Earlier, using adenomatous polyposis coli gene (Apc)-mutant mouse models of gastrointestinal (GI) tumorigenesis (ApcMin/+ and Apc1638N/+ mice), we have reported a higher RBE for intestinal tumorigenesis, and higher incidence of carcinoma after HZE and simulated GCR exposure, relative to low-LET radiation [4,5,6,7]. The gene discussed is APC; the disease is carcinoma.