Lysyl oxidase engineered lipid nanovesicles for the treatment of triple negative breast cancer.

In the field of oncology research, a deeper understanding of tumor biology has shed light on the role of environmental conditions surrounding cancer cells. In this regard, targeting the tumor microenvironment has recently emerged as a new way to access this disease. In this work, a novel extracellular matrix (ECM)-targeting nanotherapeutic was engineered using a lipid-based nanoparticle chemically linked to an inhibitor of the ECM-related enzyme, lysyl oxidase 1 (LOX), that inhibits the crosslinking of elastin and collagen fibers. We demonstrated that, when the conjugated vesicles were loaded with the chemotherapeutic epirubicin, superior inhibition of triple negative breast cancer (TNBC) cell growth was observed both in vitro and in vivo. Moreover, in vivo results displayed prolonged survival, minimal cytotoxicity, and enhanced biocompatibility compared to free epirubicin and epirubicin-loaded nanoparticles. This all-in-one nano-based ECM-targeting chemotherapeutic may provide a key-enabling technology for the treatment of TNBC.

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-ß 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.

Co-administration of resveratrol and beta-aminopropionitrile attenuates liver fibrosis development via targeting lysyl oxidase in CCl4-induced liver fibrosis in rats.

Objectives: In the current study, we aimed to investigate the effect of administration of resveratrol (RES) and beta-aminopropionitrile (BAPN) separately and together on the liver fibrosis progression via regulation of the gene expression and protein level of lysyl oxidase (LOX).Materials and methods: The six-week old Wistar rats received carbon tetrachloride (CCl4) intraperitoneally and RES and BAPN were administrated orally for eight weeks. The hepatoprotective effects of RES, BAPN, and combination treatment were evaluated. Then the hepatic protein and gene expression levels of LOX were measured.Results: Both RES and BAPN showed the antifibrotic effect through the reduction of collagen fiber bundles, hepatic hydroxyproline content, and protein level of LOX. The antifibrotic effect increased when RES and BAPN up-taken together.Conclusion: The co-administration of RES and BAPN can be considered as a promising therapeutic approach via targeting LOX.

Blocking Surgically Induced Lysyl Oxidase Activity Reduces the Risk of Lung Metastases.

Surgery remains the most successful curative treatment for cancer. However, some patients with early-stage disease who undergo surgery eventually succumb to distant metastasis. Here, we show that in response to surgery, the lungs become more vulnerable to metastasis due to extracellular matrix remodeling. Mice that undergo surgery or that are preconditioned with plasma from donor mice that underwent surgery succumb to lung metastases earlier than controls. Increased lysyl oxidase (LOX) activity and expression, fibrillary collagen crosslinking, and focal adhesion signaling contribute to this effect, with the hypoxic surgical site serving as the source of LOX. Furthermore, the lungs of recipient mice injected with plasma from post-surgical colorectal cancer patients are more prone to metastatic seeding than mice injected with baseline plasma. Downregulation of LOX activity or levels reduces lung metastasis after surgery and increases survival, highlighting the potential of LOX inhibition in reducing the risk of metastasis following surgery.

Expresión de la lisil oxidasa (LOX) en la pared vascular: mecanismos implicados en la regulación de la LOX por lipoproteínas de baja densidad / Lysyl oxidase (LOX) expression in the vascular wall: mechanisms involved in LOX regulation by low density lipoproteins

Introducción. La lisil oxidasa (LOX) es una enzima implicada en la estabilización de la matriz extracelular que podría ser clave en la disfunción endotelial desencadenada por factores de riesgo aterosclerótico. Hemos analizado el patrón de expresión de las enzimas de la familia de LOX en la pared vascular y determinado los mecanismos implicados en la modulación de esta enzima por lipoproteínas de baja densidad (LDL) en células vasculares. Material y métodos. La expresión de la LOX y de otras enzimas de la familia se analizó en arterias coronarias humanas, aorta abdominal porcina, células endoteliales de aorta porcina (PAEC) y células musculares lisas (CML), mediante inmunohistoquímica, RT-PCR y/o Northern-blot. Resultados. Hemos observado grandes diferencias en el patrón de expresión de las enzimas de la familia de la LOX en la pared vascular. La LOX se expresa preferentemente en el endotelio y en la adventicia de arterias coronarias humanas y de aorta porcina. El tratamiento con LDL disminuye la expresión de esta enzima en PAEC y CML en cultivo. Este efecto se produce por un mecanismo transcripcional, sin que se vea afectada la estabilidad del mensajero. La esfingosina-1-fosfato (S1P), componente bioactivo de las LDL, no modificó la expresión de la LOX, y la inhibición de proteínas G sensibles a toxina pertúsica no revertió el efecto de las lipoproteínas. Sin embargo, observamos que la inhibición del procesamiento lisosomal con cloroquina previno la disminución de la expresión de la LOX causada por las LDL. Conclusiones. La disminución de la expresión de la LOX por LDL requiere el procesamiento lisosomal de la lipoproteína. La regulación de esta enzima por lipoproteínas y su fuerte expresión en el endotelio vascular apoyan el papel de la LOX en la disfunción endotelial desencadenada por la hipercolesterolemia y sugieren su contribución en el proceso aterosclerótico (AU)

Introduction. Lysyl oxidase (LOX) is an enzyme involved in extracellular matrix stabilization that could play a key role in endothelial dysfunction triggered by atherosclerotic risk factors. We analyzed the expression pattern of LOX isoenzymes in the vascular wall and determined the molecular mechanisms involved in low density lipoproteins (LDL)-mediated LOX modulation in vascular cells. Material and methods. LOX isoenzyme expression was analyzed in human coronary arteries, porcine abdominal aorta, porcine aortic endothelial cells (PAEC) and vascular smooth muscle cells (VSMC) by immunohistochemistry, RT-PCR and/or Northern-blot. Results. We observed marked differences in the vascular expression pattern of LOX isoenzymes. LOX was preferentially expressed in endothelium and adventitia in human coronary arteries and in porcine abdominal aorta. LDL decreased LOX expression in both PAEC and VSMC in culture. This effect was due to a transcription mechanism that did not seem to alter mRNA stability. Sphingosine-1-phosphate (S1P), an LDL bioactive component, did not modify LOX expression, and inhibition of pertussis toxin-sensitive G-proteins did not prevent the effect of lipoproteins. Finally, we observed that inhibition of lysosomal processing with chloroquine abolished the LDL-induced LOX downregulation. Conclusions. LOX downregulation by LDL requires lipoprotein lysosomal processing. Both LOX regulation by lipoproteins and its strong endothelial expression support the role of this enzyme in endothelial dysfunction triggered by hypercholesterolemia and suggest that it contributes to the atherosclerotic process (AU)

Immunohistochemical localization of lysyl oxidase in normal human skin.

Lysyl oxidase (EC 1.4.3.13), a copper-dependent enzyme which catalyses the formation of aldehyde cross-links, and acts primarily on collagen and elastin, is known to be increased during wound healing and in fibrotic disorders including liver cirrhosis and atherosclerosis, and to be decreased in some hereditary connective tissue diseases and in malignant cell lines. A recent study showed that lysyl oxidase might possess tumour suppressor activity as an antioncogene for ras. Little is known about the localization of this enzyme in human skin. In this study, we determined immunohistochemically the localization of lysyl oxidase in normal skin of young and elderly subjects obtained from sun-exposed and unexposed regions of the body. All skin samples tested had similar distributions of lysyl oxidase. The enzyme was present both extracellularly and intracellularly. Extracellularly, a few granular aggregates of immunoreactants were observed along collagen and elastic fibres. These granules were more common in the adventitial portion of the dermis than in the reticular portion. Of all sun-exposed and unexposed regions studied, the skin of the face displayed the greatest amount of extracellular immunoreactants. Immunopositive granules were observed intracellularly in fibroblasts, vascular endothelial cells, sweat glands, sebaceous glands, arrector pili muscles and some keratinocytes. These findings provide evidence that, as suggested in recent reports, lysyl oxidase may have a variety of intracellular functions.

Purification, properties and influence of dietary copper on accumulation and functional activity of lysyl oxidase in rat skin.

Lysyl oxidase (protein-lysine 6-oxidase; EC 1.4.3.13) is a copper-containing enzyme that functions extracellularly and catalyses the oxidative deamination of peptidyl lysine. Lysyl oxidase was purified 150-175-fold from urea extracts of rat skin and uteri. Features of the enzyme were similar to those reported previously for lysyl oxidase obtained from rat aorta and bovine ligamenture. However, both approximately 40 and approximately 32 kDa polypeptide chains could be isolated from rat skin with apparent lysyl oxidase activity. Antibodies raised in chickens against the approximately 40 kDa form of lysyl oxidase detected the approximately 32 kDa form in immunoblots. Consequently it is inferred that the approximately 32 kDa form of lysyl oxidase is processed from the approximately 40 kDa form of the enzyme. The antibodies were also used to prepare anti(rat lysyl oxidase) affinity columns to facilitate the separation of lysyl oxidase from other proteins in studies to assess the extent to which lysyl oxidase serves as a reservoir for skin copper. At 16 h after an oral dose of copper, as 67Cu, about 6-8% of the total 67Cu incorporated into rat skin was found in association with lysyl oxidase. The lysyl oxidase concentration in rat skin was 2.5-7.5 nmol/g (determined by e.l.i.s.a.). Changing the copper status of rats by feeding a diet deficient in copper did not appear to influence lysyl oxidase accumulation in skin nor the percentage of incorporation of 67Cu in skin as lysyl oxidase. However, when rats were deprived of copper, the functional activity of lysyl oxidase in skin was one-third to one-half the normal values.

Ultrastructural immunolocalization of lysyl oxidase in vascular connective tissue.

The localization of lysyl oxidase was examined in calf and rat aortic connective tissue at the ultrastructural level using polyclonal chicken anti-lysyl oxidase and gold conjugated rabbit anti-chicken immunoglobulin G to identify immunoreactive sites. Electron microscopy of calf aortic specimens revealed discrete gold deposits at the interface between extracellular bundles of amorphous elastin and the microfibrils circumferentially surrounding these bundles. The antibody did not react with microfibrils which were distant from the interface with elastin. There was negligible deposition of gold within the bundles of amorphous elastin and those few deposits seen at these sites appeared to be associated with strands of microfibrils. Lysyl oxidase was similarly localized in newborn rat aorta at the interface between microfibrils and nascent elastin fibers. Gold deposits were not seen in association with extracellular collagen fibers even after collagen-associated proteoglycans had been degraded by chondroitinase ABC. However, the antibody did recognize collagen-bound lysyl oxidase in collagen fibers prepared from purified collagen to which the enzyme had been added in vitro. No reaction product was seen if the anti-lysyl oxidase was preadsorbed with purified lysyl oxidase illustrating the specificity of the antibody probe. The present results are consistent with a model of elastogenesis predicting the radial growth of the elastin fiber by the deposition and crosslinking of tropoelastin units at the fiber-microfibril interface.

Monoclonal antibodies to human lysyl oxidase.

Hybridoma antibodies against human lysyl oxidase were produced by fusing Sp. 2.0-Ag 14 myeloma cells with spleen cells from mice hyperimmunized with lysyl oxidase isolated from umbilical cords. Hybridomas positive by enzyme-linked immunosorbent assay (ELISA) for human lysyl oxidase were cloned by the dilution method. Eight hybridomas producing antibodies were isolated, three of which also recognized purified bovine aortic lysyl oxidase in an ELISA. One of these antibodies, monoclonal antibody I, was purified and attached to Sepharose CL-4B. The immobilized antibody was effective in binding an enzymatically active 30,000 dalton species. Immunoblot analysis of four of these antibodies showed reactivity against the 30,000 dalton catalytically active enzyme and the 24,000 dalton fragment of lysyl oxidase. These monoclonal antibodies should be useful tools for studying the localization and biosynthesis of lysyl oxidase.

Partial characterization of lysyl oxidase from several human tissues.

Lysyl oxidase activity was assayed in urea extracts of a number of human tissues, proving to be highest in skin. Antibodies to human placental lysyl oxidase completely inhibited the activity of crude lysyl oxidase from all the human tissues studied, with no significant differences in the amounts of antiserum required for 50% inhibition. By contrast, marked differences were found in this value between skin tissue samples from different species. The Mr of lysyl oxidase in crude extracts of human skin and in the medium of cultured human skin fibroblasts was 30 000 by gel filtration, no active species with a higher Mr being detectable. Four forms of lysyl oxidase activity were seen in DEAE-cellulose chromatography of urea extract from human skin, all having Mr 30 000. Antibodies to human placental lysyl oxidase stained a 30 000-Mr protein in urea extracts of all the human tissues studied and in the medium of cultured human skin fibroblasts when examined by immunoblotting after sodium dodecyl sulphate/polyacrylamide-slab-gel electrophoresis, but they also stained high-Mr material. The findings suggest that there are no immunologically distinct lysyl oxidase isoenzymes in the various human tissues and that the true Mr of lysyl oxidase in crude urea extracts is 30 000.

Immunological characterization of bovine lysyl oxidase.

Antibodies to homogeneously purified bovine aortic lysyl oxidase were prepared in chickens. The chicken anti-lysyl oxidase antiserum effectively inhibited bovine aortic lysyl oxidase activity. Non-immune antiserum from chickens, goats and humans was found to enhance bovine aortic lysyl oxidase activity, while non-immune rabbit serum inhibited enzyme activity. A competitive ELISA was developed to monitor immunoreactive lysyl oxidase during purification. Chromatography of bovine lysyl oxidase on Sephacryl S-200, the final step in purification, revealed two peaks of immunoreactive lysyl oxidase. The large molecular weight peak appears to contain inactive multimeric forms of the enzyme.

Human placental lysyl oxidase. Purification, partial characterization, and preparation of two specific antisera to the enzyme.

Lysyl oxidase from human placentas gave four catalytically active forms on DEAE-cellulose chromatography in 6 M urea. The first tow of these were combined to form pool I and the remaining two to form pool II. Pool I was purified to homogeneity, while the final pool II enzyme usually had one minor contaminant. The molecular weight of both enzyme pools was identical, being about 30,000 by gel filtration in 6 M urea and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. No distinct differences were found between the two pools in amino acid composition, specific activity, or the use of various substrates. Two antisera were prepared, one to the total enzyme protein (pools I and II) and the other to pool I. Both antisera inhibited and precipitated crude placental lysyl oxidase, the two enzyme pools, and crude human skin fibroblast enzyme, there being no differences between the various enzyme forms. Both antisera also stained the two enzyme pools in immunoblotting of denatured proteins. The data suggest that there are no major catalytic, molecular, or immunological differences between the multiple forms of human lysyl oxidase. An antiserum prepared to any of the enzyme forms can, therefore, probably be used to study the total enzyme protein.

Biochemical and immunochemical study of lysyl oxidase in experimental hepatic fibrosis in the rat.

Lysyl oxidase catalyzes the crosslinking of collagen and elastin. Lysyl oxidase activity was measured and localized in rat liver during the evolution of hepatic fibrosis induced by CCl4. Enzyme activity measured with DL-[6-3H]-lysine-labeled collagen substrates in liver and plasma increased sharply after approximately 3 wk of injection, reached a maximum at 6 wk, and then decreased. The increase in activity correlated histologically with early connective tissue septa formation, and the magnitude of increase was significantly greater than that found for the intracellular collagen biosynthetic enzymes protocollagen prolyl hydroxylase and lysyl hydroxylase. Indirect immunofluorescence studies showed that lysyl oxidase was present in association with collagen in the extracellular space. However, it was not possible to correlate the distribution pattern with a particular liver cell type. These observations suggest that serial measurements of lysyl oxidase activity in liver or plasma may be useful for correlating changes in connective tissue formation with histologic connective tissue deposition.

The existence of inhibited lysyl oxidase and the presence of multiple forms.

Considerable difficulty in puriying tissue lysyl oxidase has been previously encountered and the cause of this difficulty has now been ascertained. For these studies, we have used blood plasma lysyl oxidase as a model system. Blood plasma has been shown to contain considerable lysyl oxidase activity. The enzyme exists in a partially or completely inhibited state. Homogeneous preparations of the enzyme from the blood have been obtained by two different methods. Method A yields one form of lysyl oxidase while Method B yields three forms of the enzyme. The methods for the purification of the enzyme and some properties of the enzyme and preliminary data on the lysyl oxidase inhibitor will be discussed.