Beclin 1 Protein Enhances Sensitivity of Triple-negative Breast Cancer Cell Line BT-549 to 5-Fu by Promoting Cell Apoptosis

Objective To investigate the effect of Beclin 1 protein on the sensitivity of triple-negative breast cancer cell line BT-549 to 5-Fu. Methods pLenO-GTP-BECN1 vectors were transfected into BT-549 cells respectively via lentiviral method. Puromycin selection was used to select positive cells. The negative and the blank control groups were established. BT-549 cells of each group were treated with different concentrations of 5-Fu. MTT assay was performed to compare the sensitivity of BT-549 cells to 5-Fu. FCM and Hoechst33342 dying method were employed to investigate cell apoptosis. Western blot was performed to detect the expression of apoptosis-related protein Caspase-3 and Caspase-8. Results BT-549 cells with stable expression of Beclin 1 were successfully established. The pLenO-GTP-BECN1 group was more sensitive to 5-Fu than other two groups. After treated by 5-Fu for 48h, IC50 of 5-Fu in pLenO-GTP-BECN1 group was(3.54±0.20) μg/ml, which was significantly lower than those in pLenO-GTP group(14.45±1.81) μg/ml and blank group (79.40±8.34)μg/ml(F=207.902;P<0.00). Before 5-Fu treatment, the apoptosis rate of pLenO-GTP-BECN1 group was (12.14±0.76)%, which had no significant difference with those of pLenOGTP group(13.57±1.04)% and blank group(13.75±1.29)% (F=2.096; P=0.204);After treated by 5-Fu for 48h, the apoptosis rate of pLenO-GTP-BECN1 group was (51.01±3.26)%, which was significantly higher than those of pLenO-GTP group(42.17±4.6)% and blank group (38.42±2.93)%(F=9.32;P<0.01).The characteristic changes of nucleus apoptosis in pLenO-GTP-BECN1 group were more apparent than those in the other two groups. After 5-Fu treatment, the relative expression of Caspase-3 in pLenO-GTP-BECN1 group was(0.57±0.0028),which was significantly higher than those in pLenO-GTP group(0.42±0.010) and blank group(0.30±0.046)(F=46.134; P<0.01);and the relative expression of Caspase-8 in pLenO-GTP-BECN1 group was(0.44±0.0038),which was significantly higher than those in pLenO-GTP group (0.18±0.0095) and blank group(0.27 ±0.00060)(F=1006.757; P<0.00). Conclusion Beclin 1 greatly enhances the sensitivity of BT-549 cells to 5-Fu, in which the promotion of apoptosis may be an important mechanism.