[Mechanism of chloroquine in promoting sensitivity of chemotherapeutics in oral squamous cell carcinoma CAL-27 cell line to cisplatin].

Purpose: To study the role and mechanism of autophagy in chemotherapy of oral squamous cell carcinoma, and provide theoretical evidence to improve chemotherapeutic efficacy of oral squamous cell carcinoma patients.

Methods: The cell survival rate changes induced by cisplatin (DDP) and chloroquine (CQ) in CAL-27 cells were assayed by methyl thiazolyl tetrazolium method(MTT). The LC3-II expression level was detected by laser scanning confocal microscope; The apoptotic rate was determined by flow cytometry. SPSS17.0 software package was used for statistical analysis.

Results: MTT results showed that compared with the control group, the cell survival rate reduced with the increasing time of DDP and CQ treatment; The optimal concentration of CAL-27 cells was 5 mg/L after treatment with CQ. IC50 of the CAL-27 cells was 5 mg/L after treatment with DDP; MTT results showed that the cell survival rate of CQ+DDP group was significantly lower than control group, CQ group and DDP group (P<0.05). With the action of CQ and DDP to CAL-27 cells for 48 hours, immunofluorescence results showed that the average fluorescence intensity of DDP group was significantly higher than the other 3 groups (P<0.05), while it was significantly lower in CQ group than the other 3 groups (P<0.05). With the action of CQ and DDP to CAL-27 cells for 48 hours, flow cytometry results showed that the cell apoptosis rate of DDP group and CQ+DDP group were significantly higher than control group and CQ group. The cell apoptosis rate of CQ+DDP group was significantly higher than DDP group (P<0.05). With the action of CQ and DDP to CAL-27 cells for 48 hours, cells in G1 phase of DDP group and CQ+DDP group increased, indicating G1 phase blockage. The cell count in G1 phase of CQ+DDP group was significantly higher than DDP group (P<0.05).

Conclusions: Inhibition of autophagy can enhance the chemotherapeutic sensitivity of DDP in CAL-27 cells. Autophagy in CAL-27 cells is an important mechanism for chemotherapy resistance of oral squamous cell carcinoma. Autophagy inhibitor may have significant potential to be a novel chemotherapeutic sensitizer for oral squamous cell carcinoma.