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Single-cell transcriptome analysis of tumor and stromal compartments of pancreatic ductal adenocarcinoma primary tumors and metastatic lesions

ABSTRACT: Background Solid tumors such as pancreatic ductal adenocarcinoma (PDAC) comprise not just tumor cells but also a microenvironment with which the tumor cells constantly interact. Detailed characterization of the cellular composition of the tumor microenvironment is critical to the understanding of the disease and treatment of the patient. Single-cell transcriptomics has been used to study the cellular composition of different solid tumor types including PDAC. However, almost all of those studies used primary tumor tissues. Methods In this study, we employed a single-cell RNA sequencing technology to profile the transcriptomes of individual cells from dissociated primary tumors or metastatic biopsies obtained from patients with PDAC. Unsupervised clustering analysis as well as a new supervised classification algorithm, SuperCT, was used to identify the different cell types within the tumor tissues. The expression signatures of the different cell types were then compared between primary tumors and metastatic biopsies. The expressions of the cell type-specific signature genes were also correlated with patient survival using public datasets. Results Our single-cell RNA sequencing analysis revealed distinct cell types in primary and metastatic PDAC tissues including tumor cells, endothelial cells, cancer-associated fibroblasts (CAFs), and immune cells. The cancer cells showed high inter-patient heterogeneity, whereas the stromal cells were more homogenous across patients. Immune infiltration varies significantly from patient to patient with majority of the immune cells being macrophages and exhausted lymphocytes. We found that the tumor cellular composition was an important factor in defining the PDAC subtypes. Furthermore, the expression levels of cell type-specific markers for EMT+ cancer cells, activated CAFs, and endothelial cells significantly associated with patient survival. Conclusions Taken together, our work identifies significant heterogeneity in cellular compositions of PDAC tumors and between primary tumors and metastatic lesions. Furthermore, the cellular composition was an important factor in defining PDAC subtypes and significantly correlated with patient outcome. These findings provide valuable insights on the PDAC microenvironment and could potentially inform the management of PDAC patients.

SUBMITTER: Lin W

PROVIDER: S-EPMC7523332 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Project description:Pancreatic ductal adenocarcinoma (PDAC) is typically diagnosed at an advanced stage, with systemic therapy being the mainstay of treatment. Survival continues to be limited, typically less than 1 year. The PDAC microenvironment is characterized by a paucity of malignant epithelial cells, abundant stroma with predominantly immunosuppressive T cells and myelosuppressive-type macrophages (M2), and hypovascularity. The current treatment options for metastatic PDAC are modified (m)FOLFIRINOX /FOLFIRINOX or nab-paclitaxel and gemcitabine in patients with good performance status (PS) (ECOG 0-1/KPS 70-100%) and gemcitabine with or without a second agent for those with ECOG PS 2-3. New therapies are emerging, and the current guidelines endorse both germline and somatic testing in PDAC to evaluate actionable findings. Important themes related to new therapeutic approaches include DNA damage repair strategies, immunotherapy, targeting the stroma, and cancer-cell metabolism. Targeted therapy alone (outside small genomically defined subsets) or in combination with standard cytotoxic therapy, thus far, has proven disappointing in PDAC; however, novel therapies are evolving with increased integration of genomic profiling along with a better understanding of the tumor microenvironment and immunology. A small but important sub-group of patients have some of these agents available in the clinics for use. Olaparib was recently approved by the US Food and Drug Administration for maintenance therapy in germline BRCA1/2 mutated PDAC following demonstration of survival benefit in a phase 3 trial. Pembrolizumab is approved for patients with defects in mismatch repair/microsatellite instability. PDAC with wild-type KRAS represents a unique subgroup who have enrichment of potentially targetable oncogenic drivers. Small-molecule inhibitors including ERBB inhibitors (e.g., afatinib, MCLA-128), TRK inhibitors (e.g., larotrectinib, entrectinib), ALK/ROS inhibitor (e.g., crizotinib), and BRAF/MEK inhibitors are in development. In a small subset of patients with the KRASG12C mutation, a KRASG12C inhibitor, AMG510, and other agents are being investigated. Major efforts are underway to effectively target the tumor microenvironment and to integrate immunotherapy into the treatment of PDAC, and although thus far the impact has been modest to ineffective, nonetheless, there is optimism that some of the challenges will be overcome.

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Single-cell transcriptome analysis of tumor and stromal compartments of pancreatic ductal adenocarcinoma primary tumors and metastatic lesions

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