Identification of antigen related to tumor escape mechanism using cytotoxic T lymphocytes restricted by HLA-B39 that had been deleted in a lung cancer cell line
Authors: Tetsuya So, Mitsuhiro Takenoyama, Takeshi Hanagiri, Makiko Mizukami, Yoshinobu Ichiki, Masakazu Sugaya, Manabu Yasuda, Tsunehiro Oyama, Masaru Morita, Kenji Sugio, Kosei Yasumoto, Takashi Fukuyama, Yoshika Nagata
Journal: Cancer Research (2004)

5454  [Background] Recent progress in tumor immunology makes us enable to identify tumor antigens and to detect tumor-specific immune responses in cancer patients. Immunotherapy using antigenic epitopes recognized by cytotoxic T lymphocyte (CTL) has been performed, and their clinical responses could be detected in a part of cancer patients. However, cancer cells are known to have several mechanisms to escape from the host’s immunological attack. In this study, we focused on the deletion of HLA class I molecules that are essential for the recognition of CTLs, and identified an antigen presented in context with the deleted HLA class I in lung cancer cells. [Methods and results] Totally, 19 tumor cell lines have been established from resected tumor tissues of lung cancer patients. DNA genotyping of HLA class I showed loss of HLA haplotype in 7 out of the 19 cell lines (36.8%). A904L, which was established from the patient A904 with large cell carcinoma possesses HLA-A*2402, -B*0702, -Cw*0702. However, HLA genotypes of autologous EB virus-transformed B cells (A904EBV-B) are HLA-A*2402/2603, -B*0702/3901, and –Cw*0702/0702. Therefore, A904L lost the haplotype of HLA-A*2603, -B*3901, -Cw*0702. To identify the antigens resticted by the lost HLA class I, HLA-A*2603 and HLA-B*3901 cDNA were cloned from A904EBV-B and were stably transfected into autologous tumor cells, and designated as A904L-A26, A904L-B39, respectively. Autologous lymph node lymphocytes were stimulated with A904L-A26 or A904L-B39 independently (A26-MLTC, B39-MLTC). Bulk CTLs against the HLA class I-transfected autologous tumor cells were generated, thereafter CTL clones were obtained by limiting dilution. CTL clone 1 from A26-MLTC lysed A904L-A26 more than A904L, but lyse neither A904EBV-B nor NK-sensitive K562, suggesting that CTL clone 1 may recognize tumor-specific antigen restricted by HLA-A*2603. CTL clone 2 from B39-MLTC showed cytolytic activity against A904L-B39 and A904EBV-B, but did not lyse A904L or K562, suggesting that CTL clone 2 may recognize self-antigen expressed in both tumor cells and normal cells restricted by HLA-B*3901. Using cDNA expression cloning method, a 938 bp cDNA clone was isolated as an antigen-coding gene. We are trying to identify its antigenic epitope. Further we will identify the antigen presented in context with HLA-A*2603. [Discussion] Loss of HLA class I molecules may be one of mechanisms of tumor escape from the immune attack. In this study we showed that CTLs specific for tumor antigens and self-antigens, presented by deleted HLA class I, existed in draining lymph nodes of lung cancer patients. This finding suggests that tumor cells may lose HLA class I by the attacks of these CTLs. Identification of these antigens has a possibility to clarify the tumor escape mechanisms and to lead us perform immunotherapy using key antigens for the tumor rejection.