Evaluation of CD151 as an Antibody Target for Therapy of Non-Small Cell Lung Cancers

Abstract

CD151 is a member of the tetraspanin superfamily of transmembrane proteins and is overexpressed in a variety of cancers. CD151 affects the motility and metastasis of tumor cells, and its expression is closely associated with poor prognosis. Here, we investigated the potential use of CD151 expression as a prognostic marker in human non-small cell lung cancer (NSCLC). We also produced anti-CD151 antibodies as a first step in exploring the potential for CD151 to serve as a target for anticancer therapy. Tissues from 380 patients with NSCLC were collected at Samsung Hospital between 1994 and 2005. Samples were subjected to immunohistochemical staining for CD151 expression and the results were correlated with patient clinicopathological features. High expression of CD151 was significantly associated with worse disease-free survival and overall survival of males, smokers, and patients with adenocarcinoma subtype of NSCLC. CD151 expression was identified as a significant prognostic indicator of NSCLC, suggesting that it may serve as a potential molecular target for therapeutic antibody development. To investigate this possibility, we identified the optimal CD151 epitope for antibody development through structural and functional analyses, produced a recombinant CD151 protein, and isolated single chain variable antibody fragments (scFv) by screening an scFv-expressing phage library against the recombinant protein. Candidate scFv clones were selected after 4 rounds of biopanning and a secondary screening by ELISA analysis. Selected scFvs were cloned and converted to whole IgG, and the antibodies were expressed in CHO-S cells. Four anti-CD151 antibodies were affinity purified and shown by flow cytometry to bind specifically to CD151-positive tumor cell lines. In conclusion, this study demonstrated that CD151 expression is a prognostic marker for NSCLC and identified 4 anti-CD151 antibodies that may be developed as potential therapeutic anticancer antibodies.