TGFB1 and rectal neoplasm: With respect to tumor site, the mutation prevalence for the RTK/RAS, IGF2/PI-3-kinase, and TGF-beta (TGFB1) pathways was significantly lower in distal colon and rectal tumors than in proximal colon tumors, whereas the prevalence of TP53/ATM set mutations was significantly greater in distal colon and rectal tumors (Fig. 1c, Supplementary Table S6).