Plasma endothelial protein C receptor influences innate immune response in ovarian cancer by decreasing the population of natural killer and TH17 helper cells

Abstract

In spite of the growing importance of endothelial protein C receptor/active protein C (EPCR/aPC) in tumor biology, their impact on immunological homeostasis remains largely unexplored. The objective of this study was to assess whether soluble plasma endothelial protein C receptor (sEPCR), which is a regulator of circulating aPC, is involved in innate immune response in cancer patients. In the Ovcar-3 ovarian cancer line, the role of aPC in secretion of cytokines was analyzed. In parallel, in 33 patients, with a diagnosis of ovarian epithelial cancer, sEPCR was quantified, blood immune cell phenotypes were determined by flow cytometry and plasma cytokines were evaluated using a protein array. Spearman’s rank correlation coefficients (r) and coefficient significance was determined by a statistical hypothesis test (α=0.05). Our results show that i) aPC induced the secretion of several cytokines in Ovcar-3 cells; ii) 61% of patients exhibited a concentration of plasma sEPCR well above the baseline (normal plasma level, 100±28 ng/ml); iii) comparing immune cell phenotypes in patients having a normal level of sEPCR with those having a high level of sEPCR, it was found that sEPCR levels were correlated with high intensity of cells expressing CD45ra, CD3, CD8, CD25 and low intensity of cells expressing CD56 (NK cells), CD294 (TH2 cells), IL-2, IL-10, IL-17a (TH17 cells), IL-21 (TH21 cells) and CD29 markers (r ≥0.60); and iv) high levels of sEPCR correlate with high levels of plasma bioactive proteins such as insulin-like growth factor-2 (IGFII), IL-13rα, macrophage inflammatory protein (MIP1α) and matrix metalloproteinase-7 (MMP-7) that have already been proposed as biomarkers for ovarian cancer and particularly those with poor prognosis. In conclusion, sEPCR produced by ovarian cancer cells, by modulating circulating aPC, influences the secretory behavior of tumor cells (cytokines and interleukins). Consequently, sEPCR in turn acts on the innate immune response by decreasing effector cells such as natural killer and T helper cells (TH2, TH17 and TH21).

Thrombopoietin Secretion by Human Ovarian Cancer Cells

“…In contrast no TPO was extracted from breast cancer cell line (MDA-MB231), compared with ovarian or leukemic cells. Previously we found that when OVCAR-3 cells were incubated with activated protein C, the cancer cell migration was upregulated via MEK-ERK and Rho-GTPase pathway signalization [31] and the amount of secreted TPO in the culture medium detected by cytokine array increased four times [22]. In nonpublished results, we also demonstrated that activated protein C and, to a lesser degree, protein C induced the microparticles release in OVCAR-3 cell line.…”

“…We also observed that activated protein C (aPC), a natural anticoagulant, increased OVCAR-3 TPO secretion [22]. …”

Activated protein C upregulates ovarian cancer cell migration and promotes unclottability of the cancer cell microenvironment

“…On endothelial cells, the aPC, together with its cofactor protein S, degrades factors Va and VIIIa and thereby interferes with thrombin generation and abolishes the coagulation cascade ( 12 ). Endogenous aPC is shown to limit cancer cell extravasation through S1P-1-mediated vascular endothelium ( 13 ) and also plays a role in innate immune system ( 14 , 15 ).…”

High IL-17 expression is associated with an unfavorable prognosis in thyroid cancer

“…Although the Th17 profile is involved with increased immunity and host defenses, its involvement in neoplastic processes remains controversial (6,10). Previous studies suggest that Th17 cells are involved in cancer promotion (11)(12)(13)(14)(15). Notably, in the tumor microenvironment, Th17 cells have been observed to positively correlate with immune effector cells, including CD8+ T cells and natural killer cells, promoting an antitumor response that is mediated by cytotoxic cells (11,12).…”

“…Previous studies suggest that Th17 cells are involved in cancer promotion (11)(12)(13)(14)(15). Notably, in the tumor microenvironment, Th17 cells have been observed to positively correlate with immune effector cells, including CD8+ T cells and natural killer cells, promoting an antitumor response that is mediated by cytotoxic cells (11,12). As a result of the production of pro-inflammatory cytokines by Th17 cells that accumulate in the tumor microenvironment, and the association between the development and progression of cancer, a positive correlation between these cells and disease progression has been hypothesized (13,14).…”