Targeted delivery of a novel group of site-directed transglutaminase inhibitors to the liver using liposomes: a new approach for the potential treatment of liver fibrosis

Pirfenidone alleviates fibrosis by acting on tumour-stroma interplay in pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a malignancy with a 5-year survival rate of 12%. The abundant mesenchyme is partly responsible for the malignancy. The antifibrotic therapies have gained attention in recent research. However, the role of pirfenidone, an FDA-approved drug for idiopathic pulmonary fibrosis, remains unclear in PDAC.

METHODS

Data from RNA-seq of patient-derived xenograft (PDX) models treated with pirfenidone were integrated using bioinformatics tools to identify the target of cell types and genes. Using confocal microscopy, qRT-PCR and western blotting, we validated the signalling pathway in tumour cells to regulate the cytokine secretion. Further cocultured system demonstrated the interplay to regulate stroma fibrosis. Finally, mouse models demonstrated the potential of pirfenidone in PDAC.

RESULTS

Pirfenidone can remodulate multiple biological pathways, and exerts an antifibrotic effect through inhibiting the secretion of PDGF-bb from tumour cells by downregulating the TGM2/NF-kB/PDGFB pathway. Thus, leading to a subsequent reduction in collagen X and fibronectin secreted by CAFs. Moreover, the mice orthotopic pancreatic tumour models demonstrated the antifibrotic effect and potential to sensitise gemcitabine.

CONCLUSIONS

Pirfenidone may alter the pancreatic milieu and alleviate fibrosis through the regulation of tumour-stroma interactions via the TGM2/NF-kB/PDGFB signalling pathway, suggesting potential therapeutic benefits in PDAC management.

Cell-Impermeable Inhibitors Confirm That Intracellular Human Transglutaminase 2 Is Responsible for the Transglutaminase-Associated Cancer Phenotype

Transglutaminase 2 (TG2) is a multifunctional enzyme primarily responsible for crosslinking proteins. Ubiquitously expressed in humans, TG2 can act either as a transamidase by crosslinking two substrates through formation of an Nε(ɣ-glutaminyl)lysine bond or as an intracellular G-protein. These discrete roles are tightly regulated by both allosteric and environmental stimuli and are associated with dramatic changes in the conformation of the enzyme. The pleiotropic nature of TG2 and multi-faceted activities have resulted in TG2 being implicated in numerous disease pathologies including celiac disease, fibrosis, and cancer. Targeted TG2 therapies have not been selective for subcellular localization, such that currently no tools exist to selectively target extracellular over intracellular TG2. Herein, we have designed novel TG2-selective inhibitors that are not only highly potent and irreversible, but also cell impermeable, targeting only extracellular TG2. We have also further derivatized the scaffold to develop probes that are intrinsically fluorescent or bear an alkyne handle, which target both intra- and extracellular TG2, in order to facilitate cellular labelling and pull-down assays. The fluorescent probes were internalized and imaged in cellulo, and provide the first implicit experimental evidence that by comparison with their cell-impermeable analogues, it is specifically intracellular TG2, and presumably its G-protein activity, that contributes to transglutaminase-associated cancer progression.

Collagen crosslinking: effect on structure, mechanics and fibrosis progression

Biophysical properties of extracellular matrix (ECM), such as matrix stiffness, viscoelasticity and matrix fibrous structure, are emerging as important factors that regulate progression of fibrosis and other chronic diseases. The biophysical properties of the ECM can be rapidly and profoundly regulated by crosslinking reactions in enzymatic or non-enzymatic manners, which further alter the cellular responses and drive disease progression. In-depth understandings of crosslinking reactions will be helpful to reveal the underlying mechanisms of fibrosis progression and put forward new therapeutic targets, whereas related reviews are still devoid. Here, we focus on the main crosslinking mechanisms that commonly exist in a plethora of chronic diseases (e.g. fibrosis, cancer, osteoarthritis) and summarize current understandings including the biochemical reaction, the effect on ECM properties, the influence on cellular behaviors, and related studies in disease model establishment. Potential pharmaceutical interventions targeting the crosslinking process and relevant clinical studies are also introduced. Limitations of pharmaceutical development may be due to the lack of systemic investigations related to the influence on crosslinking mechanism from micro to macro level, which are discussed in the last section. We also propose the unclarified questions regarding crosslinking mechanisms and potential challenges in crosslinking-targeted therapeutics development.

Cross-Linked Multimeric Pro-Peptides of Type III Collagen (PC3X) in Hepatocellular Carcinoma - A Biomarker That Provides Additional Prognostic Value in AFP Positive Patients

Purpose

Non-invasive biomarkers for diagnosing and prognosing hepatocellular carcinoma (HCC) are urgently needed. Cirrhosis is present in 80–90% of HCC patients. Cirrhosis is characterized by deposition and cross-linking of collagens that have crucial roles in HCC initiation and progression. We evaluated circulating cross-linked pro-peptides of type III collagen (PC3X) as a diagnostic and prognostic biomarker for HCC.

Patients and Methods

PC3X was measured by ELISA in plasma from patients with HCC (n=79), cirrhosis (n=86), non-cirrhotic hepatitis-B infection (n=74) and from healthy controls (n=44). PC3X was compared to the liver fibrosis marker PRO-C3 and the HCC tumor-cell derived marker alpha-fetoprotein (AFP). Diagnostic and prognostic potential was evaluated by AUROC and by calculating hazard ratios (HR) for progression-free survival (PFS) and overall survival (OS).

Results

PC3X, PRO-C3 and AFP were significantly elevated in patients with HCC compared to other liver diseases and healthy controls (p=0.0002, p<0.0001). In patients with normal AFP (<20 IU/mL), PC3X and PRO-C3 separated HCC from cirrhosis with an AUROC of 0.72 and 0.68, respectively. High PC3X and AFP predicted for poor PFS (HR_PC3X=1.80, p=0.032; HR_AFP=1.70, p=0.031) and OS (HR_PC3X=2.12, p=0.024; HR_AFP=2.55; p=0.003), whereas PRO-C3 did not (PFS: HR=1.19, p=0.059 and OS: HR=1.12, p=0.324). PC3X was independent of AFP (PFS: HR=1.74, p=0.045 and OS: HR=2.21, p=0.018) and combining the two improved prognostic value (PFS: HR=2.66, p=0.004 and OS: HR=5.86, p<0.0001).

Conclusion

PC3X is associated with HCC independent of AFP and provides diagnostic and prognostic value for HCC patients. If validated, this suggests that PC3X has biomarker potential for HCC.

Targeting extracellular matrix stiffness to attenuate disease: From molecular mechanisms to clinical trials

Tissues stiffen during aging and during the pathological progression of cancer, fibrosis, and cardiovascular disease. Extracellular matrix stiffness is emerging as a prominent mechanical cue that precedes disease and drives its progression by altering cellular behaviors. Targeting extracellular matrix mechanics, by preventing or reversing tissue stiffening or interrupting the cellular response, is a therapeutic approach with clinical potential. Major drivers of changes to the mechanical properties of the extracellular matrix include phenotypically converted myofibroblasts, transforming growth factor β (TGFβ), and matrix cross-linking. Potential pharmacological interventions to overcome extracellular matrix stiffening are emerging clinically. Aside from targeting stiffening directly, alternative approaches to mitigate the effects of increased matrix stiffness aim to identify and inhibit the downstream cellular response to matrix stiffness. Therapeutic interventions that target tissue stiffening are discussed in the context of their limitations, preclinical drug development efforts, and clinical trials.

Structure-Activity Relationships of Potent, Targeted Covalent Inhibitors That Abolish Both the Transamidation and GTP Binding Activities of Human Tissue Transglutaminase

Human tissue transglutaminase (hTG2) is a multifunctional enzyme. It is primarily known for its calcium-dependent transamidation activity that leads to formation of an isopeptide bond between glutamine and lysine residues found on the surface of proteins, but it is also a GTP binding protein. Overexpression and unregulated hTG2 activity have been associated with numerous human diseases, including cancer stem cell survival and metastatic phenotype. Herein, we present a series of targeted covalent inhibitors (TCIs) based on our previously reported Cbz-Lys scaffold. From this structure-activity relationship (SAR) study, novel irreversible inhibitors were identified that block the transamidation activity of hTG2 and allosterically abolish its GTP binding ability with a high degree of selectivity and efficiency (k_inact/K_I > 10⁵ M^-1 min^-1). One optimized inhibitor (VA4) was also shown to inhibit epidermal cancer stem cell invasion with an EC₅₀ of 3.9 μM, representing a significant improvement over our previously reported "hit" NC9.

Inhibitors of tissue transglutaminase

Tissue transglutaminase (TG2) catalyzes the cross-linking of proteins by the formation of isopeptide bonds between glutamine (Gln) and lysine (Lys) side chains. Although TG2 is essential for the stabilization of the extracellular matrix, its unregulated activity has been implicated in celiac disease, fibrosis, and cancer metastasis, among other disorders. Given the importance and range of TG2-related pathologies, recent work has focused on the development of potent and selective inhibitors against TG2. In this review, we present the latest and most noteworthy irreversible and reversible inhibitors of TG2, and offer perspectives for the design of future inhibitors, in the hope that lead compounds with therapeutic potential may soon be discovered.

Pathogenesis of liver cirrhosis

Liver cirrhosis is the final pathological result of various chronic liver diseases, and fibrosis is the precursor of cirrhosis. Many types of cells, cytokines and miRNAs are involved in the initiation and progression of liver fibrosis and cirrhosis. Activation of hepatic stellate cells (HSCs) is a pivotal event in fibrosis. Defenestration and capillarization of liver sinusoidal endothelial cells are major contributing factors to hepatic dysfunction in liver cirrhosis. Activated Kupffer cells destroy hepatocytes and stimulate the activation of HSCs. Repeated cycles of apoptosis and regeneration of hepatocytes contribute to pathogenesis of cirrhosis. At the molecular level, many cytokines are involved in mediation of signaling pathways that regulate activation of HSCs and fibrogenesis. Recently, miRNAs as a post-transcriptional regulator have been found to play a key role in fibrosis and cirrhosis. Robust animal models of liver fibrosis and cirrhosis, as well as the recently identified critical cellular and molecular factors involved in the development of liver fibrosis and cirrhosis will facilitate the development of more effective therapeutic approaches for these conditions.

Liposomal oxymatrine in hepatic fibrosis treatment: formulation, in vitro and in vivo assessment

The aim was to develop a liposomal oxymatrine conjugating D-alpha tocopheryl polyethylene glycol 1000 succinate (OMT-LIP) for enhanced therapeutics of hepatic fibrosis. OMT-LIP was prepared using the remote loading method. The influences of formulation compositions on the encapsulation efficiency of OMT-LIP were investigated. Mean particle size, zeta potential, morphology, in vitro release, fibrotic liver targeting, and therapeutics of OMT-LIP were thoroughly assessed. The intraliposomal buffer composition and concentration, extraliposomal phase composition and pH, types of phospholipid, lipid molar ratio composition, and theoretical drug loading are crucial factors to entrap OMT into liposomes. The optimum OMT-LIP presented spherically unilamellar microstructures with entrapment efficiency of 79.7 ± 3.9%, mean particle size of 121.6 ± 52.9 nm, and zeta potential of -5.87 mV. OMT-LIP significantly increased the accumulation of OMT in the fibrotic liver with an 11.5-fold greater AUC than OMT solution in the dimethylnitrosamine (DMN)-induced hepatic fibrosis animals. OMT-LIP could be a potential strategy to improve treatment outcomes for hepatic fibrosis, showing the protective effects to mice given CCl4 and the enhanced therapeutics to mice with either DMN or CCl4-induced hepatic fibrosis.

Indwelling catheters and medical implants with FXIIIa inhibitors: A novel approach to the treatment of catheter and medical device-related infections

Central venous catheters (CVCs) are being utilized with increasing frequency in intensive care and general medical wards. In spite of the extensive experience gained in their application, CVCs are related to the long-term risks of catheter sheath formation, infection, and thrombosis (of the catheter or vessel itself) during catheterization. Such CVC-related-complications are associated with increased morbidity, mortality, duration of hospitalization, and medical care cost [1]. The present study incorporates a novel group of Factor XIIIa (FXIIIa, plasma transglutaminase) inhibitors into a lubricious silicone elastomer in order to generate an optimized drug delivery system whereby a secondary sustained drug release profile occurs following an initial burst release for catheters and other medical devices. We propose that the incorporation of FXIIIa inhibitors into catheters, stents, and other medical implant devices would reduce the incidence of catheter sheath formation, thrombotic occlusion, and associated staphylococcal infection. This technique could be used as a local delivery system for extended release with an immediate onset of action for other poorly aqueous soluble compounds.

The role of lipid geometry in designing liposomes for the solubilisation of poorly water soluble drugs

Liposomes are well recognised for their ability to improve the delivery of a range of drugs. More commonly they are applied for the delivery of water-soluble drugs, but given their structural attributes, they can also be employed as solubilising agents for low solubility drugs as well as drug targeting agents. To further explore the potential of liposomes as solubilising agents, we have investigated the role of bilayer packaging in promoting drug solubilisation in liposome bilayers. The effect of alkyl chain length and symmetry was investigated to consider if using 'mis-matched' phospholipids could create 'voids' within the bilayers, and enhance bilayer loading capacity. Lipid packing was investigated using Langmuir studies, which demonstrated that increasing the alkyl chain length enhanced lipid packing, with condensed monolayers forming, whilst asymmetric lipids formed less condensed monolayers. However, this more open packing did not translate into improved drug loading, with the longer chain, condensed bilayers formed from long-chain, saturated lipids offering higher drug loading capacity. These studies demonstrate that liposomes formulated from longer chain, saturated lipids offer enhanced solubilisation capacity. However the molecular size, rather than lipophilicity, of the drug to be incorporated was also a key factor dominating bilayer incorporation efficiency.