Immunohistochemical staining of tumor tissue demonstrated that tumors derived from HEY PGCCs were positive for cathepsin B in the cytosol, whereas most tumor cells generated by injection of control HEY cells were positive for cathepsin B in the nucleus (Figure 5B), suggesting that formation of PGCCs may involve changes in the subcellular localization of these proteins. This evidence concerns the gene CTSB and neoplasm.