Anticancer natural medicines: An overview of cell signaling and other targets of anticancer phytochemicals

Therapies of cancer are as diverse as multifaceted the cancer is. Anticancer drugs include, but not limited to synthetic, semisynthetic and natural drugs and monoclonal antibodies. A recent decline in new drug development has led to the rebirth of herbal therapeutics in the form of dietary supplements and botanical preparations. Medicinal plants comprise of complex phytochemicals due to vast biosynthetic capacity. A wide array of phytochemicals has been pharmacologically evaluated for their chemo-preventive and chemotherapeutic potential for several decades. These phytochemicals target cancer at diverse sites such as apoptotic pathways, genetic and epigenetic mutations, damage to deoxyribonucleic acid, production of reactive oxygen species, autophagy, invasion and metastasis of cancer cells, and modulation of cell signaling through Janus-activated kinase/Signal transducer and activator of transcription, Notch, mitogen-activated protein kinase/Extracellular signal-regulated kinase, phosphatidylinositol 3-kinase/Protein kinase B/mammalian target of rapamycin, Nuclear factor kappa B, Wingless-related integration site and Transforming growth factor β pathways. This review focuses on the therapeutic targets of anticancer and chemo-preventive phytochemicals and their mode of action.