miR-505 inhibits cell growth by inducing apoptotic cell death in MCF7-ADR. (A) Images show typical MCF7-ADR cells transfected with miR-505 (top) and control miRNA (bottom) in 72 hours. (B) DNA copy number on the miR-505 locus of MCF7-ADR deleted as compared with that of MCF7. (C) Real-time RT-PCR analysis was performed to determine expression levels of miR-505 in parental cell line MCF7 and drug-resistant cell line MCF7-ADR. Error bar represents S.D. of triplicate determinations in a single experiment. P < 0.05. (D). Seventy-two hours after transfection, caspase-7 activity in the presence or absence of DOC (1 nM) was detected in miR-505 or control miRNA-transfected MCF7-ADR cells. n = 6, P < 0.001. (E) Condensed and fragmented apoptotic cells are counted in the presence or absence of DOC (1 nM) by staining with Hoechst dye. n = 4, P < 0.05. Mean ± S.D. is shown. (F) Images of apoptotic nuclear condensation and fragmentation. Seventy-two hours after transfection with miR-505 (top) or control miRNA (bottom), condensed and fragmented cells are observed. White arrows show apoptotic cells in culture.