We then examined the sensitivity of Polk−/− mice to mutagenicity and carcinogenicity of benzo[a]pyrene (BP) via intragenic gavage, followed by treatment with dextran sulfate sodium (DSS), and compared the mutant frequencies (MFs) and tumor formation in the colon with those of gpt delta mice (hereafter, we refer to the mice simply Polk+/+ mice). The gene discussed is POLK; the disease is neoplasm.