Therapeutic Targeting of Oncogenic Tyrosine Phosphatases

Development of coumarin and procaine linked hybrid molecules as a novel class of SHP1 fluorescent activators

The development of small fluorescent organic molecules used in bioimaging experiment has boomed the progress of molecular and cellular biology, providing new and efficient tools to elucidate a myriad of cellular and multicellular processes. In this work, a class of fluorescent activators against SHP1 was designed and synthesized for the first time. The representative compound 3n showed activating effect against SHP1 with EC50 of 17.66 ± 1.48 μM and a fluorescence quantum yield of 0.521 in DMSO. Meanwhile, 3n showed good selectivity for SHP1, inhibited the proliferation of SU-DHL-2 cells and OCI-Ly10 cells with IC50 of 8.66 ± 1.26 μM and 9.16 ± 0.53 μM and exhibited potential for cellular imaging on human breast cancer cells.

SHP2 regulates the HIF-1 signaling pathway in the decidual human endometrial stromal cells†

The decidual endometrial stromal cells play a critical role in the establishment of uterine receptivity and pregnancy in human. Our previous studies demonstrate that protein tyrosine phosphatase 2 SHP2 is highly expressed in decidualized cells and governs the decidualization progress. However, the role and mechanism of SHP2 in the function of decidual cells remain unclear. Here, we screened proteins interacting with SHP2 in decidual hTERT-immortalized human endometrial stromal cells (T-HESCs) and identified Hypoxia-inducible factor-1 (HIF-1) signaling pathway as a potential SHP2-mediated signaling pathway through proximity-dependent biotinylation (BioID) analysis. Immunoprecipitation (Co-IP) revealed an interaction between SHP2 and HIF-1α, which colocalized to the nucleus in decidual cells. Furthermore, the SHP2 expression correlated with the transcriptional activation of HIF-1α and its downstream genes Beta-enolase (Eno3), Pyruvate kinase 2 (Pkm2), Aldolase C (Aldoc), and Facilitative glucose transporter 1 (Glut1). Knockdown or inhibition of SHP2 significantly reduced the mRNA and protein levels of HIF-1α and its downstream genes, as well as lactate production in decidual cells. We also established a hypoxia model of T-HESCs and 293 T cells and found that hypoxic treatment induced the expression of SHP2 and HIF-1α, which colocalized in the nucleus. SHP2 forced-expression rescued the inhibitory effects of SHP2 deficiency on HIF-1α expression and lactate production. Finally, SHP2 binds to the promoter regions of HIF-1α and its target genes (Eno3, Pkm2, Aldoc, and Glut1). Collectively, our results suggest that SHP2 influences the function of decidual cells by HIF-1α signaling and provide a novel function mechanism of decidual stromal cells.

The PRL2 phosphatase up-regulates miR-21 through activation of the JAK2/STAT3 pathway to down-regulate the PTEN tumor suppressor

The phosphatases of regenerating liver (PRLs) are members of the protein tyrosine phosphatase (PTP) superfamily that play pro-oncogenic roles in cell proliferation, migration, and survival. We previously demonstrated that PRLs can post-translationally down-regulate PTEN, a tumor suppressor frequently inactivated in human cancers, by dephosphorylating PTEN at Tyr336, which promotes the NEDD4-mediated PTEN ubiquitination and proteasomal degradation. Here, we report that PRLs can also reduce PTEN expression by up-regulating microRNA-21 (miR-21), which is one of the most frequently overexpressed miRNAs in solid tumors. We observe a broad correlation between PRL and miR-21 levels in multiple human cancers. Mechanistically, PRL2, the most abundant and ubiquitously expressed PRL family member, promotes the JAK2/STAT3 pathway-mediated miR-21 expression by directly dephosphorylating JAK2 at Tyr570. Finally, we confirm that the PRL2-mediated miR-21 expression contributes to its oncogenic potential in breast cancer cells. Our study defines a new functional role of PRL2 in PTEN regulation through a miR-21-dependent post-transcriptional mechanism, in addition to our previously reported NEDD4-dependent post-translational PTEN regulation. Together, these studies further establish the PRLs as negative regulators of PTEN.

Covalent-Allosteric Inhibitors: Do We Get the Best of Both Worlds?

Covalent-allosteric inhibitors (CAIs) may achieve the best of both worlds: increased potency, long-lasting effects, and reduced drug resistance typical of covalent ligands, along with enhanced specificity and decreased toxicity inherent in allosteric modulators. Therefore, CAIs can be an effective strategy to transform many undruggable targets into druggable ones. However, CAIs are challenging to design. In this perspective, we analyze the discovery of known CAIs targeting three protein families: protein phosphatases, protein kinases, and GTPases. We also discuss how computational methods and tools can play a role in addressing the practical challenges of rational CAI design.

SHP2 is essential for the progesterone-promoted proliferation and migration in breast cancer cell lines

Introduction

We previously demonstrated that progesterone (P4) can promote breast cancer cell proliferation and migration through activating the P4 receptor (PR)/cSrc-mediated signaling pathway. It has been suggested that high level of Src homology region 2 domain-containing phosphatase-2 (SHP2) might be involved in breast oncogenesis. This study aimed to investigate whether SHP2 is involved in the P4-mediated cSrc activation in breast cancer cells.

Methods

T47D, MCF-7 and BT-483 breast cancer cell lines were used in this study. Cell proliferation and migration were examined using MTT technique and wound healing assay, respectively. Immunoprecipitation assay and Western blot analysis were performed to evaluate protein-protein interaction and protein expression, respectively. Small interfering RNA (siRNA) technique was used to knock down protein expression.

Results

Knockdown of SHP2 expression abolished the P4-promoted cell proliferation and migration in T47D, MCF and BT-483 cell lines, suggesting that presence of SHP2 is essential for the P4-increased proliferation and migration of breast cancer cell lines. P4 (50 nM) treatment increased the complex formations of PR-cSrc-SHP2-caveolin-1, SHP2-p140Cap, and SHP2-Csk, and the level of p-cSrcY416 (activated form of cSrc). However, knockdown of SHP2 expression increased the complex formations of PR-cSrc-caveolin-1-Csk-p140Cap and the levels of p-caveolin-1, p-Csk and p-cSrcY527 (inactivated form of cSrc).

Discussion

Our data suggest that SHP2 can bind to cSrc-negative regulatory proteins (p140Cap and Csk), hence preventing the interaction between cSrc and cSrc-negative regulatory proteins, leading to decreased phosphorylation of cSrc Y527 and prolonged cSrc activation. These findings highlight the role of SHP2 in the P4-promoted breast cancer cell proliferation and migration.

Structure-activity relationship studies and design of a PTPN22 inhibitor with enhanced isozyme selectivity and cellular efficacy

Protein tyrosine phosphatase non-receptor type 22 (PTPN22) lies downstream of the T cell receptor (TCR) and attenuates T cell signaling by dephosphorylating key effector proteins such as LCK, Zap70, and the intracellular region of the TCR. Recent evidence implicates PTPN22 as an exciting target for enabling immunotherapeutic efficacy against cancer. We carried out structural optimization of a benzofuran salicylic acid-based orthosteric PTPN22 inhibitor 8b, using a combination of crystal structure analysis, synthesis, matched molecular pairs analysis, and biochemical and cell-based assays. Herein, we report structure-activity relationship studies, lead optimization based on the 8b-PTPN22 co-crystal structure, and cellular evaluation of the top analog. Notably, our efforts yielded compound 8b-19, an essentially equipotent scaffold with superior isozyme selectivity, improved aqueous solubility, and significantly enhanced cellular efficacy compared to the parent 8b. This compound may serve as a lead for further optimization of PTPN22-targeting immunotherapies or as a chemical probe for interrogation for additional links between PTPN22 and immunomodulation in cells.

Mechanisms and therapeutic prospect of the JAK-STAT signaling pathway in liver cancer

Liver cancer (LC) poses a significant global health challenge due to its high incidence and poor prognosis. Current systemic treatment options, such as surgery, chemotherapy, radiofrequency ablation, and immunotherapy, have shown limited effectiveness for advanced LC patients. Moreover, owing to the heterogeneous nature of LC, it is crucial to uncover more in-depth pathogenic mechanisms and develop effective treatments to address the limitations of the existing therapeutic modalities. Increasing evidence has revealed the crucial role of the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway in the pathogenesis of LC. The specific mechanisms driving the JAK-STAT pathway activation in LC, participate in a variety of malignant biological processes, including cell differentiation, evasion, anti-apoptosis, immune escape, and treatment resistance. Both preclinical and clinical investigations on the JAK-STAT pathway inhibitors have exhibited potential in LC treatment, thereby opening up avenues for the development of more targeted therapeutic strategies for LC. In this study, we provide an overview of the JAK-STAT pathway, delving into the composition, activation, and dynamic interplay within the pathway. Additionally, we focus on the molecular mechanisms driving the aberrant activation of the JAK-STAT pathway in LC. Furthermore, we summarize the latest advancements in targeting the JAK-STAT pathway for LC treatment. The insights presented in this review aim to underscore the necessity of research into the JAK-STAT signaling pathway as a promising avenue for LC therapy.

Opposing regulation of endoplasmic reticulum retention under stress by ERp44 and PDIA6

Conditions of endoplasmic reticulum (ER) stress reduce protein synthesis by provoking translation regulation, governed by the eIF2α kinase PERK. When PERK is inhibited during ER stress, retention of a selective subset of glycoproteins occurs, a phenomenon we termed selective ER retention (sERr). sERr clients are enriched with tyrosine kinase receptors (RTKs), which form large molecular weight disulfide bonded complexes in the ER. The protein disulfide isomerase ERp44 promotes sERr and increases the size of sERr complexes. Here we show that sERr is reversible upon washout. Pulse chase analyses show that upon recovery, only a small fraction of the sERr complexes disintegrates and contributes to the matured proteins, while most are newly synthesized. Sequential inductions of sERr and washouts demonstrate an accelerated recovery that is dependent on the unfolded protein response transducer IRE1. Since IRE1 regulates the expression level PDIA6, we analyzed its contribution to sERr. We found that PDIA6 and ERp44 constitutively interact by disulfides and have opposite effects on resumed recovery of trafficking following removal of sERr conditions. Deletion of ERp44 accelerates, while deletion of PDIA6 slows down recovery with a minimal effect on total protein synthesis. ERp44 is a primary interactor with sERr clients. When missing, PDIA6 partitions more into sERr complexes. Deletion of the tumor suppressor PTEN, which induces RTK signaling, promoted sERr formation kinetics, and accelerated the recovery, suggesting feedback between RTKs signaling and sERr. This study suggests that sERr, should develop physiologically or pathologically, is counteracted by adaptation responses that involve IRE1 and PDIA6.

Medicinal chemistry perspective of JAK inhibitors: synthesis, biological profile, selectivity, and structure activity relationship

JAK-STAT signalling pathway was discovered more than quarter century ago. The JAK-STAT pathway protein is considered as one of the crucial hubs for cytokine secretion which mediates activation of different inflammatory, cellular responses and hence involved in different etiological factors. The various etiological factors involved are haematopoiesis, immune fitness, tissue repair, inflammation, apoptosis, and adipogenesis. The presence of the active mutation V617K plays a significant role in the progression of the JAK-STAT pathway-related disease. Consequently, targeting the JAK-STAT pathway could be a promising therapeutic approach for addressing a range of causative factors. In this current review, we provided a comprehensive discussion for the in-detail study of anatomy and physiology of the JAK-STAT pathway which contributes structural domain rearrangement, activation, and negative regulation associated with the downstream signaling pathway, relationship between different cytokines and diseases. This review also discussed the recent development of clinical trial entities. Additionally, this review also provides updates on FDA-approved drugs. In the current investigation, we have classified recently developed small molecule inhibitors of JAK-STAT pathway according to different chemical classes and we emphasized their synthetic routes, biological evaluation, selectivity, and structure-activity relationship.

Phosphopeptide binding to the N-SH2 domain of tyrosine phosphatase SHP2 correlates with the unzipping of its central β-sheet

SHP2 is a tyrosine phosphatase that plays a regulatory role in multiple intracellular signaling cascades and is known to be oncogenic in certain contexts. In the absence of effectors, SHP2 adopts an autoinhibited conformation with its N-SH2 domain blocking the active site. Given the key role of N-SH2 in regulating SHP2, this domain has been extensively studied, often by X-ray crystallography. Using a combination of structural analyses and molecular dynamics (MD) simulations we show that the crystallographic environment can significantly influence the structure of the isolated N-SH2 domain, resulting in misleading interpretations. As an orthogonal method to X-ray crystallography, we use a combination of NMR spectroscopy and MD simulations to accurately determine the conformation of apo N-SH2 in solution. In contrast to earlier reports based on crystallographic data, our results indicate that apo N-SH2 in solution primarily adopts a conformation with a fully zipped central β-sheet, and that partial unzipping of this β-sheet is promoted by binding of either phosphopeptides or even phosphate/sulfate ions.

Targeting SHP1 and SHP2 to suppress tumors and enhance immunosurveillance

The nonreceptor tyrosine phosphatases (PTPS) SHP1 and SHP2 have crucial roles in dephosphorylating an array of substrates involved in pathways comprising receptor tyrosine kinases (RTKs) and immune receptors. This regulation maintains a delicate balance between the activation and inhibition of signal transduction, ensuring appropriate biological outcomes. In this review, we summarize research focused on elucidating the functions of SHP1 and SHP2 in hematopoiesis, immune regulation, and tumor biology, emphasizing recent findings related to cancer-driven immune evasion. Furthermore, we highlight the significant effects of SHP1 and SHP2 inhibitors in enhancing cancer treatment, specifically through the facilitation of chemotherapy and augmentation of immune activation.

Regulation of protein phosphorylation by PTPN2 and its small-molecule inhibitors/degraders as a potential disease treatment strategy

Protein tyrosine phosphatase nonreceptor type 2 (PTPN2) is an enzyme that dephosphorylates proteins with tyrosine residues, thereby modulating relevant signaling pathways in vivo. PTPN2 acts as tumor suppressor or tumor promoter depending on the context. In some cancers, such as colorectal, and lung cancer, PTPN2 defects could impair the protein tyrosine kinase pathway, which is often over-activated in cancer cells, and inhibit tumor development and progression. However, PTPN2 can also suppress tumor immunity by regulating immune cells and cytokines. The structure, functions, and substrates of PTPN2 in various tumor cells were reviewed in this paper. And we summarized the research status of small molecule inhibitors and degraders of PTPN2. It also highlights the potential opportunities and challenges for developing PTPN2 inhibitors as anticancer drugs.

STATs, promising targets for the treatment of autoimmune and inflammatory diseases

Cytokines play a crucial role in the pathophysiology of autoimmune and inflammatory diseases, with over 50 cytokines undergoing signal transduction through the Signal Transducers and Activators of Transcription (STAT) signaling pathway. Recent studies have solidly confirmed the pivotal role of STATs in autoimmune and inflammatory diseases. Therefore, this review provides a detailed summary of the immunological functions of STATs, focusing on exploring their mechanisms in various autoimmune and inflammatory diseases. Additionally, with the rapid advancement of structural biology in the field of drug discovery, many STAT inhibitors have been identified using structure-based drug design strategies. In this review, we also examine the structures of STAT proteins and compile the latest research on STAT inhibitors currently being tested in animal models and clinical trials for the treatment of immunological diseases, which emphasizes the feasibility of STATs as promising therapeutic targets and provides insights into the design of the next generation of STAT inhibitors.

Determination of promising inhibitors for N-SH2 domain of SHP2 tyrosine phosphatase: an in silico study

There are many genes that produce proteins related to diseases and these proteins can be targeted with drugs as a potential therapeutic approach. Recent advancement in drug discovery techniques have created new opportunities for treating variety of diseases by targeting disease-related proteins. Structure-based drug discovery is a faster and more cost-effective approach than traditional methods. SHP2 phosphatase, encoded by the PTPN11 gene, has been the focus of much attention due to its involvement in many types of diseases. The biological function of SHP2 is enabled mostly by protein-protein interaction through its SH2 domains. In this study, we report the identification of a potential small molecule inhibitor for the N-SH2 domain of SHP2 by structure-based drug discovery approach. We utilized molecular docking studies, followed by molecular dynamics simulations and MM/PBSA calculations, to analyze compounds retrieved from the Broad's Drug Repurposing Hub and ZINC15 databases. We selected 10 hit compounds with the best docking scores from the libraries and examined their binding properties in the N-SH2 domain. We found that compound CID 60838 (Irinotecan) was the most suitable compound with a binding free energy value of - 64.45 kcal/mol and significant interactions with the target residues in the domain.

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.

Hepatitis B Virus X Protein Represses Expression of Tumor Suppressor PTPN18 in Hepatocellular Carcinoma

HBV-associated hepatocellular carcinoma (HCC) represents the prevalent form of HCC, with HBx protein being a crucial oncoprotein. Numerous members of the protein tyrosine phosphatase nonreceptor (PTPN) family have been confirmed to be significantly associated with the occurrence and progression of malignant tumors. Our group previously identified the involvement of PTPN13 in HCC. However, the roles of other PTPNs in HCC require further investigation. In this study, we found that PTPN18 expression was significantly downregulated within HCC tissues compared with adjacent nontumor and reference liver tissues. Functionally, PTPN18 exerted inhibitory effects on the proliferation, migration, invasion, and sphere-forming capability of HCC cells while concurrently promoting apoptotic processes. Through phospho-protein microarray screening followed by subsequent validation experiments, we identified that PTPN18 could activate the p53 signaling pathway and suppress the AKT/FOXO1 signaling cascade in HCC cells. Moreover, the HBx protein mediated the repression of PTPN18 expression by upregulating miR-128-3p. Collectively, our study unveiled the role of PTPN18 as a tumor suppressor in HBV-related HCC. Implications: Our findings revealed that PTPN18 might be a potential diagnostic and therapeutic target for HBV-related HCC.

Off-target autophagy inhibition by SHP2 allosteric inhibitors contributes to their antitumor activity in RAS-driven cancers

Aberrant activation of RAS/MAPK signaling is common in cancer, and efforts to inhibit pathway components have yielded drugs with promising clinical activities. Unfortunately, treatment-provoked adaptive resistance mechanisms inevitably develop, limiting their therapeutic potential. As a central node essential for receptor tyrosine kinase-mediated RAS activation, SHP2 has emerged as an attractive cancer target. Consequently, many SHP2 allosteric inhibitors are now in clinical testing. Here we discovered a previously unrecognized off-target effect associated with SHP2 allosteric inhibitors. We found that these inhibitors accumulate in the lysosome and block autophagic flux in an SHP2-independent manner. We showed that off-target autophagy inhibition by SHP2 allosteric inhibitors contributes to their antitumor activity. We also demonstrated that SHP2 allosteric inhibitors harboring this off-target activity not only suppress oncogenic RAS signaling but also overcome drug resistance such as MAPK rebound and protective autophagy in response to RAS/MAPK pathway blockage. Finally, we exemplified a therapeutic framework that harnesses both the on- and off-target activities of SHP2 allosteric inhibitors for improved treatment of mutant RAS-driven and drug-resistant malignancies such as pancreatic and colorectal cancers.

SHP2 inhibition displays efficacy as a monotherapy and in combination with JAK2 inhibition in preclinical models of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs), including polycythemia vera, essential thrombocytosis, and primary myelofibrosis, are clonal hematopoietic neoplasms driven by mutationally activated signaling by the JAK2 tyrosine kinase. Although JAK2 inhibitors can improve MPN patients' quality of life, they do not induce complete remission as disease-driving cells persistently survive therapy. ERK activation has been highlighted as contributing to JAK2 inhibitor persistent cell survival. As ERK is a component of signaling by activated RAS proteins and by JAK2 activation, we sought to inhibit RAS activation to enhance responses to JAK2 inhibition in preclinical MPN models. We found the SHP2 inhibitor RMC-4550 significantly enhanced growth inhibition of MPN cell lines in combination with the JAK2 inhibitor ruxolitinib, effectively preventing ruxolitinib persistent growth, and the growth and viability of established ruxolitinib persistent cells remained sensitive to SHP2 inhibition. Both SHP2 and JAK2 inhibition diminished cellular RAS-GTP levels, and their concomitant inhibition enhanced ERK inactivation and increased apoptosis. Inhibition of SHP2 inhibited the neoplastic growth of MPN patient hematopoietic progenitor cells and exhibited synergy with ruxolitinib. RMC-4550 antagonized MPN phenotypes and increased survival of an MPN mouse model driven by MPL-W515L. The combination of RMC-4550 and ruxolitinib, which was safe and tolerated in healthy mice, further inhibited disease compared to ruxolitinib monotherapy, including extending survival. Given SHP2 inhibitors are undergoing clinical evaluation in patients with solid tumors, our preclinical findings suggest that SHP2 is a candidate therapeutic target with potential for rapid translation to clinical assessment to improve current targeted therapies for MPN patients.

Pharmacological inhibition of the Src homology phosphatase 2 confers partial protection in a mouse model of alcohol-associated liver disease

Alcohol-associated liver disease (ALD) is a leading factor of liver-related death worldwide. ALD has various manifestations that include steatosis, hepatitis, and cirrhosis and is currently without approved pharmacotherapies. The Src homology phosphatase 2 (Shp2) is a drug target in some cancers due to its positive regulation of Ras-mitogen-activated protein kinase signaling and cell proliferation. Shp2 pharmacological inhibition yields beneficial outcomes in animal disease models, but its impact on ALD remains unexplored. This study aims to investigate the effects of Shp2 inhibition and its validity using a preclinical mouse model of ALD. We report that the administration of SHP099, a potent and selective allosteric inhibitor of Shp2, partially ameliorated ethanol-induced hepatic injury, inflammation, and steatosis in mice. Additionally, Shp2 inhibition was associated with reduced ethanol-evoked activation of extracellular signal-regulated kinase (ERK), oxidative, and endoplasmic reticulum (ER) stress in the liver. Besides the liver, excessive alcohol consumption induces multi-organ injury and dysfunction, including the intestine. Notably, Shp2 inhibition diminished ethanol-induced intestinal inflammation and permeability, abrogated the reduction in tight junction protein expression, and the activation of ERK and stress signaling in the ileum. Collectively, Shp2 pharmacological inhibition mitigates the deleterious effects of ethanol in the liver and intestine in a mouse model of ALD. Given the multifactorial aspects underlying ALD pathogenesis, additional studies are needed to decipher the utility of Shp2 inhibition alone or as a component in a multitherapeutic regimen to combat this deadly malady.

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

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

Probing the Immunoreceptor Tyrosine-Based Inhibition Motif Interaction Protein Partners with Proteomics

Phosphorylation of tyrosine is the basic mode of protein function and signal transduction in organisms. This process is regulated by protein tyrosine kinases (PTKs) and protein tyrosinases (PTPs). Immunoreceptor tyrosine-based inhibition motif (ITIM) has been considered as regulating the PTP activity through the interaction with the partner proteins in the cell signal pathway. The ITIM sequences need to be phosphorylated first to active the downstream signaling proteins. To explore potential regulatory mechanisms, the ITIM sequences of two transmembrane immunoglobulin proteins, myelin P0 protein-related protein (PZR) and programmed death 1 (PD-1), were analyzed to investigate their interaction with proteins involved in regulatory pathways. We discovered that phosphorylated ITIM sequences can selectively interact with the tyrosine phosphatase SHP2. Specifically, PZR-N-ITIM (pY) may be critical in the interaction between the ITIM and SH2 domains of SHP2, while PD1-C-ITSM (pY) may play a key role in the interaction between the ITIM and SH2 domains of SHP2. Quite a few proteins were identified containing the SH2 domain, exhibiting phosphorylation-mediated interaction with PZR-ITIM. In this study, 14 proteins with SH2 structural domains were identified by GO analysis on 339 proteins associated to the affinity pull-down of PZR-N-ITIM (pY). Through the SH2 domains, these proteins may interact with PZR-ITIM in a phosphorylation-dependent manner.

Role of Protein Tyrosine Phosphatase Receptor Type E (PTPRE) in Chemoresistant Retinoblastoma

Protein tyrosine phosphatase receptor type E (PTPRE) is a member of the "classical" protein tyrosine phosphatase subfamily and regulates a variety of cellular processes in a tissue-specific manner by antagonizing the function of protein tyrosine kinases. PTPRE plays a tumorigenic role in different human cancer cells, but its role in retinoblastoma (RB), the most common malignant eye cancer in children, remains to be elucidated. Etoposide-resistant RB cell lines and RB patients display significant higher PTPRE expression levels compared to chemosensitive counterparts and the healthy human retina, respectively. PTPRE promotor methylation analyses revealed that PTPRE expression in RB is not regulated via this mechanism. Lentiviral PTPRE knockdown (KD) induced a significant decrease in growth kinetics, cell viability, and anchorage-independent growth of etoposide-resistant Y79 and WERI RB cells. Caspase-dependent apoptosis rates were significantly increased and a re-sensitization for etoposide could be observed after PTPRE depletion. In vivo chicken chorioallantoic membrane (CAM) assays revealed decreased tumor formation capacity as well as reduced tumor size and weight following PTPRE KD. Expression levels of miR631 were significantly downregulated in etoposide-resistant RB cells and patients. Transient miR631 overexpression resulted in significantly decreased PTPRE levels and concomitantly decreased proliferation and increased apoptosis levels in etoposide-resistant RB cells. These impacts mirror PTPRE KD effects, indicating a regulation of PTPRE via this miR. Additionally, PTPRE KD led to altered phosphorylation of protein kinase SGK3 and-dependent on the cell line-AKT and ERK1/2, suggesting potential PTPRE downstream signaling pathways. In summary, these results indicate an oncogenic role of PTPRE in chemoresistant retinoblastoma.

From bench to bedside: current development and emerging trend of KRAS-targeted therapy

Kirsten rat sarcoma 2 viral oncogene homolog (KRAS) is the most frequently mutated oncogene in human cancers with mutations predominantly occurring in codon 12. These mutations disrupt the normal function of KRAS by interfering with GTP hydrolysis and nucleotide exchange activity, making it prone to the GTP-bound active state, thus leading to sustained activation of downstream pathways. Despite decades of research, there has been no progress in the KRAS drug discovery until the groundbreaking discovery of covalently targeting the KRASG12C mutation in 2013, which led to revolutionary changes in KRAS-targeted therapy. So far, two small molecule inhibitors sotorasib and adagrasib targeting KRASG12C have received accelerated approval for the treatment of non-small cell lung cancer (NSCLC) harboring KRASG12C mutations. In recent years, rapid progress has been achieved in the KRAS-targeted therapy field, especially the exploration of KRASG12C covalent inhibitors in other KRASG12C-positive malignancies, novel KRAS inhibitors beyond KRASG12C mutation or pan-KRAS inhibitors, and approaches to indirectly targeting KRAS. In this review, we provide a comprehensive overview of the molecular and mutational characteristics of KRAS and summarize the development and current status of covalent inhibitors targeting the KRASG12C mutation. We also discuss emerging promising KRAS-targeted therapeutic strategies, with a focus on mutation-specific and direct pan-KRAS inhibitors and indirect KRAS inhibitors through targeting the RAS activation-associated proteins Src homology-2 domain-containing phosphatase 2 (SHP2) and son of sevenless homolog 1 (SOS1), and shed light on current challenges and opportunities for drug discovery in this field.

Targeting PRL phosphatases in hematological malignancies

INTRODUCTION

Phosphatase of regenerating liver (PRL) family proteins, also known as protein tyrosine phosphatase 4A (PTP4A), have been implicated in many types of cancers. The PRL family of phosphatases consists of three members, PRL1, PRL2, and PRL3. PRLs have been shown to harbor oncogenic potentials and are highly expressed in a variety of cancers. Given their roles in cancer progression and metastasis, PRLs are potential targets for anticancer therapies. However, additional studies are needed to be performed to fully understand the roles of PRLs in blood cancers.

AREAS COVERED

In this review, we will summarize recent studies of PRLs in normal and malignant hematopoiesis, the role of PRLs in regulating various signaling pathways, and the therapeutic potentials of targeting PRLs in hematological malignancies. We will also discuss how to improve current PRL inhibitors for cancer treatment.

EXPERT OPINION

Although PRL inhibitors show promising therapeutic effects in preclinical studies of different types of cancers, moving PRL inhibitors from bench to bedside is still challenging. More potent and selective PRL inhibitors are needed to target PRLs in hematological malignancies and improve treatment outcomes.

Novel imidazo[1,2,4] triazole derivatives: Synthesis, fluorescence, bioactivity for SHP1

The Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP1) is a convergent node for oncogenic cell-signaling cascades. Consequently, SHP1 represents a potential target for drug development in cancer treatment. The development of efficient methods for rapidly tracing and modulating the SHP1 activity in complex biological systems is of considerable significance for advancing the integration of diagnosis and treatment of the related disease. Thus, we designed and synthesized a series of imidazo[1,2,4] triazole derivatives containing salicylic acid to explore novel scaffolds with inhibitory activities and good fluorescence properties for SHP1. The photophysical properties and inhibitory activities of these imidazo[1,2,4] triazole derivatives (5a-5y) against SHP1PTP were thoroughly studied from the theoretical simulation and experimental application aspects. The representative compound 5p exhibited remarkable fluorescence response (P: 0.002) with fluorescence quantum yield (QY) of 0.37 and inhibitory rate of 85.21 ± 5.17% against SHP1PTP at the concentration of 100 μM. Furthermore, compound 5p showed obvious aggregation caused quenching (ACQ) effect and had high selectivity for Fe3+ ions, good anti-interference and relatively low detection limit (5.55 μM). Finally, the cellular imaging test of compound 5p also exhibited good biocompatibility and certain potential biological imaging application. This study provides a potential way to develop molecules with fluorescent properties and bioactivities for SHP1.

JAK/STAT in leukemia: a clinical update

Over the past three decades, considerable efforts have been expended on understanding the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway in leukemia, following the identification of the JAK2V617F mutation in myeloproliferative neoplasms (MPNs). The aim of this review is to summarize the latest progress in our understanding of the involvement of the JAK/STAT signaling pathway in the development of leukemia. We also attempt to provide insights into the current use of JAK/STAT inhibitors in leukemia therapy and explore pertinent clinical trials in this field.

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.

Inhibition of PRL2 Upregulates PTEN and Attenuates Tumor Growth in Tp53-deficient Sarcoma and Lymphoma Mouse Models

The phosphatases of regenerating liver (PRL) are oncogenic when overexpressed. We previously found that PRL2 deletion increases PTEN, decreases Akt activity, and suppresses tumor development in a partial Pten-deficient mouse model. The current study aims to further establish the mechanism of PTEN regulation by PRL2 and expand the therapeutic potential for PTEN augmentation mediated by PRL2 inhibition in cancers initiated without PTEN alteration. The TP53 gene is the most mutated tumor suppressor in human cancers, and heterozygous or complete deletion of Tp53 in mice leads to the development of sarcomas and thymic lymphomas, respectively. There remains a lack of adequate therapies for the treatment of cancers driven by Tp53 deficiency or mutations. We show that Prl2 deletion leads to PTEN elevation and attenuation of Akt signaling in sarcomas and lymphomas developed in Tp53 deficiency mouse models. This results in increased survival and reduced tumor incidence because of impaired tumor cell proliferation. In addition, inhibition of PRL2 with a small-molecule inhibitor phenocopies the effect of genetic deletion of Prl2 and reduces Tp53 deficiency-induced tumor growth. Taken together, the results further establish PRL2 as a negative regulator of PTEN and highlight the potential of PRL2 inhibition for PTEN augmentation therapy in cancers with wild-type PTEN expression.

SIGNIFICANCE

Prl2 deletion attenuates Tp53 deficiency-induced tumor growth by increasing PTEN and reducing Akt activity. Targeting Tp53-null lymphoma with PRL inhibitors lead to reduced tumor burden, providing a therapeutic approach via PTEN augmentation.

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.

High-Throughput Discovery and Characterization of Covalent Inhibitors for Protein Tyrosine Phosphatases

Covalent inhibition has gained increasing interest in targeting the undruggable protein tyrosine phosphatases (PTPs). However, a systematic method for discovering and characterizing covalent PTP inhibitors has yet to be established. Here, we describe a workflow involving high-throughput screening of covalent fragment libraries and a novel biochemical assay that enables the acquisition of kinetics parameters of PTP inhibition by covalent inhibitors with higher throughput.

Atomistic ensemble of active SHP2 phosphatase

SHP2 phosphatase plays an important role in regulating several intracellular signaling pathways. Pathogenic mutations of SHP2 cause developmental disorders and are linked to hematological malignancies and cancer. SHP2 comprises two tandemly-arranged SH2 domains, a catalytic PTP domain, and a disordered C-terminal tail. Under physiological, non-stimulating conditions, the catalytic site of PTP is occluded by the N-SH2 domain, so that the basal activity of SHP2 is low. Whereas the autoinhibited structure of SHP2 has been known for two decades, its active, open structure still represents a conundrum. Since the oncogenic mutant SHP2E76K almost completely populates the active, open state, this mutant has been extensively studied as a model for activated SHP2. By molecular dynamics simulations and accurate explicit-solvent SAXS curve predictions, we present the heterogeneous atomistic ensemble of constitutively active SHP2E76K in solution, encompassing a set of conformational arrangements and radii of gyration in agreement with experimental SAXS data.

Protein tyrosine phosphatases as emerging targets for cancer immunotherapy

Contemporary strategies in cancer immunotherapy, despite remarkable success, remain constrained by inherent limitations such as suboptimal patient responses, the emergence of drug resistance, and the manifestation of pronounced adverse effects. Consequently, the need for alternative strategies for immunotherapy becomes clear. Protein tyrosine phosphatases (PTPs) wield a pivotal regulatory influence over an array of essential cellular processes. Substantial research has underscored the potential in targeting PTPs to modulate the immune responses and/or regulate antigen presentation, thereby presenting a novel paradigm for cancer immunotherapy. In this review, we focus on recent advances in genetic and biological validation of several PTPs as emerging targets for immunotherapy. We also highlight recent development of small molecule inhibitors and degraders targeting these PTPs as novel cancer immunotherapeutic agents.

PTPRH promotes the progression of non-small cell lung cancer via glycolysis mediated by the PI3K/AKT/mTOR signaling pathway

BACKGROUND

The protein tyrosine phosphatase H receptor (PTPRH) is known to regulate the occurrence and development of pancreatic and colorectal cancer. However, its association with glycolysis in non-small cell lung cancer (NSCLC) is still unclear. In this study, we aimed to investigate the relationship between PTPRH expression and glucose metabolism and the underlying mechanism of action.

METHODS

The expression of PTPRH in NSCLC cells was evaluated by IHC staining, qRT‒PCR and Western blotting. The effect of PTPRH on cell biological behavior was evaluated by colony assays, EdU experiments, Transwell assays, wound healing assays and flow cytometry. Changes in F-18-fluorodeoxyglucose (18F-FDG) uptake and glucose metabolite levels after altering PTPRH expression were detected via a gamma counter and lactic acid tests. The expression of glycolysis-related proteins in NSCLC cells was detected by Western blotting after altering PTPRH expression.

RESULTS

The results showed that PTPRH was highly expressed in clinical patient tissue samples and closely related to tumor diameter and clinical stage. In addition, PTPRH expression was associated with glycometabolism indexes on 18F-FDG positron emission tomography/computed tomography (PET/CT) imaging, the expression level of Ki67 and the expression levels of glycolysis-related proteins. PTPRH altered cell behavior, inhibited apoptosis, and promoted 18F-FDG uptake, lactate production, and the expression of glycolysis-related proteins. In addition, PTPRH modulated the glycometabolism of NSCLC cells via the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway, as assessed using LY294002 and 740Y-P (an inhibitor and agonist of PI3K, respectively). The same results were validated in vivo using a xenograft tumor model in nude mice. Protein expression levels of PTPRH, glycolysis-related proteins, p-PI3K/PI3K and p-AKT/AKT were measured by IHC staining using a subcutaneous xenograft model in nude mice.

CONCLUSIONS

In summary, we report that PTPRH promotes glycolysis, proliferation, migration, and invasion via the PI3K/AKT/mTOR signaling pathway in NSCLC and ultimately promotes tumor progression, which can be regulated by LY294002 and 740Y-P. These results suggest that PTPRH is a potential therapeutic target for NSCLC.

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.

Relationship between SHP2 gene polymorphisms and systemic lupus erythematosus risk

OBJECTIVE

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder. SHP2, a non-transmembrane member of the protein tyrosine phosphatase (PTP) family, can be involved in multiple signaling pathways in inflammatory response. To date, it remains to be investigated whether polymorphisms in the SHP2 gene are correlated with SLE in the Chinese Han population.

METHOD

A study comprising 320 SLE patients and 400 healthy individuals was performed. Three single nucleotide polymorphisms (rs4767860, rs7132778, rs7953150) of the SHP2 gene were genotyped using the Kompetitive Allele-Specific Polymerase Chain Reaction method.

RESULTS

Genotypes of rs4767860 (AA, AG + AA) and rs7132778 (AA, AC + AA), and alleles of rs4767860 (A) and rs7132778 (A) were associated with SLE risk. Genotype AA of rs7132778 and allele A of rs7132778 and rs7953150 were associated with oral ulcers in SLE patients. Allele C of rs7132778 and genotype AA and allele A of rs7953150 were associated with pyuria. Patients who carried AA genotype and allele A of rs7953150 are more likely to develop hypocomplementemia. AA and AG genotype frequencies are more raised in patients with SLE with alopecia than in those without alopecia. Patients who carried AA and AG genotypes of rs4767860 had elevated C-reactive protein levels.

CONCLUSION

Gene polymorphisms of SHP2 (rs4767860, rs7132778) are relevant to SLE susceptibility.

Fragment-Based Discovery of Novel VE-PTP Inhibitors Using Orthogonal Biophysical Techniques

Tyrosine phosphorylation is an essential post-translational modification that regulates various biological events and is implicated in many diseases including cancer and atherosclerosis. Vascular endothelial protein tyrosine phosphatase (VE-PTP), which plays an important role in vascular homeostasis and angiogenesis, is therefore an attractive drug target for these diseases. However, there are still no drugs targeting PTP including VE-PTP. In this paper, we report the discovery of a novel VE-PTP inhibitor, Cpd-2, by fragment-based screening combining various biophysical techniques. Cpd-2 is the first VE-PTP inhibitor with a weakly acidic structure and high selectivity, unlike known strongly acidic inhibitors. We believe that this compound represents a new possibility for the development of bioavailable VE-PTP inhibitors.

An In Silico Study Investigating Camptothecin-Analog Interaction with Human Protein Tyrosine Phosphatase, SHP2 (PTPN11)

The human PTPN11 gene encodes for the src tyrosine phosphatase protein (SHP2) is now gaining much attention in many disorders, particularly its oncogenic involvement in many types of cancer. Efforts in developing molecules targeting SHP2 with high efficacy are the future of drug discovery and chemotherapy. However, the interaction of a new camptothecin analog with the catalytic domain of SHP2 protein remains unknown. Therefore, this study aims to provide in silico rationale for the recognition and binding of FL118 and irinotecan with the catalytic domain of human protein tyrosine phosphatase-SHP2 (PTPc-SH2-SHP2, chain A). The docking interaction of the human SHP2 protein's catalytic domain as well as Y279C and R465G mutants with FL118 and irinotecan ligands were calculated and analyzed using the Autodock 4.2 programme, setting the docking grid to target the protein's active site. The camptothecin analog FL118 had the best lowest negative affinity energies with PTPc-SHP2 wildtype and SHP2-Y279C mutant model (-7.54 Kcal/mol and -6.94 Kcal/mol, respectively). Moreover, the protein-ligand complexes revealed several hydrogen bond interactions reflecting the degree of stability that each structure possesses, with the FL118-SHP2-wildtype forming the most stable complex among the structures. In addition, the FL118-SHP2 wildtype complex was validated for RMSD, RMSF, hydrogen bonds, and salt bridges. This revealed that the complex generated became stable over time. This in silico rationale identifies the novel FL118 camptothecin analog as a potent selective inhibitor of PTPc-SH2 domain of SHP2 protein, paving way for further in vitro investigations into the interactions and binding activity of analogs with SHP2 for potential therapeutic applications in PTPN11-associated disorders.

SHP2: its association and roles in systemic lupus erythematosus

OBJECTIVE

Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease. Src homology 2 domain containing protein tyrosine phosphatase (SHP2) is a member of the protein tyrosine phosphatases (PTPs) family. To date, relationship between SHP2 and SLE pathogenesis is not elucidated.

METHOD

We measured plasma levels of SHP2 in 328 SLE patients, 78 RA patients, 80 SS patients and 79 healthy controls by ELISA, and discussed association of SHP2 in SLE patients, potential of plasma SHP2 as a SLE biomarker. Moreover, histological and serological changes were evaluated by flow cytometry, HE/Masson examination, immunofluorescence test in pristane-induced lupus mice after SHP2 inhibitor injection to reveal role of SHP2 in lupus development.

RESULTS

Results indicated that SHP2 plasma levels were upregulated in SLE patients and correlated with some clinical, laboratory characteristics such as proteinuria, pyuria, and may be a potential biomarker for SLE. After SHP2 inhibitor treatment, hepatosplenomegaly and histological severity of the kidney in lupus mice were improved. SHP2 inhibitor reversed DCs, Th1, and Th17 cells differentiation and downregulated inflammatory cytokines (IL-4, IL-6, IL-10, IL-17A, IFN-γ and TNF-α) and autoantibodies (ANA, anti-dsDNA) production in pristane-lupus mice.

CONCLUSION

In summary, SHP2 correlated with SLE pathogenesis and promoted the development of lupus.

Evolving cognition of the JAK-STAT signaling pathway: autoimmune disorders and cancer

The Janus kinase (JAK) signal transducer and activator of transcription (JAK-STAT) pathway is an evolutionarily conserved mechanism of transmembrane signal transduction that enables cells to communicate with the exterior environment. Various cytokines, interferons, growth factors, and other specific molecules activate JAK-STAT signaling to drive a series of physiological and pathological processes, including proliferation, metabolism, immune response, inflammation, and malignancy. Dysregulated JAK-STAT signaling and related genetic mutations are strongly associated with immune activation and cancer progression. Insights into the structures and functions of the JAK-STAT pathway have led to the development and approval of diverse drugs for the clinical treatment of diseases. Currently, drugs have been developed to mainly target the JAK-STAT pathway and are commonly divided into three subtypes: cytokine or receptor antibodies, JAK inhibitors, and STAT inhibitors. And novel agents also continue to be developed and tested in preclinical and clinical studies. The effectiveness and safety of each kind of drug also warrant further scientific trials before put into being clinical applications. Here, we review the current understanding of the fundamental composition and function of the JAK-STAT signaling pathway. We also discuss advancements in the understanding of JAK-STAT-related pathogenic mechanisms; targeted JAK-STAT therapies for various diseases, especially immune disorders, and cancers; newly developed JAK inhibitors; and current challenges and directions in the field.

PTP4A2 promotes lysophagy by dephosphorylation of VCP/p97 at Tyr805

Overexpression of PTP4A phosphatases are associated with advanced cancers, but their biological functions are far from fully understood due to limited knowledge about their physiological substrates. VCP is implicated in lysophagy via collaboration with specific cofactors in the ELDR complex. However, how the ELDR complex assembly is regulated has not been determined. Moreover, the functional significance of the penultimate and conserved Tyr805 phosphorylation in VCP has not been established. Here, we use an unbiased substrate trapping and mass spectrometry approach and identify VCP/p97 as a bona fide substrate of PTP4A2. Biochemical studies show that PTP4A2 dephosphorylates VCP at Tyr805, enabling the association of VCP with its C-terminal cofactors UBXN6/UBXD1 and PLAA, which are components of the ELDR complex responsible for lysophagy, the autophagic clearance of damaged lysosomes. Functionally, PTP4A2 is required for cellular homeostasis by promoting lysophagy through facilitating ELDR-mediated K48-linked ubiquitin conjugate removal and autophagosome formation on the damaged lysosomes. Deletion of Ptp4a2 in vivo compromises the recovery of glycerol-injection induced acute kidney injury due to impaired lysophagy and sustained lysosomal damage. Taken together, our data establish PTP4A2 as a critical regulator of VCP and uncover an important role for PTP4A2 in maintaining lysosomal homeostasis through dephosphorylation of VCP at Tyr805. Our study suggests that PTP4A2 targeting could be a potential therapeutic approach to treat cancers and other degenerative diseases by modulating lysosomal homeostasis and macroautophagy/autophagy.Abbreviations: AAA+: ATPases associated with diverse cellular activities; AKI: acute kidney injury; CBB: Coomassie Brilliant Blue; CRISPR: clustered regularly interspaced short palindromic repeats; ELDR: endo-lysosomal damage response; GFP: green fluorescent protein; GST: ‎glutathione S-transferase; IHC: immunohistochemistry; IP: immunoprecipitation; LAMP1: lysosomal-associated membrane protein 1; LC-MS: liquid chromatography-mass spectrometry; LGALS3/Gal3: galectin 3; LLOMe: L-leucyl-L-leucine methyl ester; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MEF: mouse embryonic fibroblast; PLAA: phospholipase A2, activating protein; PTP4A2: protein tyrosine phosphatase 4a2; PUB: NGLY1/PNGase/UBA- or UBX-containing protein; PUL: PLAP, Ufd3, and Lub1; TFEB: transcription factor EB; UBXN6/UBXD1: UBX domain protein 6; UPS: ubiquitin-proteasome system; VCP/p97: valosin containing protein; VCPIP1: valosin containing protein interacting protein 1; YOD1: YOD1 deubiquitinase.

Targeting protein phosphatases in cancer immunotherapy and autoimmune disorders

Protein phosphatases act as key regulators of multiple important cellular processes and are attractive therapeutic targets for various diseases. Although extensive effort has been dedicated to phosphatase-targeted drug discovery, early expeditions for competitive phosphatase inhibitors were plagued by druggability issues, leading to the stigmatization of phosphatases as difficult targets. Despite challenges, persistent efforts have led to the identification of several drug-like, non-competitive modulators of some of these enzymes - including SH2 domain-containing protein tyrosine phosphatase 2, protein tyrosine phosphatase 1B, vascular endothelial protein tyrosine phosphatase and protein phosphatase 1 - reigniting interest in therapeutic targeting of phosphatases. Here, we discuss recent progress in phosphatase drug discovery, with emphasis on the development of selective modulators that exhibit biological activity. The roles and regulation of protein phosphatases in immune cells and their potential as powerful targets for immuno-oncology and autoimmunity indications are assessed.

Protein tyrosine phosphatase non-receptor type 12 suppresses tumor progression in osteosarcoma cells

BACKGROUND

Protein tyrosine phosphatase non-receptor 12 (PTPN12) plays a prominent role in various cancers as a tumor suppressor. However, the expression of PTPN12 and its biological functions in osteosarcoma (OS) remains to be determined.

METHODS

PTPN12 expression in OS was explored in public databases and detected by immunohistochemistry and Western blot. The cell viability was determined by Cell Counting Kit-8 (CCK-8) assay and colony formation. The cell migration and invasion were assessed by the Transwell assay. Flow cytometry analysis was applied to detect cell apoptosis and cell cycle distribution. To investigate the related mechanism, the levels of EGFR and downstream proteins were detected by Western blot.

RESULTS

PTPN12 expression was significantly decreased in OS samples in GEO database and our hospital. OS cell lines in Cancer Cell Line Encyclopedia (CCLE) database and our cultured OS cells also demonstrated low PTPN12 expression. Lentivirus-induced overexpression of PTPN12 significantly inhibited the cell viability, migration and invasion of 143B and U2OS cells. The results of flow cytometry found that PTPN12 overexpression promoted cell apoptosis and induced cell cycle arrest at G1 phase in 143B and U2OS cells. The phosphorylation levels of EGFR and subsequent proteins of the PI3K/AKT and ERK pathways were inactivated as a result of PTPN12 overexpression in OS.

CONCLUSION

PTPN12 plays a tumor suppressive role in OS cells. Restoring of PTPN12 activity may provide new insights for the treatment of this disease.

CDC14B is a favorable biomarker for recurrence and prognosis of GBM

BACKGROUND

Glioblastoma (GBM) is the most common and lethal primary brain tumor in adults. The treatment options of GBM are quite few and the prognosis of GBM is very dismal. Identifying the effective and prognostic biomarker is important for molecular classification and individual treatment of patients. CDC14 is a conserved dual specificity phosphatase functioning mainly in mitosis and DNA respiration. The expression and function of CDC14 family in tumor progression is still elusive.

MATERIALS AND METHODS

In our study, we established a retrospective GBM cohort consisting of 135 patients who underwent the surgery and received standard treatment therapy. We compared the expression of CDC14A and CDC14B in GBM and tumor-adjacent tissues by retrieving data from TCGA and qPCR. With immunohistochemistry (IHC), we detected the expression of CDC14B in the cohort, and analyzed the correlation between CDC14B and clinicopathological factors by chi-square test. The significance of CDC14B on GBM recurrence and prognosis was assessed by univariate and multivariate analyses.

RESULTS

CDC14B, but not CDC14A, had a higher expression in GBM tissues than in tumor-adjacent tissues. High CDC14B was correlated with high progression-free survival (PFS) rate and overall survival (OS) rate of GBM. In the Cox-regression model, CDC14B was an independent and favorable biomarker indicating low risk of recurrence and GBM-related death.

CONCLUSIONS

High CDC14B is correlated with high GBM PFS and OS rate, and CDC14B is an independent biomarker of GBM, indicating low recurrence and favorable prognosis. Our study reveals a new biomarker of GBM which could indicate the recurrence and prognosis of GBM. This may help stratify the high-risk patients and modify the prognostic assessment based on molecular features.

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.

Shp2 Deficiency in Kupffer Cells and Hepatocytes Aggravates Hepatocarcinogenesis by Recruiting Non-Kupffer Macrophages

BACKGROUND & AIMS

Complex communications between hepatocytes and Kupffer cells (KCs) are known to drive or suppress hepatocarcinogenesis, with controversial data in the literature. In previous experiments that aimed to decipher hepatocyte/KC interactions, we unexpectedly unveiled a tumor-suppressing effect of polyinosinic-polycytidylic acid, a widely used inducer of MX dynamin like GTPase 1 (Mx1)-cre expression, which questioned a theory of interleukin 1a/6 cytokine circuit in hepatocyte/KC communication. The goal of this study was to clarify the controversy and decipher unique functions of KCs and non-KC macrophages in liver tumorigenesis.

METHODS

We used the C-type lectin domain family 4 member F (Clec4f)-cre system to delete Src-homology 2 domain-containing tyrosine phosphatase 2 (Shp2)/protein tyrosine phosphatase nonreceptor 11 (Ptpn11) in KCs, and a combination of Clec4f-cre and adeno-associated virus-cre to delete Shp2 in KCs and hepatocytes to investigate the effects on hepatocellular carcinoma development and immune cell compositions/activities.

RESULTS

Ablating Shp2 in KCs generated a tumor-promoting niche, which was exacerbated further by concurrent removal of Shp2 in both KCs and hepatocytes. Shp2 deficiency induced KC apoptosis and decreased its numbers, which induced compensatory recruitment of bone marrow-derived monocytes into liver. These newly recruited monocytes differentiated into non-KC macrophages with tumor-associated macrophage function, leading to aggravated tumor progression through down-regulation of CD8 T cells. Tumor-associated macrophage blockade by anti-chemokine (C-C motif) ligand 2 (CCL2) antibody inhibited hepatocellular carcinoma progression, while depletion of all macrophages had a tumor-promoting effect by increasing myeloid-derived suppressor cells (M-MDSCs) and decreasing CD8 T cells.

CONCLUSIONS

Shp2 loss in KCs or hepatocytes generated a protumorigenic microenvironment, which was exacerbated by its removal in both cell types. These results show the complexity of intercellular signaling events in liver tumorigenesis and raises caution on the use of specific Shp2 inhibitor in liver cancer therapy. Transcript profiling: RNA sequencing data are available at Gene Expression Omnibus (GSE222594).

Burst kinetics and CNNM binding are evolutionarily conserved properties of phosphatases of regenerating liver

Phosphatases of regenerating liver (PRL or PTP4A) are a family of enigmatic protein phosphatases implicated in cell growth and metabolism. Despite their relevance in metastatic cancer, much remains unknown about the PRL family. They act as pseudophosphatases to regulate the CNNM family of magnesium transporters yet also have enzymatic activity on unknown substrates. In mammals, PRLs are mostly found trapped in an intermediate state that regulates their pseudophosphatase activity. Phosphocysteine, which is formed as an intermediate in the phosphatase catalytic cycle, is inefficiently hydrolyzed leading to burst enzyme kinetics and turnover numbers of less than one per hour. In flies, PRLs have recently been shown to have neuroprotective and neurodevelopmental roles raising the question whether they act as phosphatases, pseudophosphatases, or both. Here, we characterize the evolutionary development of PRLs and ask whether their unique structural and functional properties are conserved. We purified recombinant PRL proteins from 15 phylogenetically diverse organisms and characterized their catalytic activities and ability to bind CNNM proteins. We observed PRLs from humans to amoebae form a stable phosphocysteine intermediate and exhibit burst kinetics. Isothermal titration calorimetry experiments confirmed that the PRL-CNNM interaction is broadly conserved with nanomolar affinity in vertebrates. Lastly, we determined the crystal structure of the Drosophila melanogaster PRL-CNNM complex and identified mutants that specifically impair either phosphatase activity or CNNM binding. Our results reveal the unique properties of PRLs are conserved throughout the animal kingdom and open the door to using model organisms to dissect PRL function in cell signaling.

KMT2D deficiency drives lung squamous cell carcinoma and hypersensitivity to RTK-RAS inhibition

Lung squamous cell carcinoma (LUSC) represents a major subtype of lung cancer with limited treatment options. KMT2D is one of the most frequently mutated genes in LUSC (>20%), and yet its role in LUSC oncogenesis remains unknown. Here, we identify KMT2D as a key regulator of LUSC tumorigenesis wherein Kmt2d deletion transforms lung basal cell organoids to LUSC. Kmt2d loss increases activation of receptor tyrosine kinases (RTKs), EGFR and ERBB2, partly through reprogramming the chromatin landscape to repress the expression of protein tyrosine phosphatases. These events provoke a robust elevation in the oncogenic RTK-RAS signaling. Combining SHP2 inhibitor SHP099 and pan-ERBB inhibitor afatinib inhibits lung tumor growth in Kmt2d-deficient LUSC murine models and in patient-derived xenografts (PDXs) harboring KMT2D mutations. Our study identifies KMT2D as a pivotal epigenetic modulator for LUSC oncogenesis and suggests that KMT2D loss renders LUSC therapeutically vulnerable to RTK-RAS inhibition.

The Structure, Function and Regulation of Protein Tyrosine Phosphatase Receptor Type J and Its Role in Diseases

Protein tyrosine phosphatase receptor type J (PTPRJ), also known as DEP-1, HPTPη, or CD148, belongs to the R3 subfamily of receptor protein tyrosine phosphatases (RPTPs). It was first identified as an antioncogene due to its protein level being significantly downregulated in most epithelial tumors and cancer cell lines (e.g., colon, lung, thyroid, breast, and pancreas). PTPRJ regulates mouse optic nerve projection by inhibiting the phosphorylation of the erythropoietin-producing hepatocellular carcinoma (Eph) receptor and abelson murine leukemia viral oncogene homolog 1 (c-Abl). PTPRJ is crucial for metabolism. Recent studies have demonstrated that PTPRJ dephosphorylates JAK2 at positions Y813 and Y868 to inhibit leptin signaling. Akt is more phosphorylated at the Ser473 and Thr308 sites in Ptprj^-/- mice, suggesting that PTPRJ may be a novel negative regulator of insulin signaling. PTPRJ also plays an important role in balancing the pro- and anti-osteoclastogenic activity of the M-CSF receptor (M-CSFR), and in maintaining NFATc1 expression during the late stages of osteoclastogenesis to promote bone-resorbing osteoclast (OCL) maturation. Furthermore, multiple receptor tyrosine kinases (RTKs) as substrates of PTPRJ are probably a potential therapeutic target for many types of diseases, such as cancer, neurodegenerative diseases, and metabolic diseases, by inhibiting their phosphorylation activity. In light of the important roles that PTPRJ plays in many diseases, this review summarizes the structural features of the protein, its expression pattern, and the physiological and pathological functions of PTPRJ, to provide new ideas for treating PTPRJ as a potential therapeutic target for related metabolic diseases and cancer.

Pan-cancer analyses of classical protein tyrosine phosphatases and phosphatase-targeted therapy in cancer

Protein tyrosine phosphatases function in dephosphorylating target proteins to regulate signaling pathways that control a broad spectrum of fundamental physiological and pathological processes. Detailed knowledge concerning the roles of classical PTPs in human cancer merits in-depth investigation. We comprehensively analyzed the regulatory mechanisms and clinical relevance of classical PTPs in more than 9000 tumor patients across 33 types of cancer. The independent datasets and functional experiments were employed to validate our findings. We exhibited the extensive dysregulation of classical PTPs and constructed the gene regulatory network in human cancer. Moreover, we characterized the correlation of classical PTPs with both drug-resistant and drug-sensitive responses to anti-cancer drugs. To evaluate the PTP activity in cancer prognosis, we generated a PTPscore based on the expression and hazard ratio of classical PTPs. Our study highlights the notable role of classical PTPs in cancer biology and provides novel intelligence to improve potential therapeutic strategies based on pTyr regulation.