Effect of synthetic small double-stranded RNA on the development of bladder cancer by activating P21 expression

Abstract

To investigate the effects of a synthetic small double-stranded RNA (dsRNA) dsP21-555 on the development of bladder cancer cell lines T24 and EJ. According to the different treatments, bladder cancer cells were divided into three groups: negative control group (transfected with dsControl), positive control group (transfected with candidate microRNA, i.e. miR-370) and experimental group (transfected with dsP21-555). Real-time fluorescent quantitative polymerase chain reaction (qPCR) was conducted to detect the expressions of p21 mRNA and cyclin-dependent kinases 4/6 (CDK4/6) mRNA; Western blot was operated to verify the expression of P21 and CDK4/6 proteins. Cell cycle distribution was measured by flow cytometry after transfection. Cell proliferation assay was performed to evaluate the proliferative capacity of transfected cells. Colony formation assay was carried out to analyze the proliferative ability of single cancer cells. qPCR showed that, compared with the negative control group, dsP21-555 up-regulated the expressions of p21 mRNA by 2.46 times (P<0.01) in T24 cells and 2.60 times (P<0.01) in EJ cells; compared with the positive control group, the expression of p21 mRNA was no significantly different in the experimental group (P>0.05). Compared with the dsControl group, dsP21-555 suppressed the expressions of CDK4 mRNA by 43% (P<0.01) in T24 and 54% (P<0.01) in EJ cells, the expression of CDK6 mRNA by 39% (P<0.01) in T24 and 36% (P<0.01) in EJ cells; the differences in the expression of CDK4 and CDK6 mRNAs between the miR-370 and dsP21-555 groups were not statistically significant (P> 0.05). Western blot verified the differences of p21 and CDK4/6 genes expression among groups. Flow cytometry revealed that the G0/G1 phase cells significantly increased while S and G2/M phase cells decreased in the miR-370 and the dsP21-555 groups, compared with the dsControl group. Cell proliferation assay showed that, compared with the dsControl group, the proliferative capacities of cells transfected with miR-370 or dsP21-555 decreased significantly (both P<0.05), but the difference in proliferative capacities between the miR-370 and the dsP21-555 groups was no statistically significant (P>0.05). Colony formation assay showed that the numbers of colonies formed in the miR-370 and the dsP21-555 groups were both smaller than that in the dsControl group. dsP21-555 may activate the expression of P21 protein by RNA activation, thereby significantly inhibit the growth of bladder cancer cells.