Abstract 2796: Pan-cancer characterization of tumor immune microenvironment

Abstract Background: Anti-PD1/PDL1 therapy has been established as standard care in multiple tumor types, however, many patients will not benefit from this treatment as lack of infiltrating immune cells. Our aim was to explore the pan-cancer immune microenvironment and whether they impacted by ICI biomarkers. Method: 7-plex mIHC was performed to assessed immune cell infiltrations were assessed. Positive PD-L1 expression was defined as ≥1% of tumor cells with membranous staining. Statistical analyses were performed using R version 3.4.4. Result: Among 520 samples, CD8+T cell infiltration in tumor was assessed in Esophagus, Liver, Biliary Tract, Lung, Colorectum, Stomach tumors, ordered by descending median density at the center of the tumor. The median density at the periphery was almost double than the median density at the center. In addition, we have observed high TAM.M1 density in Bladder urinary Tract, Biliary Tract, Liver, with a higher or equivalent level of infiltration in stroma than in tumor. While in contrast, the TAM.M2 cell density was higher in stroma than in tumor. Regarding to PDL1 status in colorectum, there was little difference in the degree of CD8+ T cell infiltration between stroma and tumor. In the term of MSI status, CD8+T cell infiltration was significantly higher in MSIH colorectum tumor. We compared the proportion of above immune cells. In stroma, except lung tumor, CD8+T cells made up the largest share of immune cells, following by NK cells. In tumor, except for lung cancer, NK cells accounted for the highest proportion. Cancer with the highest proportion of NK cells is bladder/urinary tract cancer. Although the proportion of NK cells in lung cancer is also high, macrophages proportion is the highest, especially TAM.M2. Conclusions: Together, these data outlined the immune infiltration inter-, extra-tumor, and associations with TMB, MSI status. Tumor immune microenvironment might serve as promising predictive factors for immunotherapy. Citation Format: Tianqing Chu, Zhang Bei. Pan-cancer characterization of tumor immune microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2796.