Human tissue distribution of TA02, which is homologous with a new type of aspartic proteinase, napsin A

The N-terminal amino acid sequence of TA02 (molecular weight 35.0 kDa, isoe lectric point 5.29), which is associated with primary lung adenocarcinoma, was determined and a fragment peptide was used to generate mouse monoclonal antibodies (mAbs) against TA02, The amino acid sequence suggested that TA0 2 might be homologous with napsin A, a new type of aspartic proteinase, In this context, we confirmed the expression of napsin A in primary lung adeno carcinoma using reverse-transcription polymerare chain reaction (RT-PCR) an d showed that the TA02 mAbs reacted with glutathione-S-transferase (GST)-na psin A fusion protein. We concluded that TA02 is the same molecule as napsi n A, and showed immunohistochemically that it is distributed mainly in type II pneumocytes, alveolar macrophages, renal tubules and exocrine glands an d ducts in the pancreas. In particular, type TT pneumocytes and alveolar ma crophages showed high expression of TA02 among human normal tissues. In pri mary lung adenocarcinoma, 47 out of 58 (81.0%) primary lesions were positiv e. All well-differentiated adenocarcinomas except those of goblet cell type showed high expression of TA02, In addition, two out of seven (28.6%) larg e cell carcinomas showed low expression of TA02, The other histopathologica l types of primary lung cancer did not express TA02 at all. A few cases of renal cell cancer, pancreatic cancer, breast cancer, thyroid cancer, colon cancer and ovarian cancer showed low expression, but the staining patterns were completely different from that of primary lung adenocarcinoma, which s howed a granular staining pattern. Our novel mAbs should be valuable for im munochemical detection of TA02/napsin A.