Inflammatory networks and immune surveillance of pancreatic carcinoma

The Immune Revolution: A Case for Priming, Not Checkpoint

Most tumors are unresponsive to immune checkpoint blockade, especially if deep immunosuppression in the tumor develops prior to and prevents T cell immunosurveillance. Failed or frustrated T cell priming often needs repair before successful sensitization to PD-1/PD-L1 blockade. CD40 activation plays a critical role in generating T cell immunity, by activating dendritic cells, and converting cold tumors to hot. In preclinical studies, agonistic CD40 antibodies demonstrate T cell-dependent anti-tumor activity, especially in combination with chemotherapy, checkpoint inhibitory antibodies, and other immune modulators. With the advent of multiple CD40 agonists with acceptable single-agent toxicity, clinical evaluation of CD40 combinations has accelerated.

Crosstalk between Regulatory T Cells and Tumor-Associated Dendritic Cells Negates Anti-tumor Immunity in Pancreatic Cancer

Regulatory T (Treg) cell infiltration constitutes a prominent feature of pancreatic ductal adenocarcinoma (PDA). However, the immunomodulatory function of Treg cells in PDA is poorly understood. Here, we demonstrate that Treg cell ablation is sufficient to evoke effective anti-tumor immune response in early and advanced pancreatic tumorigenesis in mice. This response is dependent on interferon-γ (IFN-γ)-producing cytotoxic CD8⁺ T cells. We show that Treg cells engage in extended interactions with tumor-associated CD11c⁺ dendritic cells (DCs) and restrain their immunogenic function by suppressing the expression of costimulatory ligands necessary for CD8⁺ T cell activation. Consequently, tumor-associated CD8⁺ T cells fail to display effector activities when Treg cell ablation is combined with DC depletion. We propose that tumor-infiltrating Treg cells can promote immune tolerance by suppressing tumor-associated DC immunogenicity. The therapeutic manipulation of this axis might provide an effective approach for the targeting of PDA.

Metabolic Interactions in the Tumor Microenvironment

Tumors are dynamic pseudoorgans that contain numerous cell types interacting to create a unique physiology. Within this network, the malignant cells encounter many challenges and rewire their metabolic properties accordingly. Such changes can be experienced and executed autonomously or through interaction with other cells in the tumor. The focus of this review is on the remodeling of the tumor microenvironment that leads to pathophysiologic interactions that are influenced and shaped by metabolism. They include symbiotic nutrient sharing, nutrient competition, and the role of metabolites as signaling molecules. Examples of such processes abound in normal organismal physiology, and such heterocellular metabolic interactions are repurposed to support tumor metabolism and growth. The importance and ubiquity of these processes are just beginning to be realized, and insights into their role in tumor development and progression are being used to design new drug targets and cancer therapies.

Immune Cytolytic Activity Stratifies Molecular Subsets of Human Pancreatic Cancer

Purpose: Immunotherapy has the potential to improve the dismal prognosis in pancreatic ductal adenocarcinoma (PDA), but clinical trials, including those with single-agent PD-1 or PD-L1 inhibition, have been disappointing. Our aim was to examine the immune landscape of PDA as it relates to aspects of tumor biology, including neoepitope burden.Experimental Design: We used publicly available expression data from 134 primary resection PDA samples from The Cancer Genome Atlas to stratify patients according to a cytolytic T-cell activity expression index. We correlated cytolytic immune activity with mutational, structural, and neoepitope features of the tumor.Results: Human PDA displays a range of intratumoral cytolytic T-cell activity. PDA tumors with low cytolytic activity exhibited significantly increased copy number alterations, including recurrent amplifications of MYC and NOTCH2 and recurrent deletions and mutations of CDKN2A/B In sharp contrast to other tumor types, high cytolytic activity in PDA did not correlate with increased mutational burden or neoepitope load (MHC class I and class II). Cytolytic-high tumors exhibited increased expression of multiple immune checkpoint genes compared to cytolytic-low tumors, except for PD-L1 expression, which was uniformly low.Conclusions: These data identify a subset of human PDA with high cytolytic T-cell activity. Rather than being linked to mutation burden or neoepitope load, immune activation indices in PDA were inversely linked to genomic alterations, suggesting that intrinsic oncogenic processes drive immune inactivity in human PDA. Furthermore, these data highlight the potential importance of immune checkpoints other than PD-L1/PD-1 as therapeutic targets in this lethal disease. Clin Cancer Res; 23(12); 3129-38. ©2016 AACR.

Immunotherapy in pancreatic cancer: Unleash its potential through novel combinations

Pancreatic cancer is the third leading cause of cancer mortality in both men and women in the United States, with poor response to current standard of care, short progression-free and overall survival. Immunotherapies that target cytotoxic T lymphocyte antigen-4, programmed cell death protein-1, and programmed death-ligand 1 checkpoints have shown remarkable activities in several cancers such as melanoma, renal cell carcinoma, and non-small cell lung cancer due to high numbers of somatic mutations, combined with cytotoxic T-cell responses. However, single checkpoint blockade was ineffective in pancreatic cancer, highlighting the challenges including the poor antigenicity, a dense desmoplastic stroma, and a largely immunosuppressive microenvironment. In this review, we will summarize available clinical results and ongoing efforts of combining immune checkpoint therapies with other treatment modalities such as chemotherapy, radiotherapy, and targeted therapy. These combination therapies hold promise in unleashing the potential of immunotherapy in pancreatic cancer to achieve better and more durable clinical responses by enhancing cytotoxic T-cell responses.

Cancer-FOXP3 directly activated CCL5 to recruit FOXP3+Treg cells in pancreatic ductal adenocarcinoma

Forkheadbox protein 3 (FOXP3), initially identified as a key transcription factor for regulatory T cells (Treg cells), was also expressed in many tumors including pancreatic ductal adenocarcinoma (PDAC). However, its role in PDAC progression remains elusive. In this study, we utilized 120 PDAC tissues after radical resection to detect cancer-FOXP3 and Treg cells by immunohistochemistry and evaluated clinical and pathological features of these patients. Cancer-FOXP3 was positively correlated with Treg cells accumulation in tumor tissues derived from PDAC patients. In addition, high cancer-FOXP3 expression was associated with increased tumor volumes and poor prognosis in PDAC especially combined with high levels of Treg cells. Overexpression of cancer-FOXP3 promoted the tumor growth in immunocompetent syngeneic mice but not in immunocompromised or Treg cell-depleted mice. Furthermore, CCL5 was directly trans-activated by cancer-FOXP3 and promoted the recruitment of Treg cells from peripheral blood to the tumor site in vitro and in vivo. This finding has been further reinforced by the evidence that Treg cells recruitment by cancer-FOXP3 was impaired by neutralization of CCL5, thereby inhibiting the growth of PDAC. In conclusion, cancer-FOXP3 serves as a prognostic biomarker and a crucial determinant of immunosuppressive microenvironment via recruiting Treg cells by directly trans-activating CCL5. Therefore, cancer-FOXP3 could be used to select patients with better response to CCL5/CCR5 blockade immunotherapy.

Spatial computation of intratumoral T cells correlates with survival of patients with pancreatic cancer

The exact nature and dynamics of pancreatic ductal adenocarcinoma (PDAC) immune composition remains largely unknown. Desmoplasia is suggested to polarize PDAC immunity. Therefore, a comprehensive evaluation of the composition and distribution of desmoplastic elements and T-cell infiltration is necessary to delineate their roles. Here we develop a novel computational imaging technology for the simultaneous evaluation of eight distinct markers, allowing for spatial analysis of distinct populations within the same section. We report a heterogeneous population of infiltrating T lymphocytes. Spatial distribution of cytotoxic T cells in proximity to cancer cells correlates with increased overall patient survival. Collagen-I and αSMA⁺ fibroblasts do not correlate with paucity in T-cell accumulation, suggesting that PDAC desmoplasia may not be a simple physical barrier. Further exploration of this technology may improve our understanding of how specific stromal composition could impact T-cell activity, with potential impact on the optimization of immune-modulatory therapies.

The functional significance of T-cell infiltration in pancreatic ductal adenocarcinoma in relation to desmoplastic stroma is unclear. Here the authors develop a method to spatially resolve tumour stroma composition and find that spatial T-cell infiltration correlates with patient prognosis regardless of desmoplasia.

Vaccination with poly(IC:LC) and peptide-pulsed autologous dendritic cells in patients with pancreatic cancer

BACKGROUND

Dendritic cells (DCs) enhance the quality of anti-tumor immune response in patients with cancer. Thus, we posit that DC-based immunotherapy, in conjunction with toll-like receptor (TLR)-3 agonist poly-ICLC, is a promising approach for harnessing immunity against metastatic or locally advanced unresectable pancreatic cancer (PC).

METHODS

We generated autologous DCs from the peripheral blood of HLA-A2⁺ patients with PC. DCs were pulsed with three distinct A2-restricted peptides: 1) human telomerase reverse transcriptase (hTERT, TERT572Y), 2) carcinoembryonic antigen (CEA; Cap1-6D), and 3) survivin (SRV.A2). Patients received four intradermal injections of 1 × 10⁷ peptide-pulsed DC vaccines every 2 weeks (Day 0, 14, 28, and 42). Concurrently, patients received intramuscular administration of Poly-ICLC at 30 μg/Kg on vaccination days (i.e., day 0, 14, 28, and 42), as well as on days 3, 17, 21, 31, 37, and 45. Our key objective was to assess safety and feasibility. The effect of DC vaccination on immune response was measured at each DC injection time point by enumerating the phenotype and function of patient T cells.

RESULTS

Twelve patients underwent apheresis: nine patients with metastatic disease, and three patients with locally advanced unresectable disease. Vaccines were successfully manufactured from all individuals. We found that this treatment was well-tolerated, with the most common symptoms being fatigue and/or self-limiting flu-like symptoms. Among the eight patients who underwent imaging on day 56, four patients experienced stable disease while four patients had disease progression. The median overall survival was 7.7 months. One patient survived for 28 months post leukapheresis. MHC class I -tetramer analysis before and after vaccination revealed effective generation of antigen-specific T cells in three patients with stable disease.

CONCLUSION

Vaccination with peptide-pulsed DCs in combination with poly-ICLC is safe and induces a measurable tumor specific T cell population in patients with advanced PC.

TRIAL REGISTRATION

NCT01410968 ; Name of registry: clinicaltrials.gov; Date of registration: 08/04/2011).

Bromodomain inhibitors, JQ1 and I-BET 762, as potential therapies for pancreatic cancer

Bromodomain inhibitors (JQ1 and I-BET 762) are a new generation of selective, small molecule inhibitors that target BET (bromodomain and extra terminal) proteins. By impairing their ability to bind to acetylated lysines on histones, bromodomain inhibitors interfere with transcriptional initiation and elongation. BET proteins regulate several genes responsible for cell cycle, apoptosis and inflammation. In this study, JQ1 and I-BET 762 decreased c-Myc and p-Erk 1/2 protein levels and inhibited proliferation in pancreatic cancer cells. The tumor microenvironment is known to play an important role in pancreatic cancer, and these drugs suppressed the production of nitric oxide and a variety of inflammatory cytokines, including IL-6, CCL2, and GM-CSF, in both immune and pancreatic cancer cells in vitro. Notably, the bromodomain inhibitors also reduced protein levels of p-Erk 1/2 and p-STAT3 in mouse models of pancreatic cancer. All of these proteins are essential for tumor promotion, progression and metastasis. In conclusion, the bromodomain inhibitors JQ1 and I-BET 762 targeted and suppressed multiple pathways in pancreatic cancer. I-BET 762 and a number of other bromodomain inhibitors are currently being tested in several clinical trials, making them potentially promising drugs for the treatment of pancreatic cancer, an often-fatal disease.

De-Risking Immunotherapy: Report of a Consensus Workshop of the Cancer Immunotherapy Consortium of the Cancer Research Institute

With the recent FDA approvals of pembrolizumab and nivolumab, and a host of additional immunomodulatory agents entering clinical development each year, the field of cancer immunotherapy is changing rapidly. Strategies that can assist researchers in choosing the most promising drugs and drug combinations to move forward through clinical development are badly needed in order to reduce the likelihood of late-stage clinical trial failures. On October 5, 2014, the Cancer Immunotherapy Consortium of the Cancer Research Institute, a collaborative think tank composed of stakeholders from academia, industry, regulatory agencies, and patient interest groups, met to discuss strategies for de-risking immunotherapy development, with a focus on integrating preclinical and clinical studies, and conducting smarter early-phase trials, particularly for combination therapies. Several recommendations were made, including making better use of clinical data to inform preclinical research, obtaining adequate tissues for biomarker studies, and choosing appropriate clinical trial endpoints to identify promising drug candidates and combinations in nonrandomized early-phase trials.

Dual prognostic significance of tumour-associated macrophages in human pancreatic adenocarcinoma treated or untreated with chemotherapy

OBJECTIVE

Tumour-associated macrophages (TAMs) play key roles in tumour progression. Recent evidence suggests that TAMs critically modulate the efficacy of anticancer therapies, raising the prospect of their targeting in human cancer.

DESIGN

In a large retrospective cohort study involving 110 patients with pancreatic ductal adenocarcinoma (PDAC), we assessed the density of CD68-TAM immune reactive area (%IRA) at the tumour-stroma interface and addressed their prognostic relevance in relation to postsurgical adjuvant chemotherapy (CTX). In vitro, we dissected the synergism of CTX and TAMs.

RESULTS

In human PDAC, TAMs predominantly exhibited an immunoregulatory profile, characterised by expression of scavenger receptors (CD206, CD163) and production of interleukin 10 (IL-10). Surprisingly, while the density of TAMs associated to worse prognosis and distant metastasis, CTX restrained their protumour prognostic significance. High density of TAMs at the tumour-stroma interface positively dictated prognostic responsiveness to CTX independently of T-cell density. Accordingly, in vitro, gemcitabine-treated macrophages became tumoricidal, activating a cytotoxic gene expression programme, inhibiting their protumoural effect and switching to an antitumour phenotype. In patients with human PDAC, neoadjuvant CTX was associated to a decreased density of CD206(+) and IL-10(+) TAMs at the tumour-stroma interface.

CONCLUSIONS

Overall, our data highlight TAMs as critical determinants of prognostic responsiveness to CTX and provide clinical and in vitro evidence that CTX overall directly re-educates TAMs to restrain tumour progression. These results suggest that the quantification of TAMs could be exploited to select patients more likely to respond to CTX and provide the basis for novel strategies aimed at re-educating macrophages in the context of CTX.

The triterpenoid CDDO-imidazolide reduces immune cell infiltration and cytokine secretion in the KrasG12D;Pdx1-Cre (KC) mouse model of pancreatic cancer

Because the 5-year survival rate for pancreatic cancer remains under 10%, new drugs are needed for the prevention and treatment of this devastating disease. Patients with chronic pancreatitis have a 12-fold higher risk of developing pancreatic cancer. LSL-Kras^G12D/+;Pdx-1-Cre (KC) mice replicate the genetics, symptoms and histopathology found in human pancreatic cancer. Immune cells infiltrate into the pancreas of these mice and produce inflammatory cytokines that promote tumor growth. KC mice are particularly sensitive to the effects of lipopolysaccharide (LPS), as only 48% of KC mice survived an LPS challenge while 100% of wildtype (WT) mice survived. LPS also increased the percentage of CD45+ immune cells in the pancreas and immunosuppressive Gr1+ myeloid-derived suppressor cell in the spleen of these mice. The triterpenoid CDDO-imidazolide (CDDO-Im) not only reduced the lethal effects of LPS (71% survival) but also decreased the infiltration of CD45+ cells into the pancreas and the percentage of Gr1+ myeloid-derived suppressor cell in the spleen of KC mice 4-8 weeks after the initial LPS challenge. While the levels of inflammatory cytokine levels were markedly higher in KC mice versus WT mice challenged with LPS, CDDO-Im significantly decreased the production of IL-6, CCL-2, vascular endothelial growth factor and G-CSF in the KC mice. All of these cytokines are prognostic markers in pancreatic cancer or play important roles in the progression of this disease. Disrupting the inflammatory process with drugs such as CDDO-Im might be useful for preventing pancreatic cancer, especially in high-risk populations.

Lack of immunoediting in murine pancreatic cancer reversed with neoantigen

In carcinogen-driven cancers, a high mutational burden results in neoepitopes that can be recognized immunologically. Such carcinogen-induced tumors may evade this immune response through "immunoediting," whereby tumors adapt to immune pressure and escape T cell-mediated killing. Many tumors lack a high neoepitope burden, and it remains unclear whether immunoediting occurs in such cases. Here, we evaluated T cell immunity in an autochthonous mouse model of pancreatic cancer and found a low mutational burden, absence of predicted neoepitopes derived from tumor mutations, and resistance to checkpoint immunotherapy. Spontaneous tumor progression was identical in the presence or absence of T cells. Moreover, tumors arising in T cell-depleted mice grew unchecked in immune-competent hosts. However, introduction of the neoantigen ovalbumin (OVA) led to tumor rejection and T cell memory, but this did not occur in OVA immune-tolerant mice. Thus, immunoediting does not occur in this mouse model - a likely consequence, not a cause, of absent neoepitopes. Because many human tumors also have a low missense mutational load and minimal neoepitope burden, our findings have clinical implications for the design of immunotherapy for patients with such tumors.

Metabolic plasticity in heterogeneous pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is one of the most lethal malignant neoplasms. The recognized hallmarks of PDA are regarded to be downstream events of metabolic reprogramming. Because PDA is a heterogeneous disease that is influenced by genetic polymorphisms and changes in the microenvironment, metabolic plasticity is a novel feature of PDA. As intrinsic factors for metabolic plasticity, K-ras activation and mutations in other tumor suppressor genes induce abnormal mitochondrial metabolism and enhance glycolysis, with alterations in glutamine and lipid metabolism. As extrinsic factors, the acidic and oxygen/nutrient-deprived microenvironment also induces cancer cells to reprogram their metabolic pathway and hijack stromal cells (mainly cancer-associated fibroblasts and immunocytes) to communicate, thereby adapting to metabolic stress. Therefore, a better understanding of the metabolic features of PDA will contribute to the development of novel diagnostic and therapeutic strategies.

Pancreatic cancer biology and genetics from an evolutionary perspective

Cancer is an evolutionary disease, containing the hallmarks of an asexually reproducing unicellular organism subject to evolutionary paradigms. Pancreatic ductal adenocarcinoma (hereafter referred to as pancreatic cancer) is a particularly robust example of this phenomenon. Genomic features indicate that pancreatic cancer cells are selected for fitness advantages when encountering the geographic and resource-depleted constraints of the microenvironment. Phenotypic adaptations to these pressures help disseminated cells to survive in secondary sites, a major clinical problem for patients with this disease. In this Review we gather the wide-ranging aspects of pancreatic cancer research into a single concept rooted in Darwinian evolution, with the goal of identifying novel insights and opportunities for study.

AID-expressing epithelium is protected from oncogenic transformation by an NKG2D surveillance pathway

Activation-induced deaminase (AID) initiates secondary antibody diversification in germinal center B cells, giving rise to higher affinity antibodies through somatic hypermutation (SHM) or to isotype-switched antibodies through class switch recombination (CSR). SHM and CSR are triggered by AID-mediated deamination of cytosines in immunoglobulin genes. Importantly, AID activity in B cells is not restricted to Ig loci and can promote mutations and pro-lymphomagenic translocations, establishing a direct oncogenic mechanism for germinal center-derived neoplasias. AID is also expressed in response to inflammatory cues in epithelial cells, raising the possibility that AID mutagenic activity might drive carcinoma development. We directly tested this hypothesis by generating conditional knock-in mouse models for AID overexpression in colon and pancreas epithelium. AID overexpression alone was not sufficient to promote epithelial cell neoplasia in these tissues, in spite of displaying mutagenic and genotoxic activity. Instead, we found that heterologous AID expression in pancreas promotes the expression of NKG2D ligands, the recruitment of CD8⁺ T cells, and the induction of epithelial cell death. Our results indicate that AID oncogenic potential in epithelial cells can be neutralized by immunosurveillance protective mechanisms.

KRAS Mutant Pancreatic Cancer: No Lone Path to an Effective Treatment

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest cancers with a dismal 7% 5-year survival rate and is projected to become the second leading cause of cancer-related deaths by 2020. KRAS is mutated in 95% of PDACs and is a well-validated driver of PDAC growth and maintenance. However, despite comprehensive efforts, an effective anti-RAS drug has yet to reach the clinic. Different paths to inhibiting RAS signaling are currently under investigation in the hope of finding a successful treatment. Recently, direct RAS binding molecules have been discovered, challenging the perception that RAS is an “undruggable” protein. Other strategies currently being pursued take an indirect approach, targeting proteins that facilitate RAS membrane association or downstream effector signaling. Unbiased genetic screens have identified synthetic lethal interactors of mutant RAS. Most recently, metabolic targets in pathways related to glycolytic signaling, glutamine utilization, autophagy, and macropinocytosis are also being explored. Harnessing the patient’s immune system to fight their cancer is an additional exciting route that is being considered. The “best” path to inhibiting KRAS has yet to be determined, with each having promise as well as potential pitfalls. We will summarize the state-of-the-art for each direction, focusing on efforts directed toward the development of therapeutics for pancreatic cancer patients with mutated KRAS.

Role of tumor associated macrophages in regulating pancreatic cancer progression

Pancreatic cancer has an overall 5-year survival rate of less than 5%. Unfortunately, patient survival has not substantially improved in the last couple of decades despite advances in treatment modalities that have been successful in other cancer types. The poor response of pancreatic cancer to therapy is a major obstacle faced by clinicians. Increasing attention is being paid to how tumor cells and non-tumor cells influence each other in the pancreatic tumor microenvironment. Tumor-associated macrophages (TAMs) are a highlight in this field because of their vast presence in the tumor microenvironment. TAMs promote angiogenesis, metastasis, and suppress the anti-tumor immune response. Here we review the current understanding of the role of TAMs in regulating the progression of pancreatic cancer.

From bench to bedside a comprehensive review of pancreatic cancer immunotherapy

The incidence of pancreatic cancer has been increasing while its 5-year survival rate has not changed in decades. In the era of personalized medicine, immunotherapy has emerged as a promising treatment modality in a variety of malignancies, including pancreatic cancer. This review will discuss the unique pancreatic tumor microenvironment, including the cells and receptors that transform the pancreas from its normal architecture into a complex mix of suppressor immune cells and dense extracellular matrix that allows for the unrestricted growth of cancer cells. Next, we will highlight the recently completed immunotherapy clinical trials in pancreatic cancer. Finally, we will explore the on-going immunotherapy clinical trials and future directions of this engaging and changing field.

Transcriptional repression of SOCS3 mediated by IL-6/STAT3 signaling via DNMT1 promotes pancreatic cancer growth and metastasis

BACKGROUND

Previous studies have investigated the sustained aberrantly activated Interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) signaling pathway is crucial for pancreatic cancer growth and metastasis. Suppressor of cytokine signaling 3 (SOCS3), as a key negative feedback regulator of this signaling pathway, is usually down-regulated in various cancers. In the present study, we aim at exploring the biological function and the underlying molecular regulation mechanisms of SOCS3 in pancreatic cancer.

METHODS

The expression of SOCS3 and other genes in pancreatic cancer was examined by Quantitative real-time PCR, western blotting and immunohistochemical staining. The interaction between pSTAT3 and DNA Methyltransferase 1 (DNMT1) was investigated by co-immunoprecipitation assay. Luciferase reporter assay was used to investigate the transcriptional regulation of pSTAT3 and DNMT1 on the SOCS3 gene. The effects of SOCS3 on the biological behavior of pancreatic cancer cells were assessed both in vitro and vivo. Furthermore, we performed a comprehensive analysis of the expression of SOCS3 in a pancreatic cancer tissue microarray (TMA) and correlated our findings with pathological parameters and outcomes of the patients.

RESULTS

We showed that SOCS3 expression was decreased in phosphorylated STAT3 (pSTAT3)-positive tumors and was negatively correlated with pSTAT3 in pancreatic cancer cells. We also found that IL-6/STAT3 promoted SOCS3 promoter hypermethylation by increasing DNMT1 activity; silencing DNMT1 or 5-aza-2-deoxycytidine (5-AZA) treatment could reverse the down-regulation of SOCS3 mediated by IL-6. Using co-immunoprecipitation and luciferase reporter assays, we found that STAT3 recruited DNMT1 to the promoter region of SOCS3 and inhibited its transcriptional activity. Overexpression of SOCS3 significantly inhibited cell proliferation, which may be due to the increase in G1-S phase arrest; overexpression of SOCS3 also inhibited cell migration and invasion as well as tumorigenicity in nude mice. Pancreatic cancer tissue microarray analysis showed that high SOCS3 expression was a good prognostic factor and negatively correlated with tumor volume and metastasis.

CONCLUSION

We demonstrated that activated IL-6/STAT3 signaling could induce SOCS3 methylation via DNMT1, which led to pancreatic cancer growth and metastasis. These data also provided a mechanistic link between sustained aberrantly activated IL-6/STAT3 signaling and SOCS3 down-regulation in pancreatic cancer. Thus, inhibitors of STAT3 or DNMT1 may become novel strategies for treating pancreatic cancer.

Pancreatic cancer, treatment options, and GI-4000

Although pancreatic cancer is but the eleventh most prevalent cancer in the US, it is predicted that of all the patients newly diagnosed with this disease in 2014, only 27% will still be alive at the end of the first year, which is reduced to 6% after 5 years. The choice of chemotherapy in the treatment of pancreatic cancer is dependent on disease stage and patient performance status but, in general, the most widely used approved regimens include 5-fluorouracil (5-FU) combinations and gemcitabine combinations. Recent therapeutic strategies have resulted in an improvement in survival of patients with pancreatic cancer but the magnitude of change is disappointing and vast improvements are still needed. The goal of immunotherapy is to enhance and guide the body's immune system to recognize tumor-specific antigens and mount an attack against the disease. Among newer immune therapies, GI-4000 consists of 4 different targeted molecular immunogens, each containing a different Ras protein (antigen) encoded by the most commonly found mutant RAS genes in solid tumors-RAS mutations exist in over 90% of pancreatic ductal adenocarcinomas. We will review pancreatic cancer epidemiology and its current treatment options, and consider the prospects of immunotherapy, focusing on GI-4000. We discuss the potential mechanism of action of GI-4000, and the performance of this vaccination series thus far in early phase clinical trials.

A Novel Immunocompetent Mouse Model of Pancreatic Cancer with Robust Stroma: a Valuable Tool for Preclinical Evaluation of New Therapies

A valid preclinical tumor model should recapitulate the tumor microenvironment. Immune and stromal components are absent in immunodeficient models of pancreatic cancer. While these components are present in genetically engineered models such as Kras(G12D); Trp53(R172H); Pdx-1Cre (KPC), immense variability in development of invasive disease makes them unsuitable for evaluation of novel therapies. We have generated a novel mouse model of pancreatic cancer by implanting tumor fragments from KPC mice into the pancreas of wild type mice. Three-millimeter tumor pieces from KPC mice were implanted into the pancreas of C57BL/6J mice. Four to eight weeks later, tumors were harvested, and stromal and immune components were evaluated. The efficacy of Minnelide, a novel compound which has been shown to be effective against pancreatic cancer in a number of preclinical murine models, was evaluated. In our model, consistent tumor growth and metastases were observed. Tumors demonstrated intense desmoplasia and leukocytic infiltration which was comparable to that in the genetically engineered KPC model and significantly more than that observed in KPC tumor-derived cell line implantation model. Minnelide treatment resulted in a significant decrease in the tumor weight and volume. This novel model demonstrates a consistent growth rate and tumor-associated mortality and recapitulates the tumor microenvironment. This convenient model is a valuable tool to evaluate novel therapies.

Pancreatic Cancer Metabolism: Breaking It Down to Build It Back Up

How do cancer cells escape tightly controlled regulatory circuits that link their proliferation to extracellular nutrient cues? An emerging theme in cancer biology is the hijacking of normal stress response mechanisms to enable growth even when nutrients are limiting. Pancreatic ductal adenocarcinoma (PDA) is the quintessential aggressive malignancy that thrives in nutrient-poor, hypoxic environments. PDAs overcome these limitations through appropriation of unorthodox strategies for fuel source acquisition and utilization. In addition, the interplay between evolving PDA and whole-body metabolism contributes to disease pathogenesis. Deciphering how these pathways function and integrate with one another can reveal novel angles of therapeutic attack.

SIGNIFICANCE

Alterations in tumor cell and systemic metabolism are central to the biology of pancreatic cancer. Further investigation of these processes will provide important insights into how these tumors develop and grow, and suggest new approaches for its detection, prevention, and treatment.

Spatial distribution of B cells predicts prognosis in human pancreatic adenocarcinoma

B-cell responses are emerging as critical regulators of cancer progression. In this study, we investigated the role of B lymphocytes in the microenvironment of human pancreatic ductal adenocarcinoma (PDAC), in a retrospective consecutive series of 104 PDAC patients and in PDAC preclinical models. Immunohistochemical analysis revealed that B cells occupy two histologically distinct compartments in human PDAC, either scatteringly infiltrating (CD20-TILs), or organized in tertiary lymphoid tissue (CD20-TLT). Only when retained within TLT, high density of B cells predicted longer survival (median survival 16.9 mo CD20-TLT^hi vs. 10.7 mo CD20-TLT^lo; p = 0.0085). Presence of B cells within TLT associated to a germinal center (GC) immune signature, correlated with CD8-TIL infiltration, and empowered their favorable prognostic value. Immunotherapeutic vaccination of spontaneously developing PDAC (Kras^G12D-Pdx1-Cre) mice with α-enolase (ENO1) induced formation of TLT with active GCs and correlated with increased recruitment of T lymphocytes, suggesting induction of TLT as a strategy to favor mobilization of immune cells in PDAC. In contrast, in an implanted tumor model devoid of TLT, depletion of B cells with an anti-CD20 antibody reinstated an antitumor immune response. Our results highlight B cells as an essential element of the microenvironment of PDAC and identify their spatial organization as a key regulator of their antitumor function. A mindfully evaluation of B cells in human PDAC could represent a powerful prognostic tool to identify patients with distinct clinical behaviors and responses to immunotherapeutic strategies.

Perspectives in the treatment of pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an incurable lethal disease whose incidence rate is growing. There is no effective screening for detection of early stage tumors and, in most cases, PDAC is diagnosed at advanced disease stages, when radical pancreatic resection is not possible. The aggressive nature of pancreatic tumor cells lies in the complex genetic mechanisms behind their uncontrolled capability to grow and metastasize, which involve essential adaptive changes in cellular metabolism, signaling, adhesion and immunoediting. In addition, PDAC cells promote a dense functional stroma that facilitates tumor resistance to chemotherapy and radiation. During the last two decades, gemcitabine has been the reference for the systemic treatment of PDAC. However, recently, a regimen combining fluorouracil, irinotecan, oxaliplatin, and leucovorin (FOLFIRINOX) and another combining albumin-bound paclitaxel with gemcitabine have shown clear therapeutic advantage in advanced PDAC, with survival outcomes of 11.3 and 8.5 mo on phase III trials, respectively, over single-agent gemcitabine. With the pending issue of their higher toxicities, these regimens set the reference for ongoing and future clinical studies in advanced PDAC. In addition, the efficacy of oral fluoropyrimidine (S-1) has been well documented in Asiatic PDAC patients. The development of therapeutic approaches other than cytotoxic drugs has proven difficult in the past, with only one drug (erlotinib) approved to date. Besides, a number of agents targeting signaling pathways in tumor or stroma cells are being investigated. Likewise, immunotherapies that target PDAC in various ways are the subject of a number of clinical trials. The search for reliable biomarkers with diagnostic and prognostic value using genomics and mass spectrometry methods may facilitate monitoring and refinement of therapies. This review focuses on current understanding of the pathogenesis of PDAC and the latest developments in the treatment of advanced PDAC.

State of the art and future directions of pancreatic ductal adenocarcinoma therapy

Pancreatic ductal adenocarcinoma (PDAC) is expected to become the second cause of cancer-related death in 2030. PDAC is the poorest prognostic tumor of the digestive tract, with 80% of patients having advanced disease at diagnosis and 5-year survival rate not exceeding 7%. Until 2010, gemcitabine was the only validated therapy for advanced PDAC with a modest improvement in median overall survival as compared to best supportive care (5-6 vs 3 months). Multiple phase II-III studies have used various combinations of gemcitabine with other cytotoxics or targeted agents, most in vain, in attempt to improve this outcome. Over the past few years, the landscape of PDAC management has undergone major and rapid changes with the approval of the FOLFIRINOX and gemcitabine plus nab-paclitaxel regimens in patients with metastatic disease. These two active combination chemotherapy options yield an improved median overall survival (11.1 vs 8.5 months, respectively) thus making longer survival a reasonably achievable goal. This breakthrough raises some new clinical questions about the management of PDAC. Moreover, better knowledge of the environmental and genetic events that underpin multistep carcinogenesis and of the microenvironment surrounding cancer cells in PDAC has open new perspectives and therapeutic opportunities. In this new dynamic context of deep transformation in basic research and clinical management aspects of the disease, we gathered updated preclinical and clinical data in a multifaceted review encompassing the lessons learned from the past, the yet unanswered questions, and the most promising research priorities to be addressed for the next 5 years.

Genetics and Biology of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma remains a clinical challenge. Thus far, enlightenment on the downstream activities of Kras, the tumor's unique metabolic needs, and how the stroma and immune system affect it have remained untranslated to the clinical practice. Given the numbers of diverse therapies in development and a growing knowledge about how to evaluate these systems preclinically and clinically, this is expected to change significantly and for the better over the next 5 years.

Control of CD8 T-Cell Infiltration into Tumors by Vasculature and Microenvironment

CD8 T-cells are a critical brake on the initial development of tumors. In established tumors, the presence of CD8 T-cells is correlated with a positive patient prognosis, although immunosuppressive mechanisms limit their effectiveness and they are rarely curative without manipulation. Cancer immunotherapies aim to shift the balance back to dominant antitumor immunity through antibody blockade of immunosuppressive signaling pathways, vaccination, and adoptive transfer of activated or engineered T-cells. These approaches have yielded striking responses in small subsets of patients with solid tumors, most notably those with melanoma. Importantly, the subset of patients who respond to vaccination or immunosuppression blockade therapies are those with CD8 T-cells present in the tumor prior to initiating therapy. While current adoptive cell therapy approaches can be dramatically effective, they require infusion of extremely large numbers of T-cells, but the number that actually infiltrates the tumor is very small. Thus, poor representation of CD8 T-cells in tumors is a fundamental hurdle to successful immunotherapy, over and above the well-established barrier of immunosuppression. In this review, we discuss the factors that determine whether immune cells are present in tumors, with a focus on the representation of cytotoxic CD8 T-cells. We emphasize the critically important role of tumor-associated vasculature as a gateway that enables the active infiltration of both effector and naïve CD8 T-cells that exert antitumor activity. We also discuss strategies to enhance the gateway function and extend the effectiveness of immunotherapies to a broader set of cancer patients.

Immune Therapy in GI Malignancies: A Review

The balance between tumor-promoting and tumor-suppressing immune responses and the difference between them ultimately determine whether a cancer escapes immune recognition mechanisms. Defining the complex relationships between the tumor itself, the tumor environment, and the immune system has been critical in facilitating the development of successful immunotherapies. This review explores the role of oncogenes in inducing cancer-associated inflammation, the local and systemic factors that lead to immune suppression, and immunotherapy approaches to overcome immune privilege.

Induction of T-cell Immunity Overcomes Complete Resistance to PD-1 and CTLA-4 Blockade and Improves Survival in Pancreatic Carcinoma

Disabling the function of immune checkpoint molecules can unlock T-cell immunity against cancer, yet despite remarkable clinical success with monoclonal antibodies (mAb) that block PD-1 or CTLA-4, resistance remains common and essentially unexplained. To date, pancreatic carcinoma is fully refractory to these antibodies. Here, using a genetically engineered mouse model of pancreatic ductal adenocarcinoma in which spontaneous immunity is minimal, we found that PD-L1 is prominent in the tumor microenvironment, a phenotype confirmed in patients; however, tumor PD-L1 was found to be independent of IFNγ in this model. Tumor T cells expressed PD-1 as prominently as T cells from chronically infected mice, but treatment with αPD-1 mAbs, with or without αCTLA-4 mAbs, failed in well-established tumors, recapitulating clinical results. Agonist αCD40 mAbs with chemotherapy induced T-cell immunity and reversed the complete resistance of pancreatic tumors to αPD-1 and αCTLA-4. The combination of αCD40/chemotherapy plus αPD-1 and/or αCTLA-4 induced regression of subcutaneous tumors, improved overall survival, and conferred curative protection from multiple tumor rechallenges, consistent with immune memory not otherwise achievable. Combinatorial treatment nearly doubled survival of mice with spontaneous pancreatic cancers, although no cures were observed. Our findings suggest that in pancreatic carcinoma, a nonimmunogenic tumor, baseline refractoriness to checkpoint inhibitors can be rescued by the priming of a T-cell response with αCD40/chemotherapy.

Rosmarinic acid potentiates ATRA-induced macrophage differentiation in acute promyelocytic leukemia NB4 cells

Rosmarinic acid (RA, an ester of caffeic acid and 3,4-dihydroxyphenyllactic acid) has a number of biological activities, but little is known about anti-leukemic activities of RA combined with all-trans retinoic acid (ATRA) against acute promyelocytic leukemia (APL) cells. We examined the differentiation marker, CD11b, in bone marrow cells (BMC) of an APL patient, in NB4 cells (APL cell line), and in normal BMC and peripheral blood mononuclear cells (PBMC) of healthy subjects by flow cytometric analysis. ATRA/RA induced expression of CD11b in the BMC of the APL patient and in NB4 cells, but not in normal BMC or PBMC. Therefore, we realized that RA potentiated ATRA-induced macrophage differentiation in APL cells. Further characterization of the induced macrophages showed that they exhibited morphological changes and were able to phagocytose and generate reactive oxygen species. Th also had typical expression of C-C chemokine receptor type 1 (CCR1), CCR2, and intercellular adhesion molecule-1 (ICAM-1). Moreover, the expression of CD11b(+) and CD14(+) cells depended on ERK-NF-κB axis activation. Together, these results indicate that RA potentiates ATRA-induced macrophage differentiation in APL cells. Thus, RA may play an important role as an appurtenant differentiation agent for functional macrophage differentiation in APL. Additionally, the differentiated macrophages might have a normal life span and, they could die. These data indicate that co-treatment with RA and ATRA has potential as an anti-leukemic therapy in APL.

PD-1/PD-L1 blockade together with vaccine therapy facilitates effector T-cell infiltration into pancreatic tumors

Pancreatic ductal adenocarcinoma (PDA) has a poor prognosis due to late detection and resistance to conventional therapies. Published studies show that the PDA tumor microenvironment is predominantly infiltrated with immune suppressive cells and signals that if altered, would allow effective immunotherapy. However, single-agent checkpoint inhibitors including agents that alter immune suppressive signals in other human cancers such as cytotoxic T-lymphocyte antigen 4 (CTLA-4), programmed death 1 (PD-1), and its ligand PD-L1, have failed to demonstrate objective responses when given as single agents to PDA patients. We recently reported that inhibition of the CTLA-4 pathway when given together with a T cell inducing vaccine gives objective responses in metastatic PDA patients. In this study, we evaluated blockade of the PD-1/PD-L1 pathway. We found that PD-L1 is weakly expressed at a low frequency in untreated human and murine PDAs but treatment with a granulocyte macrophage colony-stimulating factor secreting PDA vaccine (GVAX) significantly upregulates PD-L1 membranous expression after treatment of tumor-bearing mice. In addition, combination therapy with vaccine and PD-1 antibody blockade improved murine survival compared with PD-1 antibody monotherapy or GVAX therapy alone. Furthermore, PD-1 blockade increased effector CD8 T lymphocytes and tumor-specific interferon-γ production of CD8 T cells in the tumor microenvironment. Immunosuppressive pathways, including regulatory T cells and CTLA-4 expression on T cells were overcome by the addition of vaccine and low-dose cyclophosphamide to PD-1 blockade. Collectively, our study supports combining PD-1 or PD-L1 antibody therapy with a T cell inducing agent for PDA treatment.

Serum cytokine profile in patients with pancreatic cancer

OBJECTIVE

Pancreatic ductal adenocarcinoma is a deadly disease because of late diagnosis and chemoresistance. We aimed to find a panel of serum cytokines representing diagnostic and predictive biomarkers for pancreatic cancer.

METHODS

A cytokine antibody array was performed to simultaneously identify 507 cytokines in sera of patients with pancreatic cancer and healthy controls. The nonparametric Mann-Whitney U test was used to pairwise compare the controls, the pretreated patients, and the posttreated patients. Fold changes greater than or equal to 1.5 or less than or equal to 1/1.5 were considered significant. Receiver operating characteristic curves were used to assess the performance of the model. A leave-one-out cross-validation was used for estimating prediction error.

RESULTS

Comparing the sera of pretreated patients against the control samples, the cytokines fibroblast growth factor 10 (FGF-10/keratinocyte growth factor-2 (KGF-2), chemokine (C-X-C motif) ligand 11 interferon inducible T cell alpha chemokine (I-TAC)/chemokine [C-X-C motif] ligand 11 (CXCL11), oncostatin M (OSM), osteoactivin/glycoprotein nonmetastatic melanoma protein B, and stem cell factor (SCF) were found significantly overexpressed. Besides, the cytokines CD30 ligand/tumor necrosis factor superfamily, member 8 (TNFSF8), chordin-like 2, FGF-10/KGF-2, growth/differentiation factor 15, I-TAC/CXCL11, OSM, and SCF were differentially expressed in response to treatment.

CONCLUSIONS

We propose a role for FGF-10/KGF-2, I-TAC/CXCL11, OSM, osteoactivin/glycoprotein nonmetastatic melanoma protein B, and SCF as novel diagnostic biomarkers. CD30 ligand/TNFSF8, chordin-like 2, FGF-10/KGF-2, growth/differentiation factor 15, I-TAC/CXCL11, OSM, and SCF might represent as predictive biomarkers for gemcitabine and erlotinib response of patients with pancreatic cancer.

Immune-based therapies in pancreatic and colorectal cancers and biomarkers of responsiveness

Immune-based strategies are the most promising treatments to improve cancer disease control. Early clinical trials are ongoing to test the safety and feasibility of immune-based therapies for gastrointestinal cancers. However, to date, immunotherapy has been only an experimental option for these diseases and a better understanding of their molecular, cellular, structural and clinical dissimilarities is crucial in the generation of tailored immunotherapeutic treatments. In this review, we will summarize the key mechanisms that regulate the action of immune system in cancer and the different immune-based approaches aimed at improving disease control in patients with advanced disease. We will then move on to discussing the current immunotherapeutic approaches in two types of gastrointestinal (colo-rectal and pancreatic) cancers, whose immune microenvironment has been lately object of intense analyses and has emerged as an important determinant of clinical outcome.

The pancreatic cancer microenvironment: an immunologic battleground

Recent studies of human pancreatic cancer challenge the mouse model-derived notion that the pancreas is a site of immune privilege. A heavy infiltration of CD8⁺ T cells expressing programmed cell death 1 (PD-1) and smaller numbers of myeloid cells and regulatory T cells provides rationale for the clinical evaluation of immune checkpoint inhibition as a pancreatic cancer therapeutic strategy.

Interleukin-6: a villain in the drama of pancreatic cancer development and progression

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a devastating malignancy with a poor prognosis and little treatment options. The development and progression of the disease is fostered by inflammatory cells and cytokines. One of these cytokines is interleukin-6 (IL-6), which plays an important role in a wide range of biologic activities.

DATA SOURCES

A systematic search of PubMed was performed to identify relevant studies using key words such as interleukin-6, inflammatory cytokines, inflammation and pancreatic cancer or PDAC. Articles related to IL-6 and pancreatic cancer were systematically reviewed.

RESULTS

IL-6 is elevated in the serum of pancreatic cancer patients and correlates with cachexia, advanced tumor stage and poor survival. Its expression is enhanced by hypoxia and proteins involved in pancreatic cancer development like Kras, mesothelin or ZIP4. IL-6 in turn contributes to the generation of a pro-tumorigenic microenvironment and is probably involved in angiogenesis and metastasis. In experimental mouse models of PDAC, IL-6 was important for the development and progression of precursor lesions.

CONCLUSION

IL-6 emerges as a key player in pancreatic cancer development and progression, and hence should be considered as a new therapeutic target.

Specificity delivers: therapeutic role of tumor antigen-specific antibodies in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) is among the most deadly cancers with less than 5% of the patients living beyond 5 years post-diagnosis. Lack of early diagnostic biomarkers and resistance to current therapies help explain these disappointing numbers. Thus, more effective and better-targeted therapies are needed quickly. Monoclonal antibodies offer an attractive alternative targeted therapy option for PDA because they are highly specific and potent. However, currently available monoclonal antibody therapies for PDA are still in their infancy with a low success rate and low likelihood of being approved. The challenges faced by these therapies include the following: lack of predictive and response biomarkers, unfavorable safety profiles, expression of targets not restricted to the cancer cells, flawed preclinical model systems, drug resistance, and PDA's complex nature. Additionally, discovery of novel PDA-specific antigen targets, present on the cell surface or in the extracellular matrix, is needed. Predictive and response markers also need to be determined for PDA patient subgroups so that the most appropriate effective therapy can be delivered. Serologic approaches, recombinant antibody-producing technologies, and advances in antibody engineering techniques will help to identify these predictive biomarkers and aid in the development of new therapeutic antibodies. A combinatorial approach simultaneously targeting antigens on the PDA cell, stroma, and immunosuppressive cells should be employed.

Pancreatic ductal adenocarcinoma contains an effector and regulatory immune cell infiltrate that is altered by multimodal neoadjuvant treatment

Objective

The immune response to pancreatic ductal adenocarcinoma (PDA) may play a role in defining its uniquely aggressive biology; therefore, we sought to clearly define the adaptive immune infiltrate in PDA.

Design

We used immunohistochemistry and flow cytometry to characterize the immune infiltrate in human PDA and compared our findings to the patients’ peripheral blood.

Results

In contrast to the myeloid cell predominant infiltrate seen in murine models, T cells comprised the majority of the hematopoietic cell component of the tumor stroma in human PDA. Most intratumoral CD8⁺ T cells exhibited an antigen-experienced effector memory cell phenotype and were capable of producing IFN-γ. CD4⁺ regulatory T cells (Treg) and IL-17 producing T helper cells were significantly more prevalent in tumor than in blood. Consistent with the association with reduced survival in previous studies, we observed higher frequencies of both myeloid cells and Treg in poorly differentiated tumors. The majority of intratumoral T cells expressed the co-inhibitory receptor programmed death-1 (PD-1), suggesting one potential mechanism through which PDA may evade antitumor immunity. Successful multimodal neoadjuvant therapy altered the immunoregulatory balance and was associated with reduced infiltration of both myeloid cells and Treg.

Conclusion

Our data show that human PDA contains a complex mixture of inflammatory and regulatory immune cells, and that neoadjuvant therapy attenuates the infiltration of intratumoral cells associated with immunosuppression and worsened survival.

Inflammation-induced NFATc1-STAT3 transcription complex promotes pancreatic cancer initiation by KrasG12D

Cancer-associated inflammation is a molecular key feature in pancreatic ductal adenocarcinoma. Oncogenic KRAS in conjunction with persistent inflammation is known to accelerate carcinogenesis, although the underlying mechanisms remain poorly understood. Here, we outline a novel pathway whereby the transcription factors NFATc1 and STAT3 cooperate in pancreatic epithelial cells to promote Kras(G12D)-driven carcinogenesis. NFATc1 activation is induced by inflammation and itself accelerates inflammation-induced carcinogenesis in Kras(G12D) mice, whereas genetic or pharmacologic ablation of NFATc1 attenuates this effect. Mechanistically, NFATc1 complexes with STAT3 for enhancer-promoter communications at jointly regulated genes involved in oncogenesis, for example, Cyclin, EGFR and WNT family members. The NFATc1-STAT3 cooperativity is operative in pancreatitis-mediated carcinogenesis as well as in established human pancreatic cancer. Together, these studies unravel new mechanisms of inflammatory-driven pancreatic carcinogenesis and suggest beneficial effects of chemopreventive strategies using drugs that are currently available for targeting these factors in clinical trials.

SIGNIFICANCE

Our study points to the existence of an oncogenic NFATc1-STAT3 cooperativity that mechanistically links inflammation with pancreatic cancer initiation and progression. Because NFATc1-STAT3 nucleoprotein complexes control the expression of gene networks at the intersection of inflammation and cancer, our study has significant relevance for potentially managing pancreatic cancer and other inflammatory-driven malignancies.

Structural pathways of cytokines may illuminate their roles in regulation of cancer development and immunotherapy

Cytokines are messengers between tissues and the immune system. They play essential roles in cancer initiation, promotion, metastasis, and immunotherapy. Structural pathways of cytokine signaling which contain their interactions can help understand their action in the tumor microenvironment. Here, our aim is to provide an overview of the role of cytokines in tumor development from a structural perspective. Atomic details of protein-protein interactions can help in understanding how an upstream signal is transduced; how higher-order oligomerization modes of proteins can influence their function; how mutations, inhibitors or antagonists can change cellular consequences; why the same protein can lead to distinct outcomes, and which alternative parallel pathways can take over. They also help to design drugs/inhibitors against proteins de novo or by mimicking natural antagonists as in the case of interferon-γ. Since the structural database (PDB) is limited, structural pathways are largely built from a series of predicted binary protein-protein interactions. Below, to illustrate how protein-protein interactions can help illuminate roles played by cytokines, we model some cytokine interaction complexes exploiting a powerful algorithm (PRotein Interactions by Structural Matching-PRISM).

Pancreatic cancer stroma: Understanding biology leads to new therapeutic strategies

Pancreatic ductal adenocarcinoma (PDA) is among the deadliest cancers in the United States and in the world. Late diagnosis, early metastasis and lack of effective therapy are among the reasons why only 6% of patients diagnosed with PDA survive past 5 years. Despite development of targeted therapy against other cancers, little progression has been made in the treatment of PDA. Therefore, there is an urgent need for the development of new treatments. However, in order to proceed with treatments, the complicated biology of PDA needs to be understood first. Interestingly, majority of the tumor volume is not made of malignant epithelial cells but of stroma. In recent years, it has become evident that there is an important interaction between the stromal compartment and the less prevalent malignant cells, leading to cancer progression. The stroma not only serves as a growth promoting source of signals but it is also a physical barrier to drug delivery. Understanding the tumor-stroma signaling leading to development of desmoplastic reaction and tumor progression can lead to the development of therapies to decrease stromal activity and improve drug delivery. In this review, we focus on how the current understanding of biology of the pancreatic tumor microenvironment can be translated into the development of targeted therapy.

Myeloid Cell COX-2 deletion reduces mammary tumor growth through enhanced cytotoxic T-lymphocyte function

Cyclooxygenase-2 (COX-2) expression is associated with poor prognosis across a range of human cancers, including breast cancer. The contribution of tumor cell-derived COX-2 to tumorigenesis has been examined in numerous studies; however, the role of stromal-derived COX-2 is ill-defined. Here, we examined how COX-2 in myeloid cells, an immune cell subset that includes macrophages, influences mammary tumor progression. In mice engineered to selectively lack myeloid cell COX-2 [myeloid-COX-2 knockout (KO) mice], spontaneous neu oncogene-induced tumor onset was delayed, tumor burden reduced, and tumor growth slowed compared with wild-type (WT). Similarly, growth of neu-transformed mammary tumor cells as orthotopic tumors in immune competent syngeneic myeloid-COX-2 KO host mice was reduced compared with WT. By flow cytometric analysis, orthotopic myeloid-COX-2 KO tumors had lower tumor-associated macrophage (TAM) infiltration consistent with impaired colony stimulating factor-1-dependent chemotaxis by COX-2 deficient macrophages in vitro. Further, in both spontaneous and orthotopic tumors, COX-2-deficient TAM displayed lower immunosuppressive M2 markers and this was coincident with less suppression of CD8(+) cytotoxic T lymphocytes (CTLs) in myeloid-COX-2 KO tumors. These studies suggest that reduced tumor growth in myeloid-COX-2 KO mice resulted from disruption of M2-like TAM function, thereby enhancing T-cell survival and immune surveillance. Antibody-mediated depletion of CD8(+), but not CD4(+) cells, restored tumor growth in myeloid-COX-2 KO to WT levels, indicating that CD8(+) CTLs are dominant antitumor effectors in myeloid-COX-2 KO mice. Our studies suggest that inhibition of myeloid cell COX-2 can potentiate CTL-mediated tumor cytotoxicity and may provide a novel therapeutic approach in breast cancer therapy.

Kras as a key oncogene and therapeutic target in pancreatic cancer

Pancreatic cancer is one of the deadliest human malignancies and little progress has been achieved in its treatment over the past decades. Advances in our understanding of the biology of this disease provide new potential opportunities for treatment. Pancreatic cancer is preceded by precursor lesions, the most common of which are known as Pancreatic Intraepithelial Neoplasia (PanIN). PanIN lesions, which are the focus of this review, have a high incidence of Kras mutations, and Kras mutations are a hallmark of the late-stage disease. We now know from genetically engineered mouse models that oncogenic Kras is not only driving the formation of pancreatic cancer precursor lesions, but it is also required for their progression, and for the maintenance of invasive and metastatic disease. Thus, an enormous effort is being placed in generating Kras inhibitors for clinical use. Additionally, alternative approaches, including understanding the role of Kras effector pathways at different stages of the disease progression, are being devised to target Kras effector pathways therapeutically. In particular, efforts have focused on the MAPK pathway and the PI3K pathway, for which inhibitors are widely available. Finally, recent studies have highlighted the need for oncogenic Kras to establish feedback mechanisms that maintain its levels of activity; the latter might constitute alternative ways to target Kras in pancreatic cancer. Here, we will review recent basic research and discuss potential therapeutic applications.

Pancreatic cancer, treatment options, and GI-4000

Although pancreatic cancer is but the eleventh most prevalent cancer in the US, it is predicted that of all the patients newly diagnosed with this disease in 2014, only 27% will still be alive at the end of the first year and only 6% will make it past 5 years. The choice of chemotherapy in the treatment of pancreatic cancer is dependent on disease stage and patient performance status but, in general, the most widely used approved regimens include 5-fluorouracil (5-FU) combinations and gemcitabine combinations. Recent therapeutic strategies have resulted in an improvement in survival of patients with pancreatic cancer but the magnitude of change is disappointing and vast improvements are still needed. The goal of immunotherapy is to enhance and guide the body's immune system to recognize tumor-specific antigens and mount an attack against the disease. Among newer immune therapies, GI-4000 consists of 4 different targeted molecular immunogens, each containing a different Ras protein (antigen) encoded by the most commonly found mutant RAS genes in solid tumors--RAS mutations exist in over 90% of pancreatic ductal adenocarcinomas. We will review pancreatic cancer epidemiology and its current treatment options, and consider the prospects of immunotherapy, focusing on GI-4000. We discuss the potential mechanism of action of GI-4000, and the performance of this vaccination series thus far in early phase clinical trials.

Immune infiltrates as predictive markers of survival in pancreatic cancer patients

Pancreatic cancer is a devastating disease with dismal prognosis. The tumor microenvironment is composed by multiple cell types, molecular factors, and extracellular matrix forming a strong desmoplastic reaction, which is a hallmark of the disease. A complex cross-talk between tumor cells and the stroma exists with reciprocal influence that dictates tumor progression and ultimately the clinical outcome. In this context, tumor infiltrating immune cells through secretion of chemokine and cytokines exert an important regulatory role. Here we review the correlation between the immune infiltrates, evaluated on tumor samples of pancreatic cancer patients underwent surgical resection, and disease free and/or overall survival after surgery. Specifically, we focus on tumor infiltrating lymphocytes (TILs), mast cells (MCs) and macrophages that all contribute to a Th2-type inflammatory and immunosuppressive microenvironment. In these patients tumor immune infiltrates not only do not contribute to disease eradication but rather the features of Th2-type inflammation and immunosuppression is significantly associated with more rapid disease progression and reduced survival.