{"doi":"10.7302/4638","title":"Using Single Cell RNA Sequencing to Elucidate Mechanisms of Immune Suppression in the Pancreatic Tumor Microenvironment","abstract":"Pancreatic ductal adenocarcinoma (PDA) is the third leading cause of cancer related death, with a five-year survival rate of 11%. Not only is PDA often diagnosed at advanced stages, but the standard of care chemotherapy is largely ineffective. The distinctive biologic characteristics of PDA make it difficult to treat. PDA is typically driven by an oncogenic Kras mutation. Oncogenic Kras is required for the maintenance of PDA, but inhibitors for this oncogene are few. Another key feature of PDA is the extensive fibroinflammatory stroma that constitutes the bulk of the tumor volume. The stroma includes fibroblasts, extracellular matrix and abundant infiltrating immune cells. The latter are largely immunosuppressive immune cells, including regulatory T cells, myeloid-derived suppressor cells, and tumor associated macrophages. Data from our laboratory and many others show that immune cells are a key determinant of PDA progression and metastasis. The overarching goal of my project is to understand the nature and regulation of the immune response in the PDA tumor microenvironment by dissecting the crosstalk between tumor cells and immune cells to devise strategies to reverse the immune suppression that characterizes PDA. First, we performed a multimodal analysis of human PDA tumors and PBMCs, using multiplex immunohistochemistry, mass cytometry, and single cell RNA sequencing to describe the composition of human PDA and hypothesize possible interactions between the various cell types based on abundance, localization, and receptor-ligand expression. The combination of these techniques highlighted the prevalence of understudied immune checkpoint TIGIT in human PDA compared to normal pancreas. Functionally, we discovered that TIGIT expression is significantly elevated in exhausted CD8 T cells than in effector CD8 T cells, while classical immune checkpoint protein PD-1 was not significantly different. This work demonstrates the efficacy of the discovery pipeline pioneered by members of the lab, using a combination of high resolution techniques to uncover novel and potentially efficacious treatment strategies in PDA. Secondly, we used single cell RNA sequencing to analyze the transcriptome of the various cell types present in the liver metastases of PDA patients. We characterized the different cell populations and performed differential expression analyses to determine genes upregulated in PDA metastases vs. primary tumors. We then determined putative receptor-ligand interactions based on expression of receptors and ligands on source and target cells in the PDA TME showing preliminary evidence of immune suppression in PDA liver metastases. Finally, using mouse models of both pancreatic and lung cancer, we studied the effects of oncogenic Kras on the maintenance of the tumor microenvironment in both pancreatic and lung cancers with the goal of discovering the effect oncogenic KrasG12D has on the tumor microenvironment in both primary and metastatic tumors. We verified the functionality of two mouse models of inducible Kras driven pancreas and lung cancer and performed mfIHC on the model of lung cancer to characterize the shifting immune populations in the progression and regression of the lung tumor. Together, these studies illustrate the importance of understanding cell signaling in the tumor microenvironment. By uncovering previously understudied mechanisms of immune suppression and elucidating the requirement of KRAS in establishing the TME, our work represents the first step in the identification of interactions required for the maintenance of PDA tumors. Further work is necessary to evaluate the physiological importance of these interactions and subsequently determine their translational potential.","journal":"Deep Blue (University of Michigan)","year":2022,"id":310118,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":0,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9566,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2022-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":225395,"name":"Veerin R. Sirihorachai","orcid":"0000-0003-4992-6499","position":0,"is_corresponding":true}],"reference_count":0,"raw_metadata":null,"created_at":"2026-07-19T00:33:15.860993Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}