Heterogeneous Stromal Signaling within the Tumor Microenvironment Controls the Metastasis of Pancreatic Cancer

The Effect of Intratumor Heterogeneity in Pancreatic Ductal Adenocarcinoma Progression and Treatment

BACKGROUND AND OBJECTIVES

Pancreatic cancer is one of the most lethal malignancies. Even though many substantial improvements in the survival rates for other major cancer forms were made, pancreatic cancer survival rates have remained relatively unchanged since the 1960s. Even more, no standard classification system for pancreatic cancer is based on cellular biomarkers. This review will discuss and provide updates about the role of stem cells in the progression of PC, the genetic changes associated with it, and the promising biomarkers for diagnosis.

MATERIALS AND METHODS

The search process used PubMed, Cochrane Library, and Scopus databases to identify the relevant and related articles. Articles had to be published in English to be considered.

RESULTS

The increasing number of studies in recent years has revealed that the diversity of cancer-associated fibroblasts is far greater than previously acknowledged, which highlights the need for further research to better understand the various cancer-associated fibroblast subpopulations. Despite the huge diversity in pancreatic cancer, some common features can be noted to be shared among patients. Mutations involving CDKN2, P53, and K-RAS can be seen in a big number of patients, for example. Similarly, some patterns of genes and biomarkers expression and the level of their expression can help in predicting cancer behavior such as metastasis and drug resistance. The current trend in cancer research, especially with the advancement in technology, is to sequence everything in hopes of finding disease-related mutations.

CONCLUSION

Optimizing pancreatic cancer treatment requires clear classification, understanding CAF roles, and exploring stroma reshaping approaches.

Recent advances in cancer-associated fibroblast: Biomarkers, signaling pathways, and therapeutic opportunities

ABSTRACT

Anti-cancer therapies usually focus on tumor cells, but non-tumor stromal components in the tumor microenvironment also play vital roles in tumor initiation and progression, which may be the prognostic factors and potential therapeutic targets. Cancer-associated fibroblasts (CAFs) are the essential component in the tumor environment, exhibiting high heterogeneity in their cell origin and phenotype with diverse functions that influence tumor angiogenesis, immune systems, and metabolism. Single-cell RNA sequencing and genetically engineered mouse models have increased our understanding of CAF diversity, and many subtypes have been defined. However, the precise functions of these subtypes need to be studied and validated. Studies of signaling pathways and epigenetic changes in CAFs facilitate understanding of the phenotypes of CAFs and the crosstalk between tumor cells and CAFs to provide potential therapeutic targets. Some clinical trials, including phase III trials targeting CAFs, have been performed recently. However, few of these trials have generated promising results, which indicates that the complexity of CAFs in the tumor microenvironment remains largely unknown, and in-depth investigations of CAFs should be performed. This review summarizes the research on CAFs, focusing on the heterogeneity of their phenotypes and functions, specific signaling pathways, and the therapeutic strategies involving CAFs. Additionally, we briefly discuss the current technologies commonly used in CAF studies and describe the challenges and future perspectives of CAF research.

CLDN18.2 BiTE Engages Effector and Regulatory T Cells for Antitumor Immune Response in Preclinical Models of Pancreatic Cancer

BACKGROUND & AIMS

BiTE (bispecific T-cell engager) immune therapy has demonstrated clinical activity in multiple tumor indications, but its influence in the tumor microenvironment remains unclear. CLDN18.2 is overexpressed in solid tumors including gastric cancer (GC) and pancreatic ductal adenocarcinoma (PDAC), both of which are characterized by the presence of immunosuppressive cells, including regulatory T cells (Tregs) and few effector T cells (Teffs).

METHODS

We evaluated the activity of AMG 910, a CLDN18.2-targeted half-life extended (HLE) BiTE molecule, in GC and PDAC preclinical models and cocultured Tregs and Teffs in the presence of CLDN18.2-HLE-BiTE.

RESULTS

AMG 910 induced potent, specific cytotoxicity in GC and PDAC cell lines. In GSU and SNU-620 GC xenograft models, AMG 910 engaged human CD3+ T cells with tumor cells, resulting in significant antitumor activity. AMG 910 monotherapy, in combination with a programmed death-1 (PD-1) inhibitor, suppressed tumor growth and enhanced survival in an orthotopic Panc4.14 PDAC model. Moreover, Treg infusion enhanced the antitumor efficacy of AMG 910 in the Panc4.14 model. In syngeneic KPC models of PDAC, treatment with a mouse surrogate CLDN18.2-HLE-BiTE (muCLDN18.2-HLE-BiTE) or the combination with an anti-PD-1 antibody significantly inhibited tumor growth. Tregs isolated from mice bearing KPC tumors that were treated with muCLDN18.2-HLE-BiTE showed decreased T cell suppressive activity and enhanced Teff cytotoxic activity, associated with increased production of type I cytokines and expression of Teff gene signatures.

CONCLUSIONS

Our data suggest that BiTE molecule treatment converts Treg function from immunosuppressive to immune enhancing, leading to antitumor activity in immunologically "cold" tumors.

Targeting BET Proteins Decreases Hyaluronidase-1 in Pancreatic Cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is characterized by the presence of dense stroma that is enriched in hyaluronan (HA), with increased HA levels associated with more aggressive disease. Increased levels of the HA-degrading enzymes hyaluronidases (HYALs) are also associated with tumor progression. In this study, we evaluate the regulation of HYALs in PDAC.

METHODS

Using siRNA and small molecule inhibitors, we evaluated the regulation of HYALs using quantitative real-time PCR (qRT-PCR), Western blot analysis, and ELISA. The binding of BRD2 protein on the HYAL1 promoter was evaluated by chromatin immunoprecipitation (ChIP) assay. Proliferation was evaluated by WST-1 assay. Mice with xenograft tumors were treated with BET inhibitors. The expression of HYALs in tumors was analyzed by immunohistochemistry and by qRT-PCR.

RESULTS

We show that HYAL1, HYAL2, and HYAL3 are expressed in PDAC tumors and in PDAC and pancreatic stellate cell lines. We demonstrate that inhibitors targeting bromodomain and extra-terminal domain (BET) proteins, which are readers of histone acetylation marks, primarily decrease HYAL1 expression. We show that the BET family protein BRD2 regulates HYAL1 expression by binding to its promoter region and that HYAL1 downregulation decreases proliferation and enhances apoptosis of PDAC and stellate cell lines. Notably, BET inhibitors decrease the levels of HYAL1 expression in vivo without affecting the levels of HYAL2 or HYAL3.

CONCLUSIONS

Our results demonstrate the pro-tumorigenic role of HYAL1 and identify the role of BRD2 in the regulation of HYAL1 in PDAC. Overall, these data enhance our understanding of the role and regulation of HYAL1 and provide the rationale for targeting HYAL1 in PDAC.

Hypercapnic Tissue Gene Expression and Survival in Early-Stage Pancreatic Ductal Adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive and lethal cancer. Hypercapnic tumor microenvironments were previously shown to promote cancer chemoresistance. In this study, we aimed to investigate the impact of tissue hypercapnia on PDAC prognosis.

STUDY DESIGN

PDAC cancer-cell lines were cultured in normocapnic (5% CO 2 ) and hypercapnic conditions (10% CO 2 ). RNA was extracted, and whole-exome transcriptome was sequenced. Differentially expressed genes were identified and used to construct a "hypercapnic gene set." PDAC transcriptomic patient data from the Tumor Cancer Genome Atlas was used to calculate single-sample gene set enrichment scores based on each patient's tissue expression of the hypercapnic gene set. Tissue hypercapnic scores (HSs) in PDAC patients (TMN stages Ia-IIb) were determined and correlated with clinicopathological parameters and overall survival.

RESULTS

A cohort of 135 resected stage I-II PDAC patients were assessed in this study. The average age was 65 ± 11.0 years, and the male:female ratio was 74:61. Median overall survival was 19.5 ± 1.4 months. High HSs were associated with increased tumor stage (p < 0.05) and higher lymph-node ratio (p < 0.05). In active smokers, high HS also correlated with smoking pack-years (p < 0.05). Cox regression analysis revealed high HS to be an independent prognostic factor for overall survival (hazard ratio [HR] 2.66, p = 0.004), along with lymph-node ratio (HR 4.2, p = 0.002) and age at diagnosis (HR 2.63, p = 0.01).

CONCLUSIONS

The pancreatic tumor microenvironment plays an integral role in tumor aggressiveness, and our previous in vitro data suggest that hypercapnia promotes an aggressive, more resistant phenotype. Herein, we show that in early-stage pancreatic cancer, hypercapnic tissue signatures corresponded with a worse overall survival.

Robust identification of common genomic biomarkers from multiple gene expression profiles for the prognosis, diagnosis, and therapies of pancreatic cancer

Pancreatic cancer (PC) is one of the leading causes of cancer-related death globally. So, identification of potential molecular signatures is required for diagnosis, prognosis, and therapies of PC. In this study, we detected 71 common differentially expressed genes (cDEGs) between PC and control samples from four microarray gene-expression datasets (GSE15471, GSE16515, GSE71989, and GSE22780) by using robust statistical and machine learning approaches, since microarray gene-expression datasets are often contaminated by outliers due to several steps involved in the data generating processes. Then we detected 8 cDEGs (ADAM10, COL1A2, FN1, P4HB, ITGB1, ITGB5, ANXA2, and MYOF) as the PC-causing key genes (KGs) by the protein-protein interaction (PPI) network analysis. We validated the expression patterns of KGs between case and control samples by box plot analysis with the TCGA and GTEx databases. The proposed KGs showed high prognostic power with the random forest (RF) based prediction model and Kaplan-Meier-based survival probability curve. The KGs regulatory network analysis detected few transcriptional and post-transcriptional regulators for KGs. The cDEGs-set enrichment analysis revealed some crucial PC-causing molecular functions, biological processes, cellular components, and pathways that are associated with KGs. Finally, we suggested KGs-guided five repurposable drug molecules (Linsitinib, CX5461, Irinotecan, Timosaponin AIII, and Olaparib) and a new molecule (NVP-BHG712) against PC by molecular docking. The stability of the top three protein-ligand complexes was confirmed by molecular dynamic (MD) simulation studies. The cross-validation and some literature reviews also supported our findings. Therefore, the finding of this study might be useful resources to the researchers and medical doctors for diagnosis, prognosis and therapies of PC by the wet-lab validation.

An oncogene addiction phosphorylation signature and its derived scores inform tumor responsiveness to targeted therapies

PURPOSE

Oncogene addiction provides important therapeutic opportunities for precision oncology treatment strategies. To date the cellular circuitries associated with driving oncoproteins, which eventually establish the phenotypic manifestation of oncogene addiction, remain largely unexplored. Data suggest the DNA damage response (DDR) as a central signaling network that intersects with pathways associated with deregulated addicting oncoproteins with kinase activity in cancer cells.

EXPERIMENTAL

DESIGN: We employed a targeted mass spectrometry approach to systematically explore alterations in 116 phosphosites related to oncogene signaling and its intersection with the DDR following inhibition of the addicting oncogene alone or in combination with irradiation in MET-, EGFR-, ALK- or BRAF (V600)-positive cancer models. An NSCLC tissue pipeline combining patient-derived xenografts (PDXs) and ex vivo patient organotypic cultures has been established for treatment responsiveness assessment.

RESULTS

We identified an 'oncogene addiction phosphorylation signature' (OAPS) consisting of 8 protein phosphorylations (ACLY S455, IF4B S422, IF4G1 S1231, LIMA1 S490, MYCN S62, NCBP1 S22, P3C2A S259 and TERF2 S365) that are significantly suppressed upon targeted oncogene inhibition solely in addicted cell line models and patient tissues. We show that the OAPS is present in patient tissues and the OAPS-derived score strongly correlates with the ex vivo responses to targeted treatments.

CONCLUSIONS

We propose a score derived from OAPS as a quantitative measure to evaluate oncogene addiction of cancer cell samples. This work underlines the importance of protein phosphorylation assessment for patient stratification in precision oncology and corresponding identification of tumor subtypes sensitive to inhibition of a particular oncogene.

Identification of prognostic genes in the pancreatic adenocarcinoma immune microenvironment by integrated bioinformatics analysis

PURPOSE

Pancreatic adenocarcinoma (PAAD) is one of the most common causes of death among solid tumors, and its pathogenesis remains to be clarified. This study aims to elucidate the value of immune/stromal-related genes in the prognosis of PAAD through comprehensive bioinformatics analysis based on the immune microenvironment and validated in Chinese pancreatic cancer patients.

METHODS

Gene expression profiles of pancreatic cancer patients were obtained from TCGA database. Differentially expressed genes (DEGs) were identified based on the ESTIMATE algorithm. Gene co-expression networks were constructed using WGCNA. In the key module, survival analysis was used to reveal the prognostic value. Subsequently, we performed functional enrichment analysis to construct a protein-protein interaction (PPI) network. The relationship between tumor immune infiltration and hub genes was analyzed by TIMER and CIBERSORT. Finally, it was validated in the GEO database and in tissues of Chinese pancreatic cancer patients.

RESULTS

In the TCGA pancreatic cancer cohort, a low immune/stromal score was associated with a good prognosis. After bioinformatic analysis, 57 genes were identified to be significantly associated with pancreatic cancer prognosis. Among them, up-regulation of four genes (COL6A3, PLAU, MMP11 and MMP14) indicated poor prognosis and was associated with multiple immune cell infiltration. IHC results showed that PLAU protein levels from Chinese pancreatic cancer tissues were significantly higher than those from adjacent non-tumor tissues and were also associated with tumor TNM stage and lymph node metastasis.

CONCLUSION

In conclusion, this study demonstrates that PLAU may serve as a new diagnostic and therapeutic target, which is highly expressed in Chinese pancreatic cancer tissues and associated with lymph node metastasis.

Thiosemicarbazones reprogram pancreatic cancer bidirectional oncogenic signaling between cancer cells and stellate cells to suppress desmoplasia

Standard treatments have shown dismal activity against pancreatic cancer (PC), due in part to the development of a dense stroma (desmoplasia). This perspective discusses the development of the di-2-pyridylketone thiosemicarbazones that overcomes bidirectional oncogenic signaling between PC cells and pancreatic stellate cells (PSCs), which is critical for desmoplasia development. This activity is induced by the up-regulation of the metastasis suppressor, N-myc downstream-regulated gene-1 (NDRG1), which inhibits oncogenic signaling via HGF, IGF-1 and Sonic Hedgehog pathway. More recent studies have deciphered additional pathways including those mediated by Wnt and tenascin C that are secreted by PSCs to activate β-catenin and YAP/TAZ signaling in PC cells. Suppression of bidirectional signaling between cell types presents a unique therapeutic opportunity.

Annexin A2: The Diversity of Pathological Effects in Tumorigenesis and Immune Response

Annexin A2 (ANXA2) is widely used as a marker in a variety of tumors. By regulating multiple signal pathways, ANXA2 promotes the epithelial-mesenchymal transition, which can cause tumorigenesis and accelerate thymus degeneration. The elevated ANXA2 heterotetramer facilitates the production of plasmin, which participates in pathophysiologic processes such as tumor cell invasion and metastasis, bleeding diseases, angiogenesis, inducing the expression of inflammatory factors. In addition, the ANXA2 on the cell membrane mediates immune response via its interaction with surface proteins of pathogens, C1q, toll-like receptor 2, anti-dsDNA antibodies and immunoglobulins. Nuclear ANXA2 plays a role as part of a primer recognition protein complex that enhances DNA synthesis and cells proliferation by acting on the G1-S phase of the cell. ANXA2 reduction leads to the inhibition of invasion and metastasis in multiple tumor cells, bleeding complications in acute promyelocytic leukemia, retinal angiogenesis, autoimmunity response and tumor drug resistance. In this review, we provide an update on the pathological effects of ANXA2 in both tumorigenesis and the immune response. We highlight ANXA2 as a critical protein in numerous malignancies and the immune host response.

Recent advances in targeted drug delivery for the treatment of pancreatic ductal adenocarcinoma

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) has become a serious health problem with high impact worldwide. The heterogeneity of PDAC makes it difficult to apply drug delivery systems (DDS) used in other cancer models, for example, the poorly developed vascular system makes anti-angiogenic therapy ineffective. Due to its various malignant pathological changes, drug delivery against PDAC is a matter of urgent concern. Based on this situation, various drug delivery strategies specially designed for PDAC have been generated.

AREAS COVERED

This review will briefly describe how delivery systems can be designed through nanotechnology and formulation science. Most research focused on penetrating the stromal barrier, exploiting and alleviating the hypoxic microenvironment, targeting immune cells, or designing vaccines, and combination therapies. This review will summarize the ways to reverse the malignant pathological features of PDAC and hopefully provide ideas for subsequent studies.

EXPERT OPINION

Drug delivery systems designed to achieve penetrating functions or to alleviate hypoxia and activate immunity have achieved good therapeutic results in animal models in several studies. In future studies, there is a need to deliver PDAC therapeutics in a more precise manner, or the use of drug carriers for multiple functions simultaneously, are potential therapeutic strategy.

High-dimensionality reduction clustering of complex carbohydrates to study lung cancer metabolic heterogeneity

The tumor microenvironment contains a heterogeneous population of stromal and cancer cells that engage in metabolic crosstalk to ultimately promote tumor growth and contribute to progression. Due to heterogeneity within solid tumors, pooled mass spectrometry workflows are less sensitive at delineating unique metabolic perturbations between stromal and immune cell populations. Two critical, but understudied, facets of glucose metabolism are anabolic pathways for glycogen and N-linked glycan biosynthesis. Together, these complex carbohydrates modulate bioenergetics and protein-structure function, and create functional microanatomy in distinct cell populations within the tumor heterogeneity. Herein, we combine high-dimensionality reduction and clustering (HDRC) analysis with matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) and demonstrate its ability for the comprehensive assessment of tissue histopathology and metabolic heterogeneity in human FFPE sections. In human lung adenocarcinoma (LUAD) tumor tissues, HDRC accurately clusters distinct regions and cell populations within the tumor microenvironment, including tumor cells, tumor-infiltrating lymphocytes, cancer-associated fibroblasts, and necrotic regions. In-depth pathway enrichment analyses revealed unique metabolic pathways are associated with each distinct pathological region. Further, we highlight the potential of HDRC analysis to study complex carbohydrate metabolism in a case study of lung cancer disparity. Collectively, our results demonstrate the promising potentials of HDRC of pixel-based carbohydrate analysis to study cell-type and regional-specific stromal signaling within the tumor microenvironment.

Cancer-associated fibroblast heterogeneity is associated with organ-specific metastasis in pancreatic ductal adenocarcinoma

Background

Metastasis occurs in the majority of pancreatic ductal adenocarcinoma (PDAC) patients at diagnosis or following resection. Patients with liver metastasis and those with lung metastasis have significantly different prognosis. Here, we sought to understand how cancer-associated fibroblasts (CAFs) play roles in the development of organ-specific metastasis.

Methods

PDAC tumor cell lines established from the primary tumors with liver and lung metastasis potentials, respectively, in Kras/p53 mutation conditional knock-in (KPC) mice were co-cultured with matched CAFs or mouse mesenchymal stem cells. CAFs were isolated from metastases and subjected to DNA methylation and whole transcriptomic RNA sequencing analysis.

Results

The ability of mouse PDAC tumor cell lines in developing liver or lung-specific metastases was demonstrated in orthotopic models. Tumor cells associated with liver metastasis potential, but not those associated with lung metastasis potential, induced the methylation of metabolism genes including NQO1 and ALDH1a3 and subsequent downregulated mRNA expression of a broader group of metabolism genes in CAFs. DNA methylation and downregulation of metabolism genes in CAFs in liver metastasis, but not those in lung metastasis, appeared to be regulated by DNA methyltransferase. Tumor cells associated with liver metastasis potential, but not those associated with lung metastasis potential, induce inflammatory CAF (iCAF) signatures. CAFs from liver metastasis demonstrated a more homogenous iCAF phenotype, whereas CAFs from lung metastasis maintained the heterogeneity.

Conclusions

PDAC with organ-specific metastatic potentials has different capacities in inducing methylation of metabolism genes in CAFs, modulating CAF phenotypes, and resulting in different levels of heterogeneity of CAFs in different metastatic niches.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13045-021-01203-1.

Pancreatic Cancer Small Extracellular Vesicles (Exosomes): A Tale of Short- and Long-Distance Communication

Simple Summary

Even today, pancreatic cancer still has a dismal prognosis. It is characterized by a lack of early symptoms and thus late diagnosis as well as early metastasis. The majority of patients suffer from pancreatic ductal adenocarcinoma (PDAC). PDACs communicate extensively with cellular components of their microenvironment, but also with distant metastatic niches to facilitate tumor progression and dissemination. This crosstalk is substantially enabled by small extracellular vesicles (sEVs, exosomes) with a size of 30–150 nm that are released from the tumor cells. sEVs carry bioactive cargos that reprogram target cells to promote tumor growth, migration, metastasis, immune evasion, or chemotherapy resistance. Interestingly, sEVs also carry novel diagnostic, prognostic and potentially also predictive biomarkers. Moreover, engineered sEVs may be utilized as therapeutic agents, improving treatment options. The role of sEVs for PDAC development, progression, diagnosis, prognosis, and treatment is the focus of this review.

Abstract

Even with all recent advances in cancer therapy, pancreatic cancer still has a dismal 5-year survival rate of less than 7%. The most prevalent tumor subtype is pancreatic ductal adenocarcinoma (PDAC). PDACs display an extensive crosstalk with their tumor microenvironment (TME), e.g., pancreatic stellate cells, but also immune cells to regulate tumor growth, immune evasion, and metastasis. In addition to crosstalk in the local TME, PDACs were shown to induce the formation of pre-metastatic niches in different organs. Recent advances have attributed many of these interactions to intercellular communication by small extracellular vesicles (sEVs, exosomes). These nanovesicles are derived of endo-lysosomal structures (multivesicular bodies) with a size range of 30–150 nm. sEVs carry various bioactive cargos, such as proteins, lipids, DNA, mRNA, or miRNAs and act in an autocrine or paracrine fashion to educate recipient cells. In addition to tumor formation, progression, and metastasis, sEVs were described as potent biomarker platforms for diagnosis and prognosis of PDAC. Advances in sEV engineering have further indicated that sEVs might once be used as effective drug carriers. Thus, extensive sEV-based communication and applications as platform for biomarker analysis or vehicles for treatment suggest a major impact of sEVs in future PDAC research.

Recapitulating the Cancer Microenvironment Using Bioprinting Technology for Precision Medicine

The complex and heterogenous nature of cancer contributes to the development of cancer cell drug resistance. The construction of the cancer microenvironment, including the cell-cell interactions and extracellular matrix (ECM), plays a significant role in the development of drug resistance. Traditional animal models used in drug discovery studies have been associated with feasibility issues that limit the recapitulation of human functions; thus, in vitro models have been developed to reconstruct the human cancer system. However, conventional two-dimensional and three-dimensional (3D) in vitro cancer models are limited in their ability to emulate complex cancer microenvironments. Advances in technologies, including bioprinting and cancer microenvironment reconstruction, have demonstrated the potential to overcome some of the limitations of conventional models. This study reviews some representative bioprinted in vitro models used in cancer research, particularly fabrication strategies for modeling and consideration of essential factors needed for the reconstruction of the cancer microenvironment. In addition, we highlight recent studies that applied such models, including application in precision medicine using advanced bioprinting technologies to fabricate biomimetic cancer models. Furthermore, we discuss current challenges in 3D bioprinting and suggest possible strategies to construct in vitro models that better mimic the pathophysiology of the cancer microenvironment for application in clinical settings.

Oridonin induces autophagy-mediated cell death in pancreatic cancer by activating the c-Jun N-terminal kinase pathway and inhibiting phosphoinositide 3-kinase signaling

Background

Oridonin is a diterpenoid isolated from Rabdosia rubescens that has potent anticancer activity. This study set out to investigate the antitumor effects of oridonin in pancreatic carcinoma (PC) and their underlying mechanisms.

Methods

To investigate the antitumor effects of oridonin, we developed an orthotopic C57BL/6 mouse model of PC. After successful establishment of the model, the mice were given a daily intraperitoneal injection of phosphate-buffered saline containing 0.1% dimethyl sulfoxide or oridonin for 2 weeks. In vitro experiments including MTT assay and flow cytometry were performed to examine cell viability and apoptosis. Panc-1 and Panc02 cells were transfected with a green fluorescent protein (GFP)-LC3 plasmid. After the cells had been treated with or without 20 μM oridonin and 10 μM 3-MA, the formation of GFP-LC3 puncta was detected by fluorescence microscopy. The levels of the autophagy-related proteins Beclin-1, LC3, and p62 were measured by western blotting.

Results

Oridonin inhibited the proliferation of PC cells and induced their apoptosis in vitro and in vivo. Treatment with oridonin also led to an increase in the quantity of LC3B II protein and upregulation of the p62 and Beclin-1 levels in PC cells. The effects of oridonin on PC cell proliferation, apoptosis, and autophagy were mediated via the simultaneous inhibition of the phosphoinositide 3-kinase pathway and activation of the c-Jun N-terminal kinase pathway.

Conclusions

Our study is the first to confirm the antitumor and autophagy-activating effects of oridonin on PC cells. In light of these results, oridonin may be a promising therapeutic agent for PC.

Ref-1 redox activity alters cancer cell metabolism in pancreatic cancer: exploiting this novel finding as a potential target

BACKGROUND

Pancreatic cancer is a complex disease with a desmoplastic stroma, extreme hypoxia, and inherent resistance to therapy. Understanding the signaling and adaptive response of such an aggressive cancer is key to making advances in therapeutic efficacy. Redox factor-1 (Ref-1), a redox signaling protein, regulates the conversion of several transcription factors (TFs), including HIF-1α, STAT3 and NFκB from an oxidized to reduced state leading to enhancement of their DNA binding. In our previously published work, knockdown of Ref-1 under normoxia resulted in altered gene expression patterns on pathways including EIF2, protein kinase A, and mTOR. In this study, single cell RNA sequencing (scRNA-seq) and proteomics were used to explore the effects of Ref-1 on metabolic pathways under hypoxia.

METHODS

scRNA-seq comparing pancreatic cancer cells expressing less than 20% of the Ref-1 protein was analyzed using left truncated mixture Gaussian model and validated using proteomics and qRT-PCR. The identified Ref-1's role in mitochondrial function was confirmed using mitochondrial function assays, qRT-PCR, western blotting and NADP assay. Further, the effect of Ref-1 redox function inhibition against pancreatic cancer metabolism was assayed using 3D co-culture in vitro and xenograft studies in vivo.

RESULTS

Distinct transcriptional variation in central metabolism, cell cycle, apoptosis, immune response, and genes downstream of a series of signaling pathways and transcriptional regulatory factors were identified in Ref-1 knockdown vs Scrambled control from the scRNA-seq data. Mitochondrial DEG subsets downregulated with Ref-1 knockdown were significantly reduced following Ref-1 redox inhibition and more dramatically in combination with Devimistat in vitro. Mitochondrial function assays demonstrated that Ref-1 knockdown and Ref-1 redox signaling inhibition decreased utilization of TCA cycle substrates and slowed the growth of pancreatic cancer co-culture spheroids. In Ref-1 knockdown cells, a higher flux rate of NADP + consuming reactions was observed suggesting the less availability of NADP + and a higher level of oxidative stress in these cells. In vivo xenograft studies demonstrated that tumor reduction was potent with Ref-1 redox inhibitor similar to Devimistat.

CONCLUSION

Ref-1 redox signaling inhibition conclusively alters cancer cell metabolism by causing TCA cycle dysfunction while also reducing the pancreatic tumor growth in vitro as well as in vivo.

Roles of CCL2-CCR2 Axis in the Tumor Microenvironment

Chemokines are a small family of cytokines that were first discovered as chemotactic factors in leukocytes during inflammation, and reports on the relationship between chemokines and cancer progression have recently been increasing. The CCL2-CCR2 axis is one of the major chemokine signaling pathways, and has various functions in tumor progression, such as increasing tumor cell proliferation and invasiveness, and creating a tumor microenvironment through increased angiogenesis and recruitment of immunosuppressive cells. This review discusses the roles of the CCL2-CCR2 axis and the tumor microenvironment in cancer progression and their future roles in cancer therapy.

Pancreatic Adenocarcinoma Therapeutics Targeting RTK and TGF Beta Receptor

Despite the improved overall survival rates in most cancers, pancreatic cancer remains one of the deadliest cancers in this decade. The rigid microenvironment, which majorly comprises cancer-associated fibroblasts (CAFs), plays an important role in the obstruction of pancreatic cancer therapy. To overcome this predicament, the signaling of receptor tyrosine kinases (RTKs) and TGF beta receptor (TGFβR) in both pancreatic cancer cell and supporting CAF should be considered as the therapeutic target. The activation of receptors has been reported to be aberrant to cell cycle regulation, and signal transduction pathways, such as growth-factor induced proliferation, and can also influence the apoptotic sensitivity of tumor cells. In this article, the regulation of RTKs/TGFβR between pancreatic ductal adenocarcinoma (PDAC) and CAFs, as well as the RTKs/TGFβR inhibitor-based clinical trials on pancreatic cancer are reviewed.

Combinatorial Treatment of Tinzaparin and Chemotherapy Can Induce a Significant Antitumor Effect in Pancreatic Cancer

Pancreatic Cancer (PC) is recognized as a highly thrombogenic tumor; thus, low-molecular-weight heparin (LMWH) such as tinzaparin is routinely used for PC patients. On the basis of combinatorial therapy approaches to treat highly malignant and refractory cancers such as PC, we hypothesized that tinzaparin can augment the effectiveness of traditional chemotherapeutic drugs and induce efficient antitumor activity. PANC-1 and MIAPaCa-2 were incubated alone or in combination with tinzaparin, nab-paclitaxel and gemcitabine. In vivo evaluation of these compounds was performed in a NOD/SCID mouse using a model injected with PANC-1. Tinzaparin enhances the anti-tumor effects of nab-paclitaxel and gemcitabine in mtKRAS PC cell lines via apoptosis in in vitro experiments. The triple combination power acts through the induction of apoptosis, reduction of the proliferative potential and angiogenesis; hence, contributing to a decrease in tumor volume observed in vivo. The triple regimen provided an extra 24.3% tumor reduction compared to the double combination (gemcitabine plus nab-paclitaxel). Combinatorial strategies can create novel therapeutic approaches for the treatment of patients with PC, achieving a better clinical outcome and prolonged survival. Further prospective randomized research is needed and the investigation of various concentrations of tinzaparin above 150 UI/Kg, would potentially provide a valuable synergistic effect to the conventional therapeutic compounds.

Annexin Animal Models-From Fundamental Principles to Translational Research

Routine manipulation of the mouse genome has become a landmark in biomedical research. Traits that are only associated with advanced developmental stages can now be investigated within a living organism, and the in vivo analysis of corresponding phenotypes and functions advances the translation into the clinical setting. The annexins, a family of closely related calcium (Ca²⁺)- and lipid-binding proteins, are found at various intra- and extracellular locations, and interact with a broad range of membrane lipids and proteins. Their impacts on cellular functions has been extensively assessed in vitro, yet annexin-deficient mouse models generally develop normally and do not display obvious phenotypes. Only in recent years, studies examining genetically modified annexin mouse models which were exposed to stress conditions mimicking human disease often revealed striking phenotypes. This review is the first comprehensive overview of annexin-related research using animal models and their exciting future use for relevant issues in biology and experimental medicine.

Stroma secreted IL6 selects for "stem-like" population and alters pancreatic tumor microenvironment by reprogramming metabolic pathways

Pancreatic adenocarcinoma is a devastating disease with an abysmal survival rate of 9%. A robust fibro-inflammatory and desmoplastic stroma, characteristic of pancreatic cancer, contribute to the challenges in developing viable therapeutic strategies in this disease. Apart from constricting blood vessels and preventing efficient drug delivery to the tumor, the stroma also contributes to the aggressive biology of cancer along with its immune-evasive microenvironment. In this study, we show that in pancreatic tumors, the developing stroma increases tumor initiation frequency in pancreatic cancer cells in vivo by enriching for CD133 + aggressive "stem-like" cells. Additionally, the stromal fibroblasts secrete IL6 as the major cytokine, increases glycolytic flux in the pancreatic tumor cells, and increases lactate efflux in the microenvironment via activation of the STAT signaling pathway. We also show that the secreted lactate favors activation of M2 macrophages in the tumor microenvironment, which excludes CD8 + T cells in the tumor. Our data additionally confirms that the treatment of pancreatic tumors with anti-IL6 antibody results in tumor regression as well as decreased CD133 + population within the tumor. Furthermore, inhibiting the lactate efflux in the microenvironment reduces M2 macrophages, and makes pancreatic tumors more responsive to anti-PD1 therapy. This suggests that stromal IL6 driven metabolic reprogramming plays a significant role in the development of an immune-evasive microenvironment. In conclusion, our study shows that targeting the metabolic pathways affected by stromal IL6 can make pancreatic tumors amenable to checkpoint inhibitor therapy.

Targeting of the Hedgehog/GLI and mTOR pathways in advanced pancreatic cancer, a phase 1 trial of Vismodegib and Sirolimus combination

BACKGROUND/OBJECTIVES

Preclinical data indicated a functional and molecular interaction between Hedgehog (HH)/GLI and PI3K-AKT-mTOR pathways promoting pancreatic ductal adenocarcinoma (PDAC). A phase I study was conducted of Vismodegib and Sirolimus combination to evaluate maximum tolerated dose (MTD) and preliminary anti-tumor efficacy.

METHODS

Cohort I included advanced solid tumors patients following a traditional 3 + 3 design. Vismodegib was orally administered at 150 mg daily with Sirolimus starting at 3 mg daily, increasing to 6 mg daily at dose level 2. Cohort II included only metastatic PDAC patients. Anti-tumor efficacy was evaluated every two cycles and target assessment at pre-treatment and after a single cycle.

RESULTS

Nine patient were enrolled in cohort I and 22 patients in cohort II. Twenty-eight patients were evaluated for dose-limiting toxicities (DLTs). One DLT was observed in each cohort, consisting of grade 2 mucositis and grade 3 thrombocytopenia. The MTD for Vismodegib and Sirolimus were 150 mg daily and 6 mg daily, respectively. The most common grade 3-4 toxicities were fatigue, thrombocytopenia, dehydration, and infections. A total of 6 patients had stable disease. No partial or complete responses were observed. Paired biopsy analysis before and after the first cycle in cohort II consistently demonstrated reduced GLI1 expression. Conversely, GLI and mTOR downstream targets were not significantly affected.

CONCLUSIONS

The combination of Vismodegib and Sirolimus was well tolerated. Clinical benefit was limited to stable disease in a subgroup of patients. Targeting efficacy demonstrated consistent partial decreases in HH/GLI signaling with limited impact on mTOR signaling. These findings conflict with pre-clinical models and warrant further investigations.

Pancreatic cancer stroma: an update on therapeutic targeting strategies

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer-related mortality in the Western world with limited therapeutic options and dismal long-term survival. The neoplastic epithelium exists within a dense stroma, which is recognized as a critical mediator of disease progression through direct effects on cancer cells and indirect effects on the tumour immune microenvironment. The three dominant entities in the PDAC stroma are extracellular matrix (ECM), vasculature and cancer-associated fibroblasts (CAFs). The ECM can function as a barrier to effective drug delivery to PDAC cancer cells, and a multitude of strategies to target the ECM have been attempted in the past decade. The tumour vasculature is a complex system and, although multiple anti-angiogenesis agents have already failed late-stage clinical trials in PDAC, other vasculature-targeting approaches aimed at vessel normalization and tumour immunosensitization have shown promise in preclinical models. Lastly, PDAC CAFs participate in active cross-talk with cancer cells within the tumour microenvironment. The existence of intratumoural CAF heterogeneity represents a paradigm shift in PDAC CAF biology, with myofibroblastic and inflammatory CAF subtypes that likely make distinct contributions to PDAC progression. In this Review, we discuss our current understanding of the three principal constituents of PDAC stroma, their effect on the prevalent immune landscape and promising therapeutic targets within this compartment.

The CCL20-CCR6 Axis in Cancer Progression

Chemokines, which are basic proteins that exert their effects via G protein-coupled receptors and a subset of the cytokine family, are mediators deeply involved in leukocyte migration during an inflammatory reaction. Chemokine (C-C motif) ligand 20 (CCL20), also known as macrophage inflammatory protein (MIP)-3α, liver activation regulated chemokine (LARC), and Exodus-1, is a small protein that is physiologically expressed in the liver, colon, and skin, is involved in tissue inflammation and homeostasis, and has a specific receptor C-C chemokine receptor 6 (CCR6). The CCL20-CCR6 axis has long been known to be involved in inflammatory and infectious diseases, such as rheumatoid arthritis and human immunodeficiency virus infections. Recently, however, reports have shown that the CCL20-CCR6 axis is associated with several cancers, including hepatocellular carcinoma, colorectal cancer, breast cancer, pancreatic cancer, cervical cancer, and kidney cancer. The CCL20-CCR6 axis promotes cancer progression directly by enhancing migration and proliferation of cancer cells and indirectly by remodeling the tumor microenvironment through immune cell control. The present article reviewed the role of the CCL20-CCR6 axis in cancer progression and its potential as a therapeutic target.

Global targetome analysis reveals critical role of miR-29a in pancreatic stellate cell mediated regulation of PDAC tumor microenvironment

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive forms of malignancies with a nearly equal incidence and mortality rates in patients. Pancreatic stellate cells (PSCs) are critical players in PDAC microenvironment to promote the aggressiveness and pathogenesis of the disease. Dysregulation of microRNAs (miRNAs) have been shown to play a significant role in progression of PDAC. Earlier, we observed a PSC-specific downregulation of miR-29a in PDAC pancreas, however, the mechanism of action of the molecule in PSCs is still to be elucidated. The current study aims to clarify the regulation of miR-29a in PSCs and identifies functionally important downstream targets that contribute to tumorigenic activities during PDAC progression.

METHODS

In this study, using RNAseq approach, we performed transcriptome analysis of paired miR-29a overexpressing and control human PSCs (hPSCs). Enrichment analysis was performed with the identified differentially expressed genes (DEGs). miR-29a targets in the dataset were identified, which were utilized to create network interactions. Western blots were performed with the top miR-29a candidate targets in hPSCs transfected with miR-29a mimic or scramble control.

RESULTS

RNAseq analysis identified 202 differentially expressed genes, which included 19 downregulated direct miR-29a targets. Translational repression of eight key pro-tumorigenic and -fibrotic targets namely IGF-1, COL5A3, CLDN1, E2F7, MYBL2, ITGA6 and ADAMTS2 by miR-29a was observed in PSCs. Using pathway analysis, we find that miR-29a modulates effectors of IGF-1-p53 signaling in PSCs that may hinder carcinogenesis. We further observe a regulatory role of the molecule in pathways associated with PDAC ECM remodeling and tumor-stromal crosstalk, such as INS/IGF-1, RAS/MAPK, laminin interactions and collagen biosynthesis.

CONCLUSIONS

Together, our study presents a comprehensive understanding of miR-29a regulation of PSCs, and identifies essential pathways associated with PSC-mediated PDAC pathogenesis. The findings suggest an anti-tumorigenic role of miR-29a in the context of PSC-cancer cell crosstalk and advocates for the potential of the molecule in PDAC targeted therapies.

Inhibition of miR-21 Regulates Mutant KRAS Effector Pathways and Intercepts Pancreatic Ductal Adenocarcinoma Development

Almost all pancreatic ductal adenocarcinomas (PDA) develop following KRAS activation, which triggers epithelial transformation and recruitment of desmoplastic stroma through additional transcriptional and epigenetic regulation, but only a few of these regulatory mechanisms have been described. We profiled dysregulated miRNAs starting with the earliest premalignant pancreatic intraepithelial neoplasias (PanIN) in genetically engineered mutated KRAS and P53 (KPC) mice programmed to recapitulate human PDA tumorigenesis. We identified miR-21 and miR-224 as cell-specific and compartment-specific regulators in PanINs and PDA. miR-21 is overexpressed in tumor epithelial cells of premalignant ducts, while miR-224 is overexpressed in cancer-associated fibroblasts in PDA stroma. Inhibition of miR-21 reverted protumorigenic functionalities to baseline levels. Overexpression of miR-224 induced activated phenotypes in normal fibroblasts. In vivo miR-21 inhibition improved survival in established PDA. Importantly, early systemic miR-21 inhibition completely intercepted premalignant progression. Finally, an evaluation of miR-21 expression in the PDA cohort of The Cancer Genome Atlas identified a correlation between tumor epithelial cell content and miR-21 expression in human tumors providing further rationale for conducting human studies. Thus, miR-21 may be useful for early PanIN detection, and for intercepting developing premalignant pancreatic lesions and other KRAS-driven premalignancies.

Insulin-Like Growth Factor-1 Receptor Expression and Disease Recurrence and Survival in Patients with Resected Pancreatic Ductal Adenocarcinoma

BACKGROUND

Insulin-like growth factor-1 receptor (IGF1R) signaling is important in pancreatic ductal adenocarcinoma (PDAC) biology, but little is known regarding IGF1R expression and patient characteristics and outcomes.

METHODS

In 365 patients with resected PDAC, we evaluated IGF1R protein expression using IHC on whole-slide sections and IGF1R genomic status using next-generation sequencing. Associations of IGF1R expression, measured by H-scores incorporating staining intensity and proportion of positive tumor cells, with disease-free survival (DFS) and overall survival (OS) were evaluated in 317 and 321 patients, respectively, using Cox regression adjusting for known prognostic factors.

RESULTS

Higher IGF1R expression in tumor cells was associated with worse DFS comparing highest versus lowest expression tertiles [median DFS, 10.8 vs. 16.1 months; adjusted hazard ratio (HR), 1.73; 95% confidence interval (CI), 1.24-2.44; P _trend = 0.002] and worse OS (median OS, 17.4 vs. 25.8 months; HR, 1.39; 95% CI, 1.00-1.92; P _trend = 0.046). The association between high IGF1R expression and reduced DFS was identified primarily among patients with a preoperative body mass index ≥25 kg/m² (HR, 4.27; 95% CI, 2.03-8.96, comparing extreme tertiles; P _interaction = 0.032). KRAS-mutant tumors had greater IGF1R expression, and IGF1R expression in tumor epithelium was inversely correlated with that in stromal cells. Mutations in IGF1R were infrequent, and no overt loss-of-function alterations were identified. Higher IGF1R expression was modestly associated with higher gene copy number (Pearson correlation coefficient = 0.26, P < 0.001).

CONCLUSIONS

Higher IGF1R protein expression was associated with worse patient outcomes in resected PDAC.

IMPACT

IGF1R expression in PDAC represents a potential biomarker to guide patient selection for more aggressive, multidrug regimens in the adjuvant setting.

An Immunological Glance on Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) has still a dismal prognosis. Different factors such as mutational landscape, intra- and intertumoral heterogeneity, stroma, and immune cells impact carcinogenesis of PDAC associated with an immunosuppressive microenvironment. Different cell types with partly opposing roles contribute to this milieu. In recent years, immunotherapeutic approaches, including checkpoint inhibitors, were favored to treat cancers, albeit not every cancer entity exhibited benefits in a similar way. Indeed, immunotherapies rendered little success in pancreatic cancer. In this review, we describe the communication between the immune system and pancreatic cancer cells and propose some rationale why immunotherapies may fail in the context of pancreatic cancer. Moreover, we delineate putative strategies to sensitize PDAC towards immunological therapeutics and highlight the potential of targeting neoantigens.

NGF from pancreatic stellate cells induces pancreatic cancer proliferation and invasion by PI3K/AKT/GSK signal pathway

Pancreatic cancer (PC) is a continuously high lethal disease, and the tumour microenvironment plays a pivotal role during PC progression. Herein, we focus on that the Nerve growth factor (NGF)/Tropomyosin-related kinase A (TrkA), in pancreatic stellate cells-pancreatic cancer cells (PSCs-PC cells) co-culture system, influences PC proliferation and invasion. The model of PC cells and PSCs was directly co-cultured in a no-touch manner, using the Transwell as the co-culture system. NGF and TrkA expression was measured in cultured system by real-time PCR, immunofluorescence, Western blotting analysis or ELISA. Small interfering RNA transfection was used to regulate the expression of TrkA in PC cells. The promotion of cancer invasion was investigated using Matrigel Transwell assay. In our study, NGF/TrkA is overexpressed in PSCs-PC cells co-culture system and promotes the invasion and proliferation of PC cells. And the epithelial-mesenchymal transition-related genes are influenced by si-TrkA. What's more, NGF/TrkA regulates the PC cell proliferation and invasion via activation of PI3K/AKT/GSK signalling. The present study demonstrated NGF/TrkA promoted the PC cell proliferation and invasion in the co-culture system by the activation of the PI3K/AKT/GSK signal cascade, providing a potential therapeutic target for PC patients.

Mechanisms of the Antitumor Activity of Low Molecular Weight Heparins in Pancreatic Adenocarcinomas

Immune checkpoint inhibitors have revolutionized cancer treatment in the last decade. Despite the progress in immunotherapy, most pancreatic cancer patients still do not derive benefit when receiving immune-based therapies. Recently, resistance mechanisms to immune therapies have been mainly focused on tumor microenvironment properties. Pancreatic cancer is considered one of the most lethal and difficult to treat tumors due to its highly immunosuppressive and desmoplastic microenvironment. Low molecular weight heparins (LMWHs) have been used for the treatment and prevention of thromboembolic disease in these patients. However, many nonanticoagulant properties attributed to LMWHs have been described. Exploiting LMWH properties in a combined treatment modality with immune checkpoint inhibition and chemotherapy could provide a new approach in the management of pancreatic adenocarcinoma patients. The ability of LMWH to interfere with various aspects of the tumor microenvironment could result in both the alleviation of immunosuppression and improvement in drug delivery within the tumor, leading to higher cancer cell destruction rates and more potent immune system activity that would, ultimately, lead to better patient outcomes.

Sonic Hedgehog Signaling in Organogenesis, Tumors, and Tumor Microenvironments

During mammalian embryonic development, primary cilia transduce and regulate several signaling pathways. Among the various pathways, Sonic hedgehog (SHH) is one of the most significant. SHH signaling remains quiescent in adult mammalian tissues. However, in multiple adult tissues, it becomes active during differentiation, proliferation, and maintenance. Moreover, aberrant activation of SHH signaling occurs in cancers of the skin, brain, liver, gallbladder, pancreas, stomach, colon, breast, lung, prostate, and hematological malignancies. Recent studies have shown that the tumor microenvironment or stroma could affect tumor development and metastasis. One hypothesis has been proposed, claiming that the pancreatic epithelia secretes SHH that is essential in establishing and regulating the pancreatic tumor microenvironment in promoting cancer progression. The SHH signaling pathway is also activated in the cancer stem cells (CSC) of several neoplasms. The self-renewal of CSC is regulated by the SHH/Smoothened receptor (SMO)/Glioma-associated oncogene homolog I (GLI) signaling pathway. Combined use of SHH signaling inhibitors and chemotherapy/radiation therapy/immunotherapy is therefore key in targeting CSCs.

CCL20 Signaling in the Tumor Microenvironment

CCL20, as a chemokine, plays an important role in rheumatoid arthritis, psoriasis, and other diseases by binding to its receptor CCR6. Recent 10 years' research has demonstrated that CCL20 also contributes to the progression of many cancers, such as liver cancer, colon cancer, breast cancer, pancreatic cancer, and gastric cancer. This article reviews and discusses the previous studies on CCL20 roles in cancers from the aspects of its specific effects on various cancers, its remodeling on tumor microenvironment (TME), its synergistic effects with other cytokines in tumor microenvironment, and the specific mechanisms of CCL20 signal activation, illustrating CCL20 signaling in TME from multiple directions.

Metastasis in Pancreatic Ductal Adenocarcinoma: Current Standing and Methodologies

Pancreatic ductal adenocarcinoma is an extremely aggressive disease with a high metastatic potential. Most patients are diagnosed with metastatic disease, at which the five-year survival rate is only 3%. A better understanding of the mechanisms that drive metastasis is imperative for the development of better therapeutic interventions. Here, we take the reader through our current knowledge of the parameters that support metastatic progression in pancreatic ductal adenocarcinoma, and the experimental models that are at our disposal to study this process. We also describe the advantages and limitations of these models to study the different aspects of metastatic dissemination.

ARHGAP4 regulates the cell migration and invasion of pancreatic cancer by the HDAC2/β-catenin signaling pathway

β-catenin is a subunit of the cadherin protein complex and acts as an intracellular signal transducer in the Wnt signaling pathway that mediates multiple cellular processes, such as cell migration and invasion. HDAC2 (histone deacetylase 2), a deacetylase that maintains histone H3 in a deacetylated state in the promoter region of Wnt-targeted genes where β-catenin is bound, negatively regulating β-catenin activation. However, the regulation of HDAC2/β-catenin pathway remains unclear. Here, we report ARHGAP4 as a new regulator of the β-catenin pathway that regulates cell invasion and migration of pancreatic cancer as well as the downstream effector MMP2 and MMP9 expression in vitro. Mechanistically, ARHGAP4 interacts with and ubiquitinates HDAC2, which in turn inhibits β-catenin activation. Furthermore, treatment of CAY10683, an HDAC2 inhibitor, and XAV939, a Wnt/β-catenin pathway inhibitor, attenuated the effects of ARHGAP4 silencing on pancreatic cancer cells. Overall, our findings establish ARHGAP4 as a novel regulator of HDAC2/β-catenin pathway with a critical role in tumorigenesis.

Precision medicine in pancreatic cancer: treating every patient as an exception

Patients with pancreatic cancer have not benefited from recent improvements in overall survival brought about by precision medicine in other malignancies. This failure is not due to a dearth of precision-medicine research in pancreatic ductal adenocarcinoma (PDAC), the main type of pancreatic cancer. In fact, the stalled progress in precision therapies for this type of cancer is due to the absence of agents that are able to target the common genetic alterations in PDAC. Several studies have attempted to phenotypically stratify PDAC at the transcriptional level. However, the value of such classifications will only be revealed through prospective studies and, crucially, only after development of new treatment options for this disease. Therefore, it is essential to learn from breakthrough discoveries in other cancer types that could benefit subpopulations of patients with PDAC and convert them from ordinary to exceptional responders. Identifying these exceptional patients will help to bring PDAC in line with other cancer types in terms of availability of precision therapies. Thus, the true challenge to precision medicine for PDAC might be the poor consensus on which genetic and phenotypic alterations across the spectrum of this disease are actionable; not the absence of actionable variables themselves. To reach consensus, knowledge and tools must be developed and disseminated for individuals who provide pancreatic cancer care, to enable the real-time identification of exceptional patients, more precise subgroup classifications, and effective disease management strategies; all informed by immediate feedback from clinical outcome data.

Signaling in the microenvironment of pancreatic cancer: Transmitting along the nerve

Pancreatic ductal adenocarcinoma (PDA) is a dismal malignant disease with the lowest stage-combined overall survival rate compared to any other cancer type. PDA has a unique tumor microenvironment (TME) comprised of a dense desmoplastic reaction comprising over two-thirds of the total tumor volume. The TME is comprised of cellular and acellular components that all orchestrate different signaling mechanisms together to promote tumorigenesis and disease progression. Particularly, the neural portion of the TME has recently been appreciated in PDA progression. Neural remodeling and perineural invasion (PNI), the neoplastic invasion of tumor cells into nerves, are common adverse histological characteristics of PDA associated with a worsened prognosis and increased cancer aggressiveness. The TME undergoes dramatic neural hypertrophy and increased neural density that is associated with many signaling pathways to promote cell invasion. PNI is also considered one of the main routes for cancer recurrence and metastasis after surgical resection, which remains the only current cure for PDA. Recent studies have shown multiple cell types in the TME signal through autocrine and paracrine mechanisms to enhance perineural invasion, pancreatic neural remodeling and disease progression in PDA. This review summarizes the current findings of the signaling mechanisms and cellular and molecular players involved in neural signaling in the TME of PDA.

ARHGAP4 mediates the Warburg effect in pancreatic cancer through the mTOR and HIF-1α signaling pathways

Objective

The phenomenon that cancer cells avidly exhibit glycolysis with lactate secretion and decrease in mitochondrial activity under aerobic conditions is known historically as the Warburg effect. Rho GTPase-activating protein 4 (ARHGAP4) is an important negative regulator of the Rho signaling pathway that was associated with the tumorigenesis. Our study aims to determine the function of ARHGAP4 in controlling the glycolytic process of pancreatic cancer in vitro and possible molecular mechanism involved.

Methods

ARHGAP4 and PKM2 expressions in pancreatic cancer tissues were measured by immunohistochemistry. Human pancreatic cancer cells transfected with ARHGAP4 expressing lentivirus or siRNA were treated with either mTOR inhibitor (Rapamycin) or HIF-1α inhibitor (YC-1), and the effects were analyzed on cell viability, glucose uptake, lactate release, and the levels of ARHGAP4, p-mTOR, mTOR, PKM2, and HIF-1α expression.

Results

Our findings showed that ARHGAP4 and PKM2 expressions were, respectively, down-regulated and up-regulated in pancreatic cancer tissues. Overexpression of ARHGAP4 significantly inhibited cell viability, glucose uptake, lactate release, PKM2 expression, and activation of mTOR and HIF-1α signaling pathways in pancreatic cancer cells while ARHGAP4 silencing and treatment of Rapamycin or YC-1 showed inverse effects. Additionally, ARHGAP4 downregulation induced cell morphology of pancreatic cancer was inhibited by Rapamycin or YC-1 treatment.

Conclusion

These findings suggest that mTOR and HIF-1α signaling pathways can regulate the ARHGAP4-mediated glycolytic process of pancreatic cancer.

Dissecting the Stromal Signaling and Regulation of Myeloid Cells and Memory Effector T Cells in Pancreatic Cancer

PURPOSE

Myeloid cells are a prominent immunosuppressive component within the stroma of pancreatic ductal adenocarcinoma (PDAC). Previously, targeting myeloid cells has had limited success. Here, we sought to target the myeloid cells through modifying a specific stromal component.

EXPERIMENTAL DESIGN

A murine model of metastatic PDAC treated with an irradiated whole-cell PDAC vaccine and PDAC specimens from patients treated with the same type of vaccine were used to assess the immune-modulating effect of stromal hyaluronan (HA) degradation by PEGPH20.

RESULTS

Targeting stroma by degrading HA with PEGPH20 in combination with vaccine decreases CXCL12/CXCR4/CCR7 immunosuppressive signaling axis expression in cancer-associated fibroblasts, myeloid, and CD8⁺ T cells, respectively. This corresponds with increased CCR7^- effector memory T-cell infiltration, an increase in tumor-specific IFNγ, and improved survival. In the stroma of human PDACs treated with the same vaccine, decreased stromal CXCR4 expression significantly correlated with decreased HA and increased cytotoxic activities, suggesting CXCR4 is an important therapeutic target.

CONCLUSIONS

This study represents the first to dissect signaling cascades following PDAC stroma remodeling via HA depletion, suggesting this not only overcomes a physical barrier for immune cell trafficking, but alters myeloid function leading to downstream selective increases in effector memory T-cell infiltration and antitumor activity.

Anti-pancreatic tumor efficacy of a Listeria-based, Annexin A2-targeting immunotherapy in combination with anti-PD-1 antibodies

BACKGROUND

Immune checkpoint inhibitors are not effective for pancreatic ductal adenocarcinoma (PDAC) as single agents. Vaccine therapy may sensitize PDACs to checkpoint inhibitor treatments. Annexin A2 (ANXA2) is a pro-metastasis protein, previously identified as a relevant PDAC antigen that is expressed by a GM-CSF-secreting allogenic whole pancreatic tumor cell vaccine (GVAX) to induce an anti-ANXA2 antibody response in patients with PDAC. We hypothesized that an ANXA2-targeting vaccine approach not only provokes an immune response but also mounts anti-tumor effects.

METHODS

We developed a Listeria-based, ANXA2-targeting cancer immunotherapy (Lm-ANXA2) and investigated its effectiveness within two murine models of PDAC.

RESULTS

We show that Lm-ANXA2 prolonged the survival in a transplant model of mouse PDACs. More importantly, priming with the Lm-ANXA2 treatment prior to administration of anti-PD-1 antibodies increased cure rates in the implanted PDAC model and resulted in objective tumor responses and prolonged survival in the genetically engineered spontaneous PDAC model. In tumors treated with Lm-ANXA2 followed by anti-PD-1 antibody, the T cells specific to ANXA2 had significantly increased INFγ expression.

CONCLUSIONS

For the first time, a listeria vaccine-based immunotherapy was shown to be able to induce a tumor antigen-specific T cell response within the tumor microenvironment of a "cold" tumor such as PDAC and sensitize the tumor to checkpoint inhibitor therapy. Moreover, this combination immunotherapy led to objective tumor responses and survival benefit in the mice with spontaneously developed PDAC tumors. Therefore, our study supports developing Lm-ANXA2 as a therapeutic agent in combination with anti-PD-1 antibody for PDAC treatment.

Role of c-MET Inhibitors in Overcoming Drug Resistance in Spheroid Models of Primary Human Pancreatic Cancer and Stellate Cells

Pancreatic stellate cells (PSCs) are a key component of tumor microenvironment in pancreatic ductal adenocarcinoma (PDAC) and contribute to drug resistance. c-MET receptor tyrosine kinase activation plays an important role in tumorigenesis in different cancers including PDAC. In this study, effects of PSC conditioned medium (PCM) on c-MET phosphorylation (by immunocytochemistry enzyme-linked immunosorbent assay (ELISA)) and drug response (by sulforhodamine B assay) were investigated in five primary PDAC cells. In novel 3D-spheroid co-cultures of cyan fluorescence protein (CFP)-firefly luciferase (Fluc)-expressing primary human PDAC cells and green fluorescence protein (GFP)-expressing immortalized PSCs, PDAC cell growth and chemosensitivity were examined by luciferase assay, while spheroids' architecture was evaluated by confocal microscopy. The highest phospho-c-MET expression was detected in PDAC5 and its subclone sorted for "stage specific embryonic antigen-4" (PDAC5 (SSEA4)). PCM of cells pre-incubated with PDAC conditioned medium, containing increased hepatocyte growth factor (HGF) levels, made PDAC cells significantly more resistant to gemcitabine, but not to c-MET inhibitors. Hetero-spheroids containing both PSCs and PDAC5 (SSEA4) cells were more resistant to gemcitabine compared to PDAC5 (SSEA4) homo-spheroids. However, c-MET inhibitors (tivantinib, PHA-665752 and crizotinib) were equally effective in both spheroid models. Experiments with primary human PSCs confirmed the main findings. In conclusion, we developed spheroid models to evaluate PSC-PDAC reciprocal interaction, unraveling c-MET inhibition as an important therapeutic option against drug resistant PDAC.

Sonic Hedgehog Ligand: A Role in Formation of a Mesenchymal Niche in Human Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is characterised by desmoplasia, thought to support progression and chemotherapeutic resistance. The Hedgehog pathway is known to play an important role in this cancer. While the upregulation of Sonic hedgehog (Shh) in the epithelium of PDAC is known, we investigated its expression in the tumour microenvironment in order to find new targets for new chemotherapeutical approaches. Immunohistochemistry was used for the investigation of Shh and Vimentin in primary human pancreatic tissues. Gene (qRT-PCR) and protein (immunofluorescence) expression of Shh, αSMA (a marker of the mesenchymal phenotype) and periostin (a marker of mesenchymal cells within a mixed population) were investigated in in vitro cell models. Shh expression was significantly upregulated in the stromal and epithelial compartments of poorly-differentiated PDAC samples, with a strong correlation with the amount of stroma present. Characterisation of stromal cells showed that there was expression of Shh ligand in a mixed population comprising αSMA+ myofibroblasts and αSMA- mesenchymal stem cells. Moreover, we demonstrated the interaction between these cell lines by showing a higher rate of mesenchymal cell proliferation and the upregulation of periostin. Therefore, targeting stromal Shh could affect the equilibrium of the tumour microenvironment and its contribution to tumour growth.

Genomic testing, tumor microenvironment and targeted therapy of Hedgehog-related human cancers

Hedgehog signals are transduced through Patched receptors to the Smoothened (SMO)-SUFU-GLI and SMO-Gi-RhoA signaling cascades. MTOR-S6K1 and MEK-ERK signals are also transduced to GLI activators through post-translational modifications. The GLI transcription network up-regulates target genes, such as BCL2, FOXA2, FOXE1, FOXF1, FOXL1, FOXM1, GLI1, HHIP, PTCH1 and WNT2B, in a cellular context-dependent manner. Aberrant Hedgehog signaling in tumor cells leads to self-renewal, survival, proliferation and invasion. Paracrine Hedgehog signaling in the tumor microenvironment (TME), which harbors cancer-associated fibroblasts, leads to angiogenesis, fibrosis, immune evasion and neuropathic pain. Hedgehog-related genetic alterations occur frequently in basal cell carcinoma (BCC) (85%) and Sonic Hedgehog (SHH)-subgroup medulloblastoma (87%) and less frequently in breast cancer, colorectal cancer, gastric cancer, pancreatic cancer, non-small-cell lung cancer (NSCLC) and ovarian cancer. Among investigational SMO inhibitors, vismodegib and sonidegib are approved for the treatment of patients with BCC, and glasdegib is approved for the treatment of patients with acute myeloid leukemia (AML). Resistance to SMO inhibitors is caused by acquired SMO mutations, SUFU deletions, GLI2 amplification, other by-passing mechanisms of GLI activation and WNT/β-catenin signaling activation. GLI-DNA-interaction inhibitors (glabrescione B and GANT61), GLI2 destabilizers (arsenic trioxide and pirfenidone) and a GLI-deacetylation inhibitor (4SC-202) were shown to block GLI-dependent transcription and tumorigenesis in preclinical studies. By contrast, SMO inhibitors can remodel the immunosuppressive TME that is dominated by M2-like tumor-associated macrophages (M2-TAMs), myeloid-derived suppressor cells and regulatory T cells, and thus, a Phase I/II clinical trial of the immune checkpoint inhibitor pembrolizumab with or without vismodegib in BCC patients is ongoing.

IDO1 inhibition potentiates vaccine-induced immunity against pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) represents an immune quiescent tumor that is resistant to immune checkpoint inhibitors. Previously, our group has shown that a GM-CSF-secreting allogenic pancreatic tumor cell vaccine (GVAX) may prime the tumor microenvironment by inducing intratumoral T cell infiltration. Here, we show that untreated PDACs express minimal indoleamine-2,3-dioxygenase (IDO1); however, GVAX therapy induced IDO1 expression on tumor epithelia as well as vaccine-induced tertiary lymphoid aggregates. IDO1 expression plays a role in regulating the polarization of Th1, Th17, and possibly T regulatory cells in PDAC tumors. IDO1 inhibitor enhanced antitumor efficacy of GVAX in a murine model of PDACs. The combination of vaccine and IDO1 inhibitor enhanced intratumoral T cell infiltration and function, but adding anti-PD-L1 antibody to the combination did not offer further synergy and in fact may have had a negative interaction, decreasing the number of intratumoral effector T cells. Additionally, IDO1 inhibitor in the presence of vaccine therapy did not significantly modulate intratumoral myeloid-derived suppressor cells quantitatively, but diminished their suppressive effect on CD8+ proliferation. Our study supports the combination of IDO1 inhibitor and vaccine therapy; however, it does not support the combination of IDO1 inhibitor and anti-PD-1/PD-L1 antibody for T cell-inflamed tumors such as PDACs treated with vaccine therapy.

Identification and Characterization of AES-135, a Hydroxamic Acid-Based HDAC Inhibitor That Prolongs Survival in an Orthotopic Mouse Model of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive, incurable cancer with a 20% 1 year survival rate. While standard-of-care therapy can prolong life in a small fraction of cases, PDAC is inherently resistant to current treatments, and novel therapies are urgently required. Histone deacetylase (HDAC) inhibitors are effective in killing pancreatic cancer cells in in vitro PDAC studies, and although there are a few clinical studies investigating combination therapy including HDAC inhibitors, no HDAC drug or combination therapy with an HDAC drug has been approved for the treatment of PDAC. We developed an inhibitor of HDACs, AES-135, that exhibits nanomolar inhibitory activity against HDAC3, HDAC6, and HDAC11 in biochemical assays. In a three-dimensional coculture model, AES-135 kills low-passage patient-derived tumor spheroids selectively over surrounding cancer-associated fibroblasts and has excellent pharmacokinetic properties in vivo. In an orthotopic murine model of pancreatic cancer, AES-135 prolongs survival significantly, therefore representing a candidate for further preclinical testing.

Activation of IGF/IGF-IR signaling pathway fails to induce epithelial-mesenchymal transition in pancreatic cancer cells

BACKGROUND

Pancreatic cancer stromal cells produce various protein factors, which presumably provide cancer cells with drug resistance and may influence their ability to form metastasis via induction of epithelial-mesenchymal transition (ЕМТ). The goal of our project was to study the effects of IGF-I on expression of protein markers of epithelial and mesenchymal differentiation, and on expression of transcriptional regulators of EMT in pancreatic cancer cell lines.

METHODS

We used Western blot analysis to study the expression patterns of epithelial and mesenchymal protein markers in pancreatic cancer cell lines, which have been stimulated with IGF-I for various periods of time. The ELISA technique was employed to determine the concentration of IGF-I in conditioned media. Additionally, the effect of IGF-I on proliferation of pancreatic cancer cells was measured via MTS technique.

RESULTS

We investigated the effect of IGF/IGF-IR signaling pathway activation on expression levels of cell differentiation markers in five pancreatic cancer cell lines (AsPC-1, BxPC-3, Capan-2, MiaPaCa-2 and Panc1). The IGF-I stimulation led to phosphorylation of IGF-IR and activation of PI-3K/Akt signaling cascade. At the same time our results reveal that the activation of IGF/IGF-IR signaling pathway in pancreatic cancer cells does not induce a significant shift in cell phenotype towards mesenchymal differentiation and does not induce a decrease in expression levels of epithelial protein markers.

CONCLUSIONS

Our results demonstrate that IGF-I does not function as an effective inductor of EMT in pancreatic cancer cell lines and that stimulation of IGF-I/IGF-IR signaling pathway does not lead to EMT associated changes in cell differentiation.

Dbx2 exhibits a tumor-promoting function in hepatocellular carcinoma cell lines via regulating Shh-Gli1 signaling

BACKGROUND

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide. HCC patients suffer from a high mortality-to-incidence ratio and low cure rate since we still have no specific and effective treatment. Although tremendous advances have been made in the investigation of HCC, the specific mechanisms of the progression of this disease are still only partially established. Hence, more research is needed to elucidate the underlying potential mechanisms to develop effective strategies for HCC.

AIM

To determine the role of developing brain homeobox 2 (Dbx2) gene in promoting the development of HCC.

METHODS

Dbx2 expression in clinical specimens and HCC cell lines was detected by Western blot (WB) and immunohistochemistry. Gain and loss of Dbx2 function assays were performed in vitro and in vivo. Cell viability assays were used to investigate cell growth, flow cytometry was employed to assess cell cycle and apoptosis, and trans-well assays were conducted to evaluate cell migration, invasion, and metastasis. The expression of key molecules in the sonic hedgehog (Shh) signaling was determined by WB.

RESULTS

Compared to matched adjacent non-tumorous tissues, Dbx2 was overexpressed in 5 HCC cell lines and 76 surgically resected HCC tissues. Dbx2 overexpression was correlated with large tumor size. Both gain and loss of function assays indicated that Dbx2 promoted HCC cell proliferation by facilitating the transition from G1 to S phase, attenuating apoptosis and promoted HCC proliferation, migration, and invasion in vitro and in vivo. Mechanistically, Dbx2 modulated Shh signaling by enhancing FTCH1 and GLi1 expression in HCC cells that overexpressed Dbx2, which was reversed in HCC cells with Dbx2 knockdown.

CONCLUSION

Our results indicate that Dbx2 is significantly upregulated in HCC tissues and plays significant roles in proliferation and metastasis of HCC cells by activating the Shh pathway.

MET/HGF Co-Targeting in Pancreatic Cancer: A Tool to Provide Insight into the Tumor/Stroma Crosstalk

The ‘onco-receptor’ MET (Hepatocyte Growth Factor Receptor) is involved in the activation of the invasive growth program that is essential during embryonic development and critical for wound healing and organ regeneration during adult life. When aberrantly activated, MET and its stroma-secreted ligand HGF (Hepatocyte Growth Factor) concur to tumor onset, progression, and metastasis in solid tumors, thus representing a relevant target for cancer precision medicine. In the vast majority of tumors, wild-type MET behaves as a ‘stress-response’ gene, and relies on ligand stimulation to sustain cancer cell ‘scattering’, invasion, and protection form apoptosis. Moreover, the MET/HGF axis is involved in the crosstalk between cancer cells and the surrounding microenvironment. Pancreatic cancer (namely, pancreatic ductal adenocarcinoma, PDAC) is an aggressive malignancy characterized by an abundant stromal compartment that is associated with early metastases and resistance to conventional and targeted therapies. Here, we discuss the role of the MET/HGF axis in tumor progression and dissemination considering as a model pancreatic cancer, and provide a proof of concept for the application of dual MET/HGF inhibition as an adjuvant therapy in pancreatic cancer patients.

The impact of cancer-associated fibroblasts on major hallmarks of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) constitutes one of the most challenging lethal tumors and has a very poor prognosis. In addition to cancer cells, the tumor microenvironment created by a repertoire of resident and recruited cells and the extracellular matrix also contribute to the acquisition of hallmarks of cancer. Among these factors, cancer-associated fibroblasts (CAFs) are critical components of the tumor microenvironment. CAFs originate from the activation of resident fibroblasts and pancreatic stellate cells, the differentiation of bone marrow-derived mesenchymal stem cells and epithelial-to-mesenchymal transition. CAFs acquire an activated phenotype via various cytokines and promote tumor proliferation and growth, accelerate invasion and metastasis, induce angiogenesis, promote inflammation and immune destruction, regulate tumor metabolism, and induce chemoresistance; these factors contribute to the acquisition of major hallmarks of PDAC. Therefore, an improved understanding of the impact of CAFs on the major hallmarks of PDAC will highlight the diagnostic and therapeutic values of these targeted cells.

Widespread Expression of Hedgehog Pathway Components in a Large Panel of Human Tumor Cells and Inhibition of Tumor Growth by GANT61: Implications for Cancer Therapy

The sonic Hedgehog/GLI signaling pathway (HH) is critical for maintaining tissue polarity in development and contributes to tumor stemness. Transcription factors GLI1–3 are the downstream effectors of HH and activate oncogenic targets. To explore the completeness of the expression of HH components in tumor cells, we performed a screen for all HH proteins in a wide spectrum of 56 tumor cell lines of various origin using Western blot analysis. Generally, all HH proteins were expressed. Important factors GLI1 and GLI2 were always expressed, only exceptionally one of them was lowered, suggesting the functionality of HH in all tumors tested. We determined the effect of a GLI inhibitor GANT61 on proliferation in 16 chosen cell lines. More than half of tumor cells were sensitive to GANT61 to various extents. GANT61 killed the sensitive cells through apoptosis. The inhibition of reporter activity containing 12xGLI consensus sites by GANT61 and cyclopamine roughly correlated with cell proliferation influenced by GANT61. Our results recognize the sensitivity of tumor cell types to GANT61 in cell culture and support a critical role for GLI factors in tumor progression through restraining apoptosis. The use of GANT61 in combined targeted therapy of sensitive tumors, such as melanomas, seems to be immensely helpful.