SMAD2 and colorectal carcinoma: Hence, we hypothesized that in addition to aneuploidy-based loss of Smad2, Smad4, and Dcc in these five colorectal carcinoma tumors, as all our colorectal carcinoma tumors had two copy loss of the floxed Apc allele, the somatic APC copy loss event may also have affected the three known TSGs.