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

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.

Clinically relevant orthotopic pancreatic cancer models for adoptive T cell transfer therapy

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive tumor. Prognosis is poor and survival is low in patients diagnosed with this disease, with a survival rate of ~12% at 5 years. Immunotherapy, including adoptive T cell transfer therapy, has not impacted the outcomes in patients with PDAC, due in part to the hostile tumor microenvironment (TME) which limits T cell trafficking and persistence. We posit that murine models serve as useful tools to study the fate of T cell therapy. Currently, genetically engineered mouse models (GEMMs) for PDAC are considered a "gold-standard" as they recapitulate many aspects of human disease. However, these models have limitations, including marked tumor variability across individual mice and the cost of colony maintenance.

METHODS

Using flow cytometry and immunohistochemistry, we characterized the immunological features and trafficking patterns of adoptively transferred T cells in orthotopic PDAC (C57BL/6) models using two mouse cell lines, KPC-Luc and MT-5, isolated from C57BL/6 KPC-GEMM (KrasLSL-G12D/+p53-/- and KrasLSL-G12D/+p53LSL-R172H/+, respectively).

RESULTS

The MT-5 orthotopic model best recapitulates the cellular and stromal features of the TME in the PDAC GEMM. In contrast, far more host immune cells infiltrate the KPC-Luc tumors, which have less stroma, although CD4+ and CD8+ T cells were similarly detected in the MT-5 tumors compared with KPC-GEMM in mice. Interestingly, we found that chimeric antigen receptor (CAR) T cells redirected to recognize mesothelin on these tumors that signal via CD3ζ and 41BB (Meso-41BBζ-CAR T cells) infiltrated the tumors of mice bearing stroma-devoid KPC-Luc orthotopic tumors, but not MT-5 tumors.

CONCLUSIONS

Our data establish for the first time a reproducible and realistic clinical system useful for modeling stroma-rich and stroma-devoid PDAC tumors. These models shall serve an indepth study of how to overcome barriers that limit antitumor activity of adoptively transferred T cells.

An integrated overview of the immunosuppression features in the tumor microenvironment of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest malignancies. It is characterized by a complex and immunosuppressive tumor microenvironment (TME), which is primarily composed of tumor cells, stromal cells, immune cells, and acellular components. The cross-interactions and -regulations among various cell types in the TME have been recognized to profoundly shape the immunosuppression features that meaningfully affect PDAC biology and treatment outcomes. In this review, we first summarize five cellular composition modules by integrating the cellular (sub)types, phenotypes, and functions in PDAC TME. Then we discuss an integrated overview of the cross-module regulations as a determinant of the immunosuppressive TME in PDAC. We also briefly highlight TME-targeted strategies that potentially improve PDAC therapy.

Tumor-associated myeloid cells in cancer immunotherapy

Tumor-associated myeloid cells (TAMCs) are among the most important immune cell populations in the tumor microenvironment, and play a significant role on the efficacy of immune checkpoint blockade. Understanding the origin of TAMCs was found to be the essential to determining their functional heterogeneity and, developing cancer immunotherapy strategies. While myeloid-biased differentiation in the bone marrow has been traditionally considered as the primary source of TAMCs, the abnormal differentiation of splenic hematopoietic stem and progenitor cells, erythroid progenitor cells, and B precursor cells in the spleen, as well as embryo-derived TAMCs, have been depicted as important origins of TAMCs. This review article provides an overview of the literature with a focus on the recent research progress evaluating the heterogeneity of TAMCs origins. Moreover, this review summarizes the major therapeutic strategies targeting TAMCs with heterogeneous sources, shedding light on their implications for cancer antitumor immunotherapies.

Neo-vascularization-based therapeutic perspectives in advanced ovarian cancer

The process of angiogenesis is well described for its potential role in the development of normal ovaries, and physiological functions as well as in the initiation, progression, and metastasis of ovarian cancer (OC). In advanced stages of OC, cancer cells spread outside the ovary to the pelvic, abdomen, lung, or multiple secondary sites. This seriously limits the efficacy of therapeutic options contributing to fatal clinical outcomes. Notably, a variety of angiogenic effectors are produced by the tumor cells to initiate angiogenic processes leading to the development of new blood vessels, which provide essential resources for tumor survival, dissemination, and dormant micro-metastasis of tumor cells. Multiple proangiogenic effectors and their signaling axis have been discovered and functionally characterized for potential clinical utility in OC. In this review, we have provided the current updates on classical and emerging proangiogenic effectors, their signaling axis, and the immune microenvironment contributing to the pathogenesis of OC. Moreover, we have comprehensively reviewed and discussed the significance of the preclinical strategies, drug repurposing, and clinical trials targeting the angiogenic processes that hold promising perspectives for the better management of patients with OC.

Modulation of T-cell function by myeloid-derived suppressor cells in hematological malignancies

Myeloid-derived suppressor cells (MDSCs) are pathologically activated neutrophils and monocytes that negatively regulate the immune response to cancer and chronic infections. Abnormal myelopoiesis and pathological activation of myeloid cells generate this heterogeneous population of myeloid-derived suppressor cells. They are characterized by their distinct transcription, phenotypic, biochemical, and functional features. In the tumor microenvironment (TME), myeloid-derived suppressor cells represent an important class of immunosuppressive cells that correlate with tumor burden, stage, and a poor prognosis. Myeloid-derived suppressor cells exert a strong immunosuppressive effect on T-cells (and a broad range of other immune cells), by blocking lymphocyte homing, increasing production of reactive oxygen and nitrogen species, promoting secretion of various cytokines, chemokines, and immune regulatory molecules, stimulation of other immunosuppressive cells, depletion of various metabolites, and upregulation of immune checkpoint molecules. Additionally, the heterogeneity of myeloid-derived suppressor cells in cancer makes their identification challenging. Overall, they serve as a major obstacle for many cancer immunotherapies and targeting them could be a favorable strategy to improve the effectiveness of immunotherapeutic interventions. However, in hematological malignancies, particularly B-cell malignancies, the clinical outcomes of targeting these myeloid-derived suppressor cells is a field that is still to be explored. This review summarizes the complex biology of myeloid-derived suppressor cells with an emphasis on the immunosuppressive pathways used by myeloid-derived suppressor cells to modulate T-cell function in hematological malignancies. In addition, we describe the challenges, therapeutic strategies, and clinical relevance of targeting myeloid-derived suppressor cells in these diseases.

Role of myeloid-derived suppressor cells in tumor recurrence

The establishment of primary tumor cells in distant organs, termed metastasis, is the principal cause of cancer mortality and is a crucial therapeutic target in oncology. Thus, it is critical to establish a better understanding of metastatic progression for the future development of improved therapeutic approaches. Indeed, such development requires insight into the timing of tumor cell dissemination and seeding of distant organs resulting in occult lesions. Following dissemination of tumor cells from the primary tumor, they can reside in niches in distant organs for years or decades, following which they can emerge as an overt metastasis. This timeline of metastatic dormancy is regulated by interactions between the tumor, its microenvironment, angiogenesis, and tumor antigen-specific T-cell responses. An improved understanding of the mechanisms and interactions responsible for immune evasion and tumor cell release from dormancy would help identify and aid in the development of novel targeted therapeutics. One such mediator of dormancy is myeloid derived suppressor cells (MDSC), whose number in the peripheral blood (PB) or infiltrating tumors has been associated with cancer stage, grade, patient survival, and metastasis in a broad range of tumor pathologies. Thus, extensive studies have revealed a role for MDSCs in tumor escape from adoptive and innate immune responses, facilitating tumor progression and metastasis; however, few studies have considered their role in dormancy. We have posited that MDSCs may regulate disseminated tumor cells resulting in resurgence of senescent tumor cells. In this review, we discuss clinical studies that address mechanisms of tumor recurrence including from dormancy, the role of MDSCs in their escape from dormancy during recurrence, the development of occult metastases, and the potential for MDSC inhibition as an approach to prolong the survival of patients with advanced malignancies. We stress that assessing the impact of therapies on MDSCs versus other cellular targets is challenging within the multimodality interventions required clinically.

The PD-L1 Expression and Tumor-Infiltrating Immune Cells Predict an Unfavorable Prognosis in Pancreatic Ductal Adenocarcinoma and Adenosquamous Carcinoma

The tumor microenvironment (TME) plays a vital role in the development, progression, and metastasis of pancreatic cancer (PC). The composition of the TME and its potential prognostic value remains to be fully understood, especially in adenosquamous carcinoma of pancreas (ASCP) patients. Immunohistochemistry was used to explore the clinical significance of CD3, CD4, CD8, FoxP3, and PD-L1 expression within the TME and to identify correlations with the prognosis of PC in a series of 29 patients with ASCP and 54 patients with pancreatic ductal adenocarcinoma (PDAC). Data from the Gene Expression Omnibus (GEO) and the Cancer Genome Atlas (TCGA) were accessed to obtain the scRNA-seq data and transcriptome profiles. Seurat was used to process the scRNA-seq data, and CellChat was used to analyze cell-cell communication. CIBERSORT was used to approximate the constitution of tumor-infiltrating immune cell (TICs) profiles. Higher levels of PD-L1 were linked with a shorter overall survival in ASCP (p = 0.0007) and PDAC (p = 0.0594). A higher expression of CD3+ and CD8+ T-cell infiltration was significantly correlated with a better prognosis in PC. By influencing the composition of tumor-infiltrating immune cells (TICs), high levels of PD-L1 expression are linked with a shorter overall survival in ASCP and PDAC.

Beyond Erectile Dysfunction: cGMP-Specific Phosphodiesterase 5 Inhibitors for Other Clinical Disorders

Cyclic guanosine monophosphate (cGMP), an important intracellular second messenger, mediates cellular functional responses in all vital organs. Phosphodiesterase 5 (PDE5) is one of the 11 members of the cyclic nucleotide phosphodiesterase (PDE) family that specifically targets cGMP generated by nitric oxide-driven activation of the soluble guanylyl cyclase. PDE5 inhibitors, including sildenafil and tadalafil, are widely used for the treatment of erectile dysfunction, pulmonary arterial hypertension, and certain urological disorders. Preclinical studies have shown promising effects of PDE5 inhibitors in the treatment of myocardial infarction, cardiac hypertrophy, heart failure, cancer and anticancer-drug-associated cardiotoxicity, diabetes, Duchenne muscular dystrophy, Alzheimer's disease, and other aging-related conditions. Many clinical trials with PDE5 inhibitors have focused on the potential cardiovascular, anticancer, and neurological benefits. In this review, we provide an overview of the current state of knowledge on PDE5 inhibitors and their potential therapeutic indications for various clinical disorders beyond erectile dysfunction.

Innate immunity in pancreatic cancer: Lineage tracing and function

Increasingly, patients with gastrointestinal tumors can benefit from immunotherapy, but not patients with pancreatic cancer. While this lack of benefit has been attributed to lower T-cell infiltration in pancreatic cancer, other studies have demonstrated the presence of numerous T cells in pancreatic cancer, suggesting another mechanism for the poor efficacy of immunotherapy. Single-cell RNA sequencing studies on the pancreatic cancer immune microenvironment have demonstrated the predominance of innate immune cells (e.g., macrophages, dendritic cells, mast cells, and innate immune lymphoid cells). Therefore, in-depth research on the source and function of innate immune lymphocytes in pancreatic cancer could guide pancreatic cancer immunotherapy.

The Role of Myeloid-Derived Suppressor Cells in the Treatment of Pancreatic Cancer

Pancreatic cancer has the highest mortality rate of all major cancers, with a 5-year survival rate of about 10%. Early warning signs and symptoms of pancreatic cancer are vague or nonexistent, and most patients are diagnosed in Stage IV, when surgery is not an option for about 80%-85% of patients. For patients with inoperable pancreatic cancer, current conventional treatment modalities such as chemotherapy and radiotherapy (RT) have suboptimal efficacy. Tumor progression is closely associated with the tumor microenvironment, which includes peripheral blood vessels, bone marrow-derived inflammatory cells, fibroblasts, immune cells, signaling molecules, and extracellular matrix. Tumor cells affect the microenvironment by releasing extracellular signaling molecules, inducing peripheral immune tolerance, and promoting tumor angiogenesis. In turn, the immune cells of the tumor affect the survival and proliferation of cancer cells. Myeloid-derived suppressor cells are key cellular components in the tumor microenvironment and exert immunosuppressive functions by producing cytokines, recognizing other immune cells, and promoting tumor growth and metastasis. Myeloid-derived suppressor cells are the main regulator of the tumor immune response and a key target for tumor treatments. Since the combination of RT and immunotherapy is the main strategy for the treatment of pancreatic cancer, it is very important to understand the immune mechanisms which lead to MDSCs generation and the failure of current therapies in order to develop new target-based therapies. This review summarizes the research advances on the role of Myeloid-derived suppressor cells in the progression of pancreatic cancer and its treatment application in recent years.

Tumour inhibitory activity on pancreatic cancer by bispecific nanobody targeting PD-L1 and CXCR4

Background:

Antibodies and derivative drugs targeting immune checkpoints have been approved for the treatment of several malignancies, but there are fewer responses in patients with pancreatic cancer. Here, we designed a nanobody molecule with bi-targeting on PD-L1 and CXCR4, as both targets are overexpressed in many cancer cells and play important roles in tumorigenesis. We characterized the biochemical and anti-tumour activities of the bispecific nanobodies in vitro and in vivo.

Methods:

A nanobody molecule was designed and constructed. The nanobody sequences targeting PD-L1 and CXCR4 were linked by the (G₄S)₃ flexible peptide to construct the anti-PD-L1/CXCR4 bispecific nanobody. The bispecific nanobody was expressed in E. coli cells and purified by affinity chromatography. The purified nanobody was biochemically characterized by mass spectrometry, Western blotting and flow cytometry to confirm the molecule and its association with both PD-L1 and CXCR4. The biological function of the nanobody and its anti-tumour effects were examined by an in vitro tumour cell-killing assay and in vivo tumour inhibition in mouse xenograft models.

Results:

A novel anti-PD-L1/CXCR4 bispecific nanobody was designed, constructed and characterized. The molecule specifically bound to two targets on the surface of human cancer cells and inhibited CXCL12-induced Jurkat cell migration. The bispecific nanobody increased the level of IFN-γ secreted by T-cell activation. The cytotoxicity of human peripheral blood mononuclear cells (hPBMCs) against pancreatic cancer cells was enhanced by the molecule in combination with IL-2. In a human pancreatic cancer xenograft model, the anti-PD-L1/CXCR4 nanobody markedly inhibited tumour growth and was superior to the combo-treatment by anti-PD-L1 nanobody and anti-CXCR4 nanobody or treatment with atezolizumab as a positive control. Immunofluorescence and immunohistochemical staining of xenograft tumours showed that the anti-tumour effects were associated with the inhibition of angiogenesis and the infiltration of immune cells.

Conclusion:

These results clearly revealed that the anti-PD-L1/CXCR4 bispecific nanobody exerted anti-tumour efficacy in vitro and inhibited tumour growth in vivo. This agent can be further developed as a therapeutic reagent to treat human pancreatic cancer by simultaneously blocking two critical targets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10165-7.

Immunosuppressive effects of vascular endothelial growth factor (Review)

Vascular endothelial growth factor (VEGF) serves a critical role in vasculogenesis, angiogenesis, tumor, inflammatory angiogenesis and lymphangiogenesis. Since 2004, bevacizumab (Avastin), a humanized anti-VEGFA monoclonal antibody, has been approved for the treatment of non-small cell lung, breast, kidney and ovarian cancer in combination with standard chemotherapy. VEGF has been demonstrated to be important in the clinic as a therapeutic target in the anti-angiogenic approach to cancer therapy. The targeting of VEGF, together with immunotherapy, has been reported to be able to reverse the immunosuppressive effects of VEGF. A positive correlation between VEGF expression and the reduced survival rates of patients with cancer has also been demonstrated. Furthermore, increased VEGF expression can lead to immune suppression via the inhibition of dendritic cell maturation, the reduction of T-cell tumor infiltration and the promotion of inhibitory cell types in the tumor microenvironment.

Using Single Cell Transcriptomics to Elucidate the Myeloid Compartment in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is a dismal disease with a 5-year survival rate of 10%. A hallmark feature of this disease is its abundant microenvironment which creates a highly immunosuppressive milieu. This is, in large part, mediated by an abundant infiltration of myeloid cells in the PDAC tumor microenvironment. Consequently, therapies that modulate myeloid function may augment the efficacy of standard of care for PDAC. Unfortunately, there is limited understanding about the various subsets of myeloid cells in PDAC, particularly in human studies. This review highlights the application of single-cell RNA sequencing to define the myeloid compartment in human PDAC and elucidate the crosstalk between myeloid cells and the other components of the tumor immune microenvironment.

Pivotal antitumor role of the immune checkpoint molecule B7-H1 in pancreatic cancer

Immune checkpoint molecule B7-H1 plays a decisive immune regulatory role in different pathologies including cancer, and manipulation of B7-H1 expression became an attractive approach in cancer immunotherapy. Pancreatic cancer (PDAC) is characterized by pronounced immunosuppressive environment and B7-H1 expression correlates with PDAC prognosis. However, the first attempts to diminish B7-H1 expression in patients were not so successful. This points the complicity of PDAC immunosuppressive network and requires further examinations. We investigated the effect of B7-H1 deficiency in PDAC. Our results clearly show that partial or complete B7-H1 inhibition in vivo let to reduced tumor volume and improved survival of PDAC-bearing mice. This oncological benefit is due to the abrogation of immunosuppression provided by MDSC, macrophages, DC and Treg, which resulted in simultaneous restoration of anti-tumor immune response, namely improved accumulation and functionality of effector-memory CD4 and CD8 T cells. Our results underline the potential of B7-H1 molecule to control immunosuppressive network in PDAC and provide new issues for further clinical investigations.

Natural killer T cell immunotherapy combined with IL-15-expressing oncolytic virotherapy and PD-1 blockade mediates pancreatic tumor regression

BACKGROUND

Pancreatic cancer is one of the leading causes of cancer death, with a 5-year -year survival rate of less than 10%. This results from late detection, high rates of metastasis, and resistance to standard chemotherapies. Furthermore, chemotherapy and radiation are associated with significant morbidity, underscoring the need for novel therapies. Recent clinical studies have shown that immunotherapies can provide durable outcomes in cancer patients, but successes in pancreatic cancer have been limited. It is likely that novel and combined therapies will be needed to achieve clinical benefits.

METHODS

Using experimental mouse models of pancreatic ductal adenocarcinoma, we examined natural killer T (NKT) cell activation therapy in combination with a recombinant oncolytic vesicular stomatitis virus (VSVΔM51) engineered to express the cytokine IL-15 (VSV-IL-15). Panc02 pancreatic ductal carcinoma cells were implanted subcutaneously or orthotopically into syngeneic C57BL/6 mice. Mice were then treated with VSV expressing green fluorescent protein (VSV-GFP) or VSV-IL-15 and/or NKT cell activation therapy via delivery of α-GalCer-loaded DCs. We further assessed whether the addition of PD-1 blockade could increase the therapeutic benefit of our combination treatment. Three days after NKT cell activation, some groups of mice were treated with anti-PD-1 antibodies weekly for 3 weeks.

RESULTS

VSV-GFP and VSV-IL-15 mediated equal killing of human and mouse pancreatic cancer lines in vitro. In vivo, VSV-IL-15 combined with NKT cell activation therapy to enhance tumor regression and increase survival time over individual treatments, and was also superior to NKT cell therapy combined with VSV-GFP. Enhanced tumor control was associated with increased immune cell infiltration and anti-tumor effector functions (cytotoxicity and cytokine production). While ineffective as a monotherapy, the addition of blocking PD-1 antibodies to the combined protocol sustained immune cell activation and effector functions, resulting in prolonged tumor regression and complete tumor clearance in 20% of mice. Mice who cleared the initial tumor challenge exhibited reduced tumor growth uponon rechallenge, consistent with the formation of immune memory.

CONCLUSION

TThese results demonstrate that NKT cell immunotherapy combined with oncolytic VSV-IL-15 virotherapy and PD-1 blockade enhances tumor control and presents a promising treatment strategy for targeting pancreatic cancer.

Pancreatic Ductal Adenocarcinoma Cortical Mechanics and Clinical Implications

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest cancers due to low therapeutic response rates and poor prognoses. Majority of patients present with symptoms post metastatic spread, which contributes to its overall lethality as the 4th leading cause of cancer-related deaths. Therapeutic approaches thus far target only one or two of the cancer specific hallmarks, such as high proliferation rate, apoptotic evasion, or immune evasion. Recent genomic discoveries reveal that genetic heterogeneity, early micrometastases, and an immunosuppressive tumor microenvironment contribute to the inefficacy of current standard treatments and specific molecular-targeted therapies. To effectively combat cancers like PDAC, we need an innovative approach that can simultaneously impact the multiple hallmarks driving cancer progression. Here, we present the mechanical properties generated by the cell’s cortical cytoskeleton, with a spotlight on PDAC, as an ideal therapeutic target that can concurrently attack multiple systems driving cancer. We start with an introduction to cancer cell mechanics and PDAC followed by a compilation of studies connecting the cortical cytoskeleton and mechanical properties to proliferation, metastasis, immune cell interactions, cancer cell stemness, and/or metabolism. We further elaborate on the implications of these findings in disease progression, therapeutic resistance, and clinical relapse. Manipulation of the cancer cell’s mechanical system has already been shown to prevent metastasis in preclinical models, but it has greater potential for target exploration since it is a foundational property of the cell that regulates various oncogenic behaviors.

Myeloid-Derived Suppressor Cells in Solid Tumors

Myeloid-derived suppressor cells (MDSCs) are one of the main suppressive cell population of the immune system. They play a pivotal role in the establishment of the tumor microenvironment (TME). In the context of cancers or other pathological conditions, MDSCs can differentiate, expand, and migrate in large quantities during circulation, inhibiting the cytotoxic functions of T cells and NK cells. This process is regulated by ROS, iNOS/NO, arginase-1, and multiple soluble cytokines. The definition of MDSCs and their phenotypes in humans are not as well represented as in other organisms such as mice, owing to the absence of the cognate molecule. However, a comprehensive understanding of the differences between different species and subsets will be beneficial for clarifying the immunosuppressive properties and potential clinical values of these cells during tumor progression. Recently, experimental evidence and clinical investigations have demonstrated that MDSCs have a close relationship with poor prognosis and drug resistance, which is considered to be a leading marker for practical applications and therapeutic methods. In this review, we summarize the remarkable position of MDSCs in solid tumors, explain their classifications in different models, and introduce new treatment approaches to target MDSCs to better understand the advancement of new approaches to cancer treatment.

CpG Oligodeoxynucleotides for Anticancer Monotherapy from Preclinical Stages to Clinical Trials

CpG oligodeoxynucleotides (CpG ODNs), the artificial versions of unmethylated CpG motifs that were originally discovered in bacterial DNA, are demonstrated not only as potent immunoadjuvants but also as anticancer agents by triggering toll-like receptor 9 (TLR9) activation in immune cells. TLR9 activation triggered by CpG ODN has been shown to activate plasmacytoid dendritic cells (pDCs) and cytotoxic T lymphocytes (CTLs), enhancing T cell-mediated antitumor immunity. However, the extent of antitumor immunity carried by TLR agonists has not been optimized individually or in combinations with cancer vaccines, resulting in a decreased preference for TLR agonists as adjuvants in clinical trials. Although various combination therapies involving CpG ODNs have been applied in clinical trials, none of the CpG ODN-based drugs have been approved by the FDA, owing to the short half-life of CpG ODNs in serum that leads to low activation of natural killer cells (NK cells) and CTLs, along with increases of pro-inflammatory cytokine productions. This review summarized the current innovation on CpG ODNs that are under clinical investigation and explored the future direction for CpG ODN-based nanomedicine as an anticancer monotherapy.

CCL28 Downregulation Attenuates Pancreatic Cancer Progression Through Tumor Cell-Intrinsic and -Extrinsic Mechanisms

C-C motif chemokine ligand 28 (CCL28) has been reported to be pro-tumoral in several cancer types. However, the role of CCL28 in pancreatic ductal adenocarcinoma (PDAC) progression remains unclear. CCL28 mRNA expression in tumors from PDAC patients was found to be elevated as compared to normal pancreas. CCL28 expression was also negatively correlated with overall survival (OS) in pancreatic cancer patients. Our in vitro experiments showed that CCL28 knockdown impairs the proliferation of mouse pancreatic cancer cell line PAN02. Moreover, in both immunocompetent syngeneic mice and immunodeficient NOD-SCID mice, CCL28 deficiency significantly attenuated the growth of subcutaneous PAN02 tumors. In syngeneic mouse model, CCL28 downregulation remodeled the pancreatic tumor microenvironment by suppressing the infiltration of both regulatory T (Treg) cells, myeloid-derived suppressor cells, and activated pancreatic stellate cells, and upregulating the expression of lymphocyte cytotoxic proteins including perforin and granzyme B. In conclusion, our work demonstrates that CCL28 is a potential target for pancreatic cancer treatment and CCL28 blockade could inhibit tumor growth through both tumor-cell-intrinsic and extrinsic mechanisms.

Systemic Interleukins' Profile in Early and Advanced Colorectal Cancer

Tumor microenvironment (TME) is characterized by mutual interactions of the tumor, stromal and immune cells. Early and advanced colorectal tumors differ in structure and present altered serum cytokine levels. Mutual crosstalk among TME infiltrating cells may shift the balance into immune suppressive or pro-inflammatory, antitumor response this way influencing patients' prognosis. Cancer-related inflammation affects all the body and this way, the systemic level of cytokines could reflect TME processes. Despite numerous studies, it is still not known how systemic cytokines levels change during colorectal cancer (CRC) tumor development. Better understanding tumor microenvironment processes could help in planning therapeutic interventions and more accurate patient prognosis. To contribute to the comprehension of these processes within TME, we reviewed cytokines levels from clinical trials in early and advanced colorectal cancer. Presented data were analyzed in the context of experimental studies and studies analyzing tumor infiltration with immune cells. The review summarizes clinical data of cytokines secreted by tumor microenvironment cells: lymphocytes T helper 1 (Th1), lymphocytes T helper 2 (Th2), lymphocytes T helper 17 (Th17), regulatory T cells (Treg cells), regulatory T cells (Breg cells), M1/M2 macrophages, N1/N2 neutrophils, myeloid-derived suppressor cells (MDSC), dendritic cells (DC), innate lymphoid cells (ILC) natural killer (NK) cells and tumor cells.

TNFSF9 promotes metastasis of pancreatic cancer by regulating M2 polarization of macrophages through Src/FAK/p-Akt/IL-1β signaling

The effect of tumor necrosis factor superfamily member 9 (TNFSF9) on the metastasis of pancreatic cancer (PC) and the underlying mechanism remain unclear. We studied the expression of TNFSF9 in pancreatic cancer and its relationship with immune cells. We further explored the effect of TNFSF9 on pancreatic cancer metastasis by inducing macrophage polarization, and evaluated the expression of Src/FAK/p-Akt/IL-1β signals in macrophages after knocking down TNFSF9. The data shows that TNFSF9 expression is elevated in pancreatic cancer and is related to the poor prognosis of patients with pancreatic cancer. In addition, TNFSF9 may induce the M2 polarization of macrophages through Src/FAK/p-Akt/IL-1β signals, thereby promoting the migration of pancreatic cancer cells. In conclusion, our data reveals that TNFSF9 may become a predictive biomarker of pancreatic cancer and provides a new intervention target for the immunotherapy of pancreatic cancer.

Dietary inflammatory index and pancreatic cancer risk: a systematic review and dose-response meta-analysis

OBJECTIVE

The meta-analysis was conducted to test the link between pancreatic cancer (PC) risk and dietary inflammatory index (DII®) score.

DESIGN

Systematic review and meta-analysis.

SETTING

We searched PubMed, Embase, Web of Science and the Cochrane Library up to 22 November 2020 to identify the relevant studies. Studies that reported the risk estimates and the corresponding 95 % CI for the DII category and PC risk were included. The effect sizes were pooled using the random-effects model. Dose-response analysis was conducted where possible.

PARTICIPANTS

Two prospective cohort studies of 634 705 participants (3152 incident cases), and four case-control studies of 2737 cases and 4861 controls.

RESULTS

Overall, the pooled risk ratio (RR) indicated that individuals in the highest category compared with the lowest category had an increased PC risk (RR = 1·45; 95 % CI 1·11, 1·90; P = 0·006). Meanwhile, significant heterogeneity was also revealed. The dose-response meta-analysis indicated that a 1-unit increase in the DII score was associated with the PC risk (RR = 1·08; 95 % CI 1·002, 1·166; P = 0·045; I2 = 94·1 %, P < 0·001). Nonlinear result showed an increased risk of moving from fewer to more inflammatory borders with increasing DII score (Pnonlinearity = 0·003; I2 = 76·5 %, P < 0·001). Subgroup analyses found that significant positive association between PC risk and DII score appeared to be in case-control studies (RR = 1·70; 95 % CI 1·16, 2·50; P = 0·007) and studies with ≤ 31 DII components (RR = 1·76; 95 % CI 1·14, 2·72; P = 0·011).

CONCLUSION

These findings suggested dietary habits with high inflammatory features (high DII score) might increase PC risk.

Probiotics in Counteracting the Role of Neutrophils in Cancer Metastasis

Neutrophils are known for their role geared towards pathogen clearance by different mechanisms that they initiate, primarily by the release of neutrophil extracellular traps (NETs). However, their immune-surveillance capacity accompanied with plasticity in existing as interchangeable subsets, discovered recently, has revealed their property to contribute to complex cancer pathologies including tumor initiation, growth, angiogenesis and metastasis. Although there is a growing body of evidence suggesting a critical balance between the protumoral and antitumoral neutrophil phenotypes, an in-depth signaling pathway analysis would aid in determination of anticipatory, diagnostic and therapeutic targets. This review presents a comprehensive overview of the potential pathways involved in neutrophil-triggered cancer metastasis and introduces the influence of the microbial load and avenues for probiotic intervention.

The tumor microenvironment in pancreatic ductal adenocarcinoma: current perspectives and future directions

Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal malignancies and is characterized by a unique tumor microenvironment (TME) consisting of an abundant stromal component. Many features contained with the PDAC stroma contribute to resistance to cytotoxic and immunotherapeutic regimens, as well as the propensity for this tumor to metastasize. At the cellular level, PDAC cells crosstalk with a complex mixture of non-neoplastic cell types including fibroblasts, endothelial cells, and immune cells. These intricate interactions fuel the progression and therapeutic resistance of this aggressive cancer. Moreover, data suggest the polarization of these cell types, in particular immune and fibroblast populations, dictate how PDAC tumors grow, metastasize, and respond to therapy. As a result, current research is focused on how to best target these populations to render tumors responsive to treatment. Herein, we summarize the cell populations implicated in providing a supporting role for the development and progression of PDAC. We focus on stromal fibroblasts and immune subsets that have been widely researched. We discuss factors which govern the phenotype of these populations and provide insight on how they have been targeted therapeutically. This review provides an overview of the tumor microenvironment and postulates that cellular and soluble factors within the microenvironment can be specifically targeted to improve patient outcomes.

Obesity Promotes Tumor Immune Evasion in Ovarian Cancer Through Increased Production of Myeloid-Derived Suppressor Cells via IL-6

Background

Obesity is defined as a chronic, low-grade inflammatory disease that can cause obesity-associated disorders, such as cancer. Obesity has traditionally been thought to be a risk factor for ovarian cancer. Few reports have focused on the specific pathogenesis of obesity-related ovarian cancer. When considering the correlation between obesity and the relative risk of death from ovarian cancer, we investigated whether obesity promotes tumor immune escape in ovarian cancer.

Results

In the present study, obese mice were found to have higher rates of tumor growth and tumor infiltration than mice of normal weight. Obesity increased the proportion of myeloid-derived suppressor cells (MDSCs) in peripheral blood compared with mice of normal weight. In addition, the levels of CCL25, CD40L, GM-CSF, IL-5, IGFBP2, IL-6, MMP3, and MMP9 in the peripheral blood, bone marrow, and ovarian tissue of obese mice were higher than in mice of normal weight. Moreover, IL-5 and IL-6 significantly enhanced the expression levels of S100A8 and S100A9 in MDSCs. When compared with the levels in mice of normal weight, the expression levels of S100A8 and S100A9 in the MDSCs of OB/OB mice were also higher within the tumor microenvironment. The infiltration of MDSCs in ovarian cancer was found to be positively correlated with the expression levels of IL-6. The IL-6 expression levels in ovarian cancer tissue are positively correlated with the expression levels of S100A8 and S100A9, which is consistent with the results of previous animal experiments. Finally, we found that LMT28 can suppress the tumor growth by inhibiting IL-6.

Conclusion

Obesity promotes the expression of the MDSC-related immunosuppressive genes S100A8 and S100A9 by upregulating IL-6, thus promoting tumor immune evasion and metastasis in ovarian cancer.

Arginase 1-Based Immune Modulatory Vaccines Induce Anticancer Immunity and Synergize with Anti-PD-1 Checkpoint Blockade

Expression of the L-arginine catabolizing enzyme arginase 1 (ARG1) is a central immunosuppressive mechanism mediated by tumor-educated myeloid cells. Increased activity of ARG1 promotes the formation of an immunosuppressive microenvironment and leads to a more aggressive phenotype in many cancers. Intrinsic T-cell immunity against ARG1-derived epitopes in the peripheral blood of cancer patients and healthy subjects has previously been demonstrated. To evaluate the antitumor efficacy of ARG1-derived peptide vaccines as a monotherapy and as a combinational therapy with checkpoint blockade, different in vivo syngeneic mouse tumor models were utilized. To evaluate the antitumor effects, flow cytometry analysis and IHC were performed on tumors, and ELISPOT assays were performed to characterize immune responses. We show that ARG1-targeting therapeutic vaccines were able to activate endogenous antitumor immunity in several in vivo syngeneic mouse tumor models and to modulate the cell composition of the tumor microenvironment without causing any associated side effects or systemic toxicity. ARG1-targeting vaccines in combination with anti-PD-1 also resulted in increased T-cell infiltration, decreased ARG1 expression, reduced suppressive function of tumor-educated myeloid cells, and a shift in the M1/M2 ratio of tumor-infiltrating macrophages. These results indicated that the induced shift toward a more proinflammatory microenvironment by ARG1-targeting immunotherapy favors effective tumor control when combined with anti-PD-1 checkpoint blockade. Our data illustrate the ability of ARG1-based immune modulatory vaccination to elicit antigen-specific immunosurveillance and imply the feasibility of this novel immunotherapeutic approach for clinical translation.

Antiangiogenic therapy reverses the immunosuppressive breast cancer microenvironment

Tumor angiogenesis induces local hypoxia and recruits immunosuppressive cells, whereas hypoxia subsequently promotes tumor angiogenesis. Immunotherapy efficacy depends on the accumulation and activity of tumor-infiltrating immune cells (TIICs). Antangiogenic therapy could improve local perfusion, relieve tumor microenvironment (TME) hypoxia, and reverse the immunosuppressive state. Combining antiangiogenic therapy with immunotherapy might represent a promising option for the treatment of breast cancer. This article discusses the immunosuppressive characteristics of the breast cancer TME and outlines the interaction between the tumor vasculature and the immune system. Combining antiangiogenic therapy with immunotherapy could interrupt abnormal tumor vasculature-immunosuppression crosstalk, increase effector immune cell infiltration, improve immunotherapy effectiveness, and reduce the risk of immune-related adverse events. In addition, we summarize the preclinical research and ongoing clinical research related to the combination of antiangiogenic therapy with immunotherapy, discuss the underlying mechanisms, and provide a view for future developments. The combination of antiangiogenic therapy and immunotherapy could be a potential therapeutic strategy for treatment of breast cancer to promote tumor vasculature normalization and increase the efficiency of immunotherapy.

Extracellular Vesicles and Pancreatic Cancer: Insights on the Roles of miRNA, lncRNA, and Protein Cargos in Cancer Progression

Pancreatic cancer (PC) is among the most devastating digestive tract cancers worldwide. This cancer is characterized by poor diagnostic detection, lack of therapy, and difficulty in predicting tumorigenesis progression. Although mutations of key oncogenes and oncosuppressor involved in tumor growth and in immunosurveillance escape are known, the underlying mechanisms that orchestrate PC initiation and progression are poorly understood or still under debate. In recent years, the attention of many researchers has been concentrated on the role of extracellular vesicles and of a particular subset of extracellular vesicles, known as exosomes. Literature data report that these nanovesicles are able to deliver their cargos to recipient cells playing key roles in the pathogenesis and progression of many pancreatic precancerous conditions. In this review, we have summarized and discussed principal cargos of extracellular vesicles characterized in PC, such as miRNAs, lncRNAs, and several proteins, to offer a systematic overview of their function in PC progression. The study of extracellular vesicles is allowing to understand that investigation of their secretion and analysis of their content might represent a new and potential diagnostic and prognostic tools for PC.

Myeloid derived suppressor cells and the release of micro-metastases from dormancy

Metastasis is the primary cause of cancer mortality and an improved understanding of its pathology is critical to the development of novel therapeutic approaches. Mechanism-based therapeutic strategies require insight into the timing of tumor cell dissemination, seeding of distant organs, formation of occult lesions and critically, their release from dormancy. Due to imaging limitations, primary tumors can only be detected when they reach a relatively large size (e.g. > 1 cm³), which, based on our understanding of tumor evolution, occurs approximately 10 years and about 30 doubling times following tumor initiation. Genomic profiling of paired primary tumors and metastases has suggested that tumor seeding at secondary sites occurs early during tumor progression and frequently, years prior to clinical diagnosis. Following seeding, tumor cells may enter into and remain in a dormant state, and if they survive and are released from dormancy, they can proliferate into an overt lesion. The timeline of tumor initiation and metastatic dormancy is regulated by tumor interactions with its microenvironment, angiogenesis, and tumor-specific cytotoxic T-lymphocyte (CTL) responses. Therefore, a better understanding of the cellular interactions responsible for immune evasion and/or tumor cell release from dormancy would facilitate the development of therapeutics targeted against this critical part of tumor progression. The immunosuppressive mechanisms mediated by myeloid-derived suppressor cells (MDSCs) contribute to tumor progression and, we posit, promote tumor cell escape from CTL-associated dormancy. Thus, while clinical and translational research has demonstrated a role for MDSCs in facilitating tumor progression and metastasis through tumor escape from adoptive and innate immune responses (T-, natural killer and B-cell responses), few studies have considered the role of MDSCs in tumor release from dormancy. In this review, we discuss MDSC expansion, driven by tumor burden associated growth factor secretion and their role in tumor cell escape from dormancy, resulting in manifest metastases. Thus, the therapeutic strategies to inhibit MDSC expansion and function may provide an approach to delay metastatic relapse and prolong the survival of patients with advanced malignancies.

Natural Killer Cell Interactions With Myeloid Derived Suppressor Cells in the Tumor Microenvironment and Implications for Cancer Immunotherapy

The tumor microenvironment (TME) is a complex and heterogeneous environment composed of cancer cells, tumor stroma, a mixture of tissue-resident and infiltrating immune cells, secreted factors, and extracellular matrix proteins. Natural killer (NK) cells play a vital role in fighting tumors, but chronic stimulation and immunosuppression in the TME lead to NK cell exhaustion and limited antitumor functions. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of myeloid cells with potent immunosuppressive activity that gradually accumulate in tumor tissues. MDSCs interact with innate and adaptive immune cells and play a crucial role in negatively regulating the immune response to tumors. This review discusses MDSC-mediated NK cell regulation within the TME, focusing on critical cellular and molecular interactions. We review current strategies that target MDSC-mediated immunosuppression to enhance NK cell cytotoxic antitumor activity. We also speculate on how NK cell-based antitumor immunotherapy could be improved.

Vascular Endothelial Growth Factor, a Key Modulator of the Anti-Tumor Immune Response

During tumor growth, angiogenesis is required to ensure oxygen and nutrient transport to the tumor. Vascular endothelial growth factor (VEGF) is the major inducer of angiogenesis and appears to be a key modulator of the anti-tumor immune response. Indeed, VEGF modulates innate and adaptive immune responses through direct interactions and indirectly by modulating protein expressions on endothelial cells or vascular permeability. The inhibition of the VEGF signaling pathway is clinically approved for the treatment of several cancers. Therapies targeting VEGF can modulate the tumor vasculature and the immune response. In this review, we discuss the roles of VEGF in the anti-tumor immune response. In addition, we summarize therapeutic strategies based on its inhibition, and their clinical approval.

Myeloid-derived suppressor cells: Bridging the gap between inflammation and pancreatic adenocarcinoma

Pancreatic cancer has been identified as one of the deadliest malignancies because it remains asymptomatic and usually presents in the advanced stage. Tumour immune evasion is a well-known mechanism of tumorigenesis in various forms of human malignancies. Chronic inflammation via complex networking of various inflammatory cytokines in the local tissue microenvironment dysregulates the immune system and support tumour development. Pro-inflammatory mediators present in the tumour microenvironment increase the tumour burden by causing immune suppression through the generation of myeloid-derived suppressor cells (MDSCs) and T regulatory cells. These cells, along-with myofibroblasts, create a highly immunosuppressive and resistant tumour microenvironment and are thus considered as one of the culprits for the failure of anti-cancer chemotherapies in pancreatic adenocarcinoma patients. Targeting these MDSCs using various combinatorial approaches might have the potential for abrogating the resistance and suppressive nature of the pancreatic tumour microenvironment. Therefore, there is more curiosity in studying the crosstalk of MDSCs with other immune cells during pathological conditions and the underlying mechanisms of immunosuppression in the current scenario. In this article, the possible role of MDSCs in inflammation-mediated tumour progression of pancreatic adenocarcinoma has been discussed.

Combined Effects of Myeloid Cells in the Neuroblastoma Tumor Microenvironment

Despite multimodal treatment, survival chances for high-risk neuroblastoma patients remain poor. Immunotherapeutic approaches focusing on the activation and/or modification of host immunity for eliminating tumor cells, such as chimeric antigen receptor (CAR) T cells, are currently in development, however clinical trials have failed to reproduce the preclinical results. The tumor microenvironment is emerging as a major contributor to immune suppression and tumor evasion in solid cancers and thus has to be overcome for therapies relying on a functional immune response. Among the cellular components of the neuroblastoma tumor microenvironment, suppressive myeloid cells have been described as key players in inhibition of antitumor immune responses and have been shown to positively correlate with more aggressive disease, resistance to treatments, and overall poor prognosis. This review article summarizes how neuroblastoma-driven inflammation induces suppressive myeloid cells in the tumor microenvironment and how they in turn sustain the tumor niche through suppressor functions, such as nutrient depletion and generation of oxidative stress. Numerous preclinical studies have suggested a range of drug and cellular therapy approaches to overcome myeloid-derived suppression in neuroblastoma that warrant evaluation in future clinical studies.

Trials and tribulations of pancreatic cancer immunotherapy

Immunotherapy has revolutionized cancer treatment in the last decade, and strategies to re-activate cytotoxic immunity are now standard of care in several malignancies. Despite rapid advances in immunotherapy for most solid cancers, progress in immunotherapy against pancreatic ductal adenocarcinoma (PDAC) has been exceptionally difficult. This is true for several approaches, most notably immune checkpoint inhibitors (ICIs) and GM-CSF cell-based vaccines (GVAX). Though many immunotherapies have been explored in clinical trials, few have shown significant therapeutic efficacy. Further, many have shown high rates of serious adverse effects and dose-limiting toxicities, and to date, immunotherapy regimens have not been successfully implemented in PDAC. Here, we provide a comprehensive summary of the key clinical trials exploring immunotherapy in PDAC, followed by a brief discussion of emerging molecular mechanisms that may explain the relative failure of immunotherapy in pancreas cancer thus far.

The Match between Molecular Subtypes, Histology and Microenvironment of Pancreatic Cancer and Its Relevance for Chemoresistance

In the last decade, several studies based on whole transcriptomic and genomic analyses of pancreatic tumors and their stroma have come to light to supplement histopathological stratification of pancreatic cancers with a molecular point-of-view. Three main molecular studies: Collisson et al. 2011, Moffitt et al. 2015 and Bailey et al. 2016 have found specific gene signatures, which identify different molecular subtypes of pancreatic cancer and provide a comprehensive stratification for both a personalized treatment or to identify potential druggable targets. However, the routine clinical management of pancreatic cancer does not consider a broad molecular analysis of each patient, due probably to the lack of target therapies for this tumor. Therefore, the current treatment decision is taken based on patients´ clinicopathological features and performance status. Histopathological evaluation of tumor samples could reveal many other attributes not only from tumor cells but also from their microenvironment specially about the presence of pancreatic stellate cells, regulatory T cells, tumor-associated macrophages, myeloid derived suppressor cells and extracellular matrix structure. In the present article, we revise the four molecular subtypes proposed by Bailey et al. and associate each subtype with other reported molecular subtypes. Moreover, we provide for each subtype a potential description of the tumor microenvironment that may influence treatment response according to the gene expression profile, the mutational landscape and their associated histology.

Targeting Aggressive Fibroblasts to Enhance the Treatment of Pancreatic Cancer

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) is one of the most malignant cancer entities, which is characterized by abundant desmoplastic stroma. The stroma consists of extracellular matrix, infiltrating immune cells, cancer-associated fibroblasts (CAFs) and others. Depending on environmental cues, CAFs can be highly heterogeneous and play context-dependent roles in PDAC progression.

AREAS COVERED

In this article, we discuss the biological significance of CAFs heterogeneity (oncogenic vs. tumor-suppressive) in pancreatic carcinogenesis. In particular, the complex interaction between CAFs and infiltrating immune cells has a determinant role in defining the stromal composition. A subset of PDAC patients may benefit from anti-CAFs therapy.

EXPERT OPINION

Co-defined by CAFs and infiltrating immune cells, the prognostic stroma signature is clinically relevant in a subset of human PDAC. This is the patient population which may benefit from future anti-stroma or anti-CAFs therapies. To consider CAF heterogeneity is crucial for designing anti-stroma studies. Here, reliable and traceable subtype-specific markers for CAFs are urgently needed to dissect the biological impact of CAF heterogeneity on PDAC development spatiotemporally. Given the significant contribution of CAFs to immunosuppressive microenvironment of PDAC, it is conceivable to combine anti-CAFs therapy with immunotherapy. To implement a CAF-subtype specific therapy is crucially important to improve the effectiveness of current treatments including chemotherapies and immunotherapy.

The Role of TIM-3 in Hepatocellular Carcinoma: A Promising Target for Immunotherapy?

One of the most common tumors in the world is hepatocellular carcinoma (HCC), and its mortality rates are still on the rise, so addressing it is considered an important challenge for universal health. Despite the various treatments that have been developed over the past decades, the prognosis for advanced liver cancer is still poor. Recently, tumor immunotherapy has opened new opportunities for suppression of tumor progression, recurrence, and metastasis. Besides this, investigation into this malignancy due to high immune checkpoint expression and the change of immunometabolic programming in immune cells and tumor cells is highly considered. Because anti-cytotoxic T lymphocyte–associated protein (CTLA)-4 antibodies and anti-programmed cell death protein (PD)-1 antibodies have shown therapeutic effects in various cancers, studies have shown that T cell immunoglobulin mucin-3 (TIM-3), a new immune checkpoint molecule, plays an important role in the development of HCC. In this review, we summarize the recent findings on signal transduction events of TIM-3, its role as a checkpoint target for HCC therapy, and the immunometabolic situation in the progression of HCC.

Arginine metabolism: a potential target in pancreatic cancer therapy

ABSTRACT

Pancreatic ductal adenocarcinoma (PDAC) is an extremely malignant disease, which has an extremely low survival rate of <9% in the United States. As a new hallmark of cancer, metabolism reprogramming exerts crucial impacts on PDAC development and progression. Notably, arginine metabolism is altered in PDAC cells and participates in vital signaling pathways. In addition, arginine and its metabolites including polyamine, creatine, agmatine, and nitric oxide regulate the proliferation, growth, autophagy, apoptosis, and metastasis of cancer cells. Due to the loss of argininosuccinate synthetase 1 (ASS1) expression, the key enzyme in arginine biosynthesis, arginine deprivation is regarded as a potential strategy for PDAC therapy. However, drug resistance develops during arginine depletion treatment, along with the re-expression of ASS1, metabolic dysfunction, and the appearance of anti-drug antibody. Additionally, arginase 1 exerts crucial roles in myeloid-derived suppressor cells, indicating its potential targeting by cancer immunotherapy. In this review, we introduce arginine metabolism and its impacts on PDAC cells. Also, we discuss the role of arginine metabolism in arginine deprivation therapy and immunotherapy for cancer.

Combination of gemcitabine and anti-PD-1 antibody enhances the anticancer effect of M1 macrophages and the Th1 response in a murine model of pancreatic cancer liver metastasis

BACKGROUND

Pancreatic ductular adenocarcinoma (PDAC) is among the most dreadful of malignancies, in part due to the lack of efficacious chemotherapy. Immune checkpoint inhibitors, including anti-programmed cell death 1 (anti-PD-1) antibodies, are novel promising forms of systemic immunotherapy. In the current study, we assessed whether gemcitabine (GEM) combined with anti-PD-1 antibody treatment was efficacious as immunochemotherapy for advanced PDAC using a murine model of liver metastasis.

METHODS

The murine model of PDAC liver metastasis was established by intrasplenically injecting the murine pancreatic cancer cell line PAN02 into immunocompetent C57BL/6J mice. The mice were treated with an anti-PD-1 antibody, GEM, or a combination of GEM plus anti-PD-1 antibody, and compared with no treatment (control); liver metastases, immune cell infiltration, gene expression, immune cell response phenotypes, and overall survival were investigated.

RESULTS

In the metastatic tumor tissues of mice treated with GEM plus anti-PD-1 antibody, we observed the increased infiltration of Th1 lymphocytes and M1 macrophages. Gene expression profile analysis of peripheral blood cells obtained from mice treated with GEM plus anti-PD-1 antibody clearly highlighted T cell and innate immune signaling pathways. Survival of PDAC liver metastasis mice was significantly prolonged by the combination therapy (median survival, 66 days) when compared with that of GEM alone treatment (median survival, 56 days). Expanded lymphocytes, which were isolated from the splenocytes of PDAC liver metastasis mice treated with GEM plus anti-PD-1 antibody, had an increased number of M1 macrophages.

CONCLUSION

The combination of anti-PD-1 antibody immunotherapy with GEM was beneficial to treat a murine model of PDAC liver metastasis by enhancing the immune response mediated by Th1 lymphocytes and M1 macrophages and was associated with CD8+ T cells.

Sulforaphane Promotes Dendritic Cell Stimulatory Capacity Through Modulation of Regulatory Molecules, JAK/STAT3- and MicroRNA-Signaling

Introduction

The broccoli isothiocyanate sulforaphane was shown to inhibit inflammation and tumor progression, also in pancreatic cancer, while its effect on tumor immunity is poorly understood. We investigated the immunoregulatory effect of sulforaphane on human dendritic cells alone and in presence of pancreatic tumor antigens, as well as underlying molecular mechanisms.

Methods

Sulforaphane-treated human dendritic cells were matured in vitro with a cytokine cocktail, and the expression of regulatory molecules was examined by flow cytometry. The subsequent T-cell response was analyzed by T-cell proliferation assay and CD25 expression. To confirm the findings, dendritic cells pulsed with pancreatic cancer-derived tumor antigens were used. To identify the involved pathway- and microRNA-signaling in sulforaphane-treated dendritic cells, inhibitors of various signaling pathways, western blot analysis, microRNA array, and bioinformatic analysis were applied.

Results

Sulforaphane modulated the expression of the costimulatory CD80, CD83 and the suppressive B7-H1 molecules on dendritic cells and thereby promoted activation of T cells. The effect was verified in presence of pancreatic tumor antigens. Phosphorylation of STAT3 in dendritic cells was diminished by sulforaphane, and the inhibition of JAK/STAT3 led to downregulation of B7-H1 expression. Among the identified top 100 significant microRNA candidates, the inhibition of miR-155-5p, important for the expression of costimulatory molecules, and the induction of miR-194-5p, targeting the B7-H1 gene, were induced by sulforaphane.

Conclusion

Our findings demonstrate that sulforaphane promotes T-cell activation by dendritic cells through the modulation of regulatory molecules, JAK/STAT3- and microRNA-signaling in healthy conditions and in context of pancreatic cancer-derived antigens. They explore the immunoregulatory properties of sulforaphane and justify further research on nutritional strategies in the co-treatment of cancer.

Old Player-New Tricks: Non Angiogenic Effects of the VEGF/VEGFR Pathway in Cancer

Angiogenesis has long been considered to facilitate and sustain cancer growth, making the introduction of anti-angiogenic agents that disrupt the vascular endothelial growth factor/receptor (VEGF/VEGFR) pathway an important milestone at the beginning of the 21st century. Originally research on VEGF signaling focused on its survival and mitogenic effects towards endothelial cells, with moderate so far success of anti-angiogenic therapy. However, VEGF can have multiple effects on additional cell types including immune and tumor cells, by directly influencing and promoting tumor cell survival, proliferation and invasion and contributing to an immunosuppressive microenvironment. In this review, we summarize the effects of the VEGF/VEGFR pathway on non-endothelial cells and the resulting implications of anti-angiogenic agents that include direct inhibition of tumor cell growth and immunostimulatory functions. Finally, we present how previously unappreciated studies on VEGF biology, that have demonstrated immunomodulatory properties and tumor regression by disrupting the VEGF/VEGFR pathway, now provide the scientific basis for new combinational treatments of immunotherapy with anti-angiogenic agents.

Myeloid-Derived Suppressor Cells in Tumors: From Mechanisms to Antigen Specificity and Microenvironmental Regulation

Among the various immunological and non-immunological tumor-promoting activities of myeloid-derived suppressor cells (MDSCs), their immunosuppressive capacity remains a key hallmark. Effort in the past decade has provided us with a clearer view of the suppressive nature of MDSCs. More suppressive pathways have been identified, and their recognized targets have been expanded from T cells and natural killer (NK) cells to other immune cells. These novel mechanisms and targets afford MDSCs versatility in suppressing both innate and adaptive immunity. On the other hand, a better understanding of the regulation of their development and function has been unveiled. This intricate regulatory network, consisting of tumor cells, stromal cells, soluble mediators, and hostile physical conditions, reveals bi-directional crosstalk between MDSCs and the tumor microenvironment. In this article, we will review available information on how MDSCs exert their immunosuppressive function and how they are regulated in the tumor milieu. As MDSCs are a well-established obstacle to anti-tumor immunity, new insights in the potential synergistic combination of MDSC-targeted therapy and immunotherapy will be discussed.

Sildenafil might impair maternal-fetal immunotolerance by suppressing myeloid-derived suppressor cells in mice

Myeloid-derived suppressor cells (MDSCs) as an important population of immune cells were found to restrain T cell function, polarize T-helper cells (Th) 1/Th2 toward Th2 response and induce regulatory T cells (Tregs), therefore enhancing the immunotolerance during pregnancy. Sildenafil has been applied for poor endometrial quality in implantation failure patients. Nevertheless, investigations have shown that sildenafil could reduce MDSCs-dependent immunosuppression. Whether sildenafil affects embryo implantation by suppressing MDSCs? To address this question, using the mice model, we investigated the amounts of immune cells in peripheral blood and endometrial cells from control group (CG), sildenafil low-dose group (LDG) and high-dose group (HDG). We found that both treatment groups displayed a marked deficiency in polymorphonuclear (PMN)-MDSCs and Th2 from mice blood and endometrium as compared to these from CG. The frequency of Tregs in endometrium from HDG was lower than those from CG. Th1/Th2 ratio in both periphery and uterus from study groups showed a significant increase as compared to those from CG. By relevance analysis, we found that the level of Tregs positively correlated with the level of PMN-MDSCs, whereas the Th1/Th2 ratio negatively correlated with the frequency of PMN-MDSCs in uterus. Moreover, there was a positive relationship between the amount of blood PMN-MDSCs and endometrial PMN-MDSCs. These results suggest that we should carefully weigh the pros and cons of using sildenafil when applied to patients with poor endometrial receptivity.

Myeloid-derived suppressor cells in obstetrical and gynecological diseases

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of myeloid-origin cells which have immunosuppressive activities in several conditions, such as cancer and inflammation. Recent research has also associated MDSCs with numerous obstetrical and gynecological diseases. During pregnancy, MDSCs accumulate to ensure maternal-fetal immune tolerance, whereas they are decreased in patients who suffer from early miscarriage or pre-eclampsia. While the etiology of endometriosis is still unknown, abnormal accumulation of MDSCs in the peripheral blood and peritoneal fluid, alongside an increased level of reactive oxygen species (ROS), has been observed in these patients, which is central to the cellular immune regulations by MDSCs. Additionally, the regulation of MDSCs observed in tumours is also applicable to gynecologic neoplasms, including ovarian cancer and cervical cancer. More recently, emerging evidence has shown that there are high levels of MDSCs in premature ovarian failure (POF) and in vitro fertilization (IVF), but the underlying mechanisms are unknown. In this review, the generation and mechanisms of MDSCs are summarized. In particular, the modulation of these cells in immune-related obstetrical and gynecological diseases is discussed, including potential treatment options targeting MDSCs.

STAT3: Versatile Functions in Non-Small Cell Lung Cancer

Signal Transducer and Activator of Transcription 3 (STAT3) activation is frequently found in non-small cell lung cancer (NSCLC) patient samples/cell lines and STAT3 inhibition in NSCLC cell lines markedly impairs their survival. STAT3 also plays a pivotal role in driving tumor-promoting inflammation and evasion of anti-tumor immunity. Consequently, targeting STAT3 either directly or by inhibition of upstream regulators such as Interleukin-6 (IL-6) or Janus kinase 1/2 (JAK1/2) is considered as a promising treatment strategy for the management of NSCLC. In contrast, some studies also report STAT3 being a tumor suppressor in a variety of solid malignancies, including lung cancer. Here, we provide a concise overview of STAT3‘s versatile roles in NSCLC and discuss the yins and yangs of STAT3 targeting therapies.

Enhanced expression of CD39 and CD73 on T cells in the regulation of anti-tumor immune responses

Synthesis of extracellular adenosine by the ectonucleotidases CD39 and CD73 represents an important pathway of immune suppression in the tumor microenvironment. Using two mouse models (RET transgenic melanoma and Panc02 orthotopic pancreatic adenocarcinoma), we identified an elevated frequency of ectonucleotidase-expressing T cells in tumors and spleens. Importantly, these ectonucleotidase-positive T cells also showed a pronounced expression of PD-1. Conversely, the PD-1⁺ T cell subsets in tumors contained substantially larger proportions of ectonucleotidase-expressing cells compared to their counterparts lacking PD-1 expression. Our in vitro experiments showed that the activation of normal T cells resulted in an increase in the CD39 expression. CD39⁺ and CD73⁺ T cells displayed effector or memory phenotypes and produced IFN-γ, thereby linking ectonucleotidase expression to T cell effector functions. An accumulation of conventional and regulatory T cells expressing CD39 and/or CD73 was also detected in the peripheral blood of patients with melanoma and pancreatic cancer. Moreover, we demonstrated a significant association between low frequencies of circulating CD73⁺CD8⁺ T cells and CD73⁺CD4⁺ regulatory T cells and better overall survival of melanoma patients. Tumor-derived soluble factors (in particular, TGF-β) significantly enhanced the frequencies of ectonucleotidase-expressing cells in mice. Our findings suggest that the upregulation of ectonucleotidase expression in T cells promotes extracellular adenosine accumulation and represents an important mechanism of homeostatic immune auto-regulation, which could be hijacked by tumors to evade anti-cancer immunity. Targeting CD39 and CD73 can open new avenues for cancer immunotherapy.

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.

Pancreatic ductal adenocarcinoma: Treatment hurdles, tumor microenvironment and immunotherapy

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal diseases, with an average 5-year survival rate of less than 10%. Unfortunately, the majority of patients have unresectable, locally advanced, or metastatic disease at the time of diagnosis. Moreover, traditional treatments such as chemotherapy, surgery, and radiation have not been shown to significantly improve survival. Recently, there has been a swift increase in cancer treatments that incorporate immunotherapy-based strategies to target all the stepwise events required for tumor initiation and progression. The results in melanoma, non-small-cell lung cancer and renal cell carcinoma are very encouraging. Unfortunately, the application of checkpoint inhibitors, including anti-CTLA4, anti-PD-1, and anti-PD-L1 antibodies, in pancreatic cancer has been disappointing. Many studies have revealed that the PDAC microenvironment supports tumor growth, promotes metastasis and consists of a physical barrier to drug delivery. Combination therapies hold great promise for enhancing immune responses to achieve a better therapeutic effect. In this review, we provide an outline of why pancreatic cancer is so lethal and of the treatment hurdles that exist. Particular emphasis is given to the role of the tumor microenvironment, and some of the latest and most promising studies on immunotherapy in PDAC are also presented.