The Study Of Effect And Related Mechanism Of IL-6 Induced Ovarian Cancer Cells Resistance To Chemotherapy

Objective: Ovarian cancer(OVCA) is the second most common and the most deadly malignancy of the female reproductive tract, however, most patients already diagnosed late. The surgery that complete annihilation of cells and cisplatin and paclitaxel-based combination chemotherapy are their mainly treatment, but long-term effect is not very satisfactory, the occurrence of drug resistance is a major constraint factor in clinical treatment. In recent years, studies have shown that interleukin-6 (Interleukin6, IL-6) is highly expressed in ovarian cancer cells, it not only play an important role in OVCA occurrence and development, but also affect the sensitive to chemotherapeutics. It is not yet clear the role and mechanism of IL-6 on chemotherapy resistance in ovarian cancer currently. The subject first observed the expression levels of IL-6 on the impact of chemotherapy-resistant in ovarian cancer cells, then the mechanisms and the related signal pathways were also discussed.Methods: At first, enzyme linked immunosorbent assay (ELISA), Western Blot analysis and Reverse transcription polymerase chain reaction (RT-PCR) were performed to analyze the expression of IL-6 and it's receptor, drug resistance-associated genes and apoptosis-inhibiting genes, then MTT assay was carried out to examine the sensitivity to cisplatin and paclitaxel in ovarian cancer cells.Based on the result of before, we choose not secretion of IL-6, but expression it's receptor, to cisplatin and paclitaxel-sensitive A2780 cells, and high secretion of IL-6, high expression it's receptor, resistant to cisplatin and paclitaxel SKOV3 cells as research model. At first, MTT and RT-PCR were performed to observe the effect of exogenous IL-6 on the sensitivity to cisplatin and paclitaxel, the expression of drug resistance-associated genes and apoptosis-inhibiting genes in A2780 cells. Moreover, stable cell lines overexpressing or deleting of IL-6 were cloned to investigate the effect of IL-6 on the sensitivity to cisplatin and paclitaxel, the expression levels of drug resistance-associated genes and apoptosis-inhibiting genes. Meanwhile, we also analyzed the related signal pathways of chemotherapy resistance caused by exogenous IL-6 or endogenous overexpressing of IL-6 in ovarian cancer cells through PD98059 (inhibitor of MEK1/2) and Wortmannin (inhibitor of PI3K).Results: The research of four cells show: (1) Four ovarian cancer cells all constitutively expressed IL-6 except A2780. The mRNA levels of IL-6 resembled it's respective protein levels. Also four cells all expressed IL-6Rαand gp130. (2) The sensentivity to cisplatin and paclitaxel in four ovarian cancer cells is different. A2780 cells are the most sensentive, ES-2 cells are less, whereas CAOV-3 and SKOV-3 cells are drug-resistant. (3) The expression levels of drug resistance-associated genes and apoptosis-inhibiting genes are lower in A2780 and ES-2 cells, where those are higher in CAOV-3 and SKOV-3 cells.Based on the research of A2780 cell and SKOV3 cell, we find out that: (1) Exogenous IL-6 can significantly reduce the sensitivity to cisplatin and paclitaxel in A2780, but increases expression of drug resistance-associated genes MDR1, GST-πand apoptosis-inhibiting genes Bcl-2, Bcl-xL, XIAP by a dose-dependent manner. (2) Stably expression recombinant ssIL-6 clones incloude A2780/ssIL-6L, A2780/ssIL-6M, A2780/ssIL-6H, and asIL-6 clones include SKOV3/ asIL-6MI, SKOV3/asIL-6HI and their respective empty vector were obtained. (3) The drug resistance to cisplatin and paclitaxel, expression levels of drug resistance-associated genes and apoptosis-inhibiting genes in the ssIL-6 transfected cells were increased compared with the empty vector pcDNA3.1(+)/A2780 clones and non-transfected A2780 cells, whereas those in the asIL-6 transfected cells were decreased compared with the empty vector pcDNA3.1(+)/SKOV3 clones and non-transfected SKOV3 cells. (4) Pretreatment of A2780 cells with PD98059 (inhibitor of MEK1/2) and Wortmannin (inhibitor of PI3K) can block exogenous IL-6-induced cisplatin and paclitaxel resistance, also the inhibition was found in A2780/IL-6(H) clones.Conclusion: Autocrine production levels of IL-6 in epithelial ovarian cancer cell lines were inversely associated with their sensitivity to cisplatin or paclitaxel, and chemotherapy-resistant ovarian cancer cells induced by IL-6 may be the role of the mechanisms that IL-6 up-regulated the expression levels of drug resistance associated genes and apoptosis inhibiting genes through the Ras/MEK, PI3K/Akt signal transduction pathway.