Effect of specific knockdown of BMI-1 on radiosensitivity enhancement in esophageal carcinoma cells

Abstract

Objective To inhibit the expression of B-cell-specificmiv integration site-1(BMI-1) in esophageal cancer ECA109 cells by siRNA interference, and to observe the effects of BMI-1 knockdown on cell proliferation, migration, cell cycle, and apoptosis after exposure to radiation. Methods Effective BMI-1 siRNA was designed and synthesized based on the sequence of the BMI-1 mRNA. ECA109 cells transfected with BMI-1 siRNA and negative control (NC) siRNA were assigned to BMI-1 siRNA group and NC group, while ECA109 cells without transfection were set as a control. Real-time PCR and Western blot were used to determine the mRNA and protein expression of BMI-1 in ECA109 cells, respectively. The Transwell chamber assay was used to evaluate the migration ability of BMI-1-knockdown ECA109 cells. The MTT assay, flow cytometry, and colony formation assay were used to evaluate the effects of BMI-1 knockdown on the radiosensitivity of ECA109 cells. Results Compared with the NC group and the control group, the BMI-1 siRNA group had significantly lower mRNA and protein expression of BMI-1 and significantly reduced cell proliferation and migration after exposure (P=0.024, P=0.000). According to the results of the colony formation assay, there was no significant difference in radiosensitivity between the control group and the NC group (P=0.025, P=0.031), while the BMI-1 siRNA group had significantly higher radiosensitivity than the control group and the NC group (P=0.000). According to the results of flow cytometry, the BMI-1 siRNA group had a significantly lower percentage of G2/M cells and significantly increased apoptosis after exposure than the control group and the NC group (P=0.000, 0.000); however, there was no significant difference in apoptosis between the three groups before radiation (P=0.350). Conclusions SiRNA-mediated BMI-1 knockdown and X-ray radiation effectively reduce the expression of BMI-1, inhibit sublethal damage repair, and increase the radiation lethality in esophageal cancer ECA109 cells. Key words: BMI-1 gene; RNA interference; DNA damage; Radiosensitivity