title: Wilms' tumor protein 1: an early target of progestin regulation in T-47D breast cancer cells that modulates proliferation and differentiation.
abstract: Progesterone regulates the proliferation and differentiation of normal mammary epithelium. In breast cancer cells, progesterone and its synthetic analogs, progestins, induce long-term growth inhibition and differentiation. However, the mechanisms responsible are not fully understood. When T-47D breast cancer cells were treated with the synthetic progestin ORG 2058 (16alpha-ethoxy-21-hydroxy-19-norpregn-4-en-3,20-dione), all isoforms of Wilms' tumor protein 1 (Wt1) mRNA and protein were rapidly downregulated. We reasoned that the decrease in Wt1 levels may contribute to the long-term antiproliferative and differentiative effects of progestins as proliferation and differentiation are known end points of Wt1 action. Consistent with this idea, Wt1 small interfering RNA led to a decrease in S phase and cyclin D1 levels, and increased Oil-Red-O staining, indicating increased lipogenesis. Conversely, overexpression of Wt1 attenuated the decrease in S phase induced by ORG 2058 at 48-96 h. This was accompanied by the sustained expression of cyclin D1 despite progestin treatment, and increased levels of retinoblastoma (Rb) phosphorylation at sites targeted by cyclin D1-Cdk4 (Ser249/Thr252). Wt1 overexpression also attenuated the ORG 2058-mediated increase in fatty acid synthase levels and reduced lipogenesis. Thus, Wt1 downregulation was sufficient to mimic the effects of progestin and was necessary for complete progestin-mediated proliferative arrest and subsequent differentiation. Furthermore, Wt1 overexpression modulated the effects of progestins but not anti-estrogens or androgens. These results indicate that Wt1 is an important early target of progestins that regulates both proliferation and differentiation in breast cancer cells.
authors.affiliation: Cancer Research Program, Garvan Institute of Medical Research, Sydney, NSW, Australia.
authors.forename: C E
authors.initials: CE
authors.lastname: Caldon
authors.forename: C S L
authors.initials: CS
authors.lastname: Lee
authors.forename: R L
authors.initials: RL
authors.lastname: Sutherland
authors.forename: E A
authors.initials: EA
authors.lastname: Musgrove
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology*; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D050155:Lipogenesis / Q000235:genetics; D011372:Progestins / Q000502:physiology*; D025721:WT1 Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology
chemical_list: D011372:Progestins; D025721:WT1 Proteins