LXRs have been shown to diminish the cell cycle regulators, such as the S-phase Kinase-associated protein (SPK2) in cancer cell lines [271], while also inducing the expression of cell cycle inhibitors, such as p21 and p27 (CDK inhibitors) in prostate and ovarian cancer cells, with corresponding lowering levels in phospho-retinoblastoma (pRb) protein [272,273]. The gene discussed is RB1; the disease is cancer.