title: Melatonin augments the sensitivity of MCF-7 human breast cancer cells to tamoxifen in vitro.
abstract: Cultured MCF-7 human breast cancer cells were pre-exposed to either melatonin (232 ng/mL) or vehicle for 24 hrs prior to being washed and then re-exposed to either ethanol-vehicle or varying concentrations of tamoxifen (37.1 ng/mL, 3.71 micrograms/mL, 371 micrograms/mL) or melatonin (2.32 pg/mL, 232 ng/mL, 23.2 ng/mL) for 5 additional days. Only 371 ng/mL tamoxifen caused a 38% growth inhibition of cells pre-exposed to vehicle whereas all concentrations of tamoxifen inhibited the growth of melatonin pre-exposed cells by 28% to 61% in a dose-dependent manner. Melatonin pre-exposure, potentiated the inhibitory effect of only 232 ng/mL melatonin. Comparison of IC50 values indicate that tamoxifen is approximately a 100 times more potent inhibitor of breast cancer cell growth following the pretreatment of cells with a physiological concentration of melatonin. These results indicate that melatonin has the capability to augment the inhibitory actions of tamoxifen, and to a lesser extent itself, on human breast cancer cell growth.
authors.affiliation: Mary Imogene Bassett Hospital, Research Institute, Cooperstown, New York 13326-1394.
authors.forename: S T
authors.initials: ST
authors.lastname: Wilson
authors.forename: D E
authors.initials: DE
authors.lastname: Blask
authors.forename: A M
authors.initials: AM
authors.lastname: Lemus-Wilson
mesh_terms: D001943:Breast Neoplasms / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects; D004357:Drug Synergism; D006801:Humans; D008550:Melatonin / Q000494:pharmacology*; D013629:Tamoxifen / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D013629:Tamoxifen; D008550:Melatonin