Kidney associated antigen 1, also known as KAAG1, is expressed in testis and kidney, and, at lower levels, in urinary bladder and liver. And it is expressed by a high proportion of tumors of various histologic origin, including melanomas, sarcomas and colorectal carcinomas. Recombinant human KAAG1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.