Tyrosine phosphatase SHP2 inhibitors in tumor-targeted therapies

Inhibiting SHP2 reduces glycolysis, promotes microglial M1 polarization, and alleviates secondary inflammation following spinal cord injury in a mouse model

JOURNAL/nrgr/04.03/01300535-202503000-00030/figure1/v/2024-06-17T092413Z/r/image-tiff Reducing the secondary inflammatory response, which is partly mediated by microglia, is a key focus in the treatment of spinal cord injury. Src homology 2-containing protein tyrosine phosphatase 2 (SHP2), encoded by PTPN11, is widely expressed in the human body and plays a role in inflammation through various mechanisms. Therefore, SHP2 is considered a potential target for the treatment of inflammation-related diseases. However, its role in secondary inflammation after spinal cord injury remains unclear. In this study, SHP2 was found to be abundantly expressed in microglia at the site of spinal cord injury. Inhibition of SHP2 expression using siRNA and SHP2 inhibitors attenuated the microglial inflammatory response in an in vitro lipopolysaccharide-induced model of inflammation. Notably, after treatment with SHP2 inhibitors, mice with spinal cord injury exhibited significantly improved hind limb locomotor function and reduced residual urine volume in the bladder. Subsequent in vitro experiments showed that, in microglia stimulated with lipopolysaccharide, inhibiting SHP2 expression promoted M2 polarization and inhibited M1 polarization. Finally, a co-culture experiment was conducted to assess the effect of microglia treated with SHP2 inhibitors on neuronal cells. The results demonstrated that inflammatory factors produced by microglia promoted neuronal apoptosis, while inhibiting SHP2 expression mitigated these effects. Collectively, our findings suggest that SHP2 enhances secondary inflammation and neuronal damage subsequent to spinal cord injury by modulating microglial phenotype. Therefore, inhibiting SHP2 alleviates the inflammatory response in mice with spinal cord injury and promotes functional recovery postinjury.

Advances in SHP2 tunnel allosteric inhibitors and bifunctional molecules

SHP2 is a non-receptor tyrosine phosphatase encoded by PTPN11, which performs the functions of regulating cell proliferation, differentiation, apoptosis, and survival through removing tyrosine phosphorylation and modulating various signaling pathways. The overexpression of SHP2 or its mutations is related to developmental diseases and several cancers. Numerous allosteric inhibitors with striking inhibitory potency against SHP2 allosteric pockets have recently been identified, and several SHP2 tunnel allosteric inhibitors have been applied in clinical trials to treat cancers. However, based on clinical results, the efficacy of single-agent treatments has been proven to be suboptimal. Most clinical trials involving SHP2 inhibitors have adopted drug combination strategies. This review briefly discusses the research progress on SHP2 allosteric inhibitors and pathway-dependent drug combination strategies for SHP2 in cancer therapy. In addition, we summarize the current bifunctional molecules of SHP2 and elaborate on the design and structural optimization strategies of these bifunctional molecules in detail, offering further direction for the research on novel SHP2 inhibitors.

Discovery of Novel Allosteric SHP2 Inhibitor Using Pharmacophore-Based Virtual Screening, Molecular Docking, Molecular Dynamics Simulation, and Principal Component Analysis

SHP2 belongs to a cytoplasmic non-receptor protein tyrosine phosphatase class. It plays a critical role in the development of various cancers, such as gastric cancer, leukemia, and breast cancer. Thus, SHP2 has gained the interest of researchers as a potential target for inhibiting tumor cell proliferation in SHP2-dependent cancers. This study employed pharmacophore-based virtual screening, molecular docking, molecular dynamic (MD) simulations, MM/PBSA, and principal component analysis (PCA), followed by ADME prediction. We selected three potential hits from a collective database of more than one million chemical compounds. The stability of these selected hit-protein complexes was analyzed using 500 ns MD simulations and binding free energy calculations. The identified hits Lig_1, Lig_6, and Lig_14 demonstrated binding free energies of -161.49 kJ/mol, -151.28 kJ/mol, and -107.13 kJ/mol, respectively, compared to the reference molecule (SHP099) with a ΔG of -71.48 kJ/mol. Our results showed that the identified compounds could be used as promising candidates for selective SHP2 allosteric inhibition in cancer.

Protein tyrosine phosphatases: emerging role in cancer therapy resistance

BACKGROUND

Tyrosine phosphorylation of intracellular proteins is a post-translational modification that plays a regulatory role in signal transduction during cellular events. Dephosphorylation of signal transduction proteins caused by protein tyrosine phosphatases (PTPs) contributed their role as a convergent node to mediate cross-talk between signaling pathways. In the context of cancer, PTP-mediated pathways have been identified as signaling hubs that enabled cancer cells to mitigate stress induced by clinical therapy. This is achieved by the promotion of constitutive activation of growth-stimulatory signaling pathways or modulation of the immune-suppressive tumor microenvironment. Preclinical evidences suggested that anticancer drugs will release their greatest therapeutic potency when combined with PTP inhibitors, reversing drug resistance that was responsible for clinical failures during cancer therapy.

AREAS COVERED

This review aimed to elaborate recent insights that supported the involvement of PTP-mediated pathways in the development of resistance to targeted therapy and immune-checkpoint therapy.

EXPERT OPINION

This review proposed the notion of PTP inhibition in anticancer combination therapy as a potential strategy in clinic to achieve long-term tumor regression. Ongoing clinical trials are currently underway to assess the safety and efficacy of combination therapy in advanced-stage tumors.

Regulatory mechanisms of PD-1/PD-L1 in cancers

Immune evasion contributes to cancer growth and progression. Cancer cells have the ability to activate different immune checkpoint pathways that harbor immunosuppressive functions. The programmed death protein 1 (PD-1) and programmed cell death ligands (PD-Ls) are considered to be the major immune checkpoint molecules. The interaction of PD-1 and PD-L1 negatively regulates adaptive immune response mainly by inhibiting the activity of effector T cells while enhancing the function of immunosuppressive regulatory T cells (Tregs), largely contributing to the maintenance of immune homeostasis that prevents dysregulated immunity and harmful immune responses. However, cancer cells exploit the PD-1/PD-L1 axis to cause immune escape in cancer development and progression. Blockade of PD-1/PD-L1 by neutralizing antibodies restores T cells activity and enhances anti-tumor immunity, achieving remarkable success in cancer therapy. Therefore, the regulatory mechanisms of PD-1/PD-L1 in cancers have attracted an increasing attention. This article aims to provide a comprehensive review of the roles of the PD-1/PD-L1 signaling in human autoimmune diseases and cancers. We summarize all aspects of regulatory mechanisms underlying the expression and activity of PD-1 and PD-L1 in cancers, including genetic, epigenetic, post-transcriptional and post-translational regulatory mechanisms. In addition, we further summarize the progress in clinical research on the antitumor effects of targeting PD-1/PD-L1 antibodies alone and in combination with other therapeutic approaches, providing new strategies for finding new tumor markers and developing combined therapeutic approaches.

Targeting RAF dimers in RAS mutant tumors: From biology to clinic

RAS mutations occur in approximately 30% of tumors worldwide and have a poor prognosis due to limited therapies. Covalent targeting of KRAS G12C has achieved significant success in recent years, but there is still a lack of efficient therapeutic approaches for tumors with non-G12C KRAS mutations. A highly promising approach is to target the MAPK pathway downstream of RAS, with a particular focus on RAF kinases. First-generation RAF inhibitors have been authorized to treat BRAF mutant tumors for over a decade. However, their use in RAS-mutated tumors is not recommended due to the paradoxical ERK activation mainly caused by RAF dimerization. To address the issue of RAF dimerization, type II RAF inhibitors have emerged as leading candidates. Recent clinical studies have shown the initial effectiveness of these agents against RAS mutant tumors. Promisingly, type II RAF inhibitors in combination with MEK or ERK inhibitors have demonstrated impressive efficacy in RAS mutant tumors. This review aims to clarify the importance of RAF dimerization in cellular signaling and resistance to treatment in tumors with RAS mutations, as well as recent progress in therapeutic approaches to address the problem of RAF dimerization in RAS mutant tumors.

Drugging Protein Tyrosine Phosphatases through Targeted Protein Degradation

Protein tyrosine phosphatases (PTPs) are an important class of enzymes that regulate protein tyrosine phosphorylation levels of a large variety of proteins in cells. Anomalies in protein tyrosine phosphorylation have been associated with the development of numerous human diseases, leading to a heightened interest in PTPs as promising targets for drug development. However, therapeutic targeting of PTPs has faced skepticism about their druggability. Besides the conventional small molecule inhibitors, proteolysis-targeting chimera (PROTAC) technology offers an alternative approach to target PTPs. PROTAC molecules utilize the ubiquitin-proteasome system to degrade specific proteins and have unique advantages compared with inhibitors: 1) PROTACs are highly efficient and can work at much lower concentrations than that expected based on their biophysical binding affinity; 2) PROTACs may achieve higher selectivity for the targeted protein than that dictated by their binding affinity alone; and 3) PROTACs may engage any region of the target protein in addition to the functional site. This review focuses on the latest advancement in the development of targeted PTP degraders and deliberates on the obstacles and prospective paths of harnessing this technology for therapeutic targeting of the PTPs.

Tyrosine phosphatase SHP2 aggravates tumor progression and glycolysis by dephosphorylating PKM2 in gastric cancer

Gastric cancer (GC) is among the most lethal human malignancies, yet it remains hampered by challenges in fronter of molecular-guided targeted therapy to direct clinical treatment strategies. The protein tyrosine phosphatase Src homology 2 domain-containing phosphatase 2 (SHP2) is involved in the malignant progression of GC. However, the detailed mechanisms of the posttranslational modifications of SHP2 remain poorly understood. Herein, we demonstrated that an allosteric SHP2 inhibitor, SHP099, was able to block tumor proliferation and migration of GC by dephosphorylating the pyruvate kinase M2 type (PKM2) protein. Mechanistically, we found that PKM2 is a bona fide target of SHP2. The dephosphorylation and activation of PKM2 by SHP2 are necessary to exacerbate tumor progression and GC glycolysis. Moreover, we demonstrated a strong correlation between the phosphorylation level of PKM2 and adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) in GC cells. Notably, the low phosphorylation expression of AMPK was negatively correlated with activated SHP2. Besides, we proved that cisplatin could activate SHP2 and SHP099 increased sensitivity to cisplatin in GC. Taken together, our results provide evidence that the SHP2/PKM2/AMPK axis exerts a key role in GC progression and glycolysis and could be a viable therapeutic approach for the therapy of GC.

Promising natural products targeting protein tyrosine phosphatase SHP2 for cancer therapy

The development of Src homology-2 domain containing protein tyrosine phosphatase-2 (SHP2) inhibitors is a hot spot in the research and development of antitumor drugs, which may induce immunomodulatory effects in the tumor microenvironment and participate in anti-tumor immune responses. To date, several SHP2 inhibitors have made remarkable progress and entered clinical trials for the treatment of patients with advanced solid tumors. Multiple compounds derived from natural products have been proved to influence tumor cell proliferation, apoptosis, migration and other cellular functions, modulate cell cycle and immune cell activation by regulating the function of SHP2 and its mutants. However, there is a paucity of information about their diversity, biochemistry, and therapeutic potential of targeting SHP2 in tumors. This review will provide the structure, classification, inhibitory activities, experimental models, and antitumor effects of the natural products. Notably, this review summarizes recent advance in the efficacy and pharmacological mechanism of natural products targeting SHP2 in inhibiting the various signaling pathways that regulate different cancers and thus pave the way for further development of anticancer drugs targeting SHP2.

TET3-mediated DNA demethylation modification activates SHP2 expression to promote endometrial cancer progression through the EGFR/ERK pathway

OBJECTIVE

Src homology phosphotyrosin phosphatase 2 (SHP2) has been implicated in the progression of several cancer types. However, its function in endometrial cancer (EC) remains unclear. Here, we report that the ten-eleven translocation 3 (TET3)-mediated DNA demethylation modification is responsible for the oncogenic role of SHP2 in EC and explore the detailed mechanism.

METHODS

The transcriptomic differences between EC tissues and control tissues were analyzed using bioinformatics tools, followed by protein-protein interaction network establishment. EC cells were treated with shRNA targeting SHP2 alone or in combination with isoprocurcumenol, an epidermal growth factor receptor (EGFR) signaling activator. The cell biological behavior was examined using cell counting kit-8, colony formation, flow cytometry, scratch assay, and transwell assays, and the median inhibition concentration values to medroxyprogesterone acetate/gefitinib were calculated. The binding of TET3 to the SHP2 promoter was verified. EC cells with TET3 knockdown and combined with SHP2 overexpression were selected to construct tumor xenografts in mice.

RESULTS

TET3 and SHP2 were overexpressed in EC cells. TET3 bound to the SHP2 promoter, thereby increasing the DNA hydroxymethylation modification and activating SHP2 to induce the EGFR/extracellular signal-regulated kinase (ERK) pathway. Knockdown of TET3 or SHP2 inhibited EC cell malignant aggressiveness and impaired the EGFR/ERK pathway. Silencing of TET3 inhibited the tumorigenic capacity of EC cells, and ectopic expression of SHP2 or isoprocurcumenol reversed the inhibitory effect of TET3 knockdown on the biological activity of EC cells.

CONCLUSION

TET3 promoted the DNA demethylation modification in the SHP2 promoter and activated SHP2, thus activating the EGFR/ERK pathway and leading to EC progression.

Targeting KRAS and SHP2 signaling pathways for immunomodulation and improving treatment outcomes in solid tumors

Historically, KRAS has been considered 'undruggable' inspite of being one of the most frequently altered oncogenic proteins in solid tumors, primarily due to the paucity of pharmacologically 'druggable' pockets within the mutant isoforms. However, pioneering developments in drug design capable of targeting the mutant KRAS isoforms especially KRASG12C-mutant cancers, have opened the doors for emergence of combination therapies comprising of a plethora of inhibitors targeting different signaling pathways. SHP2 signaling pathway, primarily known for activation of intracellular signaling pathways such as KRAS has come up as a potential target for such combination therapies as it emerged to be the signaling protein connecting KRAS and the immune signaling pathways and providing the link for understanding the overlapping regions of RAS/ERK/MAPK signaling cascade. Thus, SHP2 inhibitors having potent tumoricidal activity as well as role in immunomodulation have generated keen interest in researchers to explore its potential as combination therapy in KRAS mutant solid tumors. However, the excitement with these combination therapies need to overcome challenges thrown up by drug resistance and enhanced toxicity. In this review, we will discuss KRAS and SHP2 signaling pathways and their roles in immunomodulation and regulation of tumor microenvironment and also analyze the positive effects and drawbacks of the different combination therapies targeted at these signaling pathways along with their present and future potential to treat solid tumors.

Emerging therapeutic approaches of SHP2-targeted modulators

Tweetable abstract Monotherapy and combination therapy of SHP2 regulator for cancer treatment.

Targeting phosphatases: From molecule design to clinical trials

Phosphatase is a kind of enzyme that can dephosphorylate target proteins, which can be divided into serine/threonine phosphatase and tyrosine phosphatase according to its mode of action. Current evidence showed multiple phosphatases were highly correlated with diseases including various cancers, demonstrating them as potential targets. However, currently, targeting phosphatases with small molecules faces many challenges, resulting in no drug approved. In this case, phosphatases are even regarded as "undruggable" targets for a long time. Recently, a variety of strategies have been adopted in the design of small molecule inhibitors targeting phosphatases, leading many of them to enter into the clinical trials. In this review, we classified these inhibitors into 4 types, including (1) molecular glues, (2) small molecules targeting catalytic sites, (3) allosteric inhibition, and (4) bifunctional molecules (proteolysis targeting chimeras, PROTACs). These molecules with diverse strategies prove the feasibility of phosphatases as drug targets. In addition, the combination therapy of phosphatase inhibitors with other drugs has also entered clinical trials, which suggests a broad prospect. Thus, targeting phosphatases with small molecules by different strategies is emerging as a promising way in the modulation of pathogenetic phosphorylation.

Binding Free Energy Calculation Based on the Fragment Molecular Orbital Method and Its Application in Designing Novel SHP-2 Allosteric Inhibitors

The accurate prediction of binding free energy is a major challenge in structure-based drug design. Quantum mechanics (QM)-based approaches show promising potential in predicting ligand-protein binding affinity by accurately describing the behavior and structure of electrons. However, traditional QM calculations face computational limitations, hindering their practical application in drug design. Nevertheless, the fragment molecular orbital (FMO) method has gained widespread application in drug design due to its ability to reduce computational costs and achieve efficient ab initio QM calculations. Although the FMO method has demonstrated its reliability in calculating the gas phase potential energy, the binding of proteins and ligands also involves other contributing energy terms, such as solvent effects, the 'deformation energy' of a ligand's bioactive conformations, and entropy. Particularly in cases involving ionized fragments, the calculation of solvation free energy becomes particularly crucial. We conducted an evaluation of some previously reported implicit solvent methods on the same data set to assess their potential for improving the performance of the FMO method. Herein, we develop a new QM-based binding free energy calculation method called FMOScore, which enhances the performance of the FMO method. The FMOScore method incorporates linear fitting of various terms, including gas-phase potential energy, deformation energy, and solvation free energy. Compared to other widely used traditional prediction methods such as FEP+, MM/PBSA, MM/GBSA, and Autodock vina, FMOScore showed good performance in prediction accuracies. By constructing a retrospective case study, it was observed that incorporating calculations for solvation free energy and deformation energy can further enhance the precision of FMO predictions for binding affinity. Furthermore, using FMOScore-guided lead optimization against Src homology-2-containing protein tyrosine phosphatase 2 (SHP-2), we discovered a novel and potent allosteric SHP-2 inhibitor (compound 8).

Astragalus Polysaccharide Alleviates Ulcerative Colitis by Regulating the Balance of mTh17/mTreg Cells through TIGIT/CD155 Signaling

The balance between memory Th17 cells (mTh17) and memory Treg cells (mTreg) plays a key role in the pathogenesis of ulcerative colitis (UC), and TIGIT signaling is involved in the differentiation of mTh17/mTreg cells. Astragalus polysaccharide (APS) has good immunomodulatory and anti-inflammatory effects. Here, the regulatory effects and potential mechanisms of APS on mTh17/mTreg cells in UC are explored. A UC model was induced with dextran sulfate sodium (DSS) and treated simultaneously with APS (200 mg/kg/day) for 10 days. After APS treatment, the mice showed a significant increase in colonic length and a significant decrease in colonic weight, colonic weight index and colonic weight/colonic length, and more intact mucosa and lighter inflammatory cell infiltration. Notably, APS significantly down-regulated the percentages of Th17 (CD4+CCR6+), cmTh17 (CD4+CCR7+CCR6+) and emTh17 (CD4+CCR7-CCR6+) cells and significantly up-regulated the percentages of cmTreg (CD4+CCR7+Foxp3+) and emTreg (CD4+CCR7-Foxp3+) cells in the mesenteric lymph nodes of the colitis mice. Importantly, APS reversed the expression changes in the TIGIT molecule on mTh17/mTreg cells in the colitis mice with fewer CD4+CCR6+TIGIT+, CD4+CCR7-CCR6+TIGIT+ and CD4+CCR7-CCR6+TIGIT+ cells and more CD4+Foxp3+TIGIT+, CD4+CCR7-Foxp3+TIGIT+ and CD4+CCR7-Foxp3+TIGIT+ cells. Meanwhile, APS significantly inhibited the protein expression of the TIGIT ligands CD155, CD113 and CD112 and downstream proteins PI3K and AKT in the colon tissues of the colitis mice. In conclusion, APS effectively alleviated DSS-induced UC in mice by regulating the balance between mTh17/mTreg cells, which was mainly achieved through regulation of the TIGIT/CD155 signaling pathway.

Protein Tyrosine Phosphatase SHP2 in Macrophages Acts as an Antiatherosclerotic Regulator in Mice

BACKGROUND

Macrophages have versatile roles in atherosclerosis. SHP2 (Src homology 2 containing protein tyrosine phosphatase 2) has been demonstrated to play a critical role in regulating macrophage activation. However, the mechanism of SHP2 regulation of macrophage function in an atherosclerotic microenvironment remains unknown.

METHODS

APOE (apolipoprotein E) or LDLR (low-density lipoprotein receptor) null mice treated with SHP099 were fed a Western diet for 8 weeks, while Shp2MKO:ApoE-/- or Shp2MKO:Ldlr-/- mice and exo-AAV8-SHP2E76K/ApoE-/- mice were fed a Western diet for 12 weeks. In vitro, levels of proinflammatory factors and phagocytic function were then studied in mouse peritoneal macrophages. RNA sequencing was used to identify PPARγ (peroxisome proliferative activated receptor γ) as the key downstream molecule. A PPARγ agonist was used to rescue the phenotypes observed in SHP2-deleted mice.

RESULTS

Pharmacological inhibition and selective deletion in macrophages of SHP2 aggravated atherosclerosis in APOE and LDLR null mice with increased plaque macrophages and apoptotic cells. In vitro, SHP2 deficiency in APOE and LDLR null macrophages enhanced proinflammatory polarization and its efferocytosis was dramatically impaired. Conversely, the expression of gain-of-function mutation of SHP2 in mouse macrophages reduced atherosclerosis. The SHP2 agonist lovastatin repressesed macrophage inflammatory activation and enhanced efferocytosis. Mechanistically, RNA sequencing analysis identified PPARγ as a key downstream transcription factor. PPARγ was decreased in macrophages upon SHP2 deletion and inhibition. Importantly, PPARγ agonist decreased atherosclerosis in SHP2 knockout mice, restored efferocytotic defects, and reduced inflammatory activation in SHP2 deleted macrophages. PPARγ was decreased by the ubiquitin-mediated degradation upon SHP2 inhibition or deletion. Finally, we found that SHP2 was downregulated in atherosclerotic vessels.

CONCLUSIONS

Overall, SHP2 in macrophages was found to act as an antiatherosclerotic regulator by stabilizing PPARγ in APOE/LDLR null mice.

Targeting Protein Phosphatases for the Treatment of Chronic Liver Disease

There exists a huge number of patients suffering from chronic liver disease worldwide. As a disease with high incidence and mortality worldwide, strengthening the research on the pathogenesis of chronic liver disease and the development of novel drugs is an important issue related to the health of all human beings. Phosphorylation modification of proteins plays a crucial role in cellular signal transduction, and phosphatases are involved in the development of liver diseases. Therefore, this article summarized the important role of protein phosphatases in chronic liver disease with the aim of facilitating the development of drugs targeting protein phosphatases for the treatment of chronic liver disease.

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

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

Myeloid-specific knockout of SHP2 regulates PI3K/PLCγ signaling pathway to protect against early myocardial infarction injury

OBJECTIVES

To study the effects of myeloid-specific knockout of SHP2 on early myocardial infarction and explore its molecular mechanism.

METHODS

The model of myocardial infarction was established by using SHP2 in myeloid-specific knockout mice, and the effect of SHP2MAC-KO on myocardial function was detected by echocardiography. The effects of SHP2 on myocardial infarct size in myeloid-specific knockout mice was examined by TTC assay and Masson staining. Then, the detection of apoptosis was performed using TUNEL staining and inflammatory cell infiltration was observed using immunohistochemical staining. Moreover, macrophages in mouse hearts were selected by Flow Cytometry and treated with PI3K inhibitors respectively. Western blotting was then used to detect protein expression of p-SHP2 and PI3K/PLCγ signaling pathway. The phagocytic ability of cells was detected by endocytosis test, and the expression of inflammatory cytokines was detected by ELISA.

RESULTS

Specific knockout of SHP2 in mice with myocardial infarction can improve the cardiac function, decrease infarct size, and reduce apoptosis as well as inflammatory cell infiltration. It also can mediate the PI3K/PLCγ signaling pathway in macrophages, which in turn enhances the endocytosis of macrophages and reduces the expression of inflammatory cytokines in macrophages.

CONCLUSIONS

Myeloid-specific knockout of SHP2 regulates PI3K/PLCγ signaling pathway to protect against early myocardial infarction injury.

Role of SHP2 (PTPN11) in glycoprotein VI-dependent thrombus formation: Improved platelet responsiveness by the allosteric drug SHP099 in Noonan syndrome patients

INTRODUCTION

The protein tyrosine phosphatase SHP2 (PTPN11) is a negative regulator of glycoprotein VI (GPVI)-induced platelet signal under certain conditions. Clinical trials with derivatives of the allosteric drug SHP099, inhibiting SHP2, are ongoing as potential therapy for solid cancers. Gain-of-function mutations of the PTPN11 gene are observed in part of the patients with the Noonan syndrome, associated with a mild bleeding disorder. Assessment of the effects of SHP2 inhibition in platelets from controls and Noonan syndrome patients.

MATERIALS AND METHODS

Washed human platelets were incubated with SHP099 and stimulated with collagen-related peptide (CRP) for stirred aggregation and flow cytometric measurements. Whole-blood microfluidics assays using a dosed collagen and tissue factor coating were performed to assess shear-dependent thrombus and fibrin formation. Effects on clot formation were evaluated by thromboelastometry.

RESULTS

Pharmacological inhibition of SHP2 did not alter GPVI-dependent platelet aggregation under stirring, but it enhanced integrin αIIbβ3 activation in response to CRP. Using whole-blood microfluidics, SHP099 increased the thrombus buildup on collagen surfaces. In the presence of tissue factor and coagulation, SHP099 increased thrombus size and reduced time to fibrin formation. Blood from PTPN11-mutated Noonan syndrome patients, with low platelet responsiveness, after ex vivo treatment with SHP099 showed a normalized platelet function. In thromboelastometry, SHP2 inhibition tended to increase tissue factor-induced blood clotting profiles with tranexamic acid, preventing fibrinolysis.

CONCLUSION

Pharmacological inhibition of SHP2 by the allosteric drug SHP099 enhances GPVI-induced platelet activation under shear conditions with a potential to improve platelet functions of Noonan syndrome patients.

SHP2 participates in decidualization by activating ERK to maintain normal nuclear localization of progesterone receptor

In brief

The establishment and maintenance of embryo implantation and pregnancy require decidualization of endometrial stromal cells. This paper reveals that SHP2 ensures the correct subcellular localization of progesterone receptor, thereby safeguarding the process of decidualization.

Abstract

Decidualization is the process of conversion of endometrial stromal cells into decidual stromal cells, which is caused by progesterone production that begins during the luteal phase of the menstrual cycle and then increases throughout pregnancy dedicated to support embryonic development. Decidualization deficiency is closely associated with various pregnancy complications, such as recurrent miscarriage (RM). Here, we reported that Src-homology-2-containing phospho-tyrosine phosphatase (SHP2), a key regulator in the signal transduction process downstream of various receptors, plays an indispensable role in decidualization. SHP2 expression was upregulated during decidualization. SHP2 inhibitor RMC-4550 and shRNA-mediated SHP2 reduction resulted in a decreased level of phosphorylation of ERK and aberrant cytoplasmic localization of progesterone receptor (PR), coinciding with reduced expression of IGFBP1 and various other target genes of decidualization. Solely inhibiting ERK activity recapitulated these observations. Administration of RMC-4550 led to decidualization deficiency and embryo absorption in mice. Moreover, reduced expression of SHP2 was detected in the decidua of RM patients. Our results revealed that SHP2 is key to PR's nuclear localization, thereby indispensable for decidualization and that reduced expression of SHP2 might be engaged in the pathogenesis of RM.

Setting sail: Maneuvering SHP2 activity and its effects in cancer

Since the discovery of tyrosine phosphorylation being a critical modulator of cancer signaling, proteins regulating phosphotyrosine levels in cells have fast become targets of therapeutic intervention. The nonreceptor protein tyrosine phosphatase (PTP) coded by the PTPN11 gene "SHP2" integrates phosphotyrosine signaling from growth factor receptors into the RAS/RAF/ERK pathway and is centrally positioned in processes regulating cell development and oncogenic transformation. Dysregulation of SHP2 expression or activity is linked to tumorigenesis and developmental defects. Even as a compelling anti-cancer target, SHP2 was considered "undruggable" for a long time owing to its conserved catalytic PTP domain that evaded drug development. Recently, SHP2 has risen from the "undruggable curse" with the discovery of small molecules that manipulate its intrinsic allostery for effective inhibition. SHP2's unique domain arrangement and conformation(s) allow for a truly novel paradigm of inhibitor development relying on skillful targeting of noncatalytic sites on proteins. In this review we summarize the biological functions, signaling properties, structural attributes, allostery and inhibitors of SHP2.

Discovery of a potent and selective allosteric inhibitor targeting the SHP2 tunnel site for RTK-driven cancer treatment

Src homology 2 domain-containing phosphatase 2 (SHP2) is a cytoplasmic protein tyrosine phosphatase (PTP) that regulates signal transduction of receptor tyrosine kinases (RTKs). Abnormal SHP2 activity is associated with tumorigenesis and metastasis. Because SHP2 contains multiple allosteric sites, identifying inhibitors at specific allosteric binding sites remains challenging. Here, we used structure-based virtual screening to directly search for the SHP2 "tunnel site" allosteric inhibitor. A novel hit (70) was identified as the SHP2 allosteric inhibitor with an IC₅₀ of 10.2 μM against full-length SHP2. Derivatization of hit compound 70 using molecular modeling-guided structure-based modification allowed the discovery of an effective and selective SHP2 inhibitor, compound 129, with 122-fold improved potency compared to the hit. Further studies revealed that 129 effectively inhibited signaling in multiple RTK-driven cancers and RTK inhibitor-resistant cancer cells. Remarkably, 129 was orally bioavailable (F = 55%) and significantly inhibited tumor growth in haematological malignancy. Taken together, compound 129 developed in this study may serve as a promising lead or candidate for cancers bearing RTK oncogenic drivers and SHP2-related diseases.

SHP2 inhibition mitigates adaptive resistance to MEK inhibitors in KRAS-mutant gastric cancer through the suppression of KSR1 activity

Despite the promising antitumor activity of RAF/MEK inhibitors for RAS-driven cancers, not all patients respond to these therapies. Adaptive resistance has been reported as a major culprit in non-responders, which can be reversed by SHP2 inhibitors (SHP2is) in multiple cancer cells; however, the underlying mechanisms remain unknown. In this study, we found that KRAS-mutant gastric cancer cells respond to MEK inhibitors (MEKis) with adaptive resistance. Markedly, SHP2 activation accompanied by ERK signaling restoration in MEKi-treated cells, and a MEKi and SHP2i combination had a synergistic effect on downstream signaling blockade. In vivo, SHP099 combined with AZD6244 (selumetinib) was highly efficacious for the treatment of xenografts. Mechanistically, SHP2 was found to interact with the scaffold protein KSR1 through its protein tyrosine phosphatase domain. KSR1 knockdown sensitized cells to AZD6244, whereas a KSR1 activating mutation (S269A) diminished the synergistic anti-proliferative effect of SHP2i and MEKi. Interestingly, activated SHP2, during adaptive resistance to MEKis, impaired the interaction with KSR1, activating KSR1 to promote MAPK signaling. In conclusion, SHP2 promotes adaptive resistance to MEKis by activating KSR1; selumetinib combined with SHP099 might be an available therapeutic strategy for KRAS-mutant gastric cancers.

Identification of linderalactone as a natural inhibitor of SHP2 to ameliorate CCl4-induced liver fibrosis

Liver fibrosis is characterised by the activation of hepatic stellate cells (HSCs) and matrix deposition. Accumulating evidence has revealed that the oncogenic protein tyrosine phosphatase Src homology 2 domain-containing phosphatase 2 (SHP2) acts as a therapeutic target of fibrosis. Although several SHP2 inhibitors have reached early clinical trials, there are currently no FDA-approved drugs that target SHP2. In this study, we aimed to identify novel SHP2 inhibitors from an in-house natural product library to treat liver fibrosis. Out of the screened 800 compounds, a furanogermacrane sesquiterpene, linderalactone (LIN), significantly inhibited SHP2 dephosphorylation activity in vitro. Cross-validated enzymatic assays, bio-layer interferometry (BLI) assays, and site-directed mutagenesis were used to confirm that LIN directly binds to the catalytic PTP domain of SHP2. In vivo administration of LIN significantly ameliorated carbon tetrachloride (CCl₄)-induced HSC activation and liver fibrosis by inhibiting the TGFβ/Smad3 pathway. Thus, LIN or its derivatives could be considered potential therapeutic agents against SHP2-related diseases, such as liver fibrosis or NASH.

Inhibition of SHP2 by the Small Molecule Drug SHP099 Prevents Lipopolysaccharide-Induced Acute Lung Injury in Mice

Excessive pulmonary inflammation in acute lung injury (ALI) causes high patient mortality. Anti-inflammatory therapy, combined with infection resistance, can help to prevent ALI and save lives. The expression of Src homology-2 domain-containing protein tyrosine phosphatase 2 (SHP2) was found to be significantly higher in macrophages and lung tissues with ALI, and SHP2-associated MAPK pathways were activated by lipopolysaccharide (LPS). The knockdown of the SHP2 gene suppressed the LPS-induced release of inflammatory factors and the phosphorylation of regulators in the NF-κB pathways in macrophages. Our findings showed crosstalk between the LPS-induced inflammatory pathway and the SHP2-associated MAPK pathways. SHP2 inhibition could be a valuable therapeutic approach for inhibiting excessive inflammation in ALI. We discovered that giving SHP099, a specific allosteric inhibitor of SHP2, to mice with ALI and sepsis relieves ALI and significantly increases animal survival. Our study highlights the important role of SHP2 in ALI development and demonstrates the potential application of SHP099 for treating ALI.

SHP-2-induced M2 polarization of tumor associated macrophages via IL-4 regulate colorectal cancer progression

Objective

To explore the effect and molecular mechanism of Src homology region 2 domain-containing protein tyrosine phosphatase-2 (SHP-2) in tumor-associated macrophages (TAMs) repressing the migration and invasion of colorectal cancer (CRC) cells.

Methods

The relevant data sets of human colon specimens were obtained from GEO database, and then the performed correlation analysis, principal component analysis and differentially expressed gene (DEGs) analysis on the samples were conducted. GO and KEGG enrichment analysis were performed on the common DEGs, and then functional interaction prediction was performed to verify the gene regulatory circuit of SHP-2. Furthermore, western blot was used to detect the effect of low expression of SHP-2 on related proteins, including the markers of promoting M2 polarization and exosome secretion, and keys proteins of the PI3K pathway. The relationship between SHP-2 and PI3K pathway was further verified by adding PI3K inhibitor LY294002. Finally, the effect of SHP-2 on the function of colon cancer cells was confirmed by wound healing assay and Transwell assay.

Results

Through bioinformatics analysis, SHP-2 was screened as a possible key gene affecting CRC. The low expression of SHP-2 promoted the protein levels of Arginase-1 and IL-10 in IL-4 induced M2 macrophages, while inhibited the protein levels of IL-1β and TNF-α. Meanwhile, low expression of SHP-2 was found to similarly promote the expression of p-PI3K, p-AKT, and the release of exosomes. Interestingly, the promotion was suppressed after the addition of the PI3K inhibitor LY294002. In terms of cellular behavior, wound healing and transwell data showed that low expression of SHP-2 enhanced the migration and invasion abilities of CRC cells.

Conclusion

The low expression of SHP-2 induced by PHPS1 may regulate M2 polarization of TAMs and release of exosomes through PI3K/AKT pathway, thereby enhancing the migration and invasion ability of CRC cells.

Multi-omics analyses of tumor-associated immune-infiltrating cells with the novel immune checkpoint protein tyrosine phosphatase 1B (PTP1B) in extracellular matrix of brain-lower-grade-glioma (LGG) and uveal-melanoma (UVM)

Immune checkpoint inhibitors represented by PD-1 have greatly changed the way cancer is treated. In addition to PD-1, new immune checkpoints are constantly excavated to better treat cancer. Recently, protein tyrosine phosphatase 1B (PTP1B) was identified as a new immune checkpoint and played a critical role in the treatment of tumors by inhibiting the proliferation and cytotoxicity of T cells induced by tumor antigen. To explore the targeting role of PTP1B in precision tumor therapy, we deeply analyzed the expression and prognosis of PTP1B in all tumors. Survival analysis results indicated that PTP1B was highly expressed in most tumor tissues and indicated poor prognosis in acute-myeloid-leukemia (LAML), brain-lower-grade-glioma (LGG), kidney-renal clear-cell-carcinoma (KIRC) and uveal-melanoma (UVM). The methylation status of PTP1B in these four tumors exhibited hypomethylation and mutation landscape showed that PTP1B had its specific characteristics in genomic instability and heterogeneity. The homologous recombination deficiency (HRD) and loss of heterozygosity (LOH) were positive related to PTP1B expression in liver-hepatocellular-carcinoma (LIHC) and kidney-chromophobe (KICH), while the immunescore and immune infiltration displayed a significant positive correlation with PTP1B expression in LGG and UVM. Drug sensitivity tests showed that the PTP1B inhibitor MSI-1436 had a sensitivity effect suppressing tumor cell viability and suggested it enhanced the efficacy of PD-1 inhibitors in cancers.

Destabilization of the SHP2 and SHP1 protein tyrosine phosphatase domains by a non-conserved "backdoor" cysteine

Protein tyrosine phosphatases (PTPs) are critical regulators of cellular signal transduction that catalyze the hydrolytic dephosphorylation of phosphotyrosine in substrate proteins. Among several conserved features in classical PTP domains are an active-site cysteine residue that is necessary for catalysis and a "backdoor" cysteine residue that can serve to protect the active-site cysteine from irreversible oxidation. Curiously, two biologically important phosphatases, Src homology domain-containing PTPs 2 and 1 (SHP2 and SHP1), each contain an additional backdoor cysteine residue at a position of the PTP domain that is occupied by proline in almost all other classical PTPs (position 333 in human SHP2 numbering). Here we show that the presence of cysteine 333 significantly destabilizes the fold of the PTP domains in the SHPs. We find that replacement of cysteine 333 with proline confers increased thermal stability on the SHP2 and SHP1 PTP domains, as measured by temperature-dependent activity assays and differential scanning fluorimetry. Conversely, we show that substantial destabilization of the PTP-domain fold is conferred by introduction of a non-natural cysteine residue in a non-SHP PTP that contains proline at the 333 position. It has previously been suggested that the extra backdoor cysteine of the SHP PTPs may work in tandem with the conserved backdoor cysteine to provide protection from irreversible oxidative enzyme inactivation. If so, our current results suggest that, during the course of mammalian evolution, the SHP proteins have developed extra protection from oxidation at the cost of the thermal instability that is conferred by the presence of their PTP domains' second backdoor cysteine.

Harnessing the cyclization strategy for new drug discovery

The design of new ligands with high affinity and specificity against the targets of interest has been a central focus in drug discovery. As one of the most commonly used methods in drug discovery, the cyclization represents a feasible strategy to identify new lead compounds by increasing structural novelty, scaffold diversity and complexity. Such strategy could also be potentially used for the follow-on drug discovery without patent infringement. In recent years, the cyclization strategy has witnessed great success in the discovery of new lead compounds against different targets for treating various diseases. Herein, we first briefly summarize the use of the cyclization strategy in the discovery of new small-molecule lead compounds, including the proteolysis targeting chimeras (PROTAC) molecules. Particularly, we focus on four main strategies including fused ring cyclization, chain cyclization, spirocyclization and macrocyclization and highlight the use of the cyclization strategy in lead generation. Finally, the challenges including the synthetic intractability, relatively poor pharmacokinetics (PK) profiles and the absence of the structural information for rational structure-based cyclization are also briefly discussed. We hope this review, not exhaustive, could provide a timely overview on the cyclization strategy for the discovery of new lead compounds.

Building on the backbone of CD47-based therapy in cancer: Combination strategies, mechanisms, and future perspectives

Described as a "don't eat me" signal, CD47 becomes a vital immune checkpoint in cancer. Its interaction with signal regulatory protein alpha (SIRPα) prevents macrophage phagocytosis. In recent years, a growing body of evidences have unveiled that CD47-based combination therapy exhibits a superior anti-cancer effect. Latest clinical trials about CD47 have adopted the regimen of collaborating with other therapies or developing CD47-directed bispecific antibodies, indicating the combination strategy as a general trend of the future. In this review, clinical and preclinical cases about the current combination strategies targeting CD47 are collected, their underlying mechanisms of action are discussed, and ideas from future perspectives are shared.

Small molecule inhibitors targeting the cancers

Compared with traditional therapies, targeted therapy has merits in selectivity, efficacy, and tolerability. Small molecule inhibitors are one of the primary targeted therapies for cancer. Due to their advantages in a wide range of targets, convenient medication, and the ability to penetrate into the central nervous system, many efforts have been devoted to developing more small molecule inhibitors. To date, 88 small molecule inhibitors have been approved by the United States Food and Drug Administration to treat cancers. Despite remarkable progress, small molecule inhibitors in cancer treatment still face many obstacles, such as low response rate, short duration of response, toxicity, biomarkers, and resistance. To better promote the development of small molecule inhibitors targeting cancers, we comprehensively reviewed small molecule inhibitors involved in all the approved agents and pivotal drug candidates in clinical trials arranged by the signaling pathways and the classification of small molecule inhibitors. We discussed lessons learned from the development of these agents, the proper strategies to overcome resistance arising from different mechanisms, and combination therapies concerned with small molecule inhibitors. Through our review, we hoped to provide insights and perspectives for the research and development of small molecule inhibitors in cancer treatment.

A comprehensive review of SHP2 and its role in cancer

Src homology 2-containing protein tyrosine phosphatase 2 (SHP2) is a non-receptor protein tyrosine phosphatase ubiquitously expressed mainly in the cytoplasm of several tissues. SHP2 modulates diverse cell signaling events that control metabolism, cell growth, differentiation, cell migration, transcription and oncogenic transformation. It interacts with diverse molecules in the cell, and regulates key signaling events including RAS/ERK, PI3K/AKT, JAK/STAT and PD-1 pathways downstream of several receptor tyrosine kinases (RTKs) upon stimulation by growth factors and cytokines. SHP2 acts as both a phosphatase and a scaffold, and plays prominently oncogenic functions but can be tumor suppressor in a context-dependent manner. It typically acts as a positive regulator of RTKs signaling with some inhibitory functions reported as well. SHP2 expression and activity is regulated by such factors as allosteric autoinhibition, microRNAs, ubiquitination and SUMOylation. Dysregulation of SHP2 expression or activity causes many developmental diseases, and hematological and solid tumors. Moreover, upregulated SHP2 expression or activity also decreases sensitivity of cancer cells to anticancer drugs. SHP2 is now considered as a compelling anticancer drug target and several classes of SHP2 inhibitors with different mode of action are developed with some already in clinical trial phases. Moreover, novel SHP2 substrates and functions are rapidly growing both in cell and cancer. In view of this, we comprehensively and thoroughly reviewed literatures about SHP2 regulatory mechanisms, substrates and binding partners, biological functions, roles in human cancers, and different classes of small molecule inhibitors target this oncoprotein in cancer.

Methionine enkephalin inhibits colorectal cancer by remodeling the immune status of the tumor microenvironment

There is evidence that methionine enkephalin (MENK), an opioid peptide, promotes anti-tumor immune responses. In this study, the effect of MENK on colorectal cancer (CRC) and its mechanisms of action were examined in vivo. The intraperitoneal administration of 20 mg/kg MENK effectively inhibited MC38 subcutaneous colorectal tumor growth in mice. MENK inhibited tumor progression by increasing the immunogenicity and recognition of MC38 cells. MENK down-regulated the oncogene Kras and anti-apoptotic Bclxl and Bcl2, suppressed Il1b, Il6, iNOS, and Arg1 (encoding inflammatory cytokines), and increased Il17a and Il10 levels. MENK promoted a tumor suppressive state by decreasing the immune checkpoints Pd-1, Pd-l1, Lag3, Flgl1, and 2b4 in CRC. MENK also altered the immune status of the tumor immune microenvironment (TIME). It increased the infiltration of M1-type macrophages, CD8⁺T cells, and CD4⁺T cells and decreased the proportions of G-MDSCs, M-MDSCs, and M2-type macrophages. MENK accelerated CD4⁺T_EM and CD8⁺T_EM cell activation in the TIME and up-regulated IFN-γ, TNF-α, and IL-17A in CD4⁺T cells and Granzyme B in CD8⁺T cells. In addition, analyses of PD-1 and PD-L1 expression indicated that MENK promoted the anti-tumor immune response mediated by effector T cells. Finally, OGFr was up-regulated at the protein and mRNA levels by MENK, and the inhibitory effects of MENK on tumor growth were blocked by NTX, a specific blocker of OGFr. These finding indicate that MENK remodels the TIME in CRC to inhibit tumor progression by binding to OGFr. MENK is a potential therapeutic agent for CRC, especially for improving the efficacy of immunotherapy.

Targeting protein phosphatases for the treatment of inflammation-related diseases: From signaling to therapy

Inflammation is the common pathological basis of autoimmune diseases, metabolic diseases, malignant tumors, and other major chronic diseases. Inflammation plays an important role in tissue homeostasis. On one hand, inflammation can sense changes in the tissue environment, induce imbalance of tissue homeostasis, and cause tissue damage. On the other hand, inflammation can also initiate tissue damage repair and maintain normal tissue function by resolving injury and restoring homeostasis. These opposing functions emphasize the significance of accurate regulation of inflammatory homeostasis to ameliorate inflammation-related diseases. Potential mechanisms involve protein phosphorylation modifications by kinases and phosphatases, which have a crucial role in inflammatory homeostasis. The mechanisms by which many kinases resolve inflammation have been well reviewed, whereas a systematic summary of the functions of protein phosphatases in regulating inflammatory homeostasis is lacking. The molecular knowledge of protein phosphatases, and especially the unique biochemical traits of each family member, will be of critical importance for developing drugs that target phosphatases. Here, we provide a comprehensive summary of the structure, the "double-edged sword" function, and the extensive signaling pathways of all protein phosphatases in inflammation-related diseases, as well as their potential inhibitors or activators that can be used in therapeutic interventions in preclinical or clinical trials. We provide an integrated perspective on the current understanding of all the protein phosphatases associated with inflammation-related diseases, with the aim of facilitating the development of drugs that target protein phosphatases for the treatment of inflammation-related diseases.

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.

SHP2 allosteric inhibitor TK-453 alleviates psoriasis-like skin inflammation in mice via inhibition of IL-23/Th17 axis

SHP2 is the first oncogenic tyrosine phosphatase encoded by PTPN11, which plays a significant regulatory role in cancer and inflammation-related diseases. Although SHP2 allosteric inhibitors have been used in phase I/II clinical trials for solid tumors, whether SHP2 inhibition alleviates psoriasis remains unclear. Here we expressed and purified SHP2 related proteins, and established an enzyme activity screening system for different conformations of SHP2. We launched an iterative medicinal chemistry program and identified the lead compound, TK-453. Importantly, TK-453 possessed stronger affinity with SHP2 than SHP099, evidenced by the cocrystal structure of SHP2/TK-453, revealing that the additional aryl-S-aryl bridge in TK-453 induces a 1.8 Å shift of the dichlorophenyl ring and an approximate 20° deviation of the pyrazine ring plane relative to SHP099. Furthermore, TK-453 significantly ameliorated imiquimod-triggered skin inflammation in mice via inhibition of the IL-23/Th17 axis, proving that SHP2 is a potential therapeutic target for psoriasis.

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We identify a SHP2 allosteric inhibitor TK-453, which has a stronger affinity with SHP2

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Cocrystal structure shows that TK-453 occupies the allosteric pocket of SHP2

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TK-453 alleviates psoriasis-like skin inflammation in mice

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SHP2 inhibitor provides a new strategy for the treatment of psoriasis

Proteolysis-targeting chimera molecules targeting SHP2

SHP2 is a member of the non-receptor protein tyrosine phosphatases, encoded by PTPN11, and exhibits oncogenic activities. The close association between SHP2 and human cancer has made SHP2 a promising target for clinical therapy. Proteolysis-targeting chimera (PROTAC) technology utilizes the degradation mechanism of the ubiquitin proteasome system to degrade specific proteins. It has strong advantages compared with inhibitors. Here we list the four reported PROTAC molecules targeting SHP2 and summarize the recently reported SHP2 inhibitors which can provide lead compounds for designing new SHP2 PROTACs. We also introduce the dual PROTAC technology which may replace drug combinations to treat SHP2-related diseases.

Discovery and Structural Optimization of Toddacoumalone Derivatives as Novel PDE4 Inhibitors for the Topical Treatment of Psoriasis

Psoriasis is a common immune-mediated skin disorder manifesting in abnormal skin plaques, and phosphodiesterase 4 (PDE4) is an effective target for the treatment of inflammatory diseases such as psoriasis. Toddacoumalone is a natural PDE4 inhibitor with moderate potency and imperfect drug-like properties. To discover novel and potent PDE4 inhibitors with considerable druggability, a series of toddacoumalone derivatives were designed and synthesized, leading to the compound (2R,4S)-6-ethyl-2-(2-hydroxyethyl)-2,8-dimethyl-4-(2-methylprop-1-en-1-yl)-2,3,4,6-tetrahydro-5H-pyrano[3,2-c][1,8]naphthyridin-5-one (33a) with high inhibitory potency (IC₅₀ = 3.1 nM), satisfactory selectivity, favorable skin permeability, and a well-characterized binding mechanism. Encouragingly, topical administration of 33a exhibited remarkable therapeutic effects in an imiquimod-induced psoriasis mouse model.

Structure-based design, synthesis and biological evaluation of aminopyrazines as highly potent, selective, and cellularly active allosteric SHP2 inhibitors

Src homology-2-containing protein tyrosine phosphatase 2 (SHP2) encoded by the proto-oncogene PTPN11 is the first identified non-receptor protein tyrosine phosphatase. SHP2 dysregulation contributes to the pathogenesis of different cancers, making SHP2 a promising therapeutic target for cancer therapy. In this article, we report the structure-guided design based on the well-characterized SHP2 inhibitor SHP099, extensive structure-activity relationship studies (SARs) of aminopyrazines, biochemical characterization and cellular potency. These medicinal chemistry efforts lead to the discovery of the lead compound TK-453, which potently inhibits SHP2 (SHP2^WT IC₅₀ = 0.023 μM, ΔTm = 7.01 °C) in a reversible and noncompetitive manner. TK-453 exhibits high selectivity over SHP2^PTP, SHP1 and PTP1B, and may bind at the "tunnel" allosteric site of SHP2 as SHP099. As the key pharmacophore, the aminopyrazine scaffold not only reorganizes the cationic-π stacking interaction with R111 via the novel hydrogen bond interaction between the S atom of thioether linker and T219, but also mediates a hydrogen bond with E250. In vitro studies indicate that TK-453 inhibits proliferation of HeLa, KYSE-70 and THP-1 cells moderately and induces apoptosis of Hela cells. Further mechanistic studies suggest that TK-453 can decrease the phosphorylation levels of AKT and Erk1/2 in HeLa and KYSE-70 cells. Collectively, TK-453 is a highly potent, selective, and cellularly active allosteric SHP2 inhibitor that modulates the phosphorylation of SHP2-mediated AKT and Erk cell signaling pathways by inhibiting the phosphatase activity of SHP2.

Strategies Targeting Protein Tyrosine Phosphatase SHP2 for Cancer Therapy

The protein tyrosine phosphatase SHP2 encoded by PTPN11 is a promising therapeutic target for cancer therapy, while the multifaceted roles of SHP2 complicate the drug discovery targeting SHP2. Given the biological significance of SHP2, strategies targeting SHP2 have been developed in recent years. To date, eight SHP2 inhibitors have advanced into clinical trials as mono- or combined therapy for treating solid tumors or adaptive resistant cancers. In this Perspective, we briefly summarize the strategies targeting SHP2 including inhibitors, activators, and proteolysis-targeting chimera (PROTAC) degraders. Besides, targeting the protein-protein interactions between SHP2 and other adaptor proteins is also discussed. Finally, we also highlight the target- and pathway-dependent combination strategies of SHP2 for cancer therapy. This Perspective may provide a timely and updated overview on the strategies targeting SHP2 for cancer therapy.

Inhibition of SHP2 as an approach to block RAS-driven cancers

The non-receptor protein tyrosine phosphatase SHP2 (encoded by PTPN11) is a critical component of RAS/MAPK signaling by acting upstream of RAS to promote oncogenic signaling and tumor growth. Over three decades, SHP2 was considered "undruggable" because enzymatic active-site inhibitors generally showed off-target inhibition of other proteins and low membrane permeability. More recently, allosteric SHP2 inhibitors with striking inhibitory potency have been developed. These small molecules effectively block the signal transduction between receptor tyrosine kinases (RTKs) and RAS/MAPK signaling and show efficacy in preclinical cancer models. Moreover, clinical evaluation of these allosteric SHP2 inhibitors is ongoing. RAS proteins which harbor transforming properties by gain-of-function mutations are present in various cancer types. While inhibitors of KRASG12C show early clinical promise, resistance remains a challenge and other forms of oncogenic RAS remain to be selectively inhibited. Here, we summarize the role of SHP2 in RAS-driven cancers and the therapeutic potential of allosteric SHP2 inhibitors as a strategy to block RAS-driven cancers.

Endothelial Shp2 deficiency controls alternative activation of macrophage preventing radiation-induced lung injury through Notch signaling

Radiation-induced lung injury is a common late side effect of thoracic radiotherapy. Endothelial dysfunction following leukocytes infiltration is a prominent feature in this process. Here, we established a clinical-mimicking mouse model of radiation-induced lung injury and found the activity of phosphatase Shp2 was elevated in endothelium after injury. Endothelium-specific Shp2 deletion mice showed relieved collagen deposition along with disrupted radiation-induced Jag1 expression in the endothelium. Furthermore, endothelium-derived Jag1 activated the alternative activation of macrophages in vitro and in vivo by paracrine Notch signaling. Consistently, the Notch pathway was significantly activated by chest irradiation in the peripheral blood leukocytes of patients with cancer. Collectively, our work demonstrates that Shp2 participates in the radiation-induced endothelial dysfunction and subsequently inflammatory microenvironment producing during radiation-induced lung injury. Our findings indicate Shp2 as a potential target for radiation-induced lung injury and provide another way for endothelium to participate in the pathological process of radiation-induced lung injury.

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Phosphatase activity of endothelial Shp2 is elevated by irradiation in vitro and in vivo

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Radiation-induced Jag1 is blocked in Shp2-deficient endothelium

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Loss of Shp2 in endothelium relieves radiation-induced pulmonary injury

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Shp2-deficient endothelium restrains macrophage activation via Notch signaling

Combination strategies with PD-1/PD-L1 blockade: current advances and future directions

Antibodies targeting programmed cell death protein-1 (PD-1) or its ligand PD-L1 rescue T cells from exhausted status and revive immune response against cancer cells. Based on the immense success in clinical trials, ten α-PD-1 (nivolumab, pembrolizumab, cemiplimab, sintilimab, camrelizumab, toripalimab, tislelizumab, zimberelimab, prolgolimab, and dostarlimab) and three α-PD-L1 antibodies (atezolizumab, durvalumab, and avelumab) have been approved for various types of cancers. Nevertheless, the low response rate of α-PD-1/PD-L1 therapy remains to be resolved. For most cancer patients, PD-1/PD-L1 pathway is not the sole speed-limiting factor of antitumor immunity, and it is insufficient to motivate effective antitumor immune response by blocking PD-1/PD-L1 axis. It has been validated that some combination therapies, including α-PD-1/PD-L1 plus chemotherapy, radiotherapy, angiogenesis inhibitors, targeted therapy, other immune checkpoint inhibitors, agonists of the co-stimulatory molecule, stimulator of interferon genes agonists, fecal microbiota transplantation, epigenetic modulators, or metabolic modulators, have superior antitumor efficacies and higher response rates. Moreover, bifunctional or bispecific antibodies containing α-PD-1/PD-L1 moiety also elicited more potent antitumor activity. These combination strategies simultaneously boost multiple processes in cancer-immunity cycle, remove immunosuppressive brakes, and orchestrate an immunosupportive tumor microenvironment. In this review, we summarized the synergistic antitumor efficacies and mechanisms of α-PD-1/PD-L1 in combination with other therapies. Moreover, we focused on the advances of α-PD-1/PD-L1-based immunomodulatory strategies in clinical studies. Given the heterogeneity across patients and cancer types, individualized combination selection could improve the effects of α-PD-1/PD-L1-based immunomodulatory strategies and relieve treatment resistance.

Harnessing Reversed Allosteric Communication: A Novel Strategy for Allosteric Drug Discovery

Allostery is a fundamental and extensive mechanism of intramolecular signal transmission. Allosteric drugs possess several unique pharmacological advantages over traditional orthosteric drugs, including greater selectivity, better physicochemical properties, and lower off-target toxicity. However, owing to the complexity of allosteric regulation, experimental approaches for the development of allosteric modulators are traditionally serendipitous. Recently, the reversed allosteric communication theory has been proposed, providing a feasible tool for the unbiased detection of allosteric sites. Herein, we review the latest research on the reversed allosteric communication effect using the examples of sirtuin 6, epidermal growth factor receptor, 3-phosphoinositide-dependent protein kinase 1, and Related to A and C kinases (RAC) serine/threonine protein kinase B and recapitulate the methodologies of reversed allosteric communication strategy. The novel reversed allosteric communication strategy greatly expands the horizon of allosteric site identification and allosteric mechanism exploration and is expected to accelerate an end-to-end framework for drug discovery.

Strategies to overcome drug resistance using SHP2 inhibitors

Encoded by PTPN11, the SHP2 (Src homology-2 domain-containing protein tyrosine phosphatase-2) is widely recognized as a carcinogenic phosphatase. As a promising anti-cancer drug target, SHP2 regulates many signaling pathways such as RAS-RAF-ERK, PI3K-AKT and JAK-STAT. Meanwhile, SHP2 plays a significant role in regulating immune cell function in the tumor microenvironment. Heretofore, five SHP2 allosteric inhibitors have been recruited in clinical studies for the treatment of cancer. Most recently, studies have proved the therapeutic potential of SHP2 inhibitor in overcoming drug resistance of kinase inhibitors and programmed cell death-1 (PD-1) blockade. Herein, we review the structure, function and small molecular inhibitors of SHP2, and highlight recent progress in overcoming drug resistance using SHP2 inhibitor. We hope this review would facilitate the future clinical development of SHP2 inhibitors.

Small-Molecule Inhibitors and Degraders Targeting KRAS-Driven Cancers

Drug resistance continues to be a major problem associated with cancer treatment. One of the primary causes of anticancer drug resistance is the frequently mutated RAS gene. In particular, considerable efforts have been made to treat KRAS-induced cancers by directly and indirectly controlling the activity of KRAS. However, the RAS protein is still one of the most prominent targets for drugs in cancer treatment. Recently, novel targeted protein degradation (TPD) strategies, such as proteolysis-targeting chimeras, have been developed to render "undruggable" targets druggable and overcome drug resistance and mutation problems. In this study, we discuss small-molecule inhibitors, TPD-based small-molecule chemicals for targeting RAS pathway proteins, and their potential applications for treating KRAS-mutant cancers. Novel TPD strategies are expected to serve as promising therapeutic methods for treating tumor patients with KRAS mutations.

Colony Stimulating Factor-1 and its Receptor in Gastrointestinal Malignant Tumors

Gastrointestinal malignant tumor is the fourth most common cancer in the world and the second cause of cancer death. Due to the susceptibility to lymphatic metastasis and liver metastasis, the prognosis of advanced tumor patients is still poor till now. With the development of tumor molecular biology, the tumor microenvironment and the cytokines, which are closely related to the proliferation, infiltration and metastasis, have become a research hotspot in life sciences. Colony stimulating factor-1 (CSF-1), a polypeptide chain cytokine, and its receptor CSF-1R are reported to play important roles in regulating tumor-associated macrophages in tumor microenvironment and participating in the occurrence and development in diversities of cancers. Targeted inhibition of the CSF-1/CSF-1R signal axis has broad application prospects in cancer immunotherapy. Here, we reviewed the biological characters of CSF-1/CSF-1R and their relationship with gastrointestinal malignancies.