Protein tyrosine phosphatases in glioma biology

PTP4A2 Promotes Glioblastoma Progression and Macrophage Polarization under Microenvironmental Pressure

Phosphatase of regenerating liver 2 (also known as PTP4A2) has been linked to cancer progression. Still, its exact role in glioblastoma (GBM), the most aggressive type of primary brain tumor, remains elusive. In this study, we report that pharmacologic treatment using JMS-053, a pan-phosphatase of regenerating liver inhibitor, inhibits GBM cell viability and spheroid growth. We also show that PTP4A2 is associated with a poor prognosis in gliomas, and its expression correlates with GBM aggressiveness. Using a GBM orthotopic xenograft model, we show that PTP4A2 overexpression promotes tumor growth and reduces mouse survival. Furthermore, PTP4A2 deletion leads to increased apoptosis and proinflammatory signals. Using a syngeneic GBM model, we show that depletion of PTP4A2 reduces tumor growth and induces a shift in the tumor microenvironment (TME) toward an immunosuppressive state. In vitro assays show that cell proliferation is not affected in PTP4A2-deficient or -overexpressing cells, highlighting the importance of the microenvironment in PTP4A2 functions. Collectively, our results indicate that PTP4A2 promotes GBM growth in response to microenvironmental pressure and support the rationale for targeting PTP4A2 as a therapeutic strategy against GBM.

SIGNIFICANCE

High levels of PTP4A2 are associated with poor outcomes in patients with glioma and in mouse models. PTP4A2 depletion increases apoptosis and proinflammatory signals in GBM xenograft models, significantly impacts tumor growth, and rewires the TME in an immunocompetent host. PTP4A2 effects in GBM are dependent on the presence of the TME.

Druggable targets of protein tyrosine phosphatase Family, viz. PTP1B, SHP2, Cdc25, and LMW-PTP: Current scenario on medicinal Attributes, and SAR insights

Protein tyrosine phosphatases (PTPs) are the class of dephosphorylation enzymes that catalyze the removal of phosphate groups from tyrosine residues on proteins responsible for various cellular processes. Any disbalance in signal pathways mediated by PTPs leads to various disease conditions like diabetes, obesity, cancers, and autoimmune disorders. Amongst the PTP superfamily, PTP1B, SHP2, Cdc25, and LMW-PTP have been prioritized as druggable targets for developing medicinal agents. PTP1B is an intracellular PTP enzyme that downregulates insulin and leptin signaling pathways and is involved in insulin resistance and glucose homeostasis. SHP2 is involved in the RAS-MAPK pathway and T cell immunity. Cdk-cyclin complex activation occurs by Cdc25-PTPs involved in cell cycle regulation. LMW-PTPs are involved in PDGF/PDGFR, Eph/ephrin, and insulin signaling pathways, resulting in certain diseases like diabetes mellitus, obesity, and cancer. The signaling cascades of PTP1B, SHP2, Cdc25, and LMW-PTPs have been described to rationalize their medicinal importance in the pathophysiology of diabetes, obesity, and cancer. Their binding sites have been explored to overcome the hurdles in discovering target selective molecules with optimum potency. Recent developments in the synthetic molecules bearing heterocyclic moieties against these targets have been explored to gain insight into structural features. The elaborated SAR investigation revealed the effect of substituents on the potency and target selectivity, which can be implicated in the further discovery of newer medicinal agents targeting the druggable members of the PTP superfamily.

Role of Non-Receptor-Type Tyrosine Phosphatases in Brain-Related Diseases

The non-receptor protein tyrosine phosphatase is a class of enzymes that catalyze the dephosphorylation of phosphotyrosines in protein molecules. They are involved in cellular signaling by regulating the phosphorylation status of a variety of receptors and signaling molecules within the cell, thereby influencing cellular physiological and pathological processes. In this article, we detail multiple non-receptor tyrosine phosphatase and non-receptor tyrosine phosphatase genes involved in the pathological process of brain disease. These include PTPN6, PTPN11, and PTPN13, which are involved in glioma signaling; PTPN1, PTPN5, and PTPN13, which are involved in the pathogenesis of Alzheimer's disease Tau protein lesions, PTPN23, which may be involved in the pathogenesis of Epilepsy and PTPN1, which is involved in the pathogenesis of Parkinson's disease. The role of mitochondrial tyrosine phosphatase in brain diseases was also discussed. Non-receptor tyrosine phosphatases have great potential for targeted therapies in brain diseases and are highly promising research areas.

The identification of key genes and pathways in glioblastoma by bioinformatics analysis

GBM is the most common and aggressive type of brain tumor. It is classified as a grade IV tumor by the WHO, the highest grade. Prognosis is generally poor, with most patients surviving only about a year. Only 5% of patients survive longer than 5 years. Understanding the molecular mechanisms that drive GBM progression is critical for developing better diagnostic and treatment strategies. Identifying key genes involved in GBM pathogenesis is essential to fully understand the disease and develop targeted therapies. In this study two datasets, GSE108474 and GSE50161, were obtained from the Gene Expression Omnibus (GEO) to compare gene expression between GBM and normal samples. Differentially expressed genes (DEGs) were identified and analyzed. To construct a protein-protein interaction (PPI) network of the commonly up-regulated and down-regulated genes, the STRING 11.5 and Cytoscape 3.9.1 were utilized. Key genes were identified through this network analysis. The GEPIA database was used to confirm the expression levels of these key genes and their association with survival. Functional and pathway enrichment analyses on the DEGs were conducted using the Enrichr server. In total, 698 DEGs were identified, consisting of 377 up-regulated genes and 318 down-regulated genes. Within the PPI network, 11 key up-regulated genes and 13 key down-regulated genes associated with GBM were identified. NOTCH1, TOP2A, CD44, PTPRC, CDK4, HNRNPU, and PDGFRA were found to be important targets for potential drug design against GBM. Additionally, functional enrichment analysis revealed the significant impact of Epstein-Barr virus (EBV), Cell Cycle, and P53 signaling pathways on GBM.

Encapsulated Oxovanadium(IV) and Dioxovanadium(V) Complexes into Solid Lipid Nanoparticles Increase Cytotoxicity Against MDA-MB-231 Cell Line

Introduction

Solid lipid nanoparticles (SLN) have been considered lately as promising drug delivery system in treatment of many human diseases including cancers. We previously studied potential drug compounds that were effective inhibitors of PTP1B phosphatase - possible target for breast cancer treatment. Based on our studies, two complexes were selected for encapsulation into the SLNs, the compound 1 ([VO(dipic)(dmbipy)] · 2 H₂O) and compound 2 ([VOO(dipic)](2-phepyH) · H₂O). Here, we investigate the effect of encapsulation of those compounds on cell cytotoxicity against MDA-MB-231 breast cancer cell line. The study also included the stability evaluation of the obtained nanocarriers with incorporated active substances and characterization of their lipid matrix. Moreover, the cell cytotoxicity studies against the MDA-MB-231 breast cancer cell line in comparison and in combination with vincristine have been performed. Wound healing assay was carried out to observe cell migration rate.

Methods

The properties of the SLNs such as particle size, zeta potential (ZP), and polydispersity index (PDI) were investigated. The morphology of SLNs was observed by scanning electron microscopy (SEM), while the crystallinity of the lipid particles was analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The cell cytotoxicity of complexes and their encapsulated forms was carried out against MDA-MB-231 breast cancer cell line using standard MTT protocols. The wound healing assay was performed using live imaging microscopy.

Results

SLNs with a mean size of 160 ± 25 nm, a ZP of -34.00 ± 0.5, and a polydispersity index of 30 ± 5% were obtained. Encapsulated forms of compounds showed significantly higher cytotoxicity also in co-incubation with vincristine. Moreover, our research shows that the best compound was complex 2 encapsulated into lipid nanoparticles.

Conclusion

We observed that encapsulation of studied complexes into SLNs increases their cell cytotoxicity against MDA-MB-231 cell line and enhanced the effect of vincristine.

Protein Tyrosine Phosphatase Receptor Type Z in Central Nervous System Disease

Gliomas are among the most common tumors of the central nervous system and include highly malignant subtypes, such as glioblastoma, which are associated with poor prognosis. Effective treatments are therefore urgently needed. Despite the recent advances in neuroimaging technologies, differentiating gliomas from other brain diseases such as multiple sclerosis remains challenging in some patients, and often requires invasive brain biopsy. Protein tyrosine phosphatase receptor type Z (PTPRZ) is a heavily glycosylated membrane protein that is highly expressed in the central nervous system. Several reports analyzing mouse tumor models suggest that PTPRZ may have potential as a therapeutic target for gliomas. A soluble cleaved form of PTPRZ (sPTPRZ) in the cerebrospinal fluid is markedly upregulated in glioma patients, making it another promising diagnostic biomarker. Intriguingly, PTPRZ is also involved in the process of remyelination in multiple sclerosis. Indeed, lowered PTPRZ glycosylation by deletion of the glycosyltransferase gene leads to reduced astrogliosis and enhanced remyelination in mouse models of demyelination. Here, we review the expression, molecular structure, and biological roles of PTPRZ. We also discuss glioma and demyelinating diseases, as well as the pathological role of PTPRZ and its application as a diagnostic marker and therapeutic target.

New phase therapeutic pursuits for targeted drug delivery in glioblastoma multiforme

Glioblastoma multiforme (GBM) is known as the most aggressive and prevalent brain tumor with a high mortality rate. It is reported in people who are as young as 10 years old to as old as over 70 years old, exhibiting inter and intra tumor heterogeneity. There are several genomic and proteomic investigations that have been performed to find the unexplored potential targets of the drug against GBM. Therefore, certain effective targets have been taken to further validate the studies embarking on the robustness in the field of medicinal chemistry followed by testing in clinical trials. Also, The Cancer Genome Atlas (TCGA) project has identified certain overexpressed targets involved in the pathogenesis of GBM in three major pathways, i.e., tumor protein 53 (p53), retinoblastoma (RB), and receptor tyrosine kinase (RTK)/rat sarcoma virus (Ras)/phosphoinositide 3-kinase (PI3K) pathways. This review focuses on the compilation of recent developments in the fight against GBM thus, directing future research into the elucidation of pathogenesis and potential cure for GBM. Also, it highlights the potential biomarkers that have undergone extensive research and have promising prognostic and predictive values. Additionally, this manuscript analyses the advent of gene therapy and immunotherapy, unlocking the way to consider treatment approaches other than, or in addition to, conventional chemo-radiation therapies. This review study encompasses all the relevant research studies associated with the pathophysiology, occurrence, diagnostic tools, and therapeutic intervention for GBM. It highlights the evolution of various therapeutic perspectives against GBM from the most conventional form of radiotherapy to the recent advancement of gene/cell/immune therapy. Further, the review focuses on various targeted therapies for GBM including chemotherapy sensitization, radiotherapy, nanoparticles based, immunotherapy, cell therapy, and gene therapy which would offer a comprehensive account for exploring several facets related to GBM prognostics.

Whole-exome sequencing, EGFR amplification and infiltration patterns in human glioblastoma

Glioblastoma (GBM) is the most common malignant primary brain tumor in adults. This cancer shows rapid, highly infiltrative growth, that invades individually or in small groups the surrounding tissue. The aggressive tumor biology of GBM has devastating consequences with a median survival of 15 months. GBM often has Epidermal Growth Factor Receptor (EGFR) abnormalities. Despite recent advances in the study of GBM tumor biology, it is unclear whether mutations in GBM are related to EGFR amplification and relevant phenotypes like tumor infiltration. This study aimed to perform whole-exome sequencing analysis in 30 human GBM samples for identifying mutational portraits associated with EGFR amplification and infiltrative patterns. Our results show that EGFR-amplified tumors have overall higher mutation rates than EGFR-no-amplified. Six genes out of 2029 candidate genes show mutations associated with EGFR amplification status. Mutations in these genes for GBM are novel, not previously reported in GBM, and with little presence in the TCGA database. GPR179, USP48, and BLK show mutation only in EGFR-amplified cases, and all the affected cases exhibit diffuse infiltrative patterns. On the other hand, mutations in ADGB, EHHADH, and PTPN13, were present only in the EGFR-no-amplified group with a more diverse infiltrative phenotype. Overall, our work identified different mutational portraits of GBM related to well-established features like EGFR amplification and tumor infiltration.

Glioma-Targeted Therapeutics: Computer-Aided Drug Design Prospective

Amongst the several types of brain cancers known to humankind, glioma is one of the most severe and life-threatening types of cancer, comprising 40% of all primary brain tumors. Recent reports have shown the incident rate of gliomas to be 6 per 100,000 individuals per year globally. Despite the various therapeutics used in the treatment of glioma, patient survival rate remains at a median of 15 months after undergoing first-line treatment including surgery, radiation, and chemotherapy with Temozolomide. As such, the discovery of newer and more effective therapeutic agents is imperative for patient survival rate. The advent of computer-aided drug design in the development of drug discovery has emerged as a powerful means to ascertain potential hit compounds with distinctively high therapeutic effectiveness against glioma. This review encompasses the recent advances of bio-computational in-silico modeling that have elicited the discovery of small molecule inhibitors and/or drugs against various therapeutic targets in glioma. The relevant information provided in this report will assist researchers, especially in the drug design domains, to develop more effective therapeutics against this global disease.

T Cell Protein Tyrosine Phosphatase in Glucose Metabolism

T cell protein tyrosine phosphatase (TCPTP), a vital regulator in glucose metabolism, inflammatory responses, and tumor processes, is increasingly considered a promising target for disease treatments and illness control. This review discusses the structure, substrates and main biological functions of TCPTP, as well as its regulatory effect in glucose metabolism, as an attempt to be referenced for formulating treatment strategies of metabolic disorders. Given the complicated regulation functions in different tissues and organs of TCPTP, the development of drugs inhibiting TCPTP with a higher specificity and a better biocompatibility is recognized as a promising therapeutic strategy for diabetes or obesity. Besides, treatments targeting TCPTP in a specific tissue or organ are suggested to be considerably promising.

SHP-2-Mediated Upregulation of ZEB1 Is Important for PDGF-B-Induced Cell Proliferation and Metastatic Phenotype in Triple Negative Breast Cancer

Background: Triple negative breast cancer (TNBC), a fatal malignant tumor, is characterized by a lack of estrogen and progesterone hormone receptors and overexpression of HER2. Due to its characteristics, there are no effective targeted therapies for TNBC. Therefore, it is critical to identify the crucial factors that participate in modulating TNBC progression and explore the underlying molecular mechanism. Methods: CCK-8, bromodeoxyuridine incorporation, western blotting, qPCR, and transwell assays were utilized to evaluate breast cancer cell proliferation, migration, and invasion. Results: Activation of platelet-derived growth factor (PDGF)-B/PDGF receptor (PDGFR) promoted the proliferation and metastatic phenotype of TNBC cells; however, these effects were attenuated by SHP-2 knockdown. Moreover, PDGF-B promoted the expression of zinc finger E-box binding homeobox 1 (ZEB1) by downregulating the expression of miR-200. Furthermore, knockdown of ZEB1 mitigated the promoting effects of PDGF-B on cell proliferation and migration. In addition, the regulatory effects of PDGF-B on miR-200 and ZEB1 were mediated through the SHP-2/Akt pathway. Conclusion: Our findings highlight the important roles of PDGF-B/PDGFR and their downstream signaling pathways in regulating cell proliferation and metastatic phenotype in TNBC. Hence, these molecules may serve as novel therapeutic targets for TNBC in the future.

11 Long noncoding RNA UCA1 functions as miR-135a sponge to promote the epithelial to mesenchymal transition in glioma

The dysregulation of long noncoding (lncRNA) UCA1 may play an important role in tumor progression. However, the function in gliomas is unclear. Therefore, this experiment was designed to explore the pathogenesis of glioma based on lncRNA UCA1. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of lncRNA UCA1, miR-135a, and HOXD9 in gliomas tissues. The effect of lncRNA UCA1 and miR-135a on tumor cell proliferation and migration invasiveness was examined by CCK-8 and transwell assays. Target gene prediction and screening, luciferase reporter assay were used to verify downstream target genes of lncRNA UCA1. Expression of E-cadherin, N-cadherin, vimentin, and HOXD9 was detected by RT-qPCR and Western blotting. The tumor changes in mice were detected by in vivo experiments in nude mice. lncRNA UCA1 was highly expressed in glioma tissues and cell lines. lncRNA UCA1 expression was associated with significantly poor overall survival in gliomas. Moreover, lncRNA UCA1 significantly enhanced cell proliferation and migration, and promoted the occurrence of EMT. In addition, lncRNA UCA1 promoted the development of EMT by positively regulating HOXD9 expression as a miR-135a sponge. In vivo experiments indicated that UCA1 exerted its biological functions by modulating miR-135a and HOXD9. In conclusion, lncRNA UCA1 can induce the activation of HOXD9 by inhibiting the expression of miR-135a and promote the occurrence of EMT in glioma.

A novel PTPRZ1-ETV1 fusion in gliomas

The aggressive nature of malignant gliomas and their genetic and clinical heterogeneity present a major challenge in their diagnosis and treatment. Development of targeted therapy brought attention on detecting novel gene fusions, since they represent promising therapeutic targets (eg, TRK inhibitors in NTRK fusion-positive tumors). Using targeted next-generation sequencing, we prospectively analyzed 205 primary brain tumors and detected a novel PTPRZ1-ETV1 fusion transcript in 11 of 191 (5.8%) gliomas, including nine glioblastomas, one anaplastic oligodendroglioma and one pilocytic astrocytoma. PTPRZ1-ETV1 fusion was confirmed by RT-PCR followed by Sanger sequencing, and in-silico analysis predicted a potential driver role. The newly detected fusion consists of the PTPRZ1 promoter in frame with the highly conserved DNA-binding domain of ETV1 transcription factor. The ETV1 and PTPRZ1 genes are known oncogenes, involved in processes of tumor development. ETV1 is a member of the ETS family of transcription factors, already known oncogenic drivers in Ewing sarcoma, prostate cancer and gastrointestinal stromal tumors, but not in gliomas. Its overexpression contributes to tumor growth and more aggressive tumor behavior. PTPRZ1 is already considered to be a tumor growth promoting oncogene in gliomas. In 8%-16% of gliomas, PTPRZ1 is fused to the MET oncogene, resulting in a PTPRZ1-MET fusion, which is associated with poorer prognosis but is also a positive predictive biomarker for treatment with kinase inhibitors. In view of the oncogenic role that the two fusion partners, PTPRZ1 and ETV1, exhibit in other malignancies, PTPRZ1-ETV1 fusion might present a novel potential therapeutic target in gliomas. Although histopathological examination of PTPRZ1-ETV1 fusion-positive gliomas did not reveal any specific or unique pathological features, and the follow-up period was too short to assess prognostic value of the fusion, careful monitoring of patients and their response to therapy might provide additional insights into the prognostic and predictive value of this novel fusion.

Multicellular gene network analysis identifies a macrophage-related gene signature predictive of therapeutic response and prognosis of gliomas

BACKGROUND

The tumor-associated microenvironment plays important roles in tumor progression and drug resistance. However, systematic investigations of macrophage-tumor cell interactions to identify novel macrophage-related gene signatures in gliomas for predicting patient prognoses and responses to targeted therapies are lacking.

METHODS

We developed a multicellular gene network approach to investigating the prognostic role of macrophage-tumor cell interactions in tumor progression and drug resistance in gliomas. Multicellular gene networks connecting macrophages and tumor cells were constructed from re-grouped drug-sensitive and drug-resistant samples of RNA-seq data in mice gliomas treated with BLZ945 (a CSF1R inhibitor). Subsequently, a differential network-based COX regression model was built to identify the risk signature using a cohort of 310 glioma samples from the Chinese Glioma Genome Atlas database. A large independent validation set of 690 glioma samples from The Cancer Genome Atlas database was used to test the prognostic significance and accuracy of the gene signature in predicting prognosis and targeted therapeutic response of glioma patients.

RESULTS

A macrophage-related gene signature was developed consisting of twelve genes (ANPEP, DPP4, PRRG1, GPNMB, TMEM26, PXDN, CDH6, SCN3A, SEMA6B, CCDC37, FANCA, NETO2), which was tested in the independent validation set to examine its prognostic significance and accuracy. The generation of 1000 random gene signatures by a bootstrapping scheme justified the non-random nature of the macrophage-related gene signature. Moreover, the discovered gene signature was verified to be predictive of the sensitivity or resistance of glioma patients to molecularly targeted therapeutics and outperformed other existing gene signatures. Additionally, the macrophage-related gene signature was an independent and the strongest prognostic factor when adjusted for clinicopathologic risk factors and other existing gene signatures.

CONCLUSION

The multicellular gene network approach developed herein indicates profound roles of the macrophage-mediated tumor microenvironment in the progression and drug resistance of gliomas. The identified macrophage-related gene signature has good prognostic value for predicting resistance to targeted therapeutics and survival of glioma patients, implying that combining current targeted therapies with new macrophage-targeted therapy may be beneficial for the long-term treatment outcomes of glioma patients.

Protein Phosphatases-A Touchy Enemy in the Battle Against Glioblastomas: A Review

Glioblastoma (GBM) is the most common malignant tumor arising from brain parenchyma. Although many efforts have been made to develop therapies for GBM, the prognosis still remains poor, mainly because of the difficulty in total resection of the tumor mass from brain tissue and the resistance of the residual tumor against standard chemoradiotherapy. Therefore, novel adjuvant therapies are urgently needed. Recent genome-wide analyses of GBM cases have clarified molecular signaling mechanisms underlying GBM biology. However, results of clinical trials targeting phosphorylation-mediated signaling have been unsatisfactory to date. Protein phosphatases are enzymes that antagonize phosphorylation signaling by dephosphorylating phosphorylated signaling molecules. Recently, the critical roles of phosphatases in the regulation of oncogenic signaling in malignant tumor cells have been reported, and tumorigenic roles of deregulated phosphatases have been demonstrated in GBM. However, a detailed mechanism underlying phosphatase-mediated signaling transduction in the regulation of GBM has not been elucidated, and such information is necessary to apply phosphatases as a therapeutic target for GBM. This review highlights and summarizes the phosphatases that have crucial roles in the regulation of oncogenic signaling in GBM cells.

Signal transduction pathways and resistance to targeted therapies in glioma

Although surgical techniques and adjuvant therapies have undergone progressive development for decades, the therapeutic outcomes for treating glioblastoma (GBM) remain poor. The main reasons for the poor prognosis of gliomas are that limited tumor tissue that can be resected (to preserve brain functions) and that residual tumors are often resistant to irradiation and chemotherapy. Therefore, overcoming the resistance of residual tumors against adjuvant therapy is urgently needed for glioma treatment. Recent large cohort studies of genetic alterations in GBM demonstrated that both genetic information and intracellular molecular signaling are networked in gliomas and that such information may help clarify which molecules or signals serve essential roles in resistance against radiation or chemotherapy, highlighting them as potential novel therapeutic targets against refractory gliomas. In this review, we summarize the current understanding of molecular networks that govern glioma biology, mainly based on cohort studies or recent evidence, with a focus on how intracellular signaling molecules in gliomas associate with each other and regulate refractoriness against current therapy.

Exploring the pathogenesis of canine epilepsy using a systems genetics method and implications for anti-epilepsy drug discovery

Epilepsy is a common neurological disorder in domestic dogs. However, its complex mechanism involves multiple genetic and environmental factors that make it challenging to identify the real pathogenic factors contributing to epilepsy, particularly for idiopathic epilepsy. Conventional genome-wide association studies (GWASs) can detect various genes associated with epilepsy, although they primarily detect the effects of single-site mutations in epilepsy while ignoring their interactions. In this study, we used a systems genetics method combining both GWAS and gene interactions and obtained 26 significantly mutated subnetworks. Among these subnetworks, seven genes were reported to be involved in neurological disorders. Combined with gene ontology enrichment analysis, we focused on 4 subnetworks that included traditional GWAS-neglected genes. Moreover, we performed a drug enrichment analysis for each subnetwork and identified significantly enriched candidate anti-epilepsy drugs using a hypergeometric test. We discovered 22 potential drug combinations that induced possible synergistic effects for epilepsy treatment, and one of these drug combinations has been confirmed in the Drug Combination database (DCDB) to have beneficial anti-epileptic effects. The method proposed in this study provides deep insight into the pathogenesis of canine epilepsy and implications for anti-epilepsy drug discovery.

Proteinaceous Regulators and Inhibitors of Protein Tyrosine Phosphatases

Proper control of the phosphotyrosine content in signal transduction proteins is essential for normal cell behavior and is lost in many pathologies. Attempts to normalize aberrant tyrosine phosphorylation levels in disease states currently involve either the application of small compounds that inhibit tyrosine kinases (TKs) or the addition of growth factors or their mimetics to boost receptor-type TK activity. Therapies that target the TK enzymatic counterparts, the multi-enzyme family of protein tyrosine phosphatases (PTPs), are still lacking despite their undisputed involvement in human diseases. Efforts to pharmacologically modulate PTP activity have been frustrated by the conserved structure of the PTP catalytic core, providing a daunting problem with respect to target specificity. Over the years, however, many different protein interaction-based regulatory mechanisms that control PTP activity have been uncovered, providing alternative possibilities to control PTPs individually. Here, we review these regulatory principles, discuss existing biologics and proteinaceous compounds that affect PTP activity, and mention future opportunities to drug PTPs via these regulatory concepts.

PRL-3 is a potential glioblastoma prognostic marker and promotes glioblastoma progression by enhancing MMP7 through the ERK and JNK pathways

Purpose: Glioblastoma is the most common and aggressive type of primary brain malignancy and is associated with a poor prognosis. Previously, we found that phosphatase of regenerating liver-3 (PRL-3) was significantly up-regulated in glioblastoma as determined by a microarray analysis. However, the function of PRL-3 in glioblastoma remains unknown. We aimed to investigate the clinical relationship between PRL-3 and glioblastoma, and uncover the mechanisms of PRL-3 in the process of glioblastoma.

Methods: PRL-3 expression was evaluated in 61 glioblastoma samples and 4 cell lines by RT-qPCR and immunohistochemistry. Kaplan-Meier analysis was performed to evaluate the prognostic value of PRL-3 for overall survival (OS) and progression-free survival (PFS) for glioblastoma patients. Proliferation was evaluated by Cell Counting Kit-8 (CCK-8) assay and EdU proliferation assay, migration and invasion by wound-closure/Transwell assays, and qRT-PCR/immunoblotting/IHC were used for both in vivo and in vitro investigations.

Result: A high PRL-3 expression level was closely correlated with unfavorable OS and PFS for glioblastoma patients, and was also significantly correlated with Ki-67 expression. Down-regulation of PRL-3 inhibited glioma cell proliferation, invasion and migration through ERK/JNK/matrix metalloproteinase 7 (MMP7) in vitro and in vivo.

Conclusions: PRL-3 expression enhances the invasion and proliferation of glioma cells, highlighting this phosphatase as a novel prognostic candidate and an attractive target for future therapy in glioblastoma.

Allosteric inhibition induces an open WPD-loop: a new avenue towards glioblastoma therapy

Structural mechanism of inhibition of NAZ2329 at the allosteric site of PTPRZ, with particular emphasis on the dynamics of the WPD-loop.

IGF2 mRNA binding protein 3 (IMP3) mediated regulation of transcriptome and translatome in glioma cells

RNA binding proteins mediate global regulation at the level of transcriptome and translatome of a cell. We studied the global level expression changes regulated by IMP3 in transcriptome and translatome by performing microarray using total cellular RNA and heavy polysome derived RNA of IMP3 silenced glioma cells respectively. Differentially regulated transcripts at the transcriptome level (n = 2388) and at the level of translatome (n = 479) were identified. Further, these transcripts were classified as direct and indirect targets on the basis of presence of IMP3 binding site. Additional investigation revealed that direct targets at transcriptome level were found to be associated with processes related to cell cycle, whereas direct targets at the translatome level participated in apoptosis related pathways. Probable mechanism of indirect regulation at both the levels is also investigated. Collectively, our study reveals multi-level gene expression regulation imposed by IMP3 in glioma cells.

The Protein Tyrosine Phosphatase Shp2 Regulates Oligodendrocyte Differentiation and Early Myelination and Contributes to Timely Remyelination

Shp2 is a nonreceptor protein tyrosine phosphatase that has been shown to influence neurogenesis, oligodendrogenesis, and oligodendrocyte differentiation. Furthermore, Shp2 is a known regulator of the Akt/mammalian target of rapamycin and ERK signaling pathways in multiple cellular contexts, including oligodendrocytes. Its role during later postnatal CNS development or in response to demyelination injury has not been examined. Based on the current studies, we hypothesize that Shp2 is a negative regulator of CNS myelination. Using transgenic mouse technology, we show that Shp2 is involved in oligodendrocyte differentiation and early myelination, but is not necessary for myelin maintenance. We also show that Shp2 regulates the timely differentiation of oligodendrocytes following lysolecithin-induced demyelination, although apparently normal remyelination occurs at a delayed time point. These data suggest that Shp2 is a relevant therapeutic target in demyelinating diseases such as multiple sclerosis.SIGNIFICANCE STATEMENT In the present study, we show that the protein phosphatase Shp2 is an important mediator of oligodendrocyte differentiation and myelination, both during developmental myelination as well as during myelin regeneration. We provide important insight into the signaling mechanisms regulating myelination and propose that Shp2 acts as a transient brake to the developmental myelination process. Furthermore, we show that Shp2 regulates oligodendrocyte differentiation following demyelination and therefore has important therapeutic implications in diseases such as multiple sclerosis.

Targeting PTPRZ inhibits stem cell-like properties and tumorigenicity in glioblastoma cells

The R5 subfamily of receptor-type protein tyrosine phosphatases (RPTPs) comprises PTPRZ and PTPRG. A recent study on primary human glioblastomas suggested a close association between PTPRZ1 (human PTPRZ) expression and cancer stemness. However, the functional roles of PTPRZ activity in glioma stem cells have remained unclear. In the present study, we found that sphere-forming cells from the rat C6 and human U251 glioblastoma cell lines showed high expression levels of PTPRZ-B, the short receptor isoform of PTPRZ. Stable PTPRZ knockdown altered the expression levels of stem cell transcription factors such as SOX2, OLIG2, and POU3F2 and decreased the sphere-forming abilities of these cells. Suppressive effects on the cancer stem-like properties of the cells were also observed following the knockdown of PTPRG. Here, we identified NAZ2329, a cell-permeable small molecule that allosterically inhibits both PTPRZ and PTPRG. NAZ2329 reduced the expression of SOX2 in C6 and U251 cells and abrogated the sphere-forming abilities of these cells. Tumor growth in the C6 xenograft mouse model was significantly slower with the co-treatment of NAZ2329 with temozolomide, an alkylating agent, than with the individual treatments. These results indicate that pharmacological inhibition of R5 RPTPs is a promising strategy for the treatment of malignant gliomas.

Comprehensive protein tyrosine phosphatase mRNA profiling identifies new regulators in the progression of glioma

The infiltrative behavior of diffuse gliomas severely reduces therapeutic potential of surgical resection and radiotherapy, and urges for the identification of new drug-targets affecting glioma growth and migration. To address the potential role of protein tyrosine phosphatases (PTPs), we performed mRNA expression profiling for 91 of the 109 known human PTP genes on a series of clinical diffuse glioma samples of different grades and compared our findings with in silico knowledge from REMBRANDT and TCGA databases. Overall PTP family expression levels appeared independent of characteristic genetic aberrations associated with lower grade or high grade gliomas. Notably, seven PTP genes (DUSP26, MTMR4, PTEN, PTPRM, PTPRN2, PTPRT and PTPRZ1) were differentially expressed between grade II-III gliomas and (grade IV) glioblastomas. For DUSP26, PTEN, PTPRM and PTPRT, lower expression levels correlated with poor prognosis, and overexpression of DUSP26 or PTPRT in E98 glioblastoma cells reduced tumorigenicity. Our study represents the first in-depth analysis of PTP family expression in diffuse glioma subtypes and warrants further investigations into PTP-dependent signaling events as new entry points for improved therapy.

Shp2 Deficiency Impairs the Inflammatory Response Against Haemophilus influenzae by Regulating Macrophage Polarization

Macrophages can polarize and differentiate to regulate initiation, development, and cessation of inflammation during pulmonary infection with nontypeable Haemophilus influenzae (NTHi). However, the underlying molecular mechanisms driving macrophage phenotypic differentiation are largely unclear. Our study investigated the role of Shp2, a Src homology 2 domain-containing phosphatase, in the regulation of pulmonary inflammation and bacterial clearance. Shp2 levels were increased upon NTHi stimulation. Selective inhibition of Shp2 in mice led to an attenuated inflammatory response by skewing macrophages toward alternatively activated macrophage (M2) polarization. Upon pulmonary NTHi infection, Shp2(-/-) mice, in which the gene encoding Shp2 in monocytes/macrophages was deleted, showed an impaired inflammatory response and decreased antibacterial ability, compared with wild-type controls. In vitro data demonstrated that Shp2 regulated activated macrophage (M1) gene expression via activation of p65-nuclear factor-κB signaling, independent of p38 and extracellular regulated kinase-mitogen-activated proteins kinase signaling pathways. Taken together, our study indicates that Shp2 is required to orchestrate macrophage function and regulate host innate immunity against pulmonary bacterial infection.

Small-molecule inhibition of PTPRZ reduces tumor growth in a rat model of glioblastoma

Protein tyrosine phosphatase receptor-type Z (PTPRZ) is aberrantly over-expressed in glioblastoma and a causative factor for its malignancy. However, small molecules that selectively inhibit the catalytic activity of PTPRZ have not been discovered. We herein performed an in vitro screening of a chemical library, and identified SCB4380 as the first potent inhibitor for PTPRZ. The stoichiometric binding of SCB4380 to the catalytic pocket was demonstrated by biochemical and mass spectrometric analyses. We determined the crystal structure of the catalytic domain of PTPRZ, and the structural basis of the binding of SCB4380 elucidated by a molecular docking method was validated by site-directed mutagenesis studies. The intracellular delivery of SCB4380 by liposome carriers inhibited PTPRZ activity in C6 glioblastoma cells, and thereby suppressed their migration and proliferation in vitro and tumor growth in a rat allograft model. Therefore, selective inhibition of PTPRZ represents a promising approach for glioma therapy.

Intracellular and extracellular domains of protein tyrosine phosphatase PTPRZ-B differentially regulate glioma cell growth and motility

Gliomas are primary brain tumors for which surgical resection and radiotherapy is difficult because of the diffuse infiltrative growth of the tumor into the brain parenchyma. For development of alternative, drug-based, therapies more insight in the molecular processes that steer this typical growth and morphodynamic behavior of glioma cells is needed. Protein tyrosine phosphatase PTPRZ-B is a transmembrane signaling molecule that is found to be strongly up-regulated in glioma specimens. We assessed the contribution of PTPRZ-B protein domains to tumor cell growth and migration, via lentiviral knock-down and over-expression using clinically relevant glioma xenografts and their derived cell models. PTPRZ-B knock-down resulted in reduced migration and proliferation of glioma cells in vitro and also inhibited tumor growth in vivo. Interestingly, expression of only the PTPRZ-B extracellular segment was sufficient to rescue the in vitro migratory phenotype that resulted from PTPRZ-B knock-down. In contrast, PTPRZ-B knock-down effects on proliferation could be reverted only after re-expression of PTPRZ-B variants that contained its C-terminal PDZ binding domain. Thus, distinct domains of PTPRZ-B are differentially required for migration and proliferation of glioma cells, respectively. PTPRZ-B signaling pathways therefore represent attractive therapeutic entry points to combat these tumors.

Deletion of Atf6α impairs astroglial activation and enhances neuronal death following brain ischemia in mice

To dissect the role of endoplasmic reticulum (ER) stress and unfolded protein response in brain ischemia, we investigated the relevance of activating transcription factor 6α (ATF6α), a master transcriptional factor in the unfolded protein response, after permanent middle cerebral artery occlusion (MCAO) in mice. Enhanced expression of glucose-regulated protein78, a downstream molecular chaperone of ATF6α, was observed in both neurons and glia in the peri-infarct region of wild-type mice after MCAO. Analysis using wild-type and Atf6α(-/-) mice revealed a larger infarct volume and increased cell death in the peri-ischemic region of Atf6α(-/-) mice 5 days after MCAO. These phenotypes in Atf6α(-/-) mice were associated with reduced levels of astroglial activation/glial scar formation, and a spread of tissue damage into the non-infarct area. Further analysis in mice and cultured astrocytes revealed that signal transducer and activator of transcription 3 (STAT3)-glial fibrillary acidic protein signaling were diminished in Atf6α(-/-) astrocytes. A chemical chaperone, 4-phenylbutyrate, restored STAT3-glial fibrillary acidic protein signaling, while ER stressors, such as tunicamycin and thapsigargin, almost completely abolished signaling in cultured astrocytes. Furthermore, ER stress-induced deactivation of STAT3 was mediated, at least in part, by the ER stress-responsive tyrosine phosphatase, TC-PTP/PTPN2. These results suggest that ER stress plays critical roles in determining the level of astroglial activation and neuronal survival after brain ischemia.

Tyrosine phosphatase Shp2 mediates the estrogen biological action in breast cancer via interaction with the estrogen extranuclear receptor

The extranuclear estrogen receptor pathway opens up novel perspectives in many physiological and pathological processes, especially in breast carcinogenesis. However, its function and mechanisms are not fully understood. Herein we present data identifying Shp2, a SH2-containing tyrosine phosphatase, as a critical component of extranuclear ER pathway in breast cancer. The research checked that the effect of Shp2 on the tumor formation and growth in animal model and investigated the regulation of Shp2 on the bio-effect and signaling transduction of estrogen in breast cancer cell lines. The results showed that Shp2 was highly expressed in more than 60% of total 151 breast cancer cases. The inhibition of Shp2 activity by PHPS1 (a Shp2 inhibitor) delayed the development of dimethylbenz(a)anthracene (DMBA)-induced tumors in the rat mammary gland and also blocked tumor formation in MMTV-pyvt transgenic mice. Estradiol (E2) stimulated protein expression and phosphorylation of Shp2, and induced Shp2 binding to ERα and IGF-1R around the membrane to facilitate the phosphorylation of Erk and Akt in breast cancer cells MCF7. Shp2 was also involved in several biological effects of the extranuclear ER-initiated pathway in breast cancer cells. Specific inhibitors (phps1, phps4 and NSC87877) or small interference RNAs (siRNA) of Shp2 remarkably suppressed E2-induced gene transcription (Cyclin D1 and trefoil factor 1 (TFF1)), rapid DNA synthesis and late effects on cell growth. These results introduced a new mechanism for Shp2 oncogenic action and shed new light on extranuclear ER-initiated action in breast tumorigenesis by identifying a novel associated protein, Shp2, for extranuclear ER pathway, which might benefit the therapy of breast cancer.

Structure and backbone dynamics of vanadate-bound PRL-3: comparison of 15N nuclear magnetic resonance relaxation profiles of free and vanadate-bound PRL-3

Phosphatases of regenerating liver (PRLs) constitute a novel class of small, prenylated phosphatases with oncogenic activity. PRL-3 is particularly important in cancer metastasis and represents a potential therapeutic target. The flexibility of the WPD loop as well as the P-loop of protein tyrosine phosphatases is closely related to their catalytic activity. Using nuclear magnetic resonance spectroscopy, we studied the structure of vanadate-bound PRL-3, which was generated by addition of sodium orthovanadate to PRL-3. The WPD loop of free PRL-3 extended outside of the active site, forming an open conformation, whereas that of vanadate-bound PRL-3 was directed into the active site by a large movement, resulting in a closed conformation. We suggest that vanadate binding induced structural changes in the WPD loop, P-loop, helices α4-α6, and the polybasic region. Compared to free PRL-3, vanadate-bound PRL-3 has a longer α4 helix, where the catalytic R110 residue coordinates with vanadate in the active site. In addition, the hydrophobic cavity formed by helices α4-α6 with a depth of 14-15 Å can accommodate a farnesyl chain at the truncated prenylation motif of PRL-3, i.e., from R169 to M173. Conformational exchange data suggested that the WPD loop moves between open and closed conformations with a closing rate constant k(close) of 7 s(-1). This intrinsic loop flexibility of PRL-3 may be related to their catalytic rate and may play a role in substrate recognition.

Protein tyrosine phosphatase receptor U (PTPRU) is required for glioma growth and motility

The membrane protein tyrosine phosphatase receptor U (PTPRU) has been shown to function as a negative regulator of adhesion and proliferation in certain cancer cell types, primarily through its dephosphorylation of β-catenin and inhibition of subsequent downstream signaling. In the present study, we set out to characterize the role of PTPRU in glioma and found that, while the expression of full-length PTPRU protein is low in these tumors, a number of non-full-length PTPRU isoforms are highly expressed. Among these isoforms, one in particular is localized to the nucleus, and its expression is increased in glioma tissues in a manner that positively correlates with malignancy grade. Short hairpin RNA knockdown of endogenous PTPRU in human and rat glioma cell lines suppressed proliferation, survival, invasion, migration, adhesion and vasculogenic tube formation in vitro, as well as intracranial tumor progression in vivo. In addition, knocking down PTPRU reduced tyrosine phosphorylation (pY) and transcriptional activity of β-catenin, and we were able to specifically rescue the cell migration defect by expressing a LEF1-β-catenin fusion protein in PTPRU-depleted cells. PTPRU knockdown also led to increased tyrosine pY of the E3 ubiquitin ligase c-Cbl and to the destabilization of several focal adhesion proteins. Taken together, our findings demonstrate that endogenous PTPRU promote glioma progression through their effect on β-catenin and focal adhesion signaling.

Metabolic regulation by protein tyrosine phosphatases

Obesity and the metabolic syndrome and their associated morbidities are major public health issues, whose prevalence will continue to increase in the foreseeable future. Aberrant signaling by the receptors for leptin and insulin plays a pivotal role in development of the metabolic syndrome. More complete molecular-level understanding of how both of these key signaling pathways are regulated is essential for full characterization of obesity, the metabolic syndrome, and type II diabetes, and for developing novel treatments for these diseases. Phosphorylation of proteins on tyrosine residues plays a key role in mediating the effects of leptin and insulin on their target cells. Here, we discuss the molecular methods by which protein tyrosine phosphatases, which are key physiological regulators of protein phosphorylation in vivo, affect signaling by the leptin and insulin receptors in their major target tissues.

Antitumor activity of (R,R')-4-methoxy-1-naphthylfenoterol in a rat C6 glioma xenograft model in the mouse

(R,R’)-4-methoxy-1-naphthylfenoterol (MNF) inhibits cancer cell proliferation in vitro through cell-type specific modulation of β2-adrenergic receptor and/or cannabinoid receptor function. Here, we report an investigation into antitumor activity of MNF in rat C6 glioma cells. The potent antiproliferative action of MNF in these cells (IC₅₀ of ∼1 nmol/L) was refractory to pharmacological inhibition of β2-adrenergic receptor while a synthetic inverse agonist of cannabinoid receptor 1 significantly blocked MNF activity. The antitumor activity of MNF was then assessed in a C6 glioblastoma xenograft model in mice. Three days after subcutaneous implantation of C6 cells into the lower flank of nude mice, these animals were subjected to i.p. injections of saline or MNF (2 mg/kg) for 19 days and tumor volumes were measured over the course of the experiment. Gene expression analysis, quantitative RT-PCR and immunoblot assays were performed on the tumors after treatment. Significant reduction in mean tumor volumes was observed in mice receiving MNF when compared with the saline-treated group. We identified clusters in expression of genes involved in cellular proliferation, as well as molecular markers for glioblastoma that were significantly downregulated in tumors of MNF-treated mice as compared to saline-injected controls. The efficacy of MNF against C6 glioma cell proliferation in vivo and in vitro was accompanied by marked reduction in the expression of cell cycle regulator proteins. This study is the first demonstration of MNF-dependent chemoprevention of a glioblastoma xenograft model and may offer a potential mechanism for its anticancer action in vivo.

Preclinical evaluation of dipotassium bisperoxo (picolinato) oxovanadate V for the treatment of pediatric low-grade gliomas

AIM

The treatment of pediatric low-grade gliomas with current treatment modalities still remains ineffective among a subset of patients; hence, justifying the need to further investigate more effective therapies. Dipotassium bisperoxo (picolinato) oxovanadate V (Bpv[pic]), is a derivative of the trace metal vanadium and a potent inhibitor of protein tyrosine phosphatases, which are important mediators of oncogenic and tumor suppressive activities in cancers. In this study, we undertook a preclinical evaluation of the antineoplastic functions of Bpv(pic) in the treatment of pediatric low-grade gliomas.

MATERIALS & METHODS

We utilized pediatric low-grade glioma cell lines (Res186, Res259 and R286) in a wide variety of cancer assays to determine whether Bpv(pic) can abrogate the neoplastic properties of these cells.

RESULTS

Our preclinical evaluation of the antineoplastic properties of Bpv(pic) in pediatric low-grade gliomas reveals a significant dose-dependent decrease in cell viability as a consequence of decreased proliferation and sustained induction of growth arrest and apoptosis. Bpv(pic) significantly decreases cell migration/invasion and anchorage-independent growth in soft agarose. Within cells, Bpv(pic) functions by attenuating CDC25A activity, and by decreasing the expression of multiple protein tyrosine phosphatases, DNA repair genes, microtubule-associated genes, such as PLK1, AURKA and HDAC6, and conversely augmenting the expression of proapoptotic mediators such as BAK, AIFM and CTSL1.

CONCLUSION

Collectively, our data strongly suggest novel evidence of Bpv(pic) being a potent antineoplastic drug and a suitable alternative for the treatment of pediatric low-grade gliomas.

Src homology 2-containing protein tyrosine phosphatase-2 acts as a negative regulator for MUC5AC transcription via the inhibition of the ERK1/2 MAPK signalling pathway in the airway

AIMS

Mucus hypersecretion has been frequently observed in inflammation respiratory diseases. However, the negative regulators for mucus overproduction have not been readily identified. Our work focused on identifying novel negative regulator that modulates mucus overproduction in the human respiratory system. Herein, we examined whether H2 O2 could induce MUC5AC transcription in a dose-dependent manner and activate tyrosine phosphatase (SHP)-2 in human airway epithelial cells.

METHODS

We performed qRT-PCR to detect the changes in MUC5AC transcription and dot-blotting analysis to investigate MUC5AC secretion as regulated by SHP-2.

RESULTS

H2 O2 induced MUC5AC transcription in a dose-dependent manner and dramatically activated SHP-2. In addition, whereas wild-type SHP-2 completely inhibited H2 O2 -induced MUC5AC transcription, siRNA-SHP-2 restored it interestingly, suggesting that SHP-2 may act as a negative regulator for mucus overproduction and hypersecretion in the human respiratory tract. Moreover, SHP-2 inhibited the ERK1/2 MAPK pathway, thus abolishing the signalling for MUC5AC transcription.

CONCLUSION

We found that H2 O2 induced SHP-2 activation, which acted as a suppressor in H2 O2 signalling to regulate MUC5AC transcription in the airway.

Protein tyrosine phosphatase variants in human hereditary disorders and disease susceptibilities

Reversible tyrosine phosphorylation of proteins is a key regulatory mechanism to steer normal development and physiological functioning of multicellular organisms. Phosphotyrosine dephosphorylation is exerted by members of the super-family of protein tyrosine phosphatase (PTP) enzymes and many play such essential roles that a wide variety of hereditary disorders and disease susceptibilities in man are caused by PTP alleles. More than two decades of PTP research has resulted in a collection of PTP genetic variants with corresponding consequences at the molecular, cellular and physiological level. Here we present a comprehensive overview of these PTP gene variants that have been linked to disease states in man. Although the findings have direct bearing for disease diagnostics and for research on disease etiology, more work is necessary to translate this into therapies that alleviate the burden of these hereditary disorders and disease susceptibilities in man.

Signaling mechanisms regulating myelination in the central nervous system

The precise and coordinated production of myelin is essential for proper development and function of the nervous system. Diseases that disrupt myelin, including multiple sclerosis, cause significant functional disability. Current treatment aims to reduce the inflammatory component of the disease, thereby preventing damage resulting from demyelination. However, therapies are not yet available to improve natural repair processes after damage has already occurred. A thorough understanding of the signaling mechanisms that regulate myelin generation will improve our ability to enhance repair. in this review, we summarize the positive and negative regulators of myelination, focusing primarily on central nervous system myelination. Axon-derived signals, extracellular signals from both diffusible factors and the extracellular matrix, and intracellular signaling pathways within myelinating oligodendrocytes are discussed. Much is known about the positive regulators that drive myelination, while less is known about the negative regulators that shift active myelination to myelin maintenance at the appropriate time. Therefore, we also provide new data on potential negative regulators of CNS myelination.

Emerging role of tyrosine phosphatase, TCPTP, in the organelles of the early secretory pathway

T-cell protein tyrosine phosphatase, TCPTP, is a ubiquitously expressed non-receptor type tyrosine phosphatase. There are two splice variants of TCPTP, TC48 and TC45, which differ in their sub-cellular localizations and functions. TC45 is a nuclear protein, which has both nuclear and cytoplasmic substrates, and is involved in many signaling events including endocytic recycling of platelet-derived growth factor β-receptor. TC48 is a predominantly endoplasmic reticulum (ER)-localizing protein, which dephosphorylates some of the substrates of TC45 at the ER. However, recently few specific substrates for TC48 have been identified. These include C3G (RapGEF1), syntaxin 17 and BCR-Abl. TC48 moves from the ER to post-ER compartments, the ER-Golgi intermediate compartment (ERGIC) and Golgi, and it is retrieved back to the ER. The retrieval of ER proteins from post-ER compartments is generally believed as a mechanism of targeting these proteins to the ER. However, it is possible that this shuttling of TC48 serves to regulate signaling in the early secretory pathway. For example, TC48 dephosphorylates phosphorylated C3G at the Golgi and inhibits neurite outgrowth. TC48 interacts with and dephosphorylates syntaxin 17, which is an ER and ERGIC-localizing protein involved in vesicle transport. A yeast two-hybrid screen identified several unique interacting partners of TC48 belonging to two groups - proteins involved in vesicle trafficking and proteins involved in cell adhesion. These interacting proteins could be substrates or regulators of TC48 function and localization. Thus, the role of TC48 seems to be more diverse, which is still to be explored.

Shp2 plays an important role in acute cigarette smoke-mediated lung inflammation

Cigarette smoke (CS), the major cause of chronic obstructive pulmonary disease, contains a variety of oxidative components that were implicated in the regulation of Src homology domain 2-containing protein tyrosine phosphatase 2 (Shp2) activity. However, the contribution of Shp2 enzyme to chronic obstructive pulmonary disease pathogenesis remains unclear. We investigated the role of Shp2 enzyme in blockading CS-induced pulmonary inflammation. Shp2 levels were assessed in vivo and in vitro. Mice (C57BL/6) or pulmonary epithelial cells (NCI-H292) were exposed to CS or cigarette smoke extract (CSE) to induce acute injury and inflammation. Lungs of smoking mice showed increased levels of Shp2, compared with those of controls. Treatment of lung epithelial cells with CSE showed elevated levels of Shp2 associated with the increased release of IL-8. Selective inhibition or knockdown of Shp2 resulted in decreased IL-8 release in response to CSE treatment in pulmonary epithelial cells. In comparison with CS-exposed wild-type mice, selective inhibition or conditional knockout of Shp2 in lung epithelia reduced IL-8 release and pulmonary inflammation in CS-exposed mice. In vitro biochemical data correlate CSE-mediated IL-8 release with Shp2-regulated epidermal growth factor receptor/Grb-2-associated binders/MAPK signaling. Our data suggest an important role for Shp2 in the pathological alteration associated with CS-mediated inflammation. Shp2 may be a potential target for therapeutic intervention for inflammation in CS-induced pulmonary diseases.

Protein tyrosine phosphatase mu regulates glioblastoma cell growth and survival in vivo

Glioblastoma multiforme (GBM) is the most lethal primary brain tumor. Extensive proliferation and dispersal of GBM tumor cells within the brain limits patient survival to approximately 1 year. Hence, there is a great need for the development of better means to treat GBM. Receptor protein tyrosine phosphatase (PTP)µ is proteolytically cleaved in GBM to yield fragments that promote dispersal of GBM cells. While normal brain tissue retains expression of full-length PTPµ, low-grade human astrocytoma samples have varying amounts of full-length PTPµ and cleaved PTPµ. In the highest-grade astrocytomas (i.e., GBM), PTPµ is completely proteolyzed into fragments. We demonstrate that short hairpin RNA mediated knockdown of full-length PTPµ and PTPµ fragments reduces glioma cell growth and survival in vitro. The reduction in growth and survival following PTPµ knockdown is enhanced when cells are grown in the absence of serum, suggesting that PTPµ may regulate autocrine signaling. Furthermore, we show for the first time that reduction of PTPµ protein expression decreases the growth and survival of glioma cells in vivo using mouse xenograft flank and i.c. tumor models. Inhibitors of PTPµ could be used to reduce the growth and survival of GBM cells in the brain, representing a promising therapeutic target for GBM.

CpG array analysis of histone H3 lysine 4 trimethylation by chromatin immunoprecipitation linked to microarrays analysis in peripheral blood mononuclear cells of IgA nephropathy patients

PURPOSE

The purpose of the present study was to investigate the aberrance of histone H3 lysine 4 trimethylation (H3K4me3) in patients with IgA Nephropathy (IgAN).

MATERIALS AND METHODS

In this study, H3K4me3 variations in peripheral blood mononuclear cells (PBMCs) from 15 IgAN patients and 15 healthy subjects were analyzed using chromatin immunoprecipitation linked to microarrays analysis (ChIP-chip). ChIP real-time PCR was used to validate the microarray results. Expression analysis by quantitative real-time PCR (qRT-PCR) revealed correlations between mRNA and H3K4me3 levels. DNA methylation status was analyzed by quantitative methylation-specific PCR.

RESULTS

We found that 321 probes displayed significant H3K4me3 differences in IgAN patients compared with healthy controls. Among these probes, 154 probes displayed increased H3K4me3 and 167 probes demonstrated decreased H3K4me3. For further validation, we selected 4 key relevant genes (FCRL4, GALK2, PTPRN2 and IL1RAPL1) to study. The results of ChIP real-time PCR coincided well with the microarray data. Quantitative RT-PCR revealed the correlations between the mRNA expression and the methylation levels of H3K4me3. Different degrees of DNA methylation alterations appeared on the selected positive genes.

CONCLUSION

Our studies indicated that there were significant alterations in H3K4me3 in IgAN patients. These findings may help to explain the disturbed immunity and abnormal glycosylation involved in IgAN patients.

Tissue-specific alterations of PRL-1 and PRL-2 expression in cancer

The PRL-1 and PRL-2 phosphatases have been implicated as oncogenic, however the involvement of these molecules in human neoplasms is not well understood. To increase understanding of the role PRL-1 and PRL-2 play in the neoplastic process, in situ hybridization was used to examine PRL-1 and PRL-2 mRNA expression in 285 normal, benign, and malignant human tissues of diverse origin. Immunohistochemical analysis was performed on a subset of these. PRL-1 and PRL-2 mRNA expression was also assessed in a small set of samples from a variety of diseases other than cancer. Where possible, associations with clinicopathological characteristics were evaluated. Alterations in PRL-1 or -2 expression were a frequent event, but the nature of those alterations was highly tumor type specific. PRL-1 was significantly overexpressed in 100% of hepatocellular and gastric carcinomas, but significantly under-expressed in 100% of ovarian, 80% of breast, and 75% of lung tumors. PRL-2 expression was significantly increased in 100% of hepatocellular carcinomas, yet significantly downregulated in 54% of kidney carcinomas. PRL-1 expression was correlated to patient gender in the bladder and to patient age in the brain and skeletal muscle. PRL-1 expression was also associated with tumor grade in the prostate, ovary, and uterus. These results suggest a pleiotropic role for PRL-1 and PRL-2 in the neoplastic process. These molecules may associate with tumor progression and serve as clinical markers of tumor aggressiveness in some tissues, but be involved in inhibition of tumor formation or growth in others.

Dynamin 2 mediates PDGFRα-SHP-2-promoted glioblastoma growth and invasion

Dynamin 2 (Dyn2), a large GTPase, is involved in receptor tyrosine kinase (RTK)-promoted cell migration. However, molecular mechanisms by which Dyn2 regulates RTK-induced cell migration have not been established. Recently we reported that SHP-2 and PI3K mediate PDGFRα-promoted glioma tumor growth and invasion. Here, we show that Dyn2 is an effector downstream of the PDGFRα-PI3K/SHP-2 signaling in glioma cells. Depletion of endogenous Dyn2 by shRNAs inhibited PDGFRα-stimulated phosphorylation of Akt, Erk1/2, Rac1 and Cdc42 activities, glioma cell migration and survival in vitro, tumor growth and invasion in the brains of mice. Dyn2 binds to SHP-2, PI3K and co-localizes with PDGFRα at the invasive fronts in PDGF-A-stimulated glioma cells. Inhibition of SHP-2 by siRNA knockdown abrogated Dyn2 association with activated PDGFRα and PDGFRα activation of Rac1 and Cdc42, glioma cell migration, thereby establishing a link between SHP-2 interaction with Dyn2 and the PDGFRα signaling. Furthermore, a dominant negative SHP-2 C459S mutant inhibited PDGF-A-stimulated glioma cell migration, phosphorylation of Dyn2 and concomitantly blocked PDGFRα-induced Src activation. Inhibition of Src by Src inhibitors attenuated PDGF-A-stimulated phosphorylation of Akt and Dyn2 and glioma cell migration. Additionally, mutations of binding sites to PI3K, SHP-2 or Src of PDGFRα impaired PDGFRα-stimulated phosphorylation of Akt and Dyn2, and Dyn2 association with activated PDGFRα. Taken together, this study identifies Dyn2 as an effector that mediates PDGFRα-SHP-2-induced glioma tumor growth and invasion, suggesting that targeting the PDGFRα-SHP-2-Dyn2 pathway may be beneficial to patients with malignant glioblastomas.

DNA methylation changes in atypical adenomatous hyperplasia, adenocarcinoma in situ, and lung adenocarcinoma

BACKGROUND

Aberrant DNA methylation is common in lung adenocarcinoma, but its timing in the phases of tumor development is largely unknown. Delineating when abnormal DNA methylation arises may provide insight into the natural history of lung adenocarcinoma and the role that DNA methylation alterations play in tumor formation.

METHODOLOGY/PRINCIPAL FINDINGS

We used MethyLight, a sensitive real-time PCR-based quantitative method, to analyze DNA methylation levels at 15 CpG islands that are frequently methylated in lung adenocarcinoma and that we had flagged as potential markers for non-invasive detection. We also used two repeat probes as indicators of global DNA hypomethylation. We examined DNA methylation in 249 tissue samples from 93 subjects, spanning the putative spectrum of peripheral lung adenocarcinoma development: histologically normal adjacent non-tumor lung, atypical adenomatous hyperplasia (AAH), adenocarcinoma in situ (AIS, formerly known as bronchioloalveolar carcinoma), and invasive lung adenocarcinoma. Comparison of DNA methylation levels between the lesion types suggests that DNA hypermethylation of distinct loci occurs at different time points during the development of lung adenocarcinoma. DNA methylation at CDKN2A ex2 and PTPRN2 is already significantly elevated in AAH, while CpG islands at 2C35, EYA4, HOXA1, HOXA11, NEUROD1, NEUROD2 and TMEFF2 are significantly hypermethylated in AIS. In contrast, hypermethylation at CDH13, CDX2, OPCML, RASSF1, SFRP1 and TWIST1 and global DNA hypomethylation appear to be present predominantly in invasive cancer.

CONCLUSIONS/SIGNIFICANCE

The gradual increase in DNA methylation seen for numerous loci in progressively more transformed lesions supports the model in which AAH and AIS are sequential stages in the development of lung adenocarcinoma. The demarcation of DNA methylation changes characteristic for AAH, AIS and adenocarcinoma begins to lay out a possible roadmap for aberrant DNA methylation events in tumor development. In addition, it identifies which DNA methylation changes might be used as molecular markers for the detection of preinvasive lesions.