title: Molecular pathways involved in the antineoplastic effects of calcitriol on insulinoma cells.
abstract: We have previously reported that in tumorigenic pancreatic beta-cells, calcitriol exerts a potent antitumorigenic effect by inducing apoptosis, cell growth inhibition, and reduction of solid beta-cell tumors. Here we have studied the molecular pathways involved in the antineoplastic activity of calcitriol on mouse insulinoma beta TC(3) cells, mouse insulinoma beta TC expressing or not expressing the oncogene p53, and beta TC-tet cells overexpressing or not the antiapoptotic gene Bcl2. Our results indicate that calcitriol-induced apoptosis was dependent on the function of p53 and was associated with a biphasic increase in protein levels of transcription factor nuclear factor-kappa B. Calcitriol decreased cell viability by about 40% in p53-retaining beta TC and in beta TC(3) cells; in contrast, beta TC p53(-/-) cells were only minimally affected. Calcitriol-induced cell death was regulated by members of the Bcl-2 family of apoptosis regulatory proteins, as shown by calcitriol-induced up-regulation of proapoptotic Bax and Bak and the lack of calcitriol-induced cytotoxicity in Bcl-2-overexpressing insulinoma cells. Moreover, calcitriol-mediated arrest of beta TC(3) cells in the G(1) phase of the cell cycle was associated with the abnormal expression of p21 and G(2)/M-specific cyclin B2 genes and involved the DNA damage-inducible factor GADD45. Finally, in beta TC(3) cells, calcitriol modulated the expression of IGF-I and IGF-II genes. In conclusion, these findings contribute to the understanding of the antitumorigenic effects of calcitriol on tumorigenic pancreatic beta-cells and further support the rationale of its utilization in the treatment of patients with malignant insulinomas.
authors.affiliation: Division of General Medicine, Unit of Endocrinology and Metabolic Disease, San Raffaele Scientific Institute, 20132 Milan, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Galbiati
authors.forename: Luca
authors.initials: L
authors.lastname: Polastri
authors.forename: Bernard
authors.initials: B
authors.lastname: Thorens
authors.forename: Philippe
authors.initials: P
authors.lastname: Dupraz
authors.forename: Paolo
authors.initials: P
authors.lastname: Fiorina
authors.forename: Ugo
authors.initials: U
authors.lastname: Cavallaro
authors.forename: Gerhard
authors.initials: G
authors.lastname: Christofori
authors.forename: Alberto M
authors.initials: AM
authors.lastname: Davalli
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002117:Calcitriol / Q000494:pharmacology*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004351:Drug Resistance; D015870:Gene Expression / Q000187:drug effects; D020672:I-kappa B Proteins / Q000378:metabolism; D007340:Insulinoma / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D010766:Phosphorylation; D011392:Proline / Q000031:analogs & derivatives* / Q000494:pharmacology; D011506:Proteins / Q000235:genetics; D013859:Thiocarbamates / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000378:metabolism; D000097642:GADD45 Proteins
chemical_list: D000970:Antineoplastic Agents; D002117:Calcitriol; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D020672:I-kappa B Proteins; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D011392:Proline; D011506:Proteins; D013859:Thiocarbamates; D016159:Tumor Suppressor Protein p53; D000097642:GADD45 Proteins; C493957:Cdkn1a protein, mouse; C066229:prolinedithiocarbamate