title: Additive effects of tamoxifen and the farnesyl transferase inhibitor FTI-277 on inhibition of MCF-7 breast cancer cell-cycle progression.
abstract: The efficacy of tamoxifen in the hormonal therapy of breast cancer is well established, but therapeutic resistance is inevitable. FTIs are a new class of anticancer drugs that are in phase III clinical evaluation. Since the mechanisms of action of these 2 classes of drugs are different, we tested the combination of tamoxifen and FTI-277 on inhibiting proliferation of hormone-dependent MCF-7 human breast cancer cells. An additive effect on cell proliferation was demonstrated, accompanied by an additive G(0)/G(1) arrest. The major effect of the combination of the 2 drugs was to maintain p21(waf/cip1) at an intermediate level, higher than that observed in the presence of tamoxifen alone. This was associated with an additive effect on inactivation of cyclin E-Cdk2 complexes and decreased phosphorylation of pRb and p130 pocket proteins. These effects were accompanied by increased association of 2 CDIs, p27(kip1) and p21(waf/cip1), with cyclin E-Cdk2 complexes. These data demonstrate that the additive effect is likely predominantly due to the recruitment of p27(kip1) and, to a lesser extent, p21(waf/cip1) into the cyclin E-Cdk2 complexes. Together, these results suggest that the combination of FTI and tamoxifen may increase the antitumor effect of either drug alone in breast cancer.
authors.affiliation: Cancer Research Program, Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney, Australia.
authors.forename: Sophie F
authors.initials: SF
authors.lastname: Doisneau-Sixou
authors.forename: Philippe
authors.initials: P
authors.lastname: Cestac
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Faye
authors.forename: Gilles
authors.initials: G
authors.lastname: Favre
authors.forename: Robert L
authors.initials: RL
authors.lastname: Sutherland
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000037:antagonists & inhibitors*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D051231:Farnesyltranstransferase; D016259:Genes, myc; D006801:Humans; D008715:Methionine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D009376:Neoplasms, Hormone-Dependent / Q000378:metabolism / Q000473:pathology*; D013629:Tamoxifen / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; C096856:FTI 277; D013629:Tamoxifen; D008715:Methionine; D019883:Alkyl and Aryl Transferases; D051231:Farnesyltranstransferase