Enhanced expression of transforming growth factor beta isoforms in pancreatic cancer correlates with decreased survival

TGF-β signaling: critical nexus of fibrogenesis and cancer

The transforming growth factor-beta (TGF-β) signaling pathway is a vital regulator of cell proliferation, differentiation, apoptosis, and extracellular matrix production. It functions through canonical SMAD-mediated processes and noncanonical pathways involving MAPK cascades, PI3K/AKT, Rho-like GTPases, and NF-κB signaling. This intricate signaling system is finely tuned by interactions between canonical and noncanonical pathways and plays key roles in both physiologic and pathologic conditions including tissue homeostasis, fibrosis, and cancer progression. TGF-β signaling is known to have paradoxical actions. Under normal physiologic conditions, TGF-β signaling promotes cell quiescence and apoptosis, acting as a tumor suppressor. In contrast, in pathological states such as inflammation and cancer, it triggers processes that facilitate cancer progression and tissue remodeling, thus promoting tumor development and fibrosis. Here, we detail the role that TGF-β plays in cancer and fibrosis and highlight the potential for future theranostics targeting this pathway.

N6-methyladenosine modified TGFB2 triggers lipid metabolism reprogramming to confer pancreatic ductal adenocarcinoma gemcitabine resistance

Gemcitabine resistance is a major obstacle to the effectiveness of chemotherapy in pancreatic ductal adenocarcinoma (PDAC). Therefore, new strategies are needed to sensitize cancer cells to gemcitabine. Here, we constructed gemcitabine-resistant PDAC cells and analyzed them with RNA-sequence. Employing an integrated approach involving bioinformatic analyses from multiple databases, TGFB2 is identified as a crucial gene in gemcitabine-resistant PDAC and is significantly associated with poor gemcitabine therapeutic response. The patient-derived xenograft (PDX) model further substantiates the gradual upregulation of TGFB2 expression during gemcitabine-induced resistance. Silencing TGFB2 expression can enhance the chemosensitivity of gemcitabine against PDAC. Mechanistically, TGFB2, post-transcriptionally stabilized by METTL14-mediated m6A modification, can promote lipid accumulation and the enhanced triglyceride accumulation drives gemcitabine resistance by lipidomic profiling. TGFB2 upregulates the lipogenesis regulator sterol regulatory element binding factor 1 (SREBF1) and its downstream lipogenic enzymes via PI3K-AKT signaling. Moreover, SREBF1 is responsible for TGFB2-mediated lipogenesis to promote gemcitabine resistance in PDAC. Importantly, TGFB2 inhibitor imperatorin combined with gemcitabine shows synergistic effects in gemcitabine-resistant PDAC PDX model. This study sheds new light on an avenue to mitigate PDAC gemcitabine resistance by targeting TGFB2 and lipid metabolism and develops the potential of imperatorin as a promising chemosensitizer in clinical translation.

TGF-β signaling in health, disease, and therapeutics

Transforming growth factor (TGF)-β is a multifunctional cytokine expressed by almost every tissue and cell type. The signal transduction of TGF-β can stimulate diverse cellular responses and is particularly critical to embryonic development, wound healing, tissue homeostasis, and immune homeostasis in health. The dysfunction of TGF-β can play key roles in many diseases, and numerous targeted therapies have been developed to rectify its pathogenic activity. In the past decades, a large number of studies on TGF-β signaling have been carried out, covering a broad spectrum of topics in health, disease, and therapeutics. Thus, a comprehensive overview of TGF-β signaling is required for a general picture of the studies in this field. In this review, we retrace the research history of TGF-β and introduce the molecular mechanisms regarding its biosynthesis, activation, and signal transduction. We also provide deep insights into the functions of TGF-β signaling in physiological conditions as well as in pathological processes. TGF-β-targeting therapies which have brought fresh hope to the treatment of relevant diseases are highlighted. Through the summary of previous knowledge and recent updates, this review aims to provide a systematic understanding of TGF-β signaling and to attract more attention and interest to this research area.

KMT2D links TGF-β signaling to noncanonical activin pathway and regulates pancreatic cancer cell plasticity

Although KMT2D, also known as MLL2, is known to play an essential role in development, differentiation, and tumor suppression, its role in pancreatic cancer development is not well understood. Here, we discovered a novel signaling axis mediated by KMT2D, which links TGF-β to the activin A pathway. We found that TGF-β upregulates a microRNA, miR-147b, which in turn leads to post-transcriptional silencing of KMT2D. Loss of KMT2D induces the expression and secretion of activin A, which activates a noncanonical p38 MAPK-mediated pathway to modulate cancer cell plasticity, promote a mesenchymal phenotype, and enhance tumor invasion and metastasis in mice. We observed a decreased KMT2D expression in human primary and metastatic pancreatic cancer. Furthermore, inhibition or knockdown of activin A reversed the protumoral role of KMT2D loss. These findings support a tumor-suppressive role of KMT2D in pancreatic cancer and identify miR-147b and activin A as novel therapeutic targets.

Antagonism between Prdm16 and Smad4 specifies the trajectory and progression of pancreatic cancer

The transcription factor Prdm16 functions as a potent suppressor of transforming growth factor-beta (TGF-β) signaling, whose inactivation is deemed essential to the progression of pancreatic ductal adenocarcinoma (PDAC). Using the KrasG12D-based mouse model of human PDAC, we surprisingly found that ablating Prdm16 did not block but instead accelerated PDAC formation and progression, suggesting that Prdm16 might function as a tumor suppressor in this malignancy. Subsequent genetic experiments showed that ablating Prdm16 along with Smad4 resulted in a shift from a well-differentiated and confined neoplasm to a highly aggressive and metastatic disease, which was associated with a striking deviation in the trajectory of the premalignant lesions. Mechanistically, we found that Smad4 interacted with and recruited Prdm16 to repress its own expression, therefore pinpointing a model in which Prdm16 functions downstream of Smad4 to constrain the PDAC malignant phenotype. Collectively, these findings unveil an unprecedented antagonistic interaction between the tumor suppressors Smad4 and Prdm16 that functions to restrict PDAC progression and metastasis.

Pre-existing TGF-β-specific T-cell immunity in patients with pancreatic cancer predicts survival after checkpoint inhibitors combined with radiotherapy

BACKGROUND

Circulating transforming growth factor-β (TGF-β)-specific T cells that recognize TGF-β-expressing immune regulatory cells have been described in patients with cancer. TGF-β-derived peptide vaccination modulates the tumor microenvironment and has shown clinical effects in animal models of pancreatic cancer (PC). TGF-β-expressing regulatory cells are especially elevated in PC and may prevent the clinical response to immune checkpoint inhibitors (ICIs). Thus, in the present study we investigated the significance of TGF-β-specific T-cell immunity in patients with PC treated with ICI combined with radiotherapy in a randomized phase 2 study (CheckPAC).

METHODS

Immune responses to a TGF-β-derived epitope entitled TGF-β-15 as well as epitopes from Clostridium tetani (tetanus) and influenza were measured in peripheral blood mononuclear cells (PBMCs) with interferon-ɣ enzyme-linked immunospot assays. PBMCs were isolated before and after treatment. Correlations between immune response data and clinical data were evaluated with parametric and non-parametric statistical methods. Survival was analyzed with univariate and multivariate Cox-regression. TGF-β-15 specific T cells were isolated and expanded and examined for recognition of autologous regulatory immune cells by flow cytometry.

RESULTS

PBMCs from 32 patients were analyzed for immune responses to the TGF-β-derived epitope entitled TGF-β-15. Patients with a strong TGF-β-specific immune response at treatment initiation had longer progression-free and overall survival, compared with patients with a weak or no TGF-β-specific immune response. This remained significant in multivariate analysis. Patients with weak and strong TGF-β-specific responses displayed similar responses towards viral antigens. Furthermore, we show that TGF-β-specific T cells from a clinical responder specifically reacted to and lysed autologous, regulatory immune cells. Finally, mimicking a TGF-β-15 vaccination, we showed that repeated stimulations with the TGF-β-15 epitope in vitro enhanced the immune response to TGF-β-15.

CONCLUSION

A strong TGF-β-15 specific immune response was associated with clinical benefit and improved survival after ICI/radiotherapy for patients with PC. Importantly, the lack of TGF-β-specific T cells in some patients was not caused by a general immune dysfunction. TGF-β-specific T cells recognized regulatory immune cells and could be introduced in vitro in patients without spontaneous responses. Taken together, our data suggest that combining TGF-β-based vaccination with ICI/radiotherapy will be beneficial for patients with PC.

Stroma-targeting strategies in pancreatic cancer: a double-edged sword

Pancreatic ductal adenocarcinoma (PDAC) is a type of cancer with limited treatment options and terrible long-term survival, and it is expected to become the second leading cause of cancer-related death by 2030. One reason why this cancer is so aggressive and resistant is the formation of dense stroma that surrounds the neoplastic epithelium, which promotes tumor progression, invasion, metastasis, and resistance. The three major components of PDAC stroma are extracellular matrix (ECM), cancer-associated fibroblasts (CAFs), and vasculature. The dense ECM acts as a natural physical barrier, impeding drug penetration to PDAC tumor cells. Consequently, the method that combines stroma-targeting with anticancer therapy may be a viable alternative for increasing drug penetration. Additionally, blood vessels are key entities of the tumor stroma, serving as a pathway for nutrition as well as the only way for chemical medicines and immune cells to act. Finally, PDAC CAFs and tumor cells have crosstalk effects in the tumor microenvironment, where they are responsible for enhanced matrix deposition. In this review, we aim to provide an overview of our current comprehension of the three key components of PDAC stroma and the new promising therapeutic targets for PDAC.

Therapeutic Potential of Targeting Transforming Growth Factor-beta (TGF-β) and Programmed Death-ligand 1 (PD-L1) in Pancreatic Cancer

Pancreatic cancer (PC) is one the most lethal malignancies worldwide affecting around half a million individuals each year. The treatment of PC is relatively difficult due to the difficulty in making an early diagnosis. Transforming growth factor-beta (TGF-β) is a multifunctional factor acting as both a tumor promoter in early cancer stages and a tumor suppressor in advanced disease. Programmed death-ligand 1 (PD-L1) is a ligand of programmed death-1 (PD-1), an immune checkpoint receptor, allowing tumor cells to avoid elimination by immune cells. Recently, targeting the TGF-β signaling and PD-L1 pathways has emerged as a strategy for cancer therapy. In this review, we have summarized the current knowledge regarding these pathways and their contribution to tumor development with a focus on PC. Moreover, we have reviewed the role of TGF-β and PD-L1 blockade in the treatment of various cancer types, including PC, and discussed the clinical trials evaluating TGF-β and PD-L1 antagonists in PC patients.

Combination immunotherapy for pancreatic cancer: challenges and future considerations

INTRODUCTION

: Immune checkpoint inhibitors (ICI) have not yielded significant efficacy in pancreatic ductal adenocarcinoma (PDA), despite the role of the innate and adaptive immune systems on progression and survival. However, recently identified pathways have identified new targets and generated promising clinical investigations into promoting an effective immune-mediated antitumor response in PDA.

AREAS COVERED

: We review biological mechanisms associated with immunotherapy resistance and outline strategies for therapeutic combinations with established and novel therapies in PDA.

EXPERT OPINION

: Pancreatic cancers rarely benefits from treatment with ICI due to an immunosuppressive tumor microenvironment (TME). New understandings of factors associated with the suppressive TME, include low and poor quality neoantigens, constrained effector T cells infiltration, and the presence of a dense, suppressive myeloid cell population. These findings have been translated into new clinical investigations evaluating novel therapies in combination with ICI and/or standard systemic chemotherapy and radiotherapy. The epithelial, immune, and stromal compartments are intricately related in PDA, and the framework for successful targeting of this disease requires a comprehensive and personalized approach.

An Extensive Review on Preclinical and Clinical Trials of Oncolytic Viruses Therapy for Pancreatic Cancer

Chemotherapy resistance and peculiar tumor microenvironment, which diminish or mitigate the effects of therapies, make pancreatic cancer one of the deadliest malignancies to manage and treat. Advanced immunotherapies are under consideration intending to ameliorate the overall patient survival rate in pancreatic cancer. Oncolytic viruses therapy is a new type of immunotherapy in which a virus after infecting and lysis the cancer cell induces/activates patients’ immune response by releasing tumor antigen in the blood. The current review covers the pathways and molecular ablation that take place in pancreatic cancer cells. It also unfolds the extensive preclinical and clinical trial studies of oncolytic viruses performed and/or undergoing to design an efficacious therapy against pancreatic cancer.

Local Release of TGF-β Inhibitor Modulates Tumor-Associated Neutrophils and Enhances Pancreatic Cancer Response to Combined Irreversible Electroporation and Immunotherapy

Pancreatic cancer is a deadly disease with little response to standard therapies. Irreversible electroporation (IRE) has emerged as a novel ablative technique for the clinical treatment of pancreatic cancer. Combinations of IRE and immunotherapies, including anti-programmed death 1 (αPD1) immune checkpoint blockade, have shown promising efficacy in both preclinical and clinical studies. However, tumor recurrence remains an obstacle that needs to be overcome. It herein is shown that IRE induces a substantial infiltration of neutrophils into pancreatic tumors. These neutrophils are then polarized into a protumor phenotype by immunosuppressive cues, in particular transforming growth factor β (TGF-β). Using glutathione-responsive degradable mesoporous silica nanoparticles loaded with SB525334, an inhibitor of TGF-β1 receptor, it is demonstrated that local inhibition of TGF-β within the tumor microenvironment promotes neutrophil polarization into an antitumor phenotype, enhances pancreatic cancer response to combined IRE and αPD1 therapy, and induces long-term antitumor memory. The therapeutic efficacy is also attributed to tumor infiltration by CD8⁺ cytotoxic T cells, depletion of regulatory T cells, and maturation of antigen-presenting dendritic cells. Thus, modulating neutrophil polarization with nanomedicine is a promising strategy for treating pancreatic cancer.

Molecular signaling in pancreatic ductal metaplasia: emerging biomarkers for detection and intervention of early pancreatic cancer

Pancreatic ductal metaplasia (PDM) is the transformation of potentially various types of cells in the pancreas into ductal or ductal-like cells, which eventually replace the existing differentiated somatic cell type(s). PDM is usually triggered by and manifests its ability to adapt to environmental stimuli and genetic insults. The development of PDM to atypical hyperplasia or dysplasia is an important risk factor for pancreatic intraepithelial neoplasia (PanIN) and pancreatic ductal adenocarcinoma (PDA). Recent studies using genetically engineered mouse models, cell lineage tracing, single-cell sequencing and others have unraveled novel cellular and molecular insights in PDM formation and evolution. Those novel findings help better understand the cellular origins and functional significance of PDM and its regulation at cellular and molecular levels. Given that PDM represents the earliest pathological changes in PDA initiation and development, translational studies are beginning to define PDM-associated cell and molecular biomarkers that can be used to screen and detect early PDA and to enable its effective intervention, thereby truly and significantly reducing the dreadful mortality rate of PDA. This review will describe recent advances in the understanding of PDM biology with a focus on its underlying cellular and molecular mechanisms, and in biomarker discovery with clinical implications for the management of pancreatic regeneration and tumorigenesis.

Correlation between Oxidative Stress and Transforming Growth Factor-Beta in Cancers

The downregulation of reactive oxygen species (ROS) facilitates precancerous tumor development, even though increasing the level of ROS can promote metastasis. The transforming growth factor-beta (TGF-β) signaling pathway plays an anti-tumorigenic role in the initial stages of cancer development but a pro-tumorigenic role in later stages that fosters cancer metastasis. TGF-β can regulate the production of ROS unambiguously or downregulate antioxidant systems. ROS can influence TGF-β signaling by enhancing its expression and activation. Thus, TGF-β signaling and ROS might significantly coordinate cellular processes that cancer cells employ to expedite their malignancy. In cancer cells, interplay between oxidative stress and TGF-β is critical for tumorigenesis and cancer progression. Thus, both TGF-β and ROS can develop a robust relationship in cancer cells to augment their malignancy. This review focuses on the appropriate interpretation of this crosstalk between TGF-β and oxidative stress in cancer, exposing new potential approaches in cancer biology.

Oncogenic KRAS-Induced Feedback Inflammatory Signaling in Pancreatic Cancer: An Overview and New Therapeutic Opportunities

Pancreatic ductal adenocarcinoma (PDAC) remains highly refractory to treatment. While the KRAS oncogene is present in almost all PDAC cases and accounts for many of the malignant feats of PDAC, targeting KRAS or its canonical, direct effector cascades remains unsuccessful in patients. The recalcitrant nature of PDAC is also heavily influenced by its highly fibro-inflammatory tumor microenvironment (TME), which comprises an acellular extracellular matrix and various types of non-neoplastic cells including fibroblasts, immune cells, and adipocytes, underscoring the critical need to delineate the bidirectional signaling interplay between PDAC cells and the TME in order to develop novel therapeutic strategies. The impact of tumor-cell KRAS signaling on various cell types in the TME has been well covered by several reviews. In this article, we critically reviewed evidence, including work from our group, on how the feedback inflammatory signals from the TME impact and synergize with oncogenic KRAS signaling in PDAC cells, ultimately augmenting their malignant behavior. We discussed past and ongoing clinical trials that target key inflammatory pathways in PDAC and highlight lessons to be learned from outcomes. Lastly, we provided our perspective on the future of developing therapeutic strategies for PDAC through understanding the breadth and complexity of KRAS and the inflammatory signaling network.

TGFβ Signaling in the Pancreatic Tumor Microenvironment

Pancreatic ductal adenocarcinoma (PDAC) is associated with poor clinical outcomes, largely attributed to incomplete responses to standard therapeutic approaches. Recently, selective inhibitors of the Transforming Growth Factor β (TGFβ) signaling pathway have shown early promise in the treatment of PDAC, particularly as a means of augmenting responses to chemo- and immunotherapies. However, TGFβ is a potent and pleiotropic cytokine with several seemingly paradoxical roles within the pancreatic tumor microenvironment (TME). Although TGFβ signaling can have potent tumor-suppressive effects in epithelial cells, TGFβ signaling also accelerates pancreatic tumorigenesis by enhancing epithelial-to-mesenchymal transition (EMT), fibrosis, and the evasion of the cytotoxic immune surveillance program. Here, we discuss the known roles of TGFβ signaling in pancreatic carcinogenesis, the biologic consequences of the genetic inactivation of select components of the TGFβ pathway, as well as past and present attempts to advance TGFβ inhibitors in the treatment of PDAC patients.

Loss of miR-29a/b1 promotes inflammation and fibrosis in acute pancreatitis

MicroRNA-29 (miR-29) is a critical regulator of fibroinflammatory processes in human diseases. In this study, we found a decrease in miR-29a in experimental and human chronic pancreatitis, leading us to investigate the regulatory role of the miR-29a/b1 cluster in acute pancreatitis (AP) utilizing a conditional miR-29a/b1-KO mouse model. miR-29a/b1-sufficient (WT) and -deficient (KO) mice were administered supramaximal caerulein to induce AP and characterized at different time points, utilizing an array of IHC and biochemical analyses for AP parameters. In caerulein-induced WT mice, miR-29a remained dramatically downregulated at injury. Despite high-inflammatory milieu, fibrosis, and parenchymal disarray in the WT mice during early AP, the pancreata fully restored during recovery. miR-29a/b1-KO mice showed significantly greater inflammation, lymphocyte infiltration, macrophage polarization, and ECM deposition, continuing until late recovery with persistent parenchymal disorganization. The increased pancreatic fibrosis was accompanied by enhanced TGFβ1 coupled with persistent αSMA+ PSC activation. Additionally, these mice exhibited higher circulating IL-6 and inflammation in lung parenchyma. Together, this collection of studies indicates that depletion of miR-29a/b1 cluster impacts the fibroinflammatory mechanisms of AP, resulting in (a) aggravated pathogenesis and (b) delayed recovery from the disease, suggesting a protective role of the molecule against AP.

Penetration Cascade of Size Switchable Nanosystem in Desmoplastic Stroma for Improved Pancreatic Cancer Therapy

Pancreatic ductal adenocarcinoma (PDAC) cells are surrounded by a dense extracellular matrix (ECM), which greatly restricts the access of therapeutic agents, resulting in poor clinical response to chemotherapy. Transforming growth factor-β1 (TGF-β1) signaling plays a crucial role in construction of the desmoplastic stroma and provides potential targets for PDAC therapy. To surmount the pathological obstacle, we developed a size switchable nanosystem based on PEG-PLGA nanospheres encapsulated within liposomes for the combined delivery of vactosertib (VAC), a TGF-β1 receptor kinase inhibitor, and the cytotoxic drug paclitaxel (TAX). By surface modification of the liposomes with a peptide, APT_EDB, the nanosystem can be anchored to abundant tumor-associated fibronectin in PDAC stroma and decreases its size by releasing encapsulated TAX-loaded nanospheres, as well as VAC after collapse of the liposomes. The inhibition of ECM hyperplasia by VAC allows TAX more ready access to the cancer cells in addition to its small size, thereby shrinking pancreatic tumor xenografts more effectively than a combination of the free drugs. This size switchable nanosystem enables sequential delivery of drugs at a fixed dose combination with simplified administration and provides an encouraging cascade approach of drug penetration for enhanced chemotherapy in cancers with a dense desmoplastic stroma.

The Multifaceted Role of TGF-β in Gastrointestinal Tumors

Simple Summary

The transforming growth factor β signaling pathway elicits a broad range of physiological re-sponses, and its misregulation has been related to cancer. The secreted cytokine TGFβ exerts a tumor-suppressive effect that counteracts malignant transformation. However, once tumor has developed, TGFβ can support tumor progression regulating epithelial to mesenchymal transition, invasion and metastasis, stimulating fibrosis, angiogenesis and immune suppression. Here we review the dichotomous role of TGF-β in the progression of gastrointestinal tumors, as well as its intricate crosstalk with other signaling pathways. We also discuss about the therapeutic strate-gies that are currently explored in clinical trials to counteract TGF-β functions.

Abstract

Transforming growth factor-beta (TGF-β) is a secreted cytokine that signals via serine/threonine kinase receptors and SMAD effectors. Although TGF-β acts as a tumor suppressor during the early stages of tumorigenesis, it supports tumor progression in advanced stages. Indeed, TGF-β can modulate the tumor microenvironment by modifying the extracellular matrix and by sustaining a paracrine interaction between neighboring cells. Due to its critical role in cancer development and progression, a wide range of molecules targeting the TGF-β signaling pathway are currently under active clinical development in different diseases. Here, we focused on the role of TGF-β in modulating different pathological processes with a particular emphasis on gastrointestinal tumors.

TGF-β Signaling in Liver, Pancreas, and Gastrointestinal Diseases and Cancer

Genetic alterations affecting transforming growth factor-β (TGF-β) signaling are exceptionally common in diseases and cancers of the gastrointestinal system. As a regulator of tissue renewal, TGF-β signaling and the downstream SMAD-dependent transcriptional events play complex roles in the transition from a noncancerous disease state to cancer in the gastrointestinal tract, liver, and pancreas. Furthermore, this pathway also regulates the stromal cells and the immune system, which may contribute to evasion of the tumors from immune-mediated elimination. Here, we review the involvement of the TGF-β pathway mediated by the transcriptional regulators SMADs in disease progression to cancer in the digestive system. The review integrates human genomic studies with animal models that provide clues toward understanding and managing the complexity of the pathway in disease and cancer.

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.

Harnessing Carcinoma Cell Plasticity Mediated by TGF-β Signaling

Simple Summary

This review describes mechanisms driving epithelial plasticity in carcinoma mediated by transforming growth factor beta (TGF-β) signaling. Plasticity in carcinoma is frequently induced through epithelial–mesenchymal transition (EMT), an evolutionary conserved process in the development of multicellular organisms. The review explores the multifaceted functions of EMT, particularly focusing on the intermediate stages, which provide more adaptive responses of carcinoma cells in their microenvironment. The review critically considers how different intermediate or hybrid EMT stages confer carcinoma cells with stemness, refractoriness to therapies, and ability to execute all steps of the metastatic cascade. Finally, the review provides examples of therapeutic interventions based on the EMT concept.

Abstract

Epithelial cell plasticity, a hallmark of carcinoma progression, results in local and distant cancer dissemination. Carcinoma cell plasticity can be achieved through epithelial–mesenchymal transition (EMT), with cells positioned seemingly indiscriminately across the spectrum of EMT phenotypes. Different degrees of plasticity are achieved by transcriptional regulation and feedback-loops, which confer carcinoma cells with unique properties of tumor propagation and therapy resistance. Decoding the molecular and cellular basis of EMT in carcinoma should enable the discovery of new therapeutic strategies against cancer. In this review, we discuss the different attributes of plasticity in carcinoma and highlight the role of the canonical TGFβ receptor signaling pathway in the acquisition of plasticity. We emphasize the potential stochasticity of stemness in carcinoma in relation to plasticity and provide data from recent clinical trials that seek to target plasticity.

Stroma-targeting strategies in pancreatic cancer: Past lessons, challenges and prospects

Pancreatic ductal adenocarcinoma (PDAC) is projected to emerge as the second leading cause of cancer-related death after 2030. Extreme treatment resistance is perhaps the most significant factor that underlies the poor prognosis of PDAC. To date, combination chemotherapy remains the mainstay of treatment for most PDAC patients. Compared to other cancer types, treatment response of PDAC tumors to similar chemotherapy regimens is clearly much lower and shorter-lived. Aside from typically harboring genetic alterations that to date remain un-druggable and are drivers of treatment resistance, PDAC tumors are uniquely characterized by a densely fibrotic stroma that has well-established roles in promoting cancer progression and treatment resistance. However, emerging evidence also suggests that indiscriminate targeting and near complete depletion of stroma may promote PDAC aggressiveness and lead to detrimental outcomes. These conflicting results undoubtedly warrant the need for a more in-depth understanding of the heterogeneity of tumor stroma in order to develop modulatory strategies in favor of tumor suppression. The advent of novel techniques including single cell RNA sequencing and multiplex immunohistochemistry have further illuminated the complex heterogeneity of tumor cells, stromal fibroblasts, and immune cells. This new knowledge is instrumental for development of more refined therapeutic strategies that can ultimately defeat this disease. Here, we provide a concise review on lessons learned from past stroma-targeting strategies, new challenges revealed from recent preclinical and clinical studies, as well as new prospects in the treatment of PDAC.

A Decade Later: Revisiting the TGFβ Family's Role in Diabetes

In 2010, we published a review summarizing the role of the transforming growth factor-beta (TGFβ) family of proteins in diabetes. At that time there were still many outstanding questions that needed to be answered. In this updated review, we revisit the topic and provide new evidence that supports findings from previous studies included in the 2010 review and adds to the knowledge base with new findings and information. The most substantial contributions in the past 10 years have been in the areas of human data, the investigation of TGFβ family members other than activin [e.g., bone morphogenetic proteins (BMPs), growth and differentiation factor 11 (GDF11), nodal], and the expansion of β-cell number through various mechanisms including transdifferentiation, which was previously believed to not be possible.

TGF-β signaling in liver metastasis

The presence of liver metastases drastically worsens the prognosis of cancer patients. The liver is the second most prevalent metastatic site in cancer patients, but systemic therapeutic opportunities that target liver metastases are still limited. To aid the discovery of novel treatment options for metastatic liver disease, we provide insight into the cellular and molecular steps required for liver colonization. For successful colonization in the liver, adaptation of tumor cells and surrounding stroma is essential. This includes the formation of a pre-metastatic niche, the creation of a fibrotic and immune suppressive environment, angiogenesis, and adaptation of tumor cells. We illustrate that transforming growth factor β (TGF-β) is a central cytokine in all these processes. At last, we devise that future research should focus on TGF-β inhibitory strategies, especially in combination with immunotherapy. This promising systemic treatment strategy has potential to eliminate distant metastases as the efficacy of immunotherapy will be enhanced.

Beyond just a tight fortress: contribution of stroma to epithelial-mesenchymal transition in pancreatic cancer

Novel effective treatment is direly needed for patients with pancreatic ductal adenocarcinoma (PDAC). Therapeutics that target the driver mutations, especially the KRAS oncoprotein and its effector cascades, have been ineffective. It is increasing clear that the extensive fibro-inflammatory stroma (or desmoplasia) of PDAC plays an active role in the progression and therapeutic resistance of PDAC. The desmoplastic stroma is composed of dense extracellular matrix (ECM) deposited mainly by the cancer-associated-fibroblasts (CAFs) and infiltrated with various types of immune cells. The dense ECM functions as a physical barrier that limits tumor vasculatures and distribution of therapeutics to PDAC cells. In addition, mounting evidence have demonstrated that both CAFs and ECM promote PDAC cells aggressiveness through multiple mechanisms, particularly engagement of the epithelial-mesenchymal transition (EMT) program. Acquisition of a mesenchymal-like phenotype renders PDAC cells more invasive and resistant to therapy-induced apoptosis. Here, we critically review seminal and recent articles on the signaling mechanisms by which each stromal element promotes EMT in PDAC. We discussed the experimental models that are currently employed and best suited to study EMT in PDAC, which are instrumental in increasing the chance of successful clinical translation.

Targeting the TGFβ pathway in uterine carcinosarcoma

Uterine carcinosarcoma (UCS) is a relatively infrequent, but extremely aggressive endometrial malignancy. Although surgery and chemotherapy have improved outcomes, overall survival (OS) remains dismal due to the lack of targeted therapy and biphasic (epithelial and mesenchymal) nature that renders the tumor aggressive and difficult to manage. Here we report a role of transforming growth factor-β (TGFβ) in maintaining epithelial to mesenchymal transition (EMT) phenotype and aggressiveness in UCS. Using a 3D-culture system, we evaluated the efficacy of the transforming growth factor-β receptor-I (TGFβR1) kinase inhibitor Galunisertib (GLT), alone and in combination with standard chemotherapeutic drugs used for the management of UCS. We demonstrate that GLT by inhibiting canonical and non-canonical signaling emanating from transforming growth factor-β1 (TGFβ1) reduces cellular viability, invasion, clonal growth and differentiation. Interestingly, GLT sensitizes UCS cells to chemotherapy both in vitro and in in vivo preclinical tumor model. Hence, targeting TGFβ signaling, in combination with standard chemotherapy, may be exploited as an important strategy to manage the clinically challenging UCS.

Targeting all transforming growth factor-β isoforms with an Fc chimeric receptor impairs tumor growth and angiogenesis of oral squamous cell cancer

Tumor progression is governed by various growth factors and cytokines in the tumor microenvironment (TME). Among these, transforming growth factor-β (TGF-β) is secreted by various cell types residing in the TME and promotes tumor progression by inducing the epithelial-to-mesenchymal transition (EMT) of cancer cells and tumor angiogenesis. TGF-β comprises three isoforms, TGF-β1, -β2, and -β3, and transduces intracellular signals via TGF-β type I receptor (TβRI) and TGF-β type II receptor (TβRII). For the purpose of designing ligand traps that reduce oncogenic signaling in the TME, chimeric proteins comprising the ligand-interacting ectodomains of receptors fused with the Fc portion of immunoglobulin are often used. For example, chimeric soluble TβRII (TβRII-Fc) has been developed as an effective therapeutic strategy for targeting TGF-β ligands, but several lines of evidence indicate that TβRII-Fc more effectively traps TGF-β1 and TGF-β3 than TGF-β2, whose expression is elevated in multiple cancer types. In the present study, we developed a chimeric TGF-β receptor containing both TβRI and TβRII (TβRI-TβRII-Fc) and found that TβRI-TβRII-Fc trapped all TGF-β isoforms, leading to inhibition of both the TGF-β signal and TGF-β-induced EMT of oral cancer cells, whereas TβRII-Fc failed to trap TGF-β2. Furthermore, we found that TβRI-TβRII-Fc suppresses tumor growth and angiogenesis more effectively than TβRII-Fc in a subcutaneous xenograft model of oral cancer cells with high TGF-β expression. These results suggest that TβRI-TβRII-Fc may be a promising tool for targeting all TGF-β isoforms in the TME.

TNF-α enhances TGF-β-induced endothelial-to-mesenchymal transition via TGF-β signal augmentation

The tumor microenvironment (TME) consists of various components including cancer cells, tumor vessels, cancer-associated fibroblasts (CAFs), and inflammatory cells. These components interact with each other via various cytokines, which often induce tumor progression. Thus, a greater understanding of TME networks is crucial for the development of novel cancer therapies. Many cancer types express high levels of TGF-β, which induces endothelial-to-mesenchymal transition (EndMT), leading to formation of CAFs. Although we previously reported that CAFs derived from EndMT promoted tumor formation, the molecular mechanisms underlying these interactions remain to be elucidated. Furthermore, tumor-infiltrating inflammatory cells secrete various cytokines, including TNF-α. However, the role of TNF-α in TGF-β-induced EndMT has not been fully elucidated. Therefore, this study examined the effect of TNF-α on TGF-β-induced EndMT in human endothelial cells (ECs). Various types of human ECs underwent EndMT in response to TGF-β and TNF-α, which was accompanied by increased and decreased expression of mesenchymal cell and EC markers, respectively. In addition, treatment of ECs with TGF-β and TNF-α exhibited sustained activation of Smad2/3 signals, which was presumably induced by elevated expression of TGF-β type I receptor, TGF-β2, activin A, and integrin αv, suggesting that TNF-α enhanced TGF-β-induced EndMT by augmenting TGF-β family signals. Furthermore, oral squamous cell carcinoma-derived cells underwent epithelial-to-mesenchymal transition (EMT) in response to humoral factors produced by TGF-β and TNF-α-cultured ECs. This EndMT-driven EMT was blocked by inhibiting the action of TGF-βs. Collectively, our findings suggest that TNF-α enhances TGF-β-dependent EndMT, which contributes to tumor progression.

Pancreatic cancer triggers diabetes through TGF-β-mediated selective depletion of islet β-cells

Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease that remains incurable because of late diagnosis, which renders any therapeutic intervention challenging. Most PDAC patients develop de novo diabetes, which exacerbates their morbidity and mortality. How PDAC triggers diabetes is still unfolding. Using a mouse model of KrasG12D-driven PDAC, which faithfully recapitulates the progression of the human disease, we observed a massive and selective depletion of β-cells, occurring very early at the stages of preneoplastic lesions. Mechanistically, we found that increased TGF beta (TGF-β) signaling during PDAC progression caused erosion of β-cell mass through apoptosis. Suppressing TGF-β signaling, either pharmacologically through TGF-β immunoneutralization or genetically through deletion of Smad4 or TGF-β type II receptor (TβRII), afforded substantial protection against PDAC-driven β-cell depletion. From a translational perspective, both activation of TGF-β signaling and depletion of β-cells frequently occur in human PDAC, providing a mechanistic explanation for the pathogenesis of diabetes in PDAC patients, and further implicating new-onset diabetes as a potential early prognostic marker for PDAC.

SMAD4 and the TGFβ Pathway in Patients with Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer death worldwide. PDAC is an aggressive disease with an 11-month median overall survival and a five-year survival of less than 5%. Incidence of PDAC is constantly increasing and is predicted to become the second leading cause of cancer in Western countries within a decade. Despite research and therapeutic development, current knowledge about PDAC molecular mechanisms still needs improvements and it seems crucial to identify novel therapeutic targets. Genomic analyses of PDAC revealed that transforming growth factor β (TGFβ) signaling pathways are modified and the SMAD4 gene is altered in 47% and 60% of cases, respectively, highlighting their major roles in PDAC development. TGFβ can play a dual role in malignancy depending on the context, sometimes as an inhibitor and sometimes as an inducer of tumor progression. TGFβ signaling was identified as a potent inducer of epithelial-to-mesenchymal transition (EMT), a process that confers migratory and invasive properties to epithelial cells during cancer. Therefore, aberrant TGFβ signaling and EMT are linked to promoting PDAC aggressiveness. TGFβ and SMAD pathways were extensively studied but the mechanisms leading to cancer promotion and development still remain unclear. This review aims to describe the complex role of SMAD4 in the TGFβ pathway in patients with PDAC.

Development of a Tumor-Responsive Nanopolyplex Targeting Pancreatic Cancer Cells and Stroma

Desmoplasia plays a pivotal role in promoting pancreatic cancer progression and is associated with poor clinical outcome. Targeting the desmoplastic tumor microenvironment in combination with chemotherapy is therefore a promising strategy for pancreatic cancer therapy. Here, we report a novel biodegradable copolymer to codeliver LY2109761 (a TGF-β receptor I/II inhibitor) and CPI-613 (a novel chemotherapy agent) to desmoplastic stroma and tumor cells, respectively, in the tumor microenvironment. Hydrophobic CPI-613 is conjugated to the hydrophilic copolymer via a newly designed MMP-2-responsive linker to form a trigger-responsive nanopolyplex. LY2109761 is hydrophobic and encapsulated into the hydrophobic core of the nanopolyplex. The resulting nanopolyplex is modified with a plectin-1-targeting peptide to enhance the accumulation of the nanopolyplex in pancreatic tumors. The nanopolyplex aims to normalize the stroma by blocking the interaction between tumor cells and pancreatic stellate cells to inhibit the activation of pancreatic stellate cells and subsequently reduce the dense extracellular matrix. Normalized stroma increases the penetration of the nanopolyplex into the tumor. The nanopolyplex shows enhanced accumulation in xenograft pancreatic tumors in a biodistribution study. Moreover, the targeted nanopolyplex markedly inhibits tumor growth in an orthotopic pancreatic cancer mouse model by dual-targeting tumor cells and stroma. Overall, the multifunctional nanopolyplex is a promising platform for pancreatic cancer therapy.

HisCoM-PAGE: Hierarchical Structural Component Models for Pathway Analysis of Gene Expression Data

Although there have been several analyses for identifying cancer-associated pathways, based on gene expression data, most of these are based on single pathway analyses, and thus do not consider correlations between pathways. In this paper, we propose a hierarchical structural component model for pathway analysis of gene expression data (HisCoM-PAGE), which accounts for the hierarchical structure of genes and pathways, as well as the correlations among pathways. Specifically, HisCoM-PAGE focuses on the survival phenotype and identifies its associated pathways. Moreover, its application to real biological data analysis of pancreatic cancer data demonstrated that HisCoM-PAGE could successfully identify pathways associated with pancreatic cancer prognosis. Simulation studies comparing the performance of HisCoM-PAGE with other competing methods such as Gene Set Enrichment Analysis (GSEA), Global Test, and Wald-type Test showed HisCoM-PAGE to have the highest power to detect causal pathways in most simulation scenarios.

The prognostic role of soluble TGF-beta and its dynamics in unresectable pancreatic cancer treated with chemotherapy

Objectives

Transforming growth factor‐beta (TGF‐β) is a multifunctional regulatory factor. Here we measured serum soluble TGF‐β (sTGF‐β) levels and evaluated its dynamics and prognostic capabilities during chemotherapy in unresectable pancreatic cancer patients.

Methods

We prospectively enrolled 60 patients treated with FOLFIRINOX as the first‐line palliative chemotherapy. We collected blood samples at the time of diagnosis, first response assessment, and disease progression and measured serum sTGF‐β using an enzyme‐linked immunosorbent assay.

Results

The patients’ median overall survival (OS) and progression‐free survival (PFS) were 10.3 (95% confidence interval [CI], 8.5‐12.1) and 6.5 (95% CI, 4.9‐8.1) months, respectively. Patients with low sTGF‐β at diagnosis (<31.2 ng/mL) had better OS and PFS than patients with high sTGF‐β, respectively, (OS, 13.7 vs 9.2 months; hazard ratio [HR], 2.602; P = .004; PFS, 9.0 vs 5.8 months; HR, 2.010; P = .034). At the time of disease progression, sTGF‐β was increased compared with that of diagnosis (mean, 26.4 vs 23.9 ng/mL). In particular, sTGF‐β was significantly increased at disease progression in patients with a partial response (mean, 25.7 vs 31.0 ng/mL; P = .049).

Conclusions

Pretreatment sTGF‐β levels can serve as a prognostic indicator in unresectable pancreatic cancer patients treated with FOLFIRINOX chemotherapy. Likewise, the dynamics of sTGF‐β during chemotherapy have prognostic value.

Targeting TGFβR2-mutant tumors exposes vulnerabilities to stromal TGFβ blockade in pancreatic cancer

TGFβ is important during pancreatic ductal adenocarcinoma (PDA) progression. Canonical TGFβ signaling suppresses epithelial pancreatic cancer cell proliferation; as a result, inhibiting TGFβ has not been successful in PDA. In contrast, we demonstrate that inhibition of stromal TGFβR2 reduces IL‐6 production from cancer‐associated fibroblasts, resulting in a reduction of STAT3 activation in tumor cells and reversion of the immunosuppressive landscape. Up to 7% of human PDA have tumor cell‐specific deficiency in canonical TGFβ signaling via loss of TGFβR2. We demonstrate that in PDA that harbors epithelial loss of TGFβR2, inhibition of TGFβ signaling is selective for stromal cells and results in a therapeutic benefit. Our study highlights the potential benefit of TGFβ blockade in PDA and the importance of stratifying PDA patients who might benefit from such therapy.

Breaking barriers for T cells by targeting the EPHA2/TGF-β/COX-2 axis in pancreatic cancer

Pancreatic ductal adenocarcinoma is projected to become the second leading cause of cancer-related death and is largely resistant to immunotherapies. The tumor microenvironment, largely composed of heterogeneous myeloid cells, creates a physical, metabolic, and immunosuppressive barrier that prevents T cells from infiltrating cancer beds. In this issue of the JCI, Markosyan and colleagues have reported a tumor-intrinsic mechanism that excludes T cells from the vicinity of tumor cells. They showed that a receptor tyrosine kinase, ephrin-A receptor 2 (EPHA2), regulates prostaglandin endoperoxide synthase 2 (PTGS2) (encodes COX-2) expression in a TGF-β signaling-dependent manner. Genetic ablation of Epha2 or Ptgs2 in preclinical models or pharmacological inhibition of COX-2 elicited the transformation of this immunosuppressive microenvironment into a T cell-permissive milieu. Consequent T cell relocation rendered this immunoresistant malignancy responsive to combinations of checkpoint blockers and CD40 agonists. Because the association between T cell infiltration and the EPHA2/TGF-β/COX-2 axis is supported by independent clinical data, these results provide a rationale for ensuing clinical trials aimed at incorporating pancreatic cancer into the range of immunotherapy-responsive tumors.

A New Switch for TGFβ in Cancer

The TGFβ cytokine plays dichotomous roles during tumor progression. In normal and premalignant cancer cells, the TGFβ signaling pathway inhibits proliferation and promotes cell-cycle arrest and apoptosis. However, the activation of this pathway in late-stage cancer cells could facilitate the epithelial-to-mesenchymal transition, stemness, and mobile features to enhance tumorigenesis and metastasis. The opposite functions of TGFβ signaling during tumor progression make it a challenging target to develop anticancer interventions. Nevertheless, the recent discovery of cellular contextual determinants, especially the binding partners of the transcription modulators Smads, is critical to switch TGFβ responses from proapoptosis to prometastasis. In this review, we summarize the recently identified contextual determinants (such as PSPC1, KLF5, 14-3-3ζ, C/EBPβ, and others) and the mechanisms of how tumor cells manage the context-dependent autonomous TGFβ responses to potentiate tumor progression. With the altered expression of some contextual determinants and their effectors during tumor progression, the aberrant molecular prometastatic switch might serve as a new class of theranostic targets for developing anticancer strategies.

The Clinical Potential of Oligonucleotide Therapeutics against Pancreatic Cancer

Although many diagnostic and therapeutic modalities for pancreatic cancer have been proposed, an urgent need for improved therapeutic strategies remains. Oligonucleotide therapeutics, such as those based on antisense RNAs, small interfering RNA (siRNA), microRNA (miRNA), aptamers, and decoys, are promising agents against pancreatic cancer, because they can identify a specific mRNA fragment of a given sequence or protein, and interfere with gene expression as molecular-targeted agents. Within the past 25 years, the diversity and feasibility of these drugs as diagnostic or therapeutic tools have dramatically increased. Several clinical and preclinical studies of oligonucleotides have been conducted for patients with pancreatic cancer. To support the discovery of effective diagnostic or therapeutic options using oligonucleotide-based strategies, in the absence of satisfactory therapies for long-term survival and the increasing trend of diseases, we summarize the current clinical trials of oligonucleotide therapeutics for pancreatic cancer patients, with underlying preclinical and scientific data, and focus on the possibility of oligonucleotides for targeting pancreatic cancer in clinical implications.

LncRNA XIST enhanced TGF-β2 expression by targeting miR-141-3p to promote pancreatic cancer cells invasion

The level of expression of long non-coding RNA (LncRNA) X-inactive specific transcript (XIST) is up-regulated in pancreatic cancer (PC). However, the role of XIST in PC and the underlying mechanism are still unknown. The present study aimed to elucidate how XIST participates in PC and its potential target, miR-141-3p. We detected the XIST expression in PC tissues and cells by qRT-PCR. Cell proliferation was measured using a CCK8 kit, and the migration and invasion of cells was measured by Transwell assay. Silencing XIST and miR-141-3p was performed with transfection by Lipofectamine kit. Binding assay was conducted by luciferase reporter assay. Protein expression was examined by Western blot. These results indicate that (i) XIST is highly expressed in tumor tissues while miR-141-3p is down-regulated. (ii) Silencing XIST inhibits the pancreatic cell proliferation, migration and invasion. (iii) MiR-141-3p inhibitor alleviates the inhibitory effect by siXIST in PC cell lines. (iv) MiR-141-3p directly interacts with XIST and also negatively regulates transforming growth factor-β 2 (TGF-β2) expression. (v) Overexpression of XIST attenuates the inhibition of TGF-β2 expression by miR-141-3p. The conclusion, is that XIST could promote proliferation, migration and invasion of PC cells via miR-141-5p/TGF-β2 axis.

TGIF1 functions as a tumor suppressor in pancreatic ductal adenocarcinoma

A prominent function of TGIF1 is suppression of transforming growth factor beta (TGF-β) signaling, whose inactivation is deemed instrumental to the progression of pancreatic ductal adenocarcinoma (PDAC), as exemplified by the frequent loss of the tumor suppressor gene SMAD4 in this malignancy. Surprisingly, we found that genetic inactivation of Tgif1 in the context of oncogenic Kras, KrasG12D , culminated in the development of highly aggressive and metastatic PDAC despite de-repressing TGF-β signaling. Mechanistic experiments show that TGIF1 associates with Twist1 and inhibits Twist1 expression and activity, and this function is suppressed in the vast majority of human PDACs by KrasG12D /MAPK-mediated TGIF1 phosphorylation. Ablating Twist1 in KrasG12D ;Tgif1KO mice completely blunted PDAC formation, providing the proof-of-principle that TGIF1 restrains KrasG12D -driven PDAC through its ability to antagonize Twist1. Collectively, these findings pinpoint TGIF1 as a potential tumor suppressor in PDAC and further suggest that sustained activation of TGF-β signaling might act to accelerate PDAC progression rather than to suppress its initiation.

Molecular Engineering of the TGF-β Signaling Pathway

Transforming growth factor beta (TGF-β) is an important growth factor that plays essential roles in regulating tissue development and homeostasis. Dysfunction of TGF-β signaling is a hallmark of many human diseases. Therefore, targeting TGF-β signaling presents broad therapeutic potential. Since the discovery of the TGF-β ligand, a collection of engineered signaling proteins have been developed to probe and manipulate TGF-β signaling responses. In this review, we highlight recent progress in the engineering of TGF-β signaling for different applications and discuss how molecular engineering approaches can advance our understanding of this important pathway. In addition, we provide a future outlook on the opportunities and challenges in the engineering of the TGF-β signaling pathway from a quantitative perspective.

Loss of Disabled-2 Expression in Pancreatic Cancer Progression

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive cancer type characterized by rapid metastasis and resistance to chemotherapy, properties that are shared by cancer stem cells (CSCs). In pancreatic cancer, tumor cells which possess the properties of CSCs also phenotypically resemble cells that have undergone epithelial-to-mesenchymal transition or EMT. Disabled-2 (Dab2) is a multifunctional scaffold protein frequently downregulated in cancer that has been linked to the process of EMT. However, the role of Dab2 in pancreatic cancer development and progression remains unclear. Downregulation of Dab2 expression in pancreatic cancer cell lines was found to trigger induction of genes characteristic of EMT and the CSC phenotype, while overexpression of Dab2 in the Panc1 cell line blocked the process of TGFβ-stimulated EMT. In addition, selective inhibition of the TGFβRI/RII receptors was found to reverse genes altered by Dab2 downregulation. Dab2 mRNA expression was found to be decreased in PDAC tumor samples, as compared to levels observed in normal pancreatic tissue. Methylation of the Dab2 gene promoter was demonstrated in Stage I PDAC tumors and in the MiaPaCa2 cell line, suggesting that promoter methylation may silence Dab2 expression early in pancreatic cancer progression. These results suggest that Dab2 may function as a tumor suppressor in pancreatic cancer by modulation of the TGFβ-stimulated EMT and CSC phenotype.

Enhanced preclinical antitumor activity of M7824, a bifunctional fusion protein simultaneously targeting PD-L1 and TGF-β

Antibodies targeting immune checkpoints are emerging as potent and viable cancer therapies, but not all patients respond to these as single agents. Concurrently targeting additional immunosuppressive pathways is a promising approach to enhance immune checkpoint blockade, and bifunctional molecules designed to target two pathways simultaneously may provide a strategic advantage over the combination of two single agents. M7824 (MSB0011359C) is a bifunctional fusion protein composed of a monoclonal antibody against programmed death ligand 1 (PD-L1) fused to the extracellular domain of human transforming growth factor-β (TGF-β) receptor II, which functions as a "trap" for all three TGF-β isoforms. We demonstrate that M7824 efficiently, specifically, and simultaneously binds PD-L1 and TGF-β. In syngeneic mouse models, M7824 suppressed tumor growth and metastasis more effectively than treatment with either an anti-PD-L1 antibody or TGF-β trap alone; furthermore, M7824 extended survival and conferred long-term protective antitumor immunity. Mechanistically, the dual anti-immunosuppressive function of M7824 resulted in activation of both the innate and adaptive immune systems, which contributed to M7824's antitumor activity. Finally, M7824 was an effective combination partner for radiotherapy or chemotherapy in mouse models. Collectively, our preclinical data demonstrate that simultaneous blockade of the PD-L1 and TGF-β pathways by M7824 elicits potent and superior antitumor activity relative to monotherapies.

Estrogen-related receptor alpha induces epithelial-mesenchymal transition through cancer-stromal interactions in endometrial cancer

Estrogen-related receptor alpha (ERRα), which shares structural similarities with estrogen receptors, is associated with tumor progression in endometrial cancer, but little is known about the detailed underlying mechanism. We investigated whether ERRα, in cooperation with peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), could participate in epithelial-mesenchymal transition (EMT) in endometrial cancer through cancer-stromal interactions. Two endometrial cancer cell lines, Ishikawa and HEC-1A, transfected with ERRα/PGC-1α expression plasmids or silenced for ERRα expression, were co-cultured with telomerase-transformed human endometrial stromal cells (T-HESCs). We found that EMT-associated factors including vimentin, Snail, and zinc finger E-box binding homeobox 1 were upregulated in cancer cells overexpressing ERRα/PGC-1α and that transforming growth factor-beta (TGF-β) was induced in T-HESCs in the same conditions. In contrast, ERRα knockdown suppressed EMT-associated factors in cancer cells and TGF-β in T-HESCs. ERRα/PGC-1α overexpression increased the expression of EMT-associated factors after TGF-β exposure; however, it decreased E-cadherin at protein level. ERRα knockdown suppressed EMT-associated factors in the presence of TGF-β, whereas E-cadherin remained unchanged. Matrigel invasion assays revealed that ERRα knockdown attenuated the stimulation of migration and invasion by TGF-β. These findings suggest that ERRα is a potential target for inhibiting TGF-β-induced EMT through cancer-stromal interactions in endometrial cancer.

Stromal protein βig-h3 reprogrammes tumour microenvironment in pancreatic cancer

OBJECTIVE

Pancreatic cancer is associated with an abundant stromal reaction leading to immune escape and tumour growth. This massive stroma drives the immune escape in the tumour. We aimed to study the impact of βig-h3 stromal protein in the modulation of the antitumoural immune response in pancreatic cancer.

DESIGN

We performed studies with p48-Cre;KrasG12D, pdx1-Cre;KrasG12D;Ink4a/Arffl/fl, pdx1-Cre;KrasG12D; p53R172H mice and tumour tissues from patients with pancreatic ductal adenocarcinoma (PDA). Some transgenic mice were given injections of anti-βig-h3, anti-CD8, anti-PD1 depleting antibodies. Tumour growth as well as modifications in the activation of local immune cells were analysed by flow cytometry, immunohistochemistry and immunofluorescence. Tissue stiffness was measured by atomic force microscopy.

RESULTS

We identified βig-h3 stromal-derived protein as a key actor of the immune paracrine interaction mechanism that drives pancreatic cancer. We found that βig-h3 is highly produced by cancer-associated fibroblasts in the stroma of human and mouse. This protein acts directly on tumour-specific CD8+ T cells and F4/80 macrophages. Depleting βig-h3 in vivo reduced tumour growth by enhancing the number of activated CD8+ T cell within the tumour and subsequent apoptotic tumour cells. Furthermore, we found that targeting βig-h3 in established lesions released the tissue tension and functionally reprogrammed F4/80 macrophages in the tumour microenvironment.

CONCLUSIONS

Our data indicate that targeting stromal extracellular matrix protein βig-h3 improves the antitumoural response and consequently reduces tumour weight. Our findings present βig-h3 as a novel immunological target in pancreatic cancer.

Desmoplasia in Lymph Node Metastasis of Pancreatic Adenocarcinoma Reveals Activation of Cancer-Associated Fibroblasts Pattern and T-helper 2 Immune Cell Infiltration

OBJECTIVES

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a peritumoral proliferation of fibroblasts and extracellular matrix production known as desmoplasia. We aimed to study desmoplasia in PDAC lymph node (LN) metastases.

METHODS

We evaluated LNs from 66 patients with PDAC and LN metastases. We used immunohistochemistry and real-time polymerase chain reaction to phenotype the desmoplastic response.

RESULTS

Desmoplasia was identified in 57% of patients with LN metastases (Des+). Cancer-associated fibroblasts (CAFs) in Des+ expressed α-smooth muscle actin and collagen 11A1. The latter expression was present only in CAFs but not in LN stroma or in LN metastases without desmoplasia (Des-). Desmoplasia was associated with upregulation of transforming growth factor β messenger RNA. Whereas numbers of CD8+ in tumor vicinity were not different between Des+ and Des- patients (78 [standard deviation {SD}, 57] vs 92 [SD, 52], P = 0.48, respectively), the numbers of GATA-3+ cells, a marker of T-helper 2 immune response was significantly increased (3.7 [SD, 6.3] for Des+ vs 1.3 [SD, 2.7] for Des-, P < 0.05).

CONCLUSIONS

Lymph node desmoplasia is associated with CAF pattern activation and Th2 infiltration. Therapeutic modulation of desmoplasia may be relevant in the metastatic phase and influence antitumor immune response.

The Role of TGF-β and Its Receptors in Gastrointestinal Cancers

Early detection of gastrointestinal tumors improves patient survival. However, patients with these tumors are typically diagnosed at an advanced stage and have poor prognosis. The incidence and mortality of gastrointestinal cancers, including esophageal, gastric, liver, colorectal, and pancreatic cancers, are increasing worldwide. Novel diagnostic and therapeutic agents are required to improve patient survival and quality of life. The tumor microenvironment, which contains nontumor cells, signaling molecules such as growth factors and cytokines, and extracellular matrix proteins, plays a critical role in cancer cell proliferation, invasion, and metastasis. Transforming growth factor beta (TGF-β) signaling has dual roles in gastrointestinal tumor development and progression as both a tumor suppressor and tumor promoter. Here, we review the dynamic roles of TGF-β and its receptors in gastrointestinal tumors and provide evidence that targeting TGF-β signaling may be an effective therapeutic strategy.

Dkk1 involvement and its potential as a biomarker in pancreatic ductal adenocarcinoma

Dickkopf-1 (Dkk1)'s dysregulation has been implicated in the pathogenesis of a variety of cancers. It is part of the Dkk family of proteins that includes Dkk2, Dkk3 and Dkk4. This family of secreted proteins shares similar conserved cysteine domains and inhibits the Wnt/b-catenin pathway by causing proteasomal B-catenin degradation, inducing apoptosis, and preventing cell proliferation. Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer mortality in the United States due to the late stage of diagnosis and the limited effectiveness of current therapy. Dkk1 is found increased in PADC patients' specimens and serum. Dkk1 can be a promising biomarker specific to PDAC, which has the potential to increase PDAC survival rates through improving early stage detection and monitoring progression compared to current biomarker gold standards. In addition, recent studies suggest that Dkk1 could be an excellent target for cancer immunotherapy. Interestingly, Dkk1-CKAP4-PI3K/AKT signal pathway also plays role in pancreatic cancer cell proliferation. In this review, we present the multiple mechanisms of Dkk1 in PDAC studied thus far and explore its function, regulation, and clinical applications in gynecological cancers including pancreatic ductal adenocarcinoma (PDAC), breast, ovarian, cervical, and endometrial cancer. Further research into Dkk1's mechanism and use as a diagnostic tool, alone or in combination with other biomarkers, could prove clinically useful for better understanding the pathology of PDAC and improving its early detection and treatment.

Epithelial-Stromal Interactions in Pancreatic Cancer

Pancreatic cancer is characterized by an extensive fibroinflammatory reaction that includes immune cells, fibroblasts, extracellular matrix, vascular and lymphatic vessels, and nerves. Overwhelming evidence indicates that the pancreatic cancer microenvironment regulates cancer initiation, progression, and maintenance. Pancreatic cancer treatment has progressed little over the past several decades, and the prognosis remains one of the worst for any cancer. The contribution of the microenvironment to carcinogenesis is a key area of research, offering new potential targets for treating the disease. Here, we explore the composition of the pancreatic cancer stroma, discuss the network of interactions between different components, and describe recent attempts to target the stroma therapeutically. We also discuss current areas of active research related to the tumor microenvironment.