Importantly, single-cell mRNA sequencing validated that the CTCs displayed an expression profile closely related to Lgr5− cancer cells and did not show enriched expression of other CSC marker genes, such as Prom1 (i.e., CD133), CD44, Aldh1a, and Bmi1 (Figure 3C; Figures S3F and S3G). This evidence concerns the gene CD44 and cancer.