Application of anti lung adenocarcinoma monoclonal antibody recognizing cytokeratin-like cytoplasmic antigen for tumor diagnosis.

An anti lung adenocarcinoma murine monoclonal antibody (MoAb), KM195 (IgG1), was generated using mice which underwent tolerance treatment to normal lung tissues. KM195 was selected from among a number of hybridoma clones because of its advantageous reactivity such as high binding to cell membranes of lung adenocarcinoma tissues and low binding to cell membranes of major normal tissues. In a binding assay using cultured cell lines KM195 was found to bind cytoplasmic antigen in many adenocarcinoma cells. Detailed immunohistochemical analysis using paraffin-fixed tissue sections showed that many adenocarcinoma cells such as gastric cancer, colorectal cancer, pancreatic cancer, mammary cancer, ovary cancer and cervical cancer reacted positively with KM195, as well as lung adenocarcinoma cells. KM195 also positively stained a small number of normal cells found in adult and fetal tissues like lung, intestine, pancreas, liver and kidney. Western blot analysis using membrane fraction of lung adenocarcinoma tissues revealed two major KM195-positive bands which were electrophoresed nearby at molecular weights (M.W.) of 40 Kd. The protein corresponding to the two major bands was purified by immuno-affinity chromatography and sequenced. The amino-terminal 19 residues of the lower band was identified as VLEVDPNIQAVXTQEXEQI, which is identical to that of the human cytokeratin 8 (residues 77 to 95), M.W. 52Kd. The amino-terminal sequence of the upper band was blocked and not determined. To examine the ability of KM195 for tumor imaging, 125I-labeled KM195 was injected i.v. into nude mice bearing SW1116 xenografts. Significantly higher radioactivity was observed in the tumor compared with major organs at days 3 and 5. These data indicate that KM195, which recognizes cytokeratin 8-like cytoplasmic antigen, could be a potential MoAb for use in the immunohistochemical diagnosis and radioimmunodetection of adenocarcinoma.