title: P21 and p27: roles in carcinogenesis and drug resistance.
abstract: Human cancers arise from an imbalance of cell growth and cell death. Key proteins that govern this balance are those that mediate the cell cycle. Several different molecular effectors have been identified that tightly regulate specific phases of the cell cycle, including cyclins, cyclin-dependent kinases (CDKs) and CDK inhibitors. Notably, loss of expression or function of two G1-checkpoint CDK inhibitors - p21 (CDKN1A) and p27 (CDKN1B) - has been implicated in the genesis or progression of many human malignancies. Additionally, there is a growing body of evidence suggesting that functional loss of p21 or p27 can mediate a drug-resistance phenotype. However, reports in the literature have also suggested p21 and p27 can promote tumours, indicating a paradoxical effect. Here, we review historic and recent studies of these two CDK inhibitors, including their identification, function, importance to carcinogenesis and finally their roles in drug resistance.
authors.affiliation: The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Breast Cancer Research Program, Baltimore, MD, USA.
authors.forename: Abde M
authors.initials: AM
authors.lastname: Abukhdeir
authors.forename: Ben Ho
authors.initials: BH
authors.lastname: Park
mesh_terms: D000818:Animals; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000502:physiology*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000502:physiology*; D019008:Drug Resistance, Neoplasm; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology; D011379:Prognosis
chemical_list: D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004791:Enzyme Inhibitors; D050760:Cyclin-Dependent Kinase Inhibitor p27