CDK1 and neoplasm: Our results showed that the tumor suppressors CDKN1A (also known as Cip1 and p21) and GADD45 were downregulated while various positive cell-cycle regulators and components for DNA replication, including cyclin-B, cyclin-D, CDK1, CDC25B, and MCMs, were upregulated by TSPY-overexpression (Fig. 2c).