To determine whether the absence of Mertk affects tumor growth or the response to radiation therapy, we established CT26 colorectal carcinoma in wild-type BALB/c or BALB/c Mertk−/− mice and Panc02 pancreatic adenocarcinoma, 3LL lung adenocarcinomas, and B16 melanoma in wild-type C57BL/6 or C57BL/6 Mertk−/− mice. The gene discussed is MERTK; the disease is colorectal carcinoma.