The present application provides novel human genes RNF43 whose expression is markedly elevated in colorectal cancers, as well as CXADRL1 and GCUD1 whose expression is markedly elevated in gastric cancers compared to corresponding non-cancerous tissues. The genes and polypeptides encoded by the genes can be used, for example, in the diagnosis of a cell proliferative disease, and as target molecules for developing drugs against the disease.