Neogambogic Acid Suppresses Characteristics of Colorectal Cancer Stem Cells Through Inhibition of Wnt/β-catenin Signaling Pathway

Objective To explore the role of neogambogic acid in the characteristics of colorectal cancer stem cells (CRC-CSCs) through the Wnt/β-catenin signaling pathway.

Methods The colorectal cells SW480 and HCT166 were divided into control group and neogambogic acid groups (1.5, 3, 6, and 12 μmol/L). The viability of CRC-CSCs was determined by MTT method, and spheroid and clone formation assays were used to assess the capacity of spheroid formation and self-renewal ability of the cells. The effects of neogambogic acid on the apoptosis and cell cycle of CRC-CSCs were evaluated by flow cytometry assays. Real-time quantitative PCR was used to detect the mRNA expression levels of relative markers (CD133, CD44, ALDH1, Oct4, and Nanog) of CRC-CSCs, and the protein expression levels of the self-renewal marker (PCNA), apoptosis markers (cleaved caspase-3 and cleaved caspase-9), and Wnt/β-catenin signaling pathway markers (p-GSK3β, GSK3β, β-catenin, and Wnt) were analyzed using Western blot.

Results Compared with the control group, after neogambogic acid treatment, the viability of SW480 and HCT116 cells decreased (P<0.05), the spheroid forming ability and the clone numbers of CRC-CSCs decreased (P<0.001, P<0.01) but the cell apoptosis rate increased (P<0.01), and cell cycle was arrested in G₀/G₁ phase. Moreover, neogambogic acid downregulated the mRNA and protein expression of relative markers of CRC-CSCs (CD133, CD44, ALDH1, Oct4, and Nanog), PCNA, p-GSK3β, β-catenin, and Wnt (P<0.05) and upregulated the expression of cleaved caspase-3, cleaved caspase-9, and GSK3β (P<0.01).

Conclusion Neogambogic can inhibit the stem cell properties of colorectal cells via inhibition of Wnt/β-catenin signaling pathway. As a result, neogambogic acid may be an attractive agent against colorectal cancer.