Rumination: Is The Beneficial Effect Of Exercise On Bc Due To The Sun Exposure/vit D?

[Lani]

SINCE MOST OF THE STUDIES CENTERED ON WALKING (AND FEW FEMALES WALK AT NIGHT IN MANY AREAS OF THE US AS IT IS UNSAFE/UNWISE), COULD MOST/ALL OF THE BENEFICIAL EFFECT BE DUE TO THE FACT THAT IT INCREASES EXPOSURE TO SUNSHINE AND HENCE VITAMIN D?

HERE IS THE ARTICLE WHICH MADE ME THINK (AGAIN ABOUT THIS AND POSE IT TO OTHERS):

ABSTRACT: Prohibitin Is a Novel Target Gene of Vitamin D Involved in Its Antiproliferative Action in Breast Cancer Cells [Cancer Research; Subscribe]
Previously, we showed that N-methyl-N-nitrosourea-transformed MCF12F breast epithelial cells exhibited differential expression of several genes, including up-regulation of prohibitin and elevated sensitivity to a relatively noncalcemic vitamin D analogue, 1?-hydroxyvitamin D5 [1?(OH)D5]. In this report, we evaluated the functional significance of prohibitin in relation to the cellular response to vitamin D. The in silico screening for putative transcription factor binding sites identified two vitamin D receptor (VDR)/retinoid X receptor binding sites in the 1-kb promoter region of prohibitin. Prohibitin up-regulation by 1?(OH)D5 treatment at both transcriptional and translational levels was confirmed by real-time reverse transcription-PCR and Western blot analysis in breast cancer cells, identifying prohibitin as a vitamin D target gene. Confocal microscopic analysis showed that prohibitin was localized in the nuclei of MCF-7 cells and a portion of prohibitin was colocalized with VDR, but direct physical interaction between VDR and prohibitin in cell lysates was not detectable. In MCF-7 cells expressing tetracycline-inducible prohibitin (Tet-On model), the overexpression of prohibitin inhibited cell proliferation and enhanced vitamin D-induced antiproliferative activity. Knockdown of prohibitin was accompanied by increased number of cells incorporating bromodeoxyuridine in the whole population and increased cell distribution in the S phase of cell cycle. In addition, prohibitin level had no significant effect on the vitamin D-induced transactivation of CYP24, a VDR target gene. This is the first report to suggest that prohibitin serves as a novel vitamin D target gene, which is involved in the antiproliferative action of vitamin D without affecting CYP24 transactivation in breast cancer cells.