Plasma Tissue Factor (TF) Antigen, Cellular Microparticles and Markers of Coagulation and Platelet Activation in Localized Prostate Cancer.

Coagulation and platelet activation are involved in tumor growth and dissemination, and recent trials have demonstrated promising efficacy of low-molecular-weight heparin (LMWH) in cancer treatment. It is unclear, however, which subgroup of patients benefits most from anticoagulant therapy, although LMWH may be most effective in limited-stage malignancy. About 15–20% of patients with localized prostate cancer (PC) experience recurrent local and/or metastatic disease after radical prostatectomy. We conducted a prospective study to identify laboratory markers of hypercoagulability in early-stage PC, providing a potential rational for adjuvant anticoagulant treatment strategies in this tumor entity. In 98 consecutive patients with clinically localized PC (62±6 years), we found significantly higher preoperative plasma levels of TF (median, 95 vs. 0 pg/ml), prothrombin fragment F1+2 (1.6 vs. 1.1 nmol/l), plasmin-antiplasmin complex (339 vs. 238 ng/ml), and D-dimer (0.27 vs. 0.17 mg/l) than in 42 sex- and age-matched controls (P<0.001). Patients with organ-confined (pT2) and histologically more differentiated tumors (Gleason sum, <7) had lower D-dimer levels than patients with pT3 (P=0.06) and less differentiated tumors (P=0.02). No association was found between hemostatic parameters and preoperative PSA values, lymph node involvement, or positivity of resection margins. Since TF has been implicated in tumor angiogenesis and metastasis, additional studies were performed to elucidate the cellular origin of measured TF antigen levels. To this end, platelet- (PMP) and leukocyte-derived microparticles (LMP) were enumerated by flow cytometry in 18 controls and 36 patients using FITC-conjugated antibodies against CD41 for PMP detection and CD11b or CD14 for LMP detection. Background fluorescence was determined by IgG-FITC control antibody. Calibration microspheres were used to gate all FITC+ events according to their size (forward scatter) and to correct for variations in sample flow. Only FITC+ events <1 μm were included in the analysis. The intra- and inter-assay CVs for this methodology were <10%. Controls had TF levels <50 pg/ml, and patients had TF levels of either <50 pg/ml (low-TF, n=18) or >200 pg/ml (high-TF, n=18). Compared to controls, median PMP numbers were increased 2-fold in low-TF (P<0.05) and 5-fold in high-TF patients (P<0.001). PMP numbers but not whole blood platelet counts were significantly different between patient groups (P<0.05). Compared to low-TF patients, high-TF patients also had elevated plasma levels of sP-selectin (37±15 ng/ml vs. 23±7, P<0.01) and sCD40L (361±817 vs. 47±95 pg/ml, P=0.26), two markers of in vivo platelet activation. LMP were barely detectable in controls, and their numbers were only slightly increased in patients, representing not more than 5–10% of PMP counts. Using immunohistochemistry on paraffin-embedded specimens, TF was localized predominantly to tissue macrophages and adventitial fibroblasts but not to tumor cells, showing a similar staining pattern in both patient groups. In summary, laboratory evidence of coagulation and platelet activation is already present in early-stage PC. Although TF has been associated with a poor clinical outcome in various types of malignancy, its plasma antigen levels may not reflect tumor cell TF expression in localized PC.