Cisplatin-induced apoptosis in osteosarcoma cells with overexpression or knockdown/inhibition of TWIST and/or miR-33a. In Saos-2 cells, TUNEL (terminal deoxynucleotidyl transferase mediated nick-end labeling) assays were performed in normal control cells (NC), cells stably transfected with empty pcDNA3 vector (VC), cells overexpressing TWIST, cells overexpressing miR-33a, cells transfected with antagomir-33a, cells overexpressing TWIST and miR-33a, and cells overexpressing TWIST plus transfection of antagomir-33a. In MG-63 cells, TUNEL assays were performed in normal control cells (NC), cells stably transduced with scramble control shRNA (SC), cells stably expressing TWIST-shRNA (T-shRNA), cells overexpressing miR-33a, cells transfected with antagomir-33a, cells stably expressing T-shRNA and overexpressing miR-33a, and cells stably expressing T-shRNA plus transfection of antagomir-33a. (A) The cells were under normal culture conditions for 8 hours. The cell apoptosis rate at 8 hours was expressed as fold changes to that of the Saos-2 NC cells (designated as 1). (B) Saos-2 and (C) MG-63 cells were treated with 15 nM of cisplatin for 8 hours. The cell apoptosis rates at 4 hours and 8 hours were shown as the percentage of TUNEL positive cells in total cells.