Furthermore, we examined the protein levels of cancer stem cell related genes and found that downregulation of USP38 caused significant upregulation of cancer stem cell marker genes SOX2, NANOG, OCT4, BIM1, SNAIL, CD133, ABCG2, and CD44 (Fig. 3f), suggesting that USP38 restrains cancer stem cell population of colorectal cancer cells. This evidence concerns the gene ABCG2 and cancer.