Enhanced radiosensitivity and G2/M arrest were observed in radioresistant esophageal cancer cells by knocking down RPA expression.

Abstract

The aim of this study was to evaluate the changes in radiosensitivity of radioresistant esophageal cancer cells (TE-1R) after disruption of replication protein A (RPA) expression and to explore the potential mechanism. A radioresistant human esophageal cancer cell line TE-1R was established by treating TE-1 cells with the radiation. Then, siRPA1 or -2 was transfected to TE-1R cells. The untransfected group (control) and nonsense short interfering RNA (siRNA) transfected group (NC) were used as controls. To investigate the radiosensitivity changes of TE-1R cells, the dose-survival curve was established by colony-forming assay, and the cell cycle distribution was measured by flow cytometry. (1) Comparing with control and NC groups, the protein expression of RPA1 and -2 decreased significantly 48 h after siRPA1 or -2 transfection. (2) The D 0, D q, and SF2 values reduced from 2.09, 1.70, and 0.85 in NC group to 1.67, 0.71, and 0.44 and 1.82, 0.89, and 0.51 in siRNA1 and siRPA2 transfected groups, respectively. The D q sensitization enhancement ratios (SERDq) were 2.39 and 1.91 in siRNA1 and siRPA2 transfected groups, respectively. (3) The G2/M arrest was significantly caused by siRPA1 or -2 transfection as compared with that in the NC group (t value was 2.827, 2.853, p < 0.05). Post transcriptional silencing of RPA1 or -2 via RNAi can enhance the radiosensitivity of human esophageal cancer cells TE-1R, and the potential mechanism may be related to the inhibition of post-radiation sublethal damage repair and the halted cell cycle progression at G2/M phase. Therefore, RPA may become a new target for radiosensitization enhancement in esophageal cancer.