(A) GAS5 mRNA expression following transfection with GAS5 siRNA in DLD-1 and SW480 cells compared with transfection with the NC (the efficiency of three siRNAs in DLD-1 cells was 77.06, 72.71, and 72.50% respectively, **P<0.01. The efficiency of three siRNAs in SW480 cells was 76.34, 72.59, and 71.46% respectively, **P<0.01). (B) Flow cytometric analysis of cell-cycle profiles (**P<0.01, compared with NC control). (C) GAS5 knockdown decreased the expression of cleaved PARP and cleaved caspase 3 in DLD-1 and SW480 cells. (D) Flow cytometric analysis of apoptosis. Cells were stained with Annexin/PI. Values were presented as mean ± standard (**P<0.01, compared with NC control).