Phosphatase PTP1B Research Articles

Azaphilones with protein tyrosine phosphatase inhibitory activity isolated from the fungus Aspergillus deflectus

Six undescribed azaphilones, deflectins C1-C3, deflectins D1-D2, and deflectin E, along with five known azaphilones were obtained from a solid culture of the wild fungus Aspergillus deflectus NCC0415. Their structures were determined by HRESIMS, NMR and ECD analyses, together with the GIAO 13C NMR calculation method. All compounds displayed strong or moderate inhibitory activity against protein tyrosine phosphatases SHP2 and PTP1B. Structure-activity relationship analysis of these azaphilones suggested that the length of the ketone aliphatic side chain would affect their SHP2 and PTP1B inhibitory activity. In addition, the presence of a Δ8(12) double bond on γ-lactone ring and the presence of CH3-2’ in fatty chains may increase their inhibitory activity.

PTP1B phosphatase as a novel target of oleuropein activity in MCF-7 breast cancer model

Phosphatase PTP1B has become a therapeutic target for the treatment of type 2-diabetes, whereas recent studies have revealed that PTP1B plays a pivotal role in pathophysiology and development of breast cancer. Oleuropein is a natural, phenolic compound with anticancer activity. The aim of this study was to address the question whether PTP1B constitutes a target for oleuropein in breast cancer MCF-7 cells.The cellular MCF-7 breast cancer model was used in the study. The experiments were performed using cellular viability tests, Elisa assays, immunoprecipitation, flow cytometry analyses and computer modelling.Herein, we evidenced that the reduced activity of phosphatase PTP1B after treatment with oleuropein is strictly correlated with decreased MCF-7 cellular viability and cell cycle arrest. These results provide new insight into further research on oleuropein and possible role of the compound in adjuvant treatment of breast cancer.

Inhibitors of Protein Tyrosine Phosphatase PTP1B With Anticancer Potential.

PTP1B tyrosine phosphatase is involved in the development of many types of cancers, such as breast cancer or lung cancer. Therefore, PTP1B is a promising target for anticancer therapy. The purpose of this review was to present the studies on selected PTP1B inhibitors as a possible treatment and describe the latest trends of current research in this field. This literature review was performed using the PubMed database and the analysis of previous research studies of our Department. Recent studies have shown that PTP1B, due to its implication in oncogenic transformation, represents a promising drug target. The selected compounds that are effective PTP1B inhibitors can be considered a promising anticancer treatment, both as monotherapy and in combination with other anticancer drugs.

Spatial proteomics reveal that the protein phosphatase PTP1B interacts with and may modify tyrosine phosphorylation of the rhomboid protease RHBDL4

Rhomboid-like proteins are evolutionarily conserved, ubiquitous polytopic membrane proteins, including the canonical rhomboid intramembrane serine proteases and also others that have lost protease activity during evolution. We still have much to learn about their cellular roles, and evidence suggests that some may have more than one function. For example, RHBDL4 (rhomboid-like protein 4) is an endoplasmic reticulum (ER)–resident protease that forms a ternary complex with ubiquitinated substrates and p97/VCP (valosin-containing protein), a major driver of ER-associated degradation (ERAD). RHBDL4 is required for ERAD of some substrates, such as the pre–T-cell receptor α chain (pTα) and has also been shown to cleave amyloid precursor protein to trigger its secretion. In another case, RHBDL4 enables the release of full-length transforming growth factor α in exosomes. Using the proximity proteomic method BioID, here we screened for proteins that interact with or are in close proximity to RHBDL4. Bioinformatics analyses revealed that BioID hits of RHBDL4 overlap with factors related to protein stress at the ER, including proteins that interact with p97/VCP. PTP1B (protein-tyrosine phosphatase nonreceptor type 1, also called PTPN1) was also identified as a potential proximity factor and interactor of RHBDL4. Analysis of RHBDL4 peptides highlighted the presence of tyrosine phosphorylation at the cytoplasmic RHBDL4 C terminus. Site-directed mutagenesis targeting these tyrosine residues revealed that their phosphorylation modifies binding of RHBDL4 to p97/VCP and Lys63-linked ubiquitinated proteins. Our work lays a critical foundation for future mechanistic studies of the roles of RHBDL4 in ERAD and other important cellular pathways.

Targeting pancreatic islet PTP1B improves islet graft revascularization and transplant outcomes.

Deficient vascularization is a major driver of early islet graft loss and one of the primary reasons for the failure of islet transplantation as a viable treatment for type 1 diabetes. This study identifies the protein tyrosine phosphatase 1B (PTP1B) as a potential modulator of islet graft revascularization. We demonstrate that grafts of pancreatic islets lacking PTP1B exhibit increased revascularization, which is accompanied by improved graft survival and function, and recovery of normoglycemia and glucose tolerance in diabetic mice transplanted with PTP1B-deficient islets. Mechanistically, we show that the absence of PTP1B leads to activation of hypoxia-inducible factor 1α-independent peroxisome proliferator-activated receptor γ coactivator 1α/estrogen-related receptor α signaling and enhanced expression and production of vascular endothelial growth factor A (VEGF-A) by β cells. These observations were reproduced in human islets. Together, these findings reveal that PTP1B regulates islet VEGF-A production and suggest that this phosphatase could be targeted to improve islet transplantation outcomes.

Crosstalks of the PTPIP51 interactome revealed in Her2 amplified breast cancer cells by the novel small molecule LDC3/Dynarrestin.

LDC3/Dynarrestin, an aminothiazole derivative, is a recently developed small molecule, which binds protein tyrosine phosphatase interacting protein 51 (PTPIP51). PTPIP51 interacts with various proteins regulating different signaling pathways leading to proliferation and migration. Her2 positive breast cancer cells (SKBR3) express high levels of PTPIP51. Therefore, we investigated the effects of LDC3/Dynarrestin on PTPIP51 and its interactome with 12 different proteins of various signal pathways including the interaction with dynein in SKBR3 cells. The localization and semi-quantification of PTPIP51 protein and the Tyr176 phosphorylated PTPIP51 protein were evaluated. Protein-protein-interactions were assessed by Duolink proximity ligation assays. Interactions and the activation of signal transduction hubs were examined with immunoblots. LDC3/Dynarrestin led to an increased PTPIP51 tyrosine 176 phosphorylation status while the overall amount of PTPIP51 remained unaffected. These findings are paralleled by an enhanced interaction of PTPIP51 with its crucial kinase c-Src and a reduced interaction with the counteracting phosphatase PTP1B. Furthermore, the treatment results in a significantly augmented interaction of PTPIP51/14-3-3β and PTPIP51/Raf1, the link to the MAPK pathway. Under the influence of LDC3/Dynarrestin, the activity of the MAPK pathway rose in a concentration-dependent manner as indicated by RTK assays and immunoblots. The novel small molecule stabilizes the RelA/IκB/PTPIP51 interactome and can abolish the effects caused by TNFα stimulation. Moreover, LDC3/Dynarrestin completely blocked the Akt signaling, which is essential for tumor growth. The data were compared to the recently described interactome of PTPIP51 in LDC3/Dynarrestin treated non-cancerous keratinocyte cells (HaCaT). Differences were identified exclusively for the mitochondrial-associated ER-membranes (MAM) interactions and phospho-regulation related interactome of PTPIP51.LDC3/Dynarrestin gives the opportunity/possibility to influence the MAPK signaling, NFkB signaling and probably calcium homeostasis in breast cancer cells by affecting the PTPIP51 interactome.

Sec14l3 potentiates VEGFR2 signaling to regulate zebrafish vasculogenesis

Vascular endothelial growth factor (VEGF) regulates vasculogenesis by using its tyrosine kinase receptors. However, little is known about whether Sec14-like phosphatidylinositol transfer proteins (PTP) are involved in this process. Here, we show that zebrafish sec14l3, one of the family members, specifically participates in artery and vein formation via regulating angioblasts and subsequent venous progenitors’ migration during vasculogenesis. Vascular defects caused by sec14l3 depletion are partially rescued by restoration of VEGFR2 signaling at the receptor or downstream effector level. Biochemical analyses show that Sec14l3/SEC14L2 physically bind to VEGFR2 and prevent it from dephosphorylation specifically at the Y1175 site by peri-membrane tyrosine phosphatase PTP1B, therefore potentiating VEGFR2 signaling activation. Meanwhile, Sec14l3 and SEC14L2 interact with RAB5A/4A and facilitate the formation of their GTP-bound states, which might be critical for VEGFR2 endocytic trafficking. Thus, we conclude that Sec14l3 controls vasculogenesis in zebrafish via the regulation of VEGFR2 activation.

Abstract B035: Enhancing antitumoral activity of cell-based immunotherapies by modulating the JAK-STAT axis

Abstract Mounting a T helper 1 (Th1) type of response is required for the successful priming of antigen specific CD8 T-cells which ultimately lead to effective antitumoral responses. Several cellular components of the immune system participate of the Th1 decision-making process. They include innate cells sensing the transformed cells, mainly dendritic cells (DCs), and the further involvement of antigen specific CD4 T-cells promoting direct activation of CD8 T-cells through cross-presentation (1). The correct stimulation of DCs by type I interferons and molecular pattern sensors as STING is required to drive their differentiation to conventional DC 1 (cDC1) which through the secretion of large amounts of IL-12 and the expression of CD40 skew the CD4 T-cells differentiation to Th1 (2). However, this system is sensitive to modifications of the tumor cytokine microenvironmen,t leading to failure. Adoptive cell transfer (ACT) cancer immunotherapies are promising treatments for advanced malignancies. These therapies attempt to supply key cellular actors missing and induce proper antitumoral immunity. They include mainly the in vitro modification of autologous cells, from DCs loaded with tumor antigens to the expression of chimeric antigen receptor (CAR) on T and NK cells. Constant development of these technologies has given successful results as clinical trials have already showed up to 90 % of complete remission in relapsed/refractory B cell acute lymphoid leukemia (B-ALL) (3), treatment now approved for commercial use. However, there is still lack of consistency in the responses obtained from different individuals and in different trials. Previously our laboratory has already shown that modulation of the JAK-STAT inhibitory protein tyrosine phosphatases (PTPs), PTPN1 and PTP-N2, enhance proinflammatory type I interferon signalling while decreases the effects of immunosuppressive cytokines acting through STAT3 signaling (4, 5). Specifically, we have demonstrated that partial inhibition of these phosphatases in immune cells enhances the secretion of IL-12p70 by DCs[6] and increases the cytotoxic activity of antigen specific CD8 T-cells [Pérez-Quintero LA, Tremblay ML, unpublished results]. Moreover, the partial inhibition of these phosphatases in CD8 T-cells enhance the acquisition of a central memory (Tcm) phenotype, which has been found to be associated with better remission in CAR-T-cells therapies. Nevertheless, alternative methods to enrich this phenotype, as cytokine cocktails, have proven expensive and ineffective. Having this in mind, we propose here the use of small-molecule inhibitors specific for PTPN1 and PTPN2 as a simple and cost-effective method to enhance antitumoral responses. By treating ex vivo the cellular products in animal models for DCs and CD8 ACT therapies we show, as a proof of concept, a marked improvement on the reduction of tumor burden and remission, with the late goal of translating these findings into a clinical setup.

Leptin Signaling in the Arcuate Nucleus Reduces Insulin’s Capacity to Suppress Hepatic Glucose Production in Obese Mice

Insulin action in the hypothalamus results in the suppression of hepatic glucose production (HGP). Obesity is often associated with a diminished response to insulin, leading to impaired suppression of HGP in obese mice. Here, we demonstrate that blocking central leptin signaling in diet-induced obese (DIO) mice restores the liver's ability to suppress glucose production. Leptin increases the expression of the insulin receptor phosphatase PTP1B, which is highly expressed in the hypothalamus of DIO mice. We demonstrate that the central pharmacological inhibition or ARH-targeted deletionof PTP1B restores the suppression of HGP in obese mice. Additionally, mice that lack PTP1B inAgRP neurons exhibit enhanced ARH insulin signaling andhave improved glucose tolerance and insulinsensitivity. Overall, our findings indicate thatobesity-induced increases in PTP1B diminish insulin action in the hypothalamus, resulting in unconstrained HGP and contributing to hyperglycemia in obesity.

PTP1B markedly promotes breast cancer progression and is regulated by miR-193a-3p.

The protein tyrosine phosphatase PTP1B, which is encoded by PTPN1, is a ubiquitously expressed nonreceptor protein tyrosine phosphatase. PTP1B has long been known to negatively regulate insulin and leptin receptor signalling. Recently, it was reported to be aberrantly expressed in cancer cells and to function as an important oncogene. In this study, we found that PTP1B protein levels are dramatically increased in breast cancer (BC) tissues and that PTP1B promotes the proliferation, and suppresses the apoptosis, of both HER2-positive and triple-negative BC cell lines. Bioinformatics analysis identified that the miRNA, miR-193a-3p, might potentially target PTP1B. We demonstrate that miR-193a-3p regulates PTP1B in BC cells and that it regulates the proliferation and apoptosis of BC cells by targeting PTP1B, both in vitro and in vivo. In conclusion, this study confirms that PTP1B acts as an oncogene in BC and demonstrates that miR-193a-3p can serve as a tumour suppressor gene in BC by targeting PTP1B.

P9 - Plant Bioactives and the Intestinal Barrier: Redox Signaling and Implications for Insulin Resistance

Dietary plant bioactives, and in particular flavonoids, can exert actions at the gastrointestinal (GI) tract that can have an impact systemically, e.g. on glucose homeostasis, lipid and energy metabolism. GI barrier permeabilization and the associated increased passage to the circulation of luminal endotoxins underlie in part the pathophysiology of obesity-associated pathologies, including insulin resistance and type 2 diabetes. Endotoxins trigger systemic pro-inflammatory responses that contribute to tissue insulin resistance involving the activation of redox-regulated signals. Among flavonoids, we found that the flavan-3-ol (-)-epicatechin (EC) inhibits high fat (HFD)- and/or high fructose (HFr) diet-induced insulin resistance and steatosis in rodents. These beneficial effects are associated with EC capacity to inhibit HFD-mediated intestinal barrier permeabilization and endotoxemia. In vivo and in vitro studies support intestinal cell NADPH oxidase as a major target involved in EC effects. NADPH oxidase triggers a downstream series of events that cause tight junction disruption: NF-kB and ERK1/2 activation, upregulation of myosin light chain (MLC) kinase, leading to MLC phosphorylation and consequent monolayer permeabilization. Modulation of NADPH oxidase is also involved in the capacity of EC to restore insulin sensitivity in liver and adipose tissues, given that the redox-regulated activation of IKK/NF-kB, JNK1/2 and PKC causes inhibitory serine phosphorylation of the insulin receptor (IR) substrate 1 (IRS1), and upregulation of the IR and IRS1 inhibitory tyrosine phosphatase PTP1B. EC and other structurally related flavonoids (i.e. anthocyanidins (AC)) that directly inhibit NADPH oxidase, share similar chemical structures and capacity to improve insulin sensitivity. Furthermore, inhibition of NF-kB can explain EC-mediated decreased expression of select NADPH isoforms. In summary, the capacity of select bioactives (EC, AC) to improve HFD/HFR-associated insulin resistance is in part mediated through their capacity to modulate NADPH oxidase and redox-regulated pathways, leading to loss of GI tract barrier integrity and downregulation of the insulin pathway.

Thioredoxin-related protein of 14kDa as a modulator of redox signalling pathways.

Thioredoxin-related protein of 14kDa (TRP14; also named TXNDC17 for thioredoxin domain-containing protein 17) is a highly conserved and ubiquitously expressed oxidoreductase. It is expressed in parallel with thioredoxin 1 (Trx1, TXN; TXN1), an efficient substrate for the mammalian cytosolic selenoprotein thioredoxin reductase 1 (TrxR1; TXNRD1). However, TRP14, in sharp contrast to Trx1, cannot support the activities of ribonucleotide reductase, peroxiredoxins or methionine sulfoxide reductases, thus is unable to directly support cell proliferation or antioxidant defence through these pathways. However, TRP14 has been shown to efficiently reduce l-cystine, which thereby indirectly supports glutathione synthesis. TRP14 can also suppress NF-κB signalling, is functionally linked to STAT3 signalling, and can directly reactivate oxidized protein-tyrosine phosphatase PTP1B. Furthermore, TRP14 can efficiently reduce persulfidated or nitrosylated cysteine residues in many proteins, thereby having the capacity to modulate signalling through hydrogen sulfide or NO. Additional bioinformatics analyses and observations suggest further roles for TRP14; therefore, further studies of its functions are warranted. Collectively, the results available suggest that TRP14 is a member of the thioredoxin system dedicated to the control of cellular redox signalling pathways. LINKED ARTICLES: This article is part of a themed section on Chemical Biology of Reactive Sulfur Species. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.4/issuetoc.

4-oxo-1,4-dihydrocinnoline Derivative with Phosphatase 1B Inhibitor Activity Enhances Leptin Signal Transduction in Hypothalamic Neurons

Most of regulatory effects of leptin on feeding behavior and energy metabolism are implemented via the hypothalamic leptin system. Attenuation of its activity leads to hyperphagia, obesity and other metabolic disorders. To prevent these pathological conditions, it is necessary to develop approaches aimed at restoring the leptin system. Most promising of them is creating efficient inhibitors of protein phosphotyrosine phosphatase PTP1B, a negative regulator of leptin signaling. The aim of this work was to synthesize a new compound, ethyl-3-(hydroxymethyl)-4-oxo-1,4-dihydrocinnoline-6-carboxylate (PI-04), a 4-oxo-1,4-dihydrocinnoline derivative with a PTP1B inhibitor activity, and to study its effect on IRS2- and STAT3-dependent leptin pathways in culture of hypothalamic neurons isolated from 18-day-old rat embryos. It was shown that PI-04 enhances the stimulatory effect of leptin on phosphorylation of the IRS2 protein at the Ser731 residue and of the STAT3 transcriptional factor at the Tyr705 residue, suggesting a potentiation of functional responses of hypothalamic neurons to leptin in the presence of this compound. The potentiating effect of PI-04 on leptin signaling was implemented at micromolar concentrations when this substance had virtually no effect on neuronal survival. The data obtained are promising in terms of creating phosphatase PTP1B inhibitors based on 4-oxo-1,4-dihydrocinnoline, as well as the possibility of their further use to prevent and correct metabolic disorders caused by attenuated activity of the hypothalamic leptin system.

Cyanidin and delphinidin modulate inflammation and altered redox signaling improving insulin resistance in high fat-fed mice

Consumption of diets high in fat and/or fructose content promotes tissue inflammation, oxidative stress, and insulin resistance, activating signals (e.g. NF-κB/JNK) that downregulate the insulin cascade. Current evidence supports the concept that select flavonoids can mitigate obesity and type 2 diabetes (T2D). This work investigated if supplementation with the anthocyanidins (AC) cyanidin and delphinidin could attenuate the adverse consequences of consuming a high fat diet (HFD) in mice. Consumption of an AC-rich blend mitigated HFD-induced obesity, dyslipidemia and insulin resistance (impaired responses to insulin and glucose). HFD-fed mice were characterized by increased liver lipid deposition and inflammation, which were also attenuated upon AC supplementation. HFD caused liver oxidative stress showing an increased expression of NADPH oxidases, generators of superoxide and H2O2, and high levels of oxidized lipid-protein adducts. This was associated with the activation of the redox sensitive signals IKK/NF-κB and JNK1/2, and increased expression of the NF-κB-regulated PTP1B phosphatase, all known inhibitors of the insulin pathway. In agreement with an improved insulin sensitivity, AC supplementation inhibited oxidative stress, NF-κB and JNK activation, and PTP1B overexpression. Thus, cyanidin and delphinidin consumption either through diet or by supplementation could be a positive strategy to control the adverse effects of Western style diets, including overweight, obesity, and T2D. Modulation of inflammation, oxidative stress, and NF-κB/JNK activation emerge as relevant targets of AC beneficial actions.

P-6 - Thioredoxin related protein of 14 kDa (TRP14, TXNDC17) represses Nrf2 and NFκB activities and augments HIF activation

Thioredoxin related protein of 14 kDa is a cytosolic protein of the thioredoxin fold family expressed in all tissues and an efficient substrate of the selenoprotein thioredoxin reductase 1. TRP14 cannot support classical Trx1 substrates such as peroxiredoxins, methionine sulfoxide reductases or ribonucleotide reductase, but affects NFκB signaling. However, it is efficient in reducing L-cystine and support S-denitrosylation reactions, reduce protein persulfides or reactivate oxidized protein tyrosine phosphatase PTP1B. These and other observations suggest that TRP14 may have dedicated roles in cellular signaling pathways, which was studied here. Using our previously developed pTRAF, we assessed activation patterns of the transcription factors Nrf2, NFκB and HIF in HEK293 cells with or without modulated TRP14 levels. Our preliminary results suggest that TRP14 is an unusual member of the Trx system, in that TRP14 may act as a repressor of NRF2, modulate HIF activation under hypoxia as well as acting as a weak repressor of NFκB activation. Further analyses are needed to fully evaluate the pTRAF readout also including additional methodologies Our results point towards the role of TRP14 as a dedicated fine-tuning modulator of redox regulated signaling pathways.

VSpipe, an Integrated Resource for Virtual Screening and Hit Selection: Applications to Protein Tyrosine Phospahatase Inhibition.

The use of computational tools for virtual screening provides a cost-efficient approach to select starting points for drug development. We have developed VSpipe, a user-friendly semi-automated pipeline for structure-based virtual screening. VSpipe uses the existing tools AutoDock and OpenBabel together with software developed in-house, to create an end-to-end virtual screening workflow ranging from the preparation of receptor and ligands to the visualisation of results. VSpipe is efficient and flexible, allowing the users to make choices at different steps, and it is amenable to use in both local and cluster mode. We have validated VSpipe using the human protein tyrosine phosphatase PTP1B as a case study. Using a combination of blind and targeted docking VSpipe identified both new and known functional ligand binding sites. Assessment of different binding clusters using the ligand efficiency plots created by VSpipe, defined a drug-like chemical space for development of PTP1B inhibitors with potential applications to other PTPs. In this study, we show that VSpipe can be deployed to identify and compare different modes of inhibition thus guiding the selection of initial hits for drug discovery.

A potent, selective, and orally bioavailable inhibitor of the protein-tyrosine phosphatase PTP1B improves insulin and leptin signaling in animal models

The protein-tyrosine phosphatase PTP1B is a negative regulator of insulin and leptin signaling and a highly validated therapeutic target for diabetes and obesity. Conventional approaches to drug development have produced potent and specific PTP1B inhibitors, but these inhibitors lack oral bioavailability, which limits their potential for drug development. Here, we report that DPM-1001, an analog of the specific PTP1B inhibitor trodusquemine (MSI-1436), is a potent, specific, and orally bioavailable inhibitor of PTP1B. DPM-1001 also chelates copper, which enhanced its potency as a PTP1B inhibitor. DPM-1001 displayed anti-diabetic properties that were associated with enhanced signaling through insulin and leptin receptors in animal models of diet-induced obesity. Therefore, DPM-1001 represents a proof of concept for a new approach to therapeutic intervention in diabetes and obesity. Although the PTPs have been considered undruggable, the findings of this study suggest that allosteric PTP inhibitors may help reinvigorate drug development efforts that focus on this important family of signal-transducing enzymes.

Harnessing insulin- and leptin-induced oxidation of PTP1B for therapeutic development

The protein tyrosine phosphatase PTP1B is a major regulator of glucose homeostasis and energy metabolism, and a validated target for therapeutic intervention in diabetes and obesity. Nevertheless, it is a challenging target for inhibitor development. Previously, we generated a recombinant antibody (scFv45) that recognizes selectively the oxidized, inactive conformation of PTP1B. Here, we provide a molecular basis for its interaction with reversibly oxidized PTP1B. Furthermore, we have identified a small molecule inhibitor that mimics the effects of scFv45. Our data provide proof-of-concept that stabilization of PTP1B in an inactive, oxidized conformation by small molecules can promote insulin and leptin signaling. This work illustrates a novel paradigm for inhibiting the signaling function of PTP1B that may be exploited for therapeutic intervention in diabetes and obesity.

Deficiency in Protein Tyrosine Phosphatase PTP1B Shortens Lifespan and Leads to Development of Acute Leukemia.

Protein tyrosine phosphatase PTP1B is a critical regulator of signaling pathways controlling metabolic homeostasis, cell proliferation, and immunity. In this study, we report that global or myeloid-specific deficiency of PTP1B in mice decreases lifespan. We demonstrate that myeloid-specific deficiency of PTP1B is sufficient to promote the development of acute myeloid leukemia. LysM-PTP1B-/- mice lacking PTP1B in the innate myeloid cell lineage displayed a dysregulation of bone marrow cells with a rapid decline in population at midlife and a concomitant increase in peripheral blood blast cells. This phenotype manifested further with extramedullary tumors, hepatic macrophage infiltration, and metabolic reprogramming, suggesting increased hepatic lipid metabolism prior to overt tumor development. Mechanistic investigations revealed an increase in anti-inflammatory M2 macrophage responses in liver and spleen, as associated with increased expression of arginase I and the cytokines IL10 and IL4. We also documented STAT3 hypersphosphorylation and signaling along with JAK-dependent upregulation of antiapoptotic proteins Bcl2 and BclXL. Our results establish a tumor suppressor role for PTP1B in the myeloid lineage cells, with evidence that its genetic inactivation in mice is sufficient to drive acute myeloid leukemia.Significance: This study defines a tumor suppressor function for the protein tyrosine phosphatase PTP1B in myeloid lineage cells, with evidence that its genetic inactivation in mice is sufficient to drive acute myeloid leukemia. Cancer Res; 78(1); 75-87. ©2017 AACR.

Inhibitory Activity of Iron Chelators ATA and DFO on MCF-7 Breast Cancer Cells and Phosphatases PTP1B and SHP2.

Rapidly-dividing cancer cells have higher requirement for iron compared to non-transformed cells, making iron chelating a potential anticancer strategy. In the present study we compared the anticancer activity of uncommon iron chelator aurintricarboxylic acid (ATA) with the known deferoxamine (DFO). We investigated the impact of ATA and DFO on the viability and proliferation of MCF-7 cancer cells. Moreover we performed enzymatic activity assays and computational analysis of the ATA and DFO effects on pro-oncogenic phosphatases PTP1B and SHP2. ATA and DFO decrease the viability and proliferation of breast cancer cells, but only ATA considerably reduces the activity of PTP1B and SHP2 phosphatases. Our studies indicated that ATA strongly inactivates and binds in the PTP1B and SHP2 active site, interacting with arginine residue essential for enzyme activity. We confirmed that iron chelating can be considered as a potential strategy for the adjunctive treatment of breast cancer.