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Abstract B33: Coexpression and frequency of immune checkpoint proteins in the tumor microenvironment analyzed via multiplex immunohistochemistry

Antibody blockade of the PD-1/PD-L1 axis is approved for clinical use in multiple tumor types in an effort to block tumor immune evasion. The high number of emerging cancer immunotherapy agents indicates that there is an increased importance in assessing and understanding the immunosuppressive tumor microenvironment. In this study, we applied a 7-color multiplex immunohistochemistry panel to a lung tumor tissue microarray consisting of FFPE adenocarcinoma and squamous cell carcinoma cores. The panel was composed of immune checkpoint receptors PD-1 and TIM-3; PD-L1, a PD-1 ligand; CD68 and CD8, macrophage and cytotoxic T cell markers, respectively; as well as cytokeratin as the tumor mask and DAPI as the nuclear counterstain. The array included three cores per patient, and the concordance between fields was analyzed. Additionally, the frequency and co-localization of these markers and checkpoint proteins in the tumor and tumor microenvironment were quantified. TIM-3 expression was found not only on CD8+ T cells, but also on CD68+ macrophages, where it is thought to have a distinct function involved in phagocytosis of tumor cells. Furthermore, the significant role that macrophages play in tumor progression via promoting angiogenesis and inhibiting antitumor immunity makes these data increasingly relevant. These data demonstrate how antibody-based multiplex analysis in tissue can provide insight into the various cell types involved in tumor-mediated immune evasion. Multiplex IHC with highly specific antibodies will serve to improve our understanding of how immunotherapies can be used to affect the innate and adaptive branches of the immune system in the course of cancer treatment. Citation Format: Jennifer Ziello, Sarah Klein, Katherine Crosby. Coexpression and frequency of immune checkpoint proteins in the tumor microenvironment analyzed via multiplex immunohistochemistry [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B33.