Abstract 2674: Immune profiling of in NSCLC shows expression of PD-L1 in macrophages is better associated with outcomes than PD-L1 in tumor cells in PD-1 axis immunotherapy treated patients
Authors: Liu Yuting , Zugazagoitia Jon , Henick Brian , Schalper Kurt A. , Rimm David L. 
Published: August 2019

Background: The immune checkpoint target and companion diagnostic, PD-L1 is expressed in both tumor cell and immune cells and both are read by the pathologist and associated with response to therapy in different organ systems. Here, we examine the expression of PD-L1 using molecular assessment of cellular localization to determine which cell type carries the predictive value of the companion diagnostic test.

Methods: We used the quantitative immunofluorescence (QIF) methods (AQUA analysis of images from the PM2000 and inForm analysis of images from the PerkinElmer Vectra and Polaris Automated Quantitative Pathology Imaging System) and measured the expression of PD-L1 in multiple immune cell types by phenotyping each cell. We also acquired high resolution images from the multiplex for precise identification of co-localization using confocal microscopy. The PD-L1 localization was measured using two multiplex QIF panels including CD56 for natural killer (NK) cells, CD68 for macrophages and CD8 for cytotoxic T cells. This multiplex was performed on three retrospective Yale NSCLC cohorts (457 non-immunotherapy-treated cases and 62 PD-1 axis immunotherapy treated cases) represented in tissue microarrays.

Results: PD-L1 localization was significantly higher in macrophages compared to NK cells and CD8 T cells in both tumor and stroma compartment. In stroma, 80% of PD-L1 is expressed by macrophages, while 5% and 3% by NK cells and CD8 T cells, respectively. High CD8 level (top tertile) was associated with better overall survival (P &lt;0.05) predominantly driven by the stroma CD8 (P &lt;0.05), independent of sex, stage, smoking status, and age. Elevated PD-L1 in macrophages was associated with high PD-L1 level in tumor as well as CD8 level and CD68 level (P &lt;0.05). High PD-L1 expression in CD68+ macrophages was correlated better overall survival (OS; P = .0448) while high PD-L1 expression in tumor cells was not.

Conclusion: In over 500 lung cancer cases the predominant immune cell type that expresses PD-L1 CD68 positive macrophages, as compared to NK cells and CD8 T cells. The level of PD-L1 in macrophages is significantly associated with the level of PD-L1 in tumor and with high levels of CD8+ T cells, suggesting a connection between high PD-L1 and “hot” tumors. Similar to our previous findings in melanoma, we find that high levels of PD-L1 in macrophages is a positive predictive biomarker for PD-1 pathway blockade therapy. Due to the small size of the treated cohort in the study, further work is required to confirm this observation.

Citation Format: Yuting Liu, Jon Zugazagoitia, Brian Henick, Kurt A. Schalper, David L. Rimm. Immune profiling of in NSCLC shows expression of PD-L1 in macrophages is better associated with outcomes than PD-L1 in tumor cells in PD-1 axis immunotherapy treated patients [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 2674.