To investigate the effect of miR-210 down-regulation on radio-sensitivity of hypoxic human hepatoma SMMC-7721 cells, lentivirus vector carrying miR-210 anti-sense or scrambled oligos was constructed by molecular biology techniques, and SMMC-7721 Cells with stable integration of the anti-sense miR-210 or scrambled sequence were generated through lentiviral-mediated gene transfer. Time courses of HIF-1α mRNA expression and miR-210 expression in SMMC-7721 cells exposed to 1% oxygen were analyzed by real-time RT-PCR. Cell viability was measured by MTT assay. Cell cycle and apoptosis were measured by flow cytometry assay. Radio-sensitivity of hypoxic SMMC-7721 cells was examined using a colony-forming assay. The results showed that hypoxia resulted in an increment of HIF-1α and miR-210 expression in SMMC-7721 cells. Stable integration of anti-sense miR-210 sig-nificantly decreased hypoxia-induced miR-210 expression. MiR-210 down-regulation decreased viability of hypoxic SMMC-7721 cells (P<0.05 or P<0.01). SMMC-7721 cells with miR-210 down-regulation arrested in the G0/G1 phase of cell cycle after 72 h hypoxic culture (P<0.05). Apoptotic rate of cells with miR-210 down-regulation was signifi-cantly increased (P<0.01) after 48 and 72 h hypoxic culture. MiR-210 down-regulation could enhance the ra-dio-sensitivity of hypoxic SMMC-7721 cells with a radio-sensitization ratio of 1.21. These results suggest that miR-210 down-regulation can inhibit proliferation, induce apoptosis and enhance radio-sensitivity in hypoxic human hepatoma SMMC-7721 cells in vitro.Cited