Ursolic acid and quercetin: Promising anticancer phytochemicals with antimetastatic and antiangiogenic potential

Despite available treatments, the incidence of the cancer is increasing and known to be a major cause of mortality worldwide. Plant-derived terpenoids and flavonoids are considered as promising therapeutic molecules, possessing a range of medicinal properties. These phytochemicals have been used as therapeutic agents for the treatment of the various chronic infections. Terpenoids and flavonoids, particularly ursolic acid (UA) and quercetin (Quer), respectively, are emerging as effective antitumor molecules with minimal cytotoxic effects on the normal body tissues. The regulatory role of these molecules in apoptosis, angiogenesis, invasion, or metastasis has been well documented in earlier studies. Angiogenesis and metastasis are the two important hallmarks for the survival of tumor and are responsible for 50% mortality in the cancer patients. Tumor angiogenesis and metastasis have been found to be significantly inhibited in the presence of UA and Quer. Evidence suggested that these phytochemicals inhibit the initiator and progressive cytokines, chemokines, and growth factors such as matrix metalloproteinases involved in extracellular matrix remodeling during tumor metastasis. In addition, the angiogenesis-associated factors such as hypoxia-inducible factor-α and vascular endothelial growth factor/vascular endothelial growth factor receptor have also been downregulated by UA and Quer. In the present review, molecular targets of UA and Quer, in tumor metastasis and angiogenesis, have been summarized.