Abstract 2795: Dissemination score of CD8+ TILs by automated image analysis is a potential marker of immune activity in human cancers
Authors: Bentink Stefan , Spitzmueller Andreas , Tan Tze Heng , Sade Hadassah , Wu Song , Higgs Brandon W. , Steele Keith E. 
Published: August 2019

The overall density of CD8+ tumor-infiltrating lymphocytes (TILs) is important for characterizing the level of immune activity in the tumor microenvironment (TME). Beyond the densities of CD8+ TILs, both their location and distributional patterns may also have relevance to immune activity. We evaluated 645 resected tumors encompassing seven cancer types, and correlate location and spatial patterns of CD8+ TILs to immune pathway activity.

We integrated image analysis results from digitized immunohistochemistry (IHC) slides with gene expression data from a targeted Ion Torrent Panel. Overall density of CD8+ TILs and the exact position of individual CD8+ lymphocytes were determined from IHC slides. A dissemination score was defined as ratio of global density and average local density of CD8+ TILs. This score is the inverse of the Ripley’s K statistic and becomes high for disseminated spatial patterns. We used this quotient as a continuous metric to identify tumors with a disseminated TIL pattern and to distinguish them from tumors with focal distribution of CD8+ TILs. Within a subset of tumors, the continuous dissemination metric was correlated with biological pathways using targeted mRNA sequencing and gene set enrichment analysis. In addition, association of the dissemination score with overall survival was tested on a subset of cases.

CD8+ TIL distributional patterns differed significantly between tumor types. Breast and pancreatic cancers more frequently showed a focal distribution of CD8+ TILs, while lung tumors comparatively exhibited a disseminated pattern. Transcriptional profiling data revealed differences between both image analysis phenotypes. On average, cases with more disseminated patterns of CD8+ T cells were associated with mRNA expression of genes that fall in pathways related to motility, migration and activation status of tumor infiltrating T cells. We also found a trend to better overall survival in patients whose tumors had a disseminated TIL score compared to those with a focal pattern. This trend was significant in non-small cell adenocarcinoma of the lung (log rank p = 0.018).

We demonstrate the value of spatial image analysis to automatically score CD8+ TIL dissemination as a marker of immune activity in the TME. Jointly analyzing transcriptional profiles appears to identify a biologically meaningful activation phenotype in tumors with high dissemination scores. Our data further suggests that this phenotype is associated with improved overall survival in some cancer patients.

Citation Format: Stefan Bentink, Andreas Spitzmueller, Tze Heng Tan, Hadassah Sade, Song Wu, Brandon W. Higgs, Keith E. Steele. Dissemination score of CD8+ TILs by automated image analysis is a potential marker of immune activity in human cancers [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 2795.