title: Effects of 1,25-dihydroxyvitamin D3 and its analogs on butyrate-induced differentiation of HT-29 human colonic carcinoma cells and on the reversal of the differentiated phenotype.
abstract: 1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) greatly enhances sodium butyrate (NaB)-induced enterocyte differentiation of HT-29 human colonic carcinoma cells while 1,25-(OH)2D3 alone induces growth restriction without associated differentiation. In the present study, the efficacies of various analogs of 1,25-(OH)2D3 to enhance NaB-induced HT-29 differentiation and to prolong the reversal of the differentiated phenotype under NaB-free growth conditions were subsequently examined. Extent of HT-29 differentiation was assessed by measurement of alkaline phosphatase (AP) activity, appearance of mucin-producing cells, changes in morphological characteristics, and expression of differentiation-associated cytokeratin proteins. Among active analogs of 1,25-(OH)2D3, 26,26,26,27,27,27-hexafluoro-1,25-(OH)2D3 (F6-1,25-(OH)2D3), 24,24-difluoro-24-homo-1,25-(OH)2D3, and 26,27-dimethyl-1,25-(OH)2D3 were 100-, 10-, and 5-fold, respectively, more effective than 1,25-(OH)2D3 in enhancing NaB-induced mucin production. Combined use of NaB and F6-1,25-(OH)2D3 (10(-9) M) also induced HT-29 cells to form highly differentiated goblet-like enterocytes, and increased both cellular AP enzymatic activity and tissue-type cytokeratin content. This differentiated state was qualitatively more advanced than that achieved by a combination of NaB and 10(-7) M 1,25-(OH)2D3. NaB-mediated HT-29 differentiation (in short-term inductions) was found to be reversible following a return to NaB-free medium. HT-29 cells differentiated by combined use of NaB and 1,25-(OH)2D3 or its analogs exhibited a significant prolonged reversal time relative to cells differentiated with NaB alone. The most prominent effect was achieved using cells differentiated with NaB and 10(-9) M F6-1,25-(OH)2D3 which exhibited a 7-fold prolonged reversal time over colonocytes differentiated by NaB alone. Our data suggest that a combined use of NaB and 1,25-(OH)2D3 or its derivatives may provide a convenient in vitro model system to probe molecular events associated with steroid-target tissue interactions in a differentiating cell system as commonly occurs in vivo. Such an analysis might lend itself to design of a rational combination differentiation-based therapy for the clinical management of colon cancer.
authors.affiliation: Department of Veterans Affairs Medical Center, Medical Service, Albany, New York.
authors.forename: Y
authors.initials: Y
authors.lastname: Tanaka
authors.forename: K K
authors.initials: KK
authors.lastname: Bush
authors.forename: T
authors.initials: T
authors.lastname: Eguchi
authors.forename: N
authors.initials: N
authors.lastname: Ikekawa
authors.forename: T
authors.initials: T
authors.lastname: Taguchi
authors.forename: Y
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: P J
authors.initials: PJ
authors.lastname: Higgins
mesh_terms: D002087:Butyrates / Q000494:pharmacology*; D020148:Butyric Acid; D002117:Calcitriol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D003110:Colonic Neoplasms; D006801:Humans; D007700:Kinetics; D015394:Molecular Structure; D009077:Mucins / Q000096:biosynthesis; D010641:Phenotype; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000502:physiology*
chemical_list: D002087:Butyrates; D009077:Mucins; D020148:Butyric Acid; D002117:Calcitriol