As tumorigenesis was observed in both ARH1-deficient and heterozygous mice, ARH1 has properties of a tumor-suppressor gene, and cancers follow a two-hit model.32 In agreement, we reported that 6 of 16 lung adenocarcinomas found in ARH1 heterozygous mice had LOH.32 We, therefore, also looked for LOH involving the human ARH1 gene as a potential mechanism for inactivation of ARH1 in human cancers. The gene discussed is LDLRAP1; the disease is lung adenocarcinoma.