Lysyl oxidase-like 2 promotes migration in noninvasive breast cancer cells but not in normal breast epithelial cells

Downregulation of LOX Overexpression Promotes Retinal Ganglion Cells Survival in an Acute Ocular Hypertension Model

PURPOSE

To investigate the effect of reducing Lysyl oxidase (LOX) overexpression on retinal ganglion cells (RGCs) apoptosis in an acute ocular hypertension (AOH) rat model.

METHODS

AOH rat model was performed by anterior chamber perfusion and either received an intravitreal injection with β-aminopropionitrile (BAPN) or normal saline. After 2wk, Quantification of survival RGCs in the retina was performed using Retrograde FluoroGold labeling. The mRNA expression levels of LOX, LOXL1-4, collagen 1a1 (Col1a1), collagen 3a1 (Col3a1), collagen4a1 (Col4a1), elastin (Eln), fibronectin1 (Fbn1), fibronectin4 (Fbn4) were determined by RT-qPCR. LOX expression was determined by Western blot (WB) analysis and immunohistochemistry. The RNA expression of LOX, Eln and Col1a1 in RGCs retrograde-labeled with 1,1'-dioctadecyl-3,3,3',3' tetra-methylindocarbocyanine perchlorate(DiI)that selected through FACS sorting were determined by RT-qPCR analysis. Changes of the retinal function were detected by Electroretinogram (ERG) analysis.

RESULTS

Results showed that significant LOX overexpression and loss of RGCs related to IOP exposure in AOH retinas. PCR analysis indicated significant increased mRNA level of Col1a1, Col3al and Eln in AOH retinas. Significant increase mRNA expression of LOX, Col1a1 and Eln in the RGCs were observed in AOH group compared with CON group. AOH rats injected with BAPN showed a significant decrease in LOX expression, reduced the loss of RGCs and retinal function damage.

CONCLUSIONS

The results demonstrated that changes of LOX and specific ECM components in retina were correlated with AOH. Findings from this study indicated that preventing LOX over-expression may be protective against RGCs loss and retinal function damage in AOH animal model.

LOXL2-mediated chromatin compaction is required to maintain the oncogenic properties of triple-negative breast cancer cells

Oxidation of histone H3 at lysine 4 (H3K4ox) is catalyzed by lysyl oxidase homolog 2 (LOXL2). This histone modification is enriched in heterochromatin in triple-negative breast cancer (TNBC) cells and has been linked to the maintenance of compacted chromatin. However, the molecular mechanism underlying this maintenance is still unknown. Here, we show that LOXL2 interacts with RuvB-Like 1 (RUVBL1), RuvB-Like 2 (RUVBL2), Actin-like protein 6A (ACTL6A), and DNA methyltransferase 1associated protein 1 (DMAP1), a complex involved in the incorporation of the histone variant H2A.Z. Our experiments indicate that this interaction and the active form of RUVBL2 are required to maintain LOXL2-dependent chromatin compaction. Genome-wide experiments showed that H2A.Z, RUVBL2, and H3K4ox colocalize in heterochromatin regions. In the absence of LOXL2 or RUVBL2, global levels of the heterochromatin histone mark H3K9me3 were strongly reduced, and the ATAC-seq signal in the H3K9me3 regions was increased. Finally, we observed that the interplay between these series of events is required to maintain H3K4ox-enriched heterochromatin regions, which in turn is key for maintaining the oncogenic properties of the TNBC cell line tested (MDA-MB-231).

Targeting Pivotal Hallmarks of Cancer for Enhanced Therapeutic Strategies in Triple-Negative Breast Cancer Treatment-In Vitro, In Vivo and Clinical Trials Literature Review

This literature review provides a comprehensive overview of triple-negative breast cancer (TNBC) and explores innovative targeted therapies focused on specific hallmarks of cancer cells, aiming to revolutionize breast cancer treatment. TNBC, characterized by its lack of expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), presents distinct features, categorizing these invasive breast tumors into various phenotypes delineated by key elements in molecular assays. This article delves into the latest advancements in therapeutic strategies targeting components of the tumor microenvironment and pivotal hallmarks of cancer: deregulating cellular metabolism and the Warburg effect, acidosis and hypoxia, the ability to metastasize and evade the immune system, aiming to enhance treatment efficacy while mitigating systemic toxicity. Insights from in vitro and in vivo studies and clinical trials underscore the promising effectiveness and elucidate the mechanisms of action of these novel therapeutic interventions for TNBC, particularly in cases refractory to conventional treatments. The integration of targeted therapies tailored to the molecular characteristics of TNBC holds significant potential for optimizing clinical outcomes and addressing the pressing need for more effective treatment options for this aggressive subtype of breast cancer.

Extracellular Hsp90 Binds to and Aligns Collagen-1 to Enhance Breast Cancer Cell Invasiveness

Cancer cell-secreted eHsp90 binds and activates proteins in the tumor microenvironment crucial in cancer invasion. Therefore, targeting eHsp90 could inhibit invasion, preventing metastasis-the leading cause of cancer-related mortality. Previous eHsp90 studies have solely focused on its role in cancer invasion through the 2D basement membrane (BM), a form of extracellular matrix (ECM) that lines the epithelial compartment. However, its role in cancer invasion through the 3D Interstitial Matrix (IM), an ECM beyond the BM, remains unexplored. Using a Collagen-1 binding assay and second harmonic generation (SHG) imaging, we demonstrate that eHsp90 directly binds and aligns Collagen-1 fibers, the primary component of IM. Furthermore, we show that eHsp90 enhances Collagen-1 invasion of breast cancer cells in the Transwell assay. Using Hsp90 conformation mutants and inhibitors, we established that the Hsp90 dimer binds to Collagen-1 via its N-domain. We also demonstrated that while Collagen-1 binding and alignment are not influenced by Hsp90's ATPase activity attributed to the N-domain, its open conformation is crucial for increasing Collagen-1 alignment and promoting breast cancer cell invasion. These findings unveil a novel role for eHsp90 in invasion through the IM and offer valuable mechanistic insights into potential therapeutic approaches for inhibiting Hsp90 to suppress invasion and metastasis.

The functional and evolutionary impacts of human-specific deletions in conserved elements

Conserved genomic sequences disrupted in humans may underlie uniquely human phenotypic traits. We identified and characterized 10,032 human-specific conserved deletions (hCONDELs). These short (average 2.56 base pairs) deletions are enriched for human brain functions across genetic, epigenomic, and transcriptomic datasets. Using massively parallel reporter assays in six cell types, we discovered 800 hCONDELs conferring significant differences in regulatory activity, half of which enhance rather than disrupt regulatory function. We highlight several hCONDELs with putative human-specific effects on brain development, including HDAC5, CPEB4, and PPP2CA. Reverting an hCONDEL to the ancestral sequence alters the expression of LOXL2 and developmental genes involved in myelination and synaptic function. Our data provide a rich resource to investigate the evolutionary mechanisms driving new traits in humans and other species.

Lysyl oxidase-like 2 processing by factor Xa modulates its activity and substrate preference

Lysyl oxidase-like 2 (LOXL2) has been identified as an essential mediator of extracellular matrix (ECM) remodeling in several disease processes including cardiovascular disease. Thus, there is growing interest in understanding the mechanisms by which LOXL2 is regulated in cells and tissue. While LOXL2 occurs both in full length and processed forms in cells and tissue, the precise identity of the proteases that process LOXL2 and the consequences of processing on LOXL2's function remain incompletely understood. Here we show that Factor Xa (FXa) is a protease that processes LOXL2 at Arg-338. Processing by FXa does not affect the enzymatic activity of soluble LOXL2. However, in situ in vascular smooth muscle cells, LOXL2 processing by FXa results in decreased cross-linking activity in the ECM and shifts substrate preference of LOXL2 from type IV collagen to type I collagen. Additionally, processing by FXa increases the interactions between LOXL2 and prototypical LOX, suggesting a potential compensatory mechanism to preserve total LOXs activity in the vascular ECM. FXa expression is prevalent in various organ systems and shares similar roles in fibrotic disease progression as LOXL2. Thus, LOXL2 processing by FXa could have significant implications in pathologies where LOXL2 is involved.

Copper Exposure Induces Epithelial-Mesenchymal Transition-Related Fibrotic Change via Autophagy and Increase Risk of Lung Fibrosis in Human

Copper is an essential trace element involved in several vital biological processes of the human body. However, excess exposure to copper caused by occupational hazards and environmental contamination, such as food, water, and air, damages human health. In this study, in vitro cell culture model and epidemiologic studies were conducted to evaluate the effect of copper on lung fibrosis. In vitro, treatment of CuSO₄ in lung epithelial cells at 100 μM consistently decreases cell viability in alveolar type (A549) and human bronchial epithelial (HBE) cells. CuSO₄ promotes epithelial-mesenchymal transition (EMT) as shown by increased cell migration and increased EMT marker and fibrotic gene expressions. Besides, CuSO₄ induced cell autophagy, with an increased LC3, PINK, and decreased p62 expression. Inhibition of ROS by N-acetylcysteine reversed the CuSO₄-induced PINK1, LC3, and Snail expressions. Inhibition of autophagy by chloroquine reverses the CuSO₄-induced EMT changes. Nature flavonoids, especially kaempferol, and fustin, were shown to inhibit Copper-induced EMT. In humans, a unit increase in urinary copper concentration was significantly associated with an increased risk of lung fibrotic changes (odds ratio [OR] = 1.17, 95% confidence interval [CI] = 1.01-1.36, p = 0.038). These results indicated that Copper is a risk factor for lung fibrosis through activation of the ROS-autophagy-EMT pathway, which can be reversed by flavonoids.

Cancer-Associated Fibroblasts in the Breast Tumor Microenvironment

Years of investigation have shed light on a theory in which breast tumor epithelial cells are under the effect of the stromal microenvironment. This review aims to discuss recent findings concerning the phenotypic and functional characteristics of cancer associated fibroblasts (CAFs) and their involvement in tumor evolution, as well as their potential implications for anti-cancer therapy. In this manuscript, we reviewed that CAFs play a fundamental role in initiation, growth, invasion, and metastasis of breast cancer, and also serve as biomarkers in the clinical diagnosis, therapy, and prognosis of this disease.

Novel mechanism for OSM-promoted extracellular matrix remodeling in breast cancer: LOXL2 upregulation and subsequent ECM alignment

BACKGROUND

Invasive ductal carcinoma (IDC) is a serious problem for patients as it metastasizes, decreasing 5-year patient survival from > 95 to ~ 27%. The breast tumor microenvironment (TME) is often saturated with proinflammatory cytokines, such as oncostatin M (OSM), which promote epithelial-to-mesenchymal transitions (EMT) in IDC and increased metastasis. The extracellular matrix (ECM) also plays an important role in promoting invasive and metastatic potential of IDC. Specifically, the reorganization and alignment of collagen fibers in stromal ECM leads to directed tumor cell motility, which promotes metastasis. Lysyl oxidase like-2 (LOXL2) catalyzes ECM remodeling by crosslinking of collagen I in the ECM. We propose a novel mechanism whereby OSM induces LOXL2 expression, mediating stromal ECM remodeling of the breast TME.

METHODS

Bioinformatics was utilized to determine survival and gene correlation in patients. IDC cell lines were treated with OSM (also IL-6, LIF, and IL-1β) and analyzed for LOXL2 expression by qRT-PCR and immunolabelling techniques. Collagen I contraction assays, 3D invasion assays, and confocal microscopy were performed with and without LOXL2 inhibition to determine the impact of OSM-induced LOXL2 on the ECM.

RESULTS

Our studies demonstrate that IDC patients with high LOXL2 and OSM co-expression had worse rates of metastasis-free survival than those with high levels of either, individually, and LOXL2 expression is positively correlated to OSM/OSM receptor (OSMR) expression in IDC patients. Furthermore, human IDC cells treated with OSM resulted in a significant increase in LOXL2 mRNA, which led to upregulated protein expression of secreted, glycosylated, and enzymatically active LOXL2. The expression of LOXL2 in IDC cells did not affect OSM-promoted EMT, and LOXL2 was localized to the cytoplasm and/or secreted. OSM-induced LOXL2 promoted an increase in ECM collagen I fiber crosslinking, which led to significant fiber alignment between cells and increased IDC cell invasion.

CONCLUSIONS

Aligned collagen fibers in the ECM provide pathways for tumor cells to migrate more easily through the stroma to nearby vasculature and tissue. These results provide a new paradigm through which proinflammatory cytokine OSM promotes tumor progression. Understanding the nuances in IDC metastasis will lead to better potential therapeutics to combat against the possibility.

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.

Significance of HIF-1α Expression and LOXL-2 Localization in Progression of Oral Squamous Cell Carcinoma

Backgroud: In the microenvironment of Oral Squamous Cell Carcinoma (OSCC), Hypoxia-inducible transcription factor 1 (HIF-1) is a very important chemical mediator in the microenvironment of OSCC through which cells respond to hypoxia. LOXL-2 participates in ECM remodelling, and also in regulating epithelial-to-mesenchymal transition, epithelial cell polarity and differentiation. Aim/material and methods: The present study was conducted on 90 histopathologically proven cases of OSCC to ascertain the role of HIF-1α and LOXL-2 in OSCC. Immunoexpression of both HIF-1α and LOXL-2 was analyzed both quantitatively and qualitatively and compared with tumor stage, nodal stage, clinical stage, and histological grade. Results: Tumor stages and nodal stages had significant correlation with HIF-1α expression and localization of LOXL-2 immunoexpression respectively. Conclusion: This is probably the first study to analyze LOXL-2 localization in OSCC. Alteration in the immunoexpression of LOXL-2 from nuclear to cytoplasmic and HIF-1α immunoexpression might be an important factor in progression of OSCC.

The Multifaceted Roles of Copper in Cancer: A Trace Metal Element with Dysregulated Metabolism, but Also a Target or a Bullet for Therapy

In the human body, copper (Cu) is a major and essential player in a large number of cellular mechanisms and signaling pathways. The involvement of Cu in oxidation-reduction reactions requires close regulation of copper metabolism in order to avoid toxic effects. In many types of cancer, variations in copper protein levels have been demonstrated. These variations result in increased concentrations of intratumoral Cu and alterations in the systemic distribution of copper. Such alterations in Cu homeostasis may promote tumor growth or invasiveness or may even confer resistance to treatments. Once characterized, the dysregulated Cu metabolism is pinpointing several promising biomarkers for clinical use with prognostic or predictive capabilities. The altered Cu metabolism in cancer cells and the different responses of tumor cells to Cu are strongly supporting the development of treatments to disrupt, deplete, or increase Cu levels in tumors. The metallic nature of Cu as a chemical element is key for the development of anticancer agents via the synthesis of nanoparticles or copper-based complexes with antineoplastic properties for therapy. Finally, some of these new therapeutic strategies such as chelators or ionophores have shown promising results in a preclinical setting, and others are already in the clinic.

Linking LOXL2 to Cardiac Interstitial Fibrosis

Cardiovascular diseases (CVDs) are the leading causes of death worldwide. CVD pathophysiology is often characterized by increased stiffening of the heart muscle due to fibrosis, thus resulting in diminished cardiac function. Fibrosis can be caused by increased oxidative stress and inflammation, which is strongly linked to lifestyle and environmental factors such as diet, smoking, hyperglycemia, and hypertension. These factors can affect gene expression through epigenetic modifications. Lysyl oxidase like 2 (LOXL2) is responsible for collagen and elastin cross-linking in the heart, and its dysregulation has been pathologically associated with increased fibrosis. Additionally, studies have shown that, LOXL2 expression can be regulated by DNA methylation and histone modification. However, there is a paucity of data on LOXL2 regulation and its role in CVD. As such, this review aims to gain insight into the mechanisms by which LOXL2 is regulated in physiological conditions, as well as determine the downstream effectors responsible for CVD development.

Lysyl oxidase-like 2 promotes esophageal squamous cell carcinoma cell migration independent of catalytic activity

Lysyl oxidase-like 2 (LOXL2) is a member of the lysyl oxidase (LOX) family that contributes to tumor cell metastasis. Our previous data identified two splice variants of LOXL2 (i.e., LOXL2 Δ72 and Δ13) in esophageal squamous cell carcinoma (ESCC) cells that increased cell invasiveness and migration but had lower LOX activities than wild-type LOXL2 (LOXL2 WT). We generated a series of LOXL2 deletion mutants with different deleted biochemical domains and examined the relationship between the cell migration abilities and catalytic activities, as well as subcellular locations, of these deletion mutants compared with LOXL2 WT in ESCC cells to explore the mechanism of LOXL2-driven ESCC cell migration. Our results indicated that the deletion mutants of LOXL2 had impaired deamination enzymatic activity; LOXL2 ΔSRCR4, which lacks the fourth scavenger receptor cysteine-rich (SRCR) domain, had lower enzymatic activity; and LOXL2 Y689F had no catalytic activity compared with LOXL2 WT. However these two mutants stimulated greater cellular migration than LOXL2 WT. Furthermore, the degree of cell migration promoted by LOXL2 ΔLO (in which the LOX-like domain was deleted) was higher than that of LOXL2 WT, and LOXL2 ΔSRCR3, which does not have the third SRCR domain, had lower LOX activity and cellular migration ability than LOXL2 WT. These results suggested that LOXL2 promotes ESCC cell migration independent of catalytic activity.

Evolving roles of lysyl oxidase family in tumorigenesis and cancer therapy

The lysyl oxidase (LOX) family is comprised of LOX and four LOX-like proteins (LOXL1, LOXL2, LOXL3, and LOXL4), and mainly functions in the remodeling of extracellular matrix (ECM) and the cross-linking of collagen and elastic fibers. Recently, a growing body of research has demonstrated that LOX family is critically involved in the regulation of cancer cell proliferation, migration, invasion and metastasis. In this review, we discuss the roles of LOX family members in the development and progression of different types of human cancers. Furthermore, we also describe the potential inhibitors of LOX family proteins and highlight that LOX family might be an important therapeutic target for cancer therapy.

Exosomes: Carriers of Pro-Fibrotic Signals and Therapeutic Targets in Fibrosis

Exosomes are nano-sized extracellular vesicles that are released by a variety of cells. Exosomes contain cargo from cells they derived, including lipids, proteins and nucleic acids. The bilayer lipid membrane structure of exosomes protects these contents from degradation, allowing them for intercellular communication. The role of exosomes in fibrotic diseases is increasingly being valued. Exosomes, as carriers of profibrotic signals, are involved in the development of fibrotic diseases, and also regulate fibrosis by transmitting signals that inhibit fibrosis or inflammation. Exosomes mobilize and activate a range of effector cells by targeted delivery of bioactive information. Exosomes can also reflect the condition of cells, tissues and organisms, and thus become potential biomarkers of fibrotic diseases. Exosomes from bone marrow stem cells support biological signaling that regulates and inhibits fibrosis and thus initially used in the treatment of fibrotic diseases. This article briefly summarizes the role of exosomes in the pathogenesis and treatment of fibrotic diseases and raises some issues that remain to be resolved.

How hypoxia regulate exosomes in ischemic diseases and cancer microenvironment?

Exosomes, as natural occurring vesicles, play highly important roles in the behavior and fate of ischemic diseases and different tumors. Secretion, composition, and function of exosomes are remarkably influenced by hypoxia in ischemic diseases and tumor microenvironment. Exosomes secreted from hypoxic cells affect development, growth, angiogenesis, and progression in ischemic diseases and tumors through a variety of signaling pathways. In this review article, we discuss how hypoxia affects the quantity and quality of exosomes, and review the mechanisms by which hypoxic cell-derived exosomes regulate ischemic cell behaviors in both cancerous and noncancerous cells.

LOXL2 promotes oncogenic progression in alveolar rhabdomyosarcoma independently of its catalytic activity

Rhabdomyosarcoma (RMS) is the most common soft tissue malignancy in childhood and adolescence. Patients with the most aggressive histological variant have an unfavorable prognosis due to a high metastasis incidence. Lysyl oxidase-like 2 (LOXL2) is a lysyl oxidase, member of a family of extracellular matrix (ECM) crosslinking enzymes that recently have emerged as important regulators of tumor progression and metastasis. We report that LOXL2 is overexpressed in RMS, suggesting a potential role for LOXL2 in RMS oncogenic progression. Consistently, transient and stable LOXL2 knockdown decreased cell migratory and invasive capabilities in two ARMS cell lines. Furthermore, introduction of LOXL2 in RMS non-expressing cells using wild type or mutated (catalytically inactive) constructs resulted in increased cell migration, cell invasion and number and incidence of spontaneous lung metastasis in vivo, independently of its catalytic activity. To further study the molecular mechanism associated with LOXL2 expression, a pull-down assay on LOXL2-transfected cells was performed and analyzed by mass spectrometry. The intermediated filament protein vimentin was validated as a LOXL2-interactor. Thus, our results suggest an oncogenic role of LOXL2 in RMS by regulating cytoskeleton dynamics and cell motility capabilities.

Endothelium-mediated contributions to fibrosis

Fibrosis, characterized by abnormal and excessive deposition of extracellular matrix, results in compromised tissue and organ structure. This can lead to reduced organ function and eventual failure. Although activated fibroblasts, called myofibroblasts, are considered the central players in fibrosis, the contribution of endothelial cells to the inception and progression of fibrosis has become increasingly recognized. Endothelial cells can contribute to fibrosis by acting as a source of myofibroblasts via endothelial-mesenchymal transition (EndoMT), or by becoming senescent, by secretion of profibrotic mediators and pro-inflammatory cytokines, chemokines and exosomes, promoting the recruitment of immune cells, and by participating in vascular rarefaction and decreased angiogenesis. In this review, we provide an overview of the different aspects of fibrosis in which endothelial cells have been implicated.

Identification of two molecular subtypes in canine mast cell tumours through gene expression profiling

Mast cell tumours (MCTs) are common neoplasms in dogs and are usually regarded as potentially malignant. Several studies have attempted to identify biomarkers to better predict biological behaviours for this tumour. The aim of this study was to identify pathways connected to clinical and histopathological malignancies, shorter survival times, and poor prognoses associated with MCTs. We performed genome-wide gene expression analyses on tissues obtained from 15 dogs with single MCTs, and identified two distinct tumour subtypes—high-risk and low-risk—associated with differences in histological grades, survival times, Ki67 indices, and occurrence of death due the disease. Comparative analyses of RNA sequence profiles revealed 71 genes that were differentially expressed between high- and low-risk MCTs. In addition to these analyses, we also examined gene co-expression networks to explore the biological functions of the identified genes. The network construction revealed 63 gene modules, of which 4 were significantly associated with the more aggressive tumour group. Two of the gene modules positively correlated with high-risk MCTs were also associated with cell proliferation and extracellular matrix-related terms. At the top of the extracellular matrix module category, genes with functions directly related to those of cancer-associated fibroblasts (CAFs) were identified. Immunohistochemical analyses also revealed a greater number of CAFs in high-risk MCTs. This study provides a method for the molecular characterisation of canine MCTs into two distinct subtypes. Our data indicate that proliferation pathways are significantly involved in malignant tumour behaviours, which are known to be relevant for the induction and maintenance of MCTs. Finally, animals presenting high-risk MCTs overexpress genes associated with the extracellular matrix that can be robustly linked to CAF functions. We suggest that CAFs in the MCT stroma contribute to cancer progression.

Specific protein 1(SP1) regulates the epithelial-mesenchymal transition via lysyl oxidase-like 2(LOXL2) in pancreatic ductal adenocarcinoma

Specific protein 1 (SP1) is associated with aggressive behavior, invasive clinical phenotype and poor clinical outcomes in various cancers. We studied whether SP1 exerts its effect on invasiveness and promotion of the epithelial-mesenchymal transition (EMT) by regulating lysyl oxidase-like 2 (LOXL2) in pancreatic ductal adenocarcinoma (PDAC) cell lines. We showed that silencing of SP1 in MIA Paca-2 cell significantly decreased cell invasion and migration. In MIA Paca-2 cells, silencing of SP1 induced a reduction of LOXL2 expression, whereas LOXL2 silencing did not lead to a decrease in the expression of SP1. Chromatin immunoprecipitation assay demonstrated the binding of SP1 to LOXL2 promoter. Wound healing and transmigration assays also showed that transfection of both SP1 and LOXL2 siRNA induced most significant decrease of cell invasion and migration compared to either SP1 or LOXL2-only silenced cells. Finally, we investigated the prognostic value of SP1 in patients with PDAC and SP1/LOX2 expression was examined by immunochemistry. Univariate and multivariate analyses showed that tumor differentiation and co-expression of SP1 and LOXL2 were independent factors for disease-free survival. In summary, our study demonstrates that SP1 modulates EMT and is involved in tumor invasion and migration of PDAC cells through the regulation of LOXL2.

Extracellular Processing of Lysyl Oxidase-like 2 and Its Effect on Amine Oxidase Activity

Overexpression of lysyl oxidase-like 2 (LOXL2) is associated with several hepatic and vascular fibrotic diseases and tumor progression in some aggressive cancers. Secreted LOXL2 promotes extracellular matrix cross-linking by catalyzing the oxidative deamination of peptidyl lysine. A great deal remains to be learned about the post-translational modifications of LOXL2, including whether such modifications modulate enzymatic and disease-promoting activities; such knowledge would inform the development of potential therapies. We discovered that upon secretion in cell culture, LOXL2 undergoes proteolytic processing of the first two of four scavenger receptor cysteine-rich domains at the N-terminus. A similar pattern of processing was also evident in tissue extracts from an invasive ductal carcinoma patient. Processing occurred at ³¹⁴Arg-³¹⁵Phe-³¹⁶Arg-³¹⁷Lys↓-³¹⁸Ala-, implicating proprotein convertases. siRNA-mediated knockdown of proprotein convertases (furin, PACE4, and PC5/6), as well as incubation with their recombinant forms, showed that PACE4 is the major protease that acts on extracellular LOXL2. Unlike LOX, which requires cleavage of its propeptide for catalytic activation, cleavage of LOXL2 was not essential for tropoelastin oxidation or for cross-linking of collagen type IV in vitro. However, in the latter case, processing enhanced the extent of collagen cross-linking ∼2-fold at ≤10 nM LOXL2. These results demonstrate an important difference in the regulatory mechanisms for LOX and LOXL2 catalytic activity. Moreover, they pave the way for further studies of potential differential functions of LOXL2 isoforms in fibrosis and tumor progression.

Combatting Fibrosis: Exosome-Based Therapies in the Regression of Liver Fibrosis

Hepatic fibrosis results from chronic injury and inflammation in the liver and leads to cirrhosis, liver failure, and portal hypertension. Understanding the molecular mechanisms underlying hepatic fibrosis has advanced the prospect of developing therapies for regression of the disease. Resolution of fibrosis requires a reduction of proinflammatory and fibrogenic cytokines, a decrease in extracellular matrix (ECM) protein production, an increase in collagenase activity, and finally, a disappearance of activated myofibroblasts. Exosomes are nanovesicles of endocytic origin secreted by most cell types. They epigenetically reprogram and alter the phenotype of their recipient cells and hold great promise for the reversal of fibrosis. Recent studies have shown that exosomes function as conduits for intercellular transfer and contain all the necessary components to induce resolution of fibrosis, including the ability to (1) inhibit macrophage activation and cytokine secretion, (2) remodel ECM production and decrease fibrous scars, and (3) inactivate hepatic stellate cells, a major myofibroblast population. Here, we discuss the research involving the regression of hepatic fibrosis. We focus on the newly discovered roles of exosomes during fibrogenesis and as a therapy for fibrosis reversal. We also emphasize the novel discoveries of exosome‐based antifibrotic treatments in vitro and in vivo.

Lysyl oxidases regulate fibrillar collagen remodelling in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive scarring disease of the lung with few effective therapeutic options. Structural remodelling of the extracellular matrix [i.e. collagen cross-linking mediated by the lysyl oxidase (LO) family of enzymes (LOX, LOXL1-4)] might contribute to disease pathogenesis and represent a therapeutic target. This study aimed to further our understanding of the mechanisms by which LO inhibitors might improve lung fibrosis. Lung tissues from IPF and non-IPF subjects were examined for collagen structure (second harmonic generation imaging) and LO gene (microarray analysis) and protein (immunohistochemistry and western blotting) levels. Functional effects (collagen structure and tissue stiffness using atomic force microscopy) of LO inhibitors on collagen remodelling were examined in two models, collagen hydrogels and decellularized human lung matrices. LOXL1/LOXL2 gene expression and protein levels were increased in IPF versus non-IPF. Increased collagen fibril thickness in IPF versus non-IPF lung tissues correlated with increased LOXL1/LOXL2, and decreased LOX, protein expression. β-Aminoproprionitrile (β-APN; pan-LO inhibitor) but not Compound A (LOXL2-specific inhibitor) interfered with transforming growth factor-β-induced collagen remodelling in both models. The β-APN treatment group was tested further, and β-APN was found to interfere with stiffening in the decellularized matrix model. LOXL1 activity might drive collagen remodelling in IPF lungs. The interrelationship between collagen structural remodelling and LOs is disrupted in IPF lungs. Inhibition of LO activity alleviates fibrosis by limiting fibrillar collagen cross-linking, thereby potentially impeding the formation of a pathological microenvironment in IPF.

Summary: Transforming growth factor-β-induced collagen remodelling is driven by enhanced lysyl oxidase expression in idiopathic pulmonary fibrosis.

Crystal structure of human lysyl oxidase-like 2 (hLOXL2) in a precursor state

Lysyl oxidases (LOXs), a type of copper- and lysyl tyrosylquinone (LTQ) -dependent amine oxidase, catalyze the oxidative deamination of lysine residues of extracellular matrix (ECM) proteins such as elastins and collagens and generate aldehyde groups. The oxidative deamination of lysine represents the foundational step for the cross-linking of elastin and collagen and thus is crucial for ECM modeling. Despite their physiological significance, the structure of this important family of enzymes remains elusive. Here we report the crystal structure of human lysyl oxidase-like 2 (hLOXL2) at 2.4-Å resolution. Unexpectedly, the copper-binding site of hLOXL2 is occupied by zinc, which blocks LTQ generation and the enzymatic activity of hLOXL2 in our in vitro assay. Biochemical analysis confirms that copper loading robustly activates hLOXL2 and supports LTQ formation. Furthermore, the LTQ precursor residues in the structure are distanced by 16.6 Å, corroborating the notion that the present structure may represent a precursor state and that pronounced conformational rearrangements would be required for protein activation. The structure presented here establishes an important foundation for understanding the structure-function relationship of LOX proteins and will facilitate LOX-targeting drug discovery.

Dormant tumor cells expressing LOXL2 acquire a stem-like phenotype mediating their transition to proliferative growth

Recurrence of breast cancer disease years after treatment appears to arise from disseminated dormant tumor cells (DTC). The mechanisms underlying the outgrowth of DTC remain largely unknown. Here we demonstrate that dormant MCF-7 cells expressing LOXL2 acquire a cancer stem cell (CSC)-like phenotype, mediating their outgrowth in the 3D BME system that models tumor dormancy and outgrowth. Similarly, MCF-7-LOXL2 cells colonizing the lung transitioned from dormancy to metastatic outgrowth whereas MCF-7 cells remained dormant. Notably, epithelial to mesenchymal transition (EMT) of MCF-7-LOXL2 cells was required for their CSC-like properties and their transition to metastatic outgrowth. These findings were further supported by clinical data demonstrating that increase in LOXL2 mRNA levels correlates with increase in the mRNA levels of EMT and stem cells markers, and is also associated with decrease in relapse free survival of breast cancer patients. Notably, conditional hypoxia induced expression of endogenous LOXL2 in MCF-7 cells promoted EMT and the acquisition of a CSC-like phenotype, while knockdown of LOXL2 inhibited this transition. Overall, our results demonstrate that expression of LOXL2 endowed DTC with CSC-like phenotype driving their transition to metastatic outgrowth and this stem-like phenotype is dependent on EMT that can be driven by the tumor microenvironment.

Emerging role of LOXL2 in the promotion of pancreas cancer metastasis

Lysyl oxidase-like 2 (LOXL2) is associated with invasiveness and metastasis in cancer. We analyzed the prognostic impact of LOXL2 in pancreatic cancer patients and investigated the role of LOXL2 in pancreatic cancer cell lines. Immunohistochemical analysis was performed in samples from 80 patients and showed LOXL2 expression in 81.2% of patients with pancreatic cancer. Regarding recurrence patterns, LOXL2-positive tumors showed a significantly higher rate of distant recurrence. The 1-year and 3-year disease-free survival rates were 84.6% and 0.0%, respectively, for LOXL2-negative patients, and 27.8 % and 0.0 %, respectively, for LOXL2-positive patients. On univariate analysis, combined resection of major vessels, depth of invasion, tumor stage, and LOXL2- positive status were significant factors for poor prognosis. After identification of LOXL2 expression in pancreatic cancer cell lines, LOXL2-silenced and LOXL2-overexpressed cell lines were used to perform transwell invasion and transendothelial migration assays.

In vitro studies indicated that LOXL2 silencing in MIA PaCa-2 and PANC-1 cells induced a mesenchymal–epithelial transition (MET)-like process associated with decreased invasive and migratory properties. LOXL2 overexpression in AsPC-1 and BxPC-3 cells enhanced the epithelial-mesenchymal transition (EMT)-like process and increased migratory and invasive activity. These clinical and preclinical data confirm that higher LOXL2 expression is associated with the invasiveness of pancreatic cancer cells and the low survival rate of pancreatic cancer patients. Our results suggest the clinical value of LOXL2 as a therapeutic target in pancreatic cancer.

MiR-504 inhibits cell proliferation and invasion by targeting LOXL2 in non small cell lung cancer

BACKGROUND

MicroRNAs (miRNAs) play crucial roles in tumor initiation and development. The aim of the study was to explore the clinicopathological role and functional effects of miR-504 in non small cell lung cancer (NSCLC).

METHODS

Quantitative reverse transcription polymerase chain reaction (QRT-PCR) was applied to detect the expression of miR-504 in 55 cases of NSCLC tissues and matched adjacent normal tissues in NSCLC patients. MTT, colony formation and transwell invasion assays were performed to evaluate the effects of miR-504 on cell proliferation and invasion, respectively. Dual luciferase reporter assay was used to verify that LOXL2 was a direct target of miR-504. QRT-PCR and western blot analysis were performed to analyze mRNA and protein expression.

RESULTS

In the study, we demonstrated that miR-504 was notably downregulated in NSCLC tissues compared with adjacent normal tissues. Lower miR-504 expression positively correlated with lymph node metastasis and advanced TNM stage in patients. Furthermore, upregulation of miR-504 significantly inhibited cell proliferation, cell invasion and EMT process of NSCLC. QRT-PCR, western blot and luciferase reporter assays confirmed that miR-504 could bind to LOXL2 3'UTR region and regulate its expression. Moreover, ectopic expression of LOXL2 could rescue the inhibiting effects on cell proliferation and invasion induced by miR-504 in NSCLC cells.

CONCLUSIONS

Our results indicated that miR-504 functioned as a tumor suppressor in NSCLC and may serve as a target of NSCLC treatment.

Association between lysyl oxidase and fibrotic focus in relation with inflammation in breast cancer

We hypothesized that lysyl oxidase (LOX) contributes to the formation of fibrotic focus (FF) in association with inflammation and serves a significant role in breast carcinogenesis. In the present study, the association between the expression of LOX family members and FF with regards to with inflammation was analyzed, and the prognostic significance of LOX and FF in breast cancer was investigated. Immunohistochemical staining for LOX, LOX-like protein (LOXL) 1, LOXL2 and LOXL3 was performed in primary breast cancer tissues. The status of FF within the tumor was assessed, including size and grade. Levels of inflammatory markers, intratumoral and peritumoral lymphocyte infiltration were also evaluated. The clinicopathological characteristics were evaluated from the medical records of patients. In the present study, the expression of LOX family members was not associated with the presence of FF. FF was identified to be associated with intratumoral and peritumoral inflammation, tumor stage, larger tumor size, lymph node metastasis, high histologic grade, and p53 expression. LOX and LOXL3 were associated with intratumoral, and peritumoral inflammation. Furthermore, LOXL1 was associated with intratumoral inflammation and interleukin-4. In addition, LOX was associated with cluster of differentiation 8⁺ T cells. LOXL3 was associated with expression of ER and PR, and molecular subtype. In the survival analysis, overall survival time was statistically significantly longer in the FF-negative compared with that in the FF-positive group. In conclusion, it was demonstrated that FF and the expression of LOX family members were associated with inflammation in breast cancer. FF was associated with poor prognostic markers of breast cancer. Further studies are required to clarify the mechanisms underlying the association between the LOX family, FF and inflammation in breast cancer.

Lysyl Oxidase-like Protein LOXL2 Promotes Lung Metastasis of Breast Cancer

The lysyl oxidase-like protein LOXL2 has been suggested to contribute to tumor progression and metastasis, but in vivo evidence has been lacking. Here we provide functional evidence that LOXL2 is a key driver of breast cancer metastasis in two conditional transgenic mouse models of PyMT-induced breast cancer. LOXL2 ablation in mammary tumor cells dramatically decreased lung metastasis, whereas LOXL2 overexpression promoted metastatic tumor growth. LOXL2 depletion or overexpression in tumor cells does not affect extracellular matrix stiffness or organization in primary and metastatic tumors, implying a function for LOXL2 independent of its conventional role in extracellular matrix remodeling. In support of this likelihood, cellular and molecular analyses revealed an association of LOXL2 action with elevated levels of the EMT regulatory transcription factor Snail1 and expression of several cytokines that promote premetastatic niche formation. Taken together, our findings established a pathophysiologic role and new function for LOXL2 in breast cancer metastasis. Cancer Res; 77(21); 5846-59. ©2017 AACR.

Proteolytic processing of lysyl oxidase-like-2 in the extracellular matrix is required for crosslinking of basement membrane collagen IV

Lysyl oxidase-like-2 (LOXL2) is an enzyme secreted into the extracellular matrix that crosslinks collagens by mediating oxidative deamination of lysine residues. Our previous work demonstrated that this enzyme crosslinks the 7S domain, a structural domain that stabilizes collagen IV scaffolds in the basement membrane. Despite its relevant role in extracellular matrix biosynthesis, little is known about the structural requirements of LOXL2 that enable collagen IV crosslinking. In this study, we demonstrate that LOXL2 is processed extracellularly by serine proteases, generating a 65-kDa form lacking the first two scavenger receptor cysteine-rich domains. Site-specific mutagenesis to prevent proteolytic processing generated a full-length enzyme that is active in vitro toward a soluble substrate, but fails to crosslink insoluble collagen IV within the extracellular matrix. In contrast, the processed form of LOXL2 binds to collagen IV and crosslinks the 7S domain. Together, our data demonstrate that proteolytic processing is an important event that allows LOXL2-mediated crosslinking of basement membrane collagen IV.

Roles of Copper-Binding Proteins in Breast Cancer

Copper ions are needed in several steps of cancer progression. However, the underlying mechanisms, and involved copper-binding proteins, are mainly elusive. Since most copper ions in the body (in and outside cells) are protein-bound, it is important to investigate what copper-binding proteins participate and, for these, how they are loaded with copper by copper transport proteins. Mechanistic information for how some copper-binding proteins, such as extracellular lysyl oxidase (LOX), play roles in cancer have been elucidated but there is still much to learn from a biophysical molecular viewpoint. Here we provide a summary of copper-binding proteins and discuss ones reported to have roles in cancer. We specifically focus on how copper-binding proteins such as mediator of cell motility 1 (MEMO1), LOX, LOX-like proteins, and secreted protein acidic and rich in cysteine (SPARC) modulate breast cancer from molecular and clinical aspects. Because of the importance of copper for invasion/migration processes, which are key components of cancer metastasis, further insights into the actions of copper-binding proteins may provide new targets to combat cancer.

ZEB1 induces LOXL2-mediated collagen stabilization and deposition in the extracellular matrix to drive lung cancer invasion and metastasis

Lung cancer is the leading cause of cancer-related deaths, primarily due to distant metastatic disease. Metastatic lung cancer cells can undergo an epithelial-to-mesenchymal transition (EMT) regulated by various transcription factors, including a double-negative feedback loop between the microRNA-200 (miR-200) family and ZEB1, but the precise mechanisms by which ZEB1-dependent EMT promotes malignancy remain largely undefined. Although the cell-intrinsic effects of EMT are important for tumor progression, the reciprocal dynamic crosstalk between mesenchymal cancer cells and the extracellular matrix (ECM) is equally critical in regulating invasion and metastasis. Investigating the collaborative effect of EMT and ECM in the metastatic process reveals increased collagen deposition in metastatic tumor tissues as a direct consequence of amplified collagen gene expression in ZEB1-activated mesenchymal lung cancer cells. In addition, collagen fibers in metastatic lung tumors exhibit greater linearity and organization as a result of collagen crosslinking by the lysyl oxidase (LOX) family of enzymes. Expression of the LOX and LOXL2 isoforms is directly regulated by miR-200 and ZEB1, respectively, and their upregulation in metastatic tumors and mesenchymal cell lines is coordinated to that of collagen. Functionally, LOXL2, as opposed to LOX, is the principal isoform that crosslinks and stabilizes insoluble collagen deposition in tumor tissues. In turn, focal adhesion formation and FAK/SRC signaling is activated in mesenchymal tumor cells by crosslinked collagen in the ECM. Our study is the first to validate direct regulation of LOX and LOXL2 by the miR-200/ZEB1 axis, defines a novel mechanism driving tumor metastasis, delineates collagen as a prognostic marker, and identifies LOXL2 as a potential therapeutic target against tumor progression.

Lysyl Oxidase-like-2 Cross-links Collagen IV of Glomerular Basement Membrane

The 7S dodecamer is recognized as an important structural cross-linking domain of collagen IV networks that provide mechanical stability to basement membranes, a specialized form of extracellular matrix essential for the development and maintenance of tissue architecture. Although the 7S dodecamer is stabilized by covalent cross-linking, the molecular mechanism by which such cross-links are formed has not been revealed. Here, we aimed to identify the enzyme(s) that cross-links the 7S dodecamer and characterize its expression in the kidney glomerulus. Pharmacological inhibition of candidate extracellular matrix enzymes revealed that lysyl oxidase activity is required for cross-linking of 7S polypeptides. Among all lysyl oxidase family members, lysyl oxidase-like-2 (LOXL2) was identified as the isoform cross-linking collagen IV in mouse embryonal PFHR-9 cells. Biochemical analyses revealed that LOXL2 readily promoted the formation of lysyl-derived cross-links in the 7S dodecamer but not in the NC1 domain. We also established that LOXL2 is the main lysyl oxidase family member present in the glomerular extracellular matrix. Altogether, we demonstrate that LOXL2 is a novel component of the molecular machinery that forms cross-linked collagen IV networks, which are essential for glomerular basement membrane stability and molecular ultrafiltration function.

A simple method to induce hypoxia-induced vascular endothelial growth factor-A (VEGF-A) expression in T24 human bladder cancer cells

Angiogenesis is an essential process for the establishment, development, and dissemination of several malignant tumors including bladder cancer. The hypoxic condition promotes the stabilization of hypoxia-inducible factor 1 alpha (HIF-1α), which translocates to the nucleus to mediate angiogenic factors including the vascular endothelial growth factor A (VEGF-A). AnaeroGen system was developed for microbiology area to create a low oxygen tension required to the growth of anaerobic bacteria. Here, we hypothesized the use of AnaeroGen system to induce hypoxia in T24 human bladder carcinoma cells, in order to promote the overexpression of VEGF-A. T24 cells were cultured in six-well plates containing McCoy medium. Exposures of T24 cells to hypoxia for 1, 8, 24, and 48 h were performed using the Oxoid AnaeroGen system, while T24 cells under normoxia were used as control. The expression of VEGF-A and HIF-1α was analyzed by real-time PCR. ELISA for HIF-1α was carried out. The VEGF-A expression increased significantly by Oxoid AnaeroGen-induced hypoxia in a time-depending manner, reaching the peak in 48 h of hypoxia. Although HIF-1α mRNA was not changed, HIF-1α protein was increased in the presence of hypoxia, reaching a peak at 8 h. These results demonstrated that the Oxoid AnaeroGen system is a simple method to expose T24 cells to hypoxia and efficiently to upregulate VEGF expression in T24 cells.

Prevention and treatment of cirrhotic portal hypertension: New cellular and molecular targets

Cirrhotic portal hypertension results from a variety of pathological conditions including decreased expression of endothelial NO synthase and lysyl oxidase-like 2, newly formed vessels and pathological hepatic sinusoid reconstruction. Dark chocolate, coffee and green tea polyphenol can improve endothelial dysfunction and inhibit angiogenesis and thus may be new options for treating and preventing the progression of cirrhotic portal hypertension.

Lysyl Oxidase Isoforms and Potential Therapeutic Opportunities for Fibrosis and Cancer

INTRODUCTION

The lysyl oxidase family of enzymes is classically known as being required for connective tissue maturation by oxidizing lysine residues in elastin and lysine and hydroxylysine residues in collagen precursors. The resulting aldehydes then participate in cross-link formation, which is required for normal connective tissue integrity. These enzymes have biological functions that extend beyond this fundamental biosynthetic role, with contributions to angiogenesis, cell proliferation, and cell differentiation. Dysregulation of lysyl oxidases occurs in multiple pathologies including fibrosis, primary and metastatic cancers, and complications of diabetes in a variety of tissues.

AREAS COVERED

This review summarizes the major findings of novel roles for lysyl oxidases in pathologies, and highlights some of the potential therapeutic approaches that are in development and which stem from these new findings.

EXPERT OPINION

Fundamental questions remain regarding the mechanisms of novel biological functions of this family of proteins, and regarding functions that are independent of their catalytic enzyme activity. However, progress is underway in the development of isoform-specific pharmacologic inhibitors, potential therapeutic antibodies and gaining an increased understanding of both tumor suppressor and metastasis promotion activities. Ultimately, this is likely to lead to novel therapeutic agents.

Exosomes from hypoxic endothelial cells have increased collagen crosslinking activity through up-regulation of lysyl oxidase-like 2

Exosomes are important mediators of intercellular communication. Additionally, they contain a variety of components capable of interacting with the extracellular matrix (ECM), including integrins, matrix metalloproteinases and members of the immunoglobin superfamily. Despite these observations, research on exosome-ECM interactions is limited. Here, we investigate whether the exosome-associated lysyl oxidase family member lysyl oxidase-like 2 (LOXL2) is involved in ECM remodelling. We found that LOXL2 is present on the exterior of endothelial cell (EC)-derived exosomes, placing it in direct vicinity of the ECM. It is up-regulated twofold in EC-derived exosomes cultured under hypoxic conditions. Intact exosomes from hypoxic EC and LOXL2 overexpressing EC show increased activity in a fluorometric lysyl oxidase enzymatic activity assay as well as in a collagen gel contraction assay. Concordantly, knockdown of LOXL2 in exosome-producing EC in both normal and hypoxic conditions reduces activity of exosomes in both assays. Our findings show for the first time that ECM crosslinking by EC-derived exosomes is mediated by LOXL2 under the regulation of hypoxia, and implicate a role for exosomes in hypoxia-regulated focal ECM remodelling, a key process in both fibrosis and wound healing.

Lysyl oxidase-like 2 represses Notch1 expression in the skin to promote squamous cell carcinoma progression

Lysyl oxidase-like 2 (LOXL2) is involved in a wide range of physiological and pathological processes, including fibrosis and tumor progression, implicating intracellular and extracellular functions. To explore the specific in vivo role of LOXL2 in physiological and tumor contexts, we generated conditional gain- and loss-of-function mouse models. Germ-line deletion of Loxl2 promotes lethality in half of newborn mice mainly associated to congenital heart defects, while Loxl2 overexpression triggers male sterility due to epididymal dysfunction caused by epithelial disorganization, fibrosis and acute inflammation. Remarkably, when challenged to chemical skin carcinogenesis, Loxl2-overexpressing mice increased tumor burden and malignant progression, while Loxl2-deficient mice exhibit the opposite phenotypes. Loxl2 levels in premalignant tumors negatively correlate with expression of epidermal differentiation markers and components of the Notch1 pathway. We show that LOXL2 is a direct repressor of NOTCH1. Additionally, we identify an exclusive expression pattern between LOXL2 and members of the canonical NOTCH1 pathway in human HNSCC. Our data identify for the first time novel LOXL2 roles in tissue homeostasis and support it as a target for SCC therapy.

LOXL2 induces aberrant acinar morphogenesis via ErbB2 signaling

INTRODUCTION

Lysyl oxidase-like 2 (LOXL2) is a matrix-remodeling enzyme that has been shown to play a key role in invasion and metastasis of breast carcinoma cells. However, very little is known about its role in normal tissue homeostasis. Here, we investigated the effects of LOXL2 expression in normal mammary epithelial cells to gain insight into how LOXL2 mediates cancer progression.

METHODS

LOXL2 was expressed in MCF10A normal human mammary epithelial cells. The 3D acinar morphogenesis of these cells was assessed, as well as the ability of the cells to form branching structures on extracellular matrix (ECM)-coated surfaces. Transwell-invasion assays were used to assess the invasive properties of the cells. Clinically relevant inhibitors of ErbB2, lapatinib and Herceptin (traztuzumab), were used to investigate the role of ErbB2 signaling in this model. A retrospective study on a previously published breast cancer patient dataset was carried out by using Disease Specific Genomic Analysis (DSGA) to investigate the correlation of LOXL2 mRNA expression level with metastasis and survival of ErbB2-positive breast cancer patients.

RESULTS

Fluorescence staining of the acini revealed increased proliferation, decreased apoptosis, and disrupted polarity, leading to abnormal lumen formation in response to LOXL2 expression in MCF10A cells. When plated onto ECM, the LOXL2-expressing cells formed branching structures and displayed increased invasion. We noted that LOXL2 induced ErbB2 activation through reactive oxygen species (ROS) production, and ErbB2 inhibition by using Herceptin or lapatinib abrogated the effects of LOXL2 on MCF10A cells. Finally, we found LOXL2 expression to be correlated with decreased overall survival and metastasis-free survival in breast cancer patients with ErbB2-positive tumors.

CONCLUSIONS

These findings suggest that LOXL2 expression in normal epithelial cells can induce abnormal changes that resemble oncogenic transformation and cancer progression, and that these effects are driven by LOXL2-mediated activation of ErbB2. LOXL2 may also be a beneficial marker for breast cancer patients that could benefit most from anti-ErbB2 therapy.

Human lysyl oxidase-like 2

Lysyl oxidase like-2 (LOXL2) belongs to the lysyl oxidase (LOX) family, which comprises Cu(2+)- and lysine tyrosylquinone (LTQ)-dependent amine oxidases. LOXL2 is proposed to function similarly to LOX in the extracellular matrix (ECM) by promoting crosslinking of collagen and elastin. LOXL2 has also been proposed to regulate extracellular and intracellular cell signaling pathways. Dysregulation of LOXL2 has been linked to many diseases, including cancer, pro-oncogenic angiogenesis, fibrosis and heart diseases. In this review, we will give an overview of the current understandings and hypotheses regarding the molecular functions of LOXL2.

Inhibition of BMP signaling suppresses metastasis in mammary cancer

Bone Morphogenetic Proteins (BMPs) are secreted cytokines/growth factors that play differing roles in cancer. BMPs are overexpressed in human breast cancers, but loss of BMP signaling in mammary carcinomas can accelerate metastasis. We show that human breast cancers display active BMP signaling, which is rarely downregulated or homozygously deleted. We hypothesized that systemic inhibition of BMP signaling in both the tumor and the surrounding microenvironment could prevent tumor progression and metastasis. To test this hypothesis, we used DMH1, a BMP antagonist, in MMTV.PyVmT expressing mice. Treatment with DMH1 reduced lung metastasis and the tumors were less proliferative and more apoptotic. In the surrounding tumor microenvironment, treatment with DMH1 altered fibroblasts, lymphatic vessels and macrophages to be less tumor promoting. These results indicate that inhibition of BMP signaling may successfully target both the tumor and the surrounding microenvironment to reduce tumor burden and metastasis.

LOXL2 catalytically inactive mutants mediate epithelial-to-mesenchymal transition

Lysyl-oxidase-like 2 (LOXL2) is a member of the lysyl oxidase family that catalyzes the cross-linking of collagens or elastins in the extracellular matrix, thus regulating the tensile strength of tissues. However, many reports have suggested different intracellular roles for LOXL2, including the ability to regulate gene transcription and tumor progression. We previously reported that LOXL2 mediates epithelial-to-mesenchymal transition (EMT) by Snail1-dependent and independent mechanisms, related to E-cadherin silencing and downregulation of epidermal differentiation and cell polarity components, respectively. Whether or not the catalytic activity of LOXL2 is required to induce/sustain EMT is actually unknown. Here we show that LOXL2 catalytic inactive mutants collaborate with Snail1 in E-cadherin gene repression to trigger EMT and, in addition, promote FAK/Src pathway activation to support EMT. These findings reveal a non-conventional role of LOXL2 on regulating epithelial cell plasticity.

Coevolution of the tumor microenvironment revealed by quantum dot-based multiplexed imaging of hepatocellular carcinoma

AIM

This study aimed to provide new insights into the mechanisms of hepatocellular carcinoma (HCC) invasion by simultaneously imaging tumor cells and major components of the tumor microenvironment.

MATERIALS & METHODS

Formalin-fixed paraffin-embedded human HCC tissues were studied by conventional immunohistochemistry and quantum dot-based multiplexed imaging to reveal type IV collagen, LOX and tumor angiogenesis.

RESULTS

Type IV collagen degradation and repatterning in the extracellular matrix (ECM) was a continuous process, making the ECM harder, although more fragile and less resistant to cancer invasion. The distribution of LOX among cancer nests was heterogeneous, with higher expression in small cancer nests and lower expression in large cancer nests. LOX expression in cancer cells was associated with rigid stroma and tumor angiogenesis. Tumor angiogenesis occurred with type IV collagen presence. At the cancer invasion front, the ECM was hydrolyzed, with the prominent linear reorientation of type IV collagen surrounding cancer nests adjacent to neovessels.

CONCLUSION

The visualization of the temporal-spatial relationship between type IV collagen, LOX and tumor angiogenesis revealed the coevolution process of HCC cells and their microenvironment, emphasizing an active role of the ECM during cancer invasion.

Human copper-dependent amine oxidases

Copper amine oxidases (CAOs) are a class of enzymes that contain Cu(2+) and a tyrosine-derived quinone cofactor, catalyze the conversion of a primary amine functional group to an aldehyde, and generate hydrogen peroxide and ammonia as byproducts. These enzymes can be classified into two non-homologous families: 2,4,5-trihydroxyphenylalanine quinone (TPQ)-dependent CAOs and the lysine tyrosylquinone (LTQ)-dependent lysyl oxidase (LOX) family of proteins. In this review, we will focus on recent developments in the field of research concerning human CAOs and the LOX family of proteins. The aberrant expression of these enzymes is linked to inflammation, fibrosis, tumor metastasis/invasion and other diseases. Consequently, there is a critical need to understand the functions of these proteins at the molecular level, so that strategies targeting these enzymes can be developed to combat human diseases.