Abstract 1507: Transcriptional profiles of CD14+ cells in situ in melanoma tumors reveal plasticity and localization dependent function

Mechanisms contributing to immunotherapy resistance in patients are the object of intense studies. Myeloid cells play a major role in tumors and include cells with different functions that can be grossly summarized as: (1) Antigen capture for presentation (dendritic cells, DCs) or for degradation (macrophages); (2) Tissue repair (macrophages) and (3) Effector function (mast cells, monocytes, granulocytes). However, the functional states of myeloid cells in human tumors are not completely understood. To study intact tumor microenvironments we have established a comprehensive approach for cellular and molecular analysis. Modular analysis of bulk RNAseq data of whole melanoma tissue sections stratified patient samples based on lymphocytic infiltrate but revealed inflammation and myeloid modules spread across samples. Polychromatic immunofluorescence and histocytometry showed that CD14+ cells represent the majority of the total tumor immune infiltrate. Furthermore, the majority of T cells present in melanoma tissue are in direct contact with CD14+ cells rather than melanoma cells. The distribution of CD14+ cells shows two distinct patterns: CD14+ cells within cancer nests (intratumoral) which are in close proximity to melanoma cells and are loaded with melanoma protein; CD14+ cells in the tissue surrounding cancer nests (stromal) which do not contain melanoma protein cargo and are organized in dense infiltrates. Using customized immunofluorescence-guided laser capture micro-dissection, we harvested CD14+ cells based on their tissue location and melanoma protein load for downstream analysis. We find that unsupervised clustering of transcriptomes groups cells by their tissue localization, i.e., intratumoral vs. stromal. Computational analysis, revealed distinct and replicable gene signatures associated with different pathways, in intratumoral and stromal CD14+ cells. Thus, the transcriptome differentiates the functional status of CD14+ cells related to their localization within tumor. Citation Format: Jan Martinek, Kyung In Kim, Te-Chia Wu, Victor Wang, Hannah M. Brookes, Lili Sun, Ananya Gulati, Joshy George, Philipp Henrich, Florentina Marches, Anthony Rongvaux, Michael Chiorazzi, Jeff Chuang, Paul Robson, Richard Flavell, Jacques Banchereau, Karolina Palucka. Transcriptional profiles of CD14+ cells in situ in melanoma tumors reveal plasticity and localization dependent function [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 1507.