Abstract
Studies have established the presence of a small subpopulation of cells
within tumor cells, known as cancer stem cells (CSCs). These cells have
evidently been the reason for metastasis, chemotherapy or radiotherapy
resistance and tumor relapses in several types of cancers. CSCs are
prone to epithelial-to-mesenchymal transition (EMT), resulting in
aggressive tumors. They modulate various pathways of molecular
signaling, including Wnt, Hedgehog and Notch, thus increasing the
stem-like characteristics. Elevated expression of ATP binding cassette
(ABC) transporter efflux pump as well as suppression of apoptosis has
also increased anti-cancer drug resistance. Plants are known to possess
bioactive compounds that can modulate these key regulators and hence
eliminate CSCs. This review aims to report and summarize preclinical
studies about the effects of phytocompounds on CSCs of various tumors.
Furthermore, clinical trials carried out for some of these
phytoconstituents are reported. Thus, selectively targeting CSCs with
plant extracts and herbal preparations may be a promising remedial
strategy for cancer.