CDKN1A and hydrops fetalis: To dissect the roles of p21Cip1 and p27Kip1 in the synergistic effect of HF and ATS on cell cycle arrest, we constructed the p21Cip1 knockdown, p27Kip1 knockdown, and p21Cip1-p27Kip1 double knockdown HCT116 cells or MCF-7 cells.