title: Synergistic effect of paclitaxel and 4-hydroxytamoxifen on estrogen receptor-negative colon cancer and lung cancer cell lines.
abstract: Antiestrogen tamoxifen (Tam) is the most prescribed drug for the treatment of estrogen receptor (ER)-positive breast cancers. It is also used in long-term clinical trials with encouraging preliminary results as a chemopreventive agent for breast cancer. The effect of Tam on ER-negative cancers, however, is unclear. Here we reported that paclitaxel and 4-hydroxytamoxifen (4-HT) have a synergistic cytotoxic effect on the ER-negative colon cancer cell line HCT15, which is refractory to paclitaxel alone. Our results showed that 4-HT at submicromolar concentrations effectively enhanced the antiproliferative effect of paclitaxel. In addition, at 1/10 of the paclitaxel concentrations used for HCT15, 4-HT and paclitaxel also showed synergistic effect on NCI H460, an ER-negative lung cancer cell line. For both cell lines, the effective concentration for paclitaxel to inhibit cell growth was 1 log lower in the combination treatment than the concentration used in the single treatment. Cell cycle analysis showed that the combination of paclitaxel and 4-HT increased the G2/M population and resulted in the increase of apoptosis in both cell lines. Enhanced early release of cytochrome c from mitochondria may be the apoptotic pathway activated in the combination treatment in HCT15 cells.
authors.affiliation: Cancer Research, Pharmaceutical Product Research Division, Abbott Laboratories, Abbott Park, IL 60064, USA.
authors.forename: W Z
authors.initials: WZ
authors.lastname: Gu
authors.forename: Z
authors.initials: Z
authors.lastname: Chen
authors.forename: S K
authors.initials: SK
authors.lastname: Tahir
authors.forename: S H
authors.initials: SH
authors.lastname: Rosenberg
authors.forename: S C
authors.initials: SC
authors.lastname: Ng
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D018287:Carcinoma, Large Cell / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D002455:Cell Division / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D003574:Cytochrome c Group / Q000187:drug effects / Q000378:metabolism; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D020847:Estrogen Receptor Modulators / Q000494:pharmacology*; D016195:G2 Phase / Q000187:drug effects; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D008938:Mitosis / Q000187:drug effects; D017239:Paclitaxel / Q000494:pharmacology*; D011960:Receptors, Estrogen / Q000187:drug effects / Q000378:metabolism; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D003574:Cytochrome c Group; D020847:Estrogen Receptor Modulators; D011960:Receptors, Estrogen; D013629:Tamoxifen; C016601:afimoxifene; D017239:Paclitaxel