Identification of Genetic Determinants of Pancreatic Cancer Immune Phenotypes by Integrative Genome-scale Analysis

Abstract

Background Pancreatic cancer (PC) is a malignant neoplasm of the digestive tract that is highly malignant and difficult to diagnose at an early stage with high postoperative mortality and low cure rates. Cancer immunotherapy is innovating the clinical treatment of several cancers, but has a limited role in PC. The incomplete understanding of immune response hinders the development of gene therapy. To fill this gap, it is very necessary to classify the immunogenic subtypes of PC to understand the relationship between tumor microenvironments and clinical pathological characteristics, DNA damage repair and tumor immune response.Methods We extracted copy number change, somatic mutation and expression data from tumor genome map (TCGA). Using RNA sequencing data, we defined three different immunophenotypes and elucidated how immune cell interactions in immune subtypes vary with the background of the immune system. Further correlation analysis between DNA damage repair (DDR) related genes expression and immune response was conducted to explore the effects of DDR expression on antitumor activity in the tumor microenvironments.Results We defined three different immunophenotypes and elucidated how immune cell interactions in immune subtypes vary with the background of the immune system. When the total number of mutations was standardized, no enrichment of new epitopes was detected in immunocompetent phenotypes. These observations suggest that mutations in Th-1 enriched IS3 tumors are essentially no more immunogenic than those in IS2 cancers. We also found that the expression patterns of key IFN mediators STAT1 and / or STAT3 were increased in tumors with DDR mutations (19 of ATM, ERCC1, Rb1, BRCA2, pole and TP53), which is a reflex activation of IFN pathway.Conclusions Three defined immune subtypes show different characteristics of immune cell infiltration, revealing different manifestations in anti-cancer immune function. That is to say, clinical biological events of differential tumors are associated to immune-phenotypes. The invasive phenotype was driven by somatic mutations across immune subtypes, and DDR defect may also influence the response of tumor immune subtypes. Our results suggested that the occurrence of pancreatic cancer is related to genetic factors of immunophenotype, providing information for clinical prognosis and outcome of pancreatic cancer.