Quantification of circulating CD105, its ligands TGFβ1 and TGFβ3 and the ligand–receptor complexes revealed elevated levels of CD105, TGFβ3, CD105/TGFβ3 and CD105/TGFβ1 complexes but not TGFβ1 in patients with colorectal cancer. Here, TGFB3 is linked to colorectal cancer.