Antitumor effect of antibody against a SEREX-defined antigen (UOEH-LC-1) on lung cancer xenotransplanted into severe combined immunodeficiency mice.

We previously reported the humoral immune response of tumor-infiltrating B lymphocytes in a lung cancer patient and 22 genes coding tumor-associated antigens identified using the serological identification of antigens by recombinant expression cloning method. In this study, we investigated one of these genes, designated University of Occupational and Environmental Health-Lung cancer antigen-1 (UOEH-LC-1), which has an extracellular domain. Quantitative reverse transcription-PCR revealed that UOEH-LC-1 was expressed ubiquitously in the normal tissues tested. However, it was overexpressed in 5 of 11 (45.5%) lung cancer cell lines and also in 9 of 15 (60%) lung cancer tissues compared with the paired normal lung tissues. A sequence analysis revealed that UOEH-LC-1 has a transmembrane domain. Flow cytometry analysis using a polyclonal antibody against UOEH-LC-1 revealed positive staining on lung cancer cell lines that were positive for expression of mRNA of UOEH-LC-1. Phage plaque assay showed the specific reactivity of anti-UOEH-LC-1 antibody against UOEH-LC-1 protein derived from the antigen encoding phage. By immunohistochemical staining with the anti-UOEH-LC-1 antibody, 7 of 28 (25.0%) lung cancer specimens showed positive staining on the cell surface. The administration of anti-UOEH-LC-1 antibody inhibited the growth of the UOEH-LC-1-positive tumors that were xenotransplanted into severe combined immunodeficiency mice. Complement-dependent cytotoxicity was one of the mechanisms to suppress the tumor growth. These results suggest that the antibody against UOEH-LC-1 therefore seems to have a promising therapeutic potential as a treatment for lung cancer.