Collectively, when subjects with familial adenomatous polyposis were excluded, the presence of the wild-type allele of polymorphic CYP2A6 apparently led to a reduction in the chemopreventive effects of daily aspirin on the sporadic development of colorectal tumors in nonsmokers (Fig. 1c, d). The gene discussed is CYP2A6; the disease is colorectal neoplasm.