Phosphorylation Of SHP-2 Research Articles

Inhibition of SHP-1 activity by PKC-θ regulates NK cell activation threshold and cytotoxicity.

Natural killer (NK) cells play a crucial role in immunity, killing virally infected and cancerous cells. The balance of signals initiated upon engagement of activating and inhibitory NK receptors with cognate ligands determines killing or tolerance. Nevertheless, the molecular mechanisms regulating rapid NK cell discrimination between healthy and malignant cells in a heterogeneous tissue environment are incompletely understood. The SHP-1 tyrosine phosphatase is the central negative NK cell regulator that dephosphorylates key activating signaling proteins. Though the mechanism by which SHP-1 mediates NK cell inhibition has been partially elucidated, the pathways by which SHP-1 is itself regulated remain unclear. Here, we show that phosphorylation of SHP-1 in NK cells on the S591 residue by PKC-θ promotes the inhibited SHP-1 'folded' state. Silencing PKC-θ maintains SHP-1 in the active conformation, reduces NK cell activation and cytotoxicity, and promotes tumor progression in vivo. This study reveals a molecular pathway that sustains the NK cell activation threshold through suppression of SHP-1 activity.

Immunomodulation of T- and NK-cell Responses by a Bispecific Antibody Targeting CD28 Homolog and PD-L1.

Checkpoint blockade therapies targeting PD-1/PD-L1 and CTLA-4 are clinically successful but also evoke adverse events due to systemic T-cell activation. We engineered a bispecific, mAb targeting CD28 homolog (CD28H), a newly identified B7 family receptor that is constitutively expressed on T and natural killer (NK) cells, with a PD-L1 antibody to potentiate tumor-specific immune responses. The bispecific antibody led to T-cell costimulation, induced NK-cell cytotoxicity of PD-L1-expressing tumor cells, and activated tissue-resident memory CD8+ T cells. Mechanistically, the CD28H agonistic arm of the bispecific antibody reduced PD-L1/PD-1-induced SHP2 phosphorylation while simultaneously augmenting T-cell receptor signaling by activating the MAPK and AKT pathways. This bispecific approach could be used to target multiple immune cells, including CD8+ T cells, tissue-resident memory T cells, and NK cells, in a tumor-specific manner that may lead to induction of durable, therapeutic antitumor responses.

Tyr62 phosphorylation of the phosphatase SHP2 enables acquired resistance to SHP2 allosteric inhibitors in FLT3-ITD-driven AML - DIA data

Tyr62 phosphorylation of the phosphatase SHP2 enables acquired resistance to SHP2 allosteric inhibitors in FLT3-ITD-driven AML - DIA data

Isovitexin Inhibits Ginkgolic Acids-Induced Inflammation Through Downregulating SHP2 Activation.

It has been reported that Celtis sinensis Pers. is employed as a folk medicine for the treatment of inflammatory diseases. But the mechanism supporting its use as anti-inflammatory remains unclear. To investigate the anti-inflammatory of Celtis sinensis Pers. ICR mice were provided Celtis sinensis Pers. leaf extract (CLE) at 100, 200 mg/kg after ginkgolic acids (GA) sensitization. Our data showed that CLE and the main flavonoid isovitexin in CLE could ameliorate GA-induced contact dermatitis in mice. Ear swelling, inflammatory cell infiltration and splenomegaly were inhibited significantly by isovitexin, while the weight loss of mice in the isovitexin-treated group was much better than that in the dexamethasone-treated group (positive control drug). It has been reported in previous research that GA-induced inflammation is closely related to the T cell response. Therefore, T cells were the focus of the anti-inflammatory effect of isovitexin in this paper. The in vivo results showed that isovitexin (10, 20 mg/kg) inhibited the expression of proinflammatory cytokines (TNF-α, IFN-γ, IL-2 and IL-17A) in lymph nodes, inhibited the secretion of cytokines into the serum from mice with contact dermatitis and promoted the expression of apoptosis-related proteins. In vitro, isovitexin also induced apoptosis and inhibited proinflammatory cytokine expression in Con A-activated T cells. Further study showed that the MAPK and STAT signaling pathways and the phosphorylation of SHP2 were inhibited by isovitexin. Both molecular docking and biological experiments indicated that SHP2 may be an anti-inflammatory target of isovitexin in T cells. Taken together, isovitexin can serve as a potential natural agent for the treatment or prevention of GA-induced inflammatory problems.

Allosteric inhibition reveals SHP2-mediated tumor immunosuppression in colon cancer by single-cell transcriptomics

Colorectal cancer (CRC), a malignant tumor worldwide consists of microsatellite instability (MSI) and stable (MSS) phenotypes. Although SHP2 is a hopeful target for cancer therapy, its relationship with innate immunosuppression remains elusive. To address that, single-cell RNA sequencing was performed to explore the role of SHP2 in all cell types of tumor microenvironment (TME) from murine MC38 xenografts. Intratumoral cells were found to be functionally heterogeneous and responded significantly to SHP099, a SHP2 allosteric inhibitor. The malignant evolution of tumor cells was remarkably arrested by SHP099. Mechanistically, STING–TBK1–IRF3-mediated type I interferon signaling was highly activated by SHP099 in infiltrated myeloid cells. Notably, CRC patients with MSS phenotype exhibited greater macrophage infiltration and more potent SHP2 phosphorylation in CD68+ macrophages than MSI-high phenotypes, suggesting the potential role of macrophagic SHP2 in TME. Collectively, our data reveals a mechanism of innate immunosuppression mediated by SHP2, suggesting that SHP2 is a promising target for colon cancer immunotherapy.

The tyrosine phosphatase SHP-2 dephosphorylated by ALV-J via its Env efficiently promotes ALV-J replication

ABSTRACT Avian leukosis virus subgroup J (ALV-J) generally induces hemangioma, myeloid leukosis, and immunosuppression in chickens, causing significant poultry industry economic losses worldwide. The unusual env gene of ALV-J, with low homology to other subgroups of ALVs, is associated with its unique pathogenesis. However, the exact molecular basis for the pathogenesis and oncogenesis of ALV-J is still not fully understood. In this study, ALV-J infection and the overexpression of Env could efficiently downregulate the phosphorylation of SHP-2 (pSHP-2) in vitro and in vivo. The membrane-spanning domain (MSD) in Env Gp37 was the functional domain responsible for pSHP-2 downregulation. Moreover, the overexpression of SHP-2 could effectively promote the replication of ALV-J, whereas knockout or allosteric inhibition of SHP-2 could inhibit ALV-J replication. In addition, the knockout of endogenous chicken SHP-2 could significantly increase the proliferation ability of DF-1 cells. All these data demonstrate that SHP-2 dephosphorylated by ALV-J Env could efficiently promote ALV-J replication, highlighting the important role of SHP-2 in the pathogenesis of ALV-J and providing a new target for developing antiviral drugs against ALV-J.

Overcoming interferon (IFN)-γ resistance ameliorates transforming growth factor (TGF)-β-mediated lung fibroblast-to-myofibroblast transition and bleomycin-induced pulmonary fibrosis

Abnormal activation of transforming growth factor (TGF)-β is a common cause of fibroblast activation and fibrosis. In bleomycin (BLM)-induced lung fibrosis, the marked expression of phospho-Src homology-2 domain-containing phosphatase (SHP) 2, phospho-signal transducer and activator of transcription (STAT) 3, and suppressor of cytokine signaling (SOCS) 3 was highly associated with pulmonary parenchymal lesions and collagen deposition. Human pulmonary fibroblasts differentiated into myofibroblasts exhibited activation of SHP2, SOCS3, protein inhibitor of activated STAT1, STAT3, interleukin (IL)-6, and IL-10. The significant retardation of interferon (IFN)-γ signaling in myofibroblasts was revealed by the decreased expression of phospho-STAT1, IFN-γ-associated genes, and IFN-γ-inducible protein (IP) 10. Microarray analysis showed an induction of fibrotic genes in TGF-β1-differentiated myofibroblasts, whereas IFN-γ-regulated anti-fibrotic genes were suppressed. Interestingly, BIBF 1120 treatment effectively inhibited both STAT3 and SHP2 phosphorylation in TGF-β1-differentiated myofibroblasts and BLM fibrotic lung tissues, which was accompanied by suppression of fibroblast-myofibroblast transition. Moreover, the combined treatment of BIBF 1120 plus IFN-γ or SHP2 inhibitor PHPS1 plus IFN-γ markedly reduced TGF-β1-induced α-smooth muscle actin and further ameliorated BLM lung fibrosis. Accordingly, myofibroblasts were hyporesponsiveness to IFN-γ, while blockade of SHP2 contributed to the anti-fibrotic efficacy of IFN-γ.

Inhibition of TRPV1 by SHP-1 in nociceptive primary sensory neurons is critical in PD-L1 analgesia.

Recently programmed death-ligand 1 (PD-L1) receptor PD-1 was found in dorsal root ganglion (DRG) neurons, and PD-L1 activates PD-1 to inhibit inflammatory and neuropathic pain by modulating neuronal excitability. However, the downstream signaling of PD-1 in sensory neurons remains unclear. Here, we show that PD-L1 activated Src homology 2 domain-containing tyrosine phosphatase-1 (SHP-1) to downregulate transient receptor potential vanilloid 1 (TRPV1) in DRG neurons and inhibit bone cancer pain in mice. Local injection of PD-L1 produced analgesia. PD-1 in DRG neurons colocalized with TRPV1 and SHP-1. PD-L1 induced the phosphorylation of SHP-1 in DRG TRPV1 neurons and inhibited TRPV1 currents. Loss of TRPV1 in mice abolished bone cancer–induced thermal hyperalgesia and PD-L1 analgesia. Conditioned deletion of SHP-1 in NaV1.8+ neurons aggravated bone cancer pain and diminished the inhibition of PD-L1 on TRPV1 currents and pain. Together, our findings suggest that PD-L1/PD-1 signaling suppresses bone cancer pain via inhibition of TRPV1 activity. Our results also suggest that SHP-1 in sensory neurons is an endogenous pain inhibitor and delays the development of bone cancer pain via suppressing TRPV1 function.

The SLAMF3 rs509749 polymorphism correlates with malignant potential in multiple myeloma

The signaling lymphocytic activation molecule family 3 (SLAMF3) is highly expressed on plasma cells from patients with multiple myeloma (MM) and induces high malignant potential by ERK signaling mediated via the interaction with adaptor proteins SHP2 and GRB2. This study focused on the single-nucleotide polymorphism (SNP) of the SLAMF3 gene (rs509749, 1804A>G, M602V) in MM. The SNP G allele was a major type, and the frequencies of the GG, GA, and AA genotypes were 61.8%, 29.4%, and 8.8%, respectively, in patients with MM, which was almost the same as in healthy the control group in the Japanese population. Interestingly, patients with GG genotypes had significantly shorter overall survival times than patients with GA/AA genotypes. Consistent with those results, SLAMF3-overexpressing KMS-34 cells with the G allele (V602) had higher cell proliferation potential and were more resistant to anti-MM agents than those with the A allele (M602). When those cells were subcutaneously inoculated into NOG mice, tumor sizes in mice receiving V602 cells rapidly increased, and survival was significantly shorter than in mice injected with M602 cells. Furthermore, SLAMF3 V602 molecules bound more tightly to SHP2 and GRB2, with increased SHP2 and ERK phosphorylation compared with M602 cells. The mRNA expression of cell cycle-related genes (CCND1 and CCNE1) and anti-apoptotic genes (BCL2L and p21) was increased in V602 cells compared with M602 cells. The results thus suggested that the G allele of SLAMF3 SNP rs509749 may be associated with MM disease progression.

Dioscin Promotes Prostate Cancer Cell Apoptosis and Inhibits Cell Invasion by Increasing SHP1 Phosphorylation and Suppressing the Subsequent MAPK Signaling Pathway.

Dioscin possesses antioxidant effects and has anticancer ability in many solid tumors including prostate cancer (PCa). Nevertheless, its effect and mechanism of anti-PCa action remain unclear. The tyrosine protein phosphatase SHP1, which contains an oxidation-sensitive domain, has been confirmed as a target for multicancer treatment. Further studies are needed to determine whether dioscin inhibits PCa through SHP1. We performed in vitro studies using androgen-sensitive (LNCaP) and androgen-independent (LNCaP -C81) cells to investigate the anticancer effects and possible mechanisms of dioscin after administering interleukin-6 (IL-6) and dihydrotestosterone (DHT). Our results show that dioscin inhibited cell growth and invasion by increasing SHP1 phosphorylation [p-SHP1 (Y536)] and inhibiting the subsequent P38 mitogen-activated protein kinase signaling pathway. Further in vivo studies confirmed that dioscin promoted caspase-3 and Bad-related cell apoptosis in these two cell lines. Our research suggests that the anticancer effects of dioscin on PCa may occur through SHP1. Dioscin may be useful to treat androgen-sensitive and independent PCa in the future.

Caveolin-1 Ablation Imparts Partial Protection Against Inner Retinal Injury in Experimental Glaucoma and Reduces Apoptotic Activation.

Retinal ganglion cell degeneration is a characteristic feature of glaucoma, and accordingly, protection of these cells constitutes a major therapeutic objective in the disease. Here, we demonstrate the key influence of caveolin (Cav) in regulating the inner retinal homeostasis in two models of experimentally elevated intraocular pressure (IOP). Two groups of Cav-1-/- and wild-type mice were used in the study. Animals were subjected to experimentally induced chronic and acutely elevated IOP and any changes in their retinal function were assessed by positive scotopic threshold response recordings. TUNEL and cleaved caspase-3 assays were performed to evaluate apoptotic changes in the retina while Brn3a immunostaining was used as a marker to assess and quantify ganglion cell layer (GCL) changes. H&E staining was carried out on retinal sections to evaluate histological differences in retinal laminar structure. Cav-1 ablation partially protected the inner retinal function in both chronic and acute models of elevated IOP. The protective effects of Cav-1 loss were also evident histologically by reduced loss of GCL density in both models. The phenotypic protection in Cav-1-/- glaucoma mice paralleled with increased TrkB phosphorylation and reduced endoplasmic reticulum stress markers and apoptotic activation in the inner retinas. This study corroborated previous findings of enhanced Shp2 phosphorylation in a chronic glaucoma model and established a novel role of Cav-1 in mediating activation of this phosphatase in the inner retina in vivo. Collectively, these findings highlight the critical involvement of Cav-1 regulatory mechanisms in ganglion cells in response to increased IOP, implicating Cav-1 as a potential therapeutic target in glaucoma.

Human CD31 on Swine Endothelial Cells Induces SHP-1 Phosphorylation in Macrophages

BackgroundInnate immunity by natural killer (NK) cells, macrophages, and neutrophils cause severe rejections in xenotransplantation. Therefore, the development of strategies for suppressing macrophages has considerable potential in practical applications of xenotransplantation. Recently, we found that human CD31 on swine endothelial cells (SECs) suppresses neutrophil-mediated xenogeneic rejection through homophilic binding. Since a significant amount of CD31 is expressed not only on neutrophils but also on macrophages, we studied the function of human CD31 in macrophage-mediated cytotoxicity. MethodsSECs and hCD31-transfected SECs (SEC/hCD31) were co-cultured with macrophages and cytotoxicity by macrophages was evaluated with water-soluble tetrazolium salt, or WST-8, assay. To confirm whether or not inhibitory signals are induced by hCD31 homophilic binding, the phosphorylation of the enzyme SHP-1 was investigated with Western blotting. ResultsNo suppression of cytotoxicity was induced in macrophages that had been co-cultured with SEC/CD31. However, phosphorylation of SHP-1 was induced in macrophages that had been co-cultured with SEC/hCD31. ConclusionsHuman CD31 on SEC may induce not only inhibitory signals but also activation signals via the binding to other receptors for hCD31.

Phosphatase SHP2-mediated mitochondrial homeostasis for the resolution of inflammation

Abstract The negative regulation of inflammation is very important for the resolution of inflammatory diseases. Although many components and mediators in inflammation have been identified, how inflammation is finely regulated remains lack of evidence. Here we show that Src homology-2 domain containing protein tyrosine phosphatase-2 (SHP2) translocates to mitochondria in the early time of inflammatory stimulation. The RRWFH motif in SH2 domain is essential for the translocation of SHP2. This phosphatase localizes in the mitochondrial matrix with the help of Tom20/Tom40 in outer membrane and Tim23 in inner membrane. Then SHP2 interacts with ANT1, a central molecule controlling mitochondrial permeability transition. This mechanism prevents the collapse of mitochondrial membrane potential, mtDNA release and ROS production, and thus inhibits the hyperactivation of NLRP3 inflammasome. Ablation or inhibition of SHP2 in macrophage causes intensified NLRP3 inflammasome activation, production of IL-1β and IL-18, and increased sensitivity to peritonitis. We are also engaged in seeking the activator of SHP2. We have found that the natural products fusaruside and trichomides A can increase the phosphorylation of SHP2 and some of synthesized compounds can directly activate the phosphatase. These SHP2 activators show a significant anti-inflammatory activity in various disease models. Collectively, our data highlight that SHP2 orchestrates an intrinsic regulatory loop for the mitochondrial homeostasis to limit excessive NLRP3 inflammasome activation, suggesting a possibility to treat inflammatory diseases via maintaining mitochondrial homeostasis.

The glucocorticoids prednisone and dexamethasone differentially modulate T cell function in response to anti-PD-1 and anti-CTLA-4 immune checkpoint blockade.

On-treatment steroids for countering immune checkpoint inhibitor-induced inflammatory responses (irAEs) are a hallmark of cancer immunotherapy. However, the suppressive nature of steroids has raised questions regarding their ability to compromise the function of the 'proliferative burst' of effector T cells induced by immune checkpoint antibodies. We investigated the effector functions and the co-inhibitory receptor profile of stimulated peripheral blood mononuclear cells (PBMCs) pre-treated with prednisone and dexamethasone alone or in the presence of anti-PD-1/CTLA-4 antibodies. Also, clinical analysis of a patient who exhibited irAEs following combination (anti-PD-1/CTLA-4) in the presence of glucocorticoids was done. We found that prednisone in contrast to dexamethasone did not compromise T cell cytokine production (IL-2, IFN-γ and TNF-α) and proliferation in the absence or presence of anti-PD-1/CTLA-4 antibodies, when a physiological concentration was used. Neither single prednisone treatment nor co-treatment with checkpoint inhibitors impacted the expression of co-inhibitory receptors PD-1, CTLA-4, TIM-3 and LAG-3. In contrast, dexamethasone treatment promoted downregulation of LAG-3 expression by T cells. In addition, co-treatment of PD-1 + Jurkat cells with prednisone and/or dexamethasone with anti-PD-1 before stimulation significantly reduced SHP-2 phosphorylation, indicative of increased T cell function. Our findings hereby demonstrate a differential steroid effect on T cell function, which should be taken into consideration for patients undergoing immunotherapy. Also, the clinical analysis of a patient who exhibited irAEs following combination (anti-PD-1/CTLA-4) therapy indicated complete metabolic response in the presence of glucocorticoids. Therefore, concomitant use of prednisone does not appear to interfere with the function of immune checkpoint blockade.

Euxanthone represses the proliferation, migration, and invasion of glioblastoma cells by modulating STAT3/SHP-1 signaling.

Glioblastoma is one of the most prevalent primary malignant brain tumors. Glioblastoma often develops resistance to conventional chemoradiotherapy, and thus, new ways to treat glioblastoma are urgently required. The aim of this study was to investigate the effect of euxanthone on the anticancer activities of glioblastoma and its potential mechanism. The U87 and U251 glioblastoma cell lines were cultured in media containing different concentrations of euxanthone. CCK-8 and colony formation assay were used to evaluate the cell proliferation. Cell migration and invasion were evaluated by wound healing and Transwell assays. Flow cytometry was used to assess the cell cycle and apoptosis rate. TUNEL assay was also employed to evaluate the apoptosis rate. Gene and protein expressions were determined by RT-qPCR and western blotting, respectively. A xenograft model was established to evaluate the efficacy of euxanthone in vivo. Euxanthone significantly repressed cell viability, migration, invasion, and epithelial-to-mesenchymal transition of U87 and U251 cells; and increased the rate of apoptosis. Western blotting results revealed that the levels of p21, p27, cleaved caspase-3, Bax, TIMP-3, and E-cadherin were upregulated while, the levels of CDK4, CDK6, pro-caspase-3, Bcl-2, MMP-2, MMP-9, N-cadherin, and Vimentin were downregulated by euxanthone. In addition, the expression of p-STAT3 was decreased, while the expression of SHP-1 was upregulated by euxanthone. We proposed that euxanthone could repress the malignant behavior of glioblastoma cells through suppression of STAT3 phosphorylation and activation of SHP-1. Further, in vivo data demonstrated that euxanthone repressed tumor growth and promoted apoptosis.

RMC-4550, an Allosteric Inhibitor of SHP2, Displays Therapeutic Efficacy in Pre-Clinical Models of Myeloproliferative Neoplasms

Philadelphia chromosome negative myeloproliferative neoplasms (MPNs) are JAK2-driven disorders resulting from mutations in JAK2, MPL, or CALR. Ruxolitinib, the only FDA-approved JAK2 inhibitor for MPNs, alleviates patient symptomology and improves quality of life, but has little effect on reducing mutant allele burden. This persistent survival of MPN cells in the face of ruxolitinib, as well as other JAK2 inhibitors that have been clinically tested, is a major clinical bottleneck to the development of an effective targeted therapy for MPN patients. Identifying new therapeutic targets which play critical roles in MPN cells and/or in JAK2 inhibitor persistence may lead to improved MPN therapies. SHP2 is an oncogenic tyrosine phosphatase that is an effector of growth factor and cytokine receptor signaling. SHP2 plays a critical role in the activation of the RAS-ERK pathway and regulates JAK-STAT signaling via numerous phosphatase-dependent mechanisms. Activating mutations of SHP2(PTPN11) have been identified in leukemia, including 8% of MPN patients whose disease progressed to acute myeloid leukemia (AML). In addition, SHP2 has been shown to mediate adaptive resistance to targeted therapies in several cancers. Given the role of SHP2 in cytokine and JAK-STAT signaling, we envisaged a potential role of SHP2 in MPN cell growth and/or survival and ruxolitinib persistence. Treatment of JAK2-V617F-driven MPN model cell lines (UKE1, SET2, and BaF3-JAK2-V617F) with ruxolitinib blocked constitutive tyrosine phosphorylation of SHP2, including phosphorylation of Y542, a marker for activated SHP2. This phosphorylation, however, was restored in ruxolitinib persistent cells. Combination treatment of the allosteric SHP2 inhibitor RMC-4550 (Revolution Medicines) with ruxolitinib prevented the development of ruxolitinib persistent cells and pre-established persistent cells remained sensitive to SHP2 inhibition. RMC-4550 treatment led to significantly reduced levels of pERK consistent with the role of SHP2 in RAS signaling. Interestingly, pERK levels in persistent cells were more sensitive to SHP2 inhibition compared to drug naïve cells suggesting pERK was more dependent on SHP2 in ruxolitinib persistent cells. SHP2 inhibitor treatment increased pSTAT5(Y694) in drug naïve cells but this increase was not observed in similarly treated persistent cells. Furthermore, while ruxolitinib inhibited pERK levels in UKE1 and SET2 cells, pERK levels recovered within 24 hrs of treatment. SHP2 inhibition prevented the recovery of pERK in the presence of ruxolitinib. Collectively, these data suggest that signaling pathways in MPN cells treated with ruxolitinib can become rewired, gaining greater dependence on SHP2, concomitant with sustained pERK and cell survival/growth. Interestingly, we identified a known activating SHP2 mutation (F71L) in UKE1 cells obtained from two independent sources - consistent with the presence of PTPN11 mutations in post-MPN AML. The persistent survival of UKE1 cells in ruxolitinib was antagonized by CRISPR-mediated reduction of SHP2 expression, providing further evidence that SHP2 contributes to ruxolitinib persistence. To assess the effects of a SHP2 inhibitor on MPN progression in vivo, we employed the MPLW515Lbone marrow transplant mouse model of MPN. Initial assessment of therapeutic treatment of mice with an established MPN phenotype indicated that once daily treatment of RMC-4550 (10 or 30 mg/kg) antagonized the MPN phenotype. Complete blood counts indicated a significant reduction in white blood cells, monocytes, and neutrophils compared to vehicle treated mice, while flow cytometry analysis indicated RMC-4550 diminished CD11b+ cell numbers to near that observed in mice transplanted with MPLWT-transduced bone marrow. RMC-4550 improved the overall health of diseased mice, as indicated by increased weight, and significantly reduced organomegaly of the spleen and liver compared to vehicle treated MPN mice. Finally, erythropoietin independent erythroid colony formation of JAK2V617F-positive MPN patient cells was suppressed following SHP2 inhibition, which synergized or enhanced the inhibition induced by ruxolitinib in this assay. In summary, our results suggest that SHP2 inhibition may represent a potential MPN therapy in both ruxolitinib naïve and resistant patients and is an attractive therapeutic target for future clinical investigation. Disclosures Epling-Burnette: Incyte Corporation: Research Funding; Forma Therapeutics: Research Funding; Celgene Corporation: Patents & Royalties, Research Funding. Reuther:Incyte Corporation: Research Funding.

Identifying Novel Mechanisms of Resistance to Tyrosine Kinase Inhibitors in Anaplastic Large Cell Lymphoma

INTRODUCTION: Anaplastic large cell lymphomas (ALCL) frequently carry oncogenic fusion proteins as a consequence of chromosomal translocations of the anaplastic lymphoma kinase (ALK) gene. The fusion protein resulting from the translocation between dimerization domain of nucleophosmin (NPM) and intracellular tyrosine kinase domain of ALK activates several signaling pathways, promoting cell growth, transformation, migration, and survival of the cells. Chemotherapy has been used as a standard treatment approach for ALCL patients, yet about 30% of patients relapse. A more specific treatment method is based on targeting ALK tyrosine kinase using tyrosine kinase inhibitors (TKIs). Crizotinib is an ALK TKI that is approved for the treatment of ALK-rearranged lung cancer and has received Breakthrough Therapy designation for lymphoma because of its high activity in chemo refractory ALCL. However, as for lung cancer, also ALCL patient develop crizotinib resistance due to ALK mutations or unknown mechanisms. In this study, we aimed at elucidating unknown by-pass mechanisms of crizotinib resistance in ALCL. METHODS: We used Genome-wide CRISPR-Cas9 Knockout Screening (GeCKO) to identify candidate genes that contribute to resistance to crizotinib. Four different ALCL cell lines were infected with Lenti-GeCKO libraries. After treatment with crizotinib for 14 days, DNA isolation and next generation sequencing was performed on crizotinib resistant cells to identify candidate genes depleted by the GeCKO screening. Top candidates were selected for validation assays and further analyses. RESULTS: We identified two phosphatases, PTPN1 and PTPN2, in different ALCL cell lines as consistent top hits. Functional validation of these candidate genes showed that single loss of either PTPN1 or PTPN2 generate immediate resistance to crizotinib in ALCL cell lines. Analysis of downstream pathways showed that while loss of PTPN1 activates primarily the MAPK pathway, loss of PTPN2 promotes persistent STAT3 and MAPK activation in ALK inhibited cells. Remarkably, in PTPN1 knockout cells we observed hyperactivation of SHP2, an oncogenic phosphatase that positively regulates the RAS-MAPK pathway. On the other hand, over-expression of PTPN1 and PTPN2 partially inhibited SHP2 phosphorylation. A treatment that combined crizotinib and the recently developed SHP2 inhibitor completely blocked the sustained ERK phosphorylation and reverted the crizotinib resistance observed in PTPN1 and PTPN2 deficient lymphoma cells. CONCLUSIONS: GeCKO library screen identified PTPN1 and PTPN2 as specific genes that mediate crizotinib resistance in ALCL cell lines. Loss of PTPN1 and PTPN2 drives resistance by activating MAPK and/or JAK-STAT pathway. Combined inhibition of SHP2 is a potent therapeutic approach to overcome resistance to crizotinib in ALCL cells. Disclosures Gambacorti-Passerini: Bristol-Meyers Squibb: Consultancy; Pfizer: Honoraria, Research Funding.

Perlecan regulates pericyte dynamics in the maintenance and repair of the blood-brain barrier.

Ischemic stroke causes blood-brain barrier (BBB) breakdown due to significant damage to the integrity of BBB components. Recent studies have highlighted the importance of pericytes in the repair process of BBB functions triggered by PDGFRβ up-regulation. Here, we show that perlecan, a major heparan sulfate proteoglycan of basement membranes, aids in BBB maintenance and repair through pericyte interactions. Using a transient middle cerebral artery occlusion model, we found larger infarct volumes and more BBB leakage in conditional perlecan (Hspg2)-deficient (Hspg2 - / - -TG) mice than in control mice. Control mice showed increased numbers of pericytes in the ischemic lesion, whereas Hspg2 - / - -TG mice did not. At the mechanistic level, pericytes attached to recombinant perlecan C-terminal domain V (perlecan DV, endorepellin). Perlecan DV enhanced the PDGF-BB-induced phosphorylation of PDGFRβ, SHP-2, and FAK partially through integrin α5β1 and promoted pericyte migration. Perlecan therefore appears to regulate pericyte recruitment through the cooperative functioning of PDGFRβ and integrin α5β1 to support BBB maintenance and repair following ischemic stroke.

Human TIGIT on porcine aortic endothelial cells suppresses xenogeneic macrophage-mediated cytotoxicity

PurposeThe delayed rejection caused by strong cell-mediated innate and adaptive xenogeneic immune responses continues to be a major obstacle.Therefore, suppressing macrophage function could be effective in avoiding this type of rejection. In this study, the suppression of T-cell immunoglobulin and ITIM domain (TIGIT) function against macrophage-mediated xenogeneic rejection was investigated. Material and methodsNaïve porcine aortic endothelial cell (PAEC) and PAEC transfectant with TIGIT (PAEC/TIGIT) were co-cultured with M1 macrophages, and the degree of cytotoxicity was determined by a counting beads assay. The anti/pro-inflammatory gene expression was determined by RT-PCR and the phosphorylated SHP-1 in the macrophages after co-culturing with PAEC or PAEC/TIGIT was evaluated by western blotting. ResultsCD155 was expressed at essentially equal levels on both M1 and M2 macrophages, whereas TIGIT was highly expressed on M2 macrophages but not in M1 macrophages. TIGIT on PAEC significantly reduced the cytotoxicity of M1 macrophages but no significant suppression of phagocytosis was detected. TIGIT also caused a decrease in the expression of pro-inflammatory cytokines, namely TNFα, IL-1β and IL-12 in M1 macrophages. Furthermore, PAEC/TIGIT caused a significant increase in phosphorylated SHP-1 in M1 macrophages compared to PAEC. ConclusionThe findings of this study indicate that TIGIT suppresses xenogeneic M1 macrophage-induced cytotoxicity, probably at least in part, via the phosphorylation of SHP-1. In addition, the reduced expression of some pro-inflammatory cytokines, namely TNFα, IL-1β and IL-12, was observed in M1 macrophages that had been cultured with PAEC/TIGIT.

Siglec-7 on peripheral blood eosinophils: Surface expression and function.

Siglec-7 is an inhibitory receptor (IR) expressed on human blood eosinophils. Whereas activation of other IRs, including Siglec-8 and CD300a, has been shown to downregulate eosinophil function, little is known about the role of Siglec-7 on human eosinophils. To examine Siglec-7 expression and function in eosinophils from normal (ND) and eosinophilic (EO) donors. Eosinophil expression of Siglec-7 was quantified by flow cytometry and quantitative PCR. Soluble Siglec-7 (sSiglec-7) levels were measured by ELISA in serum. The effect of Siglec-7 on eosinophil viability and degranulation was assessed invitro by AnnexinV-FITC/7-AAD staining and by measuring GM-CSF-induced mediator release in culture supernatants. Signal transduction was studied by Western blot. Siglec-7 was expressed exvivo on blood eosinophils from all eosinophilic and normal individuals studied. Siglec-7 surface, but not SIGLEC-7mRNA expression, was correlated with absolute eosinophil count (AEC). Siglec-7 was upregulated on purified eosinophils after invitro stimulation with GM-CSF or IL-5. Serum sSiglec-7 was detectable in 133/144 subjects tested and correlated with AEC. Siglec-7 cross-linking inhibited GM-CSF-induced release of eosinophil peroxidase, TNF-α, and IL-8 (n=7-8) but did not promote eosinophil apoptosis (n=5). Finally, Siglec-7 cross-linking on GM-CSF-activated eosinophils induced phosphorylation of SHP-1 and de-phosphorylation of ERK1/2 and p38. Siglec-7 is constitutively expressed on human eosinophils and downmodulates eosinophil activation. Targeting of Siglec-7 on eosinophils might enhance treatment efficacy in eosinophil-driven disorders. Conversely, therapeutic interventions that inhibit Siglec-7 could have unanticipated consequences and promote eosinophilic inflammation.