IMMUNODETECTION OF SQUAMOUS-CELL CARCINOMA-ASSOCIATED VARIANT OF NUCLEAR-PROTEIN

A new monoclonal antibody, MAb C63.3, was developed by immunizing mice with the high molecular weight fraction of the cytoplasmic proteins f rom the cervical squamous cell carcinoma. In Western blotting, MAb C63 .3 reacted with cytoplasmic and chromatin antigens expressed by cervic al and vulvar squamous cell carcinomas and much weaker with normal cer vical tissue and skin cells. Different molecular variants of C63.3 chr omatin antigens were found in normal tissues (heavy variants, M(r)65,0 00 and 59,000) compared to squamous cell carcinomas (light variant, M( r) 48,000). Diagnostic value of the cancer-associated M(r) 48,000 anti gen is discussed. MAb C63.3 was internalized by cells and bound to the chromatin which suggests that antigen(s) C63.3 might represent a rece ptor for a yet unknown ligand (growth factor). It is suggested that th e high molecular weight C63.3 antigens play a role in maintaining the nonmalignant phenotype. (C) 1996 Academic Press, Inc.