Consumption of fruits rich in phenolics are proposed as a dietary strategy to help reduce the risk of developing breast cancer or as complementary treatment against the aggressive breast cancer to increase survival rates (Li et al., 2017). A meta-analysis from 93 studies has pointed out that a healthy dietary pattern is associated with lower cancer risk, especially in postmenopausal, HR⁻ women (Grosso et al., 2017). This is especially relevant when considering that genetic risk factors only account for ∼5–10% of all breast cancer incidences, while exogenous factors including lifestyle and environment are greater contributor to develop breast cancer (Li et al., 2017). Therefore, there is an urgency to find effective diet-derived compounds that are not toxic to non-cancerous cells but with potent anti-tumor activity against even the most aggressive breast cancer subtypes. Their use will help in the fight against breast cancer as alternative and complementary medicine. Studies reviewed by Li et al. (2017) demonstrated the breast cancer inhibitory activities exerted by fruit extracts using in vitro and in vivo xenograft models. For example, strawberry phenolic extracts inhibited T47D breast cancer tumor growth in vitro and in vivo. Bilberry extract inhibited MCF-7 and induced apoptotic cell death. Cranberry extract inhibited MCF-7 cell proliferation, an effect partly attributed to the induction of apoptosis and G1 phase arrest. Edible berries of the Eugenia jambolana Lam plant (also known as Portuguese plum), induced antiproliferative and pro-apoptotic effects on MCF-7 and MDA-MB-231 cells, with low toxicity to the normal MCF-10A cells. Phenolics from peach suppressed breast tumor growth in vitro and in vivo and suppressed lung metastasis in vivo. Extracts from immature plums with high concentrations of phenolics and condensed tannins exhibited high cytotoxic effects against MDA-MB-231 cells accompanied with increased expression of pro-apoptotic markers.

Tart cherries have also been assessed for their anticancer activity. Total phenolics in tart cherry juice inhibited the estrogen receptor positive (ER⁺) MCF-7 breast cancer cells (Martin & Wooden, 2012). The MCF-7 breast cancer cells (luminal A subtype), represents a less aggressive breast cancer with low metastatic potential and better prognosis (Dai et al., 2017). In this study, such activity was attributed to its anthocyanin composition, which was associated with necrosis at high concentrations and apoptosis at physiological relevant concentrations (∼307 nM cyanidin-3-glucoside equivalents).