title: Synergistic effect of a retinoid X receptor-selective ligand bexarotene (LGD1069, Targretin) and paclitaxel (Taxol) in mammary carcinoma.
abstract: We have previously shown that the retinoid X receptor (RXR) ligand bexarotene (LGD1069, Targretin) is efficacious as a chemopreventive and chemotherapeutic agent in rat N-nitroso-N-methylurea (NMU)-induced mammary carcinomas (Cancer Res 58: 479-484, 1998). To determine additional role for bexarotene in breast cancer treatment, we evaluated the effect of bexarotene on the efficacy of paclitaxel (Taxol) treatment in a rat NMU-derived mammary tumor cell line, NMU-417, in vitro and in rat NMU-induced mammary tumors in vivo. Our growth inhibition results showed that the bexarotene/paclitaxel combination produced a concentration-dependent synergy in NMU-417 tumor cell line. Synergistic growth inhibition by the combination was associated with an increase in cell death induced by both agents. In rat NMU-induced mammary tumor model in vivo, the benefit of combination therapy was observed as early as 1 week after treatment and increased as treatment continued. At the end of 6 weeks of treatment, the bexarotene/paclitaxel combination produced an overall objective response rate of 94% compared with a rate of 12% in paclitaxel-treated and 58% in bexarotene-treated animals, an effect that was more than the additive effects produced by single agents. Although both bexarotene alone and the bexarotene/paclitaxel combination reduced tumor multiplicity to similar extent, the combination regimen produced a statistically significant decrease in total tumor burden compared to single agents and untreated controls (two-tailed, p < 0.05). Combination therapy did not further alter body weight nor increase toxicity when compared to single agents. In summary, our results demonstrated the potential of using a RXR selective ligand in combination with chemotherapy for the treatment of breast cancer.
authors.affiliation: Department of Molecular Oncology, Ligand Pharmaceuticals Inc., San Diego, CA 92121, USA.
authors.forename: Wan-Ching
authors.initials: WC
authors.lastname: Yen
authors.forename: Rene Y
authors.initials: RY
authors.lastname: Prudente
authors.forename: William W
authors.initials: WW
authors.lastname: Lamph
mesh_terms: D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D000077610:Bexarotene; D016923:Cell Death; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy*; D017239:Paclitaxel / Q000494:pharmacology*; D051381:Rats; D013764:Tetrahydronaphthalenes / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D016588:Anticarcinogenic Agents; D000972:Antineoplastic Agents, Phytogenic; D013764:Tetrahydronaphthalenes; D000077610:Bexarotene; D017239:Paclitaxel