CDK4 and non-small cell lung carcinoma: Cyclin D1, encoded by CCND1, is a well-documented regulator of the G1/S transition through activating CDK4/6 kinase and subsequently phosphorylating Rb20, that was dramatically reduced at both the protein and mRNA levels in the FXR-knockdown NSCLC cells, while it was increased in ectopic FXR-overexpressing cells.