PROM1 and hepatocellular carcinoma: CD133 (human prominin-1, PROM1) is a glycoprotein with five transmembrane domains and two larger extracellular glycosylation chains that serves as an important surface marker, showing abundant expression in both cytoplasm and nucleus of various tumor tissues, including hepatocellular carcinoma (HCC), brain tumor, pancreatic cancer, prostate cancer, and colon cancer [74,75,76,77,78].