TKTL1 and cancer: Transketolase-like 1 (TKTL1) has gained increased attention due to several studies showing a TKTL1-positive staining of malignant tumor tissue of different origins [15, 16, 20, 22–24, 35, 40, 41, 43, 51] and its subsequent designation as a “proto-oncogene” [9].