Histopathology 2010, 57, 836–850. DOI: 10.1111/j.1365-2559.2010.03713.x
De novo expression of EphA2 in osteosarcoma modulates activation of the mitogenic signalling pathway Raphaela Fritsche-Guenther,1 Aurelia Noske,1 Ute Ungethu¨m,2 Ralf-Ju¨rgen Kuban,2 Peter M. Schlag,3 Per-Ulf Tunn,3 Janine Karle,1 Veit Krenn,4 Manfred Dietel1 & Christine Sers1 1
Institute of Pathology, Charite` Universita¨tsmedizin Berlin, Berlin, Germany, 2Laboratory for Functional Genome Research, Charite` Universita¨tsmedizin Berlin, Berlin, Germany, 3Robert-Ro¨ssle-Klinikum, Charite` Universita¨tsmedizin Berlin, Berlin, Germany, and 4Center for Histology, Cytology and Molecular Diagnostic, Wissenschaftspark Trier, Trier, Germany
Date of submission 5 August 2009 Accepted for publication 25 March 2010
Fritsche-Guenther R, Noske A, Ungethu¨m U, Kuban R-J, Schlag PM, Tunn P-U, Karle J, Krenn V, Dietel M & Sers C (2010) Histopathology 57, 836–850
De novo expression of EphA2 in osteosarcoma modulates activation of the mitogenic signalling pathway Aims: In osteosarcoma patients the development of metastases, often to the lungs, is the most frequent cause of death. The aim of this study was to elucidate the molecular mechanisms governing osteosarcoma development and dissemination and, thereby, to identify possible novel drug targets for improved treatment. Methods and results: Osteosarcoma samples were characterized using genome-wide microarrays: increased expression of the EphA2 receptor and its ligand EFNA1 was detected. In addition, increased expression of EFNB1, EFNB3 and EphA3 was suggested. Immunohistochemistry revealed an absence of EphA2 in normal bone, and de novo expression in osteosarcomas. EFNA1
was expressed in normal bone, but was significantly elevated in tumours. Further in vitro investigations on the functional role of EphA2 and EFNA1 showed that EFNA1 ligand binding induced increased tyrosine phoshorylation, receptor degradation and downstream mitogen-activated protein kinase (MAPK) activation. Interference with the MAPK pathway unravelled a potential autoregulatory loop governing mainly EFNA1 expression via the same pathway. Conclusion: Upregulation and de novo expression of ephrins in osteosarcomas are involved in oncogenic signalling and thus might stimulate osteosarcoma metastasis.
Keywords: EphA2, EFNA1, MAPK, osteosarcoma Abbreviations: DAB, 3, 3¢-diaminobenzidine; Eph, ephrin receptors; EFN, ephrin ligands; FAK, focal adhesion kinase; EFNA1, Ephrin-A1; H&E, haematoxylin and eosin; HOBc, primary osteoblast cells; IRS, immunoreactivity score; LSAB-HRP, linked streptavidin-biotin horseradish peroxidise; MAPK, mitogen-activated protein kinase; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; PP, percentage of positively stained cells; SI, staining intensity; TMA, tissue microarray
Introduction Classical osteosarcoma is the most common malignant primary bone tumour in children and adolescents, with a profound risk of metastasis to the lung.1 This highly Address for correspondence: R Fritsche, Charite` Universita¨tsmedizin Berlin, Institute of Pathology, Chariteplatz 1, D-10117 Berlin, Germany. e-mail:
[email protected] 2010 Blackwell Publishing Limited.
aggressive neoplasm affects patients mainly in the second decade of life when the growth spurt is highest, with 60% of patients under the age of 25 years.2 Before the use of effective chemotherapy, the overall 2-year survival rates for patients with osteosarcomas was 15–20% following surgical resection and ⁄ or radiotherapy.3 Since then, surgery and chemotherapy have led to an improvement in long-term survival rates to 50–80%.4 Nevertheless, drug resistance and poor
Ephrin expression in osteosarcoma
clinical outcome due to early metastasis remain problematic. Recently, using microarray analysis, we detected deregulation of several ephrins and their cognate receptors in human bone tumours, such as giant cell tumours and chondrosarcomas.5 Ephrin receptors (Eph) are the largest group of receptor tyrosine kinases; however, to date most information about ephrin receptors and ephrin ligands (EFN) has been gained from melanoma and epithelial tumours.6 In mouse melanoma cells, expression of the EphA2 receptor has been shown to stimulate a distinct invasive process resulting in metastasis formation.7 In carcinomas, there is already ample information on the diverse roles of different EFN and Eph and their signalling.8 In colorectal cancer, loss of EphA1 protein has been correlated with invasion and metastasis and is therefore associated with a poor prognosis.9,10 In contrast, EphA2 has been found to be upregulated in many carcinomas and exhibits both a kinase-dependent and kinase-independent role in the metastasis of prostatic cancer.11 Research on ephrin involvement in tumour development and progression is complicated by the fact that ephrin receptors and their ligands display forward and reverse signalling, though the impact of both EphA and B family members in angiogenesis is now well documented.12 There is a continuing medical need to study the basic molecular mechanisms of osteosarcoma in order to develop bone tumour-specific therapeutic strategies. The current study aimed to identify genes expressed differentially between normal human osteoblasts and osteosarcoma tissue and to define genes that may be involved in tumour progression.
Material and methods patients and tissues Tumour samples were obtained from the Max-Delbrueck-Center, Division of Pathology, Berlin-Buch, Germany. Patient characteristics are described in Table 1. The tissue specimens were fixed in 4% neutral buffered formaldehyde; bone containing tissue was ethylenediamine tetraacetic acid decalcified and embedded in paraffin. For each case, haematoxylin and eosin stained slides were reviewed carefully and tumour diagnosis was confirmed according to World Health Organization (WHO) criteria. Written informed consent was obtained from each patient. The median age of osteosarcoma patients was 37 years (range 7– 74 years); this is unusual, as osteosarcoma typically affects adolescents, but we were not able to study younger patients because the specimen archive in the 2010 Blackwell Publishing Ltd, Histopathology, 57, 836–850.
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Table 1. Tissue from patients with osteosarcoma used for microarray and immunohistochemical analyses Number
Type
Sex
Age
Localization
OS1*
Conventional
F
15
Femur
OS2
Conventional
M
16
Tibia
OS3
Conventional
M
74
Humerus
OS4*
Metastasis
M
40
Lung
OS5
Metastasis
M
59
Lung
OS6*
Metastasis
F
21
Lung
OS7
Metastasis
F
20
Lung
OS9*
Conventional
M
23
Tibia
OS10
Metastasis
M
24
Lung
OS11
Metastasis
F
45
Lung
OS12*
Metastasis
M
67
Lung
OS14
Conventional
M
56
Scapula
OS15*
Conventional
F
74
Femur
OS16*†
Conventional
F
37
Lung
OS17
Conventional
M
54
Tibia
OS18*
Conventional
M
7
Femur
OS20
Conventional
M
33
Femur
OS21
Conventional
M
59
Femur
OS24*
Conventional
M
17
Femur
F, Female; M, Male. *Used for microarray and immunohistochemical analyses. †Not used for immunohistochemistry.
institute includes only older patients. All the osteosarcomas were primary tumours. cell culture Primary osteoblast cells (HOBc) and the osteosarcoma cell line SaOS2 were purchased from Provitro GmbH, Berlin, Germany and from the American Type Culture Collection (ATCC, Manassas, VA, USA) and cultured in osteoblast growth medium (PromoCell, Heidelberg, Germany) and McCoys5A media (GIBCO McCoy’s 5A Media, Invitrogen Ltd, Paisley, UK) supplemented with 10% fetal calf serum and 1% penicillin ⁄ streptomycin, respectively. The osteosarcoma cell lines HOS, MNNG ⁄ HOS, OST, SJSA, MG63 and ZK58 were a gift from Professor Dr G Gaedicke, Clinic for General
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Pediatrics and Experimental Oncology, Charite´ Universita¨tsmedizin Berlin, Berlin, Germany and cultured in RPMI-1640 (Biochrome, Berlin, Germany) supplemented with 10% fetal calf serum and 1% penicillin ⁄ streptomycin. All cells were incubated in a humidified atmosphere with 5% CO2 at 37C. For signalling pathway analyses 1 lg ⁄ ml EFNA1 ⁄ Fc (R&D, Minneapolis, MN, USA), 50 lm U0126 (Promega, Madison, WI, USA) or 50 lm dimethylsulphoxide (DMSO) (Sigma-Aldrich, Steinheim, Germany) were used for the time-points indicated. For proliferation assays cells were plated directly onto 96-well plates or 96-well polyhaema plates and treated with 1 lg ⁄ ml EFNA1 ⁄ Fc up to 96 h. For anchorage-independent growth, media containing EFNA1 ⁄ Fc was changed every 24 h. Proliferation of cells was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell proliferation kit (Roche Applied Science, Mannheim, Germany). For wound-healing assay, cells were grown on six-well dishes or glass slides as a confluent monolayer and wounded with a 10-ll pipette tip. Afterwards, 1 lg ⁄ ml EFNA1 ⁄ Fc in the presence of fetal calf serum was added and wound closure was observed up to 48 h. m ic ro a r ra y a na ly s i s All tissues were cryopreserved in liquid nitrogen immediately after removal and stored at )80C. RNA was isolated from frozen samples and fresh cells using Tri-Reagent (Sigma) and the Rneasy-mini-kit (Qiagen, Hilden, Germany). cRNA was synthesized from 5 lg of total RNA. Synthesis of biotin-labelled cRNA was performed using the BioArray high yield RNA transcription kit (Enzo Diagnostics, Farmingdale, NY, USA). The amplified cRNA was hybridized to HG U133A arrays (Affymetrix, Santa Clara, CA, USA). After a scan of the array surface, the computergenerated image of the array was overlaid with a virtual grid, controlled by Microarray Suite version 5.0 software (Affymetrix). The Data Mining Tool version 3.0 (Affymetrix) and GeneSpring software package 6.1 (Silicon Genetics, Redwood City, CA, USA) were used to average results from different replicates and to perform statistical analysis to compare the sample groups. Differential gene expression between osteosarcoma and non-neoplastic osteoblasts was defined according to the following criteria: (i) upregulated genes are present in both replicates of osteosarcoma metastases and differential expression between conventional versus HOBc (>1.5) and metastases versus HOBc (>1.5) is mandatory; and (ii) downregulated genes are present in both replicates of HOBc and
differential expression between conventional versus HOBc (>1.5) and metastases versus HOBc (>1.5) is mandatory. Expression levels below 1000 were defined as background. The data were submitted to the Gene Expression Omnibus (GEO) database (GEO Accession number GSE14359,
[email protected]). immunohistochemistry Immunohistochemical analyses were performed on paraffin-embedded tissues. As a non-neoplastic control, a tissue microarray (TMA) containing n = 4 fetal and n = 6 adult bone samples (each in duplicate; Provitro GmbH, Berlin, Germany) was used. Antigen retrieval was performed by incubation in trypsin (0.5%; Digest-All Kit, Zymed, South San Francisco, CA, USA). To block endogenous peroxidase activity, peroxidase blocking reagent (Dako, Hamburg, Germany) was used. The primary antibodies EFNA1, EFNA2, EFNB1, EFNB3 (all 1:10; Zymed) and EphA2 (1:10; Upstate, Lake Placid, NY, USA) were incubated overnight at 4C. The chromogene was 3, 3¢-diaminobenzidine (DAB; Dako) and nuclear counter staining was performed with haemalaun. All samples were scored semi-quantitatively by two different observers using a score modified according to Remmele and Stegner13. (i) A score to measure the percentage of positively stained cells (PP) was performed as follows: 0 = no staining, 1 = 1–25%, 2 = 26–50%, 3 = 51–75%, 4 = 76–100%. (ii) A staining intensity score (SI) was established to measure the intensity of positively stained cells: 0 = no expression, 1 = weak expression, 2 = moderate expression, 3 = strong expression. The combined immunoreactivity score (IRS) value was calculated through PP · SI (maximum value was 12). Statistical analyses were performed using the Mann–Whitney U-test and Bonferroni correction P-values using spss version 13.0 software. Differences were considered significant at P < 0.05. i m m un o b l ot a na ly s is Protein extracts were prepared by incubation with sodium dodecyl sulphate (SDS) cell lysis buffer (10% SDS, 1 m TrisHCl pH 7.5, EDTA 0.5 m pH8). Reagents for SDS-polyacrylamide gel electrophoresis (PAGE) and Western blotting were obtained from Bio-Rad Laboratories (Richmond, CA, USA). Electrophoresis was performed and proteins were transferred to nitrocellulose membranes (Schleicher & Schu¨ll, Dassel, Germany). Membranes were blocked and specific proteins were detected by incubation with rabbit antihuman EFNA1 (V-18, 1:200; Santa Cruz), mouse antihuman EphA2 (Clone D7, 1:500; Upstate), mouse antihuman p-Tyr 2010 Blackwell Publishing Ltd, Histopathology, 57, 836–850.
Ephrin expression in osteosarcoma
(1:1000; Santa Cruz, CA, USA), rabbit antihuman P-extracellular-regulated kinase 1 ⁄ 2 (Erk1 ⁄ 2) (p44 ⁄ 42 MAPK Thr202 ⁄ Tyr204 1:1000; Cell Signaling, Danvers, MA, USA), mouse antihuman Erk1 (1:5000; BD, San Diego, CA, USA) and mouse antihuman actin (1:5000; Millipore, Billerica, MA, USA) antibodies overnight at 4C following horseradish peroxidase (HRP)-conjugated rabbit antimouse (1:5000; Dianova, Hamburg, Germany) or goat antirabbit (1:2000; Cell Signaling) secondary antibodies. Blots were developed using the ECL system from Amersham (GE Healthcare, Uppsala, Sweden). The quantification of blots was performed using ImageJ. im m u of l uo r e sc en c e s t a i n in g Cells were grown on glass slides and fixed with acetone. Immunofluorescence staining was performed using mouse antihuman EphA2 (Clone D7, 1:10; Upstate) antibody and visualized with Alexa488 (1:300; Invitrogen Ltd, Paisley, UK). Nuclei were counterstained with 4,6-diamidino-2-phenylindole (DAPI). Images were recorded using a fluorescence microscope (Zeiss, Jena, Germany).
Results
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observation that the EFNA1 ligand was highly upregulated in the osteosarcoma samples versus non-neoplastic osteoblasts focused our further survey upon the ephrin family and their expression in osteosarcoma tumour samples (Table 3). Within the 22 283 Affymetrix probe sets are five EFNA ligand probe sets (EFNA15), six EphA receptor probe sets (EphA1-5, EphA7), three EFNB ligand probe sets (EFNB1-3) and five EphB receptor probe sets (EphB1-4, EphB6). EFNA1, EphA2 and EphA3 were found to be upregulated in osteosarcoma tissue compared to HOBc. No significant differences between conventional and metastases could be observed. EFNA4, EphA1, EphA4 and EphA5 were found to be expressed above background in only one of eight osteosarcoma samples but below background in HOBc. Expression levels for EFNA2, EFNA3, EFNA5 and EphA7 were below background. Among the B-ligands, only EFNB2 showed high expression in osteosarcomas and HOBc, whereas expression below background was observed for EFNB1, EFNB3 and EphB1. For the B-class receptors EphB2, EphB3 (six of eight osteosarcoma samples), EphB4 and EphB6 (five of eight osteosarcoma samples) an expression level above background in osteosarcomas, but no differential expression was detected. With the exception of EphB4, ephrinB receptor expression in HOBc was below background.
ex p r e ss i on o f e p h r in s i n o ste o sa r c o m a s RNA derived from eight osteosarcoma samples (n = 4 conventional, n = 4 metastases) and from the human osteoblast primary culture HOBc were analysed using Affymetrix HG U133A microarrays. A total of 1163 genes were found upregulated significantly in conventional and metastatic osteosarcomas compared to HOBc. Thirty-one genes were expressed >10-fold in osteosarcomas compared to non-neoplastic osteoblasts. Among them, EFNA1, a ligand for EphA tyrosine kinase receptors, was expressed >10-fold higher in osteosarcoma samples compared to osteoblasts (Table 2A). In addition, 2059 genes were downregulated significantly between the osteosarcomas and HOBc. Thirty-seven genes were expressed less than 10-fold in osteosarcoma samples compared to osteoblasts (Table 2B). During a recent study we discovered several ephrin genes deregulated in bone-related tumours, such as giant cell tumour of the bone.5 For example, EFNA1 and EphA3 were upregulated in recurrent compared to primary giant cell tumours, while EphA1 and EphA4 were downregulated in giant cell tumour recurrences. This prompted us to suggest that tissue-specific expression patterns of ephrins are associated with the development and progression of bone tumours. The 2010 Blackwell Publishing Ltd, Histopathology, 57, 836–850.
ephrin prote in s are e xpressed at elevate d levels in osteosarcomas To confirm the differential expression of ephrins at the protein level, osteosarcoma tissue samples (n = 10 primary tumours and n = 7 metastases) were investigated immunohistochemically using anti-EFNA1, anti-EFNA2, anti-EFNB1, anti-EFNB3 and antiEphA2-specific antibodies. For EFNA1, EFNB1 and EphA2 a tissue microarray harbouring several nonneoplastic human bone samples (n = 18) were stained in addition. The immunoreactivity scores for all antigens are shown in Table 4. EFNA1 protein levels are increased in osteosarcomas As already suggested from the microarray analysis, a significant upregulation of EFNA1 was detected in osteosarcomas compared to non-neoplastic bone (P = 0.0003). EFNA1 expression was observed in seven of eight cases of both fetal and adult osteocytes, in osteoblasts and in osteoclasts of non-neoplastic bone (Figure 1A), but no significant differences were found between fetal and normal adult bone. However, EFNA1 was detectable at higher intensities in all osteosarcoma samples, where nearly 80% of tumour cells showed
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Table 2. Genes with at least 10-fold overexpression (A) or suppression (B) in osteosarcomas compared to primary osteoblast cells (HOBc) ID
Symbol
Fc
Gene
(A) Genes with at least 10-fold overexpression in osteosarcomas compared to HOBc 207370_at
IBSP
41.7
Integrin-binding sialoprotein
201721_s_at
LAPTM5
29.8
Lysosomal multispanning membrane protein 5
218678_at
NES
28.7
Nestin
217028_at
CXCR4
25.7
Chemokine (C-X-C motif) receptor 4
201720_s_at
LAPTM5
23.4
Lysosomal multispanning membrane protein 5
204712_at
WIF1
22.2
Wnt inhibitory factor-1
203305_at
F13A1
20.6
Coagulation factor XIII, A1 polypeptide
213068_at
DPT
19.6
Dermatopontin
215049_x_at
CD163
19.0
CD163 molecule
201117_s_at
CPE
18.6
Carboxypeptidase E
204379_s_at
FGFR3
17.8
Fibroblast growth factor receptor 3
201116_s_at
CPE
17.5
Carboxypeptidase E
202878_s_at
CD93
15.9
Complement component 1, q subcomponent, receptor 1
207977_s_at
DPT
15.8
Dermatopontin
215783_s_at
ALPL
14.5
Alkaline phosphatase, liver ⁄ bone ⁄ kidney
217897_at
FXYD6
14.5
FXYD domain containing ion transport regulator 6
206488_s_at
CD36
13.7
CD36 molecule (thrombospondin receptor)
203645_s_at
CD163
13.6
CD163 molecule
221558_s_at
LEF1
13.5
Lymphoid enhancer-binding factor 1
218002_s_at
CXCL14
13.4
Chemokine (C-X-C motif) ligand 14
202023_at
EFNA1
13.0
Ephrin-A1
209087_x_at
MCAM
12.2
Melanoma cell adhesion molecule
219478_at
WFDC1
12.1
WAP four-disulphide core domain 1
266_s_at
CD24
12.0
CD24 molecule
202746_at
ITM2A
11.4
Integral membrane protein 2A
208146_s_at
CPVL
11.1
Carboxypeptidase, vitellogenic-like
219607_s_at
MS4A4A
11.0
Membrane-spanning 4-domains, subfamily A, member 4
211343_s_at
COL13A1
10.7
Collagen, type XIII, alpha 1
202747_s_at
ITM2A
10.6
Integral membrane protein 2A
214574_x_at
LST1
10.2
Leucocyte specific transcript 1
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Ephrin expression in osteosarcoma
841
Table 2. (Continued ) ID
Symbol 209301_at
CA2
Fc 10.1
Gene Carbonic anhydrase II
(B) Genes with at least 10-fold suppression in osteosarcomas compared to HOBc 209395_at
CHI3L1
123.9
Chitinase 3-like 1 (cartilage glycoprotein-39)
209396_s_at
CHI3L1
87.0
Chitinase 3-like 1 (cartilage glycoprotein-39)
205792_at
WISP2
65.4
WNT1 inducible signalling pathway protein 2
203851_at
IGFBP6
37.6
Insulin-like growth factor binding protein 6
218468_s_at
GREM1
31.8
Gremlin 1, cysteine knot superfamily, homologue (Xenopus laevis)
204948_s_at
FST
27.2
Follistatin
212143_s_at
IGFBP3
23.3
Insulin-like growth factor binding protein 3
206157_at
PTX3
22.6
Pentraxin-related gene, rapidly induced by interleukin-1 beta
201107_s_at
THBS1
21.6
Thrombospondin 1
209355_s_at
PPAP2B
20.3
Phosphatidic acid phosphatase type 2B
203963_at
CA12
20.0
Carbonic anhydrase XII
202949_s_at
FHL2
19.4
Four-and-a-half LIM domains 2
204508_s_at
CA12
18.2
Carbonic anhydrase XII
202912_at
ADM
18.0
Adrenomedullin
209687_at
CXCL12
17.6
Chemokine (C-X-C motif) ligand 12 (stromal cell-derived factor 1)
205475_at
SCRG1
16.6
Scrapie responsive protein 1
206172_at
IL13RA2
16.0
Interleukin-13 receptor, alpha 2
201108_s_at
THBS1
15.2
Thrombospondin 1
213112_s_at
SQSTM1
14.2
Sequestosome 1
203939_at
NT5E
13.4
5¢-nucleotidase, ecto (CD73)
212226_s_at
PPAP2B
12.9
Phosphatidic acid phosphatase type 2B
201109_s_at
THBS1
12.7
Thrombospondin 1
212344_at
SULF1
12.6
Sulphatase 1
214767_s_at
HSPB6
12.3
Heat shock protein, alpha-crystallin-related, B6
205397_x_at
SMAD3
12.2
SMAD family member 3
212230_at
PPAP2B
12.1
Phosphatidic acid phosphatase type 2B
202275_at
G6PD
12.0
Glucose-6-phosphate dehydrogenase
208502_s_at
PITX1
11.7
Paired-like homeodomain 1
221111_at
IL26
11.4
Interleukin-26
202434_s_at
CYP1B1
11.3
Cytochrome P450, family 1, subfamily B, polypeptide 1
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Table 2. (Continued) ID
Symbol
Fc
Gene
202436_s_at
CYP1B1
11.3
Cytochrome P450, family 1, subfamily B, polypeptide 1
212992_at
AHNAK2
11.2
AHNAK nucleoprotein 2
204037_at
LPAR1
11.0
Lysophosphatidic acid receptor 1
207345_at
FST
10.9
Follistatin
202765_s_at
FBN1
10.5
Fibrillin 1
204036_at
LPAR1
10.4
Lysophosphatidic acid receptor 1
205924_at
RAB3B
10.3
RAB3B, member RAS oncogene family
Fc, Fold change; ID, Affymetrix identity.
Table 3. Ephrin expression profile in osteosarcoma tissue samples compared with non-neoplastic osteoblast primary culture primary osteoblast cells (HOBc). Relative expression levels below 1000 were defined as background Relative expression
A-ligand
A-receptor
B-ligand
B-receptor
Significant (>1000)
EFNA1 (HOBc below 1000, 8 ⁄ 8 OS above 1000) EFNA4 (1 ⁄ 8 OS above 1000, HOBc below 1000)
EphA1 (1 ⁄ 8 OS above 1000, HOBc below 1000) EphA2 (all probes above 1000) EphA3 (HOBc and 1 ⁄ 8 OS below 1000) EphA4 (1 ⁄ 8 OS above 1000, HOBc below 1000) EphA5 (1 ⁄ 8 OS above 1000, HOBc below 1000)
EFNB2 (all probes above 1000)
EphB2 (HOBc below 1000, 8 ⁄ 8 OS above 1000) EphB3 (HOBc and 2 ⁄ 8 OS below 1000) EphB4 (all probes above 1000) EphB6 (5 ⁄ 8 OS above 1000)
Not significant (
