Abstract
[Background] Small cell lung cancer (SCLC) possesses high tendency to disseminate. However, SCLC patients with paraneoplastic syndrome mediated by immunity against onconeural antigens remain in limited-stage disease (LD) without distant metastases. We previously demonstrated that effector-dominant CD4+ T cell balance was observed only in LD-SCLC but not in extended-stage disease (ED)-SCLC. CD4+ T cell balance in peripheral blood of SCLC patients reflected disease stage and recurrence.
Accumulating evidence suggests that most solid malignancies consist of heterogeneous tumor cells and that a relatively small subpopulation, which shares biological features with stem cells, is responsible for distant metastases and recurrence. We previously reported that DEAD/H (Asp-Glu-Ala-Asp/His) box polypeptide 3, X-linked (DDX3X) is an immunogenic protein preferentially expressed in CD133+ murine melanoma cells exhibiting biological CSC features and that DDX3X-primed CD4+ T cells mediated potent antitumor therapeutic efficacy. We found that DDX3X is strongly expressed in small cell lung cancer (SCLC).
[Objectives] In the current study, we examine that DDX3X-specific effector T cells exist in SCLC patients.
[Patients and Methods] The present study comprised 20 consecutive SCLC patients, 5 long-term survivors, and 10 healthy volunteers from a single institution (Niigata University Medical and Dental Hospital). Specimens were collected after obtaining written informed consent approved by the Niigata University Ethical Committee.
[Results] Six of 12 LD-SCLC patients possessed DDX3X-responsive effector T cells. CD62Llow CD4+ effector T cells obtained from peripheral blood of 5 LD-SCLC secreted significantly more IFNγ upon DDX3X antigen stimulation in the presence of CD11c+ autologous dendritic cells. CD62Llow CD8+ effector T cells from one LD-SCLC patient responded to DDX3X. In contrast, effector T cells obtained from ED-SCLC patients or healthy volunteers never responded to DDX3X.
[Conclusion] DDX3X is likely one of major antigens that is expressed in SCLC and is recognized by T cell immune system. Antitumor immunotherapy to induce effector-dominant CD4+ T-cell immunity on DDX3X antigen may be a promising therapy to eliminate SCLC cells that mediate distant metastases.
Citation Format: Natsue Igarashi, Hiroshi Kagamu, Koichiro Nozaki, Satoshi Shoji, Masaaki Okajima, Satoru Miura, Satoshi Watanabe, Hirohisa Yoshizawa, Ichiei Narita. DDX3X-specific effector T cells in small cell lung cancer patients reflect disease stage. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2554. doi:10.1158/1538-7445.AM2014-2554</jats:p
