Identification of a surface antigen, common to murine lung and Lewis lung carcinoma, by monoclonal antibody.

Lewis lung carcinoma (3LL) is a spontaneous murine lung carcinoma which preferentially metastasizes into the lung. Monoclonal antibodies (MAb) against 3LL cells were prepared by fusing spleen cells from rats immunized with 3LL and the P3-NSI/I-Ag4 (NSI) plasmacytoma. Two hybridomas were selected which secreted antibodies capable of preferential binding to 3LL cells and not to other malignant cells. Immunohistochemical staining of sections prepared from various mouse organs with one of the MAbs (22.2), revealed exclusive staining of the lung tissue. The data suggest that a lung-specific, 3 LL-associated antigen, is detected by the 22.2 MAb on 3LL cells. The 22.2 antigen is a surface molecule, and is stable following trypsin treatment and fixation by glutaraldehyde or picric acid. Cells that were prepared from a subcutaneous tumor or from lung metastases express high amounts of 22.2 antigen compared to cells of the culture 3LL line (3LLC). Upon reinoculation of 3LLC cells into mice there was a gradual increase in 22.2 antigen expression. It was possible to select from the heterogeneous 3LLC cell population several clones which express high amounts of antigen. These clones differed also in their metastatic patterns. However, the metastatic capacity of these clones did not correlate with expression of the 22.2 antigen. Thus, it appears that expression of the 22.2 antigen is not a necessary condition for formation of lung metastases by 3LL.