Wnt/β-catenin Signaling Inhibitors suppress the Tumor-initiating properties of a CD44<sup>+</sup>CD133<sup>+</sup> subpopulation of Caco-2 cells
Jung‐Hoon Kim, Kyeng‐Won Choi, Jungwoon Lee, Jae‐Young Lee, Seonock Lee, Ruijing Sun, Jungho Kim
Abstract
Tumor-initiating cells or cancer stem cells are a subset of cancer cells that have tumorigenic potential in human cancer. Although several markers have been proposed to distinguish tumor-initiating cells from colorectal cancer cells, little is known about how this subpopulation contributes to tumorigenesis. Here, we characterized a tumor-initiating cell subpopulation from Caco-2 colorectal cancer cells. Based on the findings that Caco-2 cell subpopulations express different cell surface markers, we were able to discriminate three main fractions, CD44 -CD133 -, CD44 -CD133 + , and CD44 + CD133 + subsets, and characterized their biochemical and tumorigenic properties. Our results show that CD44 + CD133 + cells possessed an unusual capacity to proliferate and could form tumors when transplanted into NSG mice. Additionally, primary tumors grown from CD44 + CD133 + Caco-2 cells contained mixed populations of CD44 + CD133 + and non-CD44 + CD133 + Caco-2 cells, indicating that the full phenotypic heterogeneity of the parental Caco-2 cells was re-created. Notably, only the CD44 + CD133 + subset of Caco-2-derived primary tumors had tumorigenic potential in NSG mice, and the tumor growth of CD44 + CD133 + cells was faster in secondary xenografts than in primary transplants. Gene expression analysis revealed that the Wnt/-catenin pathway was over-activated in CD44 + CD133 + cells, and the growth and tumorigenic potential of this subpopulation were significantly suppressed by small-molecule Wnt/-catenin signaling inhibitors. Our findings suggest that the CD44 + CD133 + subpopulation from Caco-2 cells was highly enriched in tumorigenic cells and will be useful for investigating the mechanisms leading to human colorectal cancer development.