title: Induction of cell cycle arrest and apoptosis in human colon adenocarcinoma cell lines by beta-carotene through down-regulation of cyclin A and Bcl-2 family proteins.
abstract: Although the pharmacological role of beta-carotene in the prevention and treatment of colon cancer has received increasing attention, little is known about the molecular mechanisms of action of this carotenoid. The present study demonstrates that beta-carotene, a natural pigment widely present in fruit and vegetables, inhibits the growth of several human colon adenocarcinoma cell lines (COLO 320 HSR, LS-174, HT-29 and WiDr) by inducing cell cycle arrest in G(2)/M phase and apoptosis. These effects were dose and time dependent and strictly related to cell ability to accumulate the carotenoid. COLO 320 HSR cells incorporated beta-carotene to a greater extent than LS-174, HT-29 and WiDr cells and, concomitantly, they exhibited a higher sensitivity to the growth inhibitory effects of the carotenoid. At inhibitory concentrations beta-carotene reduced the expression of cyclin A, a key regulator of G(2)/M progression. Neither p21 nor p27, two cyclin kinase inhibitors, were significantly modified by carotenoid treatment. With respect to apoptosis induction, decreased levels of the apoptosis blocking proteins Bcl-2 and Bcl-xL were also observed. On the other hand, no changes in expression of the apoptosis promoter protein Bax were detected. This study represents a novel aspect of the biological profile of beta-carotene and a new step in elucidating the underlying molecular mechanisms of its antitumor action. In addition, since cell growth inhibitory effects were reached at beta-carotene concentrations achievable in vivo following its supplementation, this study provides a rational approach for the use of beta-carotene in colon cancer.
authors.affiliation: Institute of General Pathology, Catholic University, 00168 Rome, Italy. ibpg@rm.unicatt.it
authors.forename: Paola
authors.initials: P
authors.lastname: Palozza
authors.forename: Simona
authors.initials: S
authors.lastname: Serini
authors.forename: Nicola
authors.initials: N
authors.lastname: Maggiano
authors.forename: Mara
authors.initials: M
authors.lastname: Angelini
authors.forename: Alma
authors.initials: A
authors.lastname: Boninsegna
authors.forename: Fiorella
authors.initials: F
authors.lastname: Di Nicuolo
authors.forename: Franco O
authors.initials: FO
authors.lastname: Ranelletti
authors.forename: Gabriella
authors.initials: G
authors.lastname: Calviello
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D017209:Apoptosis / Q000187:drug effects*; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors; D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000473:pathology*; D019925:Cyclin A / Q000276:immunology / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D019207:beta Carotene / Q000494:pharmacology*
chemical_list: D018797:Cell Cycle Proteins; D019925:Cyclin A; D019253:Proto-Oncogene Proteins c-bcl-2; D019207:beta Carotene