THY1 and hepatocellular carcinoma: CD90 is a glycosyl phosphatidylinositol-anchored membrane glycoprotein of the immunoglobulin superfamily (Haeryfar et al., 2005), it has been identified as a marker for CSCs such as hepatocellular carcinoma (HCC; Luo et al., 2015), and osteosarcoma (Chen et al., 2015), which are responsible for tumorigenic activity.