Tissue factor expression, angiogenesis, and thrombosis in pancreatic cancer

Tissue factor and cancer stem cells: is there a linkage?

A common feature in the progression of multiple human malignancies is the protracted deregulation of the coagulation system, often referred to as cancer coagulopathy. Indeed, cancer cells and their vascular stroma often exhibit procoagulant properties, of which deregulation of tissue factor (TF) expression is a notable, although not the sole example. These changes can be traced to oncogenic influences affecting epidermal growth factor receptor (EGFR), EGFRvIII, K-ras, p53, PTEN, and probably many other proto-oncogenes and tumor suppressors in tumor parenchyma. Cancer stem cells (CSCs)/tumor initiating cells (TICs) are thought to represent the primary target and the main cellular effector through which oncogenic mutations exert their tumor-inducing effects. In so doing, CSCs/TICs depend on interactions with the tumor vasculature, which forms supportive niches for their clonal growth. We postulate that TF contributes to these interactions (directly or indirectly) through procoagulant and signaling effects, the latter executed in concert with juxtaposed protease activated receptors (mainly PAR-1 and PAR-2). TF/PAR system acts as a "blood sensing" mechanism, whereby cancer cells, including CSCs/TICs, may respond to plasma proteases (Factors VIIa, Xa, and IIa) and their related microenvironmental changes (fibrin deposition, activation of platelets). A growing body of still largely circumstantial evidence suggests that these events may contribute to the CSC/TIC niche, which could influence tumor initiation, metastasis, recurrence, and therapeutic intractability. Indeed, certain types of cancer cells harboring markers of CSCs (CD133) exhibit elevated TF expression and depend on this receptor to efficiently initiate tumor growth. We propose that both tumor cell-associated and host-related TF could influence the properties of CSCs, and that agents targeting the TF/PAR system may represent a hitherto unappreciated therapeutic opportunity to control cancer progression by influencing the CSC/TIC compartment.

Tissue factor in tumour progression

The linkage between activation of the coagulation system and cancer is well established, as is deregulation of tissue factor (TF) by cancer cells, their vascular stroma and cancer-associated inflammatory cells. TF is no longer perceived as an 'alternative' coagulation factor, but rather as a central trigger of the coagulation cascade and an important cell-associated signalling receptor activated by factor VIIa, and interacting with several other regulatory entities, most notably protease-activated receptors (PAR-1 and PAR-2). Preclinical studies revealed the role of oncogenic transformation and tumour micro-environment as TF regulators in cancer, along with the impact of this receptor on gene expression, tumour growth, metastasis, angiogenesis and, possibly, formation of the cancer stem cell niche. Increasing interest surrounds the shedding of TF-containing microvesicles from cancer cells, their entry into the circulation and their role in the intercellular transfer of TF activity, cancer coagulopathy and other processes. Recent data also suggest differential roles of cell autonomous versus global effects of TF in various settings. Questions are raised regarding the consequences of TF expression by tumour cells themselves and by their associated host stroma. Progress in these areas may soon begin to impact on clinical practice and, as such, raises several important questions. Can TF be exploited as a therapeutic target in cancer? Where and when may this be safe and beneficial? Is expression of TF in various disease settings useful as a biomarker of cancer progression or the associated hypercoagulability? What clinical questions related to TF are especially worthy of further exploration, at present and in the near future? Some of these developments and questions will be discussed in this chapter.

Cancer-associated thrombosis: risk factors, candidate biomarkers and a risk model

Cancer and its treatments are well-recognized risk factors for venous thrombo-embolism (VTE). Although solid tumors have historically been associated with VTE, more recent data suggest similar risk in patients with hematologic malignancies as well. The risk of VTE is not equal for all cancer patients or even in the same patient over time. In addition to well-known risk factors such as tumor site, stage, chemotherapy and comorbidities, candidate biomarkers have recently been identified including platelet and leukocyte counts, tissue factor and P-selectin. A validated risk model incorporating some of these risk factors and biomarkers has been shown to be predictive of VTE in cancer. VTE is associated with mortality, morbidity, potential delay in treatments for cancer and consumption of scarce health-care resources. Hence, reducing VTE with targeted prophylaxis could improve outcomes for cancer patients.

Clinical outcomes and factors predicting development of venous thromboembolic complications in patients with advanced refractory cancer in a Phase I Clinic: the M. D. Anderson Cancer Center experience

Venous thromboembolism (VTE) is common in patients with advanced cancer and may influence patient eligibility for clinical studies, quality of life, and survival. We reviewed the medical records of 220 consecutive patients seen in the Phase I Clinical Trials Program at M. D. Anderson Cancer Center to determine the frequency of VTE, associated characteristics, and clinical outcomes. Twenty-three (10.5%) patients presenting to the Phase I Clinic had a history of VTE; 26 (11.8%) patients subsequently developed VTE, with a median follow-up of 8.4 months. These included nine (39%) patients with and 17 (8.6%) without a history of VTE (P < 0.0001). The most common events were deep venous thromboses of the extremities and pulmonary emboli. The median survival of patients with and without a history of VTE was 4.7 and 10.9 months, respectively (P = 0.0002). Multivariate analysis demonstrated that a history of VTE (P < 0.0001), pancreatic cancer (P = 0.007), and platelet count >440 x 10(9)/L (P = 0.026) predicted new VTE episodes. In conclusion, this retrospective analysis demonstrated that a history or new development of VTE was noted in 40 (18%) of 220 patients seen in our Phase I Clinic. A prognostic score that can be used to predict time to development of and frequency of VTE is proposed. Am. J. Hematol. 2009. (c) 2009 Wiley-Liss, Inc.

Does clinical method mask significant VTE-related mortality and morbidity in malignant disease?

After more than 150 years of a recognised link between cancer and vascular thromboembolic events (VTE), and despite a greatly improved understanding of its pathophysiology, epidemiology and treatment, the management of patients with cancer and VTE is still limited. Limitations can be related to the thromboembolism itself, the underlying cancer, or to the management process. There is significant literature that deals with the first two, but very little regarding the systems we use, or how the inadequacies in documentation, identification and classification of VTE affect the cancer patients themselves. This review aims to raise awareness of this neglected area and stimulate research that may lead to improvements in patient care.

Cancer and thrombosis in women - molecular mechanisms

Both women and men with cancer are at increased risk for developing venous thromboembolism (VTE), a propensity that has been known for many years. Until recently it was assumed, however, that the association between cancer and thrombosis is an epiphenomenon - not causally related to the transforming malignant events. The pathophysiology of thrombosis in patients with cancer is complex involving multiple tumor-related and host-related factors. Several recent studies have provided strong evidence that activation of blood coagulation, perhaps most often mediated by tissue factor (TF)-rich microparticles (MPs), is linked directly to oncogene-induced malignant transformation. In addition, the development of VTE, either before or concurrent with the diagnosis of cancer, appears to predict an aggressive behavior of a tumor, and correlates with increased tumor angiogenesis and early onset of distant metastasis. The regulation of expression of TF in tumor cells is controlled at the molecular level by several oncogenes, as appears to be true for cyclooxygenase-2 (COX-2), an important regulator of platelet function and plasminogen activator inhibitor type 1 (PAI-1), an inhibitor of fibrinolysis. In addition, engagement of protease-activated receptors (PARs) by the TF-factor VIIa complex, factor Xa and/or thrombin, have now been shown to be important for tumor growth, angiogenesis and metastasis. Targeting blood clotting reactions in cancer, therefore, may provide a unique approach to cancer treatment.

rNAPc2 inhibits colorectal cancer in mice through tissue factor

PURPOSE

Recombinant nematode anticoagulant protein c2 (rNAPc2) is a specific inhibitor of tissue factor (TF)/factor VIIa complex with novel antithrombotic activity. TF is highly expressed in human colorectal tumors, and levels are positively correlated with disease progression.

EXPERIMENTAL DESIGN

To explore the therapeutic potential and mechanism of action of rNAPc2 during tumor growth and metastasis, we tested rNAPc2 in several experimental colorectal cancer models in mice.

RESULTS

Administration of rNAPc2 inhibited pulmonary metastasis in mice systemically disseminated with CT26 murine colon carcinoma cells in a dose-dependent fashion. Combining rNAPc2 with the cytotoxic agent 5-fluorouracil or bevacizumab (humanized anti-vascular endothelial growth factor monoclonal antibody) resulted in additive growth inhibition and simultaneous reduction of microvessel density in HCT116 human colorectal tumor xenografts in nude mice. Furthermore, rNAPc2 potentiated CPT-11 in inhibiting hepatic metastasis in nude mice with portal vein injection of HCT116 tumor cells. Long-term administration of rNAPc2 significantly suppressed spontaneous formation of intestinal tumors in Apc(Min/+) mice. Using a RNA interference approach, we showed that TF expression is necessary for rNAPc2-mediated inhibition of HCT116 human colorectal tumor xenograft growth in nude mice, indicating that the antitumor effect of rNAPc2 may be transduced through TF that is expressed on tumor cells.

CONCLUSIONS

rNAPc2 is a potent anticancer agent when used in combination with chemotherapy or antiangiogenic therapy in mouse models of colorectal cancer, and TF positivity appears to be required for its activity.

New insights into cancer-associated thrombosis

Venous thromboembolism (VTE) is an increasingly frequent complication of anticancer therapy. The underlying mechanisms are not completely understood, but are related in part to oncogene activation and tissue factor (TF) expression. Several risk factors have been identified including site and stage of cancer, patient comorbidities, and specific therapeutic agents. Candidate biomarkers such as blood counts, TF, and P-selectin have recently been identified. A risk model predictive of chemotherapy-associated VTE has been validated. Thromboprophylaxis with low molecular weight heparin (LMWH), unfractionated heparin (UFH), or fondaparinux is recommended for hospitalized medical and surgical cancer patients. Long-term anticoagulation with LMWH is safe and effective in reducing recurrent VTE in cancer. The role of thromboprophylaxis in ambulatory cancer patients receiving chemotherapy is an area of active investigation.

Hemostatic complications of angiogenesis inhibitors in cancer patients

Tumor vasculature and tumor-associated neo-angiogenesis have recently become major targets for rational drug design of antineoplastic agents. Five such agents with angiogenesis inhibiting activity (thalidomide, lenalidomide, bevacizumab, sunitinib, sorafenib) have already obtained US Food and Drug Administration approval for clinical use and many others have entered clinical trials. Vascular complications, including venous or arterial thromboembolism and hemorrhage, have emerged as relevant toxicities in several clinical trials with angiogenesis inhibitors. Given the well-known interplay between the blood clotting system, angiogenesis, and tumor growth, a better understanding of the impact of these new drugs on overall hemostatic balance is required. In this brief overview, we discuss the incidence of hemostatic complications, the likely pathogenetic mechanisms involved, and the critical need to establish in randomized clinical trials the usefulness of thrombosis prophylaxis to prevent these complications. Careful documentation of hemostatic complications during treatment with each of the new antiangiogenic drugs is warranted. Further studies are urgently required to better define the causal association of these new agents with hemostatic complications and to establish the best prophylactic strategy.

Des-gamma-carboxy prothrombin increases the expression of angiogenic factors in human hepatocellular carcinoma cells

AIMS

Des-gamma-carboxyl prothrombin (DCP) is a serum protein produced by hepatocellular carcinoma (HCC) cells. The aim of this study was to evaluate the angiogenic activity of DCP in HCC cells.

MAIN METHODS

The proliferation of HCC cells was measured by 3-[4, 5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay. The growth of HCC cells was also evaluated in vivo by using the xenografts in nude mice. The enzyme-linked immunosorbent assay (ELISA) was employed to measure the levels of angiogenic factors in supernatant of cell culture. The expression of angiogenic factors was examined by Western blot analysis and immunohistochemical staining.

KEY FINDINGS

DCP displayed the stimulation of HCC cell growth in a dose (5-80 ng/ml) and time (24-96 h) dependent manner. The increase of cell growth was also observed in nude mice bearing well-established, palpable HepG2 and SMMC-7721 xenografts after 2 weeks administration of DCP. HCC cell growth was accompanied by the elevated levels of angiogenic factors. The levels of vascular endothelial growth factor (VEGF), transforming growth factor-alpha (TGF-alpha) and basic fibroblast growth factor (bFGF) in supernatant of SMMC-7721 cells were increased from 47, 126, and 60 pg/10(6) cells/24 h to 400, 208, and 298 pg/10(6) cells/24 h, respectively, after 72 h incubation with 80 ng/ml of DCP. The results of Western blot analysis and immunohistochemical staining of HCC xenografts also showed the significant increase of VEGF, TGF-alpha, and bFGF in HCC cells.

SIGNIFICANCE

These results provide the information that DCP is a type of growth factor in progression of HCC.

Transcriptional silencing of ETS-1 efficiently suppresses angiogenesis of pancreatic cancer

In this study, we addressed the hypothesis that transcriptional suppression of erythroblastosis virus E26 oncogene homolog 1 (ETS-1) is an efficient therapeutic approach to pancreatic adenocarcinoma by investigating the effect of ETS-1 suppression in human pancreatic cancer cells. We accomplished this by using an adenoviral vector encoding only the DNA-binding domain of wild-type ETS-1 (ETS-1 dominant negative, ETS-1-DN). ETS-1-DN decreases ETS-1-binding by competing for its binding to DNA. Adenoviral-mediated transfer of ETS-1-DN (adenoviral ETS-1-DN construct, AdETS-1-DN) into pancreatic tumor cell lines did not affect their proliferation rate in vitro but did significantly inhibit their in vivo growth in nude mice. Furthermore, to test the efficacy of ETS-1-DN in vivo, we injected the AdETS-1-DN into established human pancreatic adenocarcinomas grown in nude mice. This treatment significantly reduced tumor size as compared to saline injection, without any detectable side effects. Microvessel density in mouse xenografts displayed significantly lower values in tumors in which ETS-1 was downregulated. In addition, expression of the ETS-1-DN in the pancreatic cancer cells resulted in downregulation of urokinase-type plasminogen activator (u-PA) and metalloproteinase-1 (MMP-1) expression. Taken together, these data suggest that transcriptional inactivation of ETS-1 is able to significantly affect angiogenesis and growth of pancreatic cancer. This effect may be due in part to downregulation of MMP-1 and u-PA expression. Our results suggest that ETS-1-DN is a promising candidate for antiangiogenic gene therapy in pancreatic cancer.

Preoperative platelet-lymphocyte ratio is an independent significant prognostic marker in resected pancreatic ductal adenocarcinoma

BACKGROUND

The objective of this study was to investigate whether the preoperative platelet-lymphocyte (P/L) ratio represents a significant prognostic index in resected pancreatic ductal adenocarcinoma.

METHODS

A total of 110 patients undergoing pancreatoduodenectomy for pancreatic ductal adenocarcinoma over a 10-year period were identified from a prospectively maintained database.

RESULTS

The preoperative P/L ratio was found to be a more significant prognostic marker (P < .001) than either the lymphocyte count (P = .007) or platelet count (P = .068) on univariate Cox survival analysis. The median overall survival in patients with a P/L ratio of 150 or less (n = 48) was 19.7 months, 13.7 months in those with a P/L ratio of 151 to 300 (n = 43), and 5.8 months in patients with a value of greater than 300 (n = 19) (log-rank, P = .006). The preoperative P/L ratio retained significance on multivariate analysis (P < .001), along with tumor size (P = .010) and lymph node ratio (P = .013).

CONCLUSIONS

The preoperative P/L ratio represents a significant independent prognostic index in patients of resected pancreatic adenocarcinoma.

Coagulation, anticoagulation and pancreatic carcinoma

An increase in coagulation in patients with pancreatic carcinoma has long been documented. In this Review, we present what is known about the pathophysiology of increased coagulation in cancer and how it applies to pancreatic carcinoma. The relationship between the activation of coagulation or symptomatic thromboembolic disease and the development of pancreatic carcinoma is explored. Data on the relationship between thromboembolic disease and the behavior of pancreatic cancer before, during or after a diagnosis is made are also reviewed. Finally, the rationale and evidence for the use of oral anticoagulants or heparin in patients with pancreatic carcinoma is presented. This Review is a critical appraisal of what is known, and when the evidence is acceptable, on the subject of thromboembolism, anticoagulation, and treatment with anticoagulants in patients with pancreatic carcinoma.

Tissue factor, angiogenesis and tumour progression

Tissue factor, the primary initiator of the coagulation cascade, maintains vascular integrity in response to injury. It is now recognised that, in addition to the role as a procoagulant activator, tissue factor participates in many tumour-related processes that contribute to malignant disease progression. The present review details the recent evidence supporting a role for tissue factor in tumour haemostasis, angiogenesis, metastasis and malignant cell survival. Furthermore, future research directions are discussed that may enhance our understanding of the role and regulation of this protein, which could ultimately lead to the innovative design and development of new anticancer therapies.

Approaches to risk-stratifying cancer patients for venous thromboembolism

Cancer patients are clearly at increased risk for venous thromboembolism (VTE). However, the risk is not equal for all cancer patients or even in the same patient over the course of the natural history of cancer. VTE prophylaxis has been shown to be beneficial in certain high-risk populations such as post-surgical or hospitalized cancer patients but data in the ambulatory setting are conflicting. A majority of solid tumor patients are currently treated in the ambulatory setting and studying risk factors for VTE and their interaction is essential to identifying a population of ambulatory cancer patients that could benefit from prophylaxis. In this review, we evaluate the literature on risk factors for cancer-associated VTE and discuss data from a large observational study of cancer patients receiving chemotherapy which has revealed novel risk factors for chemotherapy-associated VTE. Finally, we discuss model-based approaches to risk-stratifying cancer patients that incorporate the known multiple risk factors for VTE and can help identify high-risk subgroups in the cancer population.

Development and validation of a predictive model for chemotherapy-associated thrombosis

Risk of venous thromboembolism (VTE) is elevated in cancer, but individual risk factors cannot identify a sufficiently high-risk group of outpatients for thromboprophylaxis. We developed a simple model for predicting chemotherapy-associated VTE using baseline clinical and laboratory variables. The association of VTE with multiple variables was characterized in a derivation cohort of 2701 cancer outpatients from a prospective observational study. A risk model was derived and validated in an independent cohort of 1365 patients from the same study. Five predictive variables were identified in a multivariate model: site of cancer (2 points for very high-risk site, 1 point for high-risk site), platelet count of 350 x 10(9)/L or more, hemoglobin less than 100 g/L (10 g/dL) and/or use of erythropoiesis-stimulating agents, leukocyte count more than 11 x 10(9)/L, and body mass index of 35 kg/m(2) or more (1 point each). Rates of VTE in the derivation and validation cohorts, respectively, were 0.8% and 0.3% in low-risk (score = 0), 1.8% and 2% in intermediate-risk (score = 1-2), and 7.1% and 6.7% in high-risk (score >/= 3) category over a median of 2.5 months (C-statistic = 0.7 for both cohorts). This model can identify patients with a nearly 7% short-term risk of symptomatic VTE and may be used to select cancer outpatients for studies of thromboprophylaxis.

Incidence, risk factors and consequences of portal vein and systemic thromboses in hepatocellular carcinoma

INTRODUCTION

Hemostatic activation may be important for tumor biology. Hepatocellular carcinoma (HCC) is commonly associated with portal vein thrombosis (PVT). Little is known about factors predictive for PVT in patients with HCC or its correlation with systemic venous thromboembolism (VTE).

METHODS

We conducted a retrospective chart review of 194 consecutive patients diagnosed with HCC at the University of Rochester between 1998 and 2004 to identify the frequency and risk factors for PVT and its correlation with VTE and survival.

RESULTS

Sixty patients (31%) had PVT with a higher rate in the non-transplant group compared to transplanted patients (34% vs. 24%; p=0.15). In multivariate analysis, Child Turcotte Pugh (CTP) class, stage, major vessel involvement, serum albumin, and serum AFP were independently associated with PVT (p<0.05 for each). The presence of PVT was associated with reduced survival (median survival 2.3 months for those with PVT versus 17.6 months for those without PVT, HR 2.05, p=0.004). The incidence of systemic VTE in the total population was 6.7%, and patients with PVT had a higher rate of systemic VTE compared to patients without PVT (11.5% vs. 4.4%; p=0.04).

CONCLUSION

PVT is common in patients with HCC, indicates advanced disease, is associated with worse survival and correlates with systemic VTE, suggesting a common mechanism of hemostatic activation. Advanced stage, higher CTP class, major vessel involvement, low serum albumin, and high AFP levels are predictive of PVT in patients with HCC.