Expression and significance of IKKε in the specimens and cells of epithelial ovarian cancer

Abstract

Objective: To examine the expressions of IKKε protein in the specimens and cells of epithelial ovarian cancer and investigate the effect of IKKε inhibitor on cell proliferation and apoptosis. Methods: (1) A total of 118 cases of patients with the median age of 59 who have accepted surgical treatment due to ovarian cancer in the First Affiliated Hospital of Dalian Medical University from January 2006 to April 2013 were selected. Twenty cases of patients with the median age of 55 who have accepted hysterectomy and salpingo-oophorectomy due to uterine leiomyoma during the same period were selected as the control. The expressions of IKKε protein were detected by immunohistochemistry in normal ovarian tissues and epithelial ovarian cancer specimens, and the relationship between the expressions of IKKε and the clinical features of patients was analyzed. IKKε protein was determined by western blot in various ovarian cancer cells, including SKOV3, OV2008, C13, A2780S, A2780CP, OV4, OV5, OV8, and CAOV3 treated with or without IKKε inhibitor. The cellular proliferation and apoptosis of ovarian cancer cells after 48 hours treatment of IKKε inhibitor were analyzed by methyl thiazolyl tetrazolium (MTT) assay and flow cytometry, respectively. Results: (1) The immunohistochemical results showed that IKKε was highly expressed in epithelial ovarian cancer specimens with the expression rate 66.1% (78/118), compared with normal ovarian tissue with the expression rate 35.0% (7/20), which exhibited statistically significant difference (χ(2)=6.993, P=0.008). The expression of IKKε protein was correlated with International Federation of Gynecology and Obstetrics (FIGO) stage, histological grade, the level of CA(125) in preoperative serum and distribution of the tumor (P<0.05), but no correlation with age, histological type, the incidence pattern, and tumor size (all P>0.05). (2) IKKε was widely overexpressed in different levels in SKOV3, OV2008, C13, A2780S, A2780CP, OV4, OV5, OV8, and CAOV3 cells, and the expression of IKKε decreased as the increase of the concentration of IKKε inhibitor (0.1 and 0.5 μmol/L) in OV2008, C13, A2780S, and A2780CP cells after 48 hours treatment. Different concentrations of IKKε inhibitor (0.05, 0.1, 0.5, 1, 5, 10, and 25 μmol/L) significantly inhibited the proliferation of OV2008, C13, A2780S, A2780CP, and SKOV3 cells in a concentration-dependent manner (P<0.05), and the half maximal inhibitory concentration (IC(50)) was 0.43, 0.86, 0.10, 0.19, and 0.24 μmol/L, respectively. The cell apoptotic rate of OV2008, C13, A2780S, A2780CP, and SKOV3 cells was significantly increased after 48 hours treatment of IKKε inhibitor with the concentration of 0.1 and 0.5 μmol/L (P<0.05). Conclusions: The IKKε protein in epithelial ovarian cancer specimens and cells is overexpressed. IKKε inhibitor could inhibit cellular proliferation and induce apoptosis in a concentration-dependent manner. Together, the result indicated that IKKε may be a candidate target for the treatment of ovarian cancer in future.