MCF-7 cells were transfected with various CDC2 siRNAs (S1, S2, or S3) or nonsilencing siRNA (NS). After 48 hours, cDNA was prepared using the FastLane Kit. Expression of CDC2 (cell cycle protein) relative to GAPDH (endogenous control) was analyzed by real-time two-step RT-PCR. The relative expression of CDC2 in untreated cells (UT) was set to 100%.