It was shown that MCL1 and cell cycle progression are interconnected and more MCL1 expression accelerated the cancer cell cycle progression.30, 31 Here, we found that MCL1 knockdown led to a G1 cell cycle arrest by decreasing CYCLIN D1, CDK4/6 and by increasing P27 expression.30, 31 Enforced survival led to increased CDK4 expression and pRB phosphorylation. This evidence concerns the gene CCND1 and cancer.