Inhibitory effects of Hedyotis diffusa Willd. on colorectal cancer stem cells

Cancer stem cells (CSCs) are proposed to be closely correlated with the development and progression of tumors, as well as with chemo- and radioresistance. Targeting CSCs may therefore be a promising potential strategy for the treatment of cancer. Currently, natural products have received great interest due to their therapeutic efficacy and reduced adverse effects compared with modern chemotherapeutics. As a significant component of a number of traditional Chinese medicine formulas, the medicinal herb Hedyotis diffusa Willd. (HDW) has long been utilized in China to clinically treat a variety of malignancies, including colorectal cancer (CRC). Previously, the authors of the present study reported that HDW suppressed CRC growth through multiple mechanisms, including promoting apoptosis, and inhibiting cell proliferation and tumor angiogenesis. To additionally investigate its mode of action, the present study isolated a stem-like side population (SP) from colorectal cancer HT-29 cells to investigate the effect of ethanol extract of HDW on CSCs. It was observed that HDW was able to markedly downregulate the expression of CSC marker leucine-rich repeat-containing G-protein coupled receptor 5 and also significantly decrease the proportion of SP in HT-29 cells, in a dose-dependent manner. Furthermore, HDW treatment significantly and dose-dependently inhibited the viability and sphere formation, and induced cell morphological changes of isolated HT-29 SP cells. In addition, HDW greatly suppressed the messenger RNA expression of several critical genes that mediate CSC features, including ATP-binding cassette, sub-family B, member 1, β-catenin, c-Myc, proliferating cell nuclear antigen and survivin. In conclusion, the present study indicates that HDW may exert inhibitory effects on cancer stem cells.