title: The Vitamin D endocrine system of the gut--its possible role in colorectal cancer prevention.
abstract: While Vitamin D insufficiency in the US and European population is rising, epidemiological studies suggest an inverse correlation between low serum levels of 25-hydroxyvitamin D(3) (25-OH-D(3)) and colorectal cancer incidence. The antimitotic, prodifferentiating and proapoptotic active metabolite 1alpha,25-dihydroxyvitamin D(3) (1,25-(OH)(2)-D(3)) is synthesized also by colonocytes, since these possess Vitamin D synthesizing (CYP27B1) and catabolic (CYP24) hydroxylases similar to the kidney. Early during colon tumor progression, expression of CYP27B1 and of the Vitamin D receptor increases, suggesting an autocrine/paracrine growth control in colon tissue as a physiological restriction against tumor progression. However, in human adenocarcinomas expression of the catabolic CYP24 is also enhanced when compared with adjacent normal mucosa. Therefore, to maintain colonic accumulation of 1,25-(OH)(2)-D(3) its catabolism needs to be restricted. Our studies in mice show that low nutritional calcium causes hyperproliferation of colon crypts and significant elevation of CYP24 expression, which can be completely abrogated by soy feeding. We suggest that phytoestrogens in soy, known to be estrogen receptor modulators, are responsible for decreased CYP24 expression. These results and our observation that 17beta-estradiol can elevate CYP27B1 expression in rectal tissue of postmenopausal women, may underlie the observed protective effect of estrogens against colorectal cancer in females.
authors.affiliation: Department of Pathophysiology, Center of Physiology and Pathophysiology, Medical University of Vienna, A-1090 Vienna, Waehringer Guertel 18-20, Austria. heide.cross@meduniwien.ac.at
authors.forename: Heide S
authors.initials: HS
authors.lastname: Cross
authors.forename: Giovanna
authors.initials: G
authors.lastname: Bises
authors.forename: Daniel
authors.initials: D
authors.lastname: Lechner
authors.forename: Teresa
authors.initials: T
authors.lastname: Manhardt
authors.forename: Enikö
authors.initials: E
authors.lastname: Kállay
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000008:administration & dosage / Q000494:pharmacology; D045744:Cell Line, Tumor; D002851:Chromatography, High Pressure Liquid; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000517:prevention & control*; D004703:Endocrine System / Q000378:metabolism*; D041981:Gastrointestinal Tract / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000378:metabolism; D013250:Steroid Hydroxylases / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000378:metabolism; D065668:Vitamin D3 24-Hydroxylase
chemical_list: D012333:RNA, Messenger; D018167:Receptors, Calcitriol; C118756:dihydroxy-vitamin D3; D014807:Vitamin D; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; D002118:Calcium