Inhibition of the Gab2/PI3K/mTOR signaling ameliorates myeloid malignancy caused by Ptpn11 (Shp2) gain-of-function mutations

Natural Product-Inspired Molecules for Covalent Inhibition of SHP2 Tyrosine Phosphatase

Natural products have been playing indispensable roles in the development of lifesaving drug molecules. They are also valuable sources for covalent protein modifiers. However, they often are scarce in nature and have complex chemical structures, which are limiting their further biomedical development. Thus, natural product-inspired small molecules which still contain the essence of the parent natural products but are readily available and amenable for structural modification, are important and desirable in searching for lead compounds for various disease treatment. Inspired by the complex and diverse ent-kaurene diterpenoids with significant biological activities, we have created a synthetically accessible and focused covalent library by incorporating the bicyclo[3.2.1]octane α-methylene ketone, which is considered as the pharmacophore of ent-kaurene diterpenoids, as half of the structure, and replacing the other half with much less complex but more druglike scaffolds. From this library, we have identified and characterized selective covalent inhibitors of protein tyrosine phosphatase SHP2, an important anti-cancer therapeutic target. The success of this study demonstrated the importance of creating and evaluating natural product-inspired library as well as their application in targeting challenging disease targets.

Identification of a novel fusion gene, RARA::ANKRD34C, in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a specific subtype of acute myeloid leukemia that is distinguished by the chromosomal translocation t(15;17)(q24;q21), which leads to the fusion of the promyelocytic leukemia (PML) gene with the retinoic acid receptor alpha (RARA). Recently, we identified a novel fusion gene in APL, RARA::ankyrin repeat domain 34C (ANKRD34C), identified its functions by morphological, cytogenetic, molecular biological and multiplex fluorescence in situ hybridization analyses, and demonstrated the potential therapeutic effect clinically and experimentally of all-trans retinoic acid (ATRA); the findings have important implications for the diagnosis and treatment of atypical APL.

From Stem to Sternum: The Role of Shp2 in the Skeleton

Src homology-2 domain-containing phosphatase 2 (SHP2) is a ubiquitously expressed phosphatase that is vital for skeletal development and maintenance of chondrocytes, osteoblasts, and osteoclasts. Study of SHP2 function in small animal models has led to insights in phenotypes observed in SHP2-mutant human disease, such as Noonan syndrome. In recent years, allosteric SHP2 inhibitors have been developed to specifically target the protein in neoplastic processes. These inhibitors are highly specific and have great potential for disease modulation in cancer and other pathologies, including bone disorders. In this review, we discuss the importance of SHP2 and related signaling pathways (e.g., Ras/MEK/ERK, JAK/STAT, PI3K/Akt) in skeletal development. We review rodent models of pathologic processes caused by germline mutations that activate SHP2 enzymatic activity, with a focus on the skeletal phenotype seen in these patients. Finally, we discuss SHP2 inhibitors in development and their potential for disease modulation in these genetic diseases, particularly as it relates to the skeleton.

Targeted therapy in juvenile myelomonocytic leukemia: Where are we now?

Juvenile myelomonocytic leukemia (JMML) is a rare and aggressive clonal neoplasm of early childhood, classified as an overlap myeloproliferative/myelodysplastic neoplasm by the World Health Organization. In 90% of the patients with JMML, typical initiating mutations in the canonical Ras pathway genes NF1, PTPN11, NRAS, KRAS, and CBL can be identified. Hematopoietic stem cell transplantation (HSCT) currently is the established standard of care in most patients, although long-term survival is still only 50-60%. Given the limited therapeutic options and the important morbidity and mortality associated with HSCT, new therapeutic approaches are urgently needed. Hyperactivation of the Ras pathway as disease mechanism in JMML lends itself to the use of targeted therapy. Targeted therapy could play an important role in the future treatment of patients with JMML. This review presents a comprehensive overview of targeted therapies already developed and evaluated in vitro and in vivo in patients with JMML.

Tumor Cell-Autonomous SHP2 Contributes to Immune Suppression in Metastatic Breast Cancer

SH2 containing protein tyrosine phosphatase-2 (SHP2) is recognized as a druggable oncogenic phosphatase that is expressed in both tumor cells and immune cells. How tumor cell-autonomous SHP2 contributes to an immunosuppressive tumor microenvironment (TME) and therapeutic failure of immune checkpoint blockades in metastatic breast cancer (MBC) is not fully understood. Herein, we utilized systemic SHP2 inhibition and inducible genetic depletion of SHP2 to investigate immune reprogramming during SHP2 targeting. Pharmacologic inhibition of SHP2 sensitized MBC cells growing in the lung to α-programmed death ligand 1 (α-PD-L1) antibody treatment via relieving T-cell exhaustion induced by checkpoint blockade. Tumor cell-specific depletion of SHP2 similarly reduced pulmonary metastasis and also relieved exhaustion markers on CD8+ and CD4+ cells. Both systemic SHP2 inhibition and tumor cell-autonomous SHP2 depletion reduced tumor-infiltrated CD4+ T cells and M2-polarized tumor-associated macrophages. Analysis of TCGA datasets revealed that phosphorylation of SHP2 is important for immune-cell infiltration, T-cell activation and antigen presentation. To investigate this mechanistically, we conducted in vitro T-cell killing assays, which demonstrated that pretreatment of tumor cells with FGF2 and PDGF reduced the cytotoxicity of CD8+ T cells in a SHP2-dependent manner. Both growth factor receptor signaling and three-dimensional culture conditions transcriptionally induced PD-L1 via SHP2. Finally, SHP2 inhibition reduced MAPK signaling and enhanced STAT1 signaling, preventing growth factor-mediated suppression of MHC class I. Overall, our findings support the conclusion that tumor cell-autonomous SHP2 is a key signaling node utilized by MBC cells to engage immune-suppressive mechanisms in response to diverse signaling inputs from TME.

Significance

Findings present inhibition of SHP2 as a therapeutic option to limit breast cancer metastasis by promoting antitumor immunity.

Targeting SHP2 phosphatase in hematological malignancies

INTRODUCTION

Src homology-2-containing protein tyrosine phosphatase 2 (SHP2) is a ubiquitously expressed, non-receptor protein tyrosine phosphatase encoded by the PTPN11 gene. Gain-of-function (GOF) mutations in PTPN11 are associated with the development of various hematological malignancies and Noonan syndrome with multiple lentigines (NS-ML). Preclinical studies performed with allosteric SHP2 inhibitors and combination treatments of SHP2 inhibitors with inhibitors of downstream regulators (such as MEK, ERK, and PD-1/PD-L1) demonstrate improved antitumor benefits. However, the development of novel SHP2 inhibitors is necessary to improve the therapeutic strategies for hematological malignancies and tackle drug resistance and disease relapse.

AREAS COVERED

This review examines the structure of SHP2, its function in various signaling cascades, the consequences of constitutive activation of SHP2 and potential therapeutic strategies to treat SHP2-driven hematological malignancies.

EXPERT OPINION

While SHP2 inhibitors have exhibited promise in preclinical trials, numerous challenges remain in translation to the clinic, including drug resistance. Although PROTAC-based SHP2 degraders show better efficacy than SHP2 inhibitors, novel strategies need to be designed to improve SHP2-specific therapies in hematologic malignancies. Genome-wide CRISPR screening should also be used to identify molecules that confer resistance to SHP2 inhibitors. Targeting these molecules together with SHP2 can increase the target specificity and reduce drug resistance.

Genomic and Epigenomic Landscape of Juvenile Myelomonocytic Leukemia

Simple Summary

Juvenile myelomonocytic leukemia (JMML) is a rare pediatric myelodysplastic/myeloproliferative neoplasm characterized by the constitutive activation of the RAS pathway. In spite of the recent progresses in the molecular characterization of JMML, this disease is still a clinical challenge due to its heterogeneity, difficult diagnosis, poor prognosis, and the lack of curative treatment options other than hematopoietic stem cell transplantation (HSCT). In this review, we will provide a detailed overview of the genetic and epigenetic alterations occurring in JMML, and discuss their clinical relevance in terms of disease prognosis and risk of relapse after HSCT. We will also present the most recent advances on novel preclinical and clinical therapeutic approaches directed against JMML molecular targets. Finally, we will outline future research perspectives to further explore the oncogenic mechanism driving JMML leukemogenesis and progression, with special attention to the application of single-cell next-generation sequencing technologies.

Abstract

Juvenile myelomonocytic leukemia (JMML) is a rare myelodysplastic/myeloproliferative neoplasm of early childhood. Most of JMML patients experience an aggressive clinical course of the disease and require hematopoietic stem cell transplantation, which is currently the only curative treatment. JMML is characterized by RAS signaling hyperactivation, which is mainly driven by mutations in one of five genes of the RAS pathway, including PTPN11, KRAS, NRAS, NF1, and CBL. These driving mutations define different disease subtypes with specific clinico-biological features. Secondary mutations affecting other genes inside and outside the RAS pathway contribute to JMML pathogenesis and are associated with a poorer prognosis. In addition to these genetic alterations, JMML commonly presents aberrant epigenetic profiles that strongly correlate with the clinical outcome of the patients. This observation led to the recent publication of an international JMML stratification consensus, which defines three JMML clinical groups based on DNA methylation status. Although the characterization of the genomic and epigenomic landscapes in JMML has significantly contributed to better understand the molecular mechanisms driving the disease, our knowledge on JMML origin, cell identity, and intratumor and interpatient heterogeneity is still scarce. The application of new single-cell sequencing technologies will be critical to address these questions in the future.

Gab2 deficiency prevents Flt3-ITD driven acute myeloid leukemia in vivo

Internal tandem duplications (ITD) of the FMS-like tyrosine kinase 3 (FLT3) predict poor prognosis in acute myeloid leukemia (AML) and often co-exist with inactivating DNMT3A mutations. In vitro studies implicated Grb2-associated binder 2 (GAB2) as FLT3-ITD effector. Utilizing a Flt3-ITD knock-in, Dnmt3a haploinsufficient mouse model, we demonstrate that Gab2 is essential for the development of Flt3-ITD driven AML in vivo, as Gab2 deficient mice displayed prolonged survival, presented with attenuated liver and spleen pathology and reduced blast counts. Furthermore, leukemic bone marrow from Gab2 deficient mice exhibited reduced colony-forming unit capacity and increased FLT3 inhibitor sensitivity. Using transcriptomics, we identify the genes encoding for Axl and the Ret co-receptor Gfra2 as targets of the Flt3-ITD/Gab2/Stat5 axis. We propose a pathomechanism in which Gab2 increases signaling of these receptors by inducing their expression and by serving as downstream effector. Thereby, Gab2 promotes AML aggressiveness and drug resistance as it incorporates these receptor tyrosine kinases into the Flt3-ITD signaling network. Consequently, our data identify GAB2 as a promising biomarker and therapeutic target in human AML.

The RRAS2 pathogenic variant p.Q72L produces severe Noonan syndrome with hydrocephalus: A case report

Noonan syndrome (NS) is the most common disease among RASopathies, characterized by short stature, distinctive facial features, congenital cardiac defects, and variable developmental delay. NS rarely presents with overt neurologic manifestations, in particular hydrocephalus. Recent evidence suggests that pathogenic variants in the gene RRAS2 are a rare cause of NS. Specifically, an RRAS2 pathogenic variant, p.Q72L, may be particularly severe, manifesting with lethal neurologic findings. Here, we report a NS patient with documented p.Q72L variant in RRAS2. The patient was identified in utero to have hydrocephalus and a Dandy Walker malformation. Postnatal examination revealed multiple dysmorphic features, some reminiscent of NS including low-set posteriorly rotated ears, redundant nuchal skin, widely spaced nipples, and cryptorchidism. Despite suspicion of NS, results of a 14-gene Noonan syndrome panel (Invitae) were negative. Follow-up rapid whole exome sequencing revealed a de novo p.Q72L variant in RRAS2, a poorly studied gene recently identified as a cause of NS. The patient herein reported brings to three the total number of cases reported with the RRAS2 p.Q72L pathogenic variant. All three documented patients presented with a particularly fulminant course of NS, which included hydrocephalus. RRAS2, specifically p.Q72L, should be considered in severe NS cases with neurologic manifestations.

Functional interrogation and therapeutic targeting of protein tyrosine phosphatases

Protein tyrosine phosphatases (PTPs) counteract the enzymatic activity of protein tyrosine kinases to modulate levels of both normal and disease-associated protein tyrosine phosphorylation. Aberrant activity of PTPs has been linked to the progression of many disease states, yet no PTP inhibitors are currently clinically available. PTPs are without a doubt a difficult drug target. Despite this, many selective, potent, and bioavailable PTP inhibitors have been described, suggesting PTPs should once again be looked at as viable therapeutic targets. Herein, we summarize recently discovered PTP inhibitors and their use in the functional interrogation of PTPs in disease states. In addition, an overview of the therapeutic targeting of PTPs is described using SHP2 as a representative target.

Cancer stem cell phosphatases

Cancer stem cells (CSCs) are involved in the initiation and progression of human malignancies by enabling cancer tissue self-renewal capacity and constituting the therapy-resistant population of tumor cells. However, despite the exhausting characterization of CSC genetics, epigenetics, and kinase signaling, eradication of CSCs remains an unattainable goal in most human malignancies. While phosphatases contribute equally with kinases to cellular phosphoregulation, our understanding of phosphatases in CSCs lags severely behind our knowledge about other CSC signaling mechanisms. Many cancer-relevant phosphatases have recently become druggable, indicating that further understanding of the CSC phosphatases might provide novel therapeutic opportunities. This review summarizes the current knowledge about fundamental, but yet poorly understood involvement of phosphatases in the regulation of major CSC signaling pathways. We also review the functional roles of phosphatases in CSC self-renewal, cancer progression, and therapy resistance; focusing particularly on hematological cancers and glioblastoma. We further discuss the small molecule targeting of CSC phosphatases and their therapeutic potential in cancer combination therapies.

Scaffolding protein Gab2 is involved in postnatal development and lipopolysaccharide-induced activation of microglia in the mouse brain

Grb2-associated-binding protein-2 (Gab2) is a member of the Gab/DOS family and functions as an adapter protein downstream of several growth factor signaling pathways. Gab2 is considered an Alzheimer's disease susceptibility gene. However, the role of Gab2 in the brain is still largely unknown. Herein, we report that Gab2 is involved in the postnatal development of microglia in mice. The Gab2 expression in the brain was detected at postnatal day 1 (P1) and increased until P14 but decreased thereafter. The tyrosine phosphorylation of Gab2 (pGab2) was also detected at P1 and increased until P14. Next, we focused on microglial development in Gab2 knockout and heterozygous mice. Although differences were not detected in the cytoplasmic area of Iba1-labeled microglia between Gab2(±) and Gab2(-/-) mice, the analysis of CD68 and cathepsin D (indicators of microglial lysosomal activation) immunolabeling within Iba1+ cells revealed significant underdevelopment of microglial lysosomes in Gab2(-/-) mice at P60. In addition to the developmental abnormality of microglia in Gab2(-/-) mice, lipopolysaccharide-induced lysosomal activation was selectively suppressed in Gab2(-/-) mice compared to that in Gab2(±) mice. Our findings suggest that Gab2 is involved not only in postnatal development but also in lysosomal activation of microglia, therefore Gab2 dysfunction in microglia might potentially contribute to the development of neurodegenerative diseases.

Molecular insights into phytochemicals exhibiting anti-arthritic activity: systematic review : John Di Battista

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease with an unclear etiology causing severe inflammation, joint pain, and destruction that increases the chance of disability over time. Dysregulation of various immune signaling cascades regulates the formation of synovial hyperplasia and pannus formation. Imbalance in cytokine levels, predominantly proinflammatory cytokines like TNF-α, IL-1, IL-6, IL-17, and IL-12p70 profoundly influences the disease's pathogenesis. Even though various strategies are adopted to treat arthritis, their side effects and cost limit their usage. This review discusses the multiple pathways involved in the pathogenesis of rheumatoid arthritis, provides a systematic analysis of various phytochemicals, and discusses their potential molecular targets in RA treatment.

METHODS

The literature mining was done from scientific databases such as PubMed, Europe PMC, Web of Science, Scopus, etc. The terminologies used for literature mining were Rheumatoid arthritis, phytochemicals, cell signaling pathways, molecular mechanism, etc. RESULTS: NF-κB, MAPKs, and JAK-STAT are the key pathways potentially targeted for RA treatment. However, specific susceptible pathways and potential targets remain unexplored. Besides, the phytochemicals remain an immense source to be exploited for the effective treatment of RA, overcoming the demerits of the conventional strategies. Various in vitro and in vivo findings suggest that polyphenols and flavonoids effectively treat RA conditions overcoming the demerits, such as limitations in usage and toxicity. The phytochemicals should be explored in par with the pathological mechanisms with all the available targets to determine their therapeutic efficacy. Through the established therapeutic efficacy, phytochemicals can help developing therapeutics that are safe and efficacious for RA treatment.

Analysis of the microRNA and mRNA expression profile of ricin toxin-treated RAW264.7 cells reveals that miR-155-3p suppresses cell inflammation by targeting GAB2

Ricin toxin (RT) is one of the most lethal toxins derived from the seed of castor beans. In addition to its main toxic mechanism of inhibiting the synthesis of cellular proteins, RT can induce the production of inflammatory cytokines. MicroRNAs (miRNAs) play a key role in regulating both innate and adaptive immunity. To elucidate the regulation of miRNAs in RT-induced inflammation injury, the RNA high-throughput sequencing (RNA-Seq) technology was used to analyze the expression profile of miRNAs and mRNAs in RT-treated RAW264.7 cells. Results showed that a total of 323 mRNAs and 19 miRNAs differentially expressed after RT treated. Meanwhile, 713 miRNA-mRNA interaction pairs were identified by bioinformatics analysis. KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis showed that those interaction pairs were mainly involved in JAK-STAT, T cell receptor, and MAPK signaling pathways. Moreover, we further predicted and determined the targeting relationship between miR-155-3p and GAB2 through TargetScan and dual-luciferase reporter assay. Mechanically, overexpression of miR-155-3p can reduce the secretion of TNF-α in RAW264.7 cells, revealing a possible mechanism of miR-155-3p regulating RT-induced inflammatory injury. This study provides a new perspective for clarifying the mechanism of RT-induced inflammatory injury and reveals the potential role of miRNAs in innate immune regulation.

Pediatric Neoplasms Presenting with Monocytosis

PURPOSE OF REVIEW

Juvenile myelomonocytic leukemia (JMML) is a rare but severe pediatric neoplasm with hematopoietic stem cell transplant as its only established curative option. The development of targeted therapeutics for JMML is being guided by an understanding of the pathobiology of this condition. Here, we review JMML with an emphasis on genetics in order to (i) demonstrate the relationship between JMML genotype and clinical phenotype and (ii) explore potential genetic targets of novel JMML therapies.

RECENT FINDINGS

DNA hypermethylation studies have demonstrated consistently that methylation is related to disease severity. Increasing understanding of methylation in JMML may open the door to novel therapies, such as DNA methyltransferase inhibitors. The PI3K/AKT/MTOR, JAK/STAT, and RAF/MEK/ERK pathways are being investigated as therapeutic targets for JMML. Future therapy for JMML will be driven by an increased understanding of pathobiology. Targeted therapeutic approaches hold potential for improving outcomes in patients with JMML.

Juvenile myelomonocytic leukemia-A comprehensive review and recent advances in management

Juvenile myelomonocytic leukemia (JMML) is a rare pediatric myelodysplastic/myeloproliferative neoplasm overlap disease. JMML is associated with mutations in the RAS pathway genes resulting in the myeloid progenitors being sensitive to granulocyte monocyte colony-stimulating factor (GM-CSF). Karyotype abnormalities and additional epigenetic alterations can also be found in JMML. Neurofibromatosis and Noonan's syndrome have a predisposition for JMML. In a few patients, the RAS genes (NRAS, KRAS, and PTPN11) are mutated at the germline and this usually results in a transient myeloproliferative disorder with a good prognosis. JMML with somatic RAS mutation behaves aggressively. JMML presents with cytopenias and leukemic infiltration into organs. The laboratory findings include hyperleukocytosis, monocytosis, increased hemoglobin-F levels, and circulating myeloid precursors. The blast cells in the peripheral blood/bone-marrow aspirate are less than 20% and the absence of the BCR-ABL translocation helps to differentiate from chronic myeloid leukemia. JMML should be differentiated from immunodeficiencies, viral infections, intrauterine infections, hemophagolymphohistiocytosis, other myeloproliferative disorders, and leukemias. Chemotherapy is employed as a bridge to HSCT, except in few with less aggressive disease, in which chemotherapy alone can result in long term remission. Azacitidine has shown promise as a single agent to stabilize the disease. The prognosis of JMML is poor with about 50% of patients surviving after an allogeneic hematopoietic stem cell transplant (HSCT). Allogeneic HSCT is the only known cure for JMML to date. Myeloablative conditioning is most commonly used with graft versus host disease (GVHD) prophylaxis tailored to the aggressiveness of the disease. Relapses are common even after HSCT and a second HSCT can salvage a third of these patients. Novel options in the treatment of JMML e.g., hypomethylating agents, MEK inhibitors, JAK inhibitors, tyrosine kinase inhibitors, etc. are being explored.

SHP2 is a multifunctional therapeutic target in drug resistant metastatic breast cancer

Metastatic breast cancer (MBC) is an extremely recalcitrant disease capable of bypassing current targeted therapies via engagement of several growth promoting pathways. SH2 containing protein tyrosine phosphatase-2 (SHP2) is an oncogenic phosphatase known to facilitate growth and survival signaling downstream of numerous receptor inputs. Herein, we used inducible genetic depletion and two distinct pharmacological inhibitors to investigate the therapeutic potential of targeting SHP2 in MBC. Cells that acquired resistance to the ErbB kinase inhibitor, neratinib, displayed increased phosphorylation of SHP2 at the Y542 activation site. In addition, higher levels of SHP2 phosphorylation, but not expression, were associated with decreased survival of breast cancer patients. Pharmacological inhibition of SHP2 activity blocked ERK1/2 and AKT signaling generated from exogenous stimulation with FGF2, PDGF, and hGF and readily prevented MBC cell growth induced by these factors. SHP2 was also phosphorylated upon engagement of the extracellular matrix (ECM) via focal adhesion kinase. Consistent with the potential of SHP2-targeted compounds as therapeutic agents, the growth inhibitory property of SHP2 blockade was enhanced in ECM-rich 3D culture environments. In vivo blockade of SHP2 in the adjuvant setting decreased pulmonary metastasis and extended the survival of systemic tumor-bearing mice. Finally, inhibition of SHP2 in combination with FGFR-targeted kinase inhibitors synergistically blocked the growth of MBC cells. Overall, our findings support the conclusion that SHP2 constitutes a shared signaling node allowing MBC cells to simultaneously engage a diversity of growth and survival pathways, including those derived from the ECM.

Scaffold-based selective SHP2 inhibitors design using core hopping, molecular docking, biological evaluation and molecular simulation

PTPN11 (coding the gene of SHP2), a classic non-receptor protein tyrosine phosphatase, is implicated in multiple cell signaling pathway. Abnormal activation of SHP2 has been shown to contribute to a variety of human diseases, including Juvenile myelomonocytic leukemia (JMML), Noonan syndrome and tumors. Thus, the SHP2 inhibitors have important therapeutic value. Here, based on the compound PubChem CID 8,478,960 (IC₅₀ = 45.01 μM), a series of thiophene [2,3-d] pyrimidine derivatives (IC₅₀ = 0.4-37.87 μM) were discovered as novel and efficient inhibitors of SHP2 through powerful "core hopping" and CDOCKER technology. Furthermore, the SHP2-PTP phosphatase activity assay indicated that Comp#5 (IC₅₀ = 0.4 μM) was the most active SHP2 inhibitor. Subsequently, the effects of Comp#5 on the structure and function of SHP2 were investigated through molecular dynamics (MD) simulation and post-kinetic analysis. The result indicated that Comp#5 enhanced the interaction of residues THR357, ARG362, LYS366, PRO424, CYS459, SER460, ALA461, ILE463, ARG465, THR507 and GLN510 with the surrounding residues, improving the stability of the catalytic active region and the entrance of catalytic active region. In particular, the Comp#5 conjugated with residue ARG362, elevating the efficient and selectivity of SHP2 protein. The study here may pave the way for discovering the novel SHP2 inhibitors for suffering cancer patients.

Role of the JAK/STAT Pathway in Cervical Cancer: Its Relationship with HPV E6/E7 Oncoproteins

The janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway is associated with the regulation of essential cellular mechanisms, such as proliferation, invasion, survival, inflammation, and immunity. Aberrant JAK/STAT signaling contributes to cancer progression and metastatic development. STAT proteins play an essential role in the development of cervical cancer, and the inhibition of the JAK/STAT pathway may be essential for enhancing tumor cell death. Persistent activation of different STATs is present in a variety of cancers, including cervical cancer, and their overactivation may be associated with a poor prognosis and poor overall survival. The oncoproteins E6 and E7 play a critical role in the progression of cervical cancer and may mediate the activation of the JAK/STAT pathway. Inhibition of STAT proteins appears to show promise for establishing new targets in cancer treatment. The present review summarizes the knowledge about the participation of the different components of the JAK/STAT pathway and the participation of the human papillomavirus (HPV) associated with the process of cellular malignancy.

Elevated expressions of SHP2 and GAB2 correlated with VEGF in eutopic and ectopic endometrium of women with ovarian endometriosis

Aims: Protein tyrosine phosphatase Src-homology-2-domain-containing phosphatase 2 (SHP2) and adaptor protein Grb2-associated binding protein 2 (GAB2) can bind to each other in various signal transduction. However, the expression of SHP2 and GAB2 have not been investigated in endometriosis. The aim of the study was to evaluate the expressions of SHP2 and GAB2, and explore the correlation with Ki67 and VEGF in ovarian endometriosis.Materials and methods: The protein expressions and localizations were assessed immunohistochemically in ectopic, eutopic endometrium and normal endometrium from patients with (n = 30) and without (n = 30) ovarian endometriosis.Results: SHP2 was mainly present in the endometrial glandular epithelium, with increased expression in eutopic endometrium and even higher expression in ectopic endometrium compared to control endometrium (p < .05). GAB2 was immunolocalized in endometrial epithelium and stroma, increasing its expression from control endometrium to eutopic and ectopic endometrium (p < .05). Positive correlation was found between SHP2 and GAB2 in endometrium (p < .01). SHP2 and GAB2 both positively correlated with VEGF (p < .05), but not Ki67 in endometrium.Conclusions: We provide the first evidence that the protein expressions of SHP2 and GAB2 were elevated in ectopic and eutopic endometrium, suggesting GAB2-SHP2 axis regulating VEGF might contribute to the pathomechanism of endometriosis.

Low-Grade Gliomas in Patients with Noonan Syndrome: Case-Based Review of the Literature

Noonan syndrome (NS) is a congenital autosomic dominant condition characterized by a variable spectrum from a clinical and genetical point of view. Germline mutations in more than ten genes involved in RAS-MAPK signal pathway have been demonstrated to cause the disease. An higher risk for leukemia and solid malignancies, including brain tumors, is related to NS. A review of the published literature concerning low grade gliomas (LGGs) in NS is presented. We described also a 13-year-old girl with NS associated with a recurrent mutation in PTPN11, who developed three different types of brain tumors, i.e., an optic pathway glioma, a glioneuronal neoplasm of the left temporal lobe and a cerebellar pilocytic astrocytoma. Molecular characterization of the glioneuronal tumor allowed to detect high levels of phosphorylated MTOR (pMTOR); therefore, a therapeutic approach based on an mTOR inhibitor (everolimus) was elected. The treatment was well tolerated and proved to be effective, leading to a stabilization of the tumor, which was surgical removed. The positive outcome of the present case suggests considering this approach for patients with RASopathies and brain tumors with hyperactivated MTOR signaling.

Ubiquitin-specific peptidase 17 promotes cisplatin resistance via PI3K/AKT activation in non-small cell lung cancer

The suppression of ubiquitin-specific peptidase 17 (USP17) has previously been found to result in reduced tumorigenesis and invasion of non-small cell lung cancer (NSCLC) cells. However, the functions and underlying mechanisms of USP17 in NSCLC progression remain unclear. In the present study, cisplatin treatment was found to upregulate USP17 expression in a dose-dependent manner. Furthermore, USP17-overexpressing (USP17-OE) NSCLC A549 and H1299 cells were generated for mechanistic studies. The results from the Cell Counting Kit-8 assay revealed increased cell proliferation in USP17-OE cells compared with that of control cells. Moreover, the viability of USP17-OE cells was significantly higher than that of the control cells, when treated with cisplatin. The results of the biochemical studies demonstrated enhanced PI3K and AKT phosphorylation in USP17-OE NSCLC cells, whereas USP17-knockdown decreased these levels of phosphorylation. By contrast, an AKT inhibitor abolished the USP17-mediated enhancement of proliferation. Moreover, suppression of USP17 or the combination of the AKT inhibitor and cisplatin significantly reduced cell viability. Overall, the results of the present study suggest that PI3K/AKT activation is the underlying mechanism of USP17-mediated cisplatin resistance in NSCLC.

An update on the central nervous system manifestations of tuberous sclerosis complex

The autosomal dominant disorder tuberous sclerosis complex (TSC) is characterized by an array of manifestations both within and outside of the central nervous system (CNS), including hamartomas and other malformations. TSC is caused by mutations in the TSC1 or TSC2 gene resulting in activation of the mechanistic target of rapamycin (mTOR) signaling pathway. Study of TSC has shed light on the critical role of the mTOR pathway in neurodevelopment. This update reviews the genetic basis of TSC, its cardinal phenotypic CNS features, and recent developments in the field of TSC and other mTOR-altered disorders.

GAB2 inhibits chondrocyte apoptosis through PI3K-AKT signaling in osteoarthritis

Cartilage degeneration is considered the main pathologic feature of osteoarthritis (OA). Cumulative evidence indicates that chondrocyte apoptosis is associated with cartilage degradation. However, the underlying molecular mechanism of chondrocyte apoptosis remains unclear. Growth factor receptor-bound protein 2 (GAB2), an adaptor protein, belongs to the Gab family and is involved in various biologic processes. Here, we explored the role of GAB2 in the pathogenesis of osteoarthritis (OA). GAB2 expression was markedly increased in OA articular cartilage. GAB2 expression was also increased in an in vitro model of TNFα-induced apoptosis. GAB2 depletion by siRNA promoted expression of the apoptosis markers, PARP and caspase-3, and increased the number of apoptotic cells, indicating that GAB2 might have an anti-apoptotic effect in chondrocytes. Moreover, GAB2 knockdown inhibited AKT phosphorylation, increased BAX expression, and decreased BCL2 expression, which indicated that GAB2 regulates chondrocyte apoptosis through PI3K-AKT signaling. Taken together, our study indicates that GAB2 plays a vital role in chondrocyte apoptosis and provides a new therapeutic target for OA.

Therapeutic potential of targeting SHP2 in human developmental disorders and cancers

Src homology 2 (SH2)-containing protein tyrosine phosphatase 2 (SHP2), encoded by PTPN11, regulates cell proliferation, differentiation, apoptosis and survival via releasing intramolecular autoinhibition and modulating various signaling pathways, such as mitogen-activated protein kinase (MAPK) pathway. Mutations and aberrant expression of SHP2 are implicated in human developmental disorders, leukemias and several solid tumors. As an oncoprotein in some cancers, SHP2 represents a rational target for inhibitors to interfere. Nevertheless, its tumor suppressive effect has also been uncovered, indicating the context-specificity. Even so, two types of SHP2 inhibitors including targeting catalytic pocket and allosteric sites have been developed associated with resolved cocrystal complexes. Herein, we describe its structure, biological function, deregulation in human diseases and summarize recent advance in development of SHP2 inhibitors, trying to give an insight into the therapeutic potential in future.

Shp2 activation in bone marrow microenvironment mediates the drug resistance of B-cell acute lymphoblastic leukemia through enhancing the role of VCAM-1/VLA-4

B-cell acute lymphoblastic leukemia (B-ALL) is immune to the chemotherapy-induced apoptosis as a result of the protection of bone marrow mesenchymal stromal cells (BMSCs). However, the precise underlying mechanism of such protection remains unclear so far. In this experiment, protein tyrosine phosphatase 2 (Shp2), which was encoded by the PTPN11 gene, was highly expressed in BMSCs of the newly diagnosed and the recurrent B-ALL patients. The plasmid-induced (including Shp2 E76K) Shp2 activation in BMSCs (Shp2-activated BMSCs) markedly increased the BMSCs-mediated resistance of leukemia cells both in vitro and in vivo. Additionally, studies in vitro suggested that, the expression of vascular cell adhesion molecule 1 (VCAM-1) was markedly up-regulated in Shp2-activated BMSCs, and VCAM-1 expression in BMSCs of B-ALL patients was negatively correlated with Shp2 expression. Down-regulation of VCAM-1 in BMSCs using siRNA reversed the resistance of CCRF-SB cells mediated by the Shp2-activated BMSCs. As for the molecular mechanism, the PI3K/AKT pathway mediated the regulation of VCAM-1 by Shp2. Blocking the very late antigen-4 (VLA-4) by antibodies in CCRF-SB cells dramatically reversed the resistance of CCRF-SB cells mediated by the Shp2-activated BMSCs, and decreased the adhesion effects of both CCRF-SB cells and BMSCs. In conclusion, Shp2 activation in BMSCs up-regulates VCAM-1 expression through increasing the PI3K/AKT phosphorylation level, and targeting the VCAM-1/VLA-4 signaling may serve as a clinically relevant mechanism to overcome the BMSCs-mediated chemoresistance of B-ALL cells.

After 95 years, it's time to eRASe JMML

Juvenile myelomonocytic leukaemia (JMML) is a rare clonal disorder of early childhood. Constitutive activation of the RAS pathway is the initial event in JMML. Around 90% of patients diagnosed with JMML carry a mutation in the PTPN11, NRAS, KRAS, NF1 or CBL genes. It has been demonstrated that after this first genetic event, an additional somatic mutation or epigenetic modification is involved in disease progression. The available genetic and clinical data have enabled researchers to establish relationships between JMML and several clinical conditions, including Noonan syndrome, Ras-associated lymphoproliferative disease, and Moyamoya disease. Despite scientific progress and the development of more effective treatments, JMML is still a deadly disease: the 5-year survival rate is ~50%. Here, we report on recent research having led to a better understanding of the genetic and molecular mechanisms involved in JMML.

PTPN11 mutation with additional somatic alteration indicates unfavorable outcome in juvenile myelomonocytic leukemia: a retrospective clinical study from a single center

Juvenile myelomonocytic leukemia (JMML) is a heterogeneous childhood leukemia. The management of patients with JMML requires accurate assessment of genetic and clinical features to help in patient risk stratification. This study aimed to investigate the association between genomic alterations and prognosis in children with JMML. Genomic DNA was extracted from a total of 93 patients with JMML for targeted sequencing. Univariable and multivariable analysis were used to evaluate the correlation between gene mutations and prognosis of the patients. Patients with PTPN11 mutation exhibited significantly lower event-free survival (EFS) compared with non-PTPN11 mutations (P = 0.005). Patients without or with one somatic alteration at diagnosis showed significantly better prognosis in comparison with those with more than two alterations (P = 0.009). PTPN11 mutation with additional alterations showed significantly the poorest outcome in comparison with those with only one non-PTPN11 mutation, only one PTPN11 mutation, and combined mutations without PTPN11, respectively (P < 0.0001).Conclusion: Both PTPN11 mutation and the number of somatic alterations detected at diagnosis are likely to be the major determinant of outcome in JMML. The subgroup of patients with PTPN11 mutation showed the shortest survival which was even worsened when a secondary mutation was present.

Targeting SHP2 as a promising strategy for cancer immunotherapy

Src homology-2-containing protein tyrosine phosphatase 2 (SHP2) is a major phosphatase involved in several cellular processes. In recent years, SHP2 has been the focus of significant attention in human diseases, particular in cancer. Several studies have shown that SHP2 plays an important role in regulating immune cell functions in tumor microenvironment. A few clinical trials conducted using SHP2 allosteric inhibitors have shown remarkable anti-tumor benefits and good safety profiles. This review focuses on the current understanding of the regulation of SHP2 and highlights the vital roles of SHP2 in T lymphocytes, macrophages and cancer cells. It also summarizes the current development of SHP2 inhibitors as a promising strategy for cancer immunotherapy.

The Impact of PI3-kinase/RAS Pathway Cooperating Mutations in the Evolution of KMT2A-rearranged Leukemia

Leukemia is an evolutionary disease and evolves by the accrual of mutations within a clone. Those mutations that are systematically found in all the patients affected by a certain leukemia are called "drivers" as they are necessary to drive the development of leukemia. Those ones that accumulate over time but are different from patient to patient and, therefore, are not essential for leukemia development are called "passengers." The first studies highlighting a potential cooperating role of phosphatidylinositol 3-kinase (PI3K)/RAS pathway mutations in the phenotype of KMT2A-rearranged leukemia was published 20 years ago. The recent development in more sensitive sequencing technologies has contributed to clarify the contribution of these mutations to the evolution of KMT2A-rearranged leukemia and suggested that these mutations might confer clonal fitness and enhance the evolvability of KMT2A-leukemic cells. This is of particular interest since this pathway can be targeted offering potential novel therapeutic strategies to KMT2A-leukemic patients. This review summarizes the recent progress on our understanding of the role of PI3K/RAS pathway mutations in initiation, maintenance, and relapse of KMT2A-rearranged leukemia.

Epigenetic regulation of HOTAIR in advanced chronic myeloid leukemia

Purpose

Chronic myeloid leukemia (CML) accounts for ~10% of leukemia cases, and its progression involves epigenetic gene regulation. This study investigated epigenetic regulation of HOTAIR and its target microRNA, miR-143, in advanced CML.

Patients and methods

We first isolated bone marrow mononuclear cells from 70 patients with different phases of CML and from healthy donors as normal control; we also cultured K562 and KCL22 cells, treated with demethylation drug; MTT assay, flow cytometry, quantitative real-time polymerase chain reaction (qPCR), methylation-specific polymerase chain reaction (MSP), Western blot, luciferase assay, RNA pull-down assay and RNA-binding protein immunoprecipitation (RIP) assay were performed.

Result

As measured by qPCR, HOTAIR expression in K562 cells, KCL22 cells, and samples from cases of advanced-stage CML increased with levels of several DNA methyltransferases and histone deacetylates, including DNMT1, DNMT3A, HDAC1, EZH2, and LSD1, and miR-143 levels were decreased and HOTAIR levels were increased. Treatment with 5-azacytidine, a DNA methylation inhibitor, decreased DNMT1, DNMT3A, HDAC1, EZH2, LSD1 mRNA, protein levels, and HOTAIR mRNA levels but increased miR-143 levels. HOTAIR knockdown and miR-143 overexpression both inhibited proliferation and promoted apoptosis in KCL22 and K562 cells through the PI3K/AKT pathway. RNA pull-down, mass spectrometry, and RIP assays showed that HOTAIR interacted with EZH2 and LSD1. A dual-luciferase assay demonstrated that HOTAIR interacted with miR-143.

Conclusion

Our findings demonstrate the key epigenetic interactions of HOTAIR related to CML progression and suggest HOTAIR as a potential therapeutic target for advanced CML. Furthermore, our results support the use of demethylation drugs as a CML treatment strategy.

[Advances in the treatment of juvenile myelomonocytic leukemia]

Juvenile myelomonocytic leukemia (JMML) is a rare chronic myeloid leukemia in children and has the features of both myelodysplastic syndrome and myeloproliferative neoplasm. It is highly malignant and has a poor treatment outcome. Children with JMML have a poor response to conventional chemotherapy. At present, hematopoietic stem cell transplantation is the only possible cure for this disease. In recent years, significant progress has been made in targeted therapy for mutant genes in the Ras signaling pathway and demethylation treatment of aberrant methylation of polygenic CpG islands. This article reviews the treatment and efficacy evaluation of JMML.

Spinal SHP2 Contributes to Exaggerated Incisional Pain in Adult Rats Subjected to Neonatal and Adult Incisions via PI3K

Neonatal injury-induced exaggeration of pain hypersensitivity after adult trauma is a significant clinical challenge. However, the underlying mechanisms remain poorly understood. Growing evidence shows that spinal Src homology-2 domain-containing protein tyrosine phosphatase-2 (SHP2) contributes to chronic pain in adult rodents. Here we demonstrated that the phosphorylation and expression of SHP2 in synaptosomal fraction of the spinal dorsal horn are elevated in adult rats subjected to neonatal and adult incisions (nIN-IN), and the upregulation of SHP2 is highly correlated with pain hypersensitivity. Intrathecal blockade of SHP2 phosphorylation using a SHP2 protein tyrosine phosphatase inhibitor NSC-87877, or knockdown of SHP2 by intrathecal delivery of small interfering RNA (siRNA), ameliorates mechanical allodynia and heat hyperalgesia in nIN-IN rats. Moreover, the expression of phosphatidylinositol 3-kinase (PI3K) in the spinal dorsal horn is significantly increased in nIN-IN rats. Intrathecal application of PI3K inhibitor, LY294002 or wortmannin, alleviates pain hypersensitivity in nIN-IN rats. Additionally, intrathecal administration of NSC-87877 or SHP2 siRNA attenuates the upregulation of PI3K. Finally, no alternation of SHP2 phosphorylation in the dorsal root ganglion and dorsal root of nIN-IN rats as well as PI3K expression in the dorsal root of nIN-IN rats intrathecally treated with NSC-87877 or SHP2 siRNA is observed. These results suggest that the phosphorylation and expression of SHP2 in the spinal dorsal horn play vital roles in neonatal incision-induced exaggeration of adult incisional pain via PI3K. Thus, SHP2 and PI3K may serve as potential therapeutic targets for exaggerated incisional pain induced by neonatal and adult injuries.

SHP2-Mediated Signal Networks in Stem Cell Homeostasis and Dysfunction

Stem cells, including embryonic stem cells (ESCs) and adult stem cells, play a central role in mammal organism development and homeostasis. They have two unique properties: the capacity for self-renewal and the ability to differentiate into many specialized cell types. Src homology region 2- (SH2-) containing protein tyrosine phosphatase 2 (SHP-2), a nonreceptor protein tyrosine phosphatase encoded by protein tyrosine phosphatase nonreceptor type 11 gene (PTPN11), regulates multicellular differentiation, proliferation, and survival through numerous conserved signal pathways. Gain-of-function (GOF) or loss-of-function (LOF) SHP2 in various cells, especially for stem cells, disrupt organism self-balance and lead to a plethora of diseases, such as cancer, maldevelopment, and excessive hyperblastosis. However, the exact mechanisms of SHP2 dysfunction in stem cells remain unclear. In this review, we intended to raise the attention and clarify the framework of SHP2-mediated signal pathways in various stem cells. Establishment of integrated signal architecture, from ESCs to adult stem cells, will help us to understand the changes of dynamic, multilayered pathways in response to SHP2 dysfunction. Overall, better understanding the functions of SHP2 in stem cells provides a new avenue to treat SHP2-associated diseases.

Mutation-specific signaling profiles and kinase inhibitor sensitivities of juvenile myelomonocytic leukemia revealed by induced pluripotent stem cells

Juvenile myelomonocytic leukemia (JMML) is an uncommon myeloproliferative neoplasm driven by Ras pathway mutations and hyperactive Ras/MAPK signaling. Outcomes for many children with JMML remain dismal with current standard-of-care cytoreductive chemotherapy and hematopoietic stem cell transplantation. We used patient-derived induced pluripotent stem cells (iPSCs) to characterize the signaling profiles and potential therapeutic vulnerabilities of PTPN11-mutant and CBL-mutant JMML. We assessed whether MEK, JAK, and PI3K/mTOR kinase inhibitors (i) could inhibit myeloproliferation and aberrant signaling in iPSC-derived hematopoietic progenitors with PTPN11 E76K or CBL Y371H mutations. We detected constitutive Ras/MAPK and PI3K/mTOR signaling in PTPN11 and CBL iPSC-derived myeloid cells. Activated signaling and growth of PTPN11 iPSCs were preferentially inhibited in vitro by the MEKi PD0325901 and trametinib. Conversely, JAK/STAT signaling was selectively activated in CBL iPSCs and abrogated by the JAKi momelotinib and ruxolitinib. The PI3Kδi idelalisib and mTORi rapamycin inhibited signaling and myeloproliferation in both PTPN11 and CBL iPSCs. These findings demonstrate differential sensitivity of PTPN11 iPSCs to MEKi and of CBL iPSCs to JAKi, but similar sensitivity to PI3Ki and mTORi. Clinical investigation of mutation-specific kinase inhibitor therapies in children with JMML may be warranted.

BRAF inhibition upregulates a variety of receptor tyrosine kinases and their downstream effector Gab2 in colorectal cancer cell lines

BRAF mutations occur in ~10% of colorectal cancer (CRC) and are associated with poor prognosis. Inhibitors selective for the BRAF^V600E oncoprotein, the most common BRAF mutant, elicit only poor response rates in BRAF-mutant CRC as single agents. This unresponsiveness was mechanistically attributed to the loss of negative feedbacks on the epidermal growth factor receptor (EGFR) and initiated clinical trials that combine BRAF (and MEK) inhibitors, either singly or in combination, with the anti-EGFR antibodies cetuximab or panitumumab. First results of these combinatorial studies demonstrated improved efficacy, however, the response rates still were heterogeneous. Here, we show that BRAF inhibition leads to the upregulation of a variety of receptor tyrosine kinases (RTKs) in CRC cell lines, including not only the EGFR, but also human epidermal growth factor receptor (HER) 2 and HER3. Importantly, combination of the BRAF inhibitors (BRAFi) vemurafenib (PLX4032), dabrafenib, or encorafenib with inhibitors dually targeting the EGFR and HER2 (such as lapatinib, canertinib, and afatinib) significantly reduced the metabolic activity and proliferative potential of CRC cells. This re-sensitization was also observed after genetic depletion of HER2 or HER3. Interestingly, BRAF inhibitors did not only upregulate RTKs, but also increased the abundance of the GRB2-associated binders (Gab) 1 and Gab2, two important amplifiers of RTK signaling. An allele-specific shRNA-mediated knockdown of BRAF^V600E revealed that Gab2 upregulation was directly dependent on the loss of the oncoprotein and was not caused by an "off-target" effect of these kinase inhibitors. Furthermore, Gab2 and Gab2-mediated Shp2 signaling were shown to be functionally important in BRAFi resistance. These findings highlight potential new escape mechanisms to these targeted therapies and indicate that a broad suppression of RTK signaling might be beneficial and should be taken into account in future research addressing targeted therapy in BRAF-mutant CRC.

RAS-pathway mutation patterns define epigenetic subclasses in juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is an aggressive myeloproliferative disorder of early childhood characterized by mutations activating RAS signaling. Established clinical and genetic markers fail to fully recapitulate the clinical and biological heterogeneity of this disease. Here we report DNA methylome analysis and mutation profiling of 167 JMML samples. We identify three JMML subgroups with unique molecular and clinical characteristics. The high methylation group (HM) is characterized by somatic PTPN11 mutations and poor clinical outcome. The low methylation group is enriched for somatic NRAS and CBL mutations, as well as for Noonan patients, and has a good prognosis. The intermediate methylation group (IM) shows enrichment for monosomy 7 and somatic KRAS mutations. Hypermethylation is associated with repressed chromatin, genes regulated by RAS signaling, frequent co-occurrence of RAS pathway mutations and upregulation of DNMT1 and DNMT3B, suggesting a link between activation of the DNA methylation machinery and mutational patterns in JMML.

Role of SHP2 in hematopoiesis and leukemogenesis

PURPOSE OF REVIEW

SH2 domain-containing tyrosine phosphatase 2 (SHP2), encoded by PTPN11 plays an important role in regulating signaling from cell surface receptor tyrosine kinases during normal development as well as oncogenesis. Herein we review recently discovered roles of SHP2 in normal and aberrant hematopoiesis along with novel strategies to target it.

RECENT FINDINGS

Cell autonomous role of SHP2 in normal hematopoiesis and leukemogenesis has long been recognized. The review will discuss the newly discovered role of SHP2 in lineage specific differentiation. Recently, a noncell autonomous role of oncogenic SHP2 has been reported in which activated SHP2 was shown to alter the bone marrow microenvironment resulting in transformation of donor derived normal hematopoietic cells and development of myeloid malignancy. From being considered as an 'undruggable' target, recent development of allosteric inhibitor has made it possible to specifically target SHP2 in receptor tyrosine kinase driven malignancies.

SUMMARY

SHP2 has emerged as an attractive target for therapeutic targeting in hematological malignancies for its cell autonomous and microenvironmental effects. However a better understanding of the role of SHP2 in different hematopoietic lineages and its crosstalk with signaling pathways activated by other genetic lesions is required before the promise is realized in the clinic.

Aberrant neuronal activity-induced signaling and gene expression in a mouse model of RASopathy

Noonan syndrome (NS) is characterized by reduced growth, craniofacial abnormalities, congenital heart defects, and variable cognitive deficits. NS belongs to the RASopathies, genetic conditions linked to mutations in components and regulators of the Ras signaling pathway. Approximately 50% of NS cases are caused by mutations in PTPN11. However, the molecular mechanisms underlying cognitive impairments in NS patients are still poorly understood. Here, we report the generation and characterization of a new conditional mouse strain that expresses the overactive Ptpn11D61Y allele only in the forebrain. Unlike mice with a global expression of this mutation, this strain is viable and without severe systemic phenotype, but shows lower exploratory activity and reduced memory specificity, which is in line with a causal role of disturbed neuronal Ptpn11 signaling in the development of NS-linked cognitive deficits. To explore the underlying mechanisms we investigated the neuronal activity-regulated Ras signaling in brains and neuronal cultures derived from this model. We observed an altered surface expression and trafficking of synaptic glutamate receptors, which are crucial for hippocampal neuronal plasticity. Furthermore, we show that the neuronal activity-induced ERK signaling, as well as the consecutive regulation of gene expression are strongly perturbed. Microarray-based hippocampal gene expression profiling revealed profound differences in the basal state and upon stimulation of neuronal activity. The neuronal activity-dependent gene regulation was strongly attenuated in Ptpn11D61Y neurons. In silico analysis of functional networks revealed changes in the cellular signaling beyond the dysregulation of Ras/MAPK signaling that is nearly exclusively discussed in the context of NS at present. Importantly, changes in PI3K/AKT/mTOR and JAK/STAT signaling were experimentally confirmed. In summary, this study uncovers aberrant neuronal activity-induced signaling and regulation of gene expression in Ptpn11D61Y mice and suggests that these deficits contribute to the pathophysiology of cognitive impairments in NS.