These results suggest that a subset (approximately 21%) of human lung adenocarcinoma and squamous cell carcinoma tissues express an antigen that cross-reacts with the JSRV Env-specific monoclonal antibody and that in the case of adenocarcinoma, increased staining intensity correlates with more advanced stage cancer, whereas decreased staining intensity correlates with more advanced stage cancer in the case of squamous cell carcinoma. This evidence concerns the gene ERVW-1 and cancer.