Effect and possible mechanism of BMI-1 gene on radiosensitivity of human pancreatic cancer SW1990 cell line

Objective: To evaluate the effect and possible mechanism of B-cell-specific moloney murine leukemia virus insertion site 1 (BMI-1) on the radiosensitivity of pancreatic cancer SW1990 cell line. Methods: According to our previous study results, 4 Gy X-ray and down-regulation of BMI-1 expression were adopted as intervention conditions. The effect on the proliferation of SW1990 cells was assessed by colony formation assay. The effect on cell apoptosis and cell cycle was evaluated by flow cytometry. The effect upon the epithelial-mesenchymal transition (EMT) was determined by Western blot. Results: Colony formation assay and flow cytometry found that the lowest cell proliferation ability and the highest apoptotic rate were obtained after BMI-1 down-regulation and 4 Gy X-ray compared with other groups (all P < 0.05). Flow cytometry revealed that the proportion of G₀/G₁ phase was significantly decreased, whereas the G₂/M phase was remarkably increased in pancreatic cancer stem cells treated with 4 Gy X-ray compared with the control group (both P < 0.05). Nevertheless, opposite results were obtained after down-regulation of BMI-1 expression. Western blot showed that the expression of E-cadherin was up-regulated, whereas that of Vimentin was down-regulated following 4 Gy X-ray (both P < 0.05). Conclusion: Downregulation of BMI-1 expression can enhance the radiosensitivity of pancreatic cancer SW1990 cells, and its mechanism may be related to cell cycle and EMT. (authors)