p53-Induced Apoptosis and Inhibitors of p53

Current Medicinal Chemistry, 2009, 16, 2627-2640

2627

p53-Induced Apoptosis and Inhibitors of p53 Surendra Kumar Nayak1, Paramjit Singh Panesar2 and Harish Kumar*,1 1

Department of Chemistry, Sant Longowal Institute Engineering & Technology (Deemed University), Longowal, Sangrur 148106, India 2 Department of Food Technology, Sant Longowal Institute Engineering & Technology, Longowal, Sangrur 148106, India

Abstract: Protein p53 is a key player in mitochondrial mediated apoptotic cell death and excess p53 activity has been implicated in many disease states such athrosclerosis, diabetes, osteoarthritis, Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, AIDS, P. falciparum and S. typhimurium infections. Thus, chemical inhibitors of p53 activation might prove effective in suppressing diseases associated with excess p53 activity. Diverse chemical compounds are being synthesized and evaluated as potent inhibitors of p53 in many cell types. In this review, we have focused on the effects of apoptosis, which is involved in p53 protein and inhibition of p53 induced apoptosis. Peculiar features of p53 protein and its roles in various diseases are summarized along with important inhibitors developed in recent years.

Keywords: Apoptosis, p53-pathway, p53- inhibitors, diseases. INTRODUCTION Apoptosis is a genetically programmed process which leads to the death of a cell with un-repairable DNA damage and has been recognized to be involved in tissue remodeling during embryogenesis [1], maintenance of organism homeostasis [2], immune system function and insect metamorphosis [3]. Anti cancer drugs have been found to act by induction of apoptosis in highly proliferative cancer cells [4, 5]. Apoptosis is characterized by blebbing of the cell surface, cell shrinkage, chromatin condensation and/or internucleosomal cleavage, and the formation of apoptotic bodies [6]. Thus, apoptosis differs from necrosis in which dying cells do not swell and lyse but exhibit above characteristic morphological changes. The apoptotic cell death can be triggered by a wide variety of stimuli and not all cells necessarily die in response to the same stimulus [7]. DNA damage by ionizing radiation or antineoplastic agents is among the most studied death stimuli is, which expresses wild-type p53 to induce apoptosis in response to these stimuli [8-10]. There are various endogenous proteins other than p53, which are involved in the induction of apoptosis in variety of cells and stimuli such as caspases, granzyme-A/B and Gq [11-13]. These proteins induce apoptotic cell death through the activation of various intracellular substances such as Bax, Bak, Bik, Bim, Bad, Noxa, Puma, Smac, Htra2, and apaf-1, which are collectively known as proapoptotic proteins [11]. Similarly, there are other intracellular proteins, which act as endogenous suppressors of apoptosis and known as survival factors, for example Bcl-2, BclXL, IAPs (such as XIAP, cIAP1, c-IAP2, NIAP etc.) and c-FLIP [14, 15]. The p53 is a protein which acts as labile transcription factor that regulates the expression of a wide variety of genes involved in cell cycle arrest, apoptosis, DNA repair and differentiation in response to genotoxic or cellular stress, through a mechanism involving disruption of its interaction

*Address correspondence to this author at the Department of Chemistry, Sant Longowal Institute Engineering & Technology (Deemed University), Longowal, Sangrur-148106 (Punjab), India; Tel: +91-1672-305204 (O), +91-1672-305205 (R); Fax: +91-1672-280072; E-mail: [email protected], [email protected] 0929-8673/09 $55.00+.00

with Mdm2 (a negative regulatory partner) [16]. Induction of p53 by DNA damage involves a series of phosphorylation and acetylation modifications, some of which regulate Mdm2 binding [17, 18]. Under normal circumstances, the level of p53 is relatively low in the cell. However, if there is damage to the cell’s DNA, this activates the transcriptional activity of p53. The process of activation requires changes in the conformation of the molecule and accumulation of p53. Therefore, both qualitative and quantitative processes result in p53 activation. This may happen due to a variety of processes e.g. microtubules and growth factor depletion, ribonucleotide depletion (non-genotoxic processes), DNA damage due to radiation or UV- and X-ray exposures and oxidative stress [7]. Moreover, p53 promotes apoptosis by repressing the survival genes through the interference with the activity of specific transcription factor or by regulating mitochondrial translocation of Bax [19]. The induction of apoptosis by p53 activation results in a variety of diseases such as athrosclerosis [20], diabetes [21], osteoarthritis, neuronal disorders (such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis) [19, 22] and allograft rejection [23]. Apoptosis has also been reported in other pathological dysfunctions, for example, T-cell depletion in HIV infection and mononuclear cell loss in P. falciparum and S. typhimurium infection [15]. p53 activation not only induces apoptosis but in some cases it may also protect cells from apoptosis [24]. 1. P53 DEPENDENT APOPTOTIC PATHWAY There are two major pathways of apoptosis, namely extrinsic and intrinsic [25], which are mediated by activation of proteolytic enzymes (caspases) or death receptors and mitochondria, respectively. The intrinsic pathway is further categorized as transcription-independent and transcriptiondependent p53 pathway [26]. The transcription-independent p53 pathway involves translocation of p53 to mitochondria, which results in disruption of mitochondrial inner transmembrane potential () or permeability transition (PT) and thus increase in the mitochondrial membrane permeability and release of cytochrome c [11]. The released cytochrome c reacts with Apaf-1 to form a complex known as apoptosome © 2009 Bentham Science Publishers Ltd.

2628 Current Medicinal Chemistry, 2009 Vol. 16, No. 21

that activates downstream caspases. The transcriptiondependent pathway involves transcriptional activation of proapoptotic genes by p53 [27]. Recently, Chipuk et al. reported that Bax can also be activated transcriptionindependently by p53 [28]. Protein p53 is activated as a transcription factor in response to oncogene activation, hypoxia, nitric oxide mitotic spindle damage, riboneucleotide depletion and specially DNA damage, resulting in growth arrest or apoptosis [29-31] or by repressing the expression of antiapoptotic proteins [32], Fig. (1). Mdm2 is a ubiquitin-ligase which mediates ubiquitination of p53, thus targeting it for degradation by proteosome and p53 levels are kept low in normal cells [33]. Recently, nutlin-3, which acts as an p53 activator, has been reported for inhibition of p53/Mdm2 interaction [34]. In response to cellular stress (such as DNA damage), p53 is phosphorylated at several serine and threonine residues and acetylated at several lysine residues. Phosphorylation of p53 at amino-terminal residue may block Mdm2 binding and may promote protein stabilization and stimulate the acetyla-

Nayak et al.

tion of p53 at its carboxyl terminus. Acetylation increases p53 sequence specific DNA binding in vitro, suggesting that this modification may be required for p53-mediated transactivation [35]. Additionally, recent findings suggested that TAD consists with two nascent turn motifs, turn I (residues 40-45) and turn II (residues 49-54) are also capable of binding to Mdm2. In particular, the turn II motif has a higher Mdm2 binding affinity (20μM) [16]. In vitro and in vivo experiments revealed that gankyrin (an ankyrin repeat oncoprotein) facilitates this p53-Mdm2 binding, and increases ubiquitination and degradation of p53 [36] and NUMB, a regulator of p53, prevents ubiquitination and degradation of p53 [37]. Moreover, p53 is induced by oncogenes such as cmyc, adenovirus E1A and Ras as well as by loss of the retinoblastoma tumor suppressor pRb, thus inducing oncogene mediated cell death [38]. However, p53 can also transactivate other genes that may contribute to apoptosis including PTEN, Apaf-1, PERP, p53AIP1 and genes that lead to increase in reactive oxygen species (ROS) [39]. In many instances, an oncogenic insult only results in increased proliferation and eventually malignant transformation if activators

Fig. (1). Schematic representation of apoptotic pathway that involve activation of p53 along with role of proapoptotic and antiapoptotic factors.

p53-Induced Apoptosis and Inhibitors of p53

of p53 (such as ARF, Chk2 or ATM), or p53 itself (e.g. by Mdm2, the adenovirus E1B, papillomavirus E6 or SV40 large T antigen), or p53 downstream signaling components (p53 target genes) are inactivated [40]. p53-mediated apoptosis pathways can be suppressed by survival signals, such as growth factors binding to their cognate growth factor receptors that results in activation of the several pro-survival kinases (such as Akt, p90S6K, p70S6K and PKA) which in turn phosphorylates proapoptotic factors. This phosphorylation of proapoptotic factors inhibits their interaction with antiapoptotic Bcl-2 proteins and thus induces sequestration away from mitochondria [41]. Moreover, Akt kinase is known to mediate a number of antiapoptotic mechanisms, such as the direct phosphorylation and inactivation of Bad and caspase-9, the activation of NF-B antiapoptotic signaling via phosphorylation of IB, but also phosphorylation and activation of Mdm2 [42]. Besides phosphorylation, ubiquitination and protein-protein interactions, p53 is also regulated by acetylation that affects its activity as well as by sumoylation [43]. The chemical inhibitors of p53 may be developed as promising therapies against degenerative disorders are described below: 2. INHIBITORS OF P53 INDUCED APOPTOSIS Chemotherapy and radiation therapy for cancer often have several side effects that limit their efficacy [44]. As these effects are in part determined by p53-mediated apoptosis, hence temporary suppression of p53 has been suggested as a therapeutic strategy to prevent damage of normal tissues during treatment of tumors [16]. Moreover, premature cell death (e.g. neurodegeneration) also required temporary suppression in the activity of p53 [44]. The various inhibitors of p53 apoptotic pathway are under investigation and some of these have been proved to be effective antiapoptotic agents. These agents may act by blocking the mitochondrial localization of p53 in transcription-independent part (e.g. pifithrin-μ) or transactivatinal function of p53 in transcriptiondependent part of p53 pathway (e.g. pifithrin- and IBTs). Thus inhibitors of p53 may be the useful drugs as cotreatment for reducing the adverse effects of cancer therapy as well as premature cell death associated with p53 induction [7]. 2.1. Pifithrins (PFTs) A small molecule 2-(2-imino-4, 5, 6, 7-tetrahydrobenzothiazol-3-yl)-1-p-tolylethanone (PFT-, 1) was originally identified from a broad screening of 10,000 compounds to inhibit cell death from -irradiation [19]. This compound has been shown to protect mice from lethal genotoxic stress [45], cerebral ischemic injury [46, 47] and neuronal excitotoxic damage [48] in addition to cell death inhibition. PFT- is a cell-permeable reversible inhibitor of p53 that blocks p53-mediated apoptosis and protects normal tissues from deleterious side effects of chemotherapeutic agents. This biological effect of PFT- on p53 pathway suggested that it acts by interfering with nuclear accumulation of p53 and thus inhibition of p53-dependent transactivation of p53responsive genes. PFT- has been shown to arrest p53-

Current Medicinal Chemistry, 2009 Vol. 16, No. 21

2629

dependent growth of human diploid fibroblasts in response to DNA damage but has no effect on p53-deficient fibroblasts. It protects neurons against -amyloid peptide and glutamate-induced apoptosis [19]. Additionally, PFT- has also been found to suppress the heat shock and glucocorticoid signaling pathways, which is independent of p53 [49]. In a recent study of PFT- and its analogues, Barchechath et al. [50] reported that open PFT structure with saturated benzo ring (class I) is the best scaffold for antiapoptotic activity. While PFT- shows impressive cytoprotective activity with 72% cell survival (EC50 = 4.16 μM). Compound 9, bearing a pyrrolidinyl substituent at the para position of the phenyl ring is even more protective with 77% cell survival (EC50 = 1.31 μM). Another compound 12, bearing a tertiary amine (Et2N) substituent also enhances cell survival significantly in thymocytes treated with dexamethasone (EC50 = 1.84 μM). Moreover, compounds with o-Cl (8), p-Ph (10), and p-OMe (11) also found to be fairly active invitro. In the examination of closed-ring compounds (class II), a 2-naphthyl (15) or phenyl (16) substitution at para results in improved cytoprotective activity. Similarly, compounds with p-pyrrolidinyl (13) and p-Me (14) also prove to be fairly active (Table 1). The compounds with lipophilic substiutuents such as tertiary amines (9 and 12) or large aromatic groups (10 and 16) have shown similar and even greater cytoprotection than that of PFT- [19]. While comparing PFT- (1) with its cyclic analogue (14) or p-pyrrolidinyl substituted compound (9) with its cyclic analogue (13), it is clear that how much important imino group is for cytoprotective activity. The replacement of the imino group by oxo function in open-ring derivatives results in considerable decrease in cytoprotective activity of the compounds. This suggests that the imine function plays a vital role in the bioactivity of the open ring compounds, particularly for those of class I PFTs. Thus, it may concluded that lipophilic substituents at p-position of the phenyl ring and imino group at 2-position of the tetrahydrobenzothiazole moiety are essential features for improved cytoprotective activity of a compound. In a study, Zhu and co-workers [51] reported that oxazole analogues of PFT- also improve p53 inactivation by 2- to 4- fold in a neuroprotection assay. PFT- (1) has been described as a potent inhibitor of programmed cell death. However, 1 does not remain in the open ring form in protic solution or under physiological conditions and largely converted to a planar tricyclic derivative (PFT-, 14), with half-life of 4.2 hours. This spontaneous conversion greatly alters the structural and physicochemical properties of the drug. For example, PFT- has a pKa of 9.11 and is an ionic species in physiological medium, whereas PFT- has a pKa of 4.36 and exists as the neutral free base at pH 7. This tricyclic derivative is very hydrophobic, with a log P of 4.26. The conversion of PFT- proceeds via an intramolecular cyclization mechanism involving the imine and carbonyl groups [19, 52, 53], Fig. (2). 2.2. PFTs with Modified Iminotetrahydrobenzothiazole The similarity property principle states that structurally similar compounds are expected to have similar activities [54], small structural modifications can nevertheless produce


Table 1.

Nayak et al.

The % Survival of Thymocyte Cells Treated with PFT- and Analogues after Treatment with DEX NH O

S N

R2

R2

N R3

N

R3

I

a

R1

S

R1

II

Compound

Class

R1

R2

R3

EC50 (μ M)

Average cell survival (%)a

1

I

H

H

Me

4.16

72

2

I

H

F

H

9.69

54

3

I

H

H

N3

5.68

56

4

I

H

Cl

Cl

7.28

57

5

I

H

H

2-Naphthyl

4.02

58

6

I

H

H

H

6.06

59

7

I

H

H

Cl

5.37

59

8

I

Cl

H

H

5.72

65

9

I

H

H

Pyrrolidinyl

1.31

77

10

I

H

H

Ph

2.29

65b

11

I

H

H

OMe

7.54

66

12

I

H

H

Et2N

1.84

70

13

II

H

H

Pyrrolidinyl

> 10

50

14

II

H

H

Me

2.01

54

15

II

H

H

2-Naphthyl

4.77

57

16

II

H

H

Ph

3.79

75

Control average % cell survival: 72 ± 4. DEX average % cell survival: 36 ± 7. Toxic at 10 μM. Tested at 5 μM. b

S

S NH

N O H

N H

S

+ NH

N O_

H

CH3

N

OH

CH3 H2O CH3 S PFT-alfa (1) N

PFT-beta (14)

N

CH3

Fig. (2). Mechanism of conversion of PFT- (11 ) into PFT- (11 4) under physiological conditions.

either a slight modulation or a dramatic loss of activity. Therefore, considering the PFT- scaffold as a privileged structure according to Evans’ definition [55], Pietrancosta et al. [19] introduced chemical modification to generate a series of novel PFTs and assayed for p53 induced apoptosis in cortical neurons (Table 2). As can be seen in Table 2, tricyclic analogue 23 (ED50 = 30 nM) is one order magnitude more active than PFT- in

protecting cortical neurons exposed to etoposide. In contrast, the replacement of the cyclohexen ring by larger cycles (e.g. cycloheptene or octahydro-naphthalene: 21 and 18, respectively) abolishes inhibitory effects, showing that ring size is determinative of activity. Moreover, the introduction of different substituents on the aromatic ring (18 and 19) modulates their inhibitory activities. Interestingly, 17, the corresponding open form of the cyclic analogue 23, shows a p53 inhibitory activity similar to that of the PFT-, whereas


Table 2.


2631

The % Survival of Cortical Neurons Treated with Modified PFTs after Treatment with Etoposide S (CH2)m N

( )n

S

S NH O

(CH2)m N

( )n

I

N

(CH2)m ( )n

II

N

NH N-OH

III R3

R3

a

R3

Compounda

Class

n

m

R3

Average cell survival (%)b

1 (PFT-)

I

1

0

Me

85

17

I

1

0

NO2

84

18

I

1

4

Me

70

19

I

1

4

OMe

68

20

I

1

4

NO2

70

21

I

2

0

Me

40

22

II

1

4

NO2

71

23

II

1

0

NO2

85

24

III

1

0

NO2

35

None of the new compounds were toxic at concentration of 10 μM. Cell survival assay was performed at concentration of 3 μM. b

oxime 24 was found inactive in preventing p53-induced cell death. This later observation is of interest because oxime 24 cannot be cyclized. From this study it is clear that 23 is the most efficient inhibitor of p53-triggered neuronal death in vitro. But compound 23 and PFT- do not prevent cortical neuronal death induced by p40met, showing the remarkable specificity in the inhibitory action of 23 on p53. Thus these agents may not be effective in p53 independent cell death. Moreover, Compound 23, and 17 prevent p53-triggered increase in protein levels of p21WAF1, indicating that these analogues behave as p53 posttranscriptional activity inhibitors [45]. 2.3. Imidazobenzothiazoles (IBTs) Imidazobenzothiazoles (IBTs) are structurally related analogues of PFT-, which have been shown to act similar to PFT- and inhibit dexamethasone-induced apoptosis in thymocytes. IBTs are divided into two classes, one with open-ring system (class I) while the other with closed-ring system (class II) (Table 3). Both these classes also has the PFT platform but contained aromatic benzo ring in lead nucleus and may used to compare the influence of open versus closed-ring structure and also saturated benzo ring versus an aromatic ring (Table 1 and 3). In the open-ring IBTs series, the compounds contained 2-naphthyl (28), pyrrolidinyl (29) and phenyl (30) substituents at para position of phenyl ring shows considerable enhanced cytoprotective activity than other members of this class (class I, Table 3). But none of the compounds in this class are as protective as PFT- (1). Compounds in the closed-ring IBTs series show great survival of thymocytes treated with DEX, even more active than PFT- (1). Here again, the pyrrolidinyl (42, EC50 = 0.35 μM), 2-naphthyl (41, EC50 = 4.02 μ M) and methyl (40,

EC50 = 1.22 μM) substituents are among the most active. Compound 39 (EC50 = 10.23 μM) without a substituent on the phenyl, as well as compound 38 (EC50 = 4.44 μM) with a methoxy group on benzo ring, also shows enhanced cytoprotective activity (class II, Table 3). Thus, the same substituents seem to improve activity in several classes of PFTs and IBTs. Several compounds have greater cyto-protective activity compared with PFT- (1), particularly a few members of class I PFTs and class II IBTs. The three most potent new compounds are 9, 40 and 42, which has antiapoptotic activity in the thymocyte protection assay even at low micromolar or sub-micromolar concentrations while displacing direct cytotoxic activity at 20-fold higher concentrations [50]. Pietrancosta et al. [56] showed that cyclic analogue of compound 26 with a cyano group adjacent to the ketone as well as compound with nitro function at para position of phenyl ring in class II IBTs enhance the potency 10-fold greater than PFT- in protecting mouse embryo cortical neurons against DNA damage. 2.4. Phenylacetylenylsulfonamide (Pifithrin-μ) As described above, p53 may induce apoptosis in a transcription-independent manner, which involved translocation of p53 to mitochondria. This translocation results in disruption of , opening of mitochondrial pores, leakage of cytochrome c and induction of downstream caspases which induce cell death [11]. Further, it has been demonstrated that this mechanism is the primary cause of radiation-induced death of thymocytes and presumably other cells from most radio-sensitive tissues [57]. These findings indicate that such cells cannot be protected from apoptosis through the inhibi-


Table 3.

Nayak et al.

The % Survival of Thymocyte Cells Treated with Open- and Close-Ring IBTs after Treatment with DEX NH O

S

R1

R1

S

R2

R2

N

N R4

R3

N

R4

R3

I

a

II

Compound

Class

R1

R2

R3

R4

Average cell survival (%)a

25

I

H

H

H

H

20

26

I

H

H

Me

H

21

27

I

H

H

cyclopentyl

H

33

28

I

H

H

2-naphthyl

H

62

29

I

H

H

pyrrolidinyl

H

64

30

I

H

H

Ph

H

66

31

II

H

H

furanyl

H

16

32

II

H

H

Me

OH

19b

33

II

H

H

Br

H

22

34

II

H

H

Me

NH2

27

35

II

H

H

cyclopentyl

H

36

36

II

H

H

Me

Br

39

37

II

H

H

Ph

H

59

38

II

H

H

Me

OMe

68b

39

II

H

H

H

H

73

40

II

H

H

Me

H

73b

41

II

H

H

2-naphthyl

H

75b

42

II

H

H

pyrrolidinyl

H

78b

Control average % cell survival: 72 ± 4. Dexamethasone average % cell survival: 36 ± 7. b Toxic at 10 μM. Tested at 5 μM.

tion of the transactivation function of p53. The majority of tissue protective functions of p53 (growth arrest at cell cycle check points, induction of DNA repair enzymes etc.) also gets exerted through its transactivation function [58]. Strom et al. isolated a small molecule named pifithrin-μ (PFT-μ, 43) that blocks p53 interaction with Bcl-XL as well as Bcl-2 and selectively inhibits translocation of p53 to mitochondria without affecting the transactivation function of p53, [59], Fig. (3) and (4).

PFT-μ is a cell-permeable sulfonamide that has a high degree of p53 specificity and does not protect cells from downstream proapoptotic factors or cell death which is independent of p53. PFT-μ rescues primary mouse thymocytes from p53-mediated apoptosis caused by radiation and protects mice from doses of radiation causing lethal hematopoietic syndrome. Because PFT-μ targets only the mitochondrial branch of the p53 pathway without affecting the important transcripO

S

O NH2

(43) N NH S

N H O (44)

Fig. (3). Structures of miscellaneous inhibitor of p53.

OCH3

H2N

H N

O (45)

HO S

P

OH O



2633

Fig. (4). Existence of double role of p53 as protective and destructive protein. Selective inhibition of mitochondrial localization of p53 by PFT-μ results in protection from lethal adverse effects of radiation without affecting transactivation-mediated functions of p53 [60].

tional functions of p53, so it is found to be superior to PFT- (1) in in vivo studies [60, 61], Fig. (4). 2.5. Nocodazole Nocodazole (44), is a microtubule-interfering agent, which evokes the activation of stress response pathways, cell cycle arrest, and the induction of apoptosis [62]. Structurally, nocodazole is 2-aminobenzimidazole derivative in which benzo ring and amino group at 2-position substituted with thiophene carbonyl and methoxy carbonyl functions, respectively Fig. (3). Thus, substituent at amino function results in absence of intermolecular cyclization that is most common in PFTs under physiological conditions. As described above, phosphorylation, acetylating and ubiquitination regulate the activity of p53. Thus, these biochemical modifications prevent p53 induced apoptosis in variety of cells. Nocodazole is known to induces phosphorylation of p53 at Ser-392, one of its key activating sites, is mediated through direct p38 MAP kinase and stimulation of casein kinase 2 (CK2) in the HeLa cervical and HCT116 colon carcinoma cell lines [63]. This cytoprotective activity of nocodazole, adds another possible platform of structural modification in lead nucleus of p53 inhibitors (especially PFTS and IBTs). 2.6. Amifostine Amifostine (45) is known as 2-(3-aminopropylamino)ethylsulfanyl phosphoric acid and is being used as cytoprotective against toxic effects induced by radiotherapy and different antineoplastic agents involving DNA-binding chemotherapeutic agents, Fig. (3). It is structurally different from PFTs and IBTs, indicating that different molecules may have similar activities and this provides broad area for design and development of novel lead nucleus for p53 inhibition.

Amifostine is considered to be pro-drug because it is dephosphorylated by membrane-bound alkaline phosphatase to a pharmacologically active free thiol metabolite at the tissue site [64]. This thiol metabolite is responsible for most of the cytoprotective and radioprotective properties of the drug. Recently, Acosta et al. [65] reported that amifostine reduces p53-mediated transactivation target promoters in human myeloid leukemia K562 and NB4 cells. In these cells several p53 target genes such as p21 Waf1, mdm2, gadd45, pig8 and pig3 are down-regulated and c-myc is up-regulate by amifostine. This up-regulation of c-myc by amifostine is also consistent with impairment of p53-mediated apoptosis in K562 and NB4 cells. The ability of amifostine to protect normal tissues may also be partly attributed to the higher capillary alkaline phosphatase activity, higher pH and better vascularity of normal tissues relative to tumor that results in a more rapid generation of the active thiol metabolite as well as a higher rate constant for uptake into cells. Thus, selectively protects normal tissues from toxic effect of chemotherapeutic agents and radiotherapy without affecting their anti-tumor effect, because amifostine and metabolites are present in healthy cells at 100-fold greater concentrations than in tumor cells [66]. The cytoprotective effect of amifostine extends to nephrotoxicity, neurotoxicity, and mucositis, and has been used in clinical trials in ovary, cervix, lung, and head and neck cancer [67]. Amifostine has been approved by US-FDA for reduction of renal cisplatin toxicity in ovarian or non-small cell lung carcinoma and reduction of radiation effects on the parotid gland [68]. It has been reported for beneficial effect on acute myeloid leukemia (AML) patients [69] and a correlation with reduction of telomerase activity in AML cells in vivo [70]. Also, it has been shown that amifostine reduces toxicity of chemotherapy on hematopoietic progenitor cells and shortens the engraftment period after autologous bone marrow transplantation [71, 72]. In vitro, amifostine promotes cell survival, delays apoptosis, and stimulates the growth of colony-forming units


from bone marrow cells [73, 74]. Thus, amifostine has been used in patients with myelodysplastic syndrome, where it stimulates hematopoiesis, inducing a partial hematopoietic recovery [73, 75]. US-FDA studies of amifostine in animals have revealed its adverse effects on the fetus and breast feeding is not recommended during treatment due to the potential secretion of the drug into breast milk [76]. 3. DISEASES ASSOCIATED WITH EXCESS P53 ACTIVITY Apoptosis has been regarded as an evolutionarily conserved pathway needed for embryonic development and tissue homoeostasis [77, 78]. This type of cell death as well as proliferation is regulated by expression of p53 levels within the cell. In mammalian cells, p53 is activated through an interaction with p44 [79] or M protein [80] and involve in a variety of diseases such as neurodegenerative diseases [81], immunodeficiency [82] and skin disorders [83]. Thus, excess of p53 activity adversely affect health, especially the incidental apoptotic death in normal tissues. On other hand, suppression of normal activity of p53 results in development of cancer and autoimmune disorders. Here we describe some diseases which are result of excess activity of p53 in normal tissues or unwanted apoptosis. In these circumstances, temporary, reversible and tissue specific inhibition of p53 may be meaningful (e.g. with pifithrin-) [7, 51]. 3.1. Neurodegenerative Diseases Multiple neurodegenerative disorders such as Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), and retinitis pigmentosa (RP) results from inappropriate death of cells in the nervous system. Pathological neuronal death can occur by apoptosis, by necrosis or by a combination of both [84, 85]. The transcription factor p53 plays an essential role in the death of many cell types by inducing death-promoting protein Bax. Evidently, wild-type p53 has been implicated in the death of neurons observed in AD [86], PD [87], stroke [88], and traumatic brain injury [89]. Strong correlations between p53 expression and neuronal death induced by DNA damaging agents and glutamate also have been reported [90-92], whereas studies using p53-deficient mice suggest an essential role for p53 in neuronal deaths resulting from ischemic and excitotoxic insults. Moreover, dopaminergic neurons in mice lacking p53 were reported to be resistant to MPTP and methamphetamine induced neurotoxicities [93, 94]. Thus, the apparent involvement of p53 in the pathogenesis of neuro-diseases raises the possibility that chemical inhibitors of p53 activation might prove effective in suppressing the neurodegenerative process. It recently was reported that the compound PFT- and structurally related analog can selectively inhibit p53 transcriptional activity in various lines of non-neuronal as well as neuronal cells and can prevent DNA damage-induced death in these cells [19, 22]. 3.2. Haematologic Diseases Haematopoiesis is regulated by a number of trophic factors, such as stem cell factor, colony-stimulating factor, erythropoietin, thrombopoietin, cytokines etc. These factors

Nayak et al.

were demonstrated to act, in part, by promoting the survival of progenitor cells, by suppressing apoptosis during the differentiation of intrinsically committed progenitors [95, 96]. Overexpression of Bcl-2 prevents apoptosis of haematopoietic cells induced by growth factor withdrawal. Bone marrow-derived stromal cells also prevent apoptotic death of normal and malignant haematopoietic cells [97]. Hematological diseases, such as myelodysplastic syndromes, aplastic anemia, chronic neutropenia or severe -thalassaemia are associated with increased apoptotic cell death within the bone marrow [98-100]. The mechanisms by which increased apoptotic cell death is involved in the etiology of these diseases supported by the evidences as amifostine (p53 transactivation inhibitor) has shown beneficial effect in patients [72, 73, 75] and mitochondrial membrane permeability triggering agents inducing death in malignant hematopoietic cells [101]. 3.3. Infectious Diseases Apoptosis plays an important role in the pathogenesis of many infectious diseases, including those caused by viruses [102]. Viral infections increase p53 transcriptional activity, which induces the expression of genes involved in cell cycle arrest and apoptosis. Recent studies demonstrated that p53 activity is up-regulated during influenza and pneumonia, leading to apoptosis [103, 104]. Induction of apoptosis has also been reported in HIV infection where CD4+ cells die through the apoptosis (see autoimmune diseases). A role of apoptosis has also been proposed in pathogenesis of bacterial infectious diseases such as sarcoidosis and tuberculosis, in which mycobacterium tuberculosis heat shock protein (Mtbhsp) considered as causative agent, play important role in apoptosis [105]. 3.4. Skin Diseases The excessive apoptosis in dermal and epidermal layers of skin results in variety of skin complications such as psoriasis, viral skin lesions, anderogenetic alopecia etc. [106, 107]. Psoriasis is a benign skin disease characterized by hyperproliferation, abnormal differentiation of keratinocytes, by the presence of inflammatory cell infiltrate in both the dermis and the epidermis and by alterations to the capillaries [108]. Many genes, particularly oncogenes and tumor suppressor genes, could be involved in the disregulation of the cell-cycle, which is probably important in development of psoriatic lesions [109, 110]. Several studies have demonstrated role of p53 protein in psoriasis [111-114]. In the latest study, Baran et al. [115] reported expression of p53 in lesional psoriatic, non-lesional psoriatic and normal skin. Besides psoriasis p53 has also been found in viral skin lesions such as common warts, condylomata acuminata and epidermodysplasia verruciformis [102]. While androgenetic alopecia is result of unwanted apoptosis in hair follicles by androgens. However, the exact mechanism by which androgens exert their effects is unknown [107]. 3.5. Autoimmune Diseases Apoptosis has been implicated in a variety of autoimmune diseases such as AIDS, autoimmune exocrinopathy (AE) and systemic lupus erythematosus (SLE). AIDS, asso-


ciated to the infection by HIV, has been defined as an imbalance between the number of CD4+ lymphocytes and the ability of the bone marrow to generate new mature cells. The CD4+ cells of the HIV-positive patients die through apoptosis when stimulated in vitro. Enhanced apoptosis has been observed in primate models of lentiviral infections, as well as in lymphocytes and lymph nodes from AIDS patients. Also, HIV-1 Tat protein has shown to induce cell death by apoptosis in T-cell line and in mononuclear peripheral blood cells from uninfected donors. The Tat protein induces apoptosis by premature activation of cyclin-dependent kinases, an event that has been associated with apoptosis induction in several other cell systems. However, further to this, not only the infected cells but also non-infected cells undergo apoptosis [116, 117]. In case of autoimmune exocrinopathy (AE), tissue-specific apoptosis in the exocrine glands in estrogendeficient mice contributes to the development of disease but the molecular mechanism responsible for tissue-specific apoptosis remains obscure. Recent findings indicate that estrogen deficiency initiates p53-mediated apoptosis by p53 phosphorylation (Ser-9) and -fodrin cleavage in the exocrine gland cells through RbAp48 overexpression and exerts a possible gender-based risk of AE in postmenopausal women [118]. Another relationship between autoimmune diseases and apoptosis suggested in systemic lupus erythematosus (SLE), which is often regarded as the prototypic systemic autoimmune disease. This disease is characterized by an autoantibody response directed against selected intracellular antigens. The UV-induced apoptosis of the keratinocytes is associated with clustering of potentially immunogenic cellular components in apoptotic blebs, a process that might participate to the induction of auto-antibodies directed at multiple antigens [119]. 3.6. Li-Fraumeni Syndrome As a tumor suppressor p53 has two faces in response to stresses: either cell cycle arrest till DNA damage was repaired or apoptotic death if the repair was failed. Restoration of p53 in p53-negative tumors has been recognized as its major therapeutic application for diseases such as LiFraumeni cancer syndrome. Li-Fraumeni syndrome is an inherited genetic disorder characterized by familial clustering of multiple malignancies predominantly including sarcomas, breast cancers, brain tumors, and other diverse neoplasms [120-122]. In this syndrome, patients often develop multiple primary cancers typically with initial occurrence at a young age. The genetic basis of this syndrome is a germ-line mutation in the p53 gene [121, 123]. In addition to pathogenesis, defects in p53mediated apoptotic pathways contribute to the resistance of these tumors to conventional treatment. These tumors invariably become refractory to standard therapies and result in early death [121, 122]. Hence, treatment of Li-Fraumeni tumors with p53 gene transfer represents a novel, prototypical targeted cancer therapy for these neoplasms. Somatic mutations in p53 occur in the majority of sporadic, nonfamilial tumors [124]. A major paradox in the treatment of LiFraumeni syndrome tumors is that conventional cytotoxic therapies (chemotherapy and radiotherapy) that induce DNA damage also contribute to the high incidence of treatment related secondary malignancies in these patients [122,125-


2635

127]. It is likely that the p53 abnormalities in Li-Fraumeni syndrome tissues mediate defects in repair of DNA damage following conventional cancer treatments, thus promoting mutations that result in secondary tumor development [125127]. Hence, novel, nongenotoxic therapies for Li-Fraumeni syndrome tumors are clearly needed. Adenoviral p53 is a targeted molecular therapy that addresses the fundamental genetic defect of Li-Fraumeni syndrome and does not induce DNA damage in normal tissues [124, 128]. Recently, Senzer et al. [129] indicated that the p53 signaling pathway is intact in the Li-Fraumeni syndrome tumor and that p53 gene transfer resulted in the induction of cell cycle arrest and apoptosis. 3.7. Miscellaneous Diseases Although apoptotic cells are phagocytosed within a few hours by neighboring cells, yet has been demonstrated histologically and histochemically to occur in several disease. Apoptosis plays important role in pathology of polycystic kidney disease [130] and toxic-induced liver disorders [131, 132] and may be central to the pathogenesis of these diseases. On other hand, in ischaemic injury, such as myocardial infarction or stroke, induces the rapid death of cells within the central area of ischaemia by necrosis. Outside the central ischaemic zone, cells die over a more protracted time period by apoptosis. Rapid reperfusion of acutely occluded blood vessels induces an increase in free radical production and in intracellular calcium level, which both trigger apoptosis of cardiac yachts [133]. Induction of apoptosis has recently been demonstrated in the artherosclerosis where p53 has a direct role in development of disease [20, 134]. Degenerative disorders of the musculoskeletal system, including arthritis and osteoporosis, could also be the consequence of increased apoptosis of chondrocytes and osteocytes respectively. Lastly, tissue homeostatic control is altered during the course of aging and the equilibrium shifted toward cell death. The true nature of this age-related cell deletion phenomenon could be apoptosis [135], as a consequence of diminished synthesis of various growth factors, transmembrane signaling defects, inability to cope with oxidative stress, or abnormal cell cycle regulation [136]. 3.8. Advantages of p53 Inhibitors Gamma irradiation and anticancer therapy induces p53dependent apoptosis in several normal tissues where the p53 gene is highly expressed such as lymphoid tissues, hematopoietic organs, intestinal epithelia, and testis. Recently, Zuco et al. [137] reported that inhibition of p53 transcriptional function by cyclic PFT increases sensitization of human tumor cells to antimitotic agent–induced apoptosis. Thus, temporary suppression of p53 might be a workable therapeutic strategy to prevent damage of normal tissues and to improve to effective of anticancer therapy. p53 inhibitors not only eliminate the adverse effects of cancer therapy but also of other drugs. For instance, after approximately 5 years of levodopa therapy, 50% of patients develop motor fluctuations; the proportion of patients affected increases to 70% after 15 years of therapy [138]. Motor complications include “off” periods of immobility or greater severity of other parkinsonian symptoms and various


Nayak et al.

Apaf-1

= Apoptosis protease activating factor-1

ARF

= Alternative reading frame protein

ATM

= Ataxia-telangiectasia mutated

Bcl-2

= B-cell CLL (chronic lymphocytic leukemia)/ lymphoma-2

Bcl-xl

= Stands for "Basal cell lymphoma-extra large"

CD95

= Cluster of differentiation 95

CK2

= Casein kinase 2

DEX

= Dexamethasone

DNA

= Deoxyribonucleic acid

DR5

= Death receptor-5

EC50

= Effective concentration

ED50

= Effective dose

c-FLIP

= Cellular caspase-8 (FLICE)-like inhibitory protein

HIV

= Human immunodeficiency virus

IB

= Inhibitor of NFB

IAP

= Inhibitory apoptotic proteins

IBTs

= Imidazobenzothiazoles

log P

= Partition Coefficient

CONCLUSION

MAP

= Mitogen-activated protein

It may be concluded from the above discussion that protein p53 has vital roles in many disease states. The inhibitors of this protein may gain importance as the therapeutics in the treatment of several diseases like Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, retinitis pigmentosa. The higher activity and potency of inhibitors against p53 transactivation is of interest and certainly encouraging in the field of drug discovery based on p53 inhibition. The mechanism of p53 induced apoptosis as well as SAR studies of PFTs and IBTs classes of inhibitors will be of additional help for the success of such venture. Moreover, the description of excess active-p53 associated diseases and advantages of p53 inhibitors will boost the process of discovery for broad area of application. However, there are certain limitations of these agents as described in the text and thus need of further improvement in development process.

Me

= Methyl

MPTP

= Mitochondrial permeability transition pore

NF-B

= Nuclear factor B

abnormal involuntary movements due to striatal nerve terminal degeneration [139]. In such types of condition p53 inhibitors provide the option of treatment. 3.8. Limitations of P53 Inhibitors Impaired induction or inactivation of p53 by p53inhibitors may results in tumor progression [140], radio- or chemo-resistant tumorigenesis [141], defective p53dependent checkpoints and cell cycle progress [142]. Furthermore, p53 is also essential for transcriptional activation of the Mdm2 gene which in turn encodes a nuclear phosphoprotein that inhibits p53-mediated transactivation [143-145] and promotes the degradation of p53 [146, 147]. This feedback-loop mechanism may be interfered by p53 inhibitors. The high-risk human papillomaviruses (HPVs) that are implicated in the pathogenesis of cervical cancers [148], produce the E6 protein, which stimulates the inactivation and ubiquitin-dependent degradation of p53 [149, 150]. The protein p53 is also known to be inactivated by the X protein [151, 152], produced by hepatitis B virus (HBV), which is implicated in the pathogenesis of liver cancer [152]. Inhibitors of p53 may facilitate these pathological conditions and thus life threatening risk. In future prospectus, there is requirement of p53 inhibitors with high tissue specificity, so that associated risk can be decrease.

ACKNOWLEDGEMENT We are thankful to the Head of Department of Chemistry, Sant Longowal Institute of Engineering and Technology, for providing work facilities and support. ABBREVIATIONS

NUMB = Numb homolog (Drosophila), a human gene o

= Ortho

OMe

= Methoxy

p

= Para

PD

= Parkinson’s disease

PERP

= P53 apoptosis effector, a human gene

PFT

= Pifithrin

Ph

= Phenyl

PKA

= Protein kinase A

pKa

= Acid dissociation constant

PT

= Permeability transition

PTEN

= phosphatase and tensin homolog gene

ROS

= Reactive oxygen species

RP

= Retinitis pigmentosa

SLE

= Systemic lupus erythematosus

Smac

= Second mitochondria-derived caspases = Transactivation domain

AD

= Alzheimer’s disease

AE

= Autoimmune exocrinopathy

AIDS

= Acquired immunodeficiency syndrome

TAD

ALS

= Amyotrophic lateral sclerosis

TRAIL = TNF-related apoptosis-inducing ligand

AML

= Acute myeloid leukemia

US-FDA = United state food and drug administration

activator

of


UV

= Ultra-violet

XIAP

= X-linked inhibitor of apoptosis protein

= Mitochondrial transmembrane potential

Current Medicinal Chemistry, 2009 Vol. 16, No. 21 [23]

[24]

REFERENCES [25] [1] [2]

[3] [4]

[5] [6]

[7]

[8] [9]

[10]

[11]

[12]

[13] [14] [15]

[16]

[17] [18] [19]

[20] [21]

[22]

Ucker, D.S. Death by suicide: one-way to go in mammalian cellular development? New Biol., 1991, 3, 103-109. Lu, X.; Lee, M.; Tran, T.; Block, T. High level expression of apoptosis inhibitor in hepatoma cell line expressing Hepatitis B virus. Int. J. Med. Sci., 2005, 2, 30-35. Steller, H.; Grether, M.E. Programmed cell death in Drosophila. Neuron, 1994, 13, 1269-1274. Zeng, X.; Yan, T.; Schupp, J.E.; Seo, Y.; Kinsella, T.J. DNA mismatch repair initiates 6-thioguanine--induced autophagy through p53 activation in human tumor cells. Clin. Cancer Res., 2007, 13, 1315-1321. Kaelin, W.G. Jr. Choosing anticancer drug targets in the postgenomic era. J. Clin. Invest., 1999, 104, 1503-1506. Maguire, T.; Harrison, P.; Hyink, O.; Kalmakoff, J.; Ward, V.K. The inhibitors of apoptosis of Epiphyas postvittana nucleopolyhedrovirus. J. Gen. Virol., 2000, 81, 2803-2811. Talasz, H.; Helliger, W.; Sarg, B.; Debbage, P.L.; Puschendorf, B.; Lindner, H. Hyperphosphorylation of histone H2A.X and dephosphorylation of histone H1 subtypes in the course of apoptosis. Cell Death Differ., 2002, 9, 27-39. Levine, A.J. p53, the cellular gatekeeper for growth and division. Cell, 1997, 88, 323-331. Amundson, S.A.; Myers, T.G.; Fornace, A.J. Jr. Roles for p53 in growth arrest and apoptosis: putting on the brakes after genotoxic stress. Oncogene, 1998, 17, 3287-3299. Joseph, T.W.; Zaika, A.; Moll, U.M. Nuclear and cytoplasmic degradation of endogenous p53 and HDM2 occurs during downregulation of the p53 response after multiple types of DNA damage. FASEB J., 2003, 17, 1622-1630. Mihara, M.; Erster, S.; Zaika, A.; Petrenko, O.; Chittenden, T.; Pancoska, P.; Moll, U.M. p53 has a direct apoptogenic role at the mitochondria. Mol. Cell, 2003, 11, 577-590. Kaspar, A.A.; Okada, S.; Kumar, J.; Poulain, F.R.; Drouvalakis, K.A.; Kelekar, A.; Hanson, D.A.; Kluck, R.M.; Hitoshi, Y.; Johnson, D.E.; Froelich, C.J.; Thompson, C.B.; Newmeyer, D.D.; Anel, A.; Clayberger, C.; Krensky, A.M. A distinct pathway of cellmediated apoptosis initiated by granulysin. J. Immunol., 2001, 167, 350-356. Webster, K.A.; Bishopric, N.H. Apoptosis inhibitors for heart disease. Circulation, 2003, 108, 2954-2956. Soane, L.; Fiskum, G. J. Bioenerg. Biomembr., 2005, 37, 179. Eeva, J.; Ropponen, A.; Nuutinen, U.; Eeva, S.-T. Matto, M.; Eray, M.; Pelkonen, J. The CD40-induced protection against CD95mediated apoptosis is associated with a rapid upregulation of antiapoptotic c-FLIP. Mol. Immunol., 2007, 44, 1230-1237. Chi, S.W.; Lee, S.H.; Kim, D.H.; Ahn, M.J.; Kim, J.S.; Woo, J.Y.; Torizawa, T.; Kainosho, M.; Han, K.H. Structural details on mdm2-p53 interaction. J. Biol. Chem., 2005, 280, 38795-38802. Takimoto, R.; El-Deiry, W.S. DNA replication blockade impairs p53-transactivation. P. Natl. Acad. Sci. USA, 2001, 98, 781-783. Tang, Y.; Zhao, W.; Chen, Y.; Zhao, Y.; Gu, W. Acetylation is indispensable for p53 activation. Cell, 2008, 133, 612-626. Pietrancosta, N.; Moumen, A.; Dono, R.; Lingor, P.; Planchamp, V.; Lamballe, F.; Bahr, M.; Kraus, J.L.; Maina, F. Iminotetrahydro-benzothiazole derivatives as p53 inhibitors: discovery of a highly potent in vivo inhibitor and its action mechanism. J. Med. Chem., 2006, 49, 3645-3652. Mercer, J.; Mahmoudi, M.; Bennett, M. DNA damage, p53, apoptosis and vascular disease. Mutat. Res., 2007, 621, 75-86. Shimabukuro, M.; Zhou, Y.-T.; Levi, M.; Unger, R.H. Fatty acidinduced cell apoptosis: A link between obesity anddiabetes. P. Natl. Acad. Sci. USA, 1998, 95, 2498-2502. Duan, W.; Zhu, X.; Ladenheim, B.; Yu, Q.S.; Guo, Z.; Oyler, J.; Cutler, R.G.; Cadet, J.L.; Greig, N.H.; Mattson, M.P. p53 inhibitors preserve dopamine neurons and motor function in experimental parkinsonism. Ann. Neurol., 2002, 52, 597-606.

[26]

[27] [28]

[29] [30] [31] [32]

[33] [34]

[35] [36]

[37]

[38]

[39] [40]

[41]

[42] [43] [44]

[45]

[46]

2637

Emamaullee, J.A.; Shapiro, A.M. J. Interventional strategies to prevent beta-cell apoptosis in islet transplantation. Diabetes, 2006, 55, 1907-1914. Kim, Y.-M.; Choi, B.-M.; Kim, Y.-S.; Kwon, Y.-G.; Kibbe, M.R.; Billiar, T.R.; Tzeng, E. Protective effect of p53 in vascular smooth muscle cells against nitric oxide-induced apoptosis is mediated by up-regulation of heme oxygenase-2. BMB Rep., 2008, 41, 164-169. Schimmer, A.D. Inhibitor of apoptosis proteins: translating basic knowledge into clinical practice. Cancer Res., 2004, 64, 71837190. Bonni, A.; Brunet, A.; West, A.E.; Datta, S.R.; Takasu, M.A.; Greenberg, M.E. Cell survival promoted by the Ras-MAPK signaling pathway by transcription-dependent and -independent mechanisms. Science, 1999, 286, 1358-1362. Johnstone, R.W.; Lowe, S.W. Apoptosis: a link between cancer genetics and chemotherapy. Cell, 2002, 108, 153-164. Chipuk, J.E.; Kuwana, T.; Bouchier-Hayes, L.; Droin, N.M.; Newmeyer, D.D.; Schuler, M.; Green, D.R. Direct activation of Bax by p53 mediates mitochondrial membrane permeabilization and apoptosis. Science, 2004, 303, 1010-1014. Hainaut, P.; Hollstein, M. p53 and human cancer: the first ten thousand mutations. Adv. Cancer Res., 2000, 77, 81-137. Oren, M. Regulation of the p53 tumor suppressor protein. J. Biol. Chem., 1999, 274, 36031-36034. Vousden, K.H.; Lu, X. Live or let die: the cell's response to p53. Nat. Rev. Cancer, 2002, 2, 594-604. Hoffman, W.H.; Biade, S.; Zilfou, J.T.; Chen, J.; Murphy, M. Transcriptional repression of the anti-apoptotic survivin gene by wild type p53. J. Biol. Chem., 2002, 277, 3247-3257. Brooks, C.L.; Gu, W. p53 ubiquitination: Mdm2 and beyond. Mol. Cell, 2006, 21, 307-315. Shangary, S.; Wang, S. Small-molecule inhibitors of the MDM2p53 protein-protein interaction to reactivate p53 function: a novel approach for cancer therapy. Ann. Rev. Pharmacol. Toxicol., 2009, 49, 223-241. Szak, S.T.; Mays D.; Pietenpol, J.A. Kinetics of p53 binding to promoter sites in vivo. Mol. Cell. Biol., 2001, 21, 3375-3386. Higashitsuji, H.; Higashitsuji, H.; Itoh, K.; Sakurai, T.; Nagao, T.; Sumitomo, H.; Masuda, T.; Dawson, S.; Shimada, Y.; Mayer, R.J.; Fujita, J. The oncoprotein gankyrin binds to MDM2/HDM2, enhancing ubiquitylation and degradation of p53. Cancer Cell, 2005, 8, 75-87. Colaluca, I.N.; Tosoni, D.; Nuciforo, P.; Senic-Matuglia, F.; Galimberti, V.; Viale, G.; Pece, S.; Di Fiore, P.P. NUMB controls p53 tumour suppressor activity. Nature, 2008, 451, 76-80. Henriksson, M.; Selivanova, G.; Lindstrom, M.; Wiman, K.G. Inactivation of Myc-induced p53-dependent apoptosis in human tumors. Apoptosis, 2001, 6, 133-137. Haupt, S.; Berger, M.; Goldberg, Z.; Haupt, Y. Apoptosis - the p53 network. J. Cell Sci., 2003, 116, 4077-4085. Eischen, C.M.; Weber, J.D.; Roussel, M.F.; Sherr, C.J.; Cleveland, J.L. Disruption of the ARF-Mdm2-p53 tumor suppressor pathway in Myc-induced lymphomagenesis. Gene Dev., 1999, 13, 26582669. Harada, H.; Andersen, J.S.; Mann, M.; Terada, N.; Korsmeyer, S.J. p70S6 kinase signals cell survival as well as growth, inactivating the pro-apoptotic molecule BAD. P. Natl. Acad. Sci. USA, 2001, 98, 9666-9670. Mayo, L.D.; Donner, D.B. The PTEN, Mdm2, p53 tumor suppressoroncoprotein network. Trends Biochem. Sci., 2002, 27, 462-467. Appella, E. Modulation of p53 function in cellular regulation. Eur. J. Biochem., 2001, 268, 2763-2764. Herr, I.; Ucur, E.; Herzer, K.; Okouoyo, S.; Ridder, R.; Krammer, P.H.; von Knebel Doeberitz, M.; Debatin, K.M. Glucocorticoid cotreatment induces apoptosis resistance toward cancer therapy in carcinomas. Cancer Res., 2003, 63, 3112-3120. Komarov, P.G.; Komarova, E.A.; Kondratov, R.V.; ChristovTselkov, K.; Coon, J.S.; Chernov, M.V.; Gudkov, A.V. A chemical inhibitor of p53 that protects mice from the side effects of cancer therapy. Science, 1999, 285, 1733-1737. Leker, R.R.; Ahronowiz, M.; Greig, N.H.; Ovadia, H. The role of p53-induced apoptosis in cerebral ischemia: effects of the p53 inhibitor pifithrin alpha. Exp. Neurol., 2004, 187, 487-486.

2638 Current Medicinal Chemistry, 2009 Vol. 16, No. 21 [47]

[48]

[49]

[50]

[51]

[52]

[53]

[54]

[55]

[56]

[57]

[58] [59]

[60]

[61]

[62]

[63]

[64]

[65]

Endo, H.; Kamada, H.; Nito, C.; Nishi, T.; Chan, P.H. Mitochondrial translocation of p53 mediates release of cytochrome c and hippocampal CA1 neuronal death after transient global cerebral ischemia in rats. J. Neurosci., 2006, 26, 7974-7983. Culmsee, C.; Zhu, X.; Yu, Q.S.; Chan, S.L.; amandola, S.; Guo, Z.; Greig, N.H.; Mattson, M.P. A synthetic inhibitor of p53 protects neurons against death induced by ischemic and excitotoxic insults, and amyloid beta-peptide. J. Neurochem., 2001, 77, 220-228. Komarova, E.A.; Neznanov, N.; Komarov, P.G.; Chernov, M.V.; Wang, K.; Gudkov, A.V. p53 inhibitor pifithrin alpha can suppress heat shock and glucocorticoid signaling pathways. J. Biol. Chem., 2003, 278, 15465-15468. Barchechath, S.D.; Tawatao, R.I.; Corr, M.; Carson, D.A.; Cottam, H.B. Inhibitors of apoptosis in lymphocytes: synthesis and biological evaluation of compounds related to pifithrin-alpha. J. Med. Chem., 2005, 48, 6409-6422. Zhu, X.; Yu, Q.-S.; Culter, R.G.; Culmsee, C.W.; Holloway, H.W.; Lahiri, D.K.; Mattson, M.P.; Greig, N.H. Interdependence between physical parameters and selection of substituent groups for correlation studies. J. Med. Chem., 1971, 14, 680-684. Gary, R.K.; Jensen, D.A. The p53 inhibitor pifithrin-alpha forms a sparingly soluble derivative via intramolecular cyclization under physiological conditions. Mol. Pharmaceutics, 2005, 2, 462-474. Walton, M.I.; Wilson, S.C.; Hardcastle, I.R.; Mirza, A.R.; Workman, P. An evaluation of the ability of pifithrin-alpha and -beta to inhibit p53 function in two wild-type p53 human tumor cell lines. Mol. Cancer Ther., 2005, 4, 1369-1377. Johnson, M.; Lajiness, M.; Maggiora, G. Molecular similarity: a basis for designing drug screening programs. Prog. Clin. Biol. Res., 1989, 291, 167-171. Evans, B.E.; Rittle, K.E.; Bock, M.G.; DiPardo, R.M.; Freidinger, R.M.; Whitter, W.L.; Lundell, G.F.; Veber, D.F.; Anderson, P.S.; Chang, R.S.L.; Lotti, V.J.; Cerino, D.J.; Chen, T.B.;Kling, P.J.;Kunkel, K.A.; Springer, J.P.; Hirshfield, J. Methods for drug discovery: development of potent, selective, orally effective cholecystokinin antagonists. J. Med. Chem., 1988, 31, 2235-2246. Pietrancosta, N.; Maina, F.; Dono, R.; Moumen, A.; Garino, C.; Laras, Y.; Burlet, S.; Quelever, G.; Kraus, J.L. Novel cyclized Pifithrin-alpha p53 inactivators: synthesis and biological studies. Bioorg. Med. Chem. Lett., 2005, 15, 1561-1564. Erster, S.; Mihara, M.; Kim, R.H.; Petrenko, O.; Moll, U.M. In vivo mitochondrial p53 translocation triggers a rapid first wave of cell death in response to DNA damage that can precede p53 target gene activation. Mol. Cell Biol., 2004, 24, 6728-6741. Smith, M.L.; Seo, Y.R. p53 regulation of DNA excision repair pathways. Mutagenesis, 2002, 17, 149-156. Strom, E.; Sathe, S.; Kamarov, P.G.; Chernova, O.B.; Pavlovska, I.; Shyshynova, I.; Bosykh, D.A.; Burdelya, L.G.; Macklis, R.M.; Skaliter, R.; Komarowa, E.A.;Gudkov, A.V. Small-molecule inhibitor of p53 binding to mitochondria protects mice from gamma radiation. Nat. Chem. Biol., 2004, 2, 474-479. Gudkov, A.V.; Komarova, E.A. Dangerous habits of a security guard: the two faces of p53 as a drug target. Hum. Mol. Genet., 2007, 16, R67-R72. Sathe, S.E.; Komarov, P.G.; Chernova, O.B.; Pavlovska, I.; Shyshynova, I.; Bosykh, D.A.; Burdelya, L.G.; Macklis, R.M.; Skaliter, R.; Komarova, E.A.; Gudkov, A.V. Small-molecule inhibitor of p53 binding to mitochondria protects mice from gamma radiation. Nat. Chem. Biol., 2006, 2, 474-479. Zhang, H.; Shi, X.; Zhang, Q.-J.; Hampong, M.; Harry Paddon, H.; Wahyuningsih, D.; Pelech, S. Nocodazole-induced p53-dependent c-Jun N-terminal kinase activation reduces apoptosis in human colon carcinoma HCT116 cells. J. Biol. Chem., 2002, 277, 4364843658. Sayed, M.; Pelech, S.L.; Wong, C.; Marotta, A.; Salh, B. Protein kinase CK2 is involved in G2 arrest and apoptosis following spindle damage in epithelial cells. Oncogene, 2001, 20, 6994-7005. Capizzi, R.L. The preclinical basis for broad-spectrum selective cytoprotection of normal tissues from cytotoxic therapies by amifostine (Ethyol). Eur. J. Cancer, 1996, 32A, S5-S16. Acosta, J.C.; Richard, C.; Delgado, M.D.; Horita, M.; Rizzo, M.G.; Fernandez-Luna, J.L.; Leon, J. Amifostine impairs p53-mediated apoptosis of human myeloid leukemia cells. Mol. Cancer Ther., 2003, 2, 893-900.

Nayak et al. [66]

[67] [68]

[69]

[70]

[71]

[72]

[73]

[74]

[75]

[76]

[77]

[78] [79] [80]

[81]

[82]

[83]

[84]

[85] [86]

McEvoy, G.K. Editor. AHFS 2002 Drug Information. Bethesda, Maryland: American Society of Health-System Pharmacists, Inc.; 2002. Links, M.; Lewis, C. Chemoprotectants: a review of their clinical pharmacology and therapeutic efficacy. Drugs, 1999, 57, 293308. Green, D.R.; Kroemer, G. Pharmacological manipulation of cell death: clinical applications in sight? J. Clin. Invest., 2005, 115, 2610-2617. Li, B.; Yang, J.; Tao, M.; Nayini, J.; Horvath, E.; Chopra, H.; Meyer, P.; Venugopal, P.; Preisler, H.D. Poor prognosis acute myelogenous leukemia 2--biological and molecular biological characteristics and treatment outcome. Leukemia Res., 2000, 24, 777-789. Preisler, H.D.; Li, B.; Yang, B.L.; Huang, R.W.; Devemy, E.; Venugopal, P.; Tao, M.; Chopra, H.; Gregory, S.A.; Adler, S.; Sivaraman, S.; Toofanfard, P.; Jajeh, A.; Galvez, A.; Robin, E. Suppression of telomerase activity and cytokine messenger RNA levels in acute myelogenous leukemia cells in vivo in patients by amifostine and interleukin 4. Clin. Cancer Res., 2000, 6, 807-812. Cagnoni, P.J.; Jones, R.B.; Bearman, S.I.; Ross, M.; Hami, L.; Franklin, W.A.; Capizzi, R.; Schein, P.S.; Shpall, E.J. Use of amifostine in bone marrow purging. Semin. Oncol., 1996, 23, 44-48. List, A.F.; Heaton, R.; Glinsmann-Gibson, B.; Capizzi, R.L. Amifostine protects primitive hematopoietic progenitors against chemotherapy cytotoxicity. Semin. Oncol., 1996, 23, 58-63. List, A.F. Use of amifostine in hematologic malignancies, myelodysplastic syndrome, and acute leukemia. Semin. Oncol., 1999, 26, 61-67. List, A.F.; Heaton, R.; Glinsmann-Gibson, B.; Capizzi, R.L. Amifostine stimulates formation of multipotent and erythroid bone marrow progenitors. Leukemia, 1998, 12, 1596-1602. List, A.F.; Brasfield, F.; Heaton, R.; Glinsmann-Gibson, B.; Crook, L.; Taetle, R.; Capizzi, R.L. Stimulation of hematopoiesis by amifostine in patients with myelodysplastic syndrome. Blood, 1997, 90, 3364-3369. Amifostine. USP DI. Drug information for the health care professional. 20th Ed, Englewood, Colorado: Micromedex, Inc.; 2002, Vol. 1. Qin, H.; Yu, T.; Qing, T.; Liu, Y.; Zhao, Y.; Cai, J.; Li, J.; Song, Z.; Qu, X.; Zhou, P.; Wu, J.; Ding, M.; Deng, H. Regulation of apoptosis and differentiation by p53 in human embryonic stem cells. J. Biol. Chem., 2007, 282, 5842-5852. Nagata, S. Apoptosis: telling cells their time is up. Curr. Biol., 1996, 6, 1241-1243. Campisi, J. Fragile fugue: p53 in aging, cancer and IGF signaling. Nat. Med., 2004, 10, 231-232. Lynette, M.; Lu, X.; Nader, G.; Stuart, T.; Lawrence A.D. Agingassociated truncated form of p53 interacts with wild-type p53 and alters p53 stability, localization, and activity. Mech. ageing dev., 2007, 128, 717-730. Sedarous, M.; Keramaris, E.; O’Hare, M.; Melloni, E.; Slack, R.S.; Elce, J.S.; Greer, P.A.; Park, D.S. Calpains mediate p53 activation and neuronal death evoked by DNA damage. J. Biol. Chem., 2003, 278, 26031-26038. Castedo, M.; Ferri, K.F.; Blanco, J.; Roumier, T.; Larochette, N.; Barretina, J.; Amendola, A.; Nardacci, R.; Metivier, D.; Este, J.A.; Piacentini, M.; Kroemer, G. Human immunodeficiency virus 1 envelope glycoprotein complex-induced apoptosis involves mammalian target of rapamycin/FKBP12-rapamycin-associated proteinmediated p53 phosphorylation. J. Exp. Med., 2001, 194, 10971110. Cui, R.; Widlund, H.R.; Feige, E.; Lin, J.Y.; Wilensky, D.L.; Igras, V.E.; D'Orazio, J.; Fung, C.Y.; Schanbacher, C.F.; Granter, S.R.; Fisher, D.E. Central role of p53 in the suntan response and pathologic hyperpigmentation. Cell, 2007, 128, 853-864. Artal-Sanz, M.; Tavernarakis, N. Proteolytic mechanisms in necrotic cell death and neurodegeneration. FEBS Lett., 2005, 579, 3287-3296. Gibson, R.M. Does apoptosis have a role in neurodegeneration? BMJ, 2001, 322, 1539-1540. de la Monte, S.M.; Sohn, Y.K.; Wands, J.R. Correlates of p53- and Fas (CD95)-mediated apoptosis in Alzheimer's disease. J. Neurol. Sci., 1997, 152, 73-83.

p53-Induced Apoptosis and Inhibitors of p53 [87]

[88]

[89]

[90]

[91]

[92]

[93]

[94]

[95]

[96]

[97] [98]

[99]

[100]

[101]

[102]

[103]

[104]

[105]

[106]

[107] [108]

Blum, D.; Wu, Y.; Nissou, M.F. Arnaud, S.; Benabid, A.L.; Verna, J.M. p53 and Bax activation in 6-hydroxydopamineinduced apoptosis in PC12 cells. Brain Res., 1997, 751, 139. Crumrine, R.C.; Thomas, A.L.; Morgan, P.F. Attenuation of p53 expression protects against focal ischemic damage in transgenic mice. J. Cerebr. Blood Flow Metab., 1994, 14, 887-891. Napieralski, J.A.; Raghupathi, R.; McIntosh, T.K. The tumorsuppressor gene, p53, is induced in injured brain regions following experimental traumatic brain injury. Mol. Brain Res., 1999, 71, 7886. Cregan, S.P.; MacLaurin, J.G.; Craig, C.G.; Robertson, G.S.; Nicholson, D.W.; Park, D.S.; Slack, R.S. Bax-dependent caspase-3 activation is a key determinant in p53-induced apoptosis in neurons. J. Neurosci., 1999, 19, 7860-7869. Sakhi, S.; Bruce, A.; Sun, N. Tocco G, Baudry, M.; Schreiber, S.S. Induction of tumor suppressor p53 and DNA fragmentation in organotypic hippocampal cultures following excitotoxin treatment. Exp. Neurol., 1997, 145, 81-88. Morrison, R.S.; Wenzel, H.J.; Kinoshita, Y. Robbins, C.A.; Donehower, L.A.; Schwartzkroin, P.A. Loss of the p53 tumor suppressor gene protects neurons from kainate-induced cell death. J. Neurosci., 1996, 16, 1337-1345. Trimmer, P.A.; Smith, T.S.; Jung, A.B.; Bennett, J.P. Jr. Dopamine neurons from transgenic mice with a knockout of the p53 gene resist MPTP neurotoxicity. Neurodegeneration, 1996, 5, 233-239. Hirata, H.; Cadet, J.L. p53-knockout mice are protected against the long-term effects of methamphetamine on dopaminergic terminals and cell bodies. J. Neurochem., 1997, 69, 780-790. Williams G.T.; Smith, C.A.; Spooncer, E.; Dexter T.M.; Taylor, D.R. Haemopoietic colony stimulating factors promote cell survival by suppressing apoptosis. Nature, 1990, 343, 76-79. Koury, M.J.; Bondurant, M.C. Erythropoietin retards DNA breakdown and prevents programmed death in erythroid progenitor cells. Science, 1990, 248, 378-381. Manabe, A.; Coustan-Smith, E.; Behm, F.G.; Raimondi, S.C.; Campana, D. Blood, 1992, 79, 2370. Yoshida, Y. Hypothesis: apoptosis may be the mechanism responsible for the premature intramedullary cell death in the myelodysplastic syndrome. Leukemia, 1993, 7, 144-146. Clark, D.M.; Lampert, I.A. Apoptosis is a Common Histopathological Finding in Myelodysplasia: the Correlate of Ineffective Haematopoiesis. Leukemia Lymphoma, 1990, 2, 415-418. Yuan, J.; Angelucci, E.; Lucarelli, G. Aljurf, M.; Snyder, L.M.; Kiefer, C.R.; Ma, L.; Schrier, S.L.. Accelerated programmed cell death (apoptosis) in erythroid precursors of patients with severe beta-thalassemia (Cooley's anemia). Blood, 1993, 82, 374-377. Solary, E.; Bettaieb, A.; Dubrez-Daloz, L.; Corcos, L. Mitochondria as a target for inducing death of malignant hematopoietic cells. Leukemia Lymphoma, 2003, 44, 563-564. Hussein M.R.; Al-Badaiwy, Z.H.; Guirguis, M.N. Analysis of p53 and bcl-2 protein expression in the non-tumorigenic, pretumorigenic, and tumorigenic keratinocytic hyperproliferative lesions. J. Cutan. Pathol., 2004, 31, 643-651. Technau-Ihling, K., Ihling, C.; Kromeier, J.; Brandner, G. Influenza A virus infection of mice induces nuclear accumulation of the tumorsuppressor protein p53 in the lung. Arch. Virol., 2001, 146, 1655-1666. Turpin, E.; Luke, K.; Jones, J.; Tumpey, T.; Konan, K.; SchultzCherry, S. Influenza virus infection increases p53 activity: role of p53 in cell death and viral replication. J. Virol., 2005, 79, 88028811. Dubaniewicz, A.; Trzonkowski, P.; Dubaniewicz-Wybieralska, M.; Dubaniewicz, A.; Singh, M.; Mysliwski, A. Comparative analysis of mycobacterial heat shock proteins-induced apoptosis of peripheral blood mononuclear cells in sarcoidosis and tuberculosis. J. Clin. Immunol., 2006, 26, 243-250. Reefman, E.; Limberg, P.C.; Kallenberg, C.G.M.; Bijl, M. Apoptosis in human skin: role in pathogenesis of various diseases and relevance for therapy. Ann. N. Y. Acad. Sci., 2005, 1051, 52-63. Morgan, M.B.; Rose, P. An investigation of apoptosis in androgenetic alopecia. Ann. Clin. Lab. Sci., 2003, 33, 107-112. van de Kerkhof, P. Textbook of psoriasis, 2nd Ed., Blackwell Publishing Ltd., Oxford, 2003, pp. 83-109.

Current Medicinal Chemistry, 2009 Vol. 16, No. 21 [109] [110] [111]

[112]

[113]

[114]

[115] [116]

[117] [118]

[119]

[120]

[121]

[122]

[123]

[124] [125]

[126]

[127]

[128]

[129]

[130] [131]

2639

Bishop, J.M. Molecular themes in oncogenesis. Cell, 1991, 64, 235-248. Marshall, C.J. Tumor suppressor genes. Cell, 1991, 64, 313-326. Tadini, G.; Cerri, A.; Crosti, L. Cattoretti, G.; Berti, E. P53 and oncogenes expression in psoriasis. Acta Derm. Venereol. Suppl., 1989, 146, 33-35. Helander, S.D.; Peters, M.S.; Pittelkow, M.R. Expression of p53 protein in benign and malignant epidermal pathologic conditions. J. Am. Acad. Dermatol., 1993, 29, 741-748. Soini, Y.; Kamel, D.; Paakko, P.; Lehto, V.P.; Oikarinen, A.; Vahakangas, K.V. Aberrant accumulation of p53 associates with Ki67 and mitotic count in benign skin lesions. Br. J. Dermatol., 1994, 131, 514-520. Hannuksela-Svahn, A.; Paakko, P.; Autio, P.; Reunala, T.; Karvonen, J.; Vähäkangas, K. Expression of p53 protein before and after PUVA treatment in psoriasis. Acta Derm. Venereol., 1999, 79, 195-199. Baran, W.; Szepietowski, J.C.; Szybejko-Machaj, G. Expression of p53 protein in psoriasis. Acta dermatoven APA, 2005, 14, 79-83. Ameisen, J.C. From cell activation to cell depletion. The programmed cell death hypothesis of AIDS pathogenesis. Adv. Exp. Med. Biol., 1995, 374, 139-163. Chamond, R.R.; Anon, J.C.; Aguilar, C.M.; Pasadas, F.G. Apoptosis and disease. Alergol. Immunol. Clin., 1999, 14, 367-374. Ishimaru, N.; Arakaki, R.; Omotehara, F.; Yamada, K.; Mishima, K.; Saito, I.; Hayashi, Y. Novel role for RbAp48 in tissue-specific, estrogen deficiency-dependent apoptosis in the exocrine glands. Mol. Cell Biol., 2006, 26, 2924-2935. Casciola-Rosen, L.A.; Anhalt, G.; rosen, A. Autoantigens targeted in systemic lupus erythematosus are clustered in two populations of surface structures on apoptotic keratinocytes. J. Exp. Med., 1994, 179, 1317-1330. Li, F.P.; Fraumeni, J.F. Jr. Soft-tissue sarcomas, breast cancer, and other neoplasms. A familial syndrome? Ann. Intern. Med., 1969, 71, 747-752. Malkin, D.; Li, F.P.; Strong, L.C.; Fraumeni, J.F. Jr.; Nelson, C.E.; Kim DH, Kassel, J.; Gryka, M.A.; Bischoff, F.Z.; Tainsky, M.A. Germ line p53 mutations in a familial syndrome of breast cancer, sarcomas, and other neoplasms. Science, 1990, 250, 12331238. Hisada, M.; Garber, J.E.; Fung, C.Y.; Fraumeni, J.F. Jr.; Li, F.P. Multiple primary cancers in families with Li-Fraumeni syndrome. J. Natl. Cancer Inst., 1998, 90, 606-611. Varley, J.M.; McGown, G.; Thorncroft, M.; Santibanez-Koref, M.F.; Kelsey, A.M.; Tricker, K.J. Evans, D.G.; Birch, J.M. Germline mutations of TP53 in Li-Fraumeni families: an extended study of 39 families. Cancer Res., 1997, 57, 3245-3252. Roth, J.A. Adenovirus p53 gene therapy. Expert Opin. Biol. Ther., 2006, 6, 55-61. Nutting, C.; Camplejohn, R.S.; Gilchrist, R.; Tait, D.; Blake, P.; Knee, G.; Yao, W.Q.; Ross, G.; Fisher, C.; Eeles, R. A patient with 17 primary tumours and a germ line mutation in TP53: tumour induction by adjuvant therapy? Clin. Oncol. (R Coll Radiol), 2000, 12, 300-304. Limacher, J.M.; Frebourg, T.; Natarajan-Ame, S.; Bergerat, J.P. Two metachronous tumors in the radiotherapy fields of a patient with Li-Fraumeni syndrome. Int. J. Cancer, 2001, 96, 238-242. Hwang, S.J.; Lozano, G.; Amos, C.I.; Strong, L.C. Germline p53 mutations in a cohort with childhood sarcoma: sex differences in cancer risk. Am. J. Hum. Genet., 2003, 72, 975-983. Frederickson, R.M.; Carter, B.J.; Pilaro, A.M. Nonclinical toxicology in support of licensure of gene therapies. Mol. Ther., 2003, 8, 8-10. Senzer, N.; Nemunaitis, J.; Nemunaitis, M.; Lamont, J.; Gore, M.; Gabra, H.; Eeles, R.; Sodha, N.; Lynch, F.J.; Zumstein, L.A.; Menander, K.B.; Sobol, R.E.; Chada, S. p53 therapy in a patient with Li-Fraumeni syndrome. Mol. Cancer Ther., 2007, 6, 14781482. Woo, D. Apoptosis and loss of renal tissue in polycystic kidney diseases. New Engl. J. Med., 1995, 333, 18-25. Guicciardi, M.E.; Gores, G.J. Apoptosis: a mechanism of acute and chronic liver injury. Gut, 2005, 54, 1024-1033.

2640 Current Medicinal Chemistry, 2009 Vol. 16, No. 21 [132]

[133]

[134] [135]

[136] [137]

[138]

[139]

[140] [141]

[142]

[143]

Goldin, R.D.; Hunt, N.C.; Clark, J.; Wickramassinghe, S.N. Apoptotic bodies in a murine model of alcoholic liver disease: reversibility of ethanol-induced changes. J. Pathol., 1993, 171, 73-76. Gottlieb, R.A.; Burleson, K.O.; Kloner, R.A.; Babior, B.M.; Engler, R.L. Reperfusion injury induces apoptosis in rabbit cardiomyocytes. J. Clin. Invest., 1994, 94, 1621-1628. Mercer, J.; Bennett, M. The role of p53 in atherosclerosis. Cell Cycle, 2006, 5, 1907-1909. Whyte, M.K.B.; Meagher, L.C.; MacDermot, J.; Haslett, C. Impairment of function in aging neutrophils is associated with apoptosis. J. Immunol., 1993, 150, 5124-5134. Lockshin, R.A.; Zackeri, Z.F. Programmed cell death: new thoughts and relevance to aging. J. Gerontol., 1990, 45, 135-140. Zuco, V.; Zunino, F. Cyclic pifithrin- sensitizes wild type p53 tumor cells to antimicrotubule agent-induced apoptosis. Neoplasia, 2008, 10, 587-596. Miyawaki, E.; Lyons, K.; Pahwa, R. Motor complications of chronic levodopa therapy in Parkinson’s disease. Clin. Neuropharmacol., 1997, 20, 523-530. Lemke, T.L., Williams, D.A., Roche, V.F., Zito, S.W. In Foye’s principles of medicinal chemistry, Booth R.G., 6th Ed.; Wolters Kluwer India Pvt. Ltd., New Delhi, 2008, pp. 679-697. Smith, M.L.; Fornace, A.J.J. Genomic instability and the role of p53 mutations in cancer cells. Curr Opin Oncol., 1995, 7, 69-75. Lowe, S.W.; Ruley, H.E.; Jacks, T.; Housman, D.E. p53-dependent apoptosis modulates the cytotoxicity of anticancer agents. Cell, 1993, 74, 957-967. Bunz, F.; Hwang, P.M.; Torrance, C.; Waldman, T.; Zhang, Y.; Dillehay, L.; Williams, J.; Lengauer, C.; Kinzler, K.W.; Vegelstein, B. Disruption of p53 in human cancer cells alters the responses to therapeutic agents. J. Clin. Invest., 1999, 104, 263-269. Barak, Y.; Juven, T.; Haffner, R.; Oren, M. Mdm2 expression is induced by wild-type p53 activity. EMBO J., 1993, 12, 461-468.

Received: February 16, 2009

Revised: May 14, 2009

Accepted: May 16, 2009

Nayak et al. [144]

[145]

[146] [147] [148] [149]

[150]

[151]

[152]

[153]

Momand, J.; Zambetti, G.P.; Olson, D.C.; George, D.; Levine, A.J. The mdm-2 oncogene product forms a complex with the p53 protein and inhibits p53-mediated transactivation. Cell, 1992, 69, 1237-1245. Zauberman, A.; Barak, Y.; Ragimov, N.; Levy, N.; Oren, M. Sequence-specific DNA binding by p53: identification of target sites and lack of binding to p53-MDM2 complexes. EMBO J., 1993, 12, 2799-2808. Haupt, Y.; Maya, R.; Kazaz, A.; Oren, M. Mdm2 promotes the rapid degradation of p53. Nature, 1997, 387, 296-299. Kubbutat, M.H.G.; Jones, S.N.; Vousden, K.H. Regulation of p53 stability by Mdm2. Nature, 1997, 387, 299-303. zur Hausen, H. Papillomavirus infections: a major cause of human cancers. Biochim. Biophys. Acta, 1996, 1288, F55-F78. Mietz, J.A.; Unger, T.; Huibregtse, J.M.; Howley, P.M. The transcriptional transactivation function of wild-type p53 is inhibited by SV40 large T-antigen and by HPV-16 E6 oncoprotein. EMBO J., 1992, 11, 5013-5020. Scheffner, M.; Werness, B.A.; Huibregtse, J.M.; Levine, A.J.; Howley, P.M. The E6 oncoprotein encoded by human papillomavirus types 16 and 18 promotes the degradation of p53. Cell, 1990, 63, 1129-1136. Truant, R.; Antunovic, J.; Greenblatt, J.; Prives, C.; Cromlish, J.A. Direct interaction of the hepatitis B virus HBx protein with p53 leads to inhibition by HBx of p53 response element-directed transactivation. J. Virol., 1995, 69, 1851-1859. Ueda, H.; Ullrich, S.J.; Gangemi, J.D.; Kappel, C.A.; Ngo, L.; Feitelson, M.A. Functional inactivation but not structural mutation of p53 causes liver cancer. Nat. Genet., 1995, 9, 41-47. Cromlish, J.A. Hepatitis B virus-induced hepatocellular carcinoma: possible roles for HBx. Trends Microbiol., 1996, 4, 270-274.