CHEK1 and neoplasm: CDK5 regulatory subunit-associated protein 3 (CDK5RAP3, also known as C53, LZAP or IC53) is a tumor suppressor that activates p53, induces genotoxic-dependent apoptosis, inhibits the G2/M checkpoint via CHK1 and CDK1, and reduces NF-κB activity, cellular invasion, and tumor growth [16,17,18,19].