Aberrant signaling pathways in cancer: Modulation by the dietary flavonoid, quercetin

Abstract

Of late, flavonoids, a class of polyphenolic compounds ubiquitously present in the human diet have gained increasing attention in cancer prevention. Defining the anti-cancer mechanisms of quercetin, a major dietary flavonoid has been the topic of intense research over the last two decades. Evidences from experimental studies have shown that quercetin not only offers protection against chemically induced cancers but also suppresses the growth of cancer cells in vitro and in vivo by enhancing carcinogen detoxification and antioxidant defences, inducing cell cycle arrest and apoptosis, inhibiting matrix invasion and angiogenesis, and modulating intracellular signalling circuits. Epidemiological studies across different populations have also indicated that quercetin intake is associated with reduced risk of various cancers. This review summarizes the preclinical and clinical data on the anti-cancer effects of quercetin, the key molecular mechanisms of action, its synergistic interactions, and adverse side effects to warrant further clinical evaluation of quercetin for cancer prevention and therapy.