title: Vitamin D3 suppresses the androgen-stimulated growth of mouse mammary carcinoma SC-3 cells by transcriptional repression of fibroblast growth factor 8.
abstract: Active metabolites of vitamin A and D are well known to act as growth inhibitors in hormone-related prostate and breast cancers. When various concentrations of 1alpha,25-dihydroxyvitamin D3 (vitamin D3), all-trans-retinoic acid (ATRA) and 9-cis retinoic acid (9-cis RA) were examined, the androgen-stimulated growth of mouse mammary carcinoma SC-3 cells was inhibited by vitamin D3 alone in a dose-dependent manner. A flow cytometer analysis showed that vitamin D3 leads SC-3 cells to relative G1-growth arrest after 72 h. Characterization of vitamin D3-responsive genes using an oligonucleotide microarray demonstrated that 220 genes were upregulated at more than threefold, and 84 genes were downregulated to less than one-third, compared with the testosterone-stimulated SC-3 cells. Neither cyclin-dependent kinase inhibitors (CDKIs) nor the antiapoptotic bcl-2 gene were induced in vitamin D3-responsive genes, with the exception of a slight induction of p15(INK4B). Importantly, fgf8 was markedly repressed in response to vitamin D3. The exogenous addition of FGF8 canceled the growth suppression by vitamin D3 in SC-3 cells, suggesting that the repression of fgf8 is an indispensable step in vitamin D3-mediated growth inhibition. In reporter assays using the ARE-containing artificial construct and the natural androgen-regulated PSA promoter, co-transfection of the vitamin D receptor (VDR) and androgen receptor (AR) suppressed AR-stimulated promoter activity. In addition, vitamin D3 also suppressed androgen-stimulated promoter activity in the stably transfected SC-3 cells. Moreover, VDR repressed the core promoter activity of fgf8 in COS1 cells and in the SC-3 cells. All these findings strongly suggest that vitamin D3 serves as a negative regulator for both androgen-related and fgf8 transcriptions.
authors.affiliation: Department of Pathology, Jichi Medical University, Shimotsuke, Tochigi, Japan.
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Kawata
authors.forename: Tomoko
authors.initials: T
authors.lastname: Kamiakito
authors.forename: Norio
authors.initials: N
authors.lastname: Takayashiki
authors.forename: Akira
authors.initials: A
authors.lastname: Tanaka
mesh_terms: D000728:Androgens / Q000494:pharmacology*; D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002522:Chlorocebus aethiops; D002762:Cholecalciferol / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects; D051524:Fibroblast Growth Factor 8 / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D008321:Mammary Glands, Animal / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D014158:Transcription, Genetic / Q000235:genetics; D014212:Tretinoin / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D000728:Androgens; D051524:Fibroblast Growth Factor 8; D002762:Cholecalciferol; D014212:Tretinoin