Abstract: Objective To investigate the effect of knocking-down microRNA-221 (miR-221) expression on the radiosensitivity of
human colorectal carcinoma cells. Methods Human colorectal carcinoma-derived cell line Caco2 was transfected with miR-221
antisense oligonucleotides (anti-miR-221) via Lipofectamine 2000. Real-time quantitative PCR was performed to detect the
expression of miR-221 and PTEN mRNA in Caco2 cells. The changes in the protein expression of PTEN in the transfected cells
were detected by Western blotting. The cell death after transfection and irradiation was detected by flow cytometry. Results
Transfection with anti-miR-221 caused a significant reduction in miR-221 expression (P<0.05) and up-regulated PTEN protein
expression (P<0.05) in Caco2 cells. The percentage of cell death was significantly increased in anti-miR-221 group and
anti-miR-221 with irradiation group (P<0.01). Anti-miR-221 significantly enhanced the radiosensitivity of Caco2 cells, which
was partially reversed by PTEN-siRNA. Conclusion Anti-miR-221 can enhance the radiosensitivity of colorectal carcinoma
cells by up-regulating the expression of PTEN.