Pancreatic Ductal Adenocarcinoma: A Strong Imbalance of Good and Bad Immunological Cops in the Tumor Microenvironment

Curing pancreatic cancer

The distinct biology of pancreatic cancer with aggressive and early invasive tumor cells, a tumor promoting microenvironment, late diagnosis, and high therapy resistance poses major challenges on clinicians, researchers, and patients. In current clinical practice, a curative approach for pancreatic cancer can only be offered to a minority of patients and even for those patients, the long-term outcome is grim. This bitter combination will eventually let pancreatic cancer rise to the second leading cause of cancer-related mortalities. With surgery being the only curative option, complete tumor resection still remains the center of pancreatic cancer treatment. In recent years, new developments in neoadjuvant and adjuvant treatment have emerged. Together with improved perioperative care including complication management, an increasing number of patients have become eligible for tumor resection. Basic research aims to further increase these numbers by new methods of early detection, better tumor modelling and personalized treatment options. This review aims to summarize the current knowledge on clinical and biologic features, surgical and non-surgical treatment options, and the improved collaboration of clinicians and basic researchers in pancreatic cancer that will hopefully result in more successful ways of curing pancreatic cancer.

XGBoost Classifier Based on Computed Tomography Radiomics for Prediction of Tumor-Infiltrating CD8+ T-Cells in Patients With Pancreatic Ductal Adenocarcinoma

Objectives

This study constructed and validated a machine learning model to predict CD8⁺ tumor-infiltrating lymphocyte expression levels in patients with pancreatic ductal adenocarcinoma (PDAC) using computed tomography (CT) radiomic features.

Materials and Methods

In this retrospective study, 184 PDAC patients were randomly assigned to a training dataset (n =137) and validation dataset (n =47). All patients were divided into CD8⁺ T-high and -low groups using X-tile plots. A total of 1409 radiomics features were extracted from the segmentation of regions of interest, based on preoperative CT images of each patient. The LASSO algorithm was applied to reduce the dimensionality of the data and select features. The extreme gradient boosting classifier (XGBoost) was developed using a training set consisting of 137 consecutive patients admitted between January 2017 and December 2017. The model was validated in 47 consecutive patients admitted between January 2018 and April 2018. The performance of the XGBoost classifier was determined by its discriminative ability, calibration, and clinical usefulness.

Results

The cut-off value of the CD8⁺ T-cell level was 18.69%, as determined by the X-tile program. A Kaplan−Meier analysis indicated a correlation between higher CD8⁺ T-cell levels and better overall survival (p = 0.001). The XGBoost classifier showed good discrimination in the training set (area under curve [AUC], 0.75; 95% confidence interval [CI]: 0.67–0.83) and validation set (AUC, 0.67; 95% CI: 0.51–0.83). Moreover, it showed a good calibration. The sensitivity, specificity, accuracy, positive and negative predictive values were 80.65%, 60.00%, 0.69, 0.63, and 0.79, respectively, for the training set, and 80.95%, 57.69%, 0.68, 0.61, and 0.79, respectively, for the validation set.

Conclusions

We developed a CT-based XGBoost classifier to extrapolate the infiltration levels of CD8⁺ T-cells in patients with PDAC. This method could be useful in identifying potential patients who can benefit from immunotherapies.

CDK1/2/5 inhibition overcomes IFNG-mediated adaptive immune resistance in pancreatic cancer

OBJECTIVE

Adaptive immune resistance mediated by the cytokine interferon gamma (IFNG) still constitutes a major problem in cancer immunotherapy. We develop strategies for overcoming IFNG-mediated adaptive immune resistance in pancreatic ductal adenocarcinoma cancer (PDAC).

DESIGN

We screened 429 kinase inhibitors for blocking IFNG-induced immune checkpoint (indoleamine 2,3-dioxygenase 1 (IDO1) and CD274) expression in a human PDAC cell line. We evaluated the ability of the cyclin-dependent kinase (CDK) inhibitor dinaciclib to block IFNG-induced IDO1 and CD274 expression in 24 human and mouse cancer cell lines as well as in primary cancer cells from patients with PDAC or ovarian carcinoma. We tested the effects of dinaciclib on IFNG-induced signal transducer and activator of transcription 1 activation and immunological cell death, and investigated the potential utility of dinaciclib in combination with IFNG for pancreatic cancer therapy in vivo, and compared gene expression levels between human cancer tissues with patient survival times using the Cancer Genome Atlas datasets.

RESULTS

Pharmacological (using dinaciclib) or genetic (using shRNA or siRNA) inactivation of CDK1/2/5 not only blocks JUN-dependent immune checkpoint expression, but also triggers histone-dependent immunogenic cell death in immortalised or primary cancer cells in response to IFNG. This dual mechanism turns an immunologically 'cold' tumour microenvironment into a 'hot' one, dramatically improving overall survival rates in mouse pancreatic tumour models (subcutaneous, orthotopic and transgenic models). The abnormal expression of CDK1/2/5 and IDO1 was associated with poor patient survival in several cancer types, including PDAC.

CONCLUSION

CDK1/2/5 kinase activity is essential for IFNG-mediated cancer immunoevasion. CDK1/2/5 inhibition by dinaciclib provides a novel strategy to overcome IFNG-triggered acquired resistance in pancreatic tumour immunity.

Desmoplastic Crosstalk in Pancreatic Ductal Adenocarcinoma Is Reflected by Different Responses of Panc-1, MIAPaCa-2, PaTu-8902, and CAPAN-2 Cell Lines to Cancer-associated/Normal Fibroblasts

BACKGROUND/AIM

Pancreatic ductal adenocarcinoma (PDAC) still represents one of the most aggressive cancers. Understanding of the epithelial-mesenchymal crosstalk as a crucial part of the tumor microenvironment should pave the way for therapies to improve patient survival rates. Well-established cell lines present a useful and reproducible model to study PDAC biology. However, the tumor-stromal interactions between cancer cells and cancer-associated fibroblasts (CAFs) are still poorly understood.

MATERIALS AND METHODS

We studied interactions between four PDAC cell lines (Panc-1, CAPAN-2, MIAPaCa-2, and PaTu-8902) and conditioned media derived from primary cultures of normal fibroblasts/PDAC-derived CAFs (PANFs).

RESULTS

When the tested PDAC cell lines were stimulated by PANF-derived conditioned media, the most aggressive behavior was acquired by the Panc-1 cell line (increased number and size of colonies, remaining expression of vimentin and keratin 8 as well as increase of epithelial-to-mesenchymal polarization markers), whereas PaTu-8902 cells were rather inhibited. Of note, administration of the conditioned media to MIAPaCa-2 cells resulted in an inverse effect on the size and number of colonies, whereas CAPAN-2 cells were rather stimulated. To explain the heterogeneous pattern of the observed PDAC crosstalk at the in vitro level, we further compared the phenotype of primary cultures of cells derived from ascitic fluid with that of the tested PDAC cell lines, analyzed tumor samples of PDAC patients, and performed gene expression profiling of PANFs. Immuno-cyto/histo-chemical analysis found specific phenotype differences within the group of examined patients and tested PDAC cell lines, whereas the genomic approach in PANFs found the key molecules (IL6, IL8, MFGE8 and periostin) that may contribute to the cancer aggressive behavior.

CONCLUSION

The desmoplastic patient-specific regulation of cancer cells by CAFs (also demonstrated by the heterogeneous response of PDAC cell lines to fibroblasts) precludes simple targeting and development of an effective treatment strategy and rather requires establishment of an individualized tumor-specific treatment protocol.

A 4-gene-based hypoxia signature is associated with tumor immune microenvironment and predicts the prognosis of pancreatic cancer patients

Background

Pancreatic cancer (PAC) is one of the most devastating cancer types with an extremely poor prognosis, characterized by a hypoxic microenvironment and resistance to most therapeutic drugs. Hypoxia has been found to be one of the factors contributing to chemoresistance in PAC, but also a major driver of the formation of the tumor immunosuppressive microenvironment. However, the method to identify the degree of hypoxia in the tumor microenvironment (TME) is incompletely understood.

Methods

The mRNA expression profiles and corresponding clinicopathological information of PAC patients were downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database, respectively. To further explore the effect of hypoxia on the prognosis of patients with PAC as well as the tumor immune microenvironment, we established a hypoxia risk model and divided it into high- and low-risk groups in line with the hypoxia risk score.

Results

We established a hypoxia risk model according to four hypoxia-related genes, which could be used to demonstrate the immune microenvironment in PAC and predict prognosis. Moreover, the hypoxia risk score can act as an independent prognostic factor in PAC, and a higher hypoxia risk score was correlated with poorer prognosis in patients as well as the immunosuppressive microenvironment of the tumor.

Conclusions

In summary, we established and validated a hypoxia risk model that can be considered as an independent prognostic indicator and reflected the immune microenvironment of PAC, suggesting the feasibility of hypoxia-targeted therapy for PAC patients.

Fam83D promotes tumorigenesis and gemcitabine resistance of pancreatic adenocarcinoma through the Wnt/β-catenin pathway

BACKGROUND

Elevated expression of family with sequence similarity 83 member D (Fam83D) has been found in various cancers; however, its role in pancreatic adenocarcinoma (PDAC) remains unclear. The current study was designed to elucidate the roles of Fam83D in pancreatic cancer.

METHOD

The level of Fam83D was detected in PDAC tissues and adjacent no-tumorous tissues. Effects of Fam83D on proliferation, glycolysis and gemcitabine (GEM) sensitivity of pancreatic cancer cells were examined.

RESULTS

Fam83D was overexpressed in PDAC and associated with clinical stage, metastatic status and survival rates of PDAC patients. Function study showed that Fam83D knockdown (KD) caused inhibited proliferation, suppressed mitochondrial respiration capacity, reduced aerobic glycolysis, and down-regulation of nuclear β-catenin, proto-oncogene C-Myc, and lactate dehydrogenase A (LDHA). Fam83D KD enhanced the sensitivity of PDAC cells to GEM in vitro and in vivo. On the contrary, Fam83D overexpression displayed reverse effects on PDAC cells. Moreover, the Wnt/β-catenin inhibitor abolished the effects of Fam83D overexpression in PDAC cells.

CONCLUSIONS

the current data suggest that enhanced Fam83D expression contributes to PDAC progression and the development of chemoresistance through the Wnt/β-catenin signaling.

The State-of-the-Art of Phase II/III Clinical Trials for Targeted Pancreatic Cancer Therapies

Pancreatic cancer is a devastating disease with very poor prognosis. Currently, surgery followed by adjuvant chemotherapy represents the only curative option which, unfortunately, is only available for a small group of patients. The majority of pancreatic cancer cases are diagnosed at advanced or metastatic stage when surgical resection is not possible and treatment options are limited. Thus, novel and more effective therapeutic strategies are urgently needed. Molecular profiling together with targeted therapies against key hallmarks of pancreatic cancer appear as a promising approach that could overcome the limitations of conventional chemo- and radio-therapy. In this review, we focus on the latest personalised and multimodal targeted therapies currently undergoing phase II or III clinical trials. We discuss the most promising findings of agents targeting surface receptors, angiogenesis, DNA damage and cell cycle arrest, key signalling pathways, immunotherapies, and the tumour microenvironment.

Dilemma and Challenge of Immunotherapy for Pancreatic Cancer

Pancreatic cancer is a tumor with a high degree of malignancy, morbidity, and mortality. Immunotherapy is another important treatment for pancreatic cancer in addition to surgery and chemotherapy, but its application in pancreatic cancer is very limited, which is related to the unique biological behavior of pancreatic cancer and the tumor microenvironment. The immunosuppressive microenvironment of pancreatic cancer is highly heterogeneous and presents challenges for immunotherapy. The transformation of tumor immunosuppressive microenvironment contributes to the response to tumor immunotherapy, such that the tumor undergoes functional reprogramming to change from immunologically "cold" to immunologically "hot." In this review, we summarized the research and progress in immunotherapy for pancreatic cancer, including immune checkpoint inhibitors, vaccines, adoptive T cell therapy, oncolytic viruses, and immunomodulators, and suggest that individualized, combination, and precise therapy should be the main direction of future immunotherapy in pancreatic cancer.

Tumor-Associated Macrophages in Pancreatic Ductal Adenocarcinoma: Origin, Polarization, Function, and Reprogramming

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy. PDAC is only cured by surgical resection in its early stage, but there remains a relatively high possibility of recurrence. The development of PDAC is closely associated with the tumor microenvironment. Tumor-associated macrophages (TAMs) are one of the most abundant immune cell populations in the pancreatic tumor stroma. TAMs are inclined to M2 deviation in the tumor microenvironment, which promotes and supports tumor behaviors, including tumorigenesis, immune escape, metastasis, and chemotherapeutic resistance. Herein, we comprehensively reviewed the latest researches on the origin, polarization, functions, and reprogramming of TAMs in PDAC.

Relevance of Immune Infiltration and Clinical Outcomes in Pancreatic Ductal Adenocarcinoma Subtypes

Purpose

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer with high heterogeneity and dismal survival rates. Tumor immune microenvironment plays a critical role in sensitive to chemotherapy and prognosis. Herein, we determined the relevance of the composition of tumor-infiltrating immune cells to clinical outcomes in PDACs, and we evaluated these effects by molecular subtype.

Experimental Design

Data of 1,274 samples from publically available datasets were collected. Molecular subtypes were predicted with support vector machine. Twenty-two subsets of immune cells were estimated with CIBERSORTx. The associations between each cell subset and overall survival (OS), relapse free survival (RFS), and complete response (CR) to chemotherapy were evaluated, modelling cellular proportions as quartiles.

Results

An immune-related cluster was identified with unsupervised hierarchical clustering of hallmark pathways. Of the immune cells investigated, M0 macrophages emerged as closely associated with worse OS (HR =1.23, 95% CI = 1.15–1.31, p=1.57×10^-9) and RFS (HR = 1.14, 95% CI =1.04–1.25, p=2.93×10^-3), regardless of molecular subtypes. The CD8+ T cells conferred favorable survival. The neutrophils conferred poor OS overall (HR=1.17, 95% CI=1.10–1.23, p=1.74×10^-7) and within the classical subtype. In the basal-like subtype, activated mast cells were associated with worse OS. Consensus clustering revealed six immune subgroups with distinct survival patterns and CR rates. The higher expression of PD1 was associated with better OS.

Conclusions

The immune cellular composition infiltrate in PDAC are likely to have effects on prognosis. Further exploration of the cellular immune response has the potential to identify candidates for immunotherapy.

Emerging roles for the IL-6 family of cytokines in pancreatic cancer

Pancreatic cancer has one of the poorest prognoses of all malignancies, with little improvement in clinical outcome over the past 40 years. Pancreatic ductal adenocarcinoma is responsible for the vast majority of pancreatic cancer cases, and is characterised by the presence of a dense stroma that impacts therapeutic efficacy and drives pro-tumorigenic programs. More specifically, the inflammatory nature of the tumour microenvironment is thought to underlie the loss of anti-tumour immunity and development of resistance to current treatments. Inflammatory pathways are largely mediated by the expression of, and signalling through, cytokines, chemokines, and other cellular messengers. In recent years, there has been much attention focused on dual targeting of cancer cells and the tumour microenvironment. Here we review our current understanding of the role of IL-6, and the broader IL-6 cytokine family, in pancreatic cancer, including their contribution to pancreatic inflammation and various roles in pancreatic cancer pathogenesis. We also summarise potential opportunities for therapeutic targeting of these pathways as an avenue towards combating poor patient outcomes.

Molecular and Metabolic Subtypes Correspondence for Pancreatic Ductal Adenocarcinoma Classification

Pancreatic ductal adenocarcinoma (PDAC), the most common form of pancreatic cancer, is an extremely lethal disease due to late diagnosis, aggressiveness and lack of effective therapies. Considering its intrinsic heterogeneity, patient stratification models based on transcriptomic and genomic signatures, with partially overlapping subgroups, have been established. Besides molecular alterations, PDAC tumours show a strong desmoplastic response, resulting in profound metabolic reprogramming involving increased glucose and amino acid consumption, as well as lipid scavenging and biosynthesis. Interestingly, recent works have also revealed the existence of metabolic subtypes with differential prognosis within PDAC, which correlated to defined molecular subclasses in patients: lipogenic subtype correlated with a classical/progenitor signature, while glycolytic tumours associated with the highly aggressive basal/squamous profile. Bioinformatic analyses have demonstrated that the representative genes of each metabolic subtype are up-regulated in PDAC samples and predict patient survival. This suggests a relationship between the genetic signature, metabolic profile, and aggressiveness of the tumour. Considering all this, defining metabolic subtypes represents a clear opportunity for patient stratification considering tumour functional behaviour independently of their mutational background.

Transcriptome Reprogramming of CD11b+ Bone Marrow Cells by Pancreatic Cancer Extracellular Vesicles

Pancreatic cancers (PC) are highly metastatic with poor prognosis, mainly due to delayed detection. We previously showed that PC-derived extracellular vesicles (EVs) act on macrophages residing in the liver, eliciting extracellular matrix remodeling in this organ and marked hepatic accumulation of CD11b+ bone marrow (BM) cells, which support PC liver metastasis. We here show that PC-EVs also bind to CD11b+ BM cells and induce the expansion of this cell population. Transcriptomic characterization of these cells shows that PC-EVs upregulate IgG and IgA genes, which have been linked to the presence of monocytes/macrophages in tumor microenvironments. We also report here the transcriptional downregulation of genes linked to monocyte/macrophage activation, trafficking, and expression of inflammatory molecules. Together, these results show for the first time the existence of a PC-BM communication axis mediated by EVs with a potential role in PC tumor microenvironments.

Vestigial-like 1 is a shared targetable cancer-placenta antigen expressed by pancreatic and basal-like breast cancers

Cytotoxic T lymphocyte (CTL)-based cancer immunotherapies have shown great promise for inducing clinical regressions by targeting tumor-associated antigens (TAA). To expand the TAA landscape of pancreatic ductal adenocarcinoma (PDAC), we performed tandem mass spectrometry analysis of HLA class I-bound peptides from 35 PDAC patient tumors. This identified a shared HLA-A*0101 restricted peptide derived from co-transcriptional activator Vestigial-like 1 (VGLL1) as a putative TAA demonstrating overexpression in multiple tumor types and low or absent expression in essential normal tissues. Here we show that VGLL1-specific CTLs expanded from the blood of a PDAC patient could recognize and kill in an antigen-specific manner a majority of HLA-A*0101 allogeneic tumor cell lines derived not only from PDAC, but also bladder, ovarian, gastric, lung, and basal-like breast cancers. Gene expression profiling reveals VGLL1 as a member of a unique group of cancer-placenta antigens (CPA) that may constitute immunotherapeutic targets for patients with multiple cancer types.

Pancreatic Adenocarcinoma Invasiveness and the Tumor Microenvironment: From Biology to Clinical Trials

Pancreatic adenocarcinoma (PDAC) originates in the glandular compartment of the exocrine pancreas. Histologically, PDAC tumors are characterized by a parenchyma that is embedded in a particularly prominent stromal component or desmoplastic stroma. The unique characteristics of the desmoplastic stroma shape the microenvironment of PDAC and modulate the reciprocal interactions between cancer and stromal cells in ways that have profound effects in the pathophysiology and treatment of this disease. Here, we review some of the most recent findings regarding the regulation of PDAC cell invasion by the unique microenvironment of this tumor, and how new knowledge is being translated into novel therapeutic approaches.

Impact of anatomic site on antigen-presenting cells in cancer

Checkpoint blockade immunotherapy (CBT) can induce long-term clinical benefits in patients with advanced cancer; however, response rates to CBT vary by cancer type. Cancers of the skin, lung, and kidney are largely responsive to CBT, while cancers of the pancreas, ovary, breast, and metastatic lesions to the liver respond poorly. The impact of tissue-resident immune cells on antitumor immunity is an emerging area of investigation. Recent evidence indicates that antitumor immune responses and efficacy of CBT depend on the tissue site of the tumor lesion. As myeloid cells are predominantly tissue-resident and can shape tumor-reactive T cell responses, it is conceivable that tissue-specific differences in their function underlie the tissue-site-dependent variability in CBT responses. Understanding the roles of tissue-specific myeloid cells in antitumor immunity can open new avenues for treatment design. In this review, we discuss the roles of tissue-specific antigen-presenting cells (APCs) in governing antitumor immune responses, with a particular focus on the contributions of tissue-specific dendritic cells. Using the framework of the Cancer-Immunity Cycle, we examine the contributions of tissue-specific APC in CBT-sensitive and CBT-resistant carcinomas, highlight how these cells can be therapeutically modulated, and identify gaps in knowledge that remain to be addressed.

T-Cell Immunity in Pancreatic Cancer

Worldwide, approximately half a million people are diagnosed with pancreatic cancer every year, with mortality rates of more than 90%. T cells within pancreatic tumors are generally infrequent and incapable of eliciting antitumor immunity. Thus, pancreatic cancer is considered an "immunologically cold" tumor. However, recent studies clearly show that when T-cell immunity in pancreatic cancer is sufficiently induced, T cells become effective weapons. This fact suggests that to improve pancreatic cancer patients' clinical outcomes, we need to unveil the complex immune biology of this disease. In this review, we discuss the elements of tumor immunogenicity in the specific context of pancreatic malignancy.

Novel combination immunotherapy for pancreatic cancer: potent anti-tumor effects with CD40 agonist and interleukin-15 treatment

Objectives

With the poorest 5‐year survival of all cancers, improving treatment for pancreatic cancer is one of the biggest challenges in cancer research. We sought to explore the potential of combining both priming and activation of the immune system. To achieve this, we combined a CD40 agonist with interleukin‐15 and tested its potential in pancreatic cancer.

Methods

Response to this combination regimen was assessed in pancreatic ductal adenocarcinoma mouse models, and a thorough analysis of the tumor microenvironment was performed.

Results

We demonstrated profound reduction in tumor growth and increased survival of mice with the majority of mice being cured when both agents were combined, including an unprecedented 8‐fold dose reduction of CD40 agonist without losing any efficacy. RNAseq analysis showed involvement of natural killer (NK) cell‐ and T‐cell‐mediated anti‐tumor responses and the importance of antigen‐presenting cell pathways. This combination resulted in enhanced infiltration of tumors by both T cells and NK cells, as well as a striking increase in the ratio of CD8⁺ T cells over Tregs. We also observed a significant increase in numbers of dendritic cells (DCs) in tumor‐draining lymph nodes, particularly CD103⁺ DCs with cross‐presentation potential. A critical role for CD8⁺ T cells and involvement of NK cells in the anti‐tumor effect was highlighted. Importantly, strong immune memory was established, with an increase in memory CD8⁺ T cells only when both interleukin‐15 and the CD40 agonist were combined.

Conclusion

These novel preclinical data support initiation of a first‐in‐human clinical trial with this combination immunotherapy strategy in pancreatic cancer.

Crosstalk between Tumor and Stromal Cells in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains a lethal cancer. The poor prognosis calls for a more detailed understanding of disease biology in order to pave the way for the development of effective therapies. Typically, the pancreatic tumor is composed of a minority of malignant cells within an excessive tumor microenvironment (TME) consisting of extracellular matrix (ECM), fibroblasts, immune cells, and endothelial cells. Research conducted in recent years has particularly focused on cancer-associated fibroblasts (CAFs) which represent the most prominent cellular component of the desmoplastic stroma. Here, we review the complex crosstalk between CAFs, tumor cells, and other components of the TME, and illustrate how these interactions drive disease progression. We also discuss the emerging field of CAF heterogeneity, their tumor-supportive versus tumor-suppressive capacity, and the consequences for designing stroma-targeted therapies in the future.

Applied precision medicine in metastatic pancreatic ductal adenocarcinoma

BACKGROUND

Metastatic pancreatic ductal adenocarcinoma (mPDAC) bears a dismal prognosis due to the limited activity of systemic chemotherapy. In our platform for precision medicine, we aim to offer molecular-guided treatments to patients without further standard therapy options.

METHODS

In this single center, real-world retrospective analysis of our platform, we describe the molecular-based therapy approaches used in all 50 patients diagnosed with therapy-refractory mPDAC. A molecular portrait of the tumor specimens was created by next-generation sequencing, immunohistochemistry (IHC), microsatellite instability (MSI) testing, and fluorescence in situ hybridization.

RESULTS

In total, we detected 123 mutations in 50 patients. The five most frequent mutations were KRAS (n = 40; 80%), TP53 (n = 29; 58%), CDKN2A (n = 8; 16%), SMAD4 (n = 4; 8%), and NOTCH1 (n = 4; 8%), which together accounted for 40.2% of all mutations. Two patients had gene fusions, namely, TBL1XR1-PIK3CA and EIF3E-RSPO2. IHC detected expression of EGFR, phosphorylated mTOR, and PTEN in 36 (72%), 33 (66%), and 17 patients (34%), respectively. For 14 (28%) of the 50 patients, a targeted therapy was suggested based on the identified molecular targets. The recommended treatments included the mTOR inhibitor everolimus (n = 3), pembrolizumab (n = 3), palbociclib (n = 2), nintedanib (n = 2), and cetuximab, crizotinib, tamoxifen, and the combination of lapatinib and trastuzumab, in one patient each.Finally, five patients received the recommended therapy. Four patients died due to disease progression before radiological assessment. One patient was treated with nintedanib and achieved stable disease for 6 months.

CONCLUSION

Based on our observations, precision medicine approaches are feasible and implementable in clinical routine and may provide molecular-based therapy recommendations for mPDAC.

Current Clinical Evidence and Potential Solutions to Increase Benefit of CAR T-Cell Therapy for Patients with Solid Tumors

Immunotherapy by chimeric antigen receptor (CAR)-modified T-cells has shown unprecedented clinical efficacy for hematological malignancies. Recently two CAR T-cell based therapeutics, Kymriah (Tisagenlecleucel) and Yescarta (Axicabtagene ciloleucel) were approved by the US Food and Drug Administration and by the European Medicines Agency. Despite the progress in treating hematological malignancies, challenges remain for the use of CAR T-cell therapy in patients with solid tumors. Barriers yet to overcome for achieving effective CAR T-cell therapy include antigenic heterogeneity of solid tumors, an immune-suppressive microenvironment, and organ-specific properties that limit T-cell entry. This review will summarize available clinical data for CAR T-cell therapy in solid tumors, including present obstacles and promising strategies to advancement.

DCLK1-Isoform2 Alternative Splice Variant Promotes Pancreatic Tumor Immunosuppressive M2-Macrophage Polarization

Tumor-associated M2-macrophages are one of the most abundant immunosuppressive cell types in the pancreatic ductal adenocarcinoma (PDAC) tumor microenvironment (TME). However, the molecular mechanisms responsible for the generation of M2-macrophages are unclear. Here, we demonstrated that overexpression of DCLK1-isoform2 in AsPC1 and MIA PaCa2 cells resulted in the polarization of M1-macrophages toward an M2 phenotype via secreted chemokines/cytokines. These M2-macrophages enhanced parental PDAC cell migration, invasion, and self-renewal, and this was associated with increased expression of Snail and Slug. We observed distinct expression of Dclk-isoform2, marked infiltration of M2-macrophages, and a marginal increase of CD8⁺ T cells in 20-week-old KPCY mice pancreas compared with 5 weeks old. Utilizing an autochthonous mouse model of pancreatic adenocarcinoma, we observed distinct immunoreactive Dclk1 and arginase1 in tissues where CD8⁺ T-cell infiltration was low and observed a paucity of DCLK1 and arginase1 staining where CD8⁺ T-cell infiltration was high. Finally, we found that DCLK1-isoform2 tumor-educated M2-macrophages inhibit CD8⁺ T-cell proliferation and granzyme-B activation. Inhibition of DCLK1 in an organoid coculture system enhanced CD8⁺ T-cell activation and associated organoid death. We conclude that DCLK1-isoform2 is a novel initiator of alternate macrophage activation that contributes to the immunosuppression observed in the PDAC TME. These data suggest that tumor DCLK1-isoform2 may be an attractive target for PDAC therapy, either alone or in conjunction with immunotherapeutic strategies.

Pancreatic Cancer and Its Microenvironment-Recent Advances and Current Controversies

Pancreatic ductal adenocarcinoma (PDAC) causes annually well over 400,000 deaths world-wide and remains one of the major unresolved health problems. This exocrine pancreatic cancer originates from the mutated epithelial cells: acinar and ductal cells. However, the epithelia-derived cancer component forms only a relatively small fraction of the tumor mass. The majority of the tumor consists of acellular fibrous stroma and diverse populations of the non-neoplastic cancer-associated cells. Importantly, the tumor microenvironment is maintained by dynamic cell-cell and cell-matrix interactions. In this article, we aim to review the most common drivers of PDAC. Then we summarize the current knowledge on PDAC microenvironment, particularly in relation to pancreatic cancer therapy. The focus is placed on the acellular stroma as well as cell populations that inhabit the matrix. We also describe the altered metabolism of PDAC and characterize cellular signaling in this cancer.

Cav-1 Ablation in Pancreatic Stellate Cells Promotes Pancreatic Cancer Growth through Nrf2-Induced shh Signaling

A more comprehensive understanding of the complexity of pancreatic cancer pathobiology, especially, and understanding of the role of the tumor microenvironment (TME) in disease progression should pave the way for therapies to improve patient response rates. Previous studies reported that caveolin-1 (Cav-1) has both tumor-promoting and tumor-suppressive functions. However, the function of Cav-1 in the pancreatic cancer microenvironment remains largely unexplored. Here, we show that coinjection of Cav-1-silenced pancreatic stellate cells (PSCs) with pancreatic cancer cells increased tumor growth. To comprehensively characterize paracrine communication between pancreatic cancer cells and PSCs, PSCs were cultured with pancreatic cancer cell conditioned medium (CM) containing cytokines. We reveal that Cav-1-silenced PSCs facilitated the growth of pancreatic cancer cells via enhanced paracrine shh/MMP2/bFGF/IL-6 signaling. Specifically, Cav-1-silenced PSCs exhibited increased shh expression, which heterotypically activated the shh signaling pathway in pancreatic cancer cells. Moreover, Cav-1-deficient PSCs accumulated ROS to enhance the shh pathway and angiogenesis in pancreatic cancer cells. In addition, overexpression of Nrf2 reversed the effects of Cav-1 knockdown on PSCs, increasing ROS production and enhancing paracrine shh/MMP2/bFGF/IL-6 signaling. Together, our findings show that stromal Cav-1 may mediate different mechanisms in the complex interaction between cancer cells and their microenvironment though Nrf2-induced shh signaling activation during pancreatic cancer progression.

TGF-β1 secreted by pancreatic stellate cells promotes stemness and tumourigenicity in pancreatic cancer cells through L1CAM downregulation

Pancreatic stellate cells (PSCs) secrete high levels of transforming growth factor-β1 (TGF-β1) that contributes to the development of pancreatic ductal adenocarcinoma (PDAC). TGF-β1 modulates the expression of L1 cell adhesion molecule (L1CAM), but its role in tumour progression still remains controversial. To clarify L1 function in PDAC and cellular phenotypes, we performed L1CAM cell sorting, silencing and overexpression in several primary pancreatic cancer cells. PSCs silenced for TGF-β1 were used for crosstalk experiments. We found that TGF-β1 secreted by PSCs negatively regulates L1CAM expression, through canonical TGF-β-Smad2/3 signalling, leading to a more aggressive PDAC phenotype. Cells with reduced expression of L1CAM harboured enhanced stemness potential and tumourigenicity. Inactivation of TGF-β1 signalling in PSCs strongly reduced the aggressiveness of PDAC cells. Our data provide functional proof and mechanistic insights for the tumour-suppressive function of L1CAM via reducing stemness. Rescuing L1CAM expression in cancer cells through targeting of TGF-β1 reverses stemness and bears the potential to improve the still miserable prognosis of PDAC patients.

Patient-derived xenograft model engraftment predicts poor prognosis after surgery in patients with pancreatic cancer

OBJECTIVES

To establish and evaluate a first generation patient-derived xenograft (PDX) model in nude mice using tumors resected from pancreatic cancer (PC) patients for the identification of key factors that influence xenograft success and prediction of patient prognosis.

METHODS

Primary tumor samples harvested from PC patients who underwent curative resection between May 2016 and April 2018 at our hospital were xenografted into nude mice. Tumor size was evaluated for 2 months. Patients' baseline characteristics and follow-up data were analyzed.

RESULTS

Tumor xenograft models were generated from 67 patients; 30 (44.8%) were successful and 37 (55.2%) failed. Xenograft models could recapitulate the pathology and genetic information of the primary tumors. Univariate analysis identified tumor engraftment, post-operation CA19-9, tumor size, lymph node status, and lymphovascular invasion as significant predictors (P=0.000, 0.023, 0.004, 0.035 and 0.005, respectively) of disease-free survival (DFS). Multivariate Cox regression analysis confirmed tumor engraftment, tumor size and lymphovascular invasion function as independent risk factors for DFS (P=0.000, 0.039 and 0.025, respectively). The hazard ratio of tumor engraftment for DFS was 0.239 (95% confidence interval, 0.109 to 0.524). Kaplan-Meier analysis of DFS indicated an unfavorable outcome in the engraftment group compared to that in the failed engraftment group (6.2 vs. 12.2 months, log rank P=0.000).

CONCLUSION

The pathology and genetic information of primary PC tumors are recapitulated in the PDX tumor model in nude mice. Furthermore, engraftment success is an effective predictor of disease recurrence in patients after surgery.

Quantitative, qualitative and spatial analysis of lymphocyte infiltration in periampullary and pancreatic adenocarcinoma

Immunotherapeutic modalities are currently revolutionizing cancer treatment. In pancreatic cancer, however, early clinical trials have been disappointing. The optimization of immunotherapeutic strategies requires better understanding of the inflammatory tumor microenvironment. Therefore, the aim of our study was to perform a detailed in situ description of lymphocyte infiltration patterns in resected pancreatic and other periampullary cancers. Multiplexed immunofluorescence imaging was applied to tissue microarrays with tumors from a cohort of 175 patients with resected periampullary adenocarcinoma. A panel of immune cell markers including CD4, CD8α, FoxP3, CD20, CD45RO and pan-cytokeratin was applied to allow for simultaneous spatial analysis of multiple lymphocyte populations. The majority of lymphocyte populations were significantly more abundant in intestinal (I-type) compared to pancreatobiliary (PB-type) tumors. Hierarchical cluster analysis revealed several immune cell signatures of potential clinical relevance. Notably, in the stromal compartment of PB-type tumors, high infiltration of B cells, CD8α⁺ CD45RO⁺ and single-positive CD4⁺ T cells, but low levels of FoxP3⁺ CD45RO^high and single-positive CD8α⁺ T cells were associated with improved overall survival (OS). The study also defined prognostic relevant topographical patterns of lymphocytic infiltration, in particular proximity of CD8α⁺ cells to cancer cells. Moreover, the presence of lymphocytes with potential T-helper capacities (CD4⁺ ) in the nearest vicinity to CD8α⁺ cells was associated with a prolonged OS. Our data demonstrate that the composition and clinical impact of immune infiltrates in periampullary adenocarcinoma differ by morphological type as well as localization. Furthermore, spatial in situ analysis identified potential immunological mechanisms of prognostic significance.

Patient outcome according to the 2017 international consensus on the definition of borderline resectable pancreatic ductal adenocarcinoma

BACKGROUND/OBJECTIVE

We evaluated the usefulness of the 2017 definition of borderline pancreatic ductal adenocarcinoma (BR-PDAC) in fit patients (performance status 0-1) based on anatomical (A) and biological dimensions (B).

METHODS

From 2011 to 2018, 139 resected patients with BR-PDAC according to the 2017 definition were included: 18 patients underwent upfront pancreatectomy (CA 19-9 > 500 U/mL and/or regional lymph node metastasis; BR-B group), and 121 received FOLFIRINOX (FX) induction chemotherapy and were divided into BR-A (CA 19-9 < 500 U/mL, no regional lymph node metastasis; n = 68) and BR-AB (CA 19-9 > 500 U/mL and/or regional lymph node metastasis; n = 53) groups.

RESULTS

The 3 groups were comparable according to patient characteristics (except for back pain (P < .01) and CA 19-9 (P < .01)), intraoperative data, and postoperative courses. BR-AB patients required more venous resections (P < .01). The 3 groups were comparable on pathologic findings, except that BR-B patients had more lymph node invasions (P = .02). Median overall survival (OS) of the 121 patients was 45 months. In multivariate analysis, venous resection (P = .039) and R1 resection (P = .012) were poorly linked with OS, whereas BR-A classification (P < .01) independently favored OS. Median survival times of BR-A, BR-AB, and BR-B groups were undetermined, 27 months, and 20 months (P < .001), respectively.

CONCLUSIONS

The 2017 definition was relevant for sub-classifying patients with BR-PDAC. The anatomical dimension (BR-A) was a favorable prognostic factor, whereas the biological dimension (BR-AB and BR-B) poorly impacted survival.

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.

CNN-based survival model for pancreatic ductal adenocarcinoma in medical imaging

Background

Cox proportional hazard model (CPH) is commonly used in clinical research for survival analysis. In quantitative medical imaging (radiomics) studies, CPH plays an important role in feature reduction and modeling. However, the underlying linear assumption of CPH model limits the prognostic performance. In this work, using transfer learning, a convolutional neural network (CNN) based survival model was built and tested on preoperative CT images of resectable Pancreatic Ductal Adenocarcinoma (PDAC) patients.

Results

The proposed CNN-based survival model outperformed the traditional CPH-based radiomics approach in terms of concordance index and index of prediction accuracy, providing a better fit for patients’ survival patterns.

Conclusions

The proposed CNN-based survival model outperforms CPH-based radiomics pipeline in PDAC prognosis. This approach offers a better fit for survival patterns based on CT images and overcomes the limitations of conventional survival models.

Assessing the Magnitude of Immunogenic Cell Death Following Chemotherapy and Irradiation Reveals a New Strategy to Treat Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) continues to have a dismal prognosis, in part, due to ineffective treatment strategies. The efficacy of some chemotherapies and especially radiotherapy is mediated partially by the immune system. Therefore, we hypothesized that profiling the immune response following chemotherapy and/or irradiation can be used as a readout for treatment efficacy but also to help identify optimal therapeutic schedules for PDAC. Using murine models of PDAC, we demonstrated that concurrent administration of stereotactic body radiotherapy (SBRT) and a modified dose of FOLFIRINOX (mFX) resulted in superior tumor control when compared with single or sequential treatment groups. Importantly, this combined treatment schedule enhanced the magnitude of immunogenic cell death, which in turn amplified tumor antigen presentation by dendritic cells and intratumoral CD8+ T-cell infiltration. Concurrent therapy also resulted in systemic immunity contributing to the control of established metastases. These findings provide a rationale for pursuing concurrent treatment schedules of SBRT with mFX in PDAC.

Prognostic value of pre-treatment peripheral blood markers in pancreatic ductal adenocarcinoma and their association with S100A4 expression in tumor tissue

The aims of the present study were to clarify the prognostic value of peripheral blood variables in patients with pancreatic ductal adenocarcinoma (PDAC), including the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR) and lymphocyte-to-monocyte ratio (LMR), and to determine the association between these variables and S100 calcium-binding protein A4 (S100A4) expression in tumor tissue, which is another prognostic factor for PDAC. Patients with PDAC were recruited at the Tianjin Medical University Cancer Institute and Hospital (Tianjin, China) between December 2008 and December 2014. A retrospective analysis was performed based on the recorded pre-treatment hematological parameters and clinical data. The prognostic value of NLR, PLR and LMR was examined. The association between these variables and S100A4 tissue expression was analyzed. Descriptive statistics and χ2 analyses were used in the present study. The median overall survival (OS) time of patients with PDAC was 9 months (range, 1-32 months). Univariate analysis revealed that NLR, LMR, carbohydrate antigen 19-9, surgery, chemotherapy, stage at diagnosis, tumor grade and age significantly affected OS. Although PLR exhibited no significant effects on OS, NLR and LMR were independent prognostic factors according to the multivariate analysis. Unpaired Student's t-test revealed differences between S100A4 expression and NLR, PLR and LMR. The results of the present study indicated that low NLR and high LMR were associated with a favorable prognosis in patients with PDAC. As a simply obtained and widely available index at diagnosis, NLR and LMR may become a novel predictive and classifying marker for PDAC in the clinical setting.

A Systematic Inflammation-based Model in Advanced Pancreatic Ductal Adenocarcinoma

Emerging evidence revealed the critical role of systematic inflammation in pancreatic ductal adenocarcinoma (PDAC). In the present study, we reviewed the records of 279 patients with advanced PDAC. Among them, 147 cases were used as the training cohort and another 132 as the validation cohort. In the training cohort, distant metastasis, carbohydrate antigen 19-9 (CA19-9), Glasgow prognostic score (GPS), neutrophil-to-lymphocyte ratio (NLR), and lymphocyte-to-monocyte ratio (LMR) were independent prognostic factors in Cox regression. A nomogram based on these factors was generated to predict median survival time and survival probabilities at 6, 12, and 18 months. The nomogram showed a better discriminatory ability than the American Joint Committee on Cancer (AJCC) TNM staging (C-index: 0.727 vs. 0.610). In the validation cohort, a nomogram composed of the same variables also showed a high discriminatory ability (C-index: 0.784). In the low-risk group with a nomogram total point (NTP) value of more than 175, patients receiving combination therapy showed better prognosis than those receiving monotherapy (P=0.015). In conclusion, the nomogram based on inflammatory biomarkers can serve as useful prognostic tool for advanced PDAC. In addition, patients with high NTP can greater benefit from combination chemotherapy than monotherapy.

Characterization of spatial distribution of tumor-infiltrating CD8+ T cells refines their prognostic utility for pancreatic cancer survival

The abundance of cytotoxic T-cell infiltrates has important implications for patient outcome and therapeutic design for pancreatic ductal adenocarcinoma. However, intratumoral heterogeneity remains a challenge to understanding the complex immune microenvironment. We hypothesized that characterizing CD8⁺ cell distribution within pancreatic adenocarcinoma tissues might refine the prognostic value of tumor-infiltrating CD8⁺ lymphocytes. Using multiplex immunohistochemistry-based image analysis on whole-tissue sections of 214 pancreatic ductal adenocarcinomas, we measured CD8⁺ cell densities in the tumor center, the tumor margin, and the whole tumor, along with the proximity of CD8⁺ cells to carcinoma cells. Multivariable Cox regression analysis was performed to assess the associations of CD8⁺ cell densities with pancreatic cancer-specific survival, adjusting for clinicopathologic and immune-related features, including tumor expressions of TP53, SMAD4, and the programmed cell death 1 ligand 1 (CD274, PD-L1) and the extent of tertiary lymphoid structures. There was substantial heterogeneity in CD8⁺ cell density, with the mean density in the tumor center less than half that in the tumor margin. Tumor CD274 expression and extensive tertiary lymphoid structures were appeared to be associated with higher CD8⁺ cell density in the tumor margin (P = 0.037 and P = 0.005, respectively), but not with that in the tumor center (P > 0.50). The association of higher CD8⁺ cell density with prolonged survival was significant for the whole tumor (P_trend = 0.009); however, the association was stronger for the tumor center (P_trend = 0.002) and insignificant for the tumor margin (P_trend = 0.07). Tumor cell-CD8⁺ cell distance correlated strongly with CD8⁺ cell density, whereas the density of CD8⁺ cells proximate to cancer cells exhibited no prognostic association. In conclusion, spatial computational analysis on pancreatic ductal adenocarcinoma reveals the prognostic validity of CD8⁺ cell density in the tumor center, where CD8⁺ cell infiltration is ununiformly restricted, likely suggesting pro-tumorigenic roles of the immunosuppressive tumor microenvironment of pancreatic cancer.

A Phase Ib Study of the Combination of Personalized Autologous Dendritic Cell Vaccine, Aspirin, and Standard of Care Adjuvant Chemotherapy Followed by Nivolumab for Resected Pancreatic Adenocarcinoma-A Proof of Antigen Discovery Feasibility in Three Patients

Despite the promising therapeutic effects of immune checkpoint blockade (ICB), most patients with solid tumors treated with anti-PD-1/PD-L1 monotherapy do not achieve objective responses, with most tumor regressions being partial rather than complete. It is hypothesized that the absence of pre-existing antitumor immunity and/or the presence of additional tumor immune suppressive factors at the tumor microenvironment are responsible for such therapeutic failures. It is therefore clear that in order to fully exploit the potential of PD-1 blockade therapy, antitumor immune response should be amplified, while tumor immune suppression should be further attenuated. Cancer vaccines may prime patients for treatments with ICB by inducing effective anti-tumor immunity, especially in patients lacking tumor-infiltrating T-cells. These "non-inflamed" non-permissive tumors that are resistant to ICB could be rendered sensitive and transformed into "inflamed" tumor by vaccination. In this article we describe a clinical study where we use pancreatic cancer as a model, and we hypothesize that effective vaccination in pancreatic cancer patients, along with interventions that can reprogram important immunosuppressive factors in the tumor microenvironment, can enhance tumor immune recognition, thus enhancing response to PD-1/PD-L1 blockade. We incorporate into the schedule of standard of care (SOC) chemotherapy adjuvant setting a vaccine platform comprised of autologous dendritic cells loaded with personalized neoantigen peptides (PEP-DC) identified through our own proteo-genomics antigen discovery pipeline. Furthermore, we add nivolumab, an antibody against PD-1, to boost and maintain the vaccine's effect. We also demonstrate the feasibility of identifying personalized neoantigens in three pancreatic ductal adenocarcinoma (PDAC) patients, and we describe their optimal incorporation into long peptides for manufacturing into vaccine products. We finally discuss the advantages as well as the scientific and logistic challenges of such an exploratory vaccine clinical trial, and we highlight its novelty.

Tumor-specific delivery of gemcitabine with activatable liposomes

Gemcitabine delivery to pancreatic ductal adenocarcinoma is limited by poor pharmacokinetics, dense fibrosis and hypo-vascularization. Activatable liposomes, with drug release resulting from local heating, enhance serum stability and circulation, and the released drug retains the ability to diffuse within the tumor. A limitation of liposomal gemcitabine has been the low loading efficiency. To address this limitation, we used the superior solubilizing potential of copper (II) gluconate to form a complex with gemcitabine at copper:gemcitabine (1:4). Thermosensitive liposomes composed of DPPC:DSPC:DSPE-PEG2k (80:15:5, mole%) then reached 12 wt% loading, 4-fold greater than previously reported values. Cryo transmission electron microscopy confirmed the presence of a liquid crystalline gemcitabine‑copper mixture. The optimized gemcitabine liposomes released 60% and 80% of the gemcitabine within 1 and 5 min, respectively, at 42 °C. Liposomal encapsulation resulted in a circulation half-life of ~2 h in vivo (compared to reported circulation of 16 min for free gemcitabine in mice), and free drug was not detected within the plasma. The resulting gemcitabine liposomes were efficacious against both murine breast cancer and pancreatic cancer in vitro. Three repeated treatments of activatable gemcitabine liposomes plus ultrasound hyperthermia regressed or eliminated tumors in the neu deletion model of murine breast cancer with limited toxicity, enhancing survival when compared to treatment with gemcitabine alone. With 5% of the free gemcitabine dose (5 rather than 100 mg/kg), tumor growth was suppressed to the same degree as gemcitabine. Additionally, in a more aggressive tumor model of murine pancreatic cancer, liposomal gemcitabine combined with local hyperthermia induced cell death and regions of apoptosis and necrosis.

Protein tyrosine phosphatases: promising targets in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer. It is the fourth leading cause of cancer-related death and is associated with a very poor prognosis. KRAS driver mutations occur in approximately 95% of PDAC cases and cause the activation of several signaling pathways such as mitogen-activated protein kinase (MAPK) pathways. Regulation of these signaling pathways is orchestrated by feedback loops mediated by the balance between protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs), leading to activation or inhibition of its downstream targets. The human PTPome comprises 125 members, and these proteins are classified into three distinct families according to their structure. Since PTP activity description, it has become clear that they have both inhibitory and stimulatory effects on cancer-associated signaling processes and that deregulation of PTP function is closely associated with tumorigenesis. Several PTPs have displayed either tumor suppressor or oncogenic characteristics during the development and progression of PDAC. In this sense, PTPs have been presented as promising candidates for the treatment of human pancreatic cancer, and many PTP inhibitors have been developed since these proteins were first associated with cancer. Nevertheless, some challenges persist regarding the development of effective and safe methods to target these molecules and deliver these drugs. In this review, we discuss the role of PTPs in tumorigenesis as tumor suppressor and oncogenic proteins. We have focused on the differential expression of these proteins in PDAC, as well as their clinical implications and possible targeting for pharmacological inhibition in cancer therapy.

Why is pancreatic cancer so deadly? The pathologist's view

The remarkable aggressiveness of pancreatic cancer has never been fully explained. Although clearly multifactorial, we postulate that venous invasion, a finding seen in most pancreatic cancers but not in most cancers of other organs, may be a significant, underappreciated contributor to the aggressiveness of this disease. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Therapeutic challenges and current immunomodulatory strategies in targeting the immunosuppressive pancreatic tumor microenvironment

BACKGROUND

Pancreatic cancer is one of the most lethal type of cancers, with an overall five-year survival rate of less than 5%. It is usually diagnosed at an advanced stage with limited therapeutic options. To date, no effective treatment options have demonstrated long-term benefits in advanced pancreatic cancer patients. Compared with other cancers, pancreatic cancer exhibits remarkable resistance to conventional therapy and possesses a highly immunosuppressive tumor microenvironment (TME).

MAIN BODY

In this review, we summarized the evidence and unique properties of TME in pancreatic cancer that may contribute to its resistance towards immunotherapies as well as strategies to overcome those barriers. We reviewed the current strategies and future perspectives of combination therapies that (1) promote T cell priming through tumor associated antigen presentation; (2) inhibit tumor immunosuppressive environment; and (3) break-down the desmoplastic barrier which improves tumor infiltrating lymphocytes entry into the TME.

CONCLUSIONS

It is imperative for clinicians and scientists to understand tumor immunology, identify novel biomarkers, and optimize the position of immunotherapy in therapeutic sequence, in order to improve pancreatic cancer clinical trial outcomes. Our collaborative efforts in targeting pancreatic TME will be the mainstay of achieving better clinical prognosis among pancreatic cancer patients. Ultimately, pancreatic cancer will be a treatable medical condition instead of a death sentence for a patient.

Mouse-Derived Allografts: A Complementary Model to the KPC Mice on Researching Pancreatic Cancer In Vivo

Pancreatic ductal adenocarcinoma (PDAC) is one of the most malignant cancers and has an extremely undesirable prognosis because little is known about the initiation and progression mechanisms of pancreatic cancer. The lack of an appropriate research model may have hindered this process. Using LSL-Kras^G12D/+; Trp53^fl/+; Pdx1-Cre (KPC) mice and the tumor tissue fragment transplantation technique, we constructed the mouse-derived subcutaneous/orthotopic allograft tumor models (MDAs-ST/OT). H&E staining, Masson staining and immunohistochemical staining were adopted to describe the histopathology and biomarkers of the MDAs and the recruitment of immune cells. The intervention of gemcitabine was applied to measure the chemotherapeutic response of MDAs tumors. MDAs could mimic the pathological histology and the high proliferation characteristics of PDAC. Indeed, the fibrosis, epithelial-mesenchyme transition (EMT) and invasion/metastasis related markers of MDAs were similar to those observed in pancreatic cancer. Further, the recruitment of immune cells in PDAC was precisely simulated by MDAs. In addition, gemcitabine suppressed the tumor growth of MDAs-ST significantly. MDAs are an effective model for investigating the progression and treatment of pancreatic cancer.

Cellular Senescence, Represented by Expression of Caveolin-1, in Cancer-Associated Fibroblasts Promotes Tumor Invasion in Pancreatic Cancer

BACKGROUND

The role of senescence of cancer-associated fibroblasts (CAFs) in the development of cancer is controversial. In this study, we investigated whether cellular senescence of CAFs, represented by CAV1 expression, affects tumor progression in pancreatic cancers (PC).

METHODS

Because CAV1 plays a major role in cellular senescence, we used CAV1 expression to monitor cellular senescence. A total of 157 consecutive patients with PC who underwent curative resection were enrolled in the study. Patients were divided into two groups according to CAV1 expression in CAFs by immunohistochemistry. We investigated the relationship between the CAV1 expression in CAFs and the patients' clinicopathological characteristics, including survival. We also established ten CAFs cell lines using PC clinical samples and chose one of them to knock down CAV1 expression. Finally, we cultured a PC cell line (MIAPaCa-2) in CAF-conditioned medium (CM).

RESULTS

Regarding patients' clinicopathological characteristics, the serum levels of carbohydrate antigen 19-9 and the rate of advanced tumor stage (pT2, 3, and 4) were significantly higher in the high-CAV1 group. The high-CAV1 group had significantly worse outcomes in both overall and disease-free survival (p < 0.01). Additionally, in co-culture assays using CAFs-CM and MIAPaCa-2 cells, we found that knockdown of CAV1 in CAFs negatively affected the invasion of PC cells.

CONCLUSIONS

In PC, CAV1 expression in CAFs is associated with patients' poor prognosis and the downregulation of CAV1 in CAFs reduces the invasiveness of PC cells. Therefore, CAV1 of CAFs might be a new target for the treatment of PC.

Overexpressed histone acetyltransferase 1 regulates cancer immunity by increasing programmed death-ligand 1 expression in pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma is one of the leading causes of cancer-related death worldwide. Immune checkpoint blockade therapy, including anti-PD-1 and anti-PD-L1, is a new therapeutic strategy for cancer treatment but the monotherapy with PD-L1 inhibitors for pancreatic cancer is almost ineffective for pancreatic cancer. Thus, exploring the regulatory mechanism of PD-L1 in cancer cells, especially in pancreatic cancer cells, is one of the key strategies to improving cancer patient response to PD-L1 blockade therapy. Histone acetyltransferase 1(HAT1) is a classic type B histone acetyltransferase and the biological role of HAT1 in pancreatic cancer is unclear.

METHODS

The clinical relevance of HAT1 was examined by the GEPIA web tool, Western blotting and immunohistochemistry of pancreatic cancer tissue microarray slides. Tumor cell motility was investigated by MTS assay, colony formation assay and xenografts. The relationship between HAT1 and PD-L1 was examined by Western blot analysis, RT-qPCR and immunohistochemistry.

RESULTS

HAT1 was upregulated in PDAC and associated with poor prognosis in PDAC patients. The knockdown of HAT1 decreased the proliferation of pancreatic cancer cells in vivo and in vitro. Strikingly, we showed that HAT1 transcriptionally regulated PD-L1, and this process was mainly mediated by BRD4 in pancreatic cancer. The knockdown of HAT1 improved the efficacy of immune checkpoint blockade by decreasing the PD-L1.

CONCLUSIONS

The recognition of HAT1 in regulating tumor cell proliferation and cancer immunity indicated that HAT1 might be employed as a new diagnostic and prognostic marker and a predictive marker for pancreatic cancer therapy, especially in immune checkpoint blockade therapy. Targeting HAT1 highlights a novel therapeutic approach to overcome immune evasion by tumor cells.

Prognostic Impact of Tumor-Infiltrating Lymphocytes and Neutrophils on Survival of Patients with Upfront Resection of Pancreatic Cancer

In patients with pancreatic ductal adenocarcinoma (PDAC), the tumor microenvironment consists of cellular and stromal components that influence prognosis. Hence, tumor-infiltrating lymphocytes (TILs) may predict prognosis more precisely than conventional staging systems. Studies on the impact of TILs are heterogeneous and further research is needed. Therefore, this study aims to point out the importance of peritumoral TILs, tumor-infiltrating neutrophils (TINs), and immune subtype classification in PDAC. Material from 57 patients was analyzed with immunohistochemistry performed for CD3, CD8, CD20, CD66b, α-sma, and collagen. Hot spots with peritumoral TILs and TINs were quantified according to the QTiS algorithm and the distance of TILs hot spots to the tumor front was measured. Results were correlated with overall (OS) and progression-free survival (PFS). High densities of peritumoral hot spots with CD3⁺, CD8⁺, and CD20⁺ TILs correlated significantly with improved OS and PFS. Combined immune cell subtypes predicted improved OS and PFS. High infiltration of CD3⁺ TILs predicted progression after 12 months. The location of TILs' hot spots and their distance to the tumor front did not correlate with patient survival. Peritumoral TILs and the composition of the stroma predict OS and PFS in PDAC.

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.