Abstract A103: Transcriptional profiles of CD14+ cells in situ in melanoma reveal plasticity, localization-dependent function, and specific T-cell interactions

Mechanisms contributing to immunotherapy resistance in patients are the object of intense studies. The 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 status of myeloid cells in human tumors is not completely understood. To study intact tumor microenvironments, we have established a comprehensive approach for cellular and molecular analysis. Polychromatic immunofluorescence and histocytometry showed that CD14+ cells represent the majority of the total tumor immune infiltrate. Furthermore, while the majority of the T cells are located outside of cancer nests, most of the T cells present in the 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 nest (intratumoral) are in close interactions with melanoma cells and are loaded with melanoma protein; CD14+ cells in the tissue surrounding cancer nest (stromal) do not show melanoma protein cargo and are organized in dense infiltrates. Using customized immunofluorescence-guided laser capture microdissection, we harvested CD3+ T cells based on their tissue location and CD14+ cells based on their tissue location and melanoma protein load for downstream analysis. RNAseq revealed transcriptional profiles that clustered patient samples according to their tissue localization, i.e., intratumoral vs. stromal; interestingly, this was not the case for the CD3+ T cells. Computational analysis revealed distinct gene signatures associated with different pathways in intratumoral and stromal CD14+ cells. Thus, transcriptome differentiates functional status of CD14+ cells related to their localization within tumor. Further, the intra/stromal CD14+ signature clustered TCGA patient samples with significantly different survival, which in metastatic melanoma was linked with dendritic cells’ signature in the stroma. Finally, we show that receptor ligand interactions between myeloid and T cells are tissue localization specific. Citation Format: Jan Martinek, Kyung in Kim, Te-Chia Wu, Hannah Boruchov, Ananya Gulati, Lili Sun, Victor Wang, 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 reveal plasticity, localization-dependent function, and specific T-cell interactions [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A103.