Inhibition of the LOX enzyme family members with old and new ligands. Selectivity analysis revisited

Unveiling the role of extracellular matrix elements and regulators in shaping ovarian cancer growth and metastasis

Epithelial ovarian cancer (EOC) progression is determined by numerous intracellular interactions and the interplay between malignant cells, normal cells, and the tumor acellular microenvironment, formed largely by the extracellular matrix (ECM). The structure and biochemical functioning of various ECM components, along with the activity of agents that regulate ECM remodeling, impact the disease's expansion (adhesion, proliferation, invasion), spread, and response to therapy. It is important to note that the involvement of ECM components and their regulators in the progression of EOC is bidirectional and distinctly depends on a particular tissue context. In certain situations, certain components of the ECM enhance the activity of cancer cells, but in other scenarios, they suppress it. In this review, we summarize the newest knowledge regarding diverse aspects of ECM engagement in EOC pathophysiology and chemotherapy. Moreover, we delineate conditions that exacerbate the pro-cancerous properties of ECM, including diabetes-associated glycation, aging, and cellular senescence. We also explore methods to therapeutically alter the properties of the ECM, which could be beneficial in ovarian cancer prevention and treatment.

Structural determinants of tendon multiscale mechanics and their sensitivity to mechanical stimulation during development in an embryonic chick model

There is an abrupt increase in the multiscale mechanical properties and load-bearing capabilities of tendon during development. While prior work has identified numerous changes that occur within the collagenous structure during this developmental period, the primary structural elements that give rise to this abrupt increase in mechanical functionality, and their mechanobiological sensitivity, remain unclear. To address this knowledge gap, we used a shear lag model along with ultrastructural imaging, biochemical/thermodynamic assays, and multiscale mechanical testing to investigate the dynamic structure-function relationships during late-stage embryonic chick development and to establish their sensitivity to mechanical stimulation. Mechanical testing and modeling suggested that the rapid increase in multiscale mechanics can be explained by increases in fibril length, intrafibrillar crosslinking, and fibril area fraction. To partially test this, we inhibited collagen crosslinking during development and observed a drastic reduction in multiscale mechanical behavior that was explained by a reduction in both fibril modulus and length. Using muscle paralysis to investigate mechanosensitivity, we observed a significantly impaired multiscale mechanical response despite minimal changes in fibril diameter and fibril area fraction. Additionally, the shear lag model found a trend toward lower fibril lengths with paralysis and experimental data found decreased crosslinking and fibril modulus values following flaccid paralysis. Together, these data suggest that both intrafibrillar crosslink formation and fibril elongation are critical to the formation of load-bearing capabilities in tenogenesis and are sensitive to mechanical loading. These findings provide critical insights into the biological and structural mechanisms that give rise to tensile load-bearing soft tissue. STATEMENT OF SIGNIFICANCE: Despite prior work investigating the structural and mechanical changes that occur during tendon development, there has not been a comprehensive analysis of how these simultaneous changes in structure and function are connected. In this study, we performed a comprehensive battery of mechanical and structural assessments of embryonic chick tendons and input these data into a shear lag model to estimate the individual importance of each structural change to the tendon mechanical properties. Additionally, we inhibited muscle activity in the embryos to evaluate the impact of mechanical stimulation on these evolving structure-function relationships during tendon development. These data provide insight into the primary structural elements that produce the tensile load-bearing capabilities of tendon, which will inform efforts to produce tissue engineered tendon replacements.

Roles of Lysyl oxidases (LOX(L)) in pathologic calcification

Calcification of tissues involves the formation and deposition of calcium-containing crystals in the extracellular matrix (ECM). While this process is normal in bones, it becomes pathological when it occurs in cardiovascular and musculoskeletal soft tissues. Pathological calcification (PC) triggers detrimental pathways such as inflammation and oxidative stress, contributing to tissue damage and dysregulated tissue biomechanics, ultimately leading to severe complications and even death. The underlying mechanisms of PC remain elusive. Emerging evidence suggests a significant role of lysyl oxidases (LOX(L)) in PC. LOX(L) are a group of five enzymes involved in collagen cross-linking and ECM maturation. Beyond their classical role in bone mineralization, recent investigations propose new non-classical roles for LOX(L) that could be relevant in PC. In this review, we analyzed and summarized the functions of LOX(L) in cardiovascular and musculoskeletal PC, highlighting their deleterious roles in most studies. To date, specific inhibitors targeting LOX(L) isoforms are under development. New therapeutic tools targeting LOX(L) are warranted in PC and must avoid adverse effects on physiological bone mineralization.

A highly potent bi-thiazole inhibitor of LOX rewires collagen architecture and enhances chemoresponse in triple-negative breast cancer

Lysyl oxidase (LOX) is upregulated in highly stiff aggressive tumors, correlating with metastasis, resistance, and worse survival; however, there are currently no potent, safe, and orally bioavailable small molecule LOX inhibitors to treat these aggressive desmoplastic solid tumors in clinics. Here we discovered bi-thiazole derivatives as potent LOX inhibitors by robust screening of drug-like molecules combined with cell/recombinant protein-based assays. Structure-activity relationship analysis identified a potent lead compound (LXG6403) with ∼3.5-fold specificity for LOX compared to LOXL2 while not inhibiting LOXL1 with a competitive, time- and concentration-dependent irreversible mode of inhibition. LXG6403 shows favorable pharmacokinetic properties, globally changes ECM/collagen architecture, and reduces tumor stiffness. This leads to better drug penetration, inhibits FAK signaling, and induces ROS/DNA damage, G1 arrest, and apoptosis in chemoresistant triple-negative breast cancer (TNBC) cell lines, PDX organoids, and in vivo. Overall, our potent and tolerable bi-thiazole LOX inhibitor enhances chemoresponse in TNBC, the deadliest breast cancer subtype.

β-Aminopropionitrile Induces Distinct Pathologies in the Ascending and Descending Thoracic Aortic Regions of Mice

BACKGROUND

β-aminopropionitrile (BAPN) is a pharmacological inhibitor of LOX (lysyl oxidase) and LOXLs (LOX-like proteins). Administration of BAPN promotes aortopathies, although there is a paucity of data on experimental conditions to generate pathology. The objective of this study was to define experimental parameters and determine whether equivalent or variable aortopathies were generated throughout the aortic tree during BAPN administration in mice.

METHODS

BAPN was administered in drinking water for a period ranging from 1 to 12 weeks. The impacts of BAPN were first assessed with regard to BAPN dose, and mouse strain, age, and sex. BAPN-induced aortic pathological characterization was conducted using histology and immunostaining. To investigate the mechanistic basis of regional heterogeneity, the ascending and descending thoracic aortas were harvested after 1 week of BAPN administration before the appearance of overt pathology.

RESULTS

BAPN-induced aortic rupture predominantly occurred or originated in the descending thoracic aorta in young C57BL/6J or N mice. No apparent differences were found between male and female mice. For mice surviving 12 weeks of BAPN administration, profound dilatation was consistently observed in the ascending region, while there were more heterogeneous changes in the descending thoracic region. Pathological features were distinct between the ascending and descending thoracic regions. Aortic pathology in the ascending region was characterized by luminal dilatation and elastic fiber disruption throughout the media. The descending thoracic region frequently had dissections with false lumen formation, collagen deposition, and remodeling of the wall surrounding the false lumen. Cells surrounding the false lumen were predominantly positive for α-SMA (α-smooth muscle actin). One week of BAPN administration compromised contractile properties in both regions equivalently, and RNA sequencing did not show obvious differences between the 2 aortic regions in smooth muscle cell markers, cell proliferation markers, and extracellular components.

CONCLUSIONS

BAPN-induced pathologies show distinct, heterogeneous features within and between ascending and descending aortic regions in mice.

β-aminopropionitrile Induces Distinct Pathologies in the Ascending and Descending Thoracic Aortic Regions of Mice

BACKGROUND

β-aminopropionitrile (BAPN) is a pharmacological inhibitor of lysyl oxidase and lysyl oxidase-like proteins. Administration of BAPN promotes aortopathies, although there is a paucity of data on experimental conditions to generate pathology. The objective of this study was to define experimental parameters and determine whether equivalent or variable aortopathies were generated throughout the aortic tree during BAPN administration in mice.

METHODS

BAPN was administered in drinking water for a period ranging from 1 to 12 weeks. The impacts of BAPN were first assessed with regard to dose, strain, age, and sex. BAPN-induced aortic pathological characterization was conducted using histology and immunostaining. To investigate the mechanistic basis of regional heterogeneity, ascending and descending thoracic aortas were harvested after one week of BAPN administration before the appearance of overt pathology.

RESULTS

BAPN-induced aortic rupture predominantly occurred or originated in the descending thoracic aorta in young C57BL/6J or N mice. No apparent differences were found between male and female mice. For mice surviving 12 weeks of BAPN administration, profound dilatation was consistently observed in the ascending region, while there were more heterogeneous changes in the descending thoracic region. Pathological features were distinct between the ascending and descending thoracic regions. Aortic pathology in the ascending region was characterized by luminal dilatation and elastic fiber disruption throughout the media. The descending thoracic region frequently had dissections with false lumen formation, collagen deposition, and remodeling of the wall surrounding the false lumen. Cells surrounding the false lumen were predominantly positive for α-smooth muscle actin. One week of BAPN administration compromised contractile properties in both regions equivalently, and RNA sequencing did not show obvious differences between the two aortic regions in smooth muscle cell markers, cell proliferation markers, and extracellular components.

CONCLUSIONS

BAPN-induced pathologies show distinct, heterogeneous features within and between ascending and descending aortic regions in mice.

Matrix stiffness affects tumor-associated macrophage functional polarization and its potential in tumor therapy

The extracellular matrix (ECM) plays critical roles in cytoskeletal support, biomechanical transduction and biochemical signal transformation. Tumor-associated macrophage (TAM) function is regulated by matrix stiffness in solid tumors and is often associated with poor prognosis. ECM stiffness-induced mechanical cues can activate cell membrane mechanoreceptors and corresponding mechanotransducers in the cytoplasm, modulating the phenotype of TAMs. Currently, tuning TAM polarization through matrix stiffness-induced mechanical stimulation has received increasing attention, whereas its effect on TAM fate has rarely been summarized. A better understanding of the relationship between matrix stiffness and macrophage function will contribute to the development of new strategies for cancer therapy. In this review, we first introduced the overall relationship between macrophage polarization and matrix stiffness, analyzed the changes in mechanoreceptors and mechanotransducers mediated by matrix stiffness on macrophage function and tumor progression, and finally summarized the effects of targeting ECM stiffness on tumor prognosis to provide insight into this new field.

The role of matrix stiffness in breast cancer progression: a review

The significance of matrix stiffness in cancer development has been investigated in recent years. The gradual elastic force the extracellular matrix imparts to cells, known as matrix stiffness, is one of the most important types of mechanical stimulation. Increased matrix stiffness alters the biological activity of cells, which promotes the growth of numerous malignancies, including breast cancer. Comprehensive studies have demonstrated that increasing matrix stiffness activates molecular signaling pathways that are closely linked to breast cancer progression. There are many articles exploring the relationship between mechanism hardness and breast cancer, so we wanted to provide a systematic summary of recent research advances. In this review, we briefly introduce the mechanism of matrix stiffness in breast cancer, elaborate on the effect of extracellular matrix stiffness on breast cancer biological behavior and signaling pathways, and finally, we will talk about breast cancer treatment that focuses on matrix stiffness.

LOXL2 in Cancer: A Two-Decade Perspective

Lysyl Oxidase Like 2 (LOXL2) belongs to the lysyl oxidase (LOX) family, which comprises five lysine tyrosylquinone (LTQ)-dependent copper amine oxidases in humans. In 2003, LOXL2 was first identified as a promoter of tumour progression and, over the course of two decades, numerous studies have firmly established its involvement in multiple cancers. Extensive research with large cohorts of human tumour samples has demonstrated that dysregulated LOXL2 expression is strongly associated with poor prognosis in patients. Moreover, investigations have revealed the association of LOXL2 with various targets affecting diverse aspects of tumour progression. Additionally, the discovery of a complex network of signalling factors acting at the transcriptional, post-transcriptional, and post-translational levels has provided insights into the mechanisms underlying the aberrant expression of LOXL2 in tumours. Furthermore, the development of genetically modified mouse models with silenced or overexpressed LOXL2 has enabled in-depth exploration of its in vivo role in various cancer models. Given the significant role of LOXL2 in numerous cancers, extensive efforts are underway to identify specific inhibitors that could potentially improve patient prognosis. In this review, we aim to provide a comprehensive overview of two decades of research on the role of LOXL2 in cancer.

High lysyl oxidase expression is an indicator of poor prognosis in dogs with cutaneous mast cell tumours

Mast cell tumour (MCT) is one of the most frequent skin tumours in dogs. Due to their unpredictable biological behaviour, MCTs often cause several therapeutic frustrations, leading to investigation regarding prognostic markers. Lysyl oxidase (LOX) is an enzyme that promotes extracellular matrix stability and contributes to cell migration, angiogenesis and epithelial-mesenchymal transition. Its expression positively correlates with poor prognoses in several human and canine mammary cancers. The aim of this study was to characterise the immunohistochemical expression of LOX in MCT samples and compare it with histological grading and post-surgical survival. Twenty-six tumours were submitted to immunohistochemistry for LOX expression evaluation. All samples were positive for LOX, with variable percentages of cytoplasmic and nuclear positivity. Cytoplasmic positivity was significantly higher in high-grade MCTs (P = .0297). Our results indicate that high expression of cytoplasmic LOX in neoplastic mast cells is an indicator of poor prognosis for canine cutaneous MCTs.

Multiple Roles of LOXL2 in the Progression of Hepatocellular Carcinoma and Its Potential for Therapeutic Targeting

LOXL2, a copper-dependent amine oxidase, has emerged as a promising therapeutic target in hepatocellular carcinoma (HCC). Increased LOXL2 expression in HCC has been linked with an aggressive phenotype and represents a poor prognostic factor. Here, we focus on the mechanisms through which LOXL2 orchestrates multiple oncogenic functions in HCC development. We performed a review of the current knowledge on the roles LOXL2 performs in the modulation of the HCC tumor microenvironment, formation of premetastatic niches, and epithelial-mesenchymal transition. We also highlighted the complex interplay between LOXL2 and hypoxia, angiogenesis, and vasculogenic mimicry in HCC. At the end of the review, we summarize the current LOXL2 inhibitors and discuss their potential in HCC precision treatment.

Lysyl Oxidase Family Proteins: Prospective Therapeutic Targets in Cancer

The lysyl oxidase (LOX) family, consisting of LOX and LOX-like proteins 1–4 (LOXL1–4), is responsible for the covalent crosslinking of collagen and elastin, thus maintaining the stability of the extracellular matrix (ECM) and functioning in maintaining connective tissue function, embryonic development, and wound healing. Recent studies have found the aberrant expression or activity of the LOX family occurs in various types of cancer. It has been proved that the LOX family mainly performs tumor microenvironment (TME) remodeling function and is extensively involved in tumor invasion and metastasis, immunomodulation, proliferation, apoptosis, etc. With relevant translational research in progress, the LOX family is expected to be an effective target for tumor therapy. Here, we review the research progress of the LOX family in tumor progression and therapy to provide novel insights for future exploration of relevant tumor mechanism and new therapeutic targets.

Lysyl Oxidase Family Enzymes and Their Role in Tumor Progression

The five genes of the lysyl oxidase family encode enzymes that covalently cross-link components of the extracellular matrix, such as various types of collagen and elastin, and, thus, promote the stabilization of extracellular matrixes. Several of these genes, in particular lysyl oxidase (LOX) and lysyl oxidase like-2 (LOXL2) were identified as genes that are upregulated by hypoxia, and promote tumor cells invasion and metastasis. Here, we focus on the description of the diverse molecular mechanisms by which the various lysyl oxidases affect tumor progression. We also describe attempts that have been made, and are still on-going, that focus on the development of efficient lysyl oxidase inhibitors for the treatment of various forms of cancer, and of diseases associated with abnormal fibrosis.

Loxl2 and Loxl3 Paralogues Play Redundant Roles during Mouse Development

Lysyl oxidase-like 2 (LOXL2) and 3 (LOXL3) are members of the lysyl oxidase family of enzymes involved in the maturation of the extracellular matrix. Both enzymes share a highly conserved catalytic domain, but it is unclear whether they perform redundant functions in vivo. In this study, we show that mice lacking Loxl3 exhibit perinatal lethality and abnormal skeletal development. Additionally, analysis of the genotype of embryos carrying double knockout of Loxl2 and Loxl3 genes suggests that both enzymes have overlapping functions during mouse development. Furthermore, we also show that ubiquitous expression of Loxl2 suppresses the lethality associated with Loxl3 knockout mice.

Disulfiram prevents collagen crosslinking and inhibits renal fibrosis by inhibiting lysyl oxidase enzymes

Chronic kidney disease is one of the major health burdens affecting a considerable number of people worldwide. The aberrant regulation of lysyl oxidase (LOX) family of enzymes results in establishment of dense extracellular matrix (ECM). Since, LOX enzymes need copper (Cu) for their proper catalytic activity; the present study investigated the efficacy of a copper chelator, disulfiram (DSF) in renal fibrosis. Antifibrotic activity of DSF was investigated in kidney epithelial cells stimulated by transforming growth factor-β1 (5 ng/ml) as well as in two animal models. The renal injury was induced in animals by unilateral ureteral obstruction and folic acid administration (250 mg/kg). The DSF (3 and 10 mg/kg, every 3rd day) and standard LOX inhibitor, β-aminopropionitrile (BAPN, 100 mg/kg, daily) administration was started on day 0 and continued till the day of sacrifice. DSF was found to be a potent LOX/LOXL2 inhibitor to reduce crosslinking of collagen fibrils leading to reduction in the collagen deposition. In addition, the DSF was demonstrated to inhibit epithelial-mesenchymal transition in the tubular cells and fibrotic kidneys. Our results suggested that DSF, being a clinically available drug could be translated to clinics for its potent antifibrotic activity due to its inhibitory effect on LOX proteins.

Increased Fibrosis in a Mouse Model of Anti-Laminin 332 Mucous Membrane Pemphigoid Remains Unaltered by Inhibition of Aldehyde Dehydrogenase

Mucous membrane pemphigoid (MMP) is an autoimmune blistering disease characterized by autoantibodies against the basal membrane zone of skin and surface-close epithelia and predominant mucosal lesions. The oral cavity and conjunctivae are most frequently affected, albeit clinical manifestations can also occur on the skin. MMP-associated lesions outside the oral cavity typically lead to scarring. Mechanisms underlying scarring are largely unknown in MMP and effective treatment options are limited. Herein, we assessed the collagen architecture in tissue samples of an antibody-transfer mouse model of anti-laminin-332 MMP. In MMP mice, increased collagen fibril density was observed in skin and conjunctival lesions compared to mice injected with normal rabbit IgG. The extracellular matrix of MMP skin samples also showed altered post-translational collagen cross-linking with increased levels of both lysine- and hydroxylysine-derived collagen crosslinks supporting the fibrotic phenotype in experimental MMP compared to control animals. In addition, we evaluated a potential anti-fibrotic therapy in experimental anti-laminin-332 MMP using disulfiram, an inhibitor of the aldehyde dehydrogenase (ALDH), which has been implicated in immune-mediated mucosal scarring. In addition, disulfiram also acts as a copper chelator that was shown to block lysyl oxidase activity, an enzyme involved in formation of collagen crosslinks. Topical use of disulfiram (300 μM in 2% [w/v] methocel) did not improve ocular lesions in experimental MMP over the 12-day treatment period in disulfiram-treated mice compared to vehicle-treated mice (n=8/group). Furthermore, C57BL6/J mice (n=8/group) were treated prophylactically with 200 mg/kg p.o. disulfiram or the solvent once daily over a period of 12 days. Systemic treatment did not show any reduction in the severity of oral and ocular lesions in MMP mice, albeit some improvement in skin lesions was observed in disulfiram- vs. vehicle-treated mice (p=0.052). No reduction in fibrosis was seen, as assessed by immunohistochemistry. Whilst blocking of ALDH failed to significantly ameliorate disease activity, our data provide new insight into fibrotic processes highlighting changes in the collagenous matrix and cross-linking patterns in IgG-mediated MMP.

β-Aminopropionitrile-induced aortic aneurysm and dissection in mice

The mechanistic basis for the formation of aortic aneurysms and dissection needs to be elucidated to facilitate the development of effective medications. β-Aminopropionitrile administration in mice has been used frequently to study the pathologic features and mechanisms of aortic aneurysm and dissection. This mouse model mimics several facets of the pathology of human aortic aneurysms and dissection, although many variables exist in the experimental design and protocols that must be resolved to determine its application to the human disease. In the present brief review, we have introduced the development of this mouse model and provided insights into understanding its pathologic features.

Recent Developments in the Study of the Microenvironment of Cancer and Drug Delivery

Cancer is characterized by disrupted molecular variables caused by cells that deviate from regular signal transduction. The uncontrolled segment of such cancerous cells annihilates most of the tissues that contact them. Gene therapy, immunotherapy, and nanotechnology advancements have resulted in novel strategies for anticancer drug delivery. Furthermore, diverse dispersion of nanoparticles in normal stroma cells adversely affects the healthy cells and disrupts the crosstalk of tumour stroma. It can contribute to cancer cell progression inhibition and, conversely, to acquired resistance, enabling cancer cell metastasis and proliferation. The tumour's microenvironment is critical in controlling the dispersion and physiological activities of nano-chemotherapeutics which is one of the targeted drug therapy. As it is one of the methods of treating cancer that involves the use of medications or other substances to specifically target and kill off certain subsets of malignant cells. A targeted therapy may be administered alone or in addition to more conventional methods of care like surgery, chemotherapy, or radiation treatment. The tumour microenvironment, stromatogenesis, barriers and advancement in the drug delivery system across tumour tissue are summarised in this review.

Rapid Identification of Potential Drug Candidates from Multi-Million Compounds' Repositories. Combination of 2D Similarity Search with 3D Ligand/Structure Based Methods and In Vitro Screening

Rapid in silico selection of target focused libraries from commercial repositories is an attractive and cost-effective approach in early drug discovery. If structures of active compounds are available, rapid 2D similarity search can be performed on multimillion compounds' databases. This approach can be combined with physico-chemical parameter and diversity filtering, bioisosteric replacements, and fragment-based approaches for performing a first round biological screening. Our objectives were to investigate the combination of 2D similarity search with various 3D ligand and structure-based methods for hit expansion and validation, in order to increase the hit rate and novelty. In the present account, six case studies are described and the efficiency of mixing is evaluated. While sequentially combined 2D/3D similarity approach increases the hit rate significantly, sequential combination of 2D similarity with pharmacophore model or 3D docking enriched the resulting focused library with novel chemotypes. Parallel integrated approaches allowed the comparison of the various 2D and 3D methods and revealed that 2D similarity-based and 3D ligand and structure-based techniques are often complementary, and their combinations represent a powerful synergy. Finally, the lessons we learnt including the advantages and pitfalls of the described approaches are discussed.

Understanding the molecular mechanism associated with reversal of oral submucous fibrosis targeting hydroxylysine aldehyde-derived collagen cross-links

Fibrosis is a pathological state characterized by excessive deposition of the extracellular matrix components leading to impaired tissue function in the affected organ. It results in scarring of the affected tissue akin to an over-healing wound as a consequence of chronic inflammation and repair in response to injury. Persistent trauma of susceptible oral mucosa due to habitual chewing of betel quid resulting in zealous healing of the mucosal tissue is one plausible explanation for the onset of oral submucous fibrosis (OSF). The irreversibility and resistance of collagen to degradation and its high potential to undergo malignant change are a major reason for morbidity in OSF. Hence, early diagnosis and timely treatment are crucial to prevent the progression of OSF to malignancy. This review focuses on the mechanistic insight into the role of collagen cross-links in advancing fibrosis and possible therapeutic targets that bring about a reversal of fibrosis. These options may be beneficial if attempted as a specific therapeutic modality in OSF as is in organ fibrosis. The upregulation of lysyl oxidase and lysyl hydroxylase has been shown to exhibit the higher levels of the hydroxylysine aldehyde-derived cross-links in fibrosis and tumor stroma promoting the tumor cell survival, resistance, and invasion. The in silico analysis highlights the potential drugs that may target the genes regulating collagen crosslinking.

LOXL2 Inhibitors and Breast Cancer Progression

LOX (lysyl oxidase) and lysyl oxidase like-1–4 (LOXL 1–4) are amine oxidases, which catalyze cross-linking reactions of elastin and collagen in the connective tissue. These amine oxidases also allow the cross-link of collagen and elastin in the extracellular matrix of tumors, facilitating the process of cell migration and the formation of metastases. LOXL2 is of particular interest in cancer biology as it is highly expressed in some tumors. This protein also promotes oncogenic transformation and affects the proliferation of breast cancer cells. LOX and LOXL2 inhibition have thus been suggested as a promising strategy to prevent metastasis and invasion of breast cancer. BAPN (β-aminopropionitrile) was the first compound described as a LOX inhibitor and was obtained from a natural source. However, novel synthetic compounds that act as LOX/LOXL2 selective inhibitors or as dual LOX/LOX-L inhibitors have been recently developed. In this review, we describe LOX enzymes and their role in promoting cancer development and metastases, with a special focus on LOXL2 and breast cancer progression. Moreover, the recent advances in the development of LOXL2 inhibitors are also addressed. Overall, this work contextualizes and explores the importance of LOXL2 inhibition as a promising novel complementary and effective therapeutic approach for breast cancer treatment.

Targeting Lysyl Oxidase Family Meditated Matrix Cross-Linking as an Anti-Stromal Therapy in Solid Tumours

Simple Summary

To improve efficacy of solid cancer treatment, efforts have shifted towards targeting both the cancer cells and the surrounding tumour tissue they grow in. The lysyl oxidase (LOX) family of enzymes underpin the fibrotic remodeling of the tumour microenvironment to promote both cancer growth, spread throughout the body and modulate response to therapies. This review examines how the lysyl oxidase family is involved in tumour development, how they can be targeted, and their potential as diagnostic and prognostic biomarkers in solid tumours.

Abstract

The lysyl oxidase (LOX) family of enzymes are a major driver in the biogenesis of desmoplastic matrix at the primary tumour and secondary metastatic sites. With the increasing interest in and development of anti-stromal therapies aimed at improving clinical outcomes of cancer patients, the Lox family has emerged as a potentially powerful clinical target. This review examines how lysyl oxidase family dysregulation in solid cancers contributes to disease progression and poor patient outcomes, as well as an evaluation of the preclinical landscape of LOX family targeting therapeutics. We also discuss the suitability of the LOX family as a diagnostic and/or prognostic marker in solid tumours.

Disulfiram as a Therapeutic Agent for Metastatic Malignant Melanoma-Old Myth or New Logos?

Simple Summary

In recent years, disulfiram has gained in attention as an anticancer drug due to its broad activity against various cancers, and its mechanisms and molecular targets have been deciphered in vitro and in vivo. One of these cancers is melanoma. Initial data from human studies show some benefit, but do not confirm its broad efficacy as a monotherapy. However, combination approaches could pave the way for exploiting the beneficial effects of disulfiram for cancer patients, including those with melanoma.

Abstract

New therapeutic concepts such as anti-PD-1-based immunotherapy or targeted therapy with BRAF and MEK inhibitors have significantly improved the survival of melanoma patients. However, about 20% of patients with targeted therapy and up to 50% with immunotherapies do not respond to their first-line treatment or rapidly develop resistance. In addition, there is no approved targeted therapy for certain subgroups, namely BRAF wild-type melanomas, although they often bear aggressive tumor biology. A repurposing of already approved drugs is a promising strategy to fill this gap, as it will result in comparatively low costs, lower risks and time savings. Disulfiram (DSF), the first drug to treat alcoholism, which received approval from the US Food and Drug Administration more than 60 years ago, is such a drug candidate. There is growing evidence that DSF has great potential for the treatment of various human cancers, including melanoma. Several mechanisms of its antitumor activity have been identified, amongst them the inhibition of the ubiquitin-proteasome system, the induction of reactive oxygen species and various death signaling pathways. This article provides an overview of the application of DSF in humans, its molecular mechanisms and targets in cancer therapy with a focus on melanoma. The results of clinical studies and experimental combination approaches of DSF with various cancer therapies are discussed, with the aim of exploring the potential of DSF in melanoma therapy.

Lysyl oxidases: Emerging biomarkers and therapeutic targets for various diseases

Therapeutic targeting of extracellular proteins has attracted huge attention in treating human diseases. The lysyl oxidases (LOXs) are a family of secreted copper-dependent enzymes which initiate the covalent crosslinking of collagen and elastin fibers in the extracellular microenvironment, thereby facilitating extracellular matrix (ECM) remodeling and ECM homeostasis. Apart from ECM-dependent roles, LOXs are also involved in other biological processes such as epithelial-to-mesenchymal transition (EMT) and transcriptional regulation, especially following hypoxic stress. Dysregulation of LOXs is found to underlie the onset and progression of multiple pathologies, such as carcinogenesis and cancer metastasis, fibrotic diseases, neurodegeneration and cardiovascular diseases. In this review, we make a comprehensive summarization of clinical and experimental evidences that support roles of for LOXs in disease pathology and points out LOXs as promising therapeutic targets for improving prognosis. Additionally, we also propose that LOXs reshape cell-ECM interaction or cell-cell interaction due to ECM-dependent and ECM-independent roles for LOXs. Therapeutic intervention of LOXs may have advantages in the maintenance of communication between ECM and cell or intercellular signaling, finally recovering organ function.

Lysyl Oxidase (LOX) Family Members: Rationale and Their Potential as Therapeutic Targets for Liver Fibrosis

The cross-linking of structural extracellular matrix (ECM) components, especially fibrillar collagens and elastin, is strongly implicated in fibrosis progression and resistance to fibrosis reversal. Lysyl oxidase family members (LOX and LOXL1 [lysyl oxidase-like 1], LOXL2 [lysyl oxidase-like 2], LOXL3 [lysyl oxidase-like 3], and LOXL4 [lysyl oxidase like 4]) are extracellular copper-dependent enzymes that play a key role in ECM cross-linking, but have also other intracellular functions relevant to fibrosis and carcinogenesis. Although the expression of most LOX family members is elevated in experimental liver fibrosis of diverse etiologies, their individual contribution to fibrosis is incompletely understood. Inhibition of the LOX family as a whole and of LOX, LOXL1, and LOXL2 specifically has been shown to suppress fibrosis progression and accelerate its reversal in rodent models of cardiac, renal, pulmonary, and liver fibrosis. Recent disappointing clinical trials with a monoclonal antibody against LOXL2 (simtuzumab) in patients with pulmonary and liver fibrosis dampened enthusiasm for LOX family member inhibition. However, this unexpected negative outcome may be related to the inefficient antibody, rather than to LOXL2, not qualifying as a relevant antifibrotic target. Moreover, LOX family members other than LOXL2 may prove to be attractive therapeutic targets. In this review, we summarize the structural hallmarks, expression patterns, covalent cross-linking activities, and modes of regulation of LOX family members and discuss the clinical potential of their inhibition to treat fibrosis in general and liver fibrosis in particular.

Role of the lysyl oxidase enzyme family in cardiac function and disease

Heart diseases are a major cause of morbidity and mortality world-wide. Lysyl oxidase (LOX) and related LOX-like (LOXL) isoforms play a vital role in remodelling the extracellular matrix (ECM). The LOX family controls ECM formation by cross-linking collagen and elastin chains. LOX/LOXL proteins are copper-dependent amine oxidases that catalyse the oxidation of lysine, causing cross-linking between the lysine moieties of lysine-rich proteins. Dynamic changes in LOX and LOXL protein-expression occur in a variety of cardiac pathologies; these changes are believed to be central to the associated tissue-fibrosis. An awareness of the potential pathophysiological importance of LOX has led to the evaluation of interventions that target LOX/LOXL proteins for heart-disease therapy. The purposes of this review article are: (i) to summarize the basic biochemistry and enzyme function of LOX and LOXL proteins; (ii) to consider their tissue and species distribution; and (iii) to review the results of experimental studies of the roles of LOX and LOXL proteins in heart disease, addressing involvement in the mechanisms, pathophysiology and therapeutic responses based on observations in patient samples and relevant animal models. Therapeutic targeting of LOX family enzymes has shown promising results in animal models, but small-molecule approaches have been limited by non-specificity and off-target effects. Biological approaches show potential promise but are in their infancy. While there is strong evidence for LOX-family protein participation in heart failure, myocardial infarction, cardiac hypertrophy, dilated cardiomyopathy, atrial fibrillation and hypertension, as well as potential interest as therapeutic targets, the precise involvement of LOX-family proteins in heart disease requires further investigation.

Mechano-therapeutics: Targeting Mechanical Signaling in Fibrosis and Tumor Stroma

Pathological remodeling of the extracellular matrix (ECM) by activated myofibroblasts is a hallmark of fibrotic diseases and desmoplastic tumors. Activation of myofibroblasts occurs in response to fibrogenic tissue injury as well as in tumor-associated fibrotic reactions. The molecular determinants of myofibroblast activation in fibrosis and tumor stroma have traditionally been viewed to include biochemical agents, such as dysregulated growth factor and cytokine signaling, which profoundly alter the biology of fibroblasts, ultimately leading to overexuberant matrix deposition and fibrosis. More recently, compelling evidence has shown that altered mechanical properties of the ECM such as matrix stiffness are major drivers of tissue fibrogenesis by promoting mechano-activation of fibroblasts. In this Review, we discuss new insights into the role of the biophysical microenvironment in the amplified activation of fibrogenic myofibroblasts during the development and progression of fibrotic diseases and desmoplastic tumors. We also summarize novel therapeutic targets for anti-fibrotic therapy based on the mechanobiology of tissue fibrosis and tumor stroma, a class of drugs known as "mechano-therapeutics".

Tumor microenvironment complexity and therapeutic implications at a glance

The dynamic interactions of cancer cells with their microenvironment consisting of stromal cells (cellular part) and extracellular matrix (ECM) components (non-cellular) is essential to stimulate the heterogeneity of cancer cell, clonal evolution and to increase the multidrug resistance ending in cancer cell progression and metastasis. The reciprocal cell-cell/ECM interaction and tumor cell hijacking of non-malignant cells force stromal cells to lose their function and acquire new phenotypes that promote development and invasion of tumor cells. Understanding the underlying cellular and molecular mechanisms governing these interactions can be used as a novel strategy to indirectly disrupt cancer cell interplay and contribute to the development of efficient and safe therapeutic strategies to fight cancer. Furthermore, the tumor-derived circulating materials can also be used as cancer diagnostic tools to precisely predict and monitor the outcome of therapy. This review evaluates such potentials in various advanced cancer models, with a focus on 3D systems as well as lab-on-chip devices. Video abstract.

Targeting the lysyl oxidases in tumour desmoplasia

The extracellular matrix (ECM) is a fundamental component of tissue microenvironments and its dysregulation has been implicated in a number of diseases, in particular cancer. Tumour desmoplasia (fibrosis) accompanies the progression of many solid cancers, and is also often induced as a result of many frontline chemotherapies. This has recently led to an increased interest in targeting the underlying processes. The major structural components of the ECM contributing to desmoplasia are the fibrillar collagens, whose key assembly mechanism is the enzymatic stabilisation of procollagen monomers by the lysyl oxidases. The lysyl oxidase family of copper-dependent amine oxidase enzymes are required for covalent cross-linking of collagen (as well as elastin) molecules into the mature ECM. This key step in the assembly of collagens is of particular interest in the cancer field since it is essential to the tumour desmoplastic response. LOX family members are dysregulated in many cancers and consequently the development of small molecule inhibitors targeting their enzymatic activity has been initiated by many groups. Development of specific small molecule inhibitors however has been hindered by the lack of crystal structures of the active sites, and therefore alternate indirect approaches to target LOX have also been explored. In this review, we introduce the importance of, and assembly steps of the ECM in the tumour desmoplastic response focussing on the role of the lysyl oxidases. We also discuss recent progress in targeting this family of enzymes as a potential therapeutic approach.

Lysyl oxidases: linking structures and immunity in the tumor microenvironment

The lysyl oxidases (LOXs) are a family of enzymes deputed to cross-link collagen and elastin, shaping the structure and strength of the extracellular matrix (ECM). However, many novel “non-canonical” functions, alternative substrates, and regulatory mechanisms have been described and are being continuously elucidated. The activity of LOXs, therefore, appears to be integrated into a complex network of signals regulating many cell functions, including survival/proliferation/differentiation. Among these signaling pathways, TGF-β and PI3K/Akt/mTOR, in particular, cross-talk extensively with each other and with LOXs also initiating complex feedback loops which modulate the activity of LOXs and direct the remodeling of the ECM. A growing body of evidence indicates that LOXs are not only important in the homeostasis of the normal structure of the ECM, but are also implicated in the establishment and maturation of the tumor microenvironment. LOXs’ association with advanced and metastatic cancer is well established; however, there is enough evidence to support a significant role of LOXs in the transformation of normal epithelial cells, in the accelerated tumor development and the induction of invasion of the premalignant epithelium. A better understanding of LOXs and their interactions with the different elements of the tumor immune microenvironment will prove invaluable in the design of novel anti-tumor strategies.

Activity and Trafficking of Copper-Transporting ATPases in Tumor Development and Defense against Platinum-Based Drugs

Membrane trafficking pathways emanating from the Golgi regulate a wide range of cellular processes. One of these is the maintenance of copper (Cu) homeostasis operated by the Golgi-localized Cu-transporting ATPases ATP7A and ATP7B. At the Golgi, these proteins supply Cu to newly synthesized enzymes which use this metal as a cofactor to catalyze a number of vitally important biochemical reactions. However, in response to elevated Cu, the Golgi exports ATP7A/B to post-Golgi sites where they promote sequestration and efflux of excess Cu to limit its potential toxicity. Growing tumors actively consume Cu and employ ATP7A/B to regulate the availability of this metal for oncogenic enzymes such as LOX and LOX-like proteins, which confer higher invasiveness to malignant cells. Furthermore, ATP7A/B activity and trafficking allow tumor cells to detoxify platinum (Pt)-based drugs (like cisplatin), which are used for the chemotherapy of different solid tumors. Despite these noted activities of ATP7A/B that favor oncogenic processes, the mechanisms that regulate the expression and trafficking of Cu ATPases in malignant cells are far from being completely understood. This review summarizes current data on the role of ATP7A/B in the regulation of Cu and Pt metabolism in malignant cells and outlines questions and challenges that should be addressed to understand how ATP7A and ATP7B trafficking mechanisms might be targeted to counteract tumor development.

Lysyl oxidases: from enzyme activity to extracellular matrix cross-links

The lysyl oxidase family comprises five members in mammals, lysyl oxidase (LOX) and four lysyl oxidase like proteins (LOXL1-4). They are copper amine oxidases with a highly conserved catalytic domain, a lysine tyrosylquinone cofactor, and a conserved copper-binding site. They catalyze the first step of the covalent cross-linking of the extracellular matrix (ECM) proteins collagens and elastin, which contribute to ECM stiffness and mechanical properties. The role of LOX and LOXL2 in fibrosis, tumorigenesis, and metastasis, including changes in their expression level and their regulation of cell signaling pathways, have been extensively reviewed, and both enzymes have been identified as therapeutic targets. We review here the molecular features and three-dimensional structure/models of LOX and LOXLs, their role in ECM cross-linking, and the regulation of their cross-linking activity by ECM proteins, proteoglycans, and by inhibitors. We also make an overview of the major ECM cross-links, because they are the ultimate molecular readouts of LOX/LOXL activity in tissues. The recent 3D model of LOX, which recapitulates its known structural and biochemical features, will be useful to decipher the molecular mechanisms of LOX interaction with its various substrates, and to design substrate-specific inhibitors, which are potential antifibrotic and antitumor drugs.

LOXL3 Function Beyond Amino Oxidase and Role in Pathologies, Including Cancer

Lysyl oxidase like 3 (LOXL3) is a copper-dependent amine oxidase responsible for the crosslinking of collagen and elastin in the extracellular matrix. LOXL3 belongs to a family including other members: LOX, LOXL1, LOXL2, and LOXL4. Autosomal recessive mutations are rare and described in patients with Stickler syndrome, early-onset myopia and non-syndromic cleft palate. Along with an essential function in embryonic development, multiple biological functions have been attributed to LOXL3 in various pathologies related to amino oxidase activity. Additionally, various novel roles have been described for LOXL3, such as the oxidation of fibronectin in myotendinous junction formation, and of deacetylation and deacetylimination activities of STAT3 to control of inflammatory response. In tumors, three distinct roles were described: (1) LOXL3 interacts with SNAIL and contributes to proliferation and metastasis by inducing epithelial-mesenchymal transition in pancreatic ductal adenocarcinoma cells; (2) LOXL3 is localized predominantly in the nucleus associated with invasion and poor gastric cancer prognosis; (3) LOXL3 interacts with proteins involved in DNA stability and mitosis completion, contributing to melanoma progression and sustained proliferation. Here we review the structure, function and activity of LOXL3 in normal and pathological conditions and discuss the potential of LOXL3 as a therapeutic target in various diseases.

Interplay Between LOX Enzymes and Integrins in the Tumor Microenvironment

Members of the lysyl oxidase (LOX) family are secreted copper-dependent amine oxidases that catalyze the covalent crosslinking of collagens and elastin in the extracellular matrix (ECM), an essential process for the structural integrity of all tissues. LOX enzymes can also remodel the tumor microenvironment and have been implicated in all stages of tumor initiation and progression of many cancer types. Changes in the ECM can influence several cancer cell phenotypes. Integrin adhesion complexes (IACs) physically connect cells with their microenvironment. This review article summarizes the main findings on the role of LOX proteins in modulating the tumor microenvironment, with a particular focus on how ECM changes are integrated by IACs to modulate cells behavior. Finally, we discuss how the development of selective LOX inhibitors may lead to novel and effective therapies in cancer treatment.