Abstract 4958: Alterations in the immune microenvironment during progression from Barrett's esophagus to esophageal adenocarcinoma

The incidence of esophageal adenocarcinoma (EAC) has increased 500 fold over the past 30 years and is now a top ten leading cause of cancer death. Systemic chemotherapy and targeted radiation have led to modest increases in survival, however 5-year survival is still less than 20%. Immunotherapy has emerged as a promising approach for the treatment of various solid tumors, however very little is known about the EAC tumor immune microenvironment and how it changes during the progression from Barrett’s metaplasia to carcinoma. The goal of the current study was to identify key changes in the immune microenvironment during progression from Barrett’s Esophagus (BE) metaplasia to the formation of EAC. Tissue samples from 52 patients with various levels of dysplasia (BE, BE w/ low grade dysplasia, BE w/ high grade dysplasia, and EAC) were subject to RNA-Seq analysis and investigated for changes in gene expression of a variety of cytokines and chemokines. Gene expression analysis revealed more than 5-fold increases in expression of multiple cytokines, such as IL8, IL6, CXCR1, and CXCR2, which have been implicated in both immunosuppression and tumor survival. Increases in the expression of immune checkpoint markers, such as PD-L1, TIGIT and CTLA4, were also seen suggesting a worsening immunosuppressive microenvironment during progression from BE to EAC. To further investigate specific changes in the infiltration of CD8 T-cell and T-regulatory cell populations during EAC progression, we performed standard immunohistochemical staining on tissue microarrays from 122 direct-to-surgery EAC patients. Staining for T-cell markers CD3, CD4, CD8, and FoxP3 revealed that only CD8 positive T-cells were increased around tumor cells during progression. Further characterization of individual immune cells was performed through multiplex immunohistochemistry, allowing for the evaluation of multiple immune cell markers within the same tissue section. Multiplex staining for surface expressed markers (CD3, CD8, FoxP3, PD-L1, PanCK, CD163, DAPI), allowed for the quantification and localization of a variety of immune cell types within the EAC microenvironment. In general, the immune cell populations (T-regs, CD8 T cells, and macrophages) increase during progression from BE to BE w/ High Grade Dysplasia. In contrast, EAC tumor sections were relatively immune poor, indicating that the immune microenvironment may often be compromised in cancer. These data collectively demonstrate the EAC microenvironment is characterized by poor infiltration of cytotoxic effector cells, increased expression of immune inhibitory signals from T-regs, inhibitory immune checkpoints and cytokines such as IL-8 and IL-6. These findings suggest an immune suppressive microenvironment which highlights the need for further studies to explore the potential of immune modulating therapy in EAC. Citation Format: Dyke P. McEwen, Derek J. Nancarrow, Jules Lin, Rishindra M. Reddy, Andrew C. Chang, David G. Beer, Kiran H. Lagisetty. Alterations in the immune microenvironment during progression from Barrett9s esophagus to esophageal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4958.