Cooperative induction of a tolerogenic dendritic cell phenotype by cytokines secreted by pancreatic carcinoma cells

Emerging Nanotechnology in Preclinical Pancreatic Cancer Immunotherapy: Driving Towards Clinical Applications

The high malignant degree and poor prognosis of pancreatic cancer (PC) pose severe challenges to the basic research and clinical translation of next-generation therapies. The rise of immunotherapy has improved the treatment of a variety of solid tumors, while the application in PC is highly restricted by the challenge of immunosuppressive tumor microenvironment. The latest progress of nanotechnology as drug delivery platform and immune adjuvant has improved drug delivery in a variety of disease backgrounds and enhanced tumor therapy based on immunotherapy. Based on the immune loop of PC and the status quo of clinical immunotherapy of tumors, this article discussed and critically analyzed the key transformation difficulties of immunotherapy adaptation to the treatment of PC, and then proposed the rational design strategies of new nanocarriers for drug delivery and immune regulation, especially the design of combined immunotherapy. This review also put forward prospective views on future research directions, so as to provide information for the new means of clinical treatment of PC combined with the next generation of nanotechnology and immunotherapy.

Current and future immunotherapeutic approaches in pancreatic cancer treatment

Pancreatic cancer is a major cause of cancer-related death, but despondently, the outlook and prognosis for this resistant type of tumor have remained grim for a long time. Currently, it is extremely challenging to prevent or detect it early enough for effective treatment because patients rarely exhibit symptoms and there are no reliable indicators for detection. Most patients have advanced or spreading cancer that is difficult to treat, and treatments like chemotherapy and radiotherapy can only slightly prolong their life by a few months. Immunotherapy has revolutionized the treatment of pancreatic cancer, yet its effectiveness is limited by the tumor's immunosuppressive and hard-to-reach microenvironment. First, this article explains the immunosuppressive microenvironment of pancreatic cancer and highlights a wide range of immunotherapy options, including therapies involving oncolytic viruses, modified T cells (T-cell receptor [TCR]-engineered and chimeric antigen receptor [CAR] T-cell therapy), CAR natural killer cell therapy, cytokine-induced killer cells, immune checkpoint inhibitors, immunomodulators, cancer vaccines, and strategies targeting myeloid cells in the context of contemporary knowledge and future trends. Lastly, it discusses the main challenges ahead of pancreatic cancer immunotherapy.

LOAd703, an oncolytic virus-based immunostimulatory gene therapy, combined with chemotherapy for unresectable or metastatic pancreatic cancer (LOKON001): results from arm 1 of a non-randomised, single-centre, phase 1/2 study

BACKGROUND

Pancreatic ductal adenocarcinoma is characterised by low immunogenicity and an immunosuppressive tumour microenvironment. LOAd703, an oncolytic adenovirus with transgenes encoding TMZ-CD40L and 4-1BBL, lyses cancer cells selectively, activates cytotoxic T cells, and induces tumour regression in preclinical models. The aim of this study was to evaluate the safety and feasibility of combining LOAd703 with chemotherapy for advanced pancreatic ductal adenocarcinoma.

METHODS

LOKON001 was a non-randomised, phase 1/2 study conducted at the Dan L Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX, USA, and consisted of two arms conducted sequentially; the results of arm 1 are presented here. In arm 1, patients 18 years or older with previously treated or treatment-naive unresectable or metastatic pancreatic ductal adenocarcinoma were treated with standard 28-day cycles of intravenous nab-paclitaxel 125 mg/m2 plus gemcitabine 1000 mg/m2 (up to 12 cycles) and intratumoural injections of LOAd703 every 2 weeks. Patients were assigned using Bayesian optimal interval design to receive 500 μL of LOAd703 at 5 × 1010 (dose 1), 1 × 1011 (dose 2), or 5 × 1011 (dose 3) viral particles per injection, injected endoscopically or percutaneously into the pancreatic tumour or a metastasis for six injections. The primary endpoints were safety and treatment-emergent immune response in patients who received at least one dose of LOAd703, and antitumour activity was a secondary endpoint. This study was registered with ClinicalTrials.gov, NCT02705196, arm 2 is ongoing and open to new participants.

FINDINGS

Between Dec 2, 2016, and Oct 17, 2019, 23 patients were assessed for eligibility, leading to 22 patients being enrolled. One patient withdrew consent, resulting in 21 patients (13 [62%] men and eight [38%] women) assigned to a dose group (three to dose 1, four to dose 2, and 14 to dose 3). 21 patients were evaluable for safety. Median follow-up time was 6 months (IQR 4-10), and data cutoff was Jan 5, 2023. The most common treatment-emergent adverse events overall were anaemia (96 [8%] of 1237 events), lymphopenia (86 [7%] events), hyperglycaemia (70 [6%] events), leukopenia (63 [5%] events), hypertension (62 [5%] events), and hypoalbuminaemia (61 [5%] events). The most common adverse events attributed to LOAd703 were fever (14 [67%] of 21 patients), fatigue (eight [38%]), chills (seven [33%]), and elevated liver enzymes (alanine aminotransferase in five [24%], alkaline phosphatase in four [19%], and aspartate aminotransferase in four [19%]), all of which were grade 1-2, except for a transient grade 3 aminotransferase elevation occurring at dose 3. A maximum tolerated dose was not reached, thereby establishing dose 3 as the highest-evaluated safe dose when combined with nab-paclitaxel plus gemcitabine. Proportions of CD8+ effector memory cells and adenovirus-specific T cells increased after LOAd703 injections in 15 (94%) of 16 patients for whom T-cell assays could be performed. Eight (44%, 95% CI 25-66) of 18 patients evaluable for activity had an objective response.

INTERPRETATION

Combining LOAd703 with nab-paclitaxel plus gemcitabine in patients with advanced pancreatic ductal adenocarcinoma was feasible and safe. To build upon this novel chemoimmunotherapeutic approach, arm 2 of LOKON001, which combines LOAd703, nab-paclitaxel plus gemcitabine, and atezolizumab, is ongoing.

FUNDING

Lokon Pharma, the Swedish Cancer Society, and the Swedish Research Council.

Innate and adaptive immune-directed tumour microenvironment in pancreatic ductal adenocarcinoma

One of the most deadly and aggressive cancers in the world, pancreatic ductal adenocarcinoma (PDAC), typically manifests at an advanced stage. PDAC is becoming more common, and by the year 2030, it is expected to overtake lung cancer as the second greatest cause of cancer-related death. The poor prognosis can be attributed to a number of factors, including difficulties in early identification, a poor probability of curative radical resection, limited response to chemotherapy and radiotherapy, and its immunotherapy resistance. Furthermore, an extensive desmoplastic stroma that surrounds PDAC forms a mechanical barrier that prevents vascularization and promotes poor immune cell penetration. Phenotypic heterogeneity, drug resistance, and immunosuppressive tumor microenvironment are the main causes of PDAC aggressiveness. There is a complex and dynamic interaction between tumor cells in PDAC with stromal cells within the tumour immune microenvironment. The immune suppressive microenvironment that promotes PDAC aggressiveness is contributed by a range of cellular and humoral factors, which itself are modulated by the cancer. In this review, we describe the role of innate and adaptive immune cells, complex tumor microenvironment in PDAC, humoral factors, innate immune-mediated therapeutic advances, and recent clinical trials in PDAC.

Lentinula Edodes Mycelia extract regulates the function of antigen-presenting cells to activate immune cells and prevent tumor-induced deterioration of immune function

Immune cell activation is essential for cancer rejection; however, the tumor microenvironment leads to deterioration of immune function, which enables cancer cells to survive and proliferate. We previously reported that oral ingestion of Lentinula Edodes Mycelia (L.E.M.) extract enhances the tumor antigen-specific T-cell response and exerts an antitumor effect in a tumor-bearing mouse model. In this study, we focused on antigen-presenting cells (APCs) located upstream of the immune system, induced a T-cell response, then examined the impact of L.E.M. extract on the APCs. L.E.M. extract enhanced the expression of MHC-I, MHC-II, CD86, CD80, and CD40 in bone marrow-derived dendritic cells (DCs) and strongly induced the production of IL-12. L.E.M.-stimulated DCs enhanced IFN-γ production from CD8+ T cells and induced their differentiation into effector cells. Furthermore, L.E.M. extract promoted IL-12 production and suppressed the production of IL-10 and TGF-β by transforming bone marrow-derived macrophages into M1-like macrophages. Furthermore, in a B16F10 melanoma inoculation model, DCs in the spleen were decreased and their activation was suppressed by the presence of cancer; however, ingestion of L.E.M. extract prevented this functional deterioration of DCs. In the spleen of cancer-bearing mice, the number of CD11b- F4/80+ macrophages in a hypoactivated state was also increased, whereas L.E.M. extract suppressed the increase of such macrophages. These findings suggest that L.E.M. extract may exhibit an antitumor immune response by regulating the function of APCs to induce cytotoxic T lymphocytes, as well as by suppressing the decline in antigen-presenting cell activity caused by the presence of cancer.

Systemic Alterations in Type-2 Conventional Dendritic Cells Lead to Impaired Tumor Immunity in Pancreatic Cancer

Intratumoral T-cell dysfunction is a hallmark of pancreatic tumors, and efforts to improve dendritic cell (DC)-mediated T-cell activation may be critical in treating these immune therapy unresponsive tumors. Recent evidence indicates that mechanisms that induce dysfunction of type 1 conventional DCs (cDC1) in pancreatic adenocarcinomas (PDAC) are drivers of the lack of responsiveness to checkpoint immunotherapy. However, the impact of PDAC on systemic type 2 cDC2 development and function has not been well studied. Herein, we report the analysis of 3 cohorts, totaling 106 samples, of human blood and bone marrow (BM) from patients with PDAC for changes in cDCs. We found that circulating cDC2s and their progenitors were significantly decreased in the blood of patients with PDAC, and repressed numbers of cDC2s were associated with poor prognosis. Serum cytokine analyses identified IL6 as significantly elevated in patients with PDAC and negatively correlated with cDC numbers. In vitro, IL6 impaired the differentiation of cDC1s and cDC2s from BM progenitors. Single-cell RNA sequencing analysis of human cDC progenitors in the BM and blood of patients with PDAC showed an upregulation of the IL6/STAT3 pathway and a corresponding impairment of antigen processing and presentation. These results suggested that cDC2s were systemically suppressed by inflammatory cytokines, which was linked to impaired antitumor immunity.

Peroxisome-related genes in hepatocellular carcinoma correlated with tumor metabolism and overall survival

BACKGROUND AND AIM

A prominent hallmark of tumors is aberrant lipid metabolism, and various peroxisome-related genes (PRGs) are associated with aberrant tumoral metabolic signaling. However, the influence of PRGs on the prognosis of hepatocellular carcinoma (HCC) patients remains debatable. Thus, the current study was designed to evaluate the effect of PRGs on HCC and construct a prognostic model for predicting survival.

METHODS

We initially acquired HCC-related gene expression profiles from the Cancer Genome Atlas and International Cancer Genome Consortium databases. We then utilized Cox analysis and Lasso regression to identify suitable PRGs for the risk model. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted to clarify the functional roles of PRGs. Single-sample gene set enrichment analysis (ssGSEA) was conducted to confirm the relationship between PRGs and immunity.

RESULTS

Four PRGs were correlated with HCC patient survival: 2 risk genes (MPV17, and ABCD1) and 2 protective genes (ACSL1 and ACSL6). We derived risk scores based on PRGs to construct a predictive model that could accurately predict overall survival (OS) among HCC patients. Furthermore, GO and KEGG analyses revealed that these PRGs were potentially involved in lipid metabolism and ferroptosis in HCC. Moreover, ssGSEA results demonstrated that high PRG scores were associated with immune suppressor activation, which caused the suppression of immune effectors (CD8⁺ T-cells, B cells, and NK cells) and the attenuation of the immune-mediated antitumor effect.

CONCLUSION

PRGs act as key regulators in tumorigenesis and tumor progression by affecting lipid synthesis and utilization, which we used to predict the outcome of HCC patients. Moreover, PRGs have been shown to promote tumoral immune resistance by serving as a vital bridge between metabolism and immunity. Thus, a personalized treatment approach targeting PRGs would clinically benefit patients by blocking the interaction between tumor metabolism and immunity.

Cytokines chattering in pancreatic ductal adenocarcinoma tumor microenvironment

Pancreatic ductal adenocarcinoma (PDAC) tumor microenvironment (TME) consists of multiple cell types interspersed by dense fibrous stroma. These cells communicate through low molecular weight signaling molecules called cytokines. The cytokines, through their receptors, facilitate PDAC initiation, progression, metastasis, and distant colonization of malignant cells. These signaling mediators secreted from tumor-associated macrophages, and cancer-associated fibroblasts in conjunction with oncogenic Kras mutation initiate acinar to ductal metaplasia (ADM), resulting in the appearance of early preneoplastic lesions. Further, M1- and M2-polarized macrophages provide proinflammatory conditions and promote deposition of extracellular matrix, whereas myofibroblasts and T-lymphocytes, such as Th17 and T-regulatory cells, create a fibroinflammatory and immunosuppressive environment with a significantly reduced cytotoxic T-cell population. During PDAC progression, cytokines regulate the expression of various oncogenic regulators such as NFκB, c-myc, growth factor receptors, and mucins resulting in the formation of high-grade PanIN lesions, epithelial to mesenchymal transition, invasion, and extravasation of malignant cells, and metastasis. During metastasis, PDAC cells colonize at the premetastatic niche created in the liver, and lung, an organotropic function primarily executed by cytokines in circulation or loaded in the exosomes from the primary tumor cells. The indispensable contribution of these cytokines at every stage of PDAC tumorigenesis makes them exciting candidates in combination with immune-, chemo- and targeted radiation therapy.

Clinical Strategies Targeting the Tumor Microenvironment of Pancreatic Ductal Adenocarcinoma

Pancreatic cancer has a complex tumor microenvironment which engages in extensive crosstalk between cancer cells, cancer-associated fibroblasts, and immune cells. Many of these interactions contribute to tumor resistance to anti-cancer therapies. Here, new therapeutic strategies designed to modulate the cancer-associated fibroblast and immune compartments of pancreatic ductal adenocarcinomas are described and clinical trials of novel therapeutics are discussed. Continued advances in our understanding of the pancreatic cancer tumor microenvironment are generating stromal and immune-modulating therapeutics that may improve patient responses to anti-tumor treatment.

Current Limitations and Novel Perspectives in Pancreatic Cancer Treatment

Simple Summary

This review article presents a synopsis of the key clinical developments, their limitations, and future perspectives in the treatment of pancreatic cancer. In the first part, we summarize the available treatments for pancreatic cancer patients according to tumor stage, as well as the most relevant clinical trials over the past two decades. Despite this progress, there is still much to be improved in terms of patient survival. Therefore, in the second part, we consider various components of the tumor microenvironment in pancreatic cancer, looking for the key drivers of therapy resistance and tumor progression, which may lead to the discovery of new potential targets. We also discuss the most prominent molecules targeting the stroma and immune compartment that are being investigated in either preclinical or clinical trials. Finally, we also outline interesting venues for further research, such as possible combinations of therapies that may have the potential for clinical application.

Abstract

Pancreatic cancer is one of the deadliest cancers worldwide, largely due to its aggressive development. Consequently, treatment options are often palliative, as only one-fifth of patients present with potentially curable tumors. The only available treatment with curative intent is surgery followed by adjuvant chemotherapy. However, even for patients that are eligible for surgery, the 5-year OS remains below 10%. Hence, there is an urgent need to find new therapeutic regimens. In the first part of this review, we discuss the tumor staging method and its impact on the corresponding current standard-of-care treatments for PDAC. We also consider the key clinical trials over the last 20 years that have improved patient survival. In the second part, we provide an overview of the major components and cell types involved in PDAC, as well as their respective roles and interactions with each other. A deeper knowledge of the interactions taking place in the TME may lead to the discovery of potential new therapeutic targets. Finally, we discuss promising treatment strategies targeting specific components of the TME and potential combinations thereof. Overall, this review provides an overview of the current challenges and future perspectives in the treatment of pancreatic cancer.

Perspectives on Hypoxia Signaling in Tumor Stroma

Hypoxia is a well-known characteristic of solid tumors that contributes to tumor progression and metastasis. Oxygen deprivation due to high demand of proliferating cancer cells and standard of care therapies induce hypoxia. Hypoxia signaling, mainly mediated by the hypoxia-inducible transcription factor (HIF) family, results in tumor cell migration, proliferation, metabolic changes, and resistance to therapy. Additionally, the hypoxic tumor microenvironment impacts multiple cellular and non-cellular compartments in the tumor stroma, including disordered tumor vasculature, homeostasis of ECM. Hypoxia also has a multifaceted and often contradictory influence on immune cell function, which contributes to an immunosuppressive environment. Here, we review the important function of HIF in tumor stromal components and summarize current clinical trials targeting hypoxia. We provide an overview of hypoxia signaling in tumor stroma that might help address some of the challenges associated with hypoxia-targeted therapies.

A comprehensive review on anticancer mechanism of bazedoxifene

Cancer is counted as a second leading cause of death among nontransmissible diseases. Identification of novel anticancer drugs is therefore necessary for the effective treatment of cancer. Conventional drug discovery is time consuming and expensive process. Unlike conventional drug discovery, drug repositioning offers a novel strategy for urgent drug discovery since it is a cost-effective and faster process. Bazedoxifene (BZA) is a synthetic selective estrogen receptor modulator, approved by the United States Food and Drug Administration for the treatment of osteoporosis in postmenopausal women. BZA is now being studied for its anticancer activity in various cancers including breast cancer, liver cancer, pancreatic cancer, colon cancer, head and neck cancer, medulloblastoma, brain cancer, and gastrointestinal cancer. Studies have reported that BZA is effective in reducing cancer progression through multiple mechanisms. BZA could effectively inhibit STAT3, PI3K/AKT, and MAPK signaling pathways and induce apoptosis. In addition to its anticancer activity as monotherapy, BZA has been shown to enhance the chemotherapeutic efficacy of clinical drugs such as paclitaxel, cisplatin, palbociclib, and oxaliplatin in multiple neoplasms. This review mainly focused on the anticancer activity, cellular targets, and anticancer mechanism of BZA, which may help the further design and conduct of research and repositioning it for oncological clinic trials.

Immunotherapy for pancreatic cancer: chasing the light at the end of the tunnel

BACKGROUND

Checkpoint blockade immunotherapy has had a significant impact on the survival of a subset of patients with advanced cancers. It has been particularly effective in immunogenic cancer types that present large numbers of somatic mutations in their genomes. To date, all conventional immunotherapies have failed to produce significant clinical benefits for patients diagnosed with pancreatic cancer, probably due to its poor immunogenic properties, including low numbers of neoantigens and highly immune-suppressive microenvironments.

CONCLUSIONS

Herein, we discuss advances that have recently been made in cancer immunotherapy and the potential of this field to deliver effective treatment options for pancreatic cancer patients. Preclinical investigations, combining different types of therapies, highlight possibilities to enhance anti-tumor immunity and to generate meaningful clinical responses in pancreatic cancer patients. Results from completed and ongoing (pre)clinical trials are discussed.

Edible Oxya chinensis sinuosa-Derived Protein as a Potential Nutraceutical for Anticancer Immunity Improvement

Oxya chinensis sinuosa (Ocs) is consumed as representative edible insects in Asia, but its function in various immune systems remains unclear. This study aimed to demonstrate the immunomodulatory effect, particularly on the innate and adaptive immune response, of Ocs protein (Ocs-P) and to investigate its function as a potent anticancer immunostimulant when administered during the progression stage of colon carcinoma in tumor-bearing mice. Our in vitro results demonstrated that Ocs-P treatment induces phenotypic alteration (increased expression of surface molecules and production of Th1-polarizing cytokines and decreased antigen uptake ability) of dendritic cells (DCs) through the activation of MAPK and NF-κB-dependent signaling pathways. Additionally, Ocs-P-stimulated DCs initiated differentiation of naive T cells into IFN-γ-producing Th1-type T cells effectively and activated cytotoxic CD8⁺ T cell response. In colon carcinoma-bearing mouse models, oral administration of Ocs-P inhibited tumor growth and restored the expression of decreased surface molecules in lineage^-CD11c⁺MHC-II⁺ splenic DCs. Furthermore, Ocs-P administration enhanced the generation of multifunctional CD4⁺ and CD8⁺ T cells expressing Th1-type cytokines (TNF-α, IFN-γ, and IL-2) and the degranulation marker (CD107a). Collectively, these results suggest that Ocs-P demonstrates an immunostimulatory effect and may induce powerful anticancer immunity.

IGF1R Axis Inhibition Restores Dendritic Cell Antitumor Response in Ovarian Cancer

Epithelial ovarian cancer (EOC) is the most lethal gynecological malignancy. The insulin-like growth factor (IGF) system plays a key role in regulating growth and invasiveness in several malignancies, including ovarian cancer. IGF1R targeting showed antiproliferative activity of EOC cells. However, clinical studies failed to show significant benefit. EOC cells suppress antitumor immune responses by inducing dendritic cell (DC) dysfunction. The IGF1 axis can regulate DC maturation. The current study evaluated involvement of the IGF1 axis in DC differentiation in EOC. Studies were conducted on EOC and on a human monocyte cell line. Tissue microarray analysis (TMA) was performed on 36 paraffin blocks from EOC patients. Expression of IGF1R, p53, Ki67, BRCA1, and DC markers was evaluated using immunohistochemistry. Co-culture of EOC cells with DC pretreated with IGF1R inhibitor blocked cancer cell migration. TMA demonstrated higher rate of IGF1R protein expression in patients with advanced (76.9%) as compared to early (40%) EOC. A negative correlation between IGF1R protein expression and the CD1c marker was found. These findings provide evidence that IGF1R axis inhibition could be a therapeutic strategy for ovarian cancer by restoring DC-mediated antitumor immunity.

Advances in Molecular Mechanisms for Traditional Chinese Medicine Actions in Regulating Tumor Immune Responses

Traditional Chinese medicine (TCM) has been developed for thousands of years with its various biological activities. The interest in TCM in tumor prevention and treatment is rising with its synergistic effect on tumor cells and tumor immunosuppressive microenvironment (TIM). Characteristic of TCM fits well within the whole system and multi-target cancer treatment. Herein we discuss the underlying mechanisms of TCM actions in TIM via regulating immunosuppressive cells, including restoring the antigen presentation function of dendritic cells, enhancing NK cells-mediated killing activity, restraining the functions of myeloid cell-derived suppressor cells, and inhibiting cancer-associated fibroblasts. TCM also regulates tumor progression through enhancing immune response, preventing immune escape and inducing cell death of tumor cells, which triggers immune response in nearby cells. In addition, we discuss TCM in clinical applications and the advantages and disadvantages of TCM in cancer prevention and treatment, as well as current therapeutic challenges and strategies. It might be helpful for understanding the therapeutic potential of TCM for cancer in clinic.

Pancreatic Cancer UK Grand Challenge: Developments and challenges for effective CAR T cell therapy for pancreatic ductal adenocarcinoma

Death from pancreatic ductal adenocarcinoma (PDAC) is rising across the world and PDAC is predicted to be the second most common cause of cancer death in the USA by 2030. Development of effective biotherapies for PDAC are hampered by late presentation, a low number of differentially expressed molecular targets and a tumor-promoting microenvironment that forms both a physical, collagen-rich barrier and is also immunosuppressive. In 2017 Pancreatic Cancer UK awarded its first Grand Challenge Programme award to tackle this problem. The team plan to combine the use of novel CAR T cells with strategies to overcome the barriers presented by the tumor microenvironment. In advance of publication of those data this review seeks to highlight the key problems in effective CAR T cell therapy of PDAC and to describe pre-clinical and clinical progress in CAR T bio-therapeutics.

Dendritic Cell Paucity Leads to Dysfunctional Immune Surveillance in Pancreatic Cancer

Here, we utilized spontaneous models of pancreatic and lung cancer to examine how neoantigenicity shapes tumor immunity and progression. As expected, neoantigen expression during lung adenocarcinoma development leads to T cell-mediated immunity and disease restraint. By contrast, neoantigen expression in pancreatic ductal adenocarcinoma (PDAC) results in exacerbation of a fibro-inflammatory microenvironment that drives disease progression and metastasis. Pathogenic T_H17 responses are responsible for this neoantigen-induced tumor progression in PDAC. Underlying these divergent T cell responses in pancreas and lung cancer are differences in infiltrating conventional dendritic cells (cDCs). Overcoming cDC deficiency in early-stage PDAC leads to disease restraint, while restoration of cDC function in advanced PDAC restores tumor-restraining immunity and enhances responsiveness to radiation therapy.

Current advances and outlooks in immunotherapy for pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an incurable cancer resistant to traditional treatments, although a limited number of early-stage patients can undergo radical resection. Immunotherapies for the treatment of haematological malignancies as well as solid tumours have been substantially improved over the past decades, and impressive results have been obtained in recent preclinical and clinical trials. However, PDAC is likely the exception because of its unique tumour microenvironment (TME). In this review, we summarize the characteristics of the PDAC TME and focus on the network of various tumour-infiltrating immune cells, outlining the current advances in PDAC immunotherapy and addressing the effect of the PDAC TME on immunotherapy. This review further explores the combinations of different therapies used to enhance antitumour efficacy or reverse immunodeficiencies and describes optimizable immunotherapeutic strategies for PDAC. The concordant combination of various treatments, such as targeting cancer cells and the stroma, reversing suppressive immune reactions and enhancing antitumour reactivity, may be the most promising approach for the treatment of PDAC. Traditional treatments, especially chemotherapy, may also be optimized for individual patients to remodel the immunosuppressive microenvironment for enhanced therapy.

Severe depletion of peripheral blood dendritic cell subsets in obstructive sleep apnea patients: A new link with cancer?

Recent evidence suggests that alterations of the immune responses are associated with the inflammatory nature of obstructive sleep apnea (OSA) and of its related co-morbidities. In this scenario, we asked whether circulating dendritic cell (DC) subsets may be possible players as their role has not yet been detailed. The frequency distribution of peripheral blood myeloid (mDC1 and mDC2) and plasmacytoid (p) DCs was investigated by mean of multi-parametric flow cytometry in 45 OSA patients (mean age: 53 yrs; M = 29) at the time of the first diagnosis and compared to 30 age- and sex-matched healthy controls. Oxidative burst (OB) and serum levels of tumor necrosis factor (TNF)-α, (interleukin) (IL)-6, interferon (INF)-γ, IL-2, IL-4, IL-10 and vascular endothelial growth factor (VEGF) were also analyzed. All subsets of circulating DCs were significantly depleted in OSA patients as compared to healthy subjects (p < 0.01, in all instances), with mDC2 and pDC subtypes being more severely compromised. These findings were co-existing with higher levels of OB along with an increased expression of IL-6, IL-10, TNF-α, IFN-γ, and VEGF (p < 0.005 in all instances). In particular, IL6 levels were significantly higher (p = 0.013) in severe OSA patients (apnea/hypopnea index >30) and were inversely correlated with both mDC2 (r = -0.802, p < 0.007) and pDC (r = -0.317, p = 0.04) subsets. We first provide evidence for a constitutive reduction of all circulating DC subsets in OSA patients. Perturbation of DCs coexists with an inflammatory milieu and is negatively correlated with the expression of IL-6, which is actually recognized as a pivotal inhibitor of DC maturation. Future studies exploring the contribution of DCs in the pathogenesis of OSA and of its complications should be encouraged.

Personalized Dendritic Cell Vaccines-Recent Breakthroughs and Encouraging Clinical Results

With the advent of combined immunotherapies, personalized dendritic cell (DC)-based vaccination could integrate the current standard of care for the treatment of a large variety of tumors. Due to their proficiency at antigen presentation, DC are key coordinators of the innate and adaptive immune system, and have critical roles in the induction of antitumor immunity. However, despite proven immunogenicity and favorable safety profiles, DC-based immunotherapies have not succeeded at inducing significant objective clinical responses. Emerging data suggest that the combination of DC-based vaccination with other cancer therapies may fully unleash the potential of DC-based cancer vaccines and improve patient survival. In this review, we discuss the recent efforts to develop innovative personalized DC-based vaccines and their use in combined therapies, with a particular focus on ovarian cancer and the promising results of mutanome-based personalized immunotherapies.

Hypoxia as a barrier to immunotherapy in pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is a lethal disease with limited response to cytotoxic chemoradiotherapy, as well as newer immunotherapies. The PDA tumor microenvironment contains infiltrating immune cells including cytotoxic T cells; however, there is an overall immunosuppressive milieu. Hypoxia is a known element of the solid tumor microenvironment and may promote tumor survival. Through various mechanisms including, but not limited to, those mediated by HIF-1α, hypoxia also leads to increased tumor proliferation and metabolic changes. Furthermore, epithelial to mesenchymal transition is promoted through several pathways, including NOTCH and c-MET, regulated by hypoxia. Hypoxia-promoted changes also contribute to the immunosuppressive phenotype seen in many different cell types within the microenvironment and thereby may inhibit an effective immune system response to PDA. Pancreatic stellate cells (PSCs) and myofibroblasts appear to contribute to the recruitment of myeloid derived suppressor cells (MDSCs) and B cells in PDA via cytokines increased due to hypoxia. PSCs also increase collagen secretion in response to HIF-1α, which promotes a fibrotic stroma that alters T cell homing and migration. In hypoxic environments, B cells contribute to cytotoxic T cell exhaustion and produce chemokines to attract more immunosuppressive regulatory T cells. MDSCs inhibit T cell metabolism by hoarding key amino acids, modulate T cell homing by cleaving L-selectin, and prevent T cell activation by increasing PD-L1 expression. Immunosuppressive M2 phenotype macrophages promote T cell anergy via increased nitric oxide (NO) and decreased arginine in hypoxia. Increased numbers of regulatory T cells are seen in hypoxia which prevent effector T cell activation through cytokine production and increased CTLA-4. Effective immunotherapy for pancreatic adenocarcinoma and other solid tumors will need to help counteract the immunosuppressive nature of hypoxia-induced changes in the tumor microenvironment. Promising studies will look at combination therapies involving checkpoint inhibitors, chemokine inhibitors, and possible targeting of hypoxia. While no model is perfect, assuring that models incorporate the effects of hypoxia on cancer cells, stromal cells, and effector immune cells will be crucial in developing successful therapies.

Ping-Pong-Tumor and Host in Pancreatic Cancer Progression

Metastasis is the main cause of high pancreatic cancer (PaCa) mortality and trials dampening PaCa mortality rates are not satisfying. Tumor progression is driven by the crosstalk between tumor cells, predominantly cancer-initiating cells (CIC), and surrounding cells and tissues as well as distant organs, where tumor-derived extracellular vesicles (TEX) are of major importance. A strong stroma reaction, recruitment of immunosuppressive leukocytes, perineural invasion, and early spread toward the peritoneal cavity, liver, and lung are shared with several epithelial cell-derived cancer, but are most prominent in PaCa. Here, we report on the state of knowledge on the PaCIC markers Tspan8, alpha6beta4, CD44v6, CXCR4, LRP5/6, LRG5, claudin7, EpCAM, and CD133, which all, but at different steps, are engaged in the metastatic cascade, frequently via PaCIC-TEX. This includes the contribution of PaCIC markers to TEX biogenesis, targeting, and uptake. We then discuss PaCa-selective features, where feedback loops between stromal elements and tumor cells, including distorted transcription, signal transduction, and metabolic shifts, establish vicious circles. For the latter particularly pancreatic stellate cells (PSC) are responsible, furnishing PaCa to cope with poor angiogenesis-promoted hypoxia by metabolic shifts and direct nutrient transfer via vesicles. Furthermore, nerves including Schwann cells deliver a large range of tumor cell attracting factors and Schwann cells additionally support PaCa cell survival by signaling receptor binding. PSC, tumor-associated macrophages, and components of the dysplastic stroma contribute to perineural invasion with signaling pathway activation including the cholinergic system. Last, PaCa aggressiveness is strongly assisted by the immune system. Although rich in immune cells, only immunosuppressive cells and factors are recovered in proximity to tumor cells and hamper effector immune cells entering the tumor stroma. Besides a paucity of immunostimulatory factors and receptors, immunosuppressive cytokines, myeloid-derived suppressor cells, regulatory T-cells, and M2 macrophages as well as PSC actively inhibit effector cell activation. This accounts for NK cells of the non-adaptive and cytotoxic T-cells of the adaptive immune system. We anticipate further deciphering the molecular background of these recently unraveled intermingled phenomena may turn most lethal PaCa into a curatively treatable disease.

Thymic stromal lymphopoietin in human pancreatic ductal adenocarcinoma: expression and prognostic significance

Thymic stromal lymphopoietin (TSLP) has emerged as an important, but contradictory, player conditioning tumor growth. In certain contexts, by driving T helper (h) 2 responses via tumor-associated OX40 Ligand (OX40L)⁺ dendritic cells (DCs), TSLP may play a pro-tumorigenic role. The study elucidates the importance of TSPL in pancreatic ductal adenocarcinoma (PDAC), by analyzing: i) TSLP levels in PDAC cell-line supernatants and plasma from patients with locally-advanced/metastatic PDAC, pre- and post-treatment with different chemotherapeutic protocols, in comparison with healthy donors; ii) TSLP and OX40L expression in PDAC and normal pancreatic tissues, by immunohistochemistry; iii) OX40L expression on ex vivo-generated normal DCs in the presence of tumor-derived TSLP, by flow cytometry; iv) clinical relevance in terms of diagnostic and prognostic value and influence on treatment modality and response.

Some PDAC cell lines, such as BxPC-3, expressed both TSLP mRNA and protein. Normal DCs, generated ex vivo in the presence of TSLP-rich-cell supernatants, displayed increased expression of OX40L, reduced by the addition of a neutralizing anti-TSLP polyclonal antibody. OX40L⁺ cells were detected in pancreatic tumor inflammatory infiltrates. Abnormally elevated TSLP levels were detected in situ in tumor cells and, systemically, in locally-advanced/metastatic PDAC patients. Of the chemotherapeutic protocols applied, gemcitabine plus oxaliplatin (GEMOX) significantly increased circulating TSLP levels. Elevated plasma TSLP concentration was associated with shorter overall survival and increased risk of poor outcome. Plasma TSLP measurement successfully discriminated PDAC patients from healthy controls.

These data show that TSLP secreted by pancreatic cancer cells may directly impact PDAC biology and patient outcome.

Targeting dendritic cells in pancreatic ductal adenocarcinoma

Dendritic cells (DC) are an integral part of the tumor microenvironment. Pancreatic cancer is characterized by reduced number and function of DCs, which impacts antigen presentation and contributes to immune tolerance. Recent data suggest that exosomes can mediate communication between pancreatic cancer cells and DCs. Furthermore, levels of DCs may serve as prognostic factors. There is also growing evidence for the effectiveness of vaccination with DCs pulsed with tumor antigens to initiate adaptive cytolytic immune responses via T cells. Most experience with DC-based vaccination has been gathered for MUC1 and WT1 antigens, where clinical studies in advanced pancreatic cancer have provided encouraging results. In this review, we highlight the role of DC in the course, prognosis and treatment of pancreatic cancer.

Tumor lysate-loaded Bacterial Ghosts as a tool for optimized production of therapeutic dendritic cell-based cancer vaccines

Cancer immunotherapy with dendritic cell (DC)-based vaccines has been used to treat various malignancies for more than two decades, however generally showed a limited clinical success. Among various factors responsible for their modest clinical activity is the lack of universally applied, standardized protocols for the generation of clinical-grade DC vaccines, capable of inducing effective anti-tumor immune responses. We investigated Bacterial Ghosts (BGs) - empty envelopes of Gram-negative bacteria - as a tool for optimized production of DC vaccines. BGs possess various intact cell surface structures, exhibiting strong adjuvant properties required for the induction of DC maturation, whereas their empty internal space can be easily filled with a source tumor antigens, e.g. tumor lysate. Hence BGs emerge as an excellent platform for both the induction of immunogenic DC maturation and loading with tumor antigens in a single-step procedure. We compared the phenotype, cytokine secretion profile, functional activity and ability to induce immunogenic T-cell responses in vitro of human monocyte-derived DCs generated using BG platform and DCs matured with widely used lipopolysaccharide (LPS) plus interferon-γ cocktail and loaded with tumor lysate. Both approaches induced DC maturation, however BG-based protocol was superior to LPS-based protocol in terms of the ability to induce DCs with a lower tolerogenic potential, resulting in a more robust CD8⁺ T cell activation and their functional activity as well as significantly lower induction of regulatory T cells. These superior parameters are attributed, at least in part, to the ability of BG-matured DCs to resist potential immunosuppressive and pro-tolerogenic activity of various tumor cell lysates, including melanoma, renal carcinoma and glioblastoma.

GPR68, a proton-sensing GPCR, mediates interaction of cancer-associated fibroblasts and cancer cells

The microenvironment of pancreatic ductal adenocarcinoma (PDAC) is characterized by a dense fibrotic stroma (desmoplasia) generated by pancreatic cancer-associated fibroblasts (CAFs) derived from pancreatic stellate cells (PSCs) and pancreatic fibroblasts (PFs). Using an unbiased GPCRomic array approach, we identified 82 G-protein-coupled receptors (GPCRs) commonly expressed by CAFs derived from 5 primary PDAC tumors. Compared with PSCs and PFs, CAFs have increased expression of GPR68 (a proton-sensing GPCR), with the results confirmed by immunoblotting, The Cancer Genome Atlas data, and immunohistochemistry of PDAC tumors. Co-culture of PSCs with PDAC cells, or incubation with TNF-α, induced GPR68 expression. GPR68 activation (by decreasing the extracellular pH) enhanced IL-6 expression via a cAMP/PKA/cAMP response element binding protein signaling pathway. Knockdown of GPR68 by short interfering RNA diminished low pH-induced production of IL-6 and enhancement of PDAC cell proliferation by CAF conditioned media. CAFs from other gastrointestinal cancers also express GPR68. PDAC cells thus induce expression by CAFs of GPR68, which senses the acidic microenvironment, thereby increasing production of fibrotic markers and IL-6 and promoting PDAC cell proliferation. CAF-expressed GPR68 is a mediator of low-pH-promoted regulation of the tumor microenvironments, in particular to PDAC cell-CAF interaction and may be a novel therapeutic target for pancreatic and perhaps other types of cancers.-Wiley, S. Z., Sriram, K., Liang, W., Chang, S. E., French, R., McCann, T., Sicklick, J., Nishihara, H., Lowy, A. M., Insel, P. A. GPR68, a proton-sensing GPCR, mediates interaction of cancer-associated fibroblasts and cancer cells.

Challenges and Perspectives for Immunotherapy in Adenocarcinoma of the Pancreas: The Cancer Immunity Cycle

Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease with a devastating 5-year overall survival of only approximately 7%. Although just 4% of all malignant diseases are accounted to PDAC, it will become the second leading cause of cancer-related deaths before 2030. Immunotherapy has proven to be a promising therapeutic option in various malignancies such as melanoma, non-small cell lung cancer (NSCLC), microsatellite instability-high gastrointestinal cancer, urinary tract cancer, kidney cancer, and others. In this review, we summarize recent findings about immunological aspects of PDAC with the focus on the proposed model of the "cancer immunity cycle". By this model, a deeper understanding of the underlying mechanism in achieving a T-cell response against cancer cells is provided. There is currently great interest in the field around designing novel immunotherapy combination studies for PDAC based on a sound understanding of the underlying immunobiology.

Oncolytic viral therapy for pancreatic cancer

Outcomes of pancreatic adenocarcinoma (PDA) remain dismal despite extensive clinical investigation. Combination chemotherapy provides modest improvements in survival above best supportive care, and immunotherapy has thus far not proven effective. Nevertheless, growing insight into antitumor immunity and the tumor microenvironment has inspired the discovery of novel agents targeting PDA. Oncolytic viruses represent an emerging class of immunotherapeutic agents that have undergone extensive preclinical investigation and warrant further investigation in well-designed clinical trials.

Tumour-derived Interleukin 35 promotes pancreatic ductal adenocarcinoma cell extravasation and metastasis by inducing ICAM1 expression

Interleukin 35 (IL-35) is a novel member of the IL-12 family, consisting of an EBV-induced gene 3 (EBI3) subunit and a P35 subunit. IL-35 is an immune-suppressive cytokine mainly produced by regulatory T cells. However, the role of IL-35 in cancer metastasis and progression is not well understood. Here we demonstrate that IL-35 is overexpressed in human pancreatic ductal adenocarcinoma (PDAC) tissues, and that IL-35 overexpression is associated with poor prognosis in PDAC patients. IL-35 has critical roles in PDAC cell extravasation and metastasis by facilitating the adhesion to endothelial cells and transendothelial extravasation. Mechanistically, IL-35 promotes ICAM1 overexpression through a GP130-STAT1 signalling pathway, which facilitates endothelial adhesion and transendothelial migration via an ICAM1-fibrinogen-ICAM1 bridge. In an orthotopic xenograft model, IL-35 promotes spontaneous pancreatic cancer metastasis in an ICAM1-dependent manner. Together, our results indicate additional functions of IL-35 in promoting PDAC metastasis through mediating ICAM1 expression.

The cornerstone K-RAS mutation in pancreatic adenocarcinoma: From cell signaling network, target genes, biological processes to therapeutic targeting

RAS belongs to the super family of small G proteins and plays crucial roles in signal transduction from membrane receptors in the cell. Mutations of K-RAS oncogene lead to an accumulation of GTP-bound proteins that maintains an active conformation. In the pancreatic ductal adenocarcinoma (PDAC), one of the most deadly cancers in occidental countries, mutations of the K-RAS oncogene are nearly systematic (>90%). Moreover, K-RAS mutation is the earliest genetic alteration occurring during pancreatic carcinogenetic sequence. In this review, we discuss the central role of K-RAS mutations and their tremendous diversity of biological properties by the interconnected regulation of signaling pathways (MAPKs, NF-κB, PI3K, Ral…). In pancreatic ductal adenocarcinoma, transcriptome analysis and preclinical animal models showed that K-RAS mutation alters biological behavior of PDAC cells (promoting proliferation, migration and invasion, evading growth suppressors, regulating mucin pattern, and miRNA expression). K-RAS also impacts tumor microenvironment and PDAC metabolism reprogramming. Finally we discuss therapeutic targeting strategies of K-RAS that have been developed without significant clinical success so far. As K-RAS is considered as the undruggable target, targeting its multiple effectors and target genes should be considered as potential alternatives.

Expression of CD14, IL10, and Tolerogenic Signature in Dendritic Cells Inversely Correlate with Clinical and Immunologic Response to TARP Vaccination in Prostate Cancer Patients

Purpose: Despite the vast number of clinical trials conducted so far, dendritic cell (DC)-based cancer vaccines have mostly shown unsatisfactory results. Factors and manufacturing procedures essential for these therapeutics to induce effective antitumor immune responses have yet to be fully characterized. We here aimed to identify DC markers correlating with clinical and immunologic response in a prostate carcinoma vaccination regimen.Experimental Design: We performed an extensive characterization of DCs used to vaccinate 18 patients with prostate carcinoma enrolled in a pilot trial of T-cell receptor gamma alternate reading frame protein (TARP) peptide vaccination (NCT00908258). Peptide-pulsed DC preparations (114) manufactured were analyzed by gene expression profiling, cell surface marker expression and cytokine release secretion, and correlated with clinical and immunologic responses.Results: DCs showing lower expression of tolerogenic gene signature induced strong antigen-specific immune response and slowing in PSA velocity, a surrogate for clinical response. These DCs were also characterized by lower surface expression of CD14, secretion of IL10 and MCP-1, and greater secretion of MDC. When combined, these four factors were able to remarkably discriminate DCs that were sufficiently potent to induce strong immunologic response.Conclusions: DC factors essential for the activation of immune responses associated with TARP vaccination in prostate cancer patients were identified. This study highlights the importance of in-depth characterization of DC vaccines and other cellular therapies, to understand the critical factors that hinder potency and potential efficacy in patients. Clin Cancer Res; 23(13); 3352-64. ©2017 AACR.

Role of immune cells in pancreatic cancer from bench to clinical application: An updated review

BACKGROUND

Pancreatic cancer (PC) remains difficult to treat, despite the recent advances in various anticancer therapies. Immuno-inflammatory response is considered to be a major risk factor for the development of PC in addition to a combination of genetic background and environmental factors. Although patients with PC exhibit evidence of systemic immune dysfunction, the PC microenvironment is replete with immune cells.

METHODS

We searched PubMed for all relevant English language articles published up to March 2016. They included clinical trials, experimental studies, observational studies, and reviews. Trials enrolled at Clinical trial.gov were also searched.

RESULTS

PC induces an immunosuppressive microenvironment, and intratumoral activation of immunity in PC is attenuated by inhibitory signals that limit immune effector function. Multiple types of immune responses can promote an immunosuppressive microenvironment; key regulators of the host tumor immune response are dendritic cells, natural killer cells, macrophages, myeloid derived suppressor cells, and T cells. The function of these immune cells in PC is also influenced by chemotherapeutic agents and the components in tumor microenvironment such as pancreatic stellate cells. Immunotherapy of PC employs monoclonal antibodies/effector cells generated in vitro or vaccination to stimulate antitumor response. Immune therapy in PC has failed to improve overall survival; however, combination therapies comprising immune checkpoint inhibitors and vaccines have been attempted to increase the response.

CONCLUSION

A number of studies have begun to elucidate the roles of immune cell subtypes and their capacity to function or dysfunction in the tumor microenvironment of PC. It will not be long before immune therapy for PC becomes a clinical reality.

Bazedoxifene as a Novel GP130 Inhibitor for Pancreatic Cancer Therapy

The IL6/GP130/STAT3 pathway is crucial for tumorigenesis in multiple cancer types, including pancreatic cancer, and presents as a viable target for cancer therapy. We reported Bazedoxifene, which is approved as a selective estrogen modulator by FDA, as a novel inhibitor of IL6/GP130 protein-protein interactions using multiple ligand simultaneous docking and drug repositioning approaches. STAT3 is one of the major downstream effectors of IL6/GP130. Here, we observed Bazedoxifene inhibited STAT3 phosphorylation and STAT3 DNA binding, induced apoptosis, and suppressed tumor growth in pancreatic cancer cells with persistent IL6/GP130/STAT3 signaling in vitro and in vivo In addition, IL6, but not INFγ, rescued Bazedoxifene-mediated reduction of cell viability. Bazedoxifene also inhibited STAT3 phosphorylation induced by IL6 and IL11, but not by OSM or STAT1 phosphorylation induced by INFγ in pancreatic cancer cells, suggesting that Bazedoxifene inhibits the GP130/STAT3 pathway mediated by IL6 and IL11. Furthermore, Bazedoxifene combined with paclitaxel or gemcitabine synergistically inhibited cell viability and cell migration in pancreatic cancer cells. These results indicate that Bazedoxifene is a potential agent and can generate synergism when combined with conventional chemotherapy in human pancreatic cancer cells and tumor xenograft in mice. Therefore, our results support that Bazedoxifene as a novel inhibitor of GP130 signaling and may be a potential and safe therapeutic agent for human pancreatic cancer therapy. Mol Cancer Ther; 15(11); 2609-19. ©2016 AACR.

Genetics and biology of pancreatic ductal adenocarcinoma

Ying et al. review pancreatic ductal adenocarcinoma (PDAC) genetics and biology, particularly altered cancer cell metabolism, the complexity of immune regulation in the tumor microenvironment, and impaired DNA repair processes.

With 5-year survival rates remaining constant at 6% and rising incidences associated with an epidemic in obesity and metabolic syndrome, pancreatic ductal adenocarcinoma (PDAC) is on track to become the second most common cause of cancer-related deaths by 2030. The high mortality rate of PDAC stems primarily from the lack of early diagnosis and ineffective treatment for advanced tumors. During the past decade, the comprehensive atlas of genomic alterations, the prominence of specific pathways, the preclinical validation of such emerging targets, sophisticated preclinical model systems, and the molecular classification of PDAC into specific disease subtypes have all converged to illuminate drug discovery programs with clearer clinical path hypotheses. A deeper understanding of cancer cell biology, particularly altered cancer cell metabolism and impaired DNA repair processes, is providing novel therapeutic strategies that show strong preclinical activity. Elucidation of tumor biology principles, most notably a deeper understanding of the complexity of immune regulation in the tumor microenvironment, has provided an exciting framework to reawaken the immune system to attack PDAC cancer cells. While the long road of translation lies ahead, the path to meaningful clinical progress has never been clearer to improve PDAC patient survival.

Pharmacological Modulation of Proton Channel Hv1 in Cancer Therapy: Future Perspectives

The pharmacological modulation of the immunosuppressive tumor microenvironment has emerged as a relevant component for cancer therapy. Several approaches aiming to deplete innate and adaptive suppressive populations, to circumvent the impairment in antigen presentation, and to ultimately increase the frequency of activated tumor-specific T cells are currently being explored. In this review, we address the potentiality of targeting the voltage-gated proton channel, Hv1, as a novel strategy to modulate the tumor microenvironment. The function of Hv1 in immune cells such as macrophages, neutrophils, dendritic cells, and T cells has been associated with the maintenance of NADPH oxidase activity and the generation of reactive oxygen species, which are required for the host defense against pathogens. We discuss evidence suggesting that the Hv1 proton channel could also be important for the function of these cells within the tumor microenvironment. Furthermore, as summarized here, tumor cells express Hv1 as a primary mechanism to extrude the increased amount of protons generated metabolically, thus maintaining physiologic values for the intracellular pH. Therefore, because this channel might be relevant for both tumor cells and immune cells supporting tumor growth, the pharmacological inhibition of Hv1 could be an innovative approach for cancer therapy. With that focus, we analyzed the available compounds that inhibit Hv1, highlighted the need to develop better drugs suitable for patients, and commented on the future perspectives of targeting Hv1 in the context of cancer therapy.

Endogenous and tumour-derived microRNAs regulate cross-presentation in dendritic cells and consequently cytotoxic T cell function

Dendritic cells (DCs) are potent antigen presenting cells (APCs). They are also specialized in the induction of cytotoxic T lymphocyte mediated responses against extracellular antigens, including tumour-specific antigens, by presenting peptide-Major Histocompatibility Complex (MHC) I complexes to naïve CD8⁺ T cells in lymphoid tissues, a process called cross-presentation. Emerging evidence suggests that the efficiency of cross-presentation can be influenced by a unique set of microRNAs (miRNAs). Some are differentially expressed in the course of morphological and functional development of DCs while tumorigenic miRNAs (onco-miRs) can be delivered to and inserted into DCs via exosomes. The latter reprogram the miRNA repertoire of DCs, transforming them from effective APCs to negative modulators of immunity, ultimately aiding cancers to evade host immunity. On the other hand, endogenous microRNAs can influence cross-presentation either positively or negatively. In this review, we discuss the possible mechanisms by which specific miRNAs influence cross-presentation as well as the viability of manipulating the expression of miRNAs that regulate DC cross-presentation as a potential cancer immunotherapy intervention.

Synergistic Effect and Molecular Mechanisms of Traditional Chinese Medicine on Regulating Tumor Microenvironment and Cancer Cells

The interaction of tumor cells with the microenvironment is like a relationship between the “seeds” and “soil,” which is a hotspot in recent cancer research. Targeting at tumor microenvironment as well as tumor cells has become a new strategy for cancer treatment. Conventional cancer treatments mostly focused on single targets or single mechanism (the seeds or part of the soil); few researches intervened in the whole tumor microenvironment and achieved ideal therapeutic effect as expected. Traditional Chinese medicine displays a broad range of biological effects, and increasing evidence has shown that it may relate with synergistic effect on regulating tumor microenvironment and cancer cells. Based on literature review and our previous studies, we summarize the synergistic effect and the molecular mechanisms of traditional Chinese medicine on regulating tumor microenvironment and cancer cells.

Inhibition of HIF-1α by PX-478 enhances the anti-tumor effect of gemcitabine by inducing immunogenic cell death in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the worst prognoses among all the malignancies. Now, gemcitabine (Gem) is the first line chemotherapeutic drug for advanced pancreatic cancer. However, Gem is usually ineffective to the PDAC because of high degree of drug resistance. Hypoxia and immune suppressive milieu are the best-described hallmarks of PDAC; therefore, we investigated the impact of hypoxia inducible factor-1 (HIF-1) inhibitor, PX-478, in combination with Gem on the induction of immunogenic cell death (ICD). We verified that combined treatment with Gem/PX-478 significantly enhanced the anti-tumor effect and increased proportion of tumor infiltrating T-lymphocytes in Panc02-bearing immune-competent but not in immune-deficient mice. Vaccination using Panc02 cell line treated with single agent or in combination showed significant anti-tumor effects. Pancreatic cell lines treated with Gem and PX-478 can induce an increase in eIF2α phosphorylation was correlated with down-regulation of HIF-1α and elicited exposure of CRT and release of HMGB1 and ATP. Only co-treated cells induced DC maturation/phagocytosis and IFN-γ secretion by cytotoxic T lymphocytes. Altogether, combined treatment with Gem/PX-478 showed significantly inhibition on tumor growth and anti-tumor immunization. We propose that inhibition HIF-1α elicits Gem-induced immune response and eliminates PDAC cells by inducing ICD.

Mesothelioma tumor cells modulate dendritic cell lipid content, phenotype and function

Dendritic cells (DCs) play an important role in the generation of anti-cancer immune responses, however there is evidence that DCs in cancer patients are dysfunctional. Lipid accumulation driven by tumor-derived factors has recently been shown to contribute to DC dysfunction in several human cancers, but has not yet been examined in mesothelioma. This study investigated if mesothelioma tumor cells and/or their secreted factors promote increases in DC lipid content and modulate DC function. Human monocyte-derived DCs (MoDCs) were exposed to human mesothelioma tumor cells and tumor-derived factors in the presence or absence of lipoproteins. The data showed that immature MoDCs exposed to mesothelioma cells or factors contained increased lipid levels relative to control DCs. Lipid accumulation was associated with reduced antigen processing ability (measured using a DQ OVA assay), upregulation of the co-stimulatory molecule, CD86, and production of the tolerogenic cytokine, IL-10. Increases in DC lipid content were further enhanced by co-exposure to mesothelioma-derived factors and triglyceride-rich lipoproteins, but not low-density lipoproteins. In vivo studies using a murine mesothelioma model showed that the lipid content of tumor-infiltrating CD4+ CD8α- DCs, CD4- CD8α- DCs DCs and plasmacytoid DCs increased with tumor progression. Moreover, increasing tumor burden was associated with reduced proliferation of tumor-antigen-specific CD8+ T cells in tumor-draining lymph nodes. This study shows that mesothelioma promotes DC lipid acquisition, which is associated with altered activation status and reduced capacity to process and present antigens, which may impair the ability of DCs to generate effective anti mesothelioma T cell responses.

Characterization of myeloid leukocytes and soluble mediators in pancreatic cancer: importance of myeloid-derived suppressor cells

Pancreatic ductal adenocarcinoma (PDAC) represents one of the deadliest cancers in the world. PDAC cells activate tumor-specific immune responses but simultaneously trigger a strong immunosuppression. We showed that PDAC cells produce high amount of chronic inflammatory mediators and PDAC tumors build an immunosuppressive cytokine milieu, which correlates with tumor progression. We observed a low frequency of dendritic cells (DC) and a pronounced accumulation of macrophages and myeloid-derived suppressor cells (MDSC) in murine PDAC tumors. A strong accumulation of MDSC has also been demonstrated in the peripheral blood of resected PDAC patients. While DC and macrophages seem not to play a significant role in this PDAC model in the context of immunosuppression, MDSC are highly suppressive, and their accumulation is associated with an increase in intratumoral VEGF concentration during the PDAC progression. Application of the phosphodiesterase-5 inhibitor sildenafil led to a prolonged survival of PDAC-bearing female mice, which was due to the decrease in MDSC frequencies and in the systemic VEGF level. This led to a restoration of anticancer immune responses, manifested in the recovery of T lymphocyte functions and in an increase in the frequency of conventional CD4⁺ T cells in tumors and IFNγ level in serum of PDAC-bearing mice. Thus, MDSC are strongly involved in the PDAC-associated immunosuppression and that their depletion could create new approaches for therapy of PDAC.

HMGB1 secretion during cervical carcinogenesis promotes the acquisition of a tolerogenic functionality by plasmacytoid dendritic cells

Acquisition of an impaired functionality by plasmacytoid dendritic cells (pDCs) contributing to cancer progression has been documented in different types of cancers. In the present study, we postulate that molecules secreted by (pre)neoplastic epithelial cells of the genital tract (cervix/vulva) might attract pDCs but also modify their proper functionality, allowing these cells to initiate a tolerogenic response interfering with antitumor immunity. We demonstrated that pDCs are recruited during the cervical metaplasia-dysplasia-cancer sequence, through the action of their chemoattractant, chemerin. We showed that stimulated-pDCs exposed to cervical/vulvar tumor microenvironment display an altered phenotype. We also demonstrated that cervical/vulvar neoplastic keratinocytes inhibit the proper function of pDCs by decreasing their IFNα secretion in response to CpG oligonucleotides. In parallel, we observed that (pre)neoplastic areas of the cervix are infiltrated by FoxP3(+) Treg cells which colocalize with pDCs. Accordingly, pDCs cocultured with cervical/vulvar neoplastic keratinocytes have the capacity to induce a Treg cell differentiation from naïve CD4(+) T cells, which is in agreement with the development of a tolerogenic response. We identified HMGB1 as a soluble factor produced by neoplastic keratinocytes from the genital tract involved in pDCs functional alteration. Indeed, this molecule inhibited pDC maturation, decreased IFNα secretion following TLR9 stimulation and forced these cells to become tolerogenic. In contrast, inhibition of HMGB1 restored pDC phenotype. Our findings indicate that the use of inhibitory molecules notably directed against HMGB1 in cervical/vulvar (pre)neoplastic lesions might prevent alterations of pDCs functionality and represent an attractive therapeutic strategy to overcome immune tolerance in cancers.

Tumor-infiltrating dendritic cells exhibit defective cross-presentation of tumor antigens, but is reversed by chemotherapy

Cross-presentation defines the unique capacity of an APC to present exogenous Ag via MHC class I molecules to CD8(+) T cells. DCs are specialized cross-presenting cells and as such have a critical role in antitumor immunity. DCs are routinely found within the tumor microenvironment, but their capacity for endogenous or therapeutically enhanced cross-presentation is not well characterized. In this study, we examined the tumor and lymph node DC cross-presentation of a nominal marker tumor Ag, HA, expressed by the murine mesothelioma tumor AB1-HA. We found that tumors were infiltrated by predominantly CD11b(+) DCs with a semimature phenotype that could not cross-present tumor Ag, and therefore, were unable to induce tumor-specific T-cell activation or proliferation. Although tumor-infiltrating DCs were able to take up, process, and cross-present exogenous cell-bound and soluble Ags, this was significantly impaired relative to lymph node DCs. Importantly, however, systemic chemotherapy using gemcitabine reversed the defect in Ag cross-presentation of tumor DCs. These data demonstrate that DC cross-presentation within the tumor microenvironment is defective, but can be reversed by chemotherapy. These results have important implications for anticancer therapy, particularly regarding the use of immunotherapy in conjunction with cytotoxic chemotherapy.

Complex role for the immune system in initiation and progression of pancreatic cancer

The immune system plays a complex role in the development and progression of pancreatic cancer. Inflammation can promote the formation of premalignant lesions and accelerate pancreatic cancer development. Conversely, pancreatic cancer is characterized by an immunosuppressive environment, which is thought to promote tumor progression and invasion. Here we review the current literature describing the role of the immune response in the progressive development of pancreatic cancer, with a focus on the mechanisms that drive recruitment and activation of immune cells at the tumor site, and our current understanding of the function of the immune cell types at the tumor. Recent clinical and preclinical data are reviewed, detailing the involvement of the immune response in pancreatitis and pancreatic cancer, including the role of specific cytokines and implications for disease outcome. Acute pancreatitis is characterized by a predominantly innate immune response, while chronic pancreatitis elicits an immune response that involves both innate and adaptive immune cells, and often results in profound systemic immune-suppression. Pancreatic adenocarcinoma is characterized by marked immune dysfunction driven by immunosuppressive cell types, tumor-promoting immune cells, and defective or absent inflammatory cells. Recent studies reveal that immune cells interact with cancer stem cells and tumor stromal cells, and these interactions have an impact on development and progression of pancreatic ductal adenocarcinoma (PDAC). Finally, current PDAC therapies are reviewed and the potential for harnessing the actions of the immune response to assist in targeting pancreatic cancer using immunotherapy is discussed.

Suppression of vascular endothelial growth factor abrogates the immunosuppressive capability of murine gastric cancer cells and elicits antitumor immunity

The mechanisms underlying immune evasion by gastric cancer have not been well described due to a lack of gastric tumor models in immunocompetent mice. In the current study, we found that supernatants from MFC cells, a murine gastric cancer line, inhibited the lipopolysaccharide (LPS) induced maturation and cross-presentation of bone-marrow-derived dendritic cells (BMDCs). Moreover, MFC tumor-derived factors markedly altered the cytokine profiles of BMDCs, leading to a trend of increased levels of interleukin 4 (IL4), IL6, IL23 and transforming growth factor β, as well as decreased levels of tumor necrosis factor α. qPCR and ELISA revealed that MFC cells expressed a high level of vascular endothelial growth factor (VEGF). Downregulating VEGF expression abrogated the inhibitory effect of MFC-derived factors on the maturation and cross-presentation of BMDCs. In addition, VEGF knockdown greatly impaired the tumorigenicity of MFC cells in immunocompetent mice. Compared with parental MFC tumors, VEGF-low MFC tumors grew much more slowly and the survival of tumor-inoculated mice was significantly improved. More importantly, mice rejecting inoculated VEGF-low MFC tumor cells gained resistance to re-challenged parental tumors, which was attributed to an antitumor immunity response against parental MFC tumors. These results reveal an immunosuppressive role for VEGF in murine gastric cancer.

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.

Orchestration of angiogenesis by immune cells

It is widely accepted that the tumor microenvironment (TUMIC) plays a major role in cancer and is indispensable for tumor progression. The TUMIC involves many "players" going well beyond the malignant-transformed cells, including stromal, immune, and endothelial cells (ECs). The non-malignant cells can acquire tumor-promoting functions during carcinogenesis. In particular, these cells can "orchestrate" the "symphony" of the angiogenic switch, permitting the creation of new blood vessels that allows rapid expansion and progression toward malignancy. Considerable attention within the context of tumor angiogenesis should focus not only on the ECs, representing a fundamental unit, but also on immune cells and on the inflammatory tumor infiltrate. Immune cells infiltrating tumors typically show a tumor-induced polarization associated with attenuation of anti-tumor functions and generation of pro-tumor activities, among these angiogenesis. Here, we propose a scenario suggesting that the angiogenic switch is an immune switch arising from the pro-angiogenic polarization of immune cells. This view links immunity, inflammation, and angiogenesis to tumor progression. Here, we review the data in the literature and seek to identify the "conductors" of this "orchestra." We also suggest that interrupting the immune → inflammation → angiogenesis → tumor progression process can delay or prevent tumor insurgence and malignant disease.