Abstract 1794: Human cancer associated fibroblast subsets can differentially regulate immunotherapy response in head and neck cancer patients

Abstract

Abstract The stromal cancer associated fibroblasts (CAF) have been postulated to modulate immune responses, but their role in clinical immunotherapy has not been rigorously explored in detail. To determine potential biomarkers of response and resistance for αPD-1 therapy in head & neck cancer patients, we performed high dimensional immunophenotyping to include single cell RNA sequencing (scRNA-SEQ) from a neoadjuvant trial of 50 advanced-stage head and neck squamous cell carcinoma (HNSCC) patients that were treated with nivolumab. Sufficient suspension cells from the tumors harvested pre and post nivolumab treatment allowed single-cell RNA sequencing on 4 patients as well as bulk RNA sequencing on 40 patients. Using the Algorithm for the Reconstruction of Accurate Cellular Networks (ARACNe) and Virtual Inference of Protein-activity by Enriched Regulon (VIPER) bioinformatic analysis platform on the matched scRNA-Seq dataset to capture low expressing genes such as transcription factors, we identified 14 distinct cell types present in HNSCC patients. While CD8 T cells did not show increased number among the responder cohort, T cell cluster analysis showed enhanced IFNγ, granzyme, and perforin. Of these 14 cell types, the CAF cluster showed significant changes among the nivolumab responder cohort. Upon deeper analysis of this fibroblast population, we identified 5 distinct clusters of cancer associated fibroblast subsets (CAF-A, B, C, D, and E) of which, one cluster, CAF-A correlated with patient response to αPD-1 therapy. In order to determine the significance of this CAF subset's function, we isolated CD45-EpCAM-CD31-CD29+FAP+ CAF-A's from primary HNSCC tumor specimens and co-cultured with primary human T cells. Analysis by flow cytometry showed that CAF-A suppresses both CD4+ and CD8+ T cell proliferation as well as activation of these T cells. When we queried the cancer genome atlas, CAF-A gene signature correlated with increased survival, corroborating the important regulatory role of these CAF subsets in the context of endogenous immune responses. Overall, our findings demonstrate the functional importance of CAF subsets in modulating the immunoregulatory milieu of the human HNSCC for the first time, and justifies a more in depth characterization of these stromal cells in human squamous carcinoma in the current era of cancer immunotherapy. Citation Format: Diana Graves, Michael J. Korrer, Aleksandar Z. Obradovic, Sohini Roy, Andrea Califano, Charles G. Drake, Young J. Kim. Human cancer associated fibroblast subsets can differentially regulate immunotherapy response in head and neck cancer patients [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 1794.