Analysis of cellular localization of SART3 tumor antigen by a newly established monoclonal antibody: heterotopic expression of SART3 on the surface of B-lineage leukemic cells.

SART3 has been identified as a tumor antigen recognized by cytotoxic T-lymphocytes. Subcellular localization of SART3 is still controversial, although it has been studied extensively. In this study, we established an anti-SART3 monoclonal antibody (mAb) to analyze the subcellular localization of SART3 in tumor specimens. Immunohistochemical analysis demonstrated that SART3 was preferentially expressed in the nucleus of cancer cells. Flow cytometric analysis indicated that SART3 was not expressed on the cell surface of tumor cells, except for B-lineage cells. SART3 was detected on the cell surface of several B-lineage leukemic cells with different maturation stages, but not on normal peripheral blood B cells. These results suggest that heterotopically expressed SART3 is a tumor-associated antigen rather than a differentiation antigen on B-lineage cells.