SMAD2 and colorectal carcinoma: Although HCT116 cells have a truncated mutation of type II TGF-β receptor (TGFR2), SMAD2 protein was phosphorylated in the shKLK6 isogenic clone upon re-expression of the enzymatically active KLK6, because the TGFR2 protein retains its function in this cell line as well as other CRC with microsatellite instability [33].