The MUC1-HIF-1α signaling axis regulates pancreatic cancer pathogenesis through polyamine metabolism remodeling.

Dysregulation of polyamine metabolism has been implicated in cancer initiation and progression; however, the mechanism of polyamine dysregulation in cancer is not fully understood. In this study, we investigated the role of MUC1, a mucin protein overexpressed in pancreatic cancer, in regulating polyamine metabolism. Utilizing pancreatic cancer patient data, we noted a positive correlation between MUC1 expression and the expression of key polyamine metabolism pathway genes. Functional studies revealed that knockdown of spermidine/spermine N1-acetyltransferase 1 (SAT1), a key enzyme involved in polyamine catabolism, attenuated the oncogenic functions of MUC1, including cell survival and proliferation. We further identified a regulatory axis whereby MUC1 stabilized hypoxia-inducible factor (HIF-1α), leading to increased SAT1 expression, which in turn induced carbon flux into the tricarboxylic acid cycle. MUC1-mediated stabilization of HIF-1α enhanced the promoter occupancy of the latter on SAT1 promoter and corresponding transcriptional activation of SAT1, which could be abrogated by pharmacological inhibition of HIF-1α or CRISPR/Cas9-mediated knockout of HIF1A. MUC1 knockdown caused a significant reduction in the levels of SAT1-generated metabolites, N1-acetylspermidine and N8-acetylspermidine. Given the known role of MUC1 in therapy resistance, we also investigated whether inhibiting SAT1 would enhance the efficacy of FOLFIRINOX chemotherapy. By utilizing organoid and orthotopic pancreatic cancer mouse models, we observed that targeting SAT1 with pentamidine improved the efficacy of FOLFIRINOX, suggesting that the combination may represent a promising therapeutic strategy against pancreatic cancer. This study provides insights into the interplay between MUC1 and polyamine metabolism, offering potential avenues for the development of treatments against pancreatic cancer.

Inflammatory and immune effects on tumor progression.

Tumor progression is known occur in a complex microenvironment that leads to genetic, cellular, and metabolic adaptations. Two articles from Martin et al. and Del Poggetto et al. enlighten us on the role of inflammation and the immune system in guiding the progression of preneoplastic cells to oncogenic transformation and on subsequent tumor evolution.

The cholesterol pathway: impact on immunity and cancer.

Cholesterol is a multifaceted metabolite that is known to modulate processes in cancer, atherosclerosis, and autoimmunity. A common denominator between these diseases appears to be the immune system, in which many cholesterol-associated metabolites impact both adaptive and innate immunity. Many cancers display altered cholesterol metabolism, and recent studies demonstrate that manipulating systemic cholesterol metabolism may be useful in improving immunotherapy responses. However, cholesterol can have both proinflammatory and anti-inflammatory roles in mammals, acting via multiple immune cell types, and depending on context. Gaining mechanistic insights into various cholesterol-related metabolites can improve our understanding of their functions and extensive effects on the immune system, and ideally will inform the design of future therapeutic strategies against cancer and/or other pathologies.

Metabolic Rewiring by Loss of Sirt5 Promotes Kras-Induced Pancreatic Cancer Progression.

BACKGROUND & AIMS: SIRT5 plays pleiotropic roles via post-translational modifications, serving as a tumor suppressor, or an oncogene, in different tumors. However, the role SIRT5 plays in the initiation and progression of pancreatic ductal adenocarcinoma (PDAC) remains unknown. METHODS: Published datasets and tissue arrays with SIRT5 staining were used to investigate the clinical relevance of SIRT5 in PDAC. Furthermore, to define the role of SIRT5 in the carcinogenesis of PDAC, we generated autochthonous mouse models with conditional Sirt5 knockout. Moreover, to examine the mechanistic role of SIRT5 in PDAC carcinogenesis, SIRT5 was knocked down in PDAC cell lines and organoids, followed by metabolomics and proteomics studies. A novel SIRT5 activator was used for therapeutic studies in organoids and patient-derived xenografts. RESULTS: SIRT5 expression negatively regulated tumor cell proliferation and correlated with a favorable prognosis in patients with PDAC. Genetic ablation of Sirt5 in PDAC mouse models promoted acinar-to-ductal metaplasia, precursor lesions, and pancreatic tumorigenesis, resulting in poor survival. Mechanistically, SIRT5 loss enhanced glutamine and glutathione metabolism via acetylation-mediated activation of GOT1. A selective SIRT5 activator, MC3138, phenocopied the effects of SIRT5 overexpression and exhibited antitumor effects on human PDAC cells. MC3138 also diminished nucleotide pools, sensitizing human PDAC cell lines, organoids, and patient-derived xenografts to gemcitabine. CONCLUSIONS: Collectively, we identify SIRT5 as a key tumor suppressor in PDAC, whose loss promotes tumorigenesis through increased noncanonic use of glutamine via GOT1, and that SIRT5 activation is a novel therapeutic strategy to target PDAC.

A Polymeric Nanogel-Based Treatment Regimen for Enhanced Efficacy and Sequential Administration of Synergistic Drug Combination in Pancreatic Cancer.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers. A combination of cisplatin (CDDP) and gemcitabine (Gem) treatment has shown favorable clinical results for metastatic disease; both are limited by toxicities and nontargeted delivery. More than 80% of PDAC aberrantly expresses the sialyl Tn (STn) antigen due to the loss of function of the core 1ß3-Gal-T-specific molecular chaperone, a specific chaperone for the activity of core 1 ß3-galactosyltransferase or C1GalT. Here, we report the development of polymeric nanogels (NGs) loaded with CDDP and coated with an anti-STn antigen-specific antibody (TKH2 monoclonal antibody) for the targeted treatment of PDAC. TKH2-functionalized, CDDP-loaded NGs delivered a significantly higher amount of platinum into the cells and tumors expressing STn antigens. We also confirmed that a synergistic cytotoxic effect of sequential exposure of pancreatic cancer cells to Gem followed by CDDP can be mimicked by the codelivery of CDDP-loaded NGs (NG/CDDP) and free Gem. In a murine orthotopic model of PDAC, combined simultaneous treatment with Gem and targeted NG/CDDP significantly attenuated tumor growth with no detectable acute toxicity. Altogether, these results suggest that combination therapy consisting of Gem followed by TKH2-conjugated CDDP NGs induces highly synergistic therapeutic efficacy against pancreatic cancer. Our results offer the basis for development of combination drug regimens using targeted nanomedicines to increase treatment effectiveness and improve outcomes of PDAC therapy.

Combination of mAb-AR20.5, anti-PD-L1 and PolyICLC inhibits tumor progression and prolongs survival of MUC1.Tg mice challenged with pancreatic tumors.

A substantial body of evidence suggests the existence of MUC1-specific antibodies and cytotoxic T cell activities in pancreatic cancer patients. However, tumor-induced immunosuppression renders these responses ineffective. The current study explores a novel therapeutic combination wherein tumor-bearing hosts can be immunologically primed with their own antigen, through opsonization with a tumor antigen-targeted antibody, mAb-AR20.5. We evaluated the efficacy of immunization with this antibody in combination with PolyICLC and anti-PD-L1. The therapeutic combination of mAb-AR20.5 + anti-PD-L1 + PolyICLC induced rejection of human MUC1 expressing tumors and provided a long-lasting, MUC1-specific cellular immune response, which could be adoptively transferred and shown to provide protection against tumor challenge in human MUC1 transgenic (MUC.Tg) mice. Furthermore, antibody depletion studies revealed that CD8 cells were effectors for the MUC1-specific immune response generated by the mAb-AR20.5 + anti-PD-L1 + PolyICLC combination. Multichromatic flow cytometry data analysis demonstrated a significant increase over time in circulating, activated CD8 T cells, CD3+CD4-CD8-(DN) T cells, and mature dendritic cells in mAb-AR20.5 + anti-PD-L1 + PolyICLC combination-treated, tumor-bearing mice, as compared to saline-treated control counterparts. Our study provides a proof of principle that an effective and long-lasting anti-tumor cellular immunity can be achieved in pancreatic tumor-bearing hosts against their own antigen (MUC1), which can be further potentiated using a vaccine adjuvant and an immune checkpoint inhibitor.

MUC1: a novel metabolic master regulator.

MUC1, a type I transmembrane protein, is significantly overexpressed and aberrantly glycosylated in tumors of epithelial origin. By virtue of its aberrant signaling due to loss of apical-basal polarity in cancer, MUC1 regulates the metabolite flux at multiple levels. Serving as a transcriptional co-activator, MUC1 directly regulates expression of metabolic genes. By regulating receptor tyrosine kinase signaling, MUC1 facilitates production of biosynthetic intermediates required for cell growth. Also, via direct interactions, MUC1 modulates the activity/stability of enzymes and transcription factors that directly regulate metabolic functions. Additionally, by modulation of autophagy, levels of reactive oxygen species, and metabolite flux, MUC1 facilitates cancer cell survival under hypoxic and nutrient-deprived conditions. This article provides a comprehensive review of recent literature on novel metabolic functions of MUC1.

MUC1 mucin stabilizes and activates hypoxia-inducible factor 1 alpha to regulate metabolism in pancreatic cancer.

Aberrant glucose metabolism is one of the hallmarks of cancer that facilitates cancer cell survival and proliferation. Here, we demonstrate that MUC1, a large, type I transmembrane protein that is overexpressed in several carcinomas including pancreatic adenocarcinoma, modulates cancer cell metabolism to facilitate growth properties of cancer cells. MUC1 occupies the promoter elements of multiple genes directly involved in glucose metabolism and regulates their expression. Furthermore, MUC1 expression enhances glycolytic activity in pancreatic cancer cells. We also demonstrate that MUC1 expression enhances in vivo glucose uptake and expression of genes involved in glucose uptake and metabolism in orthotopic implantation models of pancreatic cancer. The MUC1 cytoplasmic tail is known to activate multiple signaling pathways through its interactions with several transcription factors/coregulators at the promoter elements of various genes. Our results indicate that MUC1 acts as a modulator of the hypoxic response in pancreatic cancer cells by regulating the expression/stability and activity of hypoxia-inducible factor-1α (HIF-1α). MUC1 physically interacts with HIF-1α and p300 and stabilizes the former at the protein level. By using a ChIP assay, we demonstrate that MUC1 facilitates recruitment of HIF-1α and p300 on glycolytic gene promoters in a hypoxia-dependent manner. Also, by metabolomic studies, we demonstrate that MUC1 regulates multiple metabolite intermediates in the glucose and amino acid metabolic pathways. Thus, our studies indicate that MUC1 acts as a master regulator of the metabolic program and facilitates metabolic alterations in the hypoxic environments that help tumor cells survive and proliferate under such conditions.

Structure and function of human DnaJ homologue subfamily a member 1 (DNAJA1) and its relationship to pancreatic cancer.

Pancreatic cancer has a dismal 5 year survival rate of 5.5% that has not been improved over the past 25 years despite an enormous amount of effort. Thus, there is an urgent need to identify truly novel yet druggable protein targets for drug discovery. The human protein DnaJ homologue subfamily A member 1 (DNAJA1) was previously shown to be downregulated 5-fold in pancreatic cancer cells and has been targeted as a biomarker for pancreatic cancer, but little is known about the specific biological function for DNAJA1 or the other members of the DnaJ family encoded in the human genome. Our results suggest the overexpression of DNAJA1 suppresses the stress response capabilities of the oncogenic transcription factor, c-Jun, and results in the diminution of cell survival. DNAJA1 likely activates a DnaK protein by forming a complex that suppresses the JNK pathway, the hyperphosphorylation of c-Jun, and the anti-apoptosis state found in pancreatic cancer cells. A high-quality nuclear magnetic resonance solution structure of the J-domain of DNAJA1 combined with a bioinformatics analysis and a ligand affinity screen identifies a potential DnaK binding site, which is also predicted to overlap with an inhibitory binding site, suggesting DNAJA1 activity is highly regulated.

Measurement of Metabolic Alteration in Immune Cells Under Hypoxia.

The hypoxic microenvironment in solid tumors affects the metabolism of tumor cells and infiltrating immune cells, which aids in robust tumor growth and expansion. Myeloid-derived suppressor cells (MDSCs) are heterogenous immature myeloid cells in the TME, which play an essential role in immune evasion by subverting T/NK cell-mediated killing. The immunosuppressive function of MDSCs is tightly regulated to the metabolic pathways, in which hypoxia plays a critical role. In this chapter, we describe the isolation of murine MDSCs from bone marrows and the measurement of the transcriptomic changes of essential metabolic enzymes under hypoxic conditions. This method can be applied to study MDSCs function, mimicking the hypoxic environment in vitro. This method can be utilized to investigate the critical metabolic alterations under a given tumor context and help evaluate the efficacy of metabolic-targeted therapies in the long run.

DHODH inhibition enhances the efficacy of immune checkpoint blockade by increasing cancer cell antigen presentation.

Pyrimidine nucleotide biosynthesis is a druggable metabolic dependency of cancer cells, and chemotherapy agents targeting pyrimidine metabolism are the backbone of treatment for many cancers. Dihydroorotate dehydrogenase (DHODH) is an essential enzyme in the de novo pyrimidine biosynthesis pathway that can be targeted by clinically approved inhibitors. However, despite robust preclinical anticancer efficacy, DHODH inhibitors have shown limited single-agent activity in phase 1 and 2 clinical trials. Therefore, novel combination therapy strategies are necessary to realize the potential of these drugs. To search for therapeutic vulnerabilities induced by DHODH inhibition, we examined gene expression changes in cancer cells treated with the potent and selective DHODH inhibitor brequinar (BQ). This revealed that BQ treatment causes upregulation of antigen presentation pathway genes and cell surface MHC class I expression. Mechanistic studies showed that this effect is 1) strictly dependent on pyrimidine nucleotide depletion, 2) independent of canonical antigen presentation pathway transcriptional regulators, and 3) mediated by RNA polymerase II elongation control by positive transcription elongation factor B (P-TEFb). Furthermore, BQ showed impressive single-agent efficacy in the immunocompetent B16F10 melanoma model, and combination treatment with BQ and dual immune checkpoint blockade (anti-CTLA-4 plus anti-PD-1) significantly prolonged mouse survival compared to either therapy alone. Our results have important implications for the clinical development of DHODH inhibitors and provide a rationale for combination therapy with BQ and immune checkpoint blockade.

Vitamin B6 Competition in the Tumor Microenvironment Hampers Antitumor Functions of NK Cells.

Nutritional factors play crucial roles in immune responses. The tumor-caused nutritional deficiencies are known to affect antitumor immunity. Here, we demonstrate that pancreatic ductal adenocarcinoma (PDAC) cells can suppress NK-cell cytotoxicity by restricting the accessibility of vitamin B6 (VB6). PDAC cells actively consume VB6 to support one-carbon metabolism, and thus tumor cell growth, causing VB6 deprivation in the tumor microenvironment. In comparison, NK cells require VB6 for intracellular glycogen breakdown, which serves as a critical energy source for NK-cell activation. VB6 supplementation in combination with one-carbon metabolism blockage effectively diminishes tumor burden in vivo. Our results expand the understanding of the critical role of micronutrients in regulating cancer progression and antitumor immunity, and open new avenues for developing novel therapeutic strategies against PDAC. SIGNIFICANCE: The nutrient competition among the different tumor microenvironment components drives tumor growth, immune tolerance, and therapeutic resistance. PDAC cells demand a high amount of VB6, thus competitively causing NK-cell dysfunction. Supplying VB6 with blocking VB6-dependent one-carbon metabolism amplifies the NK-cell antitumor immunity and inhibits tumor growth in PDAC models. This article is featured in Selected Articles from This Issue, p. 5.

Cancer-associated fibroblast-derived acetate promotes pancreatic cancer development by altering polyamine metabolism via the ACSS2-SP1-SAT1 axis.

The ability of tumour cells to thrive in harsh microenvironments depends on the utilization of nutrients available in the milieu. Here we show that pancreatic cancer-associated fibroblasts (CAFs) regulate tumour cell metabolism through the secretion of acetate, which can be blocked by silencing ATP citrate lyase (ACLY) in CAFs. We further show that acetyl-CoA synthetase short-chain family member 2 (ACSS2) channels the exogenous acetate to regulate the dynamic cancer epigenome and transcriptome, thereby facilitating cancer cell survival in an acidic microenvironment. Comparative H3K27ac ChIP-seq and RNA-seq analyses revealed alterations in polyamine homeostasis through regulation of SAT1 gene expression and enrichment of the SP1-responsive signature. We identified acetate/ACSS2-mediated acetylation of SP1 at the lysine 19 residue that increased SP1 protein stability and transcriptional activity. Genetic or pharmacologic inhibition of the ACSS2-SP1-SAT1 axis diminished the tumour burden in mouse models. These results reveal that the metabolic flexibility imparted by the stroma-derived acetate enabled cancer cell survival under acidosis via the ACSS2-SP1-SAT1 axis.

LXR Signaling-Mediated Cholesterol Metabolism Reprogramming Regulates Cancer Cell Metastasis.

Metastasis is a key contributor to mortality in patients with cancer. While many regulators of metastasis have been identified, critical targets to prevent and inhibit metastatic tumor growth remain elusive. A recent study in this issue of Cancer Research by Deng and colleagues compared gene expression signatures between primary esophageal squamous cell carcinoma tumors and metastatic tumors and combined the analysis with genes induced in metastatic cancer cell lines, which identified anoctamin 1 (ANO1) as a key driver of metastasis. ANO1 caused cholesterol accumulation by inhibiting LXR signaling and decreased cholesterol hydroxylation by downregulating the expression of cholesterol hydroxylase CYP27A1. ANO1 also regulated tumor cell-fibroblast cross-talk that contributed to inflammatory cytokine signaling (IL1ß) and metastasis. Through in silico analysis, the study identified a novel small-molecule inhibitor of ANO1 that decreased tumor burden at a metastatic site. These studies provide novel insights into the role of ANO1 in cellular cholesterol metabolism and associated signaling in mediating metastasis. See related article by Deng et al., p. 1851.

CD73 induces GM-CSF/MDSC-mediated suppression of T cells to accelerate pancreatic cancer pathogenesis.

Metabolic alterations regulate cancer aggressiveness and immune responses. Given the poor response of pancreatic ductal adenocarcinoma (PDAC) to conventional immunotherapies, we investigated the link between metabolic alterations and immunosuppression. Our metabolic enzyme screen indicated that elevated expression of CD73, an ecto-5'-nucleotidase that generates adenosine, correlates with increased aggressiveness. Correspondingly, we observed increased interstitial adenosine levels in tumors from spontaneous PDAC mouse models. Diminishing CD73 by genetic manipulations ablated in vivo tumor growth, and decreased myeloid-derived suppressor cells (MDSC) in orthotopic mouse models of PDAC. A high-throughput cytokine profiling demonstrated decreased GM-CSF in mice implanted with CD73 knockdowns. Furthermore, we noted increased IFN-γ expression by intratumoral CD4+ and CD8+ T cells in pancreatic tumors with CD73 knockdowns. Depletion of CD4+ T cells, but not CD8+ T cells abrogated the beneficial effects of decreased CD73. We also observed that splenic MDSCs from Nt5e knockdown tumor-bearing mice were incompetent in suppressing T cell activation in the ex vivo assays. Replenishing GM-CSF restored tumor growth in Nt5e knockout tumors, which was reverted by MDSC depletion. Finally, anti-CD73 antibody treatment significantly improved gemcitabine efficacy in orthotopic models. Thus, targeting the adenosine axis presents a novel therapeutic opportunity for improving the anti-tumoral immune response against PDAC.

Heme Oxygenase-1 Inhibition Potentiates the Effects of Nab-Paclitaxel-Gemcitabine and Modulates the Tumor Microenvironment in Pancreatic Ductal Adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with a poor prognosis. Tumor hypoxia plays an active role in promoting tumor progression, malignancy, and resistance to therapy in PDAC. We present evidence that nab-paclitaxel-gemcitabine (NPG) and/or a hypoxic tumor microenvironment (TME) up-regulate heme oxygenase-1 (HO-1), providing a survival advantage for tumors. Using PDAC cells in vitro and a PDAC mouse model, we found that NPG chemotherapy up-regulated expression of HO-1 in PDAC cells and increased its nuclear translocation. Inhibition of HO-1 with ZnPP and SnPP sensitized PDAC cells to NPG-induced cytotoxicity (p < 0.05) and increased apoptosis (p < 0.05). Additionally, HO-1 expression was increased in gemcitabine-resistant PDAC cells (p < 0.05), and HO-1 inhibition increased GEM-resistant PDAC sensitivity to NPG (p < 0.05). NPG combined with HO-1 inhibitor inhibited tumor size in an orthotopic model. In parallel, HO-1 inhibition abrogated the influx of macrophages and FoxP3+ cells, while increasing the proportion of CD8+ infiltration in the pancreatic tumors. These effects were mediated primarily by reducing expression of the immunosuppressive cytokine IL-10.

IgE-Based Therapeutic Combination Enhances Antitumor Response in Preclinical Models of Pancreatic Cancer.

Pancreatic ductal adenocarcinoma (PDAC) represents 3% of all cancer cases and 7% of all cancer deaths in the United States. Late diagnosis and inadequate response to standard chemotherapies contribute to an unfavorable prognosis and an overall 5-year survival rate of less than 10% in PDAC. Despite recent advances in tumor immunology, tumor-induced immunosuppression attenuates the immunotherapy response in PDAC. To date, studies have focused on IgG-based therapeutic strategies in PDAC. With the recent interest in IgE-based therapies in multiple solid tumors, we explored the MUC1-targeted IgE potential against pancreatic cancer. Our study demonstrates the notable expression of FceRI (receptor for IgE antibody) in tumors from PDAC patients. Our study showed that administration of MUC1 targeted-IgE (mouse/human chimeric anti-MUC1.IgE) antibody at intermittent levels in combination with checkpoint inhibitor (anti-PD-L1) and TLR3 agonist (PolyICLC) induces a robust antitumor response that is dependent on NK and CD8 T cells in pancreatic tumor-bearing mice. Subsequently, our study showed that the antigen specificity of the IgE antibody plays a vital role in executing the antitumor response as nonspecific IgE, induced by ovalbumin (OVA), failed to restrict tumor growth in pancreatic tumor-bearing mice. Utilizing the OVA-induced allergic asthma-PDAC model, we demonstrate that allergic phenotype induced by OVA cannot restrain pancreatic tumor growth in orthotopic tumor-bearing mice. Together, our data demonstrate the novel tumor protective benefits of tumor antigen-specific IgE-based therapeutics in a preclinical model of pancreatic cancer, which can open new avenues for future clinical interventions.

Metabolic Subtyping for Novel Personalized Therapies Against Pancreatic Cancer.

Through metabolic subtyping, metabolic vulnerabilities can be exploited for developing efficacious treatments. A glycolytic subtype indicates poor survival in patients with pancreatic cancer, whereas a cholesterogenic subtype correlates with better outcomes potentially due to more energy expenditure. Personalized medicine holds great promise for improving therapy outcomes by optimally targeting metabolic pathways.See related article by Karasinska et al., p. 135.

Preclinical Models for Studying the Impact of Macrophages on Cancer Cachexia.

Cancer-associated cachexia is defined by loss of weight and muscle mass, and by the potential loss of adipose tissue accompanied by insulin resistance and increased resting energy expenditure. Cachexia is most prevalent in pancreatic cancer, the third leading cause of cancer-related deaths. While various factors interact to induce cachexia, the precise mechanisms underlying this clinical condition are not fully understood. Clinically relevant animal models of cachexia are needed given the lack of standard diagnostic methods or treatments for this condition. Described in this article are in vitro and in vivo models used to study the role of macrophages in the induction of cachexia in pancreatic cancer. Included are procedures for isolating and culturing bone marrow-derived macrophages, harvesting tumor- and macrophage-derived conditioned medium, and studying the effect of conditioned medium on C2C12 myotubes. Also described are procedures involving the use of an orthotopic model of pancreatic cancer, including a method for examining skeletal muscle atrophy in this model. © 2020 Wiley Periodicals LLC. Basic Protocol 1: In vitro model of pancreatic tumor-induced cachexia using C2C12 cell lines (myotube model) Support Protocol 1: Molecular evaluation of cachectic markers in C2C12 myotubes using real-time PCR and immunoblotting Basic Protocol 2: In vivo model to study cachectic phenotype in pancreatic tumor-bearing mice Support Protocol 2: Evaluation of cachectic markers in the skeletal muscle of tumor-bearing mice.

Local and systemic immunosuppression in pancreatic cancer: Targeting the stalwarts in tumor's arsenal.

Late detection, compromised immune system, and chemotherapy resistance underlie the poor patient prognosis for pancreatic ductal adenocarcinoma (PDAC) patients, making it the 3rd leading cause of cancer-related deaths in the United States. Cooperation between the tumor cells and the immune system leads to the immune escape and eventual establishment of the tumor. For more than 20 years, sincere efforts have been made to intercept the tumor-immune crosstalk and identify the probable therapeutic targets for breaking self-tolerance toward tumor antigens. However, the success of these studies depends on detailed examination and understanding of tumor-immune cell interactions, not only in the primary tumor but also at distant systemic niches. Innate and adaptive arms of the immune system sculpt tumor immunogenicity, where they not only aid in providing an amenable environment for their survival but also act as a driver for tumor relapse at primary or distant organ sites. This review article highlights the key events associated with tumor-immune communication and associated immunosuppression at both local and systemic microenvironments in PDAC. Furthermore, we discuss the approaches and benefits of targeting both local and systemic immunosuppression for PDAC patients. The present articles integrate data from clinical and genetic mouse model studies to provide a widespread consensus on the role of local and systemic immunosuppression in undermining the anti-tumor immune responses against PDAC.