EXPRESSION OF MATU-MN PROTEIN IN HUMAN TUMOR CULTURES AND IN CLINICALSPECIMENS

MaTu is a novel agent which may be of relevance in human oncogenesis, and has 2 components. One of them, the exogenous MX (coding for protei n p58X), is transmissible to human fibroblasts, to HeLa and to HeLa x fibroblast (H/F) hybrids. The other component, MN, is a cellular gene. Its product, the protein p54/58N, is inducible by infecting HeLa cell s with MX or by growing them in dense cultures. This p54/58N appears t o be a tumor-associated antigen: it is expressed in HeLa and in tumori genic cells (H/F-T), but not in fibroblasts or in non-tumorigenic hybr id cells (H/F-N). Proteins related to p54/58N were also found on immun oblots prepared from human carcinomas of ovary, endometrium and uterin e cervix, but not from normal tissues from corresponding organs or fro m placenta. Using genetically engineered MN protein, we developed a ra dioimmunoassay for MN-specific antibodies, and for quantitative determ ination of MN proteins in cell extracts. In HeLa cells infected with M X we observed conspicuous ultrastructural alterations: formation of ab undant filaments on the cell surface and amplification of mitochondria . Using immunogold-staining, we visualized the p54/58N on the surface microvilli and in the nucleus, particularly in nucleoli.