Philip Trackman

The Forsyth Institute

Lysyl oxidase (LOX) is a facilitator of extracellular matrix cross-linking. Using newly developed megakaryocyte-specific LOX knockout mice, we show that LOX expressed in these scarce bone marrow cells affects bone volume and collagen architecture in a sex-dependent manner.

Oral cancer is primarily squamous-cell carcinoma with a 5-year survival rate of approximately 50%. Lysyl oxidase (LOX) participates in collagen and elastin maturation. The propeptide of LOX is released as an 18 kDa protein (LOX-PP) in the extracellular environment by procollagen C-proteinases and has tumor-inhibitory properties. A polymorphism in t...

This Special Issue on lysyl oxidases, which are proteins derived from five related genes known as Lox, and Loxl1–Loxl4, brings together articles that reflect some of the diverse approaches and perspectives needed to better understand the biology of these multifunctional proteins [...]

Lysyl oxidases are multifunctional proteins derived from five lysyl oxidase paralogues (LOX) and lysyl oxidase-like 1 through lysyl oxidase-like 4 (LOXL1–LOXL4). All participate in the biosynthesis of and maturation of connective tissues by catalyzing the oxidative deamination of lysine residues in collagens and elastin, which ultimately results in...

Osteoblast lysyl oxidase (LOX) is a strongly up-regulated mRNA and protein by the glucose-dependent insulinotropic polypeptide (GIP). LOX is critically required for collagen maturation, and was shown to be dramatically down-regulated in a mouse model of type 1 diabetes, consistent with known low collagen cross-linking and poor bone quality in diabe...

Diabetic retinopathy (DR) is characterized by apoptotic cell loss in the retinal vasculature. Lysyl oxidase propeptide (LOX-PP), released during LOX processing, has been implicated in promoting apoptosis in various diseased tissues. However, its role in the development and progression of DR is unknown. We investigated whether high glucose (HG) or d...

Diabetic bone disease is a complication of type I and type II diabetes, both of which are increasing in the United States and elsewhere. Increased hip and foot fracture rates do not correlate well with changes in bone mineral density, while studies support the importance of collagen structure to bone strength. Extracellular lysyl oxidase (LOX) cata...

Heterozygous missense mutations in lysyl oxidase (LOX) are associated with thoracic aortic aneurysms and dissections. To assess how LOX mutations modify protein function and lead to aortic disease, we studied the factors that influence the onset and progression of vascular aneurysms in mice bearing a Lox mutation (p.M292R) linked to aortic dilation...

Extracellular lysyl oxidases (LOX and LOXL1–LOXL4) are critical for collagen biosynthesis. LOXL2 is a marker of poor survival in oral squamous cell cancer. We investigated mechanisms by which tumor cell secreted LOXL2 targets proximal mesenchymal cells to enhance tumor growth and metastasis. This study identified the first molecular mechanism for L...

High Glucose Increases Binding of Lysyl Oxidase with Extracellular Matrix Proteins in Retinal Endothelial Cells: Implications for Diabetic Retinopathy

High Glucose Increases Binding of Lysyl Oxidase with Extracellular Matrix Proteins in Retinal Endothelial Cells: Implications for Diabetic Retinopathy

Introduction: The lysyl oxidase family consists of 5 members and oxidizes specific lysine residues in biosynthetic collagen and elastin maturation. Lysyl oxidase like-2 (LOXL2) is elevated in oral cancer and promotes metastasis and correlates with poor prognosis. The objective of this study is to determine the mechanism by which LOXL2 promotes the...

Gingival overgrowth is a side effect of certain medications, including calcium channel blockers, cyclosporin A, and phenytoin. Phenytoin-induced gingival overgrowth is fibrotic. Lysyl oxidases are extracellular enzymes that are required for biosynthetic cross-linking of collagens, and members of this enzyme family are upregulated in fibrosis. Previ...

The propeptide (LOX-PP) domain of the lysyl oxidase proenzyme (Pro-LOX) was shown to inhibit the transformed phenotype of breast, lung and pancreatic cells in culture and the formation of Her2/neu-driven breast cancer in a xenograft model. A single nucleotide polymorphism (SNP, rs1800449) positioned in a highly conserved region of LOX-PP results in...

For decades, dental schools in the United States have endured a significant faculty shortage. Studies have determined that the top 2 sources of dental faculty are advanced education programs and private practice. Those who have completed both DDS and PhD training are considered prime candidates for dental faculty positions. However, there is no nat...

The lysyl oxidase family of proteins is primarily known for its critical role in catalyzing extracellular oxidative deamination of hydroxylysine and lysine residues in collagens, and lysine residues in elastin required for connective tissue structure and function. Lysyl oxidases have additional important biological functions in health and disease....

A simple method for the determination of relative levels of insoluble collagen accumulation in fibroblast cultures is presented. Confluent cell cultures are provided with sodium ascorbate which is then permissive for collagen deposition. At intervals, cultures are fixed and stained successively with sirius red and then crystal Violet to, respective...

Purpose To investigate the effect of reducing high glucose (HG)-induced lysyl oxidase (LOX) overexpression and increased activity on retinal endothelial cell apoptosis. Methods Rat retinal endothelial cells (RRECs) were grown in normal (N) or HG (30 mM glucose) medium for 7 days. In parallel, RRECs were grown in HG medium and transfected with LOX...

The lysyl oxidase proenzyme propeptide region (LOX-PP) is a tumor suppressor protein whose mechanism of action is not completely understood. Here, the Ubiquitously eXpressed Transcript (UXT) was identified in a yeast two-hybrid assay with LOX-PP as bait and confirmed as a novel LOX-PP associating protein. UXT, a prefoldin-like protein, is ubiquitou...

Increasing interest in the multifunctional lysyl oxidase family of proteins is evident from the growth in the number of new publications each year. The enzymes have unique properties of strong affinities to extracellular matrix components, relative insolubility in typical buffers, low catalytic rates, and often low abundance. Here we provide detail...

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. T...

Lysyl oxidases are required for collagen and elastin cross-linking and extracellular matrix maturation including in bone. The lysyl oxidase family consists of lysyl oxidase (LOX) and 4 isoforms (LOXL1-4). Here we investigate whether deletion of LOXL1, which has been linked primarily to elastin maturation, leads to skeletal abnormalities. Left femur...

Lysyl oxidase (LOX) is overexpressed in various pathologies associated with thrombosis, such as arterial stenosis and myeloproliferative neoplasms (MPNs). LOX is elevated in the megakaryocytic lineage of mouse models of MPNs and in patients with MPNs. To gain insight into the role of LOX in thrombosis and platelet function without compounding the i...

Advances in the understanding of the biological roles of the lysyl oxidase family of enzyme proteins in bone structure and function are reviewed. This family of proteins is well-known as catalyzing the final reaction required for cross-linking of collagens and elastin. Novel emerging roles for these proteins in the phenotypic development of progeni...

Lysyl oxidase pro-enzyme is secreted by tumor cells and normal cells as a 50 kDa pro-enzyme into the extracellular environment where it is cleaved into the ~30 kDa mature enzyme (LOX) and 18 kDa pro-peptide (LOX-PP). Extracellular LOX enzyme activity is required for normal collagen and elastin extracellular cross-linking and maturation of the extra...

The lysyl oxidase propeptide (LOX-PP) is derived from pro-lysyl oxidase (Pro-LOX) by extracellular biosynthetic proteolysis. LOX-PP inhibits breast and prostate cancer xenograft tumor growth and has tumor suppressor activity. Although, several intracellular targets and molecular mechanisms of action of LOX-PP have been identified, LOX-PP uptake pat...

Bone formation and healing are diminished in experimental type 1 diabetes. The present study investigated whether controlled local release of recombinant human bone morphogenetic protein 2 (rhBMP-2) stimulates bone defect healing in diabetes as a consequence of its anabolic effects on bone. Bilateral experimental circular bone defects were created...

Drug-induced gingival overgrowth is caused by the antiseizure medication phenytoin, calcium channel blockers, and cyclosporin. Characteristics of these drug-induced gingival overgrowth lesions differ. We evaluate the ability of a mouse model to mimic human phenytoin-induced gingival overgrowth and assess the ability of a drug to prevent its develop...

Lysyl oxidases are enzymes which catalyze the final enzymatic modification of ε‐ amino groups of lysine residues of elastin, and lysine and hydroxylysine residues of collagens, to form peptidyl‐aldehydes required for biosynthetic cross‐linking and extracellular matrix maturation and function. This family includes lysyl oxidase (LOX) and lysyl oxida...

Introduction Lysyl oxidase (LOX) catalyzes the oxidation of lysines to aldehydes, providing stability in connective tissues through spontaneous cross‐linking of collagen and elastin. LOX expression is elevated in sera of patients with myeloproliferative neoplasms (MPN), a group of disorders that have in common the proliferation of megakaryocytes an...

The type III TGF-β receptor has potential therapeutic and prognostic potential in breast cancer.

Drug-induced gingival overgrowth is a tissue-specific condition and is estimated to affect approximately one million North Americans. Lesions occur principally as side-effects from phenytoin, nifedipine, or ciclosporin therapy in approximately half of the people who take these agents. Due to new indications for these drugs, their use continues to g...

Diabetes diminishes bone healing and ossification. Reduced bone formation in intramembranous ossification is known, yet the mechanism(s) behind impaired intramembranous bone healing are unclear. Here we report the formation of a fibrotic matrix during healing of intramembranous calvarial bone defects that appears to exclude new bone growth. Our his...

Lysyl oxidase is a multifunctional enzyme required for collagen biosynthesis. Various growth factors regulate lysyl oxidase during osteoblast differentiation, subject to modulation by cytokines such as TNF-α in inflammatory osteopenic disorders including diabetic bone disease. Canonical Wnt signaling promotes osteoblast development. Here we investi...

Lysyl oxidase (LOX) is a multifunctional protein required for normal collagen and elastin biosynthesis and maturation. In addition, LOX has complex roles in cancer in which the lysyl oxidase propeptide (LOX-PP) domain of secreted pro-LOX has tumor-suppressor activity, while the active enzyme promotes metastasis. In prostate cancer cell lines, recom...

In this report, chairs of the 7th International Workshop on the CCN family of Genes, review the progress made in understanding the biological functions of CCN proteins (CCN1, CCN2, CCN3, CCN4, CCN5 and CCN6) with a particular focus on their implications in various pathological conditions, including cancer, fibrosis, diabetes, and cardiovascular dis...

The lysyl oxidase gene inhibits Ras signaling in transformed fibroblasts and breast cancer cells. Its activity was mapped to the 162 amino acid propeptide domain (LOX-PP) of the lysyl oxidase precursor protein. LOX-PP inhibited the Her-2/Ras signaling axis in breast cancer cells, and reduced the Her-2-driven breast tumor burden in a xenograft model...

Diabetes increases the risk of bone fracture. Organic and inorganic bone extracellular matrix components determine bone strength. Previous studies indicate that in diabetes, glycation of collagen causes abnormal arrangements of collagen molecules and fragile bones. Diabetic bone fragility is additionally attributed to reduced levels of lysyl oxidas...

Connective Tissue Growth Factor (CCN2/CTGF) mediates TGFβ induced fibrosis. Drug-induced gingival overgrowth is tissue specific. Here the role of the phosphoinositol 3 kinase (PI3K) pathway in mediating TGFβ1 stimulated CCN2/CTGF expression in primary human adult gingival fibroblasts and human adult lung fibroblasts was compared. Data indicate that...

Hypoxia-inducible factor 1 (HIF-1) is the key transcription factor involved in the adaptation of mammals to hypoxia and plays a crucial role in cancer angiogenesis. Recent evidence suggests a leading role for HIF-1 in various inflammatory and infectious diseases. Here we describe the role of HIF-1 in Staphylococcus aureus infections by investigatin...

Objective: Lysyl oxidase (LOX) dependent cross-linking is deficient in diabetic bone. Here we investigate regulation of LOX by Wnt3a and TNF-α in a mesenchymal stem cell line as a model for a mechanism of diabetic osteopenia. Method: C3H10T1/2 cells were treated with Wnt3a +/- TNF-α. LOX expression (qPCR), promoter/reporter activity, and mRNA...

Megakaryocytes (MKs), the platelet precursors, undergo an endomitotic cell cycle that leads to polyploidy. Lysyl oxidase propeptide (LOX-PP) is generated from lysyl oxidase (LOX) pro-enzyme after proteolytical cleavage. We recently reported that LOX, a known matrix cross-linking enzyme, contributes to MK lineage expansion. In addition, LOX expressi...

Objective: Establish a novel phenytoin-induced gingival overgrowth (PIGO) mouse model by continuous administration of phenytoin to mice. Evaluate gingival changes macroscopically and microscopically in the context of epithelial to mesenchymal transition (EMT). Method: 8-Week old BALB/cByJ mice were recruited and devided into a control group r...

Objective: Phenytoin- and nifedipine-induced human gingival overgrowth tissues contain high levels of CCN2 (connective tissue growth factor). Recombinant CCN2 protein (rCCN2) stimulates collagen accumulation in gingival fibroblast cultures via integrin alpha6 beta1. These effects are inhibited by a small synthetic CCN2 peptide (M3P). Here the mecha...

B lymphocyte-induced maturation protein 1 (Blimp1) is a master regulator of B cell differentiation, and controls migration of primordial germ cells. Recently we observed aberrant Blimp1 expression in breast cancer cells resulting from an NF-κB RelB to Ras signaling pathway. In order to address the question of whether the unexpected expression of Bl...

Lysyl oxidase propeptide (LOX-PP) ectopic overexpression inhibits the growth of cancer xenografts. Here the ability and mode of action of purified recombinant LOX-PP (rLOX-PP) protein to inhibit the growth of pre-existing xenografts was determined. Experimental approaches employed were direct intratumoral injection (i.t.) of rLOX-PP protein into mu...

Gingival overgrowth tissues have thickened connective tissue stroma, sometimes accompanied by the increased presence of collagen fibers, thickened epithelia, and elongated rete pegs. We have previously shown that expression of CCN2, also known as connective tissue growth factor (CTGF), correlates positively with the degree of gingival fibrosis, and...

The lysyl oxidase gene (LOX) inhibits Ras signaling in transformed fibroblasts and breast cancer cells. Its activity was mapped to the 162-amino-acid propeptide domain (LOX-PP) of the lysyl oxidase precursor protein. LOX-PP inhibits Erk signaling, motility, and tumor formation in a breast cancer xenograft model; however, its mechanism of action is...

The propeptide region of the lysyl oxidase proenzyme (LOX-PP) has been shown to inhibit Ras signaling in NIH 3T3 and lung cancer cells with activated RAS, but its mechanism of action is poorly understood. Here, a yeast two-hybrid assay of LOX-PP-interacting proteins identified a clone encoding the intracellular phosphatase domains of receptor-type...

Lysyl oxidase (LOX), a matrix cross-linking protein, is known to be selectively expressed and to enhance a fibrotic phenotype. A recent study of ours showed that LOX oxidizes the PDGF receptor-β (PDGFR-β), leading to amplified downstream signaling. Here, we examined the expression and functions of LOX in megakaryocytes (MKs), the platelet precursor...

Macrophage- and vascular-derived matrix metalloproteinase (MMP)-9 plays an important role in neointima formation after vascular injury. The A2b adenosine receptor (A2bAR) elevates cyclic adenosine monophosphate and suppresses tumor necrosis factor-α (TNF-α) levels at baseline and after vascular injury. Considering the influences of TNF-α on MMP-9 e...

The lysyl oxidase family is made up of five members: lysyl oxidase (LOX) and lysyl oxidase-like 1–4 (LOXL1-LOXL4). All members share conserved C-terminal catalytic domains that provide for lysyl oxidase or lysyl oxidase-like enzyme activity; and more divergent propeptide regions. LOX family enzyme activities catalyze the final enzymatic conversion...

Lysyl oxidase (LOX) is secreted as a proenzyme (proLOX) that is proteolytically processed in the extracellular milieu to release the propeptide and mature, active LOX. LOX oxidizes lysyl residues of a number of protein substrates in the extracellular matrix and on the cell surface, which impacts several physiological and disease states. Although th...

RAS mutations or its activation by upstream receptor tyrosine kinases are frequently associated with poor response of carcinomas to chemotherapy. The 18 kDa propeptide domain of lysyl oxidase (LOX-PP) released from the secreted precursor protein (Pro-LOX) has been shown to inhibit RAS signaling and the transformed phenotype of breast, pancreatic, l...

In diabetes, retinal vascular basement membrane (BM) undergoes significant thickening and compromises vessel function including increased vascular permeability, a prominent lesion of early diabetic retinopathy. In this study we determined whether altered expression and activity of lysyl oxidase (LOX), a cross-linking enzyme, may compromise vascular...

The lysyl oxidase family is made up of five members: lysyl oxidase (LOX) and lysyl oxidase-like 1-4 (LOXL1-LOXL4). All members share conserved C-terminal catalytic domains that provide for lysyl oxidase or lysyl oxidase-like enzyme activity; and more divergent propeptide regions. LOX family enzyme activities catalyze the final enzymatic conversion...

Epithelial to mesenchymal transition (EMT) occurs normally in development. In pathology, EMT drives cancer and fibrosis. Medication with phenytoin, nifedipine, and cyclosporine-A often causes gingival overgrowth. Based partly on the histopathology of gingival overgrowth, the present study investigates the hypothesis that EMT could contribute to its...

BACKGROUND: The histopathology of human gingival overgrowth tissue samples has led us to investigate whether epithelial to mesenchymal transition (EMT) could contribute to these lesions. AIM: Determine whether cultured human gingival epithelial cells can undergo transition to a more mesenchymal phenotype in vitro. METHODS: Primary gingival epitheli...

Introduction: TGFb stimulates CCN2/CTGF expression in human fibroblastic cells. CCN2/CTGF is responsible for some of the effects of TGFb and contributes to fibrosis in tissues including phenytoin-induced human gingival overgrowth. Objective: Explore possible tissue specific signaling pathways including PI3'K, PKC and GSK3b in CCN2/CTGF regulation b...

Introduction: Lysyl oxidase is secreted as a 50 kDa pro-enzyme and is then cleaved to a 30 kDa mature enzyme (LOX) and an 18 kDa propeptide (LOX-PP). Preliminary data indicate that LOX-PP inhibits proliferation of osteoblasts and delays terminal mineralization. FGF-2 is a key mitogen for osteoblasts that expands the pool of cells during early stage...

Pro-lysyl oxidase is secreted as a 50-kDa proenzyme and is then cleaved to a 30-kDa mature enzyme (lysyl oxidase (LOX)) and an 18-kDa propeptide (lysyl oxidase propeptide (LOX-PP)). The presence of LOX-PP in the cell layers of phenotypically normal osteoblast cultures led us to investigate the effects of LOX-PP on osteoblast differentiation. Data i...

Lysyl oxidase enzyme activity is critical for the biosynthesis of mature and functional collagens and elastin. In addition, lysyl oxidase has tumor suppressor activity that has been shown to depend on the propeptide region (LOX-PP) derived from pro-lysyl oxidase (Pro-LOX) and not on lysyl oxidase enzyme activity. Pro-LOX is secreted as a 50 kDa pro...

The lysyl oxidase (LOX) gene reverted Ras transformation of NIH 3T3 fibroblasts and tumor formation by gastric cancer cells, which frequently carry mutant RAS genes. The secreted lysyl oxidase proenzyme is processed to a propeptide (LOX-PP) and a functional enzyme (LOX). Unexpectedly, the tumor suppressor activity mapped to the LOX-PP domain, which...

Enhanced RAS signaling and decreased androgen dependence of prostate cancer cells accompany poor clinical outcomes. Elevated autocrine fibroblast growth factors 2 (FGF-2) signaling promotes prostate cancer cell growth and survival. Expression of lysyl oxidase (LOX) inhibits RAS transforming activity. LOX is secreted as 50 kDa pro-LOX protein and th...

Lysyl oxidase (LOX) catalyzes cross-linking of elastin and collagen, which is essential for the structural integrity and function of bone tissue. The present study examined the role of Lox gene deficiency for the osteoblast phenotype in primary calvarial osteoblasts from E18.5 Lox knockout (Lox ( -/- )) and wild type (wt) (C57BL/6) mice. Next to Lo...

BACKGROUND: The αvβ6 integrin receptor binds fibronectin, activates latent TGF-β and is expressed at elevated levels during Epithelial to Mesenchymal Transition (EMT) in carcinoma. We are investigating the hypothesis that EMT mediated by αvβ6 contributes to phenytoin (PHE), nifedipine (NIF), and cyclosporine A(CsA)-induced gingival fibrosis in huma...