title: Differentiation-related pathways of 1 alpha,25-dihydroxycholecalciferol metabolism in human colon adenocarcinoma-derived Caco-2 cells: production of 1 alpha,25-dihydroxy-3epi-cholecalciferol.
abstract: We used the human colon adenocarcinoma-derived cell line Caco-2, which spontaneously differentiates in vitro, as a model system to investigate the metabolism of 1 alpha,25-dihydroxycholecalciferol in colon cancer cells. Subconfluent proliferating and confluent differentiating cells were incubated with 1 microM 1 alpha,25-dihydroxycholecalciferol for a period of 24 to 48 h. HPLC analysis of the lipid extract of both cells and media was performed to isolate and identify the various metabolites of 1 alpha,25-dihydroxycholecalciferol. Undifferentiated, highly proliferating Caco-2 cells metabolized 1 alpha, 25-dihydroxycholecalciferol into several side chain modified metabolites formed through the C-24 oxidation pathway. In contrast, no metabolites of the C-24 oxidation pathway were identified in differentiated Caco-2 cells. However, differentiated cells produced significant amounts of a metabolite which was less polar than 1 alpha, 25-dihydroxycholecalciferol on a straight phase HPLC system. This metabolite was identified as 1 alpha,25-dihydroxy-3alpha-cholecalciferol by comigration with a synthetic standard on two different HPLC systems and gas chromatography--mass spectrometry. Thus, we were able to demonstrate that the state of differentiation has a profound influence on 1 alpha,25-dihydroxycholecalciferol metabolism in colon cancer cells.
authors.affiliation: Department of General and Experimental Pathology, University of Vienna Medical School, Austria.
authors.forename: M G
authors.initials: MG
authors.lastname: Bischof
authors.forename: M L
authors.initials: ML
authors.lastname: Siu-Caldera
authors.forename: A
authors.initials: A
authors.lastname: Weiskopf
authors.forename: P
authors.initials: P
authors.lastname: Vouros
authors.forename: H S
authors.initials: HS
authors.lastname: Cross
authors.forename: M
authors.initials: M
authors.lastname: Peterlik
authors.forename: G S
authors.initials: GS
authors.lastname: Reddy
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D001693:Biological Transport, Active; D018938:Caco-2 Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D002117:Calcitriol / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D004100:Dihydroxycholecalciferols / Q000737:chemistry / Q000378:metabolism* / Q000493:pharmacokinetics; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors; D014316:Tritium
chemical_list: D004100:Dihydroxycholecalciferols; D014316:Tritium; D000469:Alkaline Phosphatase; D002117:Calcitriol; D013936:Thymidine