Anti-Tumor Effects Of Rosiglitazone And Vincristine On Oral Epidermoid Carcinoma Cells

Background and objectiveOral cancer is still a serious and growing problem worldwide. Surgery and/or radiotherapy, as well as chemotherapy are the main treatments for oral cancer. Despite the advances in diagnosis and treatment, oral cancer still has lower 5-year survival rate. Vincristine (VCR), as an essential medicine for oral cancer therapy, is limited by the development of multidrug resistance (MDR), the same as other chemotherapeutics in oral cancer. Recently, some drugs (such as quercetin and celecoxib) with anti-tumor activity have been reported to elevate sensitization of drug-resistant oral epidermoid carcinoma cells to VCR, which provide an exciting method for overcoming VCR-drug resistance of tumors. Rosiglitazone (ROSI), an oral antidiabetic agent, has been reported the anti-cancer properties recent years. Emerging evidences indicate that ROSI in combination with conventional chemotherapeutic drugs (such as platinum-based drugs and 5-FU) might increase the therapeutic efficacy with unclear mechanisms. In this study, we examined the anti-tumor efficacy and possible molecular mechanisms of combination treatment of vincristine and rosiglitazone in human oral epidermoid carcinoma cell line (KB cells) and the vincristine-resistant KB cell line (KB/V cells).MethodsThe effects of ROSI on the cytotoxicity of VCR in KB cells and KB/V cells were assessed using MTT assay, CCK-8 assay and clone formation assays. The function of P-glycoprotein (P-gp) was evaluated by Rhodaminel23 accumulation assay. The microtubule organization was assessed with immunofluorescence staining of a-tubulin.The cell cycle distribution was detected using PI staining by flow cytometry. The cell apoptosis was analyzed by Hoechst 33342 nuclear staining as well as the Annexin V-FITC/PI double-staining method. The expression of all proteins was measured by western blotting assay. The anti-angiogenic effect of combination treatment was assessed by wound scratch assay and capillary tube formation assay using HUVECs.ResultsROSI potently enhanced the susceptibility of KB cells or KB/V cells to VCR in a dose-dependent manner and the synergy in KB/V cells was much more prominent than that in KB cells. The synergistic effect of ROSI and VCR was associated with inhibition on tubulin polymerization, G2/M arrest and cell apoptosis induction, but has no effect on drug efflux-protein P-gp and was independent with PPARy. The combination treatment of ROSI and VCR could regulate the PI3K/AKT signal pathway with an upregulation of PTEN and down-regulation of p-Akt. The effect of G2/M arrest might associate with the upregulation of cyclin B1 and downregulation of p-cdc2. The apoptosis induction of ROSI and VCR was partly due to an upregulation of cleaved-PARP and downregulation of Bcl-2/Bax ratio. In addition, combination treatment of ROSI and VCR showed anti-angiogenic effect by suppressing the migration and tube formation of HUVECs. Significantly, this combination treatment induced an acceptably weak cytotoxicity in human normal HL-7702 cells, GES-1 cells and HUVECs.ConclusionROSI enhances the VCR-mediated cell growth inhibition on KB cells and KB/V cells through inhibition of tubulin polymerization, cell cycle G2/M phase arrest, cell apoptosis induction and regulating the PTEN/PI3K/Akt survival pathway. The concomitant use of ROSI and VCR is possibly a novel and promising approach to oral cancer treatment, especially on that have acquired resistance to VCR therapy.