Objective: Cisplatin (CDDP) is a key drug used to treat ovarian carcinoma that activates the mitogen-activated protein kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) signaling cascade and a phosphatidylinositol 3′-kinase (PI3K)-Akt pathway, both of which are considered pathways for cell proliferation and survival. The present study aimed to elucidate the roles of the MEK-ERK and PI3K-Akt pathways in regulating cytotoxicity in ovarian carcinoma cells induced by CDDP.

Methods: Seven human ovarian serous adenocarcinoma cell lines were used in this study (KF, KFr, KOC-2S, SK-OV-3, SHIN-3, TU-OS-3, and TU-OS-4). We treated the cell lines with CDDP combined with PI3K inhibitor (LY294002 [LY]), MEK inhibitor (PD98059 [PD]), or ERK activator (phorbol 12-myristate 13-acetate [PMA]), then assessed cell viability by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The levels at which proteins expressed MEK, phosphorylated (p)MEK, ERK, pERK, Akt, pAkt, and cleaved caspase-9 were detected by western blotting. Cell cycle distribution and apoptotic cells were determined by flow cytometry, 5-bromo-2-deoxyuridine (BrdU) incorporation, and staining with Annexin V.

Results: The range of IC50 to CDDP was 2.4 to 26.9 μM for those cell lines. KFr, a CDDP-resistant cell line, was established from KF cells, and the IC50 to CDDP was 9.6 μM. We defined the cell lines which had 9.6 μM or higher IC50 value as CDDP-resistance. Proteins MEK, pMEK, Akt, pAkt, ERK and pERK were expressed in all cell lines. CDDP combined with LY had an additive effect on inhibiting growth of cells in all lines. In contrast, we observed an antagonism for all cell lines when CDDP was combined with PD. Interestingly, growth of cells was dramatically suppressed when CDDP was combined with PMA in the CDDP-resistant cells (KFr, SK-OV-3, SHIN-3, TU-OS-3, TU-OS-4). Treatment with PMA upregulated protein expression levels of pERK and cleaved caspase-9 only in the CDDP-resistant cells. CDDP combined with PMA increased the S-phase fraction and apoptotic cells in the CDDP-resistant cells. Conclusion: ERK activated by PMA may overcome resistance to CDDP in ovarian carcinoma cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3543.