Unchaining the beast; insights from structural and evolutionary studies on TGFβ secretion, sequestration, and activation

Extracellular proteolysis in cancer: Proteases, substrates, and mechanisms in tumor progression and metastasis

A vast ensemble of extracellular proteins influences the development and progression of cancer, shaped and reshaped by a complex network of extracellular proteases. These proteases, belonging to the distinct classes of metalloproteases, serine proteases, cysteine proteases, and aspartic proteases, play a critical role in cancer. They often become dysregulated in cancer, with increases in pathological protease activity frequently driven by the loss of normal latency controls, diminished regulation by endogenous protease inhibitors, and changes in localization. Dysregulated proteases accelerate tumor progression and metastasis by degrading protein barriers within the extracellular matrix (ECM), stimulating tumor growth, reactivating dormant tumor cells, facilitating tumor cell escape from immune surveillance, and shifting stromal cells toward cancer-promoting behaviors through the precise proteolysis of specific substrates to alter their functions. These crucial substrates include ECM proteins and proteoglycans, soluble proteins secreted by tumor and stromal cells, and extracellular domains of cell surface proteins, including membrane receptors and adhesion proteins. The complexity of the extracellular protease web presents a significant challenge to untangle. Nevertheless, technological strides in proteomics, chemical biology, and the development of new probes and reagents are enabling progress and advancing our understanding of the pivotal importance of extracellular proteolysis in cancer.

Binding requirements for latent transforming growth factor Beta2 activation

Although the mechanism for activation of latent TGFβ1 and TGFβ3 is understood to involve the binding of the TGFβ propeptide (LAP) to both an integrin and an insoluble substrate, the activation of latent TGFβ2 has been unclear because the TGFβ2 LAP does not have the classical integrin binding sequence found in the other two TGFβ isoform LAPs. To assess the potential requirement for covalent linkage with a matrix or cell surface protein for the activation of latent TGFβ2, we generated mice in which the TGFβ2 Cys residue predicted to be involved in binding was mutated to Ser (Tgfb2C24S). We reasoned that, if covalent interaction with a second molecule is required for latent TGFβ2 activation, mutant mice should display a Tgfb2 null (Tgfb2-/-)-like phenotype. Tgfb2C24S mice closely phenocopy Tgfb2-/- mice with death in utero between E18 and P1 and with congenital heart and kidney defects similar to those described for Tgfb2-/- mice. The mutant latent TGFβ2 is secreted at levels similar to WT, yet TGFβ signaling monitored as nuclear pSmad2 is suppressed. We conclude that, like latent TGFβ1, latent TGFβ2 activation requires binding to an immobilized matrix or plasma membrane molecule.

Noncanonical WNT5A controls the activation of latent TGF-β to drive fibroblast activation and tissue fibrosis

Transforming growth factor β (TGF-β) signaling is a core pathway of fibrosis, but the molecular regulation of the activation of latent TGF-β remains incompletely understood. Here, we demonstrate a crucial role of WNT5A/JNK/ROCK signaling that rapidly coordinates the activation of latent TGF-β in fibrotic diseases. WNT5A was identified as a predominant noncanonical WNT ligand in fibrotic diseases such as systemic sclerosis, sclerodermatous chronic graft-versus-host disease, and idiopathic pulmonary fibrosis, stimulating fibroblast-to-myofibroblast transition and tissue fibrosis by activation of latent TGF-β. The activation of latent TGF-β requires rapid JNK- and ROCK-dependent cytoskeletal rearrangements and integrin αV (ITGAV). Conditional ablation of WNT5A or its downstream targets prevented activation of latent TGF-β, rebalanced TGF-β signaling, and ameliorated experimental fibrosis. We thus uncovered what we believe to be a novel mechanism for the aberrant activation of latent TGF-β in fibrotic diseases and provided evidence for targeting WNT5A/JNK/ROCK signaling in fibrotic diseases as a new therapeutic approach.

Hepatocellular Carcinoma: Old and Emerging Therapeutic Targets

Liver cancer, predominantly hepatocellular carcinoma (HCC), globally ranks sixth in incidence and third in cancer-related deaths. HCC risk factors include non-viral hepatitis, alcohol abuse, environmental exposures, and genetic factors. No specific genetic alterations are unequivocally linked to HCC tumorigenesis. Current standard therapies include surgical options, systemic chemotherapy, and kinase inhibitors, like sorafenib and regorafenib. Immunotherapy, targeting immune checkpoints, represents a promising avenue. FDA-approved checkpoint inhibitors, such as atezolizumab and pembrolizumab, show efficacy, and combination therapies enhance clinical responses. Despite this, the treatment of hepatocellular carcinoma (HCC) remains a challenge, as the complex tumor ecosystem and the immunosuppressive microenvironment associated with it hamper the efficacy of the available therapeutic approaches. This review explores current and advanced approaches to treat HCC, considering both known and new potential targets, especially derived from proteomic analysis, which is today considered as the most promising approach. Exploring novel strategies, this review discusses antibody drug conjugates (ADCs), chimeric antigen receptor T-cell therapy (CAR-T), and engineered antibodies. It then reports a systematic analysis of the main ligand/receptor pairs and molecular pathways reported to be overexpressed in tumor cells, highlighting their potential and limitations. Finally, it discusses TGFβ, one of the most promising targets of the HCC microenvironment.

A prognostic marker LTBP1 is associated with epithelial mesenchymal transition and can promote the progression of gastric cancer

LTBP1 is closely related to TGF-β1 function as an essential component, which was unclear in gastric cancer (GC). Harbin Medical University (HMU)-GC cohort and The Cancer Genome Atlas (TCGA) dataset were combined to form a training cohort to calculate the connection between LTBP1 mRNA expression, prognosis and clinicopathological features. The training cohort was also used to verify the biological function of LTBP1 and its relationship with immune microenvironment and chemosensitivity. In the tissue microarrays (TMAs), immunohistochemical (IHC) staining was performed to observe LTBP1 protein expression. The correlation between LTBP1 protein expression level and prognosis was also analyzed, and a nomogram model was constructed. Western blotting (WB) was used in cell lines to assess LTBP1 expression. Transwell assays and CCK-8 were employed to assess LTBP1's biological roles. In compared to normal gastric tissues, LTBP1 expression was upregulated in GC tissues, and high expression was linked to a bad prognosis for GC patients. Based on a gene enrichment analysis, LTBP1 was primarily enriched in the TGF-β and EMT signaling pathways. Furthermore, high expression of LTBP1 in the tumor microenvironment was positively correlated with an immunosuppressive response. We also found that LTBP1 expression (p = 0.006) and metastatic lymph node ratio (p = 0.044) were independent prognostic risk factors for GC patients. The prognostic model combining LTBP1 expression and lymph node metastasis ratio reliably predicted the prognosis of GC patients. In vitro proliferation and invasion of MKN-45 GC cells were inhibited and their viability was decreased by LTBP1 knockout. LTBP1 plays an essential role in the development and progression of GC, and is a potential prognostic biomarker and therapeutic target for GC.

Advances in mesenchymal stem cells therapy for tendinopathies

Tendinopathies are chronic diseases of an unknown etiology and associated with inflammation. Mesenchymal stem cells (MSCs) have emerged as a viable therapeutic option to combat the pathological progression of tendinopathies, not only because of their potential for multidirectional differentiation and self-renewal, but also their excellent immunomodulatory properties. The immunomodulatory effects of MSCs are increasingly being recognized as playing a crucial role in the treatment of tendinopathies, with MSCs being pivotal in regulating the inflammatory microenvironment by modulating the immune response, ultimately contributing to improved tissue repair. This review will discuss the current knowledge regarding the application of MSCs in tendinopathy treatments through the modulation of the immune response.

Decrypting the Pathological Pathways in IgA Nephropathy

IgAN is the most common form of glomerulonephritis affecting 2000000 people annually. The disease ultimately progresses to chronic renal failure and ESRD. In this article, we focused on a comprehensive understanding of the pathogenesis of the disease and thus identifying different target proteins that could be essential in therapeutic approaches in the management of the disease. Aberrantly glycosylated IgA1 produced by the suppression of the enzyme β-1, 3 galactosyltransferase ultimately triggered the formation of IgG autoantibodies which form complexes with Gd-IgA1. The complex gets circulated through the blood vessels through monocytes and ultimately gets deposited in the glomerular mesangial cells via CD71 receptors present locally. This complex triggers the inflammatory pathways activating the alternate complement system, various types of T Cells, toll-like receptors, cytokines, and chemokines ultimately recruiting the phagocytic cells to eliminate the Gd-IgA complex. The inflammatory proteins cause severe mesangial and podocyte damage in the kidney which ultimately initiates the repair process following chronic inflammation by an important protein named TGFβ1. TGF β1 is an important protein produced during chronic inflammation mediating the repair process via various downstream transduction proteins and ultimately producing fibrotic proteins which help in the repair process but permanently damage the glomerular cells.

Genome-wide identification, evolution and expression of TGF-β signaling pathway members in mandarin fish (Siniperca chuatsi)

Members of the transforming growth factor β (TGF-β) signaling pathway regulate diverse cellular biological processes in embryonic and tissue development. We took mandarin fish (Siniperca chuatsi) as the research object to identify all members of the TGF-β signaling pathway, measure their expression pattern in the key period post hatching, and further explore their possible role in the process of sex regulation. Herein, we identified eighty-three TGF-β signaling pathway members and located them on chromosomes based on the genome of mandarin fish. TGF-β signaling pathway members were highly conserved since each TGF-β subfamily clustered with orthologs from other species. Transcriptome analysis, qRT-PCR and in situ hybridization demonstrated that most mandarin fish TGF-β signaling pathway members presented stage-specific and/or sex-dimorphic expression during gonadal development, and different members of the TGF-β signaling pathway participated in different stages of gonadal development. Taken together, our results provide new insight into the role of TGF-β signaling pathway members in the sex regulation of mandarin fish.

Study of the Urinary TGF-β1 Profile in Diabetic Nephropathy: A Single-Center Experience From India

Background Diabetic nephropathy is one of the important causes of end-stage kidney disease (ESKD). Of the various cytokines playing a role in the pathogenesis of diabetic nephropathy, transforming growth factor beta-1 (TGF-β1) is an important one. Its major role is to mediate extracellular matrix deposition. Increased renal expression of TGF-β1 is found in diabetic nephropathy and its urinary excretion can serve as a useful marker of outcomes. Material and methods A prospective observational study was conducted, which included 10 cases of diabetic nephropathy in group A with age ≥ 18 years and a urinary protein creatinine ratio (UPCR) value of > 0.5 mg/mg and 10 healthy controls in group B. Patients with active urinary tract infection, chronic kidney disease (CKD) stage Vd patients on maintenance hemodialysis, and renal transplant recipients were excluded from the study. Urinary TGF-β1 level estimation in a 24-hour urine sample, 24-hour urine protein, and other baseline laboratory investigations were done. Results In diabetic nephropathy cases (group A), the mean value of urinary TGF-β1 levels was 88.33± 12.44 ng/24 hours. In the control group (group B), the mean value of urinary TGF-β1 was 29.03 ± 3.23 ng/24 hours. Urinary TGF-β1 levels were significantly elevated in group A as compared to group B (p<0.001). There was no significant correlation between urinary TGF-β1 levels and estimated glomerular filtration rate (eGFR) (r=0.376, p= 0.285) as well as the urinary TGF-β1 levels and 24-hour urine protein levels (p = 0.334, r = 0.341) in diabetic nephropathy cases. Glycosylated hemoglobin (HbA1c) levels didn't correlate with the urinary TGF-β1 levels (r = -0.265, p = 0.46). Conclusion The urinary TGF-β1 levels were significantly elevated in diabetic nephropathy patients as compared to healthy controls. There was no significant correlation between urinary TGF-β1 levels and proteinuria, eGFR, or HbA1c levels in diabetic nephropathy patients.

Tenascins and osteopontin in biological response in cornea

The structural composition, integrity and regular curvature of the cornea contribute to the maintenance of its transparency and vision. Disruption of its integrity caused by injury results in scarring, inflammation and neovascularization followed by losses in transparency. These sight compromising effects is caused by dysfunctional corneal resident cell responses induced by the wound healing process. Upregulation of growth factors/cytokines and neuropeptides affect development of aberrant behavior. These factors trigger keratocytes to first transform into activated fibroblasts and then to myofibroblasts. Myofibroblasts express extracellular matrix components for tissue repair and contract the tissue to facilitate wound closure. Proper remodeling following primary repair is critical for restoration of transparency and visual function. Extracellular matrix components contributing to the healing process are divided into two groups; a group of classical tissue structural components and matrix macromolecules that modulate cell behaviors/activities besides being integrated into the matrix structure. The latter components are designated as matricellular proteins. Their functionality is elicited through mechanisms which modulate the scaffold integrity, cell behaviors, activation/inactivation of either growth factors or cytoplasmic signaling regulation. We discuss here the functional roles of matricellular proteins in mediating injury-induced corneal tissue repair. The roles are described of major matricellular proteins, which include tenascin C, tenascin X and osteopontin. Focus is directed towards dealing with their roles in modulating individual activities of wound healing-related growth factors, e. g., transforming growth factor β (TGF β). Modulation of matricellular protein functions could encompass a potential novel strategy to improve the outcome of injury-induced corneal wound healing.

ACUTE ELUTION OF TGFβ2 AFFECTS THE SMOOTH MUSCLE CELLS IN A COMPLIANCE-MATCHED VASCULAR GRAFT

Transforming growth factor beta 2 (TGFβ2) is a pleiotropic growth factor that plays a vital role in smooth muscle cell (SMC) function. Our prior in vitro work has shown that SMC response can be modulated with TGFβ2 stimulation in a dose dependent manner. In particular, we have shown that increasing concentrations of TGFβ2 shift SMCs from a migratory to a synthetic behavior. In this work, electrospun compliance-matched and hypocompliant TGFβ2-eluting TEVGs were implanted into Sprague Dawley rats for 5 days to observe SMC population and collagen production. TEVGs were fabricated using a combined computational and experimental approach that varied the ratio of gelatin:polycaprolactone to be either compliance-matched or twice as stiff as rat aorta (hypocompliant). TGFβ2 concentrations of 0, 10, 100 ng/mg were added to both graft types (n=3 in each group) and imaged in vivo using ultrasound. Histological markers (SMC, macrophage, collagen, and elastin) were evaluated following explantation at 5 days. In vivo ultrasound showed that compliance-matched TEVGs became stiffer as TGFβ2 increased (100 ng/mg TEVGS compared to rat aorta, p<0.01) while all hypocompliant grafts remained stiffer than control rat aorta. In vivo velocity and diameter were also not significantly different than control vessels. The compliance-matched 10 ng/mg group had an elevated SMC signal (myosin heavy chain) compared to the 0 and 100 ng/mg grafts (p=0.0009 & 0.0006 ). Compliance-matched TEVGs containing 100 ng/mg TGFβ2 had an increase in collagen production (p<0.01), general immune response (p<0.05), and a decrease in SMC population to the 0 and 10 ng/mg groups. All hypocompliant groups were found to be similar, suggesting a lower rate of TGFβ2 release in these TEVGs. Our results suggest that TGFβ2 can modulate in vivo SMC phenotype over an acute implantation period, which is consistent with our prior in vitro work. To the author's knowledge, this is first in vivo rat study that evaluates a TGFβ2-eluting TEVG.

Crosstalk Between ROS and Autophagy in Tumorigenesis: Understanding the Multifaceted Paradox

Cancer formation is a highly regulated and complex process, largely dependent on its microenvironment. This complexity highlights the need for developing novel target-based therapies depending on cancer phenotype and genotype. Autophagy, a catabolic process, removes damaged and defective cellular materials through lysosomes. It is activated in response to stress conditions such as nutrient deprivation, hypoxia, and oxidative stress. Oxidative stress is induced by excess reactive oxygen species (ROS) that are multifaceted molecules that drive several pathophysiological conditions, including cancer. Moreover, autophagy also plays a dual role, initially inhibiting tumor formation but promoting tumor progression during advanced stages. Mounting evidence has suggested an intricate crosstalk between autophagy and ROS where they can either suppress cancer formation or promote disease etiology. This review highlights the regulatory roles of autophagy and ROS from tumor induction to metastasis. We also discuss the therapeutic strategies that have been devised so far to combat cancer. Based on the review, we finally present some gap areas that could be targeted and may provide a basis for cancer suppression.

Molecular Evolution of Transforming Growth Factor-β (TGF-β) Gene Family and the Functional Characterization of Lamprey TGF-β2

The transforming growth factor-βs (TGF-βs) are multifunctional cytokines capable of regulating a wide range of cellular behaviors and play a key role in maintaining the homeostasis of the immune system. The TGF-β subfamily, which is only present in deuterostomes, expands from a single gene in invertebrates to multiple members in jawed vertebrates. However, the evolutionary processes of the TGF-β subfamily in vertebrates still lack sufficient elucidation. In this study, the TGF-β homologs are identified at the genome-wide level in the reissner lamprey (Lethenteron reissneri), the sea lamprey (Petromyzon marinus), and the Japanese lamprey (Lampetra japonica), which are the extant representatives of jawless vertebrates with a history of more than 350 million years. The molecular evolutionary analyses reveal that the lamprey TGF-β subfamily contains two members representing ancestors of TGF-β2 and 3 in vertebrates, respectively, but TGF-β1 is absent. The transcriptional expression patterns show that the lamprey TGF-β2 may play a central regulatory role in the innate immune response of the lamprey since it exhibits a more rapid and significant upregulation of expression than TGF-β3 during lipopolysaccharide stimuli. The incorporation of BrdU assay reveals that the lamprey TGF-β2 recombinant protein exerts the bipolar regulation on the proliferation of the supraneural myeloid body cells (SMB cells) in the quiescent and LPS-activated state, while plays an inhibitory role in the proliferation of quiescent and activated leukocytes in lampreys. Furthermore, caspase-3/7 activity analysis indicates that the lamprey TGF-β2 protects SMB cells from apoptosis after serum deprivation, in contrast to promoting apoptosis of leukocytes. Our composite results offer valuable clues to the origin and evolution of the TGF-β subfamily and imply that TGF-βs are among the most ancestral immune regulators in vertebrates.

The role of LTBPs in TGF beta signaling

The purpose of this review is to discuss the transforming growth factor beta (TGFB) binding proteins (LTBP) with respect to their participation in the activity of TGFB. We first describe pertinent aspects of the biology and cell function of the LTBPs. We then summarize the physiological consequences of LTBP loss in humans and mice. Finally, we consider a number of outstanding questions relating to LTBP function.

Six Shades of Vascular Smooth Muscle Cells Illuminated by KLF4 (Krüppel-Like Factor 4)

Multiple layers of vascular smooth muscle cells (vSMCs) are present in blood vessels forming the media of the vessel wall. vSMCs provide a vessel wall structure, enabling it to contract and relax, thus modulating blood flow. They also play a crucial role in the development of vascular diseases, such as atherosclerosis and aortic aneurysm formation. vSMCs display a remarkable high degree of plasticity. At present, the number of different vSMC phenotypes has only partially been characterized. By mapping vSMC phenotypes in detail and identifying triggers for phenotype switching, the relevance of the different phenotypes in vascular disease may be identified. Up until recently, vSMCs were classified as either contractile or dedifferentiated (ie, synthetic). However, single-cell RNA sequencing studies revealed such dedifferentiated arterial vSMCs to be highly diverse. Currently, no consensus exist about the number of vSMC phenotypes. Therefore, we reviewed the data from relevant single-cell RNA sequencing studies, and classified a total of 6 vSMC phenotypes. The central dedifferentiated vSMC type that we classified is the mesenchymal-like phenotype. Mesenchymal-like vSMCs subsequently seem to differentiate into fibroblast-like, macrophage-like, osteogenic-like, and adipocyte-like vSMCs, which contribute differentially to vascular disease. This phenotype switching between vSMCs requires the transcription factor KLF4 (Kruppel-like factor 4). Here, we performed an integrated analysis of the data about the recently identified vSMC phenotypes, their associated gene expression profiles, and previous vSMC knowledge to better understand the role of vSMC phenotype transitions in vascular pathology.

The role of TGF-β2 in cartilage development and diseases

Transforming growth factor-beta2 (TGF-β2) is recognized as a versatile cytokine that plays a vital role in regulation of joint development, homeostasis, and diseases, but its role as a biological mechanism is understood far less than that of its counterpart, TGF-β1. Cartilage as a load-resisting structure in vertebrates however displays a fragile performance when any tissue disturbance occurs, due to its lack of blood vessels, nerves, and lymphatics. Recent reports have indicated that TGF-β2 is involved in the physiological processes of chondrocytes such as proliferation, differentiation, migration, and apoptosis, and the pathological progress of cartilage such as osteoarthritis (OA) and rheumatoid arthritis (RA). TGF-β2 also shows its potent capacity in the repair of cartilage defects by recruiting autologous mesenchymal stem cells and promoting secretion of other growth factor clusters. In addition, some pioneering studies have already considered it as a potential target in the treatment of OA and RA. This article aims to summarize the current progress of TGF-β2 in cartilage development and diseases, which might provide new cues for remodelling of cartilage defect and intervention of cartilage diseases.

The parasite cytokine mimic Hp-TGM potently replicates the regulatory effects of TGF-β on murine CD4+ T cells

Transforming growth factor‐beta (TGF‐β) family proteins mediate many vital biological functions in growth, development and regulation of the immune system. TGF‐β itself controls immune homeostasis and inflammation, including conversion of naïve CD4⁺ T cells into Foxp3⁺ regulatory T cells (Tregs) in the presence of interleukin‐2 and T‐cell receptor ligands. The helminth parasite Heligmosomoides polygyrus exploits this pathway through a structurally novel TGF‐β mimic (Hp‐TGM), which binds to mammalian TGF‐β receptors and induces Tregs. Here, we performed detailed comparisons of Hp‐TGM with mammalian TGF‐β. Compared with TGF‐β, Hp‐TGM induced greater numbers of Foxp3⁺ Tregs (iTregs), with more intense Foxp3 expression. Both ligands upregulated Treg functional markers CD73, CD103 and programmed death‐ligand 1, but Hp‐TGM induced significantly higher CD39 expression than did TGF‐β. Interestingly, in contrast to canonical TGF‐β signaling through Smad2/3, Hp‐TGM stimulation was slower and more sustained. Gene expression profiles induced by TGF‐β and Hp‐TGM were remarkably similar, and both types of iTregs suppressed T‐cell responses in vitro and experimental autoimmune encephalomyelitis‐driven inflammation in vivo. In vitro, both types of iTregs were equally stable under inflammatory conditions, but Hp‐TGM‐induced iTregs were more stable in vivo during dextran sodium sulfate‐induced colitis, with greater retention of Foxp3 expression and lower conversion to a ROR‐γt⁺ phenotype. Altogether, results from this study suggest that the parasite cytokine mimic, Hp‐TGM, may deliver a qualitatively different signal to CD4⁺ T cells with downstream consequences for the long‐term stability of iTregs. These data highlight the potential of Hp‐TGM as a new modulator of T‐cell responses in vitro and in vivo.

The TGF-β Pathway: A Pharmacological Target in Hepatocellular Carcinoma?

Transforming Growth Factor-beta (TGF-β) superfamily members are essential for tissue homeostasis and consequently, dysregulation of their signaling pathways contributes to the development of human diseases. In the liver, TGF-β signaling participates in all the stages of disease progression from initial liver injury to hepatocellular carcinoma (HCC). During liver carcinogenesis, TGF-β plays a dual role on the malignant cell, behaving as a suppressor factor at early stages, but contributing to later tumor progression once cells escape from its cytostatic effects. Moreover, TGF-β can modulate the response of the cells forming the tumor microenvironment that may also contribute to HCC progression, and drive immune evasion of cancer cells. Thus, targeting the TGF-β pathway may constitute an effective therapeutic option for HCC treatment. However, it is crucial to identify biomarkers that allow to predict the response of the tumors and appropriately select the patients that could benefit from TGF-β inhibitory therapies. Here we review the functions of TGF-β on HCC malignant and tumor microenvironment cells, and the current strategies targeting TGF-β signaling for cancer therapy. We also summarize the clinical impact of TGF-β inhibitors in HCC patients and provide a perspective on its future use alone or in combinatorial strategies for HCC treatment.

Mesenchymal Stem Cell-Macrophage Crosstalk and Maintenance of Inflammatory Microenvironment Homeostasis

Macrophages are involved in almost every aspect of biological systems and include development, homeostasis and repair. Mesenchymal stem cells (MSCs) have good clinical application prospects due to their ability to regulate adaptive and innate immune cells, particularly macrophages, and they have been used successfully for many immune disorders, including inflammatory bowel disease (IBD), acute lung injury, and wound healing, which have been reported as macrophage-mediated disorders. In the present review, we focus on the interaction between MSCs and macrophages and summarize their methods of interaction and communication, such as cell-to-cell contact, soluble factor secretion, and organelle transfer. In addition, we discuss the roles of MSC-macrophage crosstalk in the development of disease and maintenance of homeostasis of inflammatory microenvironments. Finally, we provide optimal strategies for applications in immune-related disease treatments.

Cellular and molecular changes that predispose skin in chronic spinal cord injury to pressure ulcer formation

Patients with spinal cord injury have a predisposition to develop pressure ulcers. Specific characteristics of the patients' skin potentially involved have not yet been identified. The purpose of this investigation was to determine whether loss of neuronal control affects cellular and molecular homeostasis in the skin. Intact afflicted skin, wound edge of pressure ulcers, and control skin were analysed. Platelets, transforming growth factor‐β1, and activin A were identified by immunohistochemistry. Transforming growth factor‐β‐like activity was determined by bioassay, and gene expression by DNA microarray analysis or RT‐PCR. In afflicted skin, enhanced platelet extravasation was detected. Transforming growth factor‐β1 and activin A accumulated in the dermal‐epidermal junction zone. Transforming growth factor‐β‐like activity and activin A expression were increased in intact afflicted skin (compared to control skin) and were further enhanced in pressure ulcers. In vitro, activity was generated by fibroblast‐epithelial cell interactions, which also induced activin A. Thus, loss of neuronal control in spinal cord injury appears to trigger inappropriate wound healing processes in the patients' skin. Plasma leakage and increased transforming growth factor‐β‐like activity combined with shear forces potentially enhance the risk for pressure ulcer formation.

Regulation and Signaling of TGF-β Autoinduction

Cell signaling is a vital part of biological life. It helps coordinating various cellular processes including cell survival, cell growth, cell death, and cell interaction with the microenvironment and other cells. In general, cell signaling involves the attachment of signaling molecules known as ligands to specific receptors on cell surface, which then activate downstream events that dictate the cell's response. One of the most studied ligands is transforming growth factor-beta (TGF-β). TGF-β signaling is mainly mediated by suppressor of mothers against decapentaplegic (Smad) proteins, but it also interacts with other pathways such as the Ras and mitogen-activated protein kinase (MAPK) signaling pathways. Furthermore, TGF-β can have a dual role depending on the cellular and microenvironmental context, in which it can act as either a growth promoter or a growth inhibitor. It has been known that TGF-β can self-induce its ligand production, thereby prolonging and amplifying its effect on cells and their microenvironment. The aim of this review is to discuss the regulation and signaling of TGF-β autoinduction, which still remain to be elucidated. Several factors have been found to facilitate TGF-β autoinduction, which include the activator protein-1 (AP1) complex, Smad3-dependent signaling, and non-Smad signaling pathways. On the other hand, the LIM (Lin11, Isl-1 and Mec-3) domain only 7 (LMO7) protein can suppress TGF-β autoinduction by interfering with the activities of AP-1 and Smad3. Since TGF-β autoinduction is implicated in various pathological conditions, better understanding of its regulation and signaling can provide new directions for therapy.

The fibrillin microfibril/elastic fibre network: A critical extracellular supramolecular scaffold to balance skin homoeostasis

Supramolecular networks composed of fibrillins (fibrillin-1 and fibrillin-2) and associated ligands form intricate cellular microenvironments which balance skin homoeostasis and direct remodelling. Fibrillins assemble into microfibrils which are not only indispensable for conferring elasticity to the skin, but also control the bioavailability of growth factors targeted to the extracellular matrix architecture. Fibrillin microfibrils (FMF) represent the core scaffolds for elastic fibre formation, and they also decorate the surface of elastic fibres and form independent networks. In normal dermis, elastic fibres are suspended in a three-dimensional basket-like lattice of FMF intersecting basement membranes at the dermal-epidermal junction and thus conferring pliability to the skin. The importance of FMF for skin homoeostasis is illustrated by the clinical features caused by mutations in the human fibrillin genes (FBN1, FBN2), summarized as "fibrillinopathies." In skin, fibrillin mutations result in phenotypes ranging from thick, stiff and fibrotic skin to thin, lax and hyperextensible skin. The most plausible explanation for this spectrum of phenotypic outcomes is that FMF regulate growth factor signalling essential for proper growth and homoeostasis of the skin. Here, we will give an overview about the current understanding of the underlying pathomechanisms leading to fibrillin-dependent fibrosis as well as forms of cutis laxa caused by mutational inactivation of FMF-associated ligands.

Legumain promotes fibrogenesis in chronic pancreatitis via activation of transforming growth factor β1

Chronic pancreatitis (CP) is a major risk factor for pancreatic cancer; however, little is known about the pathogenic mechanisms underlying the development of CP. Legumain (Lgmn) has been linked to some chronic inflammatory diseases. The present study investigated the role of legumain in pancreatic fibrogenesis. We induced CP in wild type C57BL6 (WT), Lgmn-deficient (Lgmn^-/-), Lgmn^flox/flox and Lgmn^flox/flox × LysM^Cre mice by intraperitoneal injection of caerulein for 4 weeks. Pancreata were collected and analyzed by quantitative reverse transcription polymerase chain reaction, Western blotting, and histology. Pancreatic stellate cells and macrophages were isolated and studied using immunofluorescence, gelatin zymography, and enzyme-linked immunosorbent assay. The effects of inhibition of legumain were investigated in vivo by administration of the specific legumain inhibitor, RR-11a. Legumain was found to be upregulated in the serum and pancreatic tissues of mice with caerulein-induced CP. Mice with global and macrophage-specific legumain deficiency exhibited significantly reduced development of pancreatic fibrosis compared with control mice, based on pancreas size, histology, and expression of fibrosis-associated genes. Our results indicate that legumain promotes activation of pancreatic stellate cells and increases synthesis of extracellular matrix proteins via activation of matrix metalloproteinase-2(MMP-2), which hydrolyzes the transforming growth factor-β1 (TGF-β1) precursor to form active TGF-β1. Administration of RR-11a markedly attenuated pancreatic fibrosis in mice with CP. Deficiency or inhibition of legumain significantly reduces the severity of pancreatic fibrosis by suppressing activation of the TGF-β1 precursor. Our results highlight the potential of legumain as a novel therapeutic target for CP. KEY MESSAGES: • Legumain expression was markedly upregulated in CP mice. • Deletion of legumain attenuated pancreatic fibrosis in CP mice. • Legumain promotes fibrosis via MMP-2 activation, which hydrolyzed the TGF-β1 precursor to the active form. • Legumain is a potential therapeutic target for the management of CP.

The Simplest Protocol for Rapid and Long-Term Culture of Primary Epidermal Keratinocytes from Human and Mouse

Although mouse models have been used as an essential tool for studying the physiology and diseases of the skin, propagation of mouse primary epidermal keratinocytes remains challenging. In this chapter, we introduce the simplest, at least to our knowledge, protocol that enables long-term expansion of p63⁺ mouse epidermal keratinocytes in low Ca²⁺ media without the need of progenitor cell-purification steps or support by a feeder cell layer. Pharmacological inhibition of TGF-β signaling in crude preparations of mouse epidermis robustly increases proliferative capacity of p63⁺ epidermal progenitor cells, while preserving their ability to differentiate. Suppression of TGF-β signaling also permits p63⁺ epidermal keratinocytes to form macroscopically large clones in 3T3-J2 feeder cell co-culture. Suppression of TGF-β signaling also enhances the clonal growth of human keratinocytes in co-culture with a variety of feeder cells. This simple and efficient approach will not only facilitate the use of mouse models by providing p63⁺ primary epidermal keratinocytes in quantity but also significantly reduce the time needed for preparing the customized skin grafts in Green method.

Analytical Characterization of an Enzyme-Linked Immunosorbent Assay for the Measurement of Transforming Growth Factor β1 in Human Plasma

Background

The transforming growth factor β (TGF-β)–signaling pathway has emerged as a promising therapeutic target for many disease states including hepatocellular carcinoma (HCC). Because of the pleiotropic effects of this pathway, patient selection and monitoring may be important. TGF-β1 is the most prevalent isoform, and an assay to measure plasma levels of TGF-β1 would provide a rational biomarker to assist with patient selection. Therefore, the objective of this study was to analytically validate a colorimetric ELISA for the quantification of TGF-β1 in human plasma.

Methods

A colorimetric sandwich ELISA for TGF-β1 was analytically validated per Clinical and Laboratory Standards Institute protocols by assessment of precision, linearity, interfering substances, and stability. A reference range for plasma TGF-β1 was established for apparently healthy individuals and potential applicability was demonstrated in HCC patients.

Results

Precision was assessed for samples ranging from 633 to 10822 pg/mL, with total variance ranging from 28.4% to 7.2%. The assay was linear across the entire measuring range, and no interference of common blood components or similar molecules was observed. For apparently healthy individuals, the average TGF-β1 level was 1985 ± 1488 pg/mL compared to 4243 ± 2003 pg/mL for HCC patients. Additionally, the TGF-β1 level in plasma samples was demonstrated to be stable across all conditions tested, including multiple freeze–thaw cycles.

Conclusions

The ELISA described in this report is suitable for the quantification of TGF-β1 in human plasma and for investigational use in an approved clinical study.

TGF-β inhibitor therapy decreases fibrosis and stimulates cardiac improvement in a pre-clinical study of chronic Chagas' heart disease

TGF-β involvement in Chagas disease cardiomyopathy has been clearly demonstrated. The TGF-β signaling pathway is activated in the cardiac tissue of chronic phase patients and is associated with an increase in extracellular matrix protein expression. The aim of this study was to investigate the effect of GW788388, a selective inhibitor of TβR1/ALK5, on cardiac function in an experimental model of chronic Chagas' heart disease. To this end, C57BL/6 mice were infected with Trypanosoma cruzi (102 parasites from the Colombian strain) and treated orally with 3mg/kg GW788388 starting at 120 days post-infection (dpi), when 100% of the infected mice show cardiac damage, and following three distinct treatment schedules: i) single dose; ii) one dose per week; or iii) three doses per week during 30 days. The treatment with GW788388 improved several cardiac parameters: reduced the prolonged PR and QTc intervals, increased heart rate, and reversed sinus arrhythmia, and atrial and atrioventricular conduction disorders. At 180 dpi, 30 days after treatment interruption, the GW3x-treated group remained in a better cardiac functional condition. Further, GW788388 treatment reversed the loss of connexin-43 enriched intercellular plaques and reduced fibrosis of the cardiac tissue. Inhibition of the TGF-β signaling pathway reduced TGF-β/pSmad2/3, increased MMP-9 and Sca-1, reduced TIMP-1/TIMP-2/TIMP-4, and partially restored GATA-6 and Tbox-5 transcription, supporting cardiac recovery. Moreover, GW788388 administration did not modify cardiac parasite load during the infection but reduced the migration of CD3+ cells to the heart tissue. Altogether, our data suggested that the single dose schedule was not as effective as the others and treatment three times per week during 30 days seems to be the most effective strategy. The therapeutic effects of GW788388 are promising and suggest a new possibility to treat cardiac fibrosis in the chronic phase of Chagas' heart disease by TGF-β inhibitors.

Structural Adaptation in Its Orphan Domain Engenders Betaglycan with an Alternate Mode of Growth Factor Binding Relative to Endoglin

Betaglycan (BG) and endoglin (ENG), homologous co-receptors of the TGF-β family, potentiate the signaling activity of TGF-β2 and inhibin A, and BMP-9 and BMP-10, respectively. BG exists as monomer and forms 1:1 growth factor (GF) complexes, while ENG exists as a dimer and forms 2:1 GF complexes. Herein, the structure of the BG orphan domain (BG_O) reveals an insertion that blocks the region that the endoglin orphan domain (ENG_O) uses to bind BMP-9, preventing it from binding in the same manner. Using binding studies with domain-deleted forms of TGF-β and BG_O, as well as small-angle X-ray scattering data, BG_O is shown to bind its cognate GF in an entirely different manner compared with ENG_O. The alternative interfaces likely engender BG and ENG with the ability to selectively bind and target their cognate GFs in a unique temporal-spatial manner, without interfering with one another or other TGF-β family GFs.

Fibrillin microfibrils and proteases, key integrators of fibrotic pathways

Supramolecular networks composed of multi-domain ECM proteins represent intricate cellular microenvironments which are required to balance tissue homeostasis and direct remodeling. Structural deficiency in ECM proteins results in imbalances in ECM-cell communication resulting often times in fibrotic reactions. To understand how individual components of the ECM integrate communication with the cell surface by presenting growth factors or providing fine-tuned biomechanical properties is mandatory for gaining a better understanding of disease mechanisms in the quest for new therapeutic approaches. Here we provide an overview about what we can learn from inherited connective tissue disorders caused primarily by mutations in fibrillin-1 and binding partners as well as by altered ECM processing leading to defined structural changes and similar functional knock-in mouse models. We will utilize this knowledge to propose new molecular hypotheses which should be tested in future studies.

Macrophage-Derived Legumain Promotes Pulmonary Hypertension by Activating the MMP (Matrix Metalloproteinase)-2/TGF (Transforming Growth Factor)-β1 Signaling

Objective—

Macrophages participate in the pathogenesis of pulmonary arterial hypertension (PAH). Lgmn (Legumain), a newly discovered cysteine proteinase belonging to the C13 peptidase family, is primarily expressed in macrophages; however, its roles in PAH remain unknown.

Approach and Results—

Herein, Lgmn was upregulated in lung tissues of PAH mice subjected to hypoxia plus SU5416 and PAH rats challenged with monocrotaline. Global Lgmn ablation and macrophage-specific ablation alleviated PAH compared with wild-type mice, evident from a reduction in right ventricular systolic pressure, the ratio of the right ventricular wall to the left ventricular wall plus the septum, the pulmonary vascular media thickness, and pulmonary vascular muscularization. Increased expression of ECM (extracellular matrix) proteins was correlated with MMP (matrix metalloproteinase)-2 activation and TGF (transforming growth factor)-β1 signaling in the PAs. Although Lgmn did not affect inflammatory cell infiltration and PA smooth muscle cell proliferation, it drove increased the synthesis of ECM proteins via MMP-2 activation. MMP-2 hydrolyzed the TGF-β1 precursor to the active form. An Lgmn-specific inhibitor markedly ameliorated PAH. Clinically, serum Lgmn levels were closely associated with the severity of idiopathic PAH.

Conclusions—

Our results indicate that Lgmn inhibition could be an effective strategy for preventing or delaying PAH.

Reactive oxygen species: a volatile driver of field cancerization and metastasis

Field cancerization and metastasis are the leading causes for cancer recurrence and mortality in cancer patients. The formation of primary, secondary tumors or metastasis is greatly influenced by multifaceted tumor-stroma interactions, in which stromal components of the tumor microenvironment (TME) can affect the behavior of the cancer cells. Many studies have identified cytokines and growth factors as cell signaling molecules that aid cell to cell communication. However, the functional contribution of reactive oxygen species (ROS), a family of volatile chemicals, as communication molecules are less understood. Cancer cells and various tumor-associated stromal cells produce and secrete a copious amount of ROS into the TME. Intracellular ROS modulate cell signaling cascades that aid in the acquisition of several hallmarks of cancers. Extracellular ROS help to propagate, amplify, and effectively create a mutagenic and oncogenic field which facilitate the formation of multifoci tumors and act as a springboard for metastatic tumor cells. In this review, we summarize our current knowledge of ROS as atypical paracrine signaling molecules for field cancerization and metastasis. Field cancerization and metastasis are often discussed separately; we offer a model that placed these events with ROS as the focal instigating agent in a broader "seed-soil" hypothesis.

Lean on Me: Cell-Cell Interactions Release TGF-β for Local Consumption Only

A new study combines detailed biochemical characterization with whole-animal genetics and computational transcriptome data mining to reveal how the LRRC33 milieu molecule imposes an exquisite level of spatial control on TGF-β signaling in the CNS.

Cellular signaling in pseudoxanthoma elasticum: an update

Pseudoxanthoma elasticum is an autosomal recessive genodermatosis with variable expression, due to mutations in the ABCC6 or ENPP1 gene. It is characterized by elastic fiber mineralization and fragmentation, resulting in skin, eye and cardiovascular symptoms. Significant advances have been made in the last 20 years with respect to the phenotypic characterization and pathophysiological mechanisms leading to elastic fiber mineralization. Nonetheless, the substrates of the ABCC6 transporter - the main cause of PXE - remain currently unknown. Though the precise mechanisms linking the ABCC6 transporter to mineralization of the extracellular matrix are unclear, several studies have looked into the cellular consequences of ABCC6 deficiency in PXE patients and/or animal models. In this paper, we compile the evidence on cellular signaling in PXE, which seems to revolve mainly around TGF-βs, BMPs and inorganic pyrophosphate signaling cascades. Where conflicting results or fragmented data are present, we address these with novel signaling data. This way, we aim to better understand the up- and down-stream signaling of TGF-βs and BMPs in PXE and we demonstrate that ANKH deficiency can be an additional mechanism contributing to decreased serum PPi levels in PXE patients.

Promotion of Human Epidermal Keratinocyte Expansion in Feeder Cell Co-culture

Co-culture of human epidermal keratinocytes with mouse 3T3-J2 feeder cells, developed by Green and colleagues, has been used worldwide to generate skin autografts since the early 1980s. In addition, co-culture with 3T3-J2 cells has served as a fundamental tool in skin stem cell biology as it allows the evaluation of self-renewal capacity of epidermal stem cells. This chapter describes a recent improvement in the Green method to promote further the expansion of human epidermal keratinocytes utilizing a small-molecule inhibitor of TGF-β signaling. This new protocol enables more rapid expansion of human epidermal keratinocytes in co-culture with not only 3T3-J2 cells but also other feeder cells including human dermal fibroblasts and human preadipocytes, two major alternatives to 3T3-J2 cells, with a long-term goal of developing customized skin autografts.

Structural basis of latent TGF-β1 presentation and activation by GARP on human regulatory T cells

Transforming growth factor–β1 (TGF-β1) is one of very few cytokines produced in a latent form, requiring activation to exert any of its vastly diverse effects on development, immunity, and cancer. Regulatory T cells (Tregs) suppress immune cells within close proximity by activating latent TGF-β1 presented by GARP (glycoprotein A repetitions predominant) to integrin αVβ8 on their surface. We solved the crystal structure of GARP:latent TGF-β1 bound to an antibody that stabilizes the complex and blocks release of active TGF-β1. This finding reveals how GARP exploits an unusual medley of interactions, including fold complementation by the amino terminus of TGF-β1, to chaperone and orient the cytokine for binding and activation by αVβ8. Thus, this work further elucidates the mechanism of antibody-mediated blockade of TGF-β1 activation and immunosuppression by Tregs.

Connective tissue growth factor (CCN2) is a matricellular preproprotein controlled by proteolytic activation

Connective tissue growth factor (CTGF; now often referred to as CCN2) is a secreted protein predominantly expressed during development, in various pathological conditions that involve enhanced fibrogenesis and tissue fibrosis, and in several cancers and is currently an emerging target in several early-phase clinical trials. Tissues containing high CCN2 activities often display smaller degradation products of full-length CCN2 (FL-CCN2). Interpretation of these observations is complicated by the fact that a uniform protein structure that defines biologically active CCN2 has not yet been resolved. Here, using DG44 CHO cells engineered to produce and secrete FL-CCN2 and cell signaling and cell physiological activity assays, we demonstrate that FL-CCN2 is itself an inactive precursor and that a proteolytic fragment comprising domains III (thrombospondin type 1 repeat) and IV (cystine knot) appears to convey all biologically relevant activities of CCN2. In congruence with these findings, purified FL-CCN2 could be cleaved and activated following incubation with matrix metalloproteinase activities. Furthermore, the C-terminal fragment of CCN2 (domains III and IV) also formed homodimers that were ∼20-fold more potent than the monomeric form in activating intracellular phosphokinase cascades. The homodimer elicited activation of fibroblast migration, stimulated assembly of focal adhesion complexes, enhanced RANKL-induced osteoclast differentiation of RAW264.7 cells, and promoted mammosphere formation of MCF-7 mammary cancer cells. In conclusion, CCN2 is synthesized and secreted as a preproprotein that is autoinhibited by its two N-terminal domains and requires proteolytic processing and homodimerization to become fully biologically active.

Signaling Crosstalk of TGF-β/ALK5 and PAR2/PAR1: A Complex Regulatory Network Controlling Fibrosis and Cancer

Both signaling by transforming growth factor-β (TGF-β) and agonists of the G Protein-coupled receptors proteinase-activated receptor-1 (PAR1) and -2 (PAR2) have been linked to tissue fibrosis and cancer. Intriguingly, TGF-β and PAR signaling either converge on the regulation of certain matrix genes overexpressed in these pathologies or display mutual regulation of their signaling components, which is mediated in part through sphingosine kinases and sphingosine-1-phosphate and indicative of an intimate signaling crosstalk between the two pathways. In the first part of this review, we summarize the various regulatory interactions that have been discovered so far according to the organ/tissue in which they were described. In the second part, we highlight the types of signaling crosstalk between TGF-β on the one hand and PAR2/PAR1 on the other hand. Both ligand–receptor systems interact at various levels and by several mechanisms including mutual regulation of ligand–ligand, ligand–receptor, and receptor–receptor at the transcriptional, post-transcriptional, and receptor transactivation levels. These mutual interactions between PAR2/PAR1 and TGF-β signaling components eventually result in feed-forward loops/vicious cycles of matrix deposition and malignant traits that exacerbate fibrosis and oncogenesis, respectively. Given the crucial role of PAR2 and PAR1 in controlling TGF-β receptor activation, signaling, TGF-β synthesis and bioactivation, combining PAR inhibitors with TGF-β blocking agents may turn out to be more efficient than targeting TGF-β alone in alleviating unwanted TGF-β-dependent responses but retaining the beneficial ones.

BAMBI is a novel HIF1-dependent modulator of TGFβ-mediated disruption of cell polarity during hypoxia

Hypoxia and loss of cell polarity are common features of malignant carcinomas. Hypoxia-inducible factor 1 (HIF1) is the major regulator of cellular hypoxia response and mediates the activation of ∼300 genes. Increased HIF1 signaling is known to be associated with epithelial-mesenchymal transformation. Here, we report that hypoxia disrupts polarized epithelial morphogenesis of MDCK cells in a HIF1α-dependent manner by modulating the transforming growth factor-β (TGFβ) signaling pathway. Analysis of potential HIF1 targets in the TGFβ pathway identified the bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI), a transmembrane glycoprotein related to the type I receptors of the TGFβ family, whose expression was essentially lost in HIF1-depleted cells. Similar to what was observed in HIF1-deficient cells, BAMBI-depleted cells failed to efficiently activate TGFβ signaling and retained epithelial polarity during hypoxia. Taken together, we show that hypoxic conditions promote TGFβ signaling in a HIF1-dependent manner and BAMBI is identified in this pathway as a novel HIF1-regulated gene that contributes to hypoxia-induced loss of epithelial polarity.

Genetics of the extracellular matrix in aortic aneurysmal diseases

Aortic aneurysms are morbid conditions that can lead to rupture or dissection and are categorized as thoracic (TAA) or abdominal aortic aneurysms (AAA) depending on their location. While AAA shares overlapping risk factors with atherosclerotic cardiovascular disease, TAA exhibits strong heritability. Human genetic studies in the past two decades have successfully identified numerous genes involved in both familial and sporadic forms of aortic aneurysm. In this review we will discuss the genetic basis of aortic aneurysm, focusing on the extracellular matrix and how insights from these studies have informed our understanding of human biology and disease pathogenesis.

A Novel TGFβ Trap Blocks Chemotherapeutics-Induced TGFβ1 Signaling and Enhances Their Anticancer Activity in Gynecologic Cancers

Purpose: We investigated the mechanisms of how TGFβ pathway is activated by chemotherapeutics and whether a novel TGFβ trap called RER can block chemotherapeutics-induced TGFβ pathway activation and enhance their antitumor activity in gynecologic cancer.Patients and Methods: An unbiased bioinformatic analysis of differentially expressed genes in 31 ovarian cases due to chemotherapy was used to identify altered master regulators. Phosphorylated Smad2 was determined in 30 paired cervical cancer using IHC. Furthermore, the effects of chemotherapeutics on TGFβ signaling and function, and the effects of RER on chemotherapy-induced TGFβ signaling were determined in gynecologic cancer cells.Results: Chemotherapy-induced transcriptome alteration in ovarian cancer was significantly associated with TGFβ signaling activation. Chemotherapy was found to activate TGFβ signaling as indicated by phosphorylated Smad2 in paired cervical tumor samples (pre- and post-chemotherapy). Similar to TGFβ1, chemotherapeutics were found to stimulate Smad2/3 phosphorylation, cell migration, and markers related to epithelial-mesenchymal transition (EMT) and cancer stem cells (CSC). These TGFβ-like effects were due to the stimulation of TGFβ1 expression and secretion, and could all be abrogated by TGFβ inhibitors including a novel TGFβ trap protein called RER both in vitro and in vivo Importantly, combination treatment with RER and cisplatin showed a higher tumor inhibitory activity than either agent alone in a xenograft model of ovarian cancer.Conclusions: Chemotherapeutics can stimulate TGFβ1 production and consequently enhance TGFβ signaling, EMT, and CSC features resulting in reduced chemo-sensitivity. Combination therapy with a TGFβ inhibitor should alleviate this unintended side effect of chemotherapeutics and enhance their therapeutic efficacy. Clin Cancer Res; 24(12); 2780-93. ©2018 AACR.

A novel highly potent trivalent TGF-β receptor trap inhibits early-stage tumorigenesis and tumor cell invasion in murine Pten-deficient prostate glands

The effects of transforming growth factor beta (TGF-β) signaling on prostate tumorigenesis has been shown to be strongly dependent on the stage of development, with TGF-β functioning as a tumor suppressor in early stages of disease and as a promoter in later stages. To study in further detail the paradoxical tumor-suppressive and tumor-promoting roles of the TGF-β pathway, we investigated the effect of systemic treatment with a TGF-β inhibitor on early stages of prostate tumorigenesis. To ensure effective inhibition, we developed and employed a novel trivalent TGF-β receptor trap, RER, comprised of domains derived from the TGF-β type II and type III receptors. This trap was shown to completely block TβRII binding, to antagonize TGF-β1 and TGF-β3 signaling in cultured epithelial cells at low picomolar concentrations, and it showed equal or better anti-TGF-β activities than a pan TGF-β neutralizing antibody and a TGF-β receptor I kinase inhibitor in various prostate cancer cell lines. Systemic administration of RER inhibited prostate tumor cell proliferation as indicated by reduced Ki67 positive cells and invasion potential of tumor cells in high grade prostatic intraepithelial neoplasia (PIN) lesions in the prostate glands of Pten conditional null mice. These results provide evidence that TGF-β acts as a promoter rather than a suppressor in the relatively early stages of this spontaneous prostate tumorigenesis model. Thus, inhibition of TGF-β signaling in early stages of prostate cancer may be a novel therapeutic strategy to inhibit the progression as well as the metastatic potential in patients with prostate cancer.

Immunoregulatory functions and the therapeutic implications of GARP-TGF-β in inflammation and cancer

GARP (glycoprotein-A repetitions predominant) is a type I transmembrane cell surface docking receptor for latent transforming growth factor-β (TGF-β) that is abundantly expressed on regulatory T lymphocytes and platelets. GARP regulates the availability of membrane-bound latent TGF-β and modulates its activation. For this reason, GARP expression on immune and non-immune cells is involved in maintaining peripheral tolerance. It plays an important role in preventing inflammatory diseases such as allergy and graft versus host disease (GvHD). GARP is also frequently hijacked by cancer cells to promote oncogenesis. This review summarizes the most important features of GARP biology described to date including gene regulation, protein expression and mechanism in activating latent TGF-β, and the function of GARP in regulatory T cell biology and peripheral tolerance, as well as GARP’s increasingly recognized roles in platelet-mediated cancer immune evasion. The promise for GARP-targeted strategy as a novel immunotherapy of cancer is also highlighted.

Quantitation of TGF-β proteins in mouse tissues shows reciprocal changes in TGF-β1 and TGF-β3 in normal vs neoplastic mammary epithelium

Transforming growth factor-βs (TGF-βs) regulate tissue homeostasis, and their expression is perturbed in many diseases. The three isoforms (TGF-β1, -β2, and -β3) have similar bioactivities in vitro but show distinct activities in vivo. Little quantitative information exists for expression of TGF-β isoform proteins in physiology or disease. We developed an optimized method to quantitate protein levels of the three isoforms, using a Luminex® xMAP®-based multianalyte assay following acid-ethanol extraction of tissues. Analysis of multiple tissues and plasma from four strains of adult mice showed that TGF-β1 is the predominant isoform with TGF-β2 being ~10-fold lower. There were no sex-specific differences in isoform expression, but some tissues showed inter-strain variation, particularly for TGF-β2. The only adult tissue expressing appreciable TGF-β3 was the mammary gland, where its levels were comparable to TGF-β1. In situ hybridization showed the luminal epithelium as the major source of all TGF-β isoforms in the normal mammary gland. TGF-β1 protein was 3-8-fold higher in three murine mammary tumor models than in normal mammary gland, while TGF-β3 protein was 2-3-fold lower in tumors than normal tissue, suggesting reciprocal regulation of these isoforms in mammary tumorigenesis.

TGF-β family co-receptor function and signaling

Transforming growth factor-β (TGF-β) family members, which include TGF-βs, activins and bone morphogenetic proteins, are pleiotropic cytokines that elicit cell type-specific effects in a highly context-dependent manner in many different tissues. These secreted protein ligands signal via single-transmembrane Type I and Type II serine/threonine kinase receptors and intracellular SMAD transcription factors. Deregulation in signaling has been implicated in a broad array of diseases, and implicate the need for intricate fine tuning in cellular signaling responses. One important emerging mechanism by which TGF-β family receptor signaling intensity, duration, specificity and diversity are regulated and/or mediated is through cell surface co-receptors. Here, we provide an overview of the co-receptors that have been identified for TGF-β family members. While some appear to be specific to TGF-β family members, others are shared with other pathways and provide possible ways for signal integration. This review focuses on novel functions of TGF-β family co-receptors, which continue to be discovered.

ALK1 signaling in development and disease: new paradigms

Activin A receptor like type 1 (ALK1) is a transmembrane serine/threonine receptor kinase in the transforming growth factor-beta receptor family that is expressed on endothelial cells. Defects in ALK1 signaling cause the autosomal dominant vascular disorder, hereditary hemorrhagic telangiectasia (HHT), which is characterized by development of direct connections between arteries and veins, or arteriovenous malformations (AVMs). Although previous studies have implicated ALK1 in various aspects of sprouting angiogenesis, including tip/stalk cell selection, migration, and proliferation, recent work suggests an intriguing role for ALK1 in transducing a flow-based signal that governs directed endothelial cell migration within patent, perfused vessels. In this review, we present an updated view of the mechanism of ALK1 signaling, put forth a unified hypothesis to explain the cellular missteps that lead to AVMs associated with ALK1 deficiency, and discuss emerging roles for ALK1 signaling in diseases beyond HHT.

A structurally distinct TGF-β mimic from an intestinal helminth parasite potently induces regulatory T cells

Helminth parasites defy immune exclusion through sophisticated evasion mechanisms, including activation of host immunosuppressive regulatory T (Treg) cells. The mouse parasite Heligmosomoides polygyrus can expand the host Treg population by secreting products that activate TGF-β signalling, but the identity of the active molecule is unknown. Here we identify an H. polygyrus TGF-β mimic (Hp-TGM) that replicates the biological and functional properties of TGF-β, including binding to mammalian TGF-β receptors and inducing mouse and human Foxp3⁺ Treg cells. Hp-TGM has no homology with mammalian TGF-β or other members of the TGF-β family, but is a member of the complement control protein superfamily. Thus, our data indicate that through convergent evolution, the parasite has acquired a protein with cytokine-like function that is able to exploit an endogenous pathway of immunoregulation in the host.

Heligmosomoides polygyrus can activate mammalian TGF-β signalling pathways, but how it does so is not known. Here the authors identify and isolate a H. polygyrus TFG-β mimic that can bind both mammalian TGF-β receptor subunits, activate Smad signalling and generate inducible regulatory T cells.

Blocking immunosuppression by human Tregs in vivo with antibodies targeting integrin αVβ8

Human regulatory T cells (Tregs) suppress other T cells by converting the latent, inactive form of TGF-β1 into active TGF-β1. In Tregs, TGF-β1 activation requires GARP, a transmembrane protein that binds and presents latent TGF-β1 on the surface of Tregs stimulated through their T cell receptor. However, GARP is not sufficient because transduction of GARP in non-Treg T cells does not induce active TGF-β1 production. RGD-binding integrins were shown to activate TGF-β1 in several non-T cell types. Here we show that αVβ8 dimers are present on stimulated human Tregs but not in other T cells, and that antibodies against αV or β8 subunits block TGF-β1 activation in vitro. We also show that αV and β8 interact with GARP/latent TGF-β1 complexes in human Tregs. Finally, a blocking antibody against β8 inhibited immunosuppression by human Tregs in a model of xenogeneic graft-vs.-host disease induced by the transfer of human T cells in immunodeficient mice. These results show that TGF-β1 activation on the surface of human Tregs implies an interaction between the integrin αVβ8 and GARP/latent TGF-β1 complexes. Immunosuppression by human Tregs can be inhibited by antibodies against GARP or against the integrin β8 subunit. Such antibodies may prove beneficial against cancer or chronic infections.