BACKGROUND/OBJECTIVES: Disorders of haemostasis are common in prostate cancer (PC) patients and include disseminated intravascular coagulation, venous thromboembolism, acute coronary syndrome, and others. The hyper-coagulation state in PC, which is referred to as the Trousseau's syndrome, leads to increased mortality among cancer patients, and is considered the second cause of death after cancer itself. Our research will be on the role of microvesicles (MVs), which are circular membrane compartments shed from cancer as well as from healthy cells. We hypothesize that MV's have a role in coagulopathy related to PC.
We compared the pro-coagulant activities between two PC MVs differing in their metastatic potential and aggressiveness, using chromogenic assays to determine their thrombin generation. We also compared the thrombin generation in MVs extracted from plasma of PC patients with various cancer stages and extent of metastasis. Finally, we have prepared a transfected CHO (hPAR1) cell line with a construct of the human protease-activated receptor 1 (hPAR1), the principal receptor for the serine protease thrombin. The activation of PAR1 was investigated in relation to the pro-coagulant activity of PC cell-derived MVs.
Comparing the procoagulant activity of MVs derived from two PC cells lines, MVs from the more aggressive DU145vIII and more metastatic PC3-MLN4 show increased thrombin generation compared to MV’s from DU145 and PC3. Cell culture MVs were observed to generate thrombin independently of any added components from the coagulation cascade. Moreover, MVs from PC patients with a metastasized tumour had increased thrombin generation than patients with benign tumours. Lastly, PC MV’s led to the truncation and activation of PAR1 in CHO (hPAR1), indicating thrombin generation.
Our in vitro studies suggest a potential role of PC MV’s in the migratory thrombosis observed in Trousseau’s syndrome, due to their independent ability to generate active thrombin. We also demonstrated that oncogenes could regulate the pro-coagulant properties of PC-derived MVs, by enhancing their thrombin generation with increasing metastatic phenotype. PAR1 has been implicated in many cancerous properties, such as promoting cellular invasion and angiogenesis. Thus, activation of PAR1 indicates a pro-coagulant role of prostate tumour-derived MVs, and illustrates their potential in the regulation of angiogenesis and cancer development.