Effects of rapamycin and CN-A on the expressions of p53, p21Cip1, p27Kip1 and cyclins. Expression of mRNAs was examined by RT-PCR analysis. (a) MCF-7 cells were cultured with 2.5–10 μg/ml CN-A or 1 ng/ml rapamycin, or both combined for 24 hours. (b) MCF-7 cells were cultured with 0.5 ng/ml rapamycin or 10 μg/ml CN-A, or both combined for 12 hours. The levels of GAPDH expression are shown to demonstrate that equal amounts of RNA were used for RT-PCR. CN-A, cotylenin A; GAPDH, glyceraldehyde-3-phosphate dehydrogenase.