title: Inhibition of MCF-7 breast cancer cell proliferation by 5alpha-dihydrotestosterone; a role for p21(Cip1/Waf1).
abstract: Androgens inhibit the growth of breast cancer cells in vitro and in vivo by mechanisms that remain poorly defined. In this study, treatment of asynchronously growing MCF-7 breast cancer cells with the androgen, 5alpha-dihydrotestosterone (DHT), was shown to inhibit cell proliferation and induce moderate increases in the proportion of G1 phase cells. Consistent with targeting the G1-S phase transition, DHT pretreatment of MCF-7 cultures impeded the serum-induced progression of G1-arrested cells into S phase and reduced the kinase activities of cyclin-dependent kinase (Cdk)4 and Cdk2 to less than 50% of controls within 3 days. DHT treatment was associated with greater than twofold increases in the levels of the Cdk inhibitor, p27(Kip1), while p21(Cip1/Waf1) protein levels remained unchanged. During the first 24 h of DHT treatment, levels of Cdk4-associated p21(Cip1/Waf1) and p27(Kip1) were reduced coinciding with decreased levels of Cdk4-associated cyclin D3. In contrast, DHT treatment caused increased accumulation of Cdk2-associated p21(Cip1/Waf1), with no significant alterations in levels of p27(Kip1) bound to Cdk2 complexes. These findings suggest that DHT reverses the Cdk4-mediated titration of p21(Cip1/Waf1) and p27(Kip1) away from Cdk2 complexes, and that the increased association of p21(Cip1/Waf1) with Cdk2 complexes in part mediates the androgen-induced growth inhibition of breast cancer cells.
authors.affiliation: Department of Anatomical Pathology, Royal Perth Hospital, Wellington Street, Perth, Western Australia 6000, Australia.
authors.forename: M A
authors.initials: MA
authors.lastname: Greeve
authors.forename: R K
authors.initials: RK
authors.lastname: Allan
authors.forename: J M
authors.initials: JM
authors.lastname: Harvey
authors.forename: J M
authors.initials: JM
authors.lastname: Bentel
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology*; D042846:CDC2-CDC28 Kinases / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D048430:Cell Shape; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D013196:Dihydrotestosterone / Q000378:metabolism*; D005260:Female; D006801:Humans; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D011944:Receptors, Androgen / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D011518:Proto-Oncogene Proteins; D011944:Receptors, Androgen; D016160:Retinoblastoma Protein; D025521:Tumor Suppressor Proteins; D013196:Dihydrotestosterone; D050760:Cyclin-Dependent Kinase Inhibitor p27; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495900:CDK4 protein, human; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases