P06.05 Endogenous T-cell responses to ten major cancer testis antigens are frequent in esophago-gastric adenocarcinoma and antigen-specific T cells can be expanded using CD40-activated B cells

Background Tumor-associated antigens (TAAs) and especially cancer testis (CTAs) are classical tumor-specific targets for immunotherapies. As TAAs shared between patients, strategies aiming to exploit these scalable potentially applicable across different types of cancer. Loss target other mechanisms immune escape have limited the success CTA-directed immunotherapy. CAR T cells highly effective cellular therapies renewed interest in TAAs. Especially combined targeting multiple appears promising as recently shown lymphoma. In our study, we aimed characterize CTA-expression patterns their impact on endogenous T-cell responses, abundance antigen-presentation esophago-gastric adenocarcinoma (EGA). Materials Methods 41 treatment-naïve EGA patients were included study. RNA tumor patient-matched healthy tissue was isolated used NanoString based expression analysis 26 CTAs 25 genes associated with antigen-presentation. Based CTA expression, 10 peptide pools selected co-cultured peripheral blood mononuclear (PBMCs, n=21) determine anti-tumor responses a FluoroSpot assay. assessed using immunohistochemistry (CD3, CD8) digital image analyses area invasive margin. Autologous CD40 activated B expand antigen-specific CTAs. Results revealed pronounced differences regarding CEP55 MAGEA3/6 showing strong while NY-ESO-1 or MAGEA1 only weakly expressed. 68.3% (28/41) showed ≥ 5/10 analyzed simultaneously. line frequent 75.0% response against at least one most frequently detected Survivin (65.0% 52.6% respectively), 20.0% responded TTK pools. Overall, 6/20 ≥5 We found correlation addition, high Immune-Score increased TAA expression. Finally, demonstrate feasibility TAA-specific expansion potential strategy induce enhance EGA. Conclusions Our study highlights importance The identified relevant immunomonitoring clinical trials Personalized immunotherapeutic EGA-specific even patient specific appear this challenging disease. Disclosure Information M. Thelen: None. Garcia-Marquez: J. Lehmann: D. Keller: E. Preugszat: von Bergwelt-Baildon: B. Research Grant (principal investigator, collaborator consultant pending grants well already received); Modest; Astellas, Roche, MSD. Speakers Bureau/Honoraria (speakers bureau, symposia, expert witness); BMS. F. Consultant/Advisory Board; H.A. Schlößer: Significant; Astra Zeneca.