To investigate the effect of CDDP on cell cycle progression, we treated APL cells with different concentrations of CDDP and analysed the expression levels of several proteins including p53, p21, cyclins (cyclin D1), and cyclin‐dependent kinases (CDK 4 and CDK6s) by using the SDS‐polyacrylamide gel electrophoresis technique. This evidence concerns the gene CCND1 and acute promyelocytic leukemia.