CD90, a glycoprotein, also known as thymocyte differentiation antigen-1 (Thy-1), is a cell adhesion molecule and the smallest member of the immunoglobulin superfamily.43 CD90+ cells were found to be CSCs in HCC,44 as well as prostate cancer,45 insulinomas,46 OC,47 and could predict the response to sorafenib in patients.48 Co-expression with the additional surface marker, CD44, produced an even more aggressive phenotype, including a higher metastatic and self-renewal capacity, than that of the CD90+CD44− counterparts.49 Here, CD44 is linked to prostate cancer.