CCND1 and cancer: However, we found that c-MYC S405A cancer cells had lower c-MYC, cyclin D1, and CDK4 expression than c-MYC WT cancer cells, while c-MYC S405E cancer cells had higher c-MYC, cyclin D1, and CDK4 expression than c-MYC WT cancer cells (Fig. 6A).