IMMUNOPEROXIDASE STAINING OF TUMORS BY AN ANTIBODY TO XENOPUS PNIXA

pNiXa, a serpin from oocytes and embryos of Xenopus laevis, was tested as a tumor market in human and rodent tissues. A peptide correspondin g to the histidine-rich domain of pNiXa was conjugated and administere d to rabbits to produce a polyclonal antibody, which was purified by a ntigen-affinity and used for immunoperoxidase staining of formalin-fix ed, paraffin-embedded tissue sections. Staining with pNiXa-antibody wa s positive in 23/187 human tumors (12 percent) and negative in 119 spe cimens of normal human tissues. Positive reactions were more frequent in liver (38 percent) and colon (34 percent) tumors than breast (18 pe rcent), prostate (9 percent), mesothelioma (20 percent) or lung (0 per cent) tumors. Staining was negative in human tumors fi-om other sites. Rodent tumors and preneoplastic foci induced by chemical carcinogens were surveyed for staining with pNiXa-antibody. Staining was positive in 10/10 hepatic lesions (hepatocellular foci, adenomas, carcinomas) i nduced in hybrid D2B6F1 mice by diethylnitrosamine and phenobarbital, whereas murine mammary tumors and thyroid, pituitary, renal, and colon tumors of F-344/CNr rats were negative. Thus, immunostaining with pNi Xa-antibody identifies a subset of human and murine tumors; further st udies are needed to determine if reactivity of pNiXa-antibody has diag nostic or prognostic significance.