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Abstract Background Resistance to apoptosis is a major problem in ovarian cancer and correlates with poor prognosis. Osteoprotegerin (OPG) is a secreted factor in malignant ascites and acts as a decoy receptor for receptor activator of NF-κB ligand (RANKL) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). TRAIL promotes apoptosis in ovarian cancer cells. Ovarian cancer ascites attenuate TRAIL-induced apoptosis raising the possibility that OPG contained in ascites may abrogate the anti-tumor activity of TRAIL. Methods Determination of OPG levels in ascites was measured by ELISA. Effect of OPG on TRAIL-induced cell death was determined by XTT and colony forming assays in ovarian cancer cell lines and primary tumor cells. Apoptosis was assessed by ELISA. Results We found that recombinant OPG and malignant ascites attenuates TRAIL-induced cell death and apoptosis in a dose-dependent manner in ovarian cancer cell lines and primary ovarian tumor cells. OPG is present at high levels in the ascites of patients with ovarian cancer. We found a positive correlation between the levels of OPG in ascites and the ability of the ascites to attenuate TRAIL-induced cell death. The anti-apoptotic effect of ascites was not reversed by co-incubation with an OPG blocking antibody. Conclusions OPG and malignant ascites protect ovarian cancer cells from TRAIL-induced apoptosis. Although malignant ascites contain high levels of OPG, OPG is not a critical component that contributes to ascites-mediated attenuation of TRAIL-induced apoptosis.

Background: Ovarian cancer (OC) ascites consist in a proinflammatory tumor environment that is characterized by the presence of various cytokines, chemokines and growth factors. The presence of these inflammatory-related factors in ascites is associated with a more aggressive tumor phenotype. CCL18 is a member of CCL chemokines and its expression has been associated with poor prognosis in some cancers. However, its role in OC progression has not been established. Therefore, the aim of the current study was to elucidate the role of ascites CCL18 in OC progression. Methods: ELISA and tissue microarrays were used to assess CCL18 in ascites and phospho-Pyk2 expression in cancer tissues respectively. Cell migration was assessed using Boyden chambers. CCL18 and ascites signaling was examined in ovarian cancer cells utilizing siRNA and exogenous gene expression. Results: Here, we show that CCL18 levels are markedly increased in advanced serous OC ascites relative to peritoneal effusions from women with benign conditions. Ascites and CCL18 dose-dependently enhanced the migration of OC cell lines CaOV3 and OVCAR3. CCL18 levels in ascites positively correlated with the ability of ascites to promote cell migration. CCL18 blocking antibodies significantly attenuated ascites-induced cell migration. Ascites and CCL18 stimulated the phosphorylation of proline-rich tyrosine kinase 2 (Pyk2) in CaOV3 and OVCAR3 cells. Most importantly, the expression of phosphorylated Pyk2 in serous OC tumors was associated with shorter progressionfree survival. Furthermore, enforced expression of Pyk2 promoted tumor cell migration while siRNA-mediated downregulation of Pyk2 attenuated cell migration. Downregulation of Pyk2 markedly inhibited ascites and CCL18-induced cell migration. Conclusions: Taken together, our findings establish an important role for CCL18, as a component of ascites, in the migration of tumor cells and identify Pyk2 as prognostic factor and a critical downstream signaling pathway for ascites-induced OC cell migration. [ABSTRACT FROM AUTHOR]

Background Resistance to apoptosis is a major problem in ovarian cancer (OC) and correlates with poor prognosis. Osteoprotegerin (OPG) is a soluble secreted factor that acts as a decoy receptor for receptor activator of NF-κB ligand (RANKL) and tumor necrosis factor-related apoptosisinducing ligand (TRAIL). OPG has been reported to attenuate TRAIL-induced apoptosis in a variety of cancer cells, including OC cells. OPG-mediated protection against TRAIL has been attributed to its decoy receptor function. However, OPG activates integrin/focal adhesion kinase (FAK) signaling in endothelial cells. In OC cells, activation of integrin/FAK signaling inhibits TRAIL-induced apoptosis. Based on these observations, we hypothesized that OPG could attenuate TRAIL-induced apoptosis in OC cells through integrin/FAK signaling. Methods In vitro experiments including immunoblots, colony formation assays, and apoptosis measurements were used to assess the effect of OPG on TRAIL-induced apoptosis. Results Exogenous OPG protected from TRAIL-induced apoptosis in a TRAIL binding-independent manner and OPG protection was αvβ3 and αvβ5 integrin/FAK signaling-dependent. Moreover, OPG-mediated activation of integrin/FAK signaling resulted in the activation of Akt. Inhibition of both integrin/FAK and Akt signaling significantly inhibited OPG-mediated attenuation of TRAIL-induced apoptosis. Although OPG also stimulated ERK1/2 phosphorylation, inhibition of ERK1/2 signaling did not significantly altered OPG protection. Conclusions Our studies provide evidence, for the first time, that OPG can attenuate TRAIL-induced apoptosis in a TRAIL binding-independent manner through the activation of integrin/FAK/Akt signaling in OC cells. [ABSTRACT FROM AUTHOR]

Objectives. In this study, we examine the sensitivity of a panel of ovarian carcinoma cells, which includes four primary ovarian cancer cell samples, and four normal ovarian epithelium samples to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). We also examine the intracellular regulation of TRAIL-mediated apoptosis.Methods. The sensitivity to TRAIL was determined by short-term survival assays on seven ovarian carcinoma cell lines, four primary samples of ovarian cancer, and four normal ovarian epithelium samples. We assessed the activation of the apoptotic pathway in TRAIL-resistant and -sensitive tumor cells. The expression of TRAIL receptors was determined by flow cytometry. The protein expression of FADD, XIAP, caspase-8, caspase-3, BAX, and c-FLIP were determined by immunoblot analyses.Results. We show that ovarian cancer cells display variable sensitivity to TRAIL-induced apoptosis although most cell lines have similar sensitivity to cisplatin. Normal ovarian epithelium samples were mostly sensitive to TRAIL. In sensitive cells, TRAIL induced caspase-8-dependent apoptosis, which subsequently led to activation of caspase-3. Both sensitive and resistant cells expressed caspase-8, caspase-3, FADD, XIAP, and c-FLIP at similar levels. A significant enhancement in cell death was observed in TRAIL-resistant cells when c-FLIPL levels were downregulated by RNA interference.Conclusions. These data suggest that sensitivity to TRAIL and chemotherapy does not necessarily correlate in human ovarian cancer cells. Cancerous cells isolated from patients with ovarian cancer show variable sensitivity to TRAIL but most normal ovarian epithelial cells are sensitive. In human ovarian cancer cells, c-FLIPL may participate to the regulation of the TRAIL signaling cascade. [Copyright &y& Elsevier]