Cancer and Metastasis Reviews 19: 93–96, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands.
Impact of oncogenes and tumor suppressor genes on deregulation of hemostasis and angiogenesis in cancer Janusz Rak1 and Giannoula Klement2 Hamilton Civic Hospital Research Centre, McMaster University, Hamilton, Ontario; 2 Sunnybrook and Womens College Health Science Centre, University of Toronto, Toronto, Canada
1
Key words: oncogenes, angiogenesis, tumor progression, coagulation, tissue factor, cancer Abstract We postulate that oncogenes and tumor suppressor genes may influence tumor angiogenesis not only directly (e.g. by upregulating vascular endothelial growth factor) but also through their impact on expression (and/or function) of tissue factor and other elements of the hemostatic system. Causes and possible consequences of the ‘paraneoplastic syndrome’ First descriptions of ‘cancer coagulopathy’ date back to the 19th century works of Trousseau (1865) and Billroth (1878). The clinical sequellae of this heterogenous disorder, also referred to as a ‘paraneoplastic syndrome’ may include migratory thrombophlebitis, disseminated intravascular coagulation (DIC), laboratory abnormalities (e.g. fibrinopeptide A elevation, changes in prothrombin time) and histopathological evidence (e.g. peritumoral deposition of cross-linked fibrin) [1]. Although the precise pathomechanism of this syndrome remains unclear, it is thought to involve one or more of the following processes: (i) increased permeability of tumor blood vessels and resulting exposure of extravascular procoagulant surfaces; (ii) activation of factor VII-dependent ‘extrinsic’ coagulation cascade via upregulation of TF expression by tumor and/or stromal cells (endothelial cells, macrophages, perivascular fibroblasts); (iii) expression of cancer procoagulant (CP) on the surface of tumor cells resulting in direct activation of factor X; (iv) systemic procoagulant effects of circulating tumor cells and macrophages; (v) activation of platelets; and/or (vi) vascular injury due to anti-cancer treatment (e.g. with taxol or cytarabine) [1–4]. Dvorak postulated that extravascular clotting is an inherent functional component of both tumor neovascularization and growth [5]. According to this concept,
release of the vascular endothelial growth factor (VEGF) within solid tumor masses could dramatically increase blood vessel permeability (VEGF is also known as vascular permeability factor – VPF), a process which would lead to plasma protein leakage into the procoagulant extravascular micromillieau. The resulting formation of a provisional fibrin matrix could facilitate new blood vessel sprouting (angiogenesis) by providing growth/survival factors, regulatory adhesive interactions and mechanical support for activated endothelial cells [1]. It is now recognized that numerous components of the coagulation system possess an apparent or cryptic angiogenesis regulatory activity (Table 1).
Do oncogenes and tumor suppressor genes have an impact on angiogenic activities ‘built into’ the hemostatic system? Genetic alterations expressed in cancer cells likely influence many of the factors involved in blood coagulation. Perhaps the most striking example in this regard is the coagulopathy associated with acute promyelocytic leukemia (APL) [11]. DIC is a common occurrence in this disease and correlates with a translocation of the promyelocytic leukemia (PML) gene on chromosome 15 into the vicinity of the retinoid acid receptor (RARα) on chromosome 17, which results in expression of a transforming fusion protein PML/RARα [11].
94 Table 1. Angiogenesis regulators within the hemostatic system Hemostatic compartment
Angiogenesis stimulators∗
Angiogenesis inhibitors∗
Platelets
VEGF-A∗∗ , VEGF-C, PDGF, bFGF, HGF, Ang-1, IGF-1, IGF-2, EGF, S-1-P Thrombin, fibrin, TF
HGF (splice forms NK1, NK2, NK4), PF4, TSP-1
Coagulation system Fibrinolysis system
uPA, FDPs
HMWK (domain 5), prothrombin fragments 1.2, aaATIII Angiostatin (plasminogen fragment), endostatin (tPA co-factor), K5 plasminogen
∗
For reference see [1, 6–10]. Abbreviations: VEGF – vascular endothelial growth factor; PDGF – platelet derived growth factor; bFGF – basic fibroblast growth factor; IGF – insuline-like growth factor; EGF – epidermal growth factor; S-1-P – sphingosine 1-phosphate; HGF – hepatocyte growth factor/scatter factor; PF4 – platelet factor 4; TSP1 – thrombospondin 1; HMWK – high molecular weight kininogen; aaATIII – anti-angiogenic antithrombin III; uPA – urokinase type plasminogen activator; FDPs – fibrin degradation products.
∗∗
The causal role of this event in the development of DIC is supported by the observation that in APL patients, therapy with all-trans retinoic acid (ATRA) leads to a correction of the abnormal subcellular localization of the PML/RARα gene product and to a brisk reversal of the coagulopathy [11]. Several hemostatic activities such as: TF-dependent activation of factor X, APLassociated cysteine proteinase, tissue plasminogen activator (tPA), single chain pro-urokinase (uPA) or elastase inactivating α2 -antiplasmin could be altered by the PML/RARα oncoprotein [11–13]. Cryptic or overt coagulopathies can be detected in many cancers, often as a function of the disease progression. For example, expression of TF is elevated in late stage tumors of the brain [14], colon [10,15] and breast [16]. This puzzling pattern raises an obvious question as to how such TF overexpression is executed at the molecular level. Although, it is clearly possible that epigenetic factors such as hypoxia, may play a significant role [17], it cannot be ruled out that TF expression could also be affected by transforming genetic events which drive both tumor progression per se [18] as well as tumor angiogenesis [19]. In fact, many of the genes responsible for cellular transformation (e.g. v-src, ras, p53) can profoundly compromise cellular responses to hypoxia [20–22] and thereby impact the expression of hypoxia-responsive molecules such as VEGF (conceivably also TF). Indeed, there is no reason to exclude molecules with ‘canonical’ hemostatic
activities (e.g. TF or uPA) from a pleiotrophic influence (direct or indirect) exerted by either activated oncogenes (e.g. ras, src, myc, HER-2, EGFR) or deficient tumor suppressor genes (e.g. p53, p16, VHL, PTEN) operating in various types of cancer cells. A generic model of such an influence is presented in Figure 1. If oncogenes and tumor suppressor genes contribute to cancer-associated coagulopathy they could do so in at least two major ways. First, direct upregulation of VEGF by mutant oncogenes [23] as well as other genetically determined changes in the ‘angiogenic balance’ [24] could translate into exuberant formation of immature, hyperpermeable tumor blood vessels, thereby creating conditions for extravascular clotting. In this case the severity of the associated coagulopathy would be reflective of the intensity of tumor angiogenesis. Second, transforming cellular events could directly alter the expression and/or function of various proteins involved in regulation of hemostasis (e.g. TF, uPA, CP and other proteases). Alternatively, deregulation of hemostatic effector molecules could be secondary to transformation-induced paracrine interactions involving tumor cells, endothelial cells, macrophages and perivascular fibroblasts. Regardless of their nature such changes could then propagate affecting both coagulation and angiogenesis. For example, TF overexpressed by tumor cells and their associated stroma [3] could interact with its blood born ligand, factor VII/VIIa and trigger the ‘extrinsic’ pathway of blood coagulation. At
95
Figure 1. Direct and indirect influence of genetic lesions in cancer cells on angiogenesis and hemostasis – a hypothesis. Reciprocal interactions are known to exist between regulation of hemostasis and angiogenesis in cancer. Similarly, to molecular mediators of tumor angiogenesis also tissue factor (TF) and various proteases of the hemostatic system can come under direct or indirect control of oncogenes and tumor suppressor genes is expressed in tumor cells.
the same time, ‘activated’ TF could induce expression of various cellular genes [25] including angiogenesis regulators such as VEGF [26]. Discoveries of tumor-derived, systemically acting angiogenesis inhibitors brought to light another aspect of the hemostasis–angiogenesis cross-talk [7,27,28]. Angiostatin and anti-angiogenic anti-thrombin III (aaATIII) pre-exist as cryptic domains within plasma proteins which are well known for their hemostatic activities (plasminogen and ATIII, respectively). The anti-angiogenic protein fragments are released by specific proteases produced within the microenvironment of certain tumors [7]. It is not known, however, what mechanism regulates the expression and activity of such proteases. In this regard, O’Reilly et al. reported an intriguing, albeit purely phenomenological, dependence of the systemic aaATIII release/activity on the genetic progression of cancer cells [28]. In this study, nude mice were inoculated into two opposite flanks with human small-cell lung cancer cell line NCI-H69i. At random, one of the resulting tumors would become larger and completely suppress the growth of the cortralateral inoculate via an aaATIII – dependent mechanism. However, when the same cells were
serially passaged in vivo the resulting variant (NCIH69ni) no longer caused systemic angiogenesis (and tumor) suppression [28]. The reasons why these more ‘malignant’ tumor cells lost their ability to induce the systemic angiogenesis inhibition are unclear, but it could be speculated that this phenotype may be linked to a ‘loss-of-function’ or a ‘gain-of-function’ genetic alterations driving tumor progression. In summary, the regulation of hemostasis and angiogenesis intersect at many critical points. It is implicit that during tumor progression many of these regulatory circuits come under direct or indirect influence of underlying genetic changes in cancer cells and become a part of the overall pathology (e.g. by driving tumor neovascularization). Perhaps, interference with cancer coagulopathy should be considered in the context of ongoing clinical trails with various inhibitors of oncogenic signal transduction (e.g. farnesyl transferase inhibitors, herceptin, EGFR inhibitors) and other new anti-cancer therapeutics (e.g. angiogenesis inhibitors). Acknowledgements We gratefully acknowledge inspiring mentorship of Dr. R.S. Kerbel who has been a great source of support and encouragement for us for so many years. We are thankful to our families who continue to survive our passion for research. We are indebted to Dr. Petr Klement for his helpful suggestions. This work was supported by funds from HCHRC to J.R and NCIC to G.K. References 1. Dvorak, FH: In: Coleman RB, Hirsh J, Marder VJ, Salzman JB (eds.) Hemostasis and Thrombosis: Basic Principles and Clinical Practice, Lippincott Company, Philadelphia, 1994, pp 1238–1254 2. Ruf W, Mueller BM: Curr Opin Hematol 3: 379–384, 1996 3. Shoji M, Hancock WW, Abe K, Micko C, Casper KA, Baine RM, Wilcox JN, Danave I, Dillehay DL, Matthews E et al. Am J Pathol 152: 399–411, 1998. 4. Rickles FR, Levine M, Edwards RL: Cancer Metast Rev 11: 237–248, 1992 5. Dvorak HF, Dvorak AM, Manseau EJ, Wiberg L, Churchill WH: J Natl Cancer Inst 62: 1459–1472, 1979 6. Folkman J: Nature Med 2: 167–168, 1996 7. Browder T, Folkman J, Pirie-Shepherd S: J Biol Chem 275: 1521–1524, 2000 8. Thompson WD, Smith EB, Stirk CM, Stout AJ, Kochhar A: Blood Coagul Fibrinolysis 1: 517–520 1990
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21. Ravi R, Mookerjee B, Bhujwalla ZM, Sutter CH, Artemov D, Zeng Q, Dillehay LE, Madan A, Semenza GL, Bedi A: Genes Dev 14: 34–44, 2000 22. Mazure NM, Chen EY, Laderoute KR, Giaccia AJ: Blood 90: 3322–3331, 1997 23. Rak J, Filmus J, Finkenzeller G, Grugel S, Marme D, Kerbel RS: Cancer Metastasis Rev 14: 263–277, 1995 24. Bouck N, Stellmach V, Hsu SC: Adv Cancer Res 69: 135–174, 1996 25. Camerer E, Gjernes E, Wiiger M, Pringle S, Prydz H: J Biol Chem 275: 6580–6585, 2000 26. Abe K, Shoji M, Chen J, Bierhaus A, Danave I, Micko C, Casper K, Dillehay DL, Nawroth PP, Rickles FR: Proc Natl Acad Sci USA 96: 8663–8668, 1999 27. O’Reilly MS, Holmgren L, Shing Y, Chen C, Rosenthal RA, Moses M, Lane SW, Cao Y, Sage EH, Folkman J: Cell 79: 315–328, 1994 28. O’Reilly MS, Pirie-Shepherd S, Lane WS, Folkman J: Science 285: 1926–1928, 1999 Address for offprints: Janusz Rak, Hamilton Civic Hospital Research Centre, McMaster University, Hamlton, Ontario L8V 1C3, Canada; Tel: 9055272299 (ext 43771); Fax: 9055752646; e-mail:
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