PROM1 and colorectal cancer: At the same time, a relationship between the presence of CD26+ cells, detected by immunohistochemistry in primary CRC tumor biopsies, and the prognosis of metastasis has been demonstrated (Grunt et al., 2015), as well as between the presence of CD26+/CD44+ and EpCAM−/CD133− CTC population, detected in liquid biopsy, and the prognosis of colorectal cancer recurrence (Lieto et al., 2015).