Quercetin-mediated regulation of signal transduction cascades and microRNAs: Natural weapon against cancer

Recent technological and analytical breakthroughs in genomics and proteomics have deepened our understanding related to the multifaceted nature of cancer. Because of therapeutically challenging nature of cancer, there has been a renewed interest in phytochemistry, and much attention is currently being given to the identification of signaling pathway inhibitors. Data obtained through high-throughput technologies has provided a broader landscape of wiring maps of complex oncogenic signaling networks, thus revealing novel therapeutic opportunities. Increasingly, it is being realized that although our knowledge related to physiological and pathophysiological roles of signal transduction cascades has evolved rapidly, the clinical development of signaling pathway inhibitors has been challenging. Quercetin has attracted considerable attention because of its amazingly high pharmacological value. Research over decades has sequentially shown that quercetin effectively inhibited cancer development and progression. In this review, we have attempted to set the spotlight on the regulation of different cell signaling pathways by quercetin. We partition this multicomponent review into how quercetin effectively regulates the Wnt/ß-catenin pathway, Janus kinase-signal transducer and activator of transcription pathway, and vascular endothelial growth factor/vascular endothelial growth factor receptor signaling cascade in different types of cancers. We also provide an overview of the regulation of NOTCH and SHH pathways by quercetin. MicroRNAs (miRNAs) have also emerged as versatile regulators of cancer, and contemporary studies have shed light on the ability of quercetin to control different miRNAs in various cancers. We have scattered information related to NOTCH and SHH pathways, and future studies must converge on the investigation of these pathways to see how quercetin modulates the signaling machinery of these pathways. © 2018 Wiley Periodicals, Inc.