TF and cancer: The O-linked tumor-associated glycans such as the Thomsen-Friedenreich (TF) antigen (Galβ1-3GalNAcα/β-O-Ser/Thr, TF, CD176) and Tn antigen (GalNAcα1-O-Ser/Thr, CD175) are expressed in the majority of human carcinomas [1, 16–18], including cancer-initiating cells [19].