Repurposing dihydroartemisinin as a novel anticancer agent against colorectal cancer stem cells.

Colorectal cancer (CRC) is one of the leading causes of cancer-related death globally and discovering novel therapeutic agents to treat the disease, and prevent cancer metastasis and recurrence is an urgent medical need. Cancer stem cells (CSCs) capable of self-renewal and differentiation are generally considered the cause of tumor metastasis, recurrence and chemoresistance. Hence, targeting CSCs may be a promising strategy for the treatment of cancer. GATA6, a zinc finger transcription factor, contributes to tumorigenesis in CRC and is related to cancer stemness. GATA6-overexpressing stable clones OE4 and OE6 derived from HCT116 cells were previously established and exhibited increased stemness properties. In this study, we found that OE4 and OE6 cells displayed CSC-like properties, including higher expression levels of stemness-related proteins, increased sphere forming capacity and resistance to 5-fluorouracil. OE4 and OE6 cells also showed increased glucose uptake capacity, another hallmark of CSCs. Therefore, these two cell clones were employed as a CSC-like cell model to search for potential colorectal CSC-targeting drugs. Among several compounds tested, dihydroartemisinin (DHA), an antimalarial drug, exerted better anticancer activity toward OE4 and OE6 relative to the empty vector-transfected HCT116 cells. DHA also inhibited sphere formation and impaired glucose metabolism. DHA induced G0/G1 arrest and apoptosis. Moreover, DHA also induced reactive oxygen species and mitochondrial membrane potential loss. Thus, DHA caused mitochondrial damage which was confirmed by Seahorse mitochondrial stress test. DHA also increased LC3B-II and PINK1 protein levels, indicative of autophagy/mitophagy. In conclusion, repurposing DHA may be a potential strategy against colorectal CSCs and further validation using in vivo models is warranted.