Cyclin D1 is a crucial regulator of G1 to S phase progression in various cell types. It forms active complexes with cyclin‐dependent kinase 4 and 6 (CDK4/6), promoting cell cycle progression by phosphorylating and inactivating the retinoblastoma protein. Recent studies have revealed its functions as a transcriptional modulator by regulating the activity of several transcription factors and histone deacetylases, providing a new perspective on its role in cancer development and progression [31]. The gene discussed is CCND1; the disease is cancer.