Rosiglitazone elevates sensitization of drug-resistant oral epidermoid carcinoma cells to vincristine by G2/M-phase arrest, independent of PPAR-γ pathway

Rosiglitazone (ROSI), an oral antidiabetic agent, has been reported the anti-cancer properties recent years. In this paper, the potency of ROSI as a synergistic drug for vincristine (VCR) on resistant oral cancer cells was investigated. We found that ROSI potently enhanced the susceptibility of KB cells or KB/V cells to VCR in a dose manner and the synergy in KB/V cells was much more prominent than that in KB cells. The synergistic anti-proliferative effect of ROSI and VCR was associated with inhibition on tubulin polymerization, cell cycle arrest in G2/M phase and cell apoptosis induction, but has no effect on drug efflux-protein P-gp and was independent with PPARγ. The combination treatment of ROSI and VCR could regulate the PTEN/PI3K/AKT survival pathway with an upregulation of PTEN and down-regulation of p-AKT. The effect of G2/M phase arrest was associated 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 had also shown anti-angiogenic effect by suppressing the migration and blocking the capillary tube formation of HUVECs. More importantly, this combination treatment induced an acceptably weak cytotoxicity in human normal HL-7702 cells, GES-1 cells and HUVECs. Taken together, ROSI may be used as a potential compound for combinatorial therapy or as a complement to VCR for treatment on oral cancer, especially on that have acquired resistance to VCR therapy.