Effective Targeting of Colorectal Cancer Stem Cells by Inducing Differentiation Mediated by Low-Dose Vitamin C via β-Catenin Retention in the Cell Membrane

Cancer stem cells (CSCs) are implicated as the underlying cause of tumor recurrence due to their refractoriness to conventional therapies. Targeting CSCs through novel approaches can hinder their survival and proliferation, potentially reducing the challenges associated with tumor relapse. Our previous study demonstrated that colorectal cancer stem cells (CR-CSCs) showed sensitivity to Vitamin C (Vit C), displaying a dose-responsive effect where low doses (2–10 µM) promoted cell proliferation while high doses induced cell death. In this study, we unraveled the mechanistic effects of low doses that, although induced proliferation, remarkably facilitated stemness reduction in HT-29 cell line-derived CR-CSCs. Our findings revealed that Vit C doses of 2 and 6 µM resulted in a reduction in stemness as evidenced by a reduced CD44⁺ cell population, representing CR-CSCs. The key finding was the remarkable increase in the expression of β-catenin protein following low-dose Vit C treatment, despite a reduction in stemness, accompanied by a mesenchymal to epithelial transition (MET). The sequestration of upregulated β-catenin via E-cadherin to the cell membrane was identified as a mechanism for reduced stemness, MET, and differentiation of CR-CSCs. Importantly, the epithelial phenotype induced by low-dose Vit C rendered CR-CSCs sensitive to conventional treatments, enhancing chemosensitivity to Cisplatin, Paclitaxel, and 5-Fluorouracil by 60%–90%. These findings suggest that low dose Vit C could serve as an adjuvant to conventional therapeutic strategies for targeting advanced colorectal cancer by sensitizing CR-CSCs to chemotherapy and potentially reducing tumor recurrence.