SMAD3 and inflammatory bowel disease: In order to determine if heterozygosity for SMAD3 confers susceptibility of mice to DSS-induced colitis and tumors, Smad3+/− and WT mice were also included in the study shown in Figure 2 and were exposed to 1.5%, 3% and repeated DSS cycles (Figure S2). Severity of DSS-induced IBD was not significantly different between Smad3+/− and WT mice regardless of DSS concentration and single or repeated administration (Figure S2A).