Immunological and Metabolic Features of Pancreatic Ductal Adenocarcinoma Define Prognostic Subtypes of Disease

Purpose: Pancreatic ductal adenocarcinoma (PDA) is associated with an immunosuppressive microenvironment that supports the growth of the malignancy as well as immune system evasion. Here we examine markers of immunosuppression in PDA within the context of the glycolytic tumor microenvironment, their inter-relationship with tumor biology and association with overall survival. Experimental design: We utilized tissue microarrays consisting of 223 PDA patients annotated for clinical stage, tumor size, lymph node involvement, and survival. Expression of CD163, FoxP3, PDL1, and MCT4 was assessed by immunohistochemistry and statistical associations were evaluated by univariate and multivariate analysis. Multi-marker subtypes were defined by Random Forest analysis. Mechanistic interactions were evaluated using PDA cell lines and models for myeloid differentiation. Results: Conclusions: 5 impact the contributions of other immune cells in PDA (19, 20). Since increased expression of the lactate exporter MCT4 (SLC16A3) also portends poor outcome in PDA (4), we hypothesized that the glycolytic imbalance in pancreatic cancer cells, represented by MCT4 expression, directly impacts the surrounding immune milieu and that these characteristics could be used to identify distinct disease subtypes. To this end, in this study we examine the tumor microenvironment of PDA patients for indicators of an immunosuppressive phenotype and utilize these elements to define prognostic subtypes of disease. Further, we demonstrate in vitro that the metabolic context of pancreatic cancer cells can influence the phenotype of associated immune cells and, by extension, expression of the lactate exporter MCT4 can further refine the disease-immune subtypes. Immune infiltrate scoring. Lymphocytes and neutrophils were assessed in haematoxylin and eosin stained whole tissue sections at 10x magnification in either the central area of the tumor (tumor cellular environment field) or at the tumor’s invasive margin (tumor stroma field). The presence of infiltrate was assessed using a four-degree scale in each area, where a score of 0 indicated no presence, 1 denoted a mild and patchy appearance of inflammatory infiltrate (rare), 2 signified a prominent inflammatory reaction (intermittent), and 3 represented dense infiltration (frequent). Here we MCT4 knockdown lactate efflux reduce glucose uptake consistent with our previous findings, which also indicated that MCT4 to maintain proper lactate production Strikingly, patients that had low expression of MCT4 in with diminished markers of suppressive immune cells demonstrated significantly improved survival as compared to other clusters. These data suggest that a combination of immune and metabolic features in PDA define subsets of disease that sufficiently correspond to prognosis. Taken together, these data suggest that the individual metabolic state of PDA malignancies may portend the efficacy of potential immunotherapies and that, ultimately, a combined approach comprised of immunotherapy and a targeted metabolic therapy may increase treatment efficacy.