Cyclin K-CDK12 contributes to cancer development by transcriptionally regulating the expression of the oncogene MYC and promoting the cancer signaling pathways, including the noncanonical nuclear factor kappa B (NF-κB) pathway, the canonical Wnt pathway (WNT-β-catenin), and the erythroblastic leukemia viral oncogene/phosphoinositide 3-kinase/protein kinase B (ErbB–PI3K–AKT) pathway. The gene discussed is CDK12; the disease is cancer.