Pterostilbene and tamoxifen show an additive effect against breast cancer in vitro

BackgroundTamoxifen is widely used for the treatment of breast cancer. Pterostilbene, a bioavailable stilbenoid found in blueberries, has been found to inhibit breast cancer growth in vitro. It was hypothesized that combining pterostilbene with tamoxifen would produce additive effects on estrogen receptor–positive breast cancer cells.MethodsTwo estrogen receptor–positive breast cancer cell lines, MCF7 and ZR-751, were pretreated with graduated doses of pterostilbene for 24 hours, followed by 5 μmol/L tamoxifen. MTT proliferation assays and Cell Death Detection ELISAPLUS tests evaluated cell viability and apoptosis.ResultsMCF7 cells showed inhibition (10 and 20 μmol/L, P < .001; 30 μmol/L, P < .05) at all time points when combined with tamoxifen. ZR-751 cells showed additive reductions in cell viability (P < .001). Cell Death Detection ELISAPLUS indicated increased apoptosis (P < .01).ConclusionsPterostilbene shows an additive inhibitory effect on breast cancer cells when combined with tamoxifen, most likely from augmented cancer cell apoptosis.