Một vai diễn đơn giản của nhiễu xuyên âm tiềm năng giữa hormone steroid và yếu tố tăng trưởng tín hiệu đường với khả năng của họ ảnh hưởng đến trang web công nhận AP-1 thông qua hành động | 44 Keith Griffiths et al. Fig. A simple portrayal of the potential crosstalk between steroid hormone and growth factor signalling pathways with their capacity to influence the AP-1 recognition site through Fos-Jun action cer 94 and Boyle 63 64 refers to a 250 000 male cohort 95 in which 90 cases of prostate cancer were identified in African-American men and a similar number in Caucasians. The levels of 1 25-diOH-VitD3 in stored serum from these men were compared to controls matched for age race and for sample storage time. 1 25-diOH-VitD3 in cancer samples was reported to be a significant pg ml lower than controls risk therefore decreases with higher levels of the vitamin. Noteworthy however was that risk was associated only with palpable tumours not incidental cancer suggesting that any influence is confined to the later stages of tumour progression. The skin the only source of vitamin D3 is where 7-dehydrocholesterol is converted by solar UV irradiation to the provitamin D3. Thermal isomerisation of provitamin D3 to vitamin D3 occurs in the epidermis from where it enters the blood. It is hydroxylated at the C-25 position in the liver and then primarily in the kidney but also by keratinocytes hydroxylated to 1 25-diOH-VitD3 the biologically active hormone the biological effects of which are mediated 96 through VDR. Like vitamin A it induces cellular differentiation and restrains proliferation both effects are associated with the repression of the c-myc proto-oncogene 97 and induction of TGF-P expression 98 . VDR is associated with enhanced apoptosis increased expression of Bcl-2 and G1S cell cycle blockade in prostate cancer cell lines. In the USA prostate cancer mortality is inversely proportional to UV-radiation 99 and in Finland vitamin D deficiency similarly relates to UV-radiation and cancer. Levels of plasma 25-OH-VitD3 which have been falling during the past 25 years as prostate cancer incidence has increased are markedly different between men in
