In vito cellular effects of ID3 knockdown by siRNA in D283 cells. (A) Cellular viability was assessed using CCK assays. There was a significant reduction of cell viability (B) Cell proliferation was significantly decreased, assessed using BrdU assays. (C) Apoptosis was assessed using TUNEL staining (40×). (D) Quantification of TUNEL-positive cells revealed a significant increase of apoptosis after siRNA treatment. (E) There was no difference in senescence, assessed using β-gal staining. (F and G) Cell cycle analysis using FACS showed that G2 phase and sub-G1 fractions were increased after siRNA treatment. Migratory ability was assessed using transwell migration assays. (H) Representative field images (100×) and (I) the quantification of migrated cells revealed suppression of cell migration by ID3-siRNA. Error bars represent standard deviations.