Anti-cancer activity of quercetin via apoptosis induction pathways in human breast cancer cell lines-a systematic review and meta-analysis

A systematic review and meta-analysis were conducted to summarize and review the current literature surrounding quercetin in breast cancer and evaluate its efficacy as an anticancer agent in human breast cancer cell lines. Electronic databases, PUBMED, WEB OF SCIENCE and MEDLINE were systematically searched in December 2020 using the key terms, Quercetin AND Breast cancer AND apoptosis OR cell cycle. Fourteen papers surrounding effects of quercetin on cell viability were obtained. Risk of bias assessment revealed that most papers were reliable. Three meta-analyses were conducted to confirm the efficacy of quercetin at the concentrations of 40-50 µM, 100µM, and >100µM (120- 200 µM). Two subgroup analyses on incubation time and cell type were performed to ascertain whether these factors affect mechanisms of quercetin. Results showed that the decrease in percentage cell viability is directly proportional to increasing concentration. The greatest decrease in cell viability was observed in 100 µM (Risk Ratio (RR) = 0.56; p<0.00001), followed by 100 µM (RR= 0.74) and then 40-50 µM (RR=0.79). However, effects of quercetin may be determined by other factors such as incubation time or a particular cell type signaling cascade. Subgroup analysis revealed that significant differences between 24 and 48 hours were not observed. MCF7 cells showed to be most sensitive to actions of quercetin (p< 0.0001). It was concluded that there is enough information surrounding the cytotoxic effects of quercetin to be progressed forward, however optimal doses that are physiologically relevant and safe in humans should be elucidated.