CD44 and renal cell carcinoma: An in-depth study of the roles of CD44/CD24 and ALDH1 as cancer stem cell markers in tumorigenesis and metastasis [53,54] showed that the CD44 gene is a major molecular prognostic marker for cancer stem cells (CSCs) of many solid malignancies, including RCC, as well as one of the major components of surviving tubular cells in renal fibrosis [36,53,55,56].