Pien Tze Huang suppresses the stem-like side population in colorectal cancer cells

Accumulating evidence suggests that a small population of cells termed cancer stem cells (CSCs) are crucial in tumor development and drug resistance, leading to cancer relapse and metastasis and eventually the failure of clinical cancer treatment. Therefore, targeting CSCs is a promising approach for anticancer therapies. Due to the drug resistance and adverse effects of currently used chemotherapies, traditional Chinese medicines (TCM) have recently received attention due to the relatively few side-effects. Thus, they have been used as important alternative remedies for various diseases, including cancer. Pien Tze Huang (PZH), a well-known TCM formula that was first prescribed more than 450 years ago in the Ming Dynasty, has been used in China and Southeast Asia for centuries as a folk remedy for various types of cancer. Previously, it was reported that PZH inhibits colon cancer growth via the promotion of cancer cell apoptosis and inhibition of cell proliferation and tumor angiogenesis, which is probably mediated by its regulatory effect on multiple intracellular signaling pathways. To elucidate the mechanism of the tumoricidal activity of PZH, the aim of the present study was to investigate the effect of PZH on CSCs that were isolated as the side population (SP) from the HT-29 colorectal cancer cell line. The results demonstrated that PZH significantly and dose-dependently reduced the percentage of the colorectal cancer stem-like SP cells, decreased the viability and sphere-forming capacity of HT-29 SP cells, indicating that PZH is potent in suppressing the growth of colorectal cancer stem cells. Moreover, PZH treatment in HT-29 SP cells markedly inhibited the mRNA levels of ABCB1 and ABCG2, which are members of the ABC transporter superfamily, thereby contributing to the SP phenotype and multi-drug resistance. Findings of the present study suggest that inhibiting the growth of CSCs is a potential mechanism by which PZH can be used in cancer treatment.