Abstract: ObjectiveTo evaluate the effect of microRNA92a (miR92a) on regulating cell proliferation by targeting Krüppellike factor 4 (KLF4) in colon cancer. MethodsThe miR92a expressions in 21 colon cancer tissues and matched normal tumoradjacent tissues and 4 colon cancer cells (HT29, SW480, SW620, HCT116) were detected using quantitative realtime polymerase chain reaction (qRTPCR). Models of overexpression and suppression of miR92a were established by transient transfection of miR92a3p mimic to HCT116 and transient transfection of miR92a3p inhibitor to SW620, respectively. Cell proliferation activity was detected by the CCK8 colorimetry method, cell cycles were detected by flow cytometry, KLF4 protein expression was detected by Western blotting, and cell luciferase activity was detected by the dual luciferase reporter gene experiment. ResultsThe expression level of miR92a in colon cancer tissues was (0.648±0.489) fmol/μg total RNA, significantly higher than that in matched normal tumoradjacent tissues ［(0.064±0.062) fmol/μg total RNA］, with statistically significant difference (t=-5.420, P＜0.001). In 4 colon cancer cell lines, the miR92a expression level in HCT116 cells was the lowest, and highest in SW620 cell. When the expression of miR92a was upregulated, the cell proliferation activity of 72 h in HCT116 cells was higher than that in the negative control group (0.919±0.014 vs. 0.765±0.025), with statistically significant difference (t=-9.309, P=0.001), the proportion of S phase cells was also significantly increased ［(41.670±0.461)% vs. (38.703±0.554)%, t=-7.127, P=0.002), and KLF4 protein expression was decreased (0.460±0.048 vs. 0.758±0.109, t=22.865, P=0.028). When the expression of miR92a was downregulated, the cell proliferation activity of 72 h in SW620 cells was lower than that in the negative control group (0.608±0.011 vs. 0.713±0.005), with statistically significant difference (t=15.920, P＜0.001), while the proportion of S phase cells was decreased ［(31.935±0.365)% vs. (34.955±0.465)%, t=8.849, P=0.001］, and KLF4 protein expression was increased (0.694±0.121 vs. 0.479±0.044, t=-5.246, P=0.034). KLF4 3′UTR wildtype dual luciferase report plasmids were cotransfected with miR92a3p mimic to HCT116 cell, and dual luciferase assay showed that miR92a slightly repressed firefly luciferase actively, but the difference was not statistically significant (t=0.878, P=0.429). There was a negative correlation between the expression of miR92a and the expression of KLF4 protein in colon cancer tissues, but with no statistical significance (r=-0.163, P=0.699). ConclusionmiR92a is highly expressed in colon cancer tissues. It can promote colon cancer cells proliferation via enhancement of the cell cycle transition of G0G1 phase to S phase. Upexpression of miR92a may play a role in downregulating the expression of KLF4 protein in colon cancer cells. However, KLF4 is not a direct target gene of miR92a.

Key words: Colonic neoplasms, Cell proliferation, MicroRNA-92a, Krüppellike factor 4