Mucopolysaccharidosis IVA and glycosaminoglycans

Mucopolysaccharidosis IVA (MPS IVA; Morquio A: OMIM 253000) is a lysosomal storage disease with an autosomal recessive trait caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase. Deficiency of this enzyme leads to accumulation of specific glycosaminoglycans (GAGs): chondroitin-6-sulfate (C6S) and keratan sulfate (KS). C6S and KS are mainly produced in the cartilage. Therefore, the undegraded substrates are stored primarily in cartilage and in its extracellular matrix (ECM), leading to a direct impact on cartilage and bone development, and successive systemic skeletal dysplasia. Chondrogenesis, the earliest phase of skeletal formation, is maintained by cellular interactions with the ECM, growth and differentiation factors, signaling pathways, and transcription factors in a temporal-spatial manner. In patients with MPS IVA, the cartilage is disrupted at birth as a consequence of abnormal chondrogenesis and/or endochondral ossification. The unique skeletal features are distinguished by a disproportional short stature, odontoid hypoplasia, spinal cord compression, tracheal obstruction, pectus carinatum, kyphoscoliosis, platyspondyly, coxa valga, genu valgum, waddling gait, and laxity of joints. In spite of many descriptions of these unique clinical features, delay of diagnosis still happens. The pathogenesis and treatment of systemic skeletal dysplasia in MPS IVA remains an unmet challenge. In this review article, we comprehensively describe historical aspect, property of GAGs, diagnosis, screening, pathogenesis, and current and future therapies of MPS IVA.

Stability of furosemide and chlorothiazide stored in syringes

PURPOSE

The results of a study to determine the stability of solutions of furosemide and chlorothiazide over 96 hours are reported.

METHODS

Chlorothiazide and furosemide were diluted in 5% dextrose USP to final concentrations of 10 and 1 mg/mL, respectively, and combined. In addition, sample solutions of chlorothiazide in dextrose, furosemide in dextrose, and dextrose alone were prepared for control purposes. The resulting solutions were analyzed immediately after preparation and 24, 48, 72, and 96 hours later using a liquid chromatography-tandem mass spectroscopy (LC-MS/MS) system with an electrospray ionization source. Mixtures and samples were diluted 10,000-fold prior to LC-MS/MS analysis so that concentrations of both drugs would be within the assay's linear range of detection.

RESULTS

LC-MS/MS analysis showed that chlorothiazide typically eluted at 2.6 minutes and furosemide at 4.8 minutes. Each compound was degraded by exposure to strong ultraviolet light in a time-dependent manner. Both unmixed and mixed solutions retained over 90% of the original concentrations of chlorothiazide and furosemide for up to 96 hours. Furosemide and chlorothiazide are commonly used concomitantly to maximize diuresis in pediatric patients; the study findings suggest that solutions of furosemide and chlorothiazide can be combined in the same syringe without loss of stability for up to 96 hours.

CONCLUSION

Solutions of chlorothiazide (10 mg/mL) and furosemide (1 mg/mL) stored either separately or together in polypropylene syringes remained stable for up to 96 hours at room temperature and protected from light.

Current therapies for Morquio A syndrome and their clinical outcomes

INTRODUCTION

Morquio A syndrome is characterized by a unique skeletal dysplasia, leading to short neck and trunk, pectus carinatum, laxity of joints, kyphoscoliosis, and tracheal obstruction. Cervical spinal cord compression/inability, a restrictive and obstructive airway, and/or bone deformity and imbalance of growth, are life-threatening to Morquio A patients, leading to a high morbidity and mortality. It is critical to review the current therapeutic approaches with respect to their efficacy and limitations.

AREAS COVERED

Patients with progressive skeletal dysplasia often need to undergo orthopedic surgical interventions in the first two decades of life. Recently, we have treated four patients with a new surgery to correct progressive tracheal obstruction. Enzyme replacement therapy (ERT) has been approved clinically. Cell-based therapies such as hematopoietic stem cell therapy (HSCT) and gene therapy are typically one-time, permanent treatments for enzyme deficiencies. We report here on four Morquio A patients treated with HSCT approved in Japan and followed for at least ten years after treatment. Gene therapy is under investigation on mouse models but not yet available as a therapeutic option.

EXPERT OPINION

ERT and HSCT in combination with surgical intervention(s) are a therapeutic option for Morquio A; however, the approach for bone and cartilage lesion remains an unmet challenge.

Generation of Pediatric Leukemia Xenograft Models in NSG-B2m Mice: Comparison with NOD/SCID Mice

Generation of orthotopic xenograft mouse models of leukemia is important to understand the mechanisms of leukemogenesis, cancer progression, its cross talk with the bone marrow microenvironment, and for preclinical evaluation of drugs. In these models, following intravenous injection, leukemic cells home to the bone marrow and proliferate there before infiltrating other organs, such as spleen, liver, and the central nervous system. Moreover, such models have been shown to accurately recapitulate the human disease and correlate with patient response to therapy and prognosis. Thus, various immune-deficient mice strains have been used with or without recipient preconditioning to increase engraftment efficiency. Mice homozygous for the severe combined immune deficiency (SCID) mutation and with non-obese diabetic background (NOD/SCID) have been used in the majority of leukemia xenograft studies. Later, NOD/SCID mice deficient for interleukin 2 receptor gamma chain (IL2Rγ) gene called NSG mice became the model of choice for leukemia xenografts. However, engraftment of leukemia cells without irradiation preconditioning still remained a challenge. In this study, we used NSG mice with null alleles for major histocompatibility complex class I beta2-microglobulin (β2m) called NSG-B2m. This is a first report describing the 100% engraftment efficiency of pediatric leukemia cell lines and primary samples in NSG-B2m mice in the absence of host preconditioning by sublethal irradiation. We also show direct comparison of the engraftment efficiency and growth rate of pediatric acute leukemia cells in NSG-B2m and NOD/SCID mice, which showed 80–90% engraftment efficiency. Secondary and tertiary xenografts in NSG-B2m mice generated by injection of cells isolated from the spleens of leukemia-bearing mice also behaved similar to the primary patient sample. We have successfully engrafted 25 acute lymphoblastic leukemia (ALL) and 5 acute myeloid leukemia (AML) patient samples with distinct cytogenetic characteristics in NSG-B2m mice, with the purpose of generating pediatric ALL and AML xenografts for preclinical evaluation of drugs. Thus, our data support the use of NSG-B2m mouse model for leukemia engraftment and in vivo preclinical drug efficacy studies.

Activity of daily living for Morquio A syndrome

The aim of this study was to evaluate the activity of daily living (ADL) and surgical interventions in patients with mucopolysaccharidosis IVA (MPS IVA). The factor(s) that affect ADL are age, clinical phenotypes, surgical interventions, therapeutic effect, and body mass index. The ADL questionnaire comprises three domains: "Movement," "Movement with cognition," and "Cognition." Each domain has four subcategories rated on a 5-point scale based on the level of assistance. The questionnaire was collected from 145 healthy controls and 82 patients with MPS IVA. The patient cohort consisted of 63 severe and 17 attenuated phenotypes (2 were undefined); 4 patients treated with hematopoietic stem cell transplantation (HSCT), 33 patients treated with enzyme replacement therapy (ERT) for more than a year, and 45 untreated patients. MPS IVA patients show a decline in ADL scores after 10years of age. Patients with a severe phenotype have a lower ADL score than healthy control subjects, and lower scores than patients with an attenuated phenotype in domains of "Movement" and "Movement with cognition." Patients, who underwent HSCT and were followed up for over 10years, had higher ADL scores and fewer surgical interventions than untreated patients. ADL scores for ERT patients (2.5years follow-up on average) were similar with the-age-matched controls below 10years of age, but declined in older patients. Surgical frequency was higher for severe phenotypic patients than attenuated ones. Surgical frequency for patients treated with ERT was not decreased compared to untreated patients. In conclusion, we have shown the utility of the proposed ADL questionnaire and frequency of surgical interventions in patients with MPS IVA to evaluate the clinical severity and therapeutic efficacy compared with age-matched controls.

Cathepsin Inhibition Prevents Autophagic Protein Turnover and Downregulates Insulin Growth Factor-1 Receptor-Mediated Signaling in Neuroblastoma

Inhibition of the major lysosomal proteases, cathepsins B, D, and L, impairs growth of several cell types but leads to apoptosis in neuroblastoma. The goal of this study was to examine the mechanisms by which enzyme inhibition could cause cell death. Cathepsin inhibition caused cellular accumulation of fragments of the insulin growth factor 1 (IGF-1) receptor. The fragments were located in dense organelles that were characterized as autophagosomes. This novel discovery provides the first clear link between lysosomal function, autophagy, and IGF-1- mediated cell proliferation. A more in-depth analysis of the IGF1 signaling pathway revealed that the mitogen-activated protein kinase (MAPK) cell-proliferation pathway was impaired in inhibitor treated cells, whereas the Akt cell survival pathway remained functional. Shc, an adapter protein that transmits IGF-1 signaling through the MAPK pathway, was sequestered in autophagosomes; whereas IRS-2, an adapter protein that transmits IGF-1 signaling through the Akt pathway, was unaffected by cathepsin inhibition. Furthermore, Shc was sequestered in autophagosomes as its active form, indicating that autophagy is a key mechanism for downregulating IGF-1-induced cell proliferation. Cathepsin inhibition had a greater effect on autophagic sequestration of the neuronal specific adapter protein, Shc-C, than ubiquitously expressed Shc-A, providing mechanistic support for the enhanced sensitivity of neuronally derived tumor cells. We also observed impaired activation of MAPK by epidermal growth factor treatment in inhibitor-treated cells. The Shc adapter proteins are central to transducing proliferation signaling by a range of receptor tyrosine kinases; consequently, cathepsin inhibition may become an important therapeutic approach for treating neuroblastoma and other tumors of neuronal origin.

Enzyme replacement therapy for treating mucopolysaccharidosis type IVA (Morquio A syndrome): effect and limitations

INTRODUCTION

Following a Phase III, randomized, double-blind, placebo (PBO)-controlled, multinational study in subjects with mucopolysaccharidosis IVA (MPS IVA), enzyme replacement therapy (ERT) of elosulfase alfa has been approved in several countries. The study was designed to evaluate safety and efficacy of elosulfase alfa in patients with MPS IVA aged 5 years and older.

AREAS COVERED

Outcomes of clinical trials for MPS IVA have been described. Subjects received either 2.0 mg/kg/week, 2.0 mg/kg/every other week, or PBO, for 24 weeks. The primary endpoint was the change from baseline 6-min walk test (6MWT) distance compared to PBO. The 6MWT results improved in patients receiving 2 mg/kg weekly compared to PBO. The every other week regimen resulted in walk distances comparable to PBO. There was no change from baseline in the 3 Min Stair Climb Test in both treatment groups. Following completion of the initial study, patients, who continued to receive elosulfase alfa 2 mg/kg weekly (QW) for another 48 weeks (for a total of up to 72-week exposure), did not show additional improvement on 6MWT.

EXPERT OPINION

We suggest that ERT is a therapeutic option for MPS IVA, providing a modest effect and the majority of the effects are seen in the soft tissues.

Carcinoma cells induce lumen filling and EMT in epithelial cells through soluble E-cadherin-mediated activation of EGFR

In epithelial cancers, carcinoma cells coexist with normal cells. Although it is known that the tumor microenvironment (TME) plays a pivotal role in cancer progression, it is not completely understood how the tumor influences adjacent normal epithelial cells. In this study, a three-dimensional co-culture system comprising non-transformed epithelial cells (MDCK) and transformed carcinoma cells (MSV-MDCK) was used to demonstrate that carcinoma cells sequentially induce preneoplastic lumen filling and epithelial-mesenchymal transition (EMT) in epithelial cysts. MMP-9 secreted by carcinoma cells cleaves cellular E-cadherin (encoded by CDH1) from epithelial cells to generate soluble E-cadherin (sE-cad), a pro-oncogenic protein. We show that sE-cad induces EGFR activation, resulting in lumen filling in MDCK cysts. Long-term sE-cad treatment induced EMT. sE-cad caused lumen filling by induction of the ERK signaling pathway and triggered EMT through the sustained activation of the AKT pathway. Although it is known that sE-cad induces MMP-9 release and consequent EGFR activation in tumor cells, our results, for the first time, demonstrate that carcinoma cells can induce sE-cad shedding in adjacent epithelial cells, which leads to EGFR activation and the eventual transdifferentiation of the normal epithelial cells.

Disruption of Annexin II /p11 Interaction Suppresses Leukemia Cell Binding, Homing and Engraftment, and Sensitizes the Leukemia Cells to Chemotherapy

The bone marrow microenvironment plays an important role in acute lymphoblastic leukemia (ALL) cell proliferation, maintenance, and resistance to chemotherapy. Annexin II (ANX2) is abundantly expressed on bone marrow cells and complexes with p11 to form ANX2/p11-hetero-tetramer (ANX2T). We present evidence that p11 is upregulated in refractory ALL cell lines and patient samples. A small molecule inhibitor that disrupts ANX2/p11 interaction (ANX2T inhibitor), an anti-ANX2 antibody, and knockdown of p11, abrogated ALL cell adhesion to osteoblasts, indicating that ANX2/p11 interaction facilitates binding and retention of ALL cells in the bone marrow. Furthermore, ANX2T inhibitor increased the sensitivity of primary ALL cells co-cultured with osteoblasts to dexamethasone and vincristine induced cell death. Finally, in an orthotopic leukemia xenograft mouse model, the number of ALL cells homing to the bone marrow was reduced by 40-50% in mice injected with anti-ANX2 antibody, anti-p11 antibody or ANX2T inhibitor compared to respective controls. In a long-term engraftment assay, the percentage of ALL cells in mouse blood, bone marrow and spleen was reduced in mice treated with agents that disrupt ANX2/p11 interaction. These data show that disruption of ANX2/p11 interaction results in reduced ALL cell adhesion to osteoblasts, increased ALL cell sensitization to chemotherapy, and suppression of ALL cell homing and engraftment.

Abstract LB-032: Soluble E-cadherin as a microenvironmental factor that enhances tumor progression

During malignant transformation of epithelial cells, their well-organized architecture is disrupted. A key event observed during epithelial cancer progression is down regulation of E-cadherin (E-cad), a central adherens junction protein that plays a crucial role in directing cell polarity, epithelial architecture and cell-cell adhesion. One mechanism by which tumor cells downregulate E-cad is by the proteolytic cleavage of its extracellular domain by proteases such as the matrix metalloproteinases (MMPs). This proteolytic cleavage results in the shedding of the E-cad ectodomain as an 80 kDa fragment known as soluble E-cadherin (sE-cad). Elevated levels of sE-cad are found in the serum and urine of cancer patients. In tumor cells physiological consequences include enhanced tumor cell migration and invasion, induction of MMP secretion, and increased cell signaling; all of which ultimately result in tumor progression. sE-cad also causes morphological changes in epithelial cells, including disruption of the adherens junction. However, the influence of elevated sE-cad levels on normal tissue architecture is not well understood. Specifically, the mechanism by which sE-cad in the tumor microenvironment interacts with cellular E-cad in normal epithelium is yet to be elucidated.

We used a three-dimensional (3D) cell-culture system to determine the effects of sE-cad on normal epithelial cyst morphology. In this study, we show that recombinant, purified sE-cad can induce lumen-filling in normal non-tumorigenic Madin-Darby canine kidney (MDCK) epithelial cysts. The acinar luminal filling and multiple lumen formation induced by purified sE-cad represent changes in epithelial tissue structure that are characteristic of premalignant lesions reported in human epithelial glandular tumors. We further demonstrate that co-culturing of tumor cells with epithelial MDCK cysts results in disruption of 3D epithelial architecture and filling up of the hollow lumen. Our results also show that tumor cell-induced lumen filling is trigged by sE-cad shedding, with a concomitant increase in MMP-9. Using an inhibitor of MMP-9, we provide evidence that MMP-9 is crucial for lumen filling. Together, these novel findings indicate that invasive carcinoma cells can induce structural alterations in adjacent normal epithelium, and that elevated sE-cad levels disrupt epithelial architecture and activate signaling pathways in normal epithelial cells.

Citation Format: Pratima Patil, Robert W. Mason, Julia D' Ambrosio, Ayyappan K. Rajasekaran. Soluble E-cadherin as a microenvironmental factor that enhances tumor progression. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-032. doi:10.1158/1538-7445.AM2015-LB-032

CD19-Targeted Nanodelivery of Doxorubicin Enhances Therapeutic Efficacy in B-Cell Acute Lymphoblastic Leukemia

Nanomedicine has advanced to clinical trials for adult cancer therapy. However, the field is still in its infancy for treatment of childhood malignancies such as acute lymphoblastic leukemia (ALL). Nanotherapy offers multiple advantages over conventional therapy. It facilitates targeted delivery and enables controlled release of drugs to reduce treatment-related side effects. Here, we demonstrate that doxorubicin (DOX) encapsulated in polymeric nanoparticles (NPs) modified with targeting ligands against CD19 (CD19-DOX-NPs) can be delivered in a CD19-specific manner to leukemic cells. The CD19-DOX-NPs were internalized via receptor-mediated endocytosis and imparted cytotoxicity in a CD19-dependent manner in CD19-positive ALL cells. Leukemic mice treated with CD19-DOX-NPs survived significantly longer and manifested a higher degree of agility, indicating reduced apparent systemic toxicity during treatment compared to mice treated with free DOX. We suggest that targeted delivery of drugs used in childhood cancer treatment should improve therapeutic efficacy and reduce treatment-related side effects in children.

Impact of enzyme replacement therapy and hematopoietic stem cell transplantation in patients with Morquio A syndrome

Patients with mucopolysaccharidosis IVA (MPS IVA) can present with systemic skeletal dysplasia, leading to a need for multiple orthopedic surgical procedures, and often become wheelchair bound in their teenage years. Studies on patients with MPS IVA treated by enzyme replacement therapy (ERT) showed a sharp reduction on urinary keratan sulfate, but only modest improvement based on a 6-minute walk test and no significant improvement on a 3-minute climb-up test and lung function test compared with the placebo group, at least in the short-term. Surgical remnants from ERT-treated patients did not show reduction of storage materials in chondrocytes. The impact of ERT on bone lesions in patients with MPS IVA remains limited. ERT seems to be enhanced in a mouse model of MPS IVA by a novel form of the enzyme tagged with a bone-targeting moiety. The tagged enzyme remained in the circulation much longer than untagged native enzyme and was delivered to and retained in bone. Three-month-old MPS IVA mice treated with 23 weekly infusions of tagged enzyme showed marked clearance of the storage materials in bone, bone marrow, and heart valves. When treatment was initiated at birth, reduction of storage materials in tissues was even greater. These findings indicate that specific targeting of the enzyme to bone at an early stage may improve efficacy of ERT for MPS IVA. Recombinant N-acetylgalactosamine-6-sulfate sulfatase (GALNS) in Escherichia coli BL21 (DE3) (erGALNS) and in the methylotrophic yeast Pichia pastoris (prGALNS) has been produced as an alternative to the conventional production in Chinese hamster ovary cells. Recombinant GALNS produced in microorganisms may help to reduce the high cost of ERT and the introduction of modifications to enhance targeting. Although only a limited number of patients with MPS IVA have been treated with hematopoietic stem cell transplantation (HSCT), beneficial effects have been reported. A wheelchair-bound patient with a severe form of MPS IVA was treated with HSCT at 15 years of age and followed up for 10 years. Radiographs showed that the figures of major and minor trochanter appeared. Loud snoring and apnea disappeared. In all, 1 year after bone marrow transplantation, bone mineral density at L2-L4 was increased from 0.372 g/cm(2) to 0.548 g/cm(2) and was maintained at a level of 0.48±0.054 for the following 9 years. Pulmonary vital capacity increased approximately 20% from a baseline of 1.08 L to around 1.31 L over the first 2 years and was maintained thereafter. Activity of daily living was improved similar to the normal control group. After bilateral osteotomies, a patient can walk over 400 m using hip-knee-ankle-foot orthoses. This long-term observation of a patient shows that this treatment can produce clinical improvements although bone deformity remained unchanged. In conclusion, ERT is a therapeutic option for MPS IVA patients, and there are some indications that HSCT may be an alternative to treat this disease. However, as neither seems to be a curative therapy, at least for the skeletal dysplasia in MPS IVA patients, new approaches are investigated to enhance efficacy and reduce costs to benefit MPS IVA patients.

Activities of daily living in patients with Hunter syndrome: impact of enzyme replacement therapy and hematopoietic stem cell transplantation

The aim of this study was to assess the activities of daily living (ADL) in patients with Hunter syndrome (mucopolysaccharidosis II; MPS II) using a newly designed ADL questionnaire. We applied the questionnaire to evaluate clinical phenotypes and therapeutic efficacies of enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT). We also explored early signs and symptoms to make early diagnosis feasible. We devised a new ADL questionnaire with three domains: "movement," "movement with cognition," and "cognition." Each domain has four subcategories rated on a 5-point scale based on level of assistance. We also scored signs and symptoms unique to MPS by 12 subcategories (five points per category), providing 60 points in total. The questionnaire was first administered to 138 healthy Japanese controls (0.33-50 years), and successively, to 74 Japanese patients with Hunter syndrome (4-49 years). The patient cohort consisted of 51 severe and 23 attenuated phenotypes; 20 patients treated with HSCT, 23 patients treated early with ERT (≤8 years), 25 patients treated late with ERT (>8 years), and 4 untreated patients. Among 18 severe phenotypic patients treated by HSCT, 10 were designated as early HSCT (≤5years), while 8 were designated as late HSCT (>5years). Scores from patients with severe phenotypes were lower than controls and attenuated phenotypes in all categories. Among patients with severe phenotypes, there was a trend that HSCT provides a higher ADL score than early ERT, and there was a significant difference in ADL scores between late ERT and HSCT groups. Early ERT and early HSCT provided a higher score than late ERT and late HSCT, respectively. In conclusion, we have evaluated the feasibility of a new questionnaire in control population and patients with Hunter syndrome, leading to a novel evaluation method for clinical phenotypes and therapeutic efficacy. Early treatment with HSCT provides a better consequence in ADL of patients.

Therapies for the bone in mucopolysaccharidoses

Patients with mucopolysaccharidoses (MPS) have accumulation of glycosaminoglycans in multiple tissues which may cause coarse facial features, mental retardation, recurrent ear and nose infections, inguinal and umbilical hernias, hepatosplenomegaly, and skeletal deformities. Clinical features related to bone lesions may include marked short stature, cervical stenosis, pectus carinatum, small lungs, joint rigidity (but laxity for MPS IV), kyphoscoliosis, lumbar gibbus, and genu valgum. Patients with MPS are often wheelchair-bound and physical handicaps increase with age as a result of progressive skeletal dysplasia, abnormal joint mobility, and osteoarthritis, leading to 1) stenosis of the upper cervical region, 2) restrictive small lung, 3) hip dysplasia, 4) restriction of joint movement, and 5) surgical complications. Patients often need multiple orthopedic procedures including cervical decompression and fusion, carpal tunnel release, hip reconstruction and replacement, and femoral or tibial osteotomy through their lifetime. Current measures to intervene in bone disease progression are not perfect and palliative, and improved therapies are urgently required. Enzyme replacement therapy (ERT), hematopoietic stem cell transplantation (HSCT), and gene therapy are available or in development for some types of MPS. Delivery of sufficient enzyme to bone, especially avascular cartilage, to prevent or ameliorate the devastating skeletal dysplasias remains an unmet challenge. The use of an anti-inflammatory drug is also under clinical study. Therapies should start at a very early stage prior to irreversible bone lesion, and damage since the severity of skeletal dysplasia is associated with level of activity during daily life. This review illustrates a current overview of therapies and their impact for bone lesions in MPS including ERT, HSCT, gene therapy, and anti-inflammatory drugs.

Novel heparan sulfate assay by using automated high-throughput mass spectrometry: Application to monitoring and screening for mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are caused by deficiency of one of a group of specific lysosomal enzymes, resulting in excessive accumulation of glycosaminoglycans (GAGs). We previously developed GAG assay methods using liquid chromatography tandem mass spectrometry (LC-MS/MS); however, it takes 4-5 min per sample for analysis. For the large numbers of samples in a screening program, a more rapid process is desirable. The automated high-throughput mass spectrometry (HT-MS/MS) system (RapidFire) integrates a solid phase extraction robot to concentrate and desalt samples prior to direction into the MS/MS without chromatographic separation; thereby allowing each sample to be processed within 10s (enabling screening of more than one million samples per year). The aim of this study was to develop a higher throughput system to assay heparan sulfate (HS) using HT-MS/MS, and to compare its reproducibility, sensitivity and specificity with conventional LC-MS/MS. HS levels were measured in the blood (plasma and serum) from control subjects and patients with MPS II, III, or IV and in dried blood spots (DBS) from newborn controls and patients with MPS I, II, or III. Results obtained from HT-MS/MS showed 1) that there was a strong correlation of levels of disaccharides derived from HS in the blood, between those calculated using conventional LC-MS/MS and HT-MS/MS, 2) that levels of HS in the blood were significantly elevated in patients with MPS II and III, but not in MPS IVA, 3) that the level of HS in patients with a severe form of MPS II was higher than that in an attenuated form, 4) that reduction of blood HS level was observed in MPS II patients treated with enzyme replacement therapy or hematopoietic stem cell transplantation, and 5) that levels of HS in newborn DBS were elevated in patients with MPS I, II or III, compared to those of control newborns. In conclusion, HT-MS/MS provides much higher throughput than LC-MS/MS-based methods with similar sensitivity and specificity in an HS assay, indicating that HT-MS/MS may be feasible for diagnosis, monitoring, and newborn screening of MPS.

Establishment of glycosaminoglycan assays for mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by deficiency of the lysosomal enzymes essential for catabolism of glycosaminoglycans (GAGs). Accumulation of undegraded GAGs results in dysfunction of multiple organs, resulting in distinct clinical manifestations. A range of methods have been developed to measure specific GAGs in various human samples to investigate diagnosis, prognosis, pathogenesis, GAG interaction with other molecules, and monitoring therapeutic efficacy. We established ELISA, liquid chromatography tandem mass spectrometry (LC-MS/MS), and an automated high-throughput mass spectrometry (HT-MS/MS) system (RapidFire) to identify epitopes (ELISA) or disaccharides (MS/MS) derived from different GAGs (dermatan sulfate, heparan sulfate, keratan sulfate, and/or chondroitin sulfate). These methods have a high sensitivity and specificity in GAG analysis, applicable to the analysis of blood, urine, tissues, and cells. ELISA is feasible, sensitive, and reproducible with the standard equipment. HT-MS/MS yields higher throughput than conventional LC-MS/MS-based methods while the HT-MS/MS system does not have a chromatographic step and cannot distinguish GAGs with identical molecular weights, leading to a limitation of measurements for some specific GAGs. Here we review the advantages and disadvantages of these methods for measuring GAG levels in biological specimens. We also describe an unexpected secondary elevation of keratan sulfate in patients with MPS that is an indirect consequence of disruption of catabolism of other GAGs.

Assay for Glycosaminoglycans by Tandem Mass Spectrometry and its Applications

Glycosaminoglycans (GAGs) are distributed in the whole body and play a variety of important physiological roles associated with inflammation, growth, coagulation, fibrinolysis, lipolysis, and cell-matrix biology. Accumulation of undegraded GAGs in lysosomes gives rise to a distinct clinical syndrome, mucopolysaccharidoses. Measurement of each specific GAG in a variety of specimens is urgently required to understand GAG interaction with other molecules, physiological status of patients, and prognosis and pathogenesis of the disease. We established a highly sensitive and accurate tandem mass spectrometry (LC-MS/MS) method for measurements of disaccharides derived from four specific GAGs [dermatan sulfate (DS), heparan sulfate (HS), keratan sulfate (KS), and chondroitin sulfate (CS)]. Disaccharides were produced by specific enzyme digestion of each GAG, and quantified by negative ion mode of multiple reaction monitoring. Subclasses of HS and GAGs with identical molecular weights can be separated using a Hypercarbcolumn (2.0 mm×50 mm, 5 μm) with an aectonitrile gradient in ammonium acetate (pH 11.0). We also developed a GAG assay by RapidFire with tandem mass spectrometry (RF-MS/MS). The RF system consists of an integrated solid phase extraction robot that binds and de-salts samples from assay plates and directly injects them into a MS/MS detector, reducing sample processing time to ten seconds. RF-MS/MS consequently yields much faster throughput than conventional LC-MS/MS-based methods. However, the RF system does not have a chromatographic step, and therefore, cannot distinguish GAGs that have identical molecular weights. Both methods can be applied to analysis of dried blood spots, blood, and urine specimens. In this article, we compare the assay methods for GAGs and describe their potential applications.

Newborn screening and diagnosis of mucopolysaccharidoses: application of tandem mass spectrometry

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by the deficiency of lysosomal enzymes. The enzymes are required to break down glycosaminoglycans (GAGs) that help build bone, cartilage, tendons, corneas, skin and connective tissue. In patients with MPS, a missing enzyme leads to the accumulation of GAGs in the cells, blood, connective tissues, and multiple organs. The consequence is permanent, with progressive cellular damage affecting patients' appearance, physical abilities, organ and system function, and skeletal and mental development. The measurement of each specific GAG in a variety of specimens is required to establish the correlation between GAGs and physiological status of patients and/or prognosis and pathogenesis of the disease and to separate the patients with MPS from the healthy controls. We have developed a highly accurate, sensitive, and cost-effective liquid chromatography tandem mass spectrometry (LC-MS/MS) method for measurements of disaccharides derived from four specific GAGs [chondroitin sulfate (CS), dermatan sulfate (DS), heparan sulfate (HS), and keratan sulfate (KS)]. Disaccharides were produced by specific enzyme digestion of each GAG, and subsequently, quantified by negative ion mode of multiple reaction monitoring. Subclasses of GAGs with the same molecular weights can be separated by liquid chromatography. We have also developed another GAG assay by high-throughput mass spectrometry (HT-MS/MS). The HT-MS/MS consists of an integrated solid phase extraction robot that binds and de-salts samples from assay plates and directly injects them into a MS/MS detector, reducing sample processing time to within ten seconds. HT-MS/MS consequently yields much faster throughput than conventional LC-MS/MS-based methods; however, the HT-MS/MS system does not use a chromatographic step, and therefore, cannot separate GAGs that have the same molecular weights. Both techniques can be applied to the analysis of dried blood spots, blood, and urine specimens. In this review, we describe the assay methods for GAGs and the application to newborn screening and diagnosis of MPS.

Impact of Enzyme Replacement Therapy and Hematopoietic Stem Cell Therapy on Growth in Patients with Hunter Syndrome

Patients with Hunter syndrome (mucopolysaccharidosis II) present with skeletal dysplasia including short stature as well as CNS and visceral organ involvement. A previous study on Hunter syndrome indicated an impact on brain and heart involvement after hematopoietic stem cell therapy (HSCT) at an early stage but little impact after enzyme replacement therapy (ERT) (Tanaka et al 2012). Meanwhile, impact on growth in patients with Hunter syndrome treated with ERT and HSCT has not been compared until now. We recently developed baseline growth charts for untreated patients with Hunter syndrome to evaluate the natural history of growth of these patients compared to unaffected controls (Patel et al, 2014). To assess impact of ERT and HSCT on growth, clinical data were obtained from 44 Japanese male patients with MPS II; 26 patients had been treated with ERT, 12 patients had been treated with HSCT, and 6 had been treated with both ERT and HSCT. Height and weight were compared to untreated patients and unaffected controls from the previous study. We demonstrated 1) that MPS II patients, who had been treated with either ERT or HSCT, had increased height and weight when compared to untreated patients, and 2) that HSCT and ERT were equally effective in restoring growth of MPS II patients. In conclusion, HSCT should be considered as one of the primary therapeutic options for early stage treatment of MPS II, as HSCT has also been reported to have a positive effect on brain and heart valve development (Tanaka et al 2012).

Loss of Sip1 leads to migration defects and retention of ectodermal markers during lens development

SIP1 encodes a DNA-binding transcription factor that regulates multiple developmental processes, as highlighted by the pleiotropic defects observed in Mowat-Wilson syndrome, which results from mutations in this gene. Further, in adults, dysregulated SIP1 expression has been implicated in both cancer and fibrotic diseases, where it functionally links TGFβ signaling to the loss of epithelial cell characteristics and gene expression. In the ocular lens, an epithelial tissue important for vision, Sip1 is co-expressed with epithelial markers, such as E-cadherin, and is required for the complete separation of the lens vesicle from the head ectoderm during early ocular morphogenesis. However, the function of Sip1 after early lens morphogenesis is still unknown. Here, we conditionally deleted Sip1 from the developing mouse lens shortly after lens vesicle closure, leading to defects in coordinated fiber cell tip migration, defective suture formation, and cataract. Interestingly, RNA-Sequencing analysis on Sip1 knockout lenses identified 190 differentially expressed genes, all of which are distinct from previously described Sip1 target genes. Furthermore, 34% of the genes with increased expression in the Sip1 knockout lenses are normally downregulated as the lens transitions from the lens vesicle to early lens, while 49% of the genes with decreased expression in the Sip1 knockout lenses are normally upregulated during early lens development. Overall, these data imply that Sip1 plays a major role in reprogramming the lens vesicle away from a surface ectoderm cell fate towards that necessary for the development of a transparent lens and demonstrate that Sip1 regulates distinctly different sets of genes in different cellular contexts.

Therapies of mucopolysaccharidosis IVA (Morquio A syndrome)

INTRODUCTION

Morquio A syndrome (mucopolysaccharidosis type IVA, MPS IVA) is one of the lysosomal storage diseases and is caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS). Deficiency of this enzyme leads to accumulation of glycosaminoglycans (GAGs), keratan sulfate (KS) and chondroitin-6-sulfate (C6S). The majority of KS is produced by chondrocytes, and therefore, the undegraded substrates accumulate mainly in cells and extracelluar matrix (ECM) of cartilage. This has a direct impact on cartilage and bone development, leading to systemic skeletal dysplasia. In patients with Morquio A, cartilage cells are vacuolated, and this results in abnormal chondrogenesis and/or endochondral ossification.

AREAS COVERED

This article describes the advanced therapies of Morquio A, focused on enzyme replacement therapy (ERT) and gene therapy to deliver the drug to avascular bone lesions. ERT and gene therapies for other types of MPS are also discussed, which provide therapeutic efficacy to bone lesions.

EXPERT OPINION

ERT, gene therapy and hematopietic stem therapy are clinically and/or experimentally conducted. However, there is no effective curative therapy for bone lesion to date. One of the limitations for Morquio A therapy is that targeting avascular cartilage tissues remains an unmet challenge. ERT or gene therapy with bone-targeting system will improve the bone pathology and skeletal manifestations more efficiently.

Newborn screening and diagnosis of mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are caused by deficiency of lysosomal enzyme activities needed to degrade glycosaminoglycans (GAGs), which are long unbranched polysaccharides consisting of repeating disaccharides. GAGs include: chondroitin sulfate (CS), dermatan sulfate (DS), heparan sulfate (HS), keratan sulfate (KS), and hyaluronan. Their catabolism may be blocked singly or in combination depending on the specific enzyme deficiency. There are 11 known enzyme deficiencies, resulting in seven distinct forms of MPS with a collective incidence of higher than 1 in 25,000 live births. Accumulation of undegraded metabolites in lysosomes gives rise to distinct clinical syndromes. Generally, the clinical conditions progress if untreated, leading to developmental delay, systemic skeletal deformities, and early death. MPS disorders are potentially treatable with enzyme replacement therapy or hematopoietic stem cell transplantation. For maximum benefit of available therapies, early detection and intervention are critical. We recently developed a novel high-throughput multiplex method to assay DS, HS, and KS simultaneously in blood samples by using high performance liquid chromatography/tandem mass spectrometry for MPS. The overall performance metrics of HS and DS values on MPS I, II, and VII patients vs. healthy controls at newborns were as follows using a given set of cut-off values: sensitivity, 100%; specificity, 98.5-99.4%; positive predictive value, 54.5-75%; false positive rate, 0.62-1.54%; and false negative rate, 0%. These findings show that the combined measurements of these three GAGs are sensitive and specific for detecting all types of MPS with acceptable false negative/positive rates. In addition, this method will also be used for monitoring therapeutic efficacy. We review the history of GAG assay and application to diagnosis for MPS.

Dexamethasone-loaded block copolymer nanoparticles induce leukemia cell death and enhance therapeutic efficacy: a novel application in pediatric nanomedicine

Nanotechnology approaches have tremendous potential for enhancing treatment efficacy with lower doses of chemotherapeutics. Nanoparticle (NP)-based drug delivery approaches are poorly developed for childhood leukemia. Dexamethasone (Dex) is one of the most common chemotherapeutic drugs used in the treatment of childhood leukemia. In this study, we encapsulated Dex in polymeric NPs and validated their antileukemic potential in vitro and in vivo. NPs with an average diameter of 110 nm were assembled from an amphiphilic block copolymer of poly(ethylene glycol) (PEG) and poly(ε-caprolactone) (PCL) bearing pendant cyclic ketals (ECT2). The blank NPs were nontoxic to cultured cells in vitro and to mice in vivo. Encapsulation of Dex into the NPs (Dex-NP) did not compromise the bioactivity of the drug. Dex-NPs induced glucocorticoid phosphorylation and showed cytotoxicity similar to the free Dex in leukemic cells. Studies using NPs labeled with fluorescent dyes revealed leukemic cell surface binding and internalization. In vivo biodistribution studies showed NP accumulation in the liver and spleen with subsequent clearance of the particles with time. In a preclinical model of leukemia, Dex-NPs significantly improved the quality of life and survival of mice as compared to the free drug. To our knowledge, this is the first report showing the efficacy of polymeric NPs to deliver Dex to potentially treat childhood leukemia and reveals that low doses of Dex should be sufficient for inducing cell death and improving survival.

Abstract 4520: Nanotechnology based drug delivery in childhood leukemia therapy: A novel approach to reduce side-effects

Despite attaining 5-year survival rates of 90%; more than 60% of pediatric cancer survivors are affected by at-least one life threatening event in their lifetime. Childhood leukemia is currently treated with a combination of chemotherapeutics that are effective in combating the disease. However, these drugs also affect the normal growing cells in children causing devastating side-effects. The goal of this study is to develop nanosized drug delivery formulations that deliver drugs specifically to leukemic cells and ultimately reduce treatment related side-effects in children. Multi-step chemical transformations were employed to construct amphiphilic block copolymers consisting of hydrophilic polyether (PEG) and hydrophobic polyester (PCL) bearing pendent cyclic ketals. The functional block copolymers self-assemble into micelles with a core-shell architecture comprising a segregated PCL core that encapsulates the steroid drug (Dexamethasone) and a sterically stabilized PEG shell that provides a platform to conjugate targeting moieties. Dexamethasone (Dex) and fluorescent-dye encapsulated nanoparticles (NPs) were formulated by a nanoprecipitation method. The size and morphology of all formulations were analyzed by dynamic light scattering (DLS) and transmission electron microscopy (TEM) methods. The non-toxic nature of the blank-NPs was confirmed both in vitro and in vivo. The drug encapsulated NPs (Dex-NPs) are endocytosed into leukemic cells and induced cytotoxicity similar to that of free Dex, but at reduced doses. The Dex-NPs significantly improved survival in preclinical mouse models of leukemia. A second generation drug encapsulated targeted NPs with transferrin as the targeting moiety improved NP uptake in leukemic cells by comparison to non-targeted NPs. The demonstrated efficacy of such novel nanotherapeutic systems in vitro and in pre-clinical mouse models of acute leukemia have provided the foundation to successfully create novel therapeutic delivery systems that target and treat pediatric hematological malignancies with enhanced efficacy and reduced toxicity.

Citation Format: Vinu Krishnan, Xian Xu, Sonali Barwe, Xiaowei Yang, Scott A. Waldman, Robert W. Mason, Xinqiao Jia, Ayyappan K. Rajasekaran. Nanotechnology based drug delivery in childhood leukemia therapy: A novel approach to reduce side-effects. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4520. doi:10.1158/1538-7445.AM2013-4520

Current and emerging treatments and surgical interventions for Morquio A syndrome: a review

Patients with mucopolysaccharidosis type IVA (MPS IVA; Morquio A syndrome) have accumulation of the glycosaminoglycans, keratan sulfate, and chondroitin-6-sulfate, in bone and cartilage, causing systemic spondyloepiphyseal dysplasia. Features include lumbar gibbus, pectus carinatum, faring of the rib cage, marked short stature, cervical instability and stenosis, kyphoscoliosis, genu valgum, and laxity of joints. Generally, MPS IVA patients are wheelchair-bound as teenagers and do not survive beyond the second or third decade of life as a result of severe bone dysplasia, causing restrictive lung disease and airway narrowing, increasing potential for pneumonia and apnea; stenosis and instability of the upper cervical region; high risk during anesthesia administration due to narrowed airway as well as thoracoabdominal dysfunction; and surgical complications. Patients often need multiple surgical procedures, including cervical decompression and fusion, hip reconstruction and replacement, and femoral or tibial osteotomy, throughout their lifetime. Current measures to intervene in disease progression are largely palliative, and improved therapies are urgently needed. A clinical trial for enzyme replacement therapy (ERT) and an investigational trial for hematopoietic stem cell transplantation (HSCT) are underway. Whether sufficient enzyme will be delivered effectively to bone, especially cartilage (avascular region) to prevent the devastating skeletal dysplasias remains unclear. This review provides an overview of historical aspects of studies on MPS IVA, including clinical manifestations and pathogenesis of MPS IVA, orthopedic surgical interventions, and anesthetic care. It also describes perspectives on potential ERT, HSCT, and gene therapy.