Selective expression and immunogenicity of the cancer/testis antigens SP17, AKAP4 and PTTG1 in non-small cell lung cancer: new candidates for active immunotherapy.

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ABSTRACT BACKGROUND. Lung cancer is the leading cause of cancer deaths in both genders worldwide, with an incidence only second to prostate cancer in men and breast cancer in women. The lethality of the disease highlights the urgent need for innovative therapeutic options. Immunotherapy can afford efficient and specific targeting of tumor cells, improving efficacy and reducing the side effects of current therapies. We have previously reported the aberrant expression of cancer/testis antigens (CTAs) in tumors of unrelated histological origin. In this study we investigated the expression and immunogenicity of the cancer/testis antigens (CTAs) Sperm Protein 17 (SP17), A-kinase anchor protein 4 (AKAP4) and Pituitary Tumor Transforming Gene 1 (PTTG1) in human non-small cell lung cancer (NSCLC) cell lines and primary tumors. METHODS. We used RT-PCR, immunofluorescence, flow cytometry, ELISA and cytotoxicity assays to determine the expression levels and immunogenicity of SP17, AKAP4 and PTTG1 in human NSCLC cell lines and primary tumors. RESULTS. We found that SP17, AKAP4 and PTTG1 are aberrantly expressed in NSCLC cancer cell lines and primary tumor tissues from patients, compared to normal lung cell lines and tissues. We established the immunogenicity of these CTAs by measuring CTA-specific autoantibodies in patients' sera and generating CTA-specific autologous cytotoxic lymphocytes (CTLs) from patients' peripheral blood mononuclear cells (PBMCs). CONCLUSIONS. Our results provide proof of principle that the CTAs SP17/AKAP4/PTTG1 are expressed in both human NSCLC cell lines and primary tumors and can elicit an immunogenic response in NSCLC patients. Based on our findings, further studies are warranted to explore the feasibility of developing CTA-specific immunotherapeutic strategies for NSCLC patients.