CAFs enhance paclitaxel resistance by inducing EMT through the IL‑6/JAK2/STAT3 pathway.

Abstract

Carcinoma-associated fibroblasts (CAFs) are the major components of mesenchymal cells in the inflammatory tumor microenvironment. They are involved in epithelial-mesenchymal transition (EMT) and chemotherapy resistance by directly contacting with cancer cells or secretory cytokines. In the present study, we examined the role of CAFs in the induction of EMT in ovarian cancer. Primary ovarian cancer cells, CAFs and normal fibroblasts (NFs) were isolated from fresh cancer tissue and cultured for immunohistochemistry studies. Enzyme-linked immunosorbent assay (ELISA) was used to detect the expression of IL-6 in the culture supernatants of these cells. The expression of IL-6 at the mRNA level was examined by RT-PCR. The expression of IL-6 at the protein level in ovarian cancer tissues was determined using an immunofluorescence assay in both tissue sections and cell lobes. OVCAR3 cells were treated with the culture supernatants collected from CAFs and NFs. IL-6 monoclonal antibody (mAb) was employed to neutralize IL-6. The expression of phosphorylated STAT3 was assessed. Changes in EMT, proliferation, invasion and proapoptotic protein expression were also examined. Flow cytometry was performed to detect the changes in apoptosis resistance of OVCAR3 cells. The JAK2/STAT3 pathway-specific inhibitor AG490 was used to block this pathway and the β-TGF inhibitor was used to inhibit EMT. The clinical data of patients treated in our hospital were collected between January 1st, 2009 and June 30th, 2013. The expression of interstitial IL-6 in paraffin-embedded tissues was detected by immunohistochemistry. The relationship between the expression of interstitial IL-6 and the treatment response was examined by linear regression and multiple linear regression analyses. We found that CAFs were the main source of IL-6 in ovarian cancer tissue. CAFs promoted the phosphorylation of STAT3 in ovarian cancer and enhanced the proliferation, invasion and EMT. Enhanced EMT may lead to apoptosis resistance, inhibitory expression of pro-apoptotic proteins and paclitaxel resistance. A total of 255 patients were enrolled in this retrospective study. Univariate and multivariate analyses revealed that age, CA125, interstitial IL-6 expression and cytoreduction satisfaction were closely related to the sensitivity of the TP (docetaxel plus cisplatin or carbopatin) regimen in ovarian cancer (P<0.05). These results demonstrated that CAFs highly secreted IL-6 and promoted β-TGF-mediated EMT in ovarian cancer via the JAK2/STAT3 pathway, leading to inhibited apoptosis and subsequent paclitaxel resistance. Therefore, CAFs may be a new therapeutic target for the treatment of ovarian cancer.