Erc has been identified as a gene showing stronger expression in cancer-affected renal tissue than in normal renal tissue in Eker rats (a rat model of renal cancer). The human homologue of the protein encoded by this gene is called MPF (megakaryocyte potentiating factor) or mesothelin. This protein is detected especially prominently in mesothelial cells, and its involvement has been suggested in the development of mesothelioma, making it a promising tumor marker. In humans, involvement of this protein has also been suggested in the development of pancreatic, ovarian and pulmonary cancers, etc. The protein is expressed as a GPI anchor-type membranous protein (about 71 kDa in molecular weight), which is thought to be digested by a furin-like protease to yield fragments about 31 kDa of N-terminal side and about 40 kDa of C-terminal side. We think it is helpful for research of ERC/Mesothelin protein and have characterized the 31 kDa fragment as N-ERC/Mesothelin and the 40 kDa fragment as C-ERC/Mesothelin. This antibody is recognizes mouse C-ERC/Mesothelin.