Stepping out of the shadows: Oncogenic and tumor-promoting protein tyrosine phosphatases

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.

Protein tyrosine phosphatase nonreceptor 2: A New biomarker for digestive tract cancers

In this editorial, the roles of protein tyrosine phosphatase nonreceptor 2 (PTPN2) in oncogenic transformation and tumor behavior and its potential as a therapeutic target in the context of gastrointestinal (GI) cancers are presented with respect to the article by Li et al published in ninth issue of the World Journal of Gastrointestinal Oncology. PTPN2 is a member of the protein tyrosine phosphatase family of signaling proteins that play crucial roles in the regulation of inflammation and immunity. Accordingly, early findings highlighted the contribution of PTPN2 to the pathogenesis of inflammatory and autoimmune disorders related to its dysfunction. On the other hand, recent studies have indicated that PTPN2 has many different roles in different cancer types, which is associated with the complexity of its regulatory network. PTPN2 dephosphorylates and inactivates EGFR, SRC family kinases, JAK1 and JAK3, and STAT1, STAT3, and STAT5 in cell type- and context-dependent manners, which indicates that PTPN2 can perform either prooncogenic or anti-oncogenic functions depending on the tumor subtype. While PTPN2 has been suggested as a potential therapeutic target in cancer treatment, to the best of ourknowledge, no clear treatment protocol has referred to PTPN2. Although there are only few studies that investigated PTPN2 expression in the GI system cancers, which is a potential limitation, the association of this protein with tumor behavior and the influence of PTPN2 on many therapy-related signaling pathways emphasize that PTPN2 could serve as a new molecular biomarker to predict tumor behavior and as a target for therapeutic intervention against GI cancers. In conclusion, more studies should be performed to better understand the prognostic and therapeutic potential of PTPN2 in GI tumors, especially in tumors resistant to therapy.

Four-dimensional trapped ion mobility spectrometry proteomics reveals circulating extracellular vesicles encapsulated drivers of nasopharyngeal carcinoma distant dissemination

Nasopharyngeal carcinoma (NPC) is a head and neck cancer with a high propensity for early metastatic spread. Emerging evidence shows that extracellular vesicles (EVs) are key players in cancer metastasis, but their role in NPC metastasis remains poorly understood. We here present the first description of the proteomic and functional profiles of serum-derived circulating small EVs in metastatic NPC patients. To enhance the capture of low-abundance signaling proteins in EVs, timsTOF-based four-dimensional label-free quantitative proteomics was employed. We found that metastatic NPC patients (M-NPC-EVs) exhibited the highest serum EV levels compared to locoregional patients (L-NPC-EVs) and healthy subjects (Normal-EVs). The proteome of M-NPC-EVs differed substantially from L-NPC-EVs and was functionally enriched in pathways regulating cell polarity and motility, glucose metabolism, and angiogenesis. Functional assays testing individual EV samples demonstrated that M-NPC-EVs pronouncedly enhanced NPC cell migration, invasion, and the formation of lamellipodia and filopodia in vitro, and promoted angiogenesis in subcutaneous Matrigel plugs in vivo. In silico analyses suggested that PTPRA, TPI1 and GPI highly enriched in M-NPC-EVs were putative drivers underlying the motogenic and angiogenic activities of M-NPC-EVs, and their high expression levels were associated with a poor prognosis of NPC patients. The increased expression of PTPRA, TPI1 and GPI in M-NPC-EVs was then validated in an independent cohort consisting of 175 NPC patients (locoregional n = 114; metastatic n = 61). Together, utilizing patient-derived EVs, we mimicked the potential pro-metastatic functions of EVs in NPC patients in vitro and in vivo and provided novel insights into their bioactive cargoes.

EphA2 specific chimeric antigen receptor engineered T cells for the treatment of prostate cancer

Erythropoietin-producing hepatocyte receptor A2 (EphA2) is an attractive target for immunotherapy due to its high expression in a variety of solid tumors including prostate cancer. Among various types of immunotherapeutics, chimeric antigen receptor T (CAR-T) cell therapy has made promising progress in hematological and solid tumors. Here, we detected the expression of EphA2 in prostate cancer cells and developed a second-generation CAR targeting EphA2 with CD28 as a co-stimulatory receptor to explore its tumor suppressive potential for prostate cancer in vitro and in vivo. EphA2 was highly expressed on the surface of PC3 and DU145 cells. EphA2 CART cells effectively inhibited prostate cancer growth in an antigen-dependent manner in vitro and in vivo. In addition, tumor cells could stimulate the proliferation of CAR-T cells and the release of cytokine IFN-γ in vitro. These findings shed light on EphA2 as a potential target for prostate cancer, promising EphA2 specific CAR-T cells for the treatment of prostate cancer.

Blood mir-331-3p is a potential diagnostic marker for giant panda (Ailuropoda melanoleuca) testicular tumor

BACKGROUND

In recent years, several giant pandas have suffered from testicular tumor, which has seriously affected giant panda health. However, the pathogenesis of testicular tumor in giant panda is still unclear. Studies have shown that miRNAs are involved in the occurrence and development of a variety of cancers. However, the effect of miRNAs on giant panda testicular tumor has been little studied. Therefore, this study explored the pathogenesis of giant panda testicular tumor through miRNA and mRNA sequencing, and screened out diagnostic markers of testicular tumor.

RESULTS

Combined with phenotypic symptoms and pathological section results, three giant pandas were diagnosed with testicular tumor and divided into tumor group, and three other giant pandas were divided into normal group. A total of 29 differentially expressed miRNAs (DEmiRNAs) were screened by blood miRNA-seq, and 3149 target gene candidates were predicted. Functional enrichment analysis showed that the target genes were mainly involved in intermembrane lipid transfer and ATP-dependent chromatin remodeling. However, only 5 DEmiRNAs were screened by miRNA-seq of blood-derived exosomes and 364 target genes were predicted, which were mainly involved in antigen processing and presentation. In addition, 216 differentially expressed genes (DEGs) were screened by RNA-seq, and functional enrichment analysis showed that tumor-specific DEGs significantly enriched to protein phosphorylation. Spearman correlation analysis of miRNA-mRNA showed that the expressions of miR-331-3p and PKIG were significantly positively correlated (spearman = 0.943, p < 0.01), while the expressions of miR-331-3p and ENSAMEG00000013628 were significantly negatively correlated (spearman= -0.829, p < 0.05). RT-PCR showed that the expression of miR-331-3p was significantly decreased in giant panda with tumor (p < 0.01).

CONCLUSIONS

blood miRNAs and exosomal miRNAs exhibit distinct regulatory patterns concerning giant panda testicular tumor, potentially reflecting divergent biological processes in the disease's etiology. Meanwhile, miR-331-3p could be used as a potential diagnostic marker for giant panda testicular tumor. Our findings are conducive to the rapid clinical diagnosis of testicular tumor in giant pandas, and are also expected to provide scientific reference for further research on the pathogenesis of testicular tumor.

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.

Protein tyrosine phosphatase 1B (PTP1B) function, structure, and inhibition strategies to develop antidiabetic drugs

Tyrosine protein phosphatase non-receptor type 1 (PTP1B; also known as protein tyrosine phosphatase 1B) is a member of the protein tyrosine phosphatase (PTP) family and is a soluble enzyme that plays an essential role in different physiological processes, including the regulation of metabolism, specifically in insulin and leptin sensitivity. PTP1B is crucial in the pathogenesis of type 2 diabetes mellitus and obesity. These biological functions have made PTP1B validated as an antidiabetic and anti-obesity, and potentially anticancer, molecular target. Four main approaches aim to inhibit PTP1B: orthosteric, allosteric, bidentate inhibition, and PTPN1 gene silencing. Developing a potent and selective PTP1B inhibitor is still challenging due to the enzyme's ubiquitous expression, subcellular location, and structural properties. This article reviews the main advances in the study of PTP1B since it was first isolated in 1988, as well as recent contextual information related to the PTP family to which this protein belongs. Furthermore, we offer an overview of the role of PTP1B in diabetes and obesity, and the challenges to developing selective, effective, potent, bioavailable, and cell-permeable compounds that can inhibit the enzyme.

The protein tyrosine phosphatase PPH-7 is required for fertility and embryonic development in C. elegans at elevated temperatures

Post-translational modifications are key in the regulation of activity, structure, localization, and stability of most proteins in eukaryotes. Phosphorylation is potentially the most studied post-translational modification, also due to its reversibility and thereby the regulatory role this modification often plays. While most research attention was focused on kinases in the past, phosphatases remain understudied, most probably because the addition and presence of the modification is more easily studied than its removal and absence. Here, we report the identification of an uncharacterized protein tyrosine phosphatase PPH-7 in C. elegans, a member of the evolutionary conserved PTPN family of phosphatases. Lack of PPH-7 function led to reduction of fertility and embryonic lethality at elevated temperatures. Proteomics revealed changes in the regulation of targets of the von Hippel-Lindau (VHL) E3 ligase, suggesting a potential role for PPH-7 in the regulation of VHL.

Single-cell transcriptomic analysis deciphers heterogenous cancer stem-like cells in colorectal cancer and their organ-specific metastasis

OBJECTIVE

Metastasis is the major cause of cancer death. However, what types of heterogenous cancer cells in primary tumour and how they metastasise to the target organs remain largely undiscovered.

DESIGN

We performed single-cell RNA sequencing and spatial transcriptomic analysis in primary colorectal cancer (CRC) and metastases in the liver (lCRC) or ovary (oCRC). We also conducted immunofluorescence staining and functional experiments to examine the mechanism.

RESULTS

Integrative analyses of epithelial cells reveal a stem-like cell cluster with high protein tyrosine phosphatase receptor type O (PTPRO) and achaete scute-like 2 (ASCL2) expression as the metastatic culprit. This cell cluster comprising distinct subpopulations shows distinct liver or ovary metastatic preference. Population 1 (P1) cells with high delta-like ligand 4 (DLL4) and MAF bZIP transcription factor A (MAFA) expression are enriched in primary CRC and oCRC, thus may be associated with ovarian metastasis. P3 cells having a similar expression pattern as cholangiocytes are found mainly in primary CRC and lCRC, presuming to be likely the culprits that specifically metastasise to the liver. Stem-like cells interacted with cancer-associated fibroblasts and endothelial cells via the DLL4-NOTCH signalling pathway to metastasise from primary CRC to the ovary. In the oCRC microenvironment, myofibroblasts provide cancer cells with glutamine and perform a metabolic reprogramming, which may be essential for cancer cells to localise and develop in the ovary.

CONCLUSION

We uncover a mechanism for organ-specific CRC metastasis.

miR-146a-5p Alleviates Radiation-Induced Liver Fibrosis by Regulating PTPRA-SRC Signaling in Mice

Patients with hepatobiliary tumors who accept radiotherapy are at risk for radiation-induced liver fibrosis. MicroRNAs (miRNAs) have been implicated in the pathogenesis of radiation-induced liver damage and possess potential as novel biomarkers and therapeutic targets. However, the role of miR-146a-5p in radiation-induced liver fibrosis is less well understood. The current study was designed to evaluate the role of miR-146a-5p in radiation-induced liver fibrosis in mice and to investigate the possible mechanisms involved in miR-146a-5p-mediated effects. The experiments were performed on Institute of Cancer Research (ICR) mice which received fractionated radiation (30 Gy in 5 fractions) to the liver. The results show radiation could induce histopathological changes, liver dysfunction and fibrosis accompanied with decreased miR-146a-5p expression. miR-146a-5p agomir treatment resulted in recovery of liver function and reduced the amount of alpha-smooth muscle actin (α-SMA), collagen 1, protein tyrosine phosphatase receptor type A (PTPRA) and phosphorylated SRC in the livers of irradiated mice. Therefore, our study reveals that miR-146a-5p inhibits the progression of hepatic fibrosis after radiation treatment. And the beneficial role of miR-146a-5p may be relevant to PTPRA-SRC signaling pathway.

Clustering of colon, lung, and other cancer susceptibility genes with protein tyrosine phosphatases and protein kinases in multiple short genomic regions

Interactions of large gene families are poorly understood. We found that human, mouse, and rat colon and lung cancer susceptibility genes, presently considered as separate gene families, were frequently pairwise linked. The orthologous mouse map positions of 142 of 159 early discovered colon and lung cancer susceptibility genes formed 41 genomic clusters conserved >70 million years. These linked gene pairs concordantly affected both tumors and their majority was linked with two other gene families - protein tyrosine phosphatases and cancer driver protein kinases. 25% of both protein tyrosine phosphatases and protein kinases mapped <1 cM from a colon or lung cancer susceptibility gene, and 50% in <3 cM. Similar linkage was detected with most other human susceptibility genes that controlled 29 different cancer types. This concentration of tumor susceptibility genes with protein tyrosine phosphatases and driver protein kinases in multiple relatively short genomic regions suggests their possible functional diversity.

Study on the allosteric activation mechanism of SHP2 via elastic network models and neural relational inference molecular dynamics simulation

As a ubiquitous protein tyrosine phosphatase, SHP2 is involved in PD-1/PD-L1 mediated tumor immune escape and undergoes substantial conformational changes. Therefore, it is considered an ideal target for tumor intervention. However, the allosteric mechanisms of SHP2 binding PD-1 intracellular ITIM/ITSM phosphopeptides remain unclear, which greatly hinders the development of novel structure-based anticancer allosteric inhibitors. In this work, the open and closed structural models of SHP2 are first constructed based on this knowledge; next their motion modes are investigated via elastic network models such as the Gaussian network model (GNM), anisotropic network model (ANM) and adaptive anisotropic network model (aANM); and finally, a possible allosteric signaling pathway is proposed using a neural relational inference molecular dynamics (NRI-MD) simulation embedded with an artificial intelligence (AI) strategy. In GNM and ANM, the N-SH2, C-SH2 and PTP domains all exhibit distinct dynamics partitions, and the N-SH2/C-SH2 regions show a rigid rotation relative to PTP. According to a series of intermediate snapshots given by aANM, N-SH2 is first identified with pY223 specifically, inducing a D'E-loop to change from β-sheets to random coils, and then, C-SH2 serves as a fulcrum to drive N-SH2 to rotate 110° completely away from the original active sites of PTP. Finally, a possible allosteric signaling-transfer path for SHP2, namely R220-R138-T108-R32, is proposed based on NRI-MD sampling. This work provides a possible allosteric mechanism of SHP2, which is helpful for the following design of novel allosteric inhibitors and is expected to be used in clinical synergies with PD-1 monoclonal antibody.

Clustering of phosphatase RPTPα promotes Src signaling and the arthritogenic action of synovial fibroblasts

Receptor-type protein phosphatase α (RPTPα) promotes fibroblast-dependent arthritis and fibrosis, in part, by enhancing the activation of the kinase SRC. Synovial fibroblasts lining joint tissue mediate inflammation and tissue damage, and their infiltration into adjacent tissues promotes disease progression. RPTPα includes an ectodomain and two intracellular catalytic domains (D1 and D2) and, in cancer cells, undergoes inhibitory homodimerization, which is dependent on a D1 wedge motif. Through single-molecule localization and labeled molecule interaction microscopy of migrating synovial fibroblasts, we investigated the role of RPTPα dimerization in the activation of SRC, the migration of synovial fibroblasts, and joint damage in a mouse model of arthritis. RPTPα clustered with other RPTPα and with SRC molecules in the context of actin-rich structures. A known dimerization-impairing mutation in the wedge motif (P210L/P211L) and the deletion of the D2 domain reduced RPTPα-RPTPα clustering; however, it also unexpectedly reduced RPTPα-SRC association. The same mutations also reduced recruitment of RPTPα to actin-rich structures and inhibited SRC activation and cellular migration. An antibody against the RPTPα ectodomain that prevented the clustering of RPTPα also inhibited RPTPα-SRC association and SRC activation and attenuated fibroblast migration and joint damage in arthritic mice. A catalytically inactivating RPTPα-C469S mutation protected mice from arthritis and reduced SRC activation in synovial fibroblasts. We conclude that RPTPα clustering retains it to actin-rich structures to promote SRC-mediated fibroblast migration and can be modulated through the extracellular domain.

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.

Encapsulated Oxovanadium(IV) and Dioxovanadium(V) Complexes into Solid Lipid Nanoparticles Increase Cytotoxicity Against MDA-MB-231 Cell Line

Introduction

Solid lipid nanoparticles (SLN) have been considered lately as promising drug delivery system in treatment of many human diseases including cancers. We previously studied potential drug compounds that were effective inhibitors of PTP1B phosphatase - possible target for breast cancer treatment. Based on our studies, two complexes were selected for encapsulation into the SLNs, the compound 1 ([VO(dipic)(dmbipy)] · 2 H₂O) and compound 2 ([VOO(dipic)](2-phepyH) · H₂O). Here, we investigate the effect of encapsulation of those compounds on cell cytotoxicity against MDA-MB-231 breast cancer cell line. The study also included the stability evaluation of the obtained nanocarriers with incorporated active substances and characterization of their lipid matrix. Moreover, the cell cytotoxicity studies against the MDA-MB-231 breast cancer cell line in comparison and in combination with vincristine have been performed. Wound healing assay was carried out to observe cell migration rate.

Methods

The properties of the SLNs such as particle size, zeta potential (ZP), and polydispersity index (PDI) were investigated. The morphology of SLNs was observed by scanning electron microscopy (SEM), while the crystallinity of the lipid particles was analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The cell cytotoxicity of complexes and their encapsulated forms was carried out against MDA-MB-231 breast cancer cell line using standard MTT protocols. The wound healing assay was performed using live imaging microscopy.

Results

SLNs with a mean size of 160 ± 25 nm, a ZP of -34.00 ± 0.5, and a polydispersity index of 30 ± 5% were obtained. Encapsulated forms of compounds showed significantly higher cytotoxicity also in co-incubation with vincristine. Moreover, our research shows that the best compound was complex 2 encapsulated into lipid nanoparticles.

Conclusion

We observed that encapsulation of studied complexes into SLNs increases their cell cytotoxicity against MDA-MB-231 cell line and enhanced the effect of vincristine.

Identification of the novel natural product inhibitors of SHP2 from the plant Toona sinensis: In vitro and in silico study

In this study, we tested the inhibitory activity of 45 natural products extracted from the plant Toona sinensis on SHP2 protein, and identified four natural product inhibitors. The natural product 1,2,3,6-Tetragalloylglucose (A-1) was first reported as a competitive inhibitor of SHP2, with an IC₅₀ value of 0.20 ± 0.029 μM and the selectivity of 1.8-fold and 4.35-fold to high homologous proteins SHP1 and PTP1B, respectively. Compound A-1 also showed high inhibitory activity on SHP2-E76K and SHP2-E76A mutants, with IC₅₀ values of 0.95 ± 0.21 μM and 0.29 ± 0.045 μM, respectively. Cell viability assay showed that compound A-1 could inhibit the proliferation of a variety of cancer cells. Apoptosis assay showed that compound A-1 could effectively induce apoptosis of KRAS^G12C-mut NCI-H23 and KRAS^G12S-mut A549 cells. Western blot assay showed that compound A-1 could down regulate the phosphorylation levels of Erk1/2 and Akt in NCI-H23 and A549 cells. Molecular docking showed that compound A-1 could effectively dock to the catalytic active region of SHP2. Molecular dynamics simulation explored the effect of compound A-1 on SHP2, revealing the deep-seated binding mechanism. This study would provide valuable clues for the development of SHP2 and its mutant inhibitors.

SCP4-STK35/PDIK1L complex is a dual phospho-catalytic signaling dependency in acute myeloid leukemia

Acute myeloid leukemia (AML) cells rely on phospho-signaling pathways to gain unlimited proliferation potential. Here, we use domain-focused CRISPR screening and identify the nuclear phosphatase SCP4 as a dependency in AML, yet this enzyme is dispensable in normal hematopoietic progenitor cells. Using CRISPR exon scanning and gene complementation assays, we show that the catalytic function of SCP4 is essential in AML. Through mass spectrometry analysis of affinity-purified complexes, we identify the kinase paralogs STK35 and PDIK1L as binding partners and substrates of the SCP4 phosphatase domain. We show that STK35 and PDIK1L function catalytically and redundantly in the same pathway as SCP4 to maintain AML proliferation and to support amino acid biosynthesis and transport. We provide evidence that SCP4 regulates STK35/PDIK1L through two distinct mechanisms: catalytic removal of inhibitory phosphorylation and by promoting kinase stability. Our findings reveal a phosphatase-kinase signaling complex that supports the pathogenesis of AML.

PTPRO is a therapeutic target and correlated with immune infiltrates in pancreatic cancer

As a member of protein tyrosine phosphatases (PTPs), the protein tyrosine phosphatase receptor type O (PTPRO) has attracted increasing attention for its important roles in cell signaling. Currently, the roles of PTPRO in human cancers remain elusive. Herein, we performed bioinformatic analyses and revealed the potential oncogenic role of PTPRO in specific cancer types. Further in vitro experiments indicated that inhibition of PTPRO suppresses the proliferative abilities of tumor cells in pancreatic cancer, blood cancer, and breast cancer. Moreover, small molecular PTPRO inhibitor could induce cell apoptosis and affect the cell cycle in pancreatic cancer. In addition, PTPRO expression promoted the infiltration of CD8+ T, macrophages, dendritic cells, and neutrophils, in pancreatic cancers. Our findings suggested PTPRO may serve as a potential drug target for pancreatic cancer.

Discovery of novel furanylbenzamide inhibitors that target oncogenic tyrosine phosphatase SHP2 in leukemia cells

Disturbance of the dynamic balance between tyrosine phosphorylation and dephosphorylation of signaling molecules, controlled by protein tyrosine kinases and protein tyrosine phosphatases (PTPs), is known to lead to the development of cancer. While most approved targeted cancer therapies are tyrosine kinase inhibitors, PTPs have long been stigmatized as undruggable and have only recently gained renewed attention in drug discovery. One PTP target is the Src-homology 2 domain-containing phosphatase 2 (SHP2). SHP2 is implicated in tumor initiation, progression, metastasis, and treatment resistance, primarily because of its role as a signaling nexus of the extracellular signal-regulated kinase pathway, acting upstream of the small GTPase Ras. Efforts to develop small molecules that target SHP2 are ongoing, and several SHP2 allosteric inhibitors are currently in clinical trials for the treatment of solid tumors. However, while the reported allosteric inhibitors are highly effective against cells expressing WT SHP2, none have significant activity against the most frequent oncogenic SHP2 variants that drive leukemogenesis in several juvenile and acute leukemias. Here, we report the discovery of novel furanylbenzamide molecules as inhibitors of both WT and oncogenic SHP2. Importantly, these inhibitors readily cross cell membranes, bind and inhibit SHP2 under physiological conditions, and effectively decrease the growth of cancer cells, including triple-negative breast cancer cells, acute myeloid leukemia cells expressing either WT or oncogenic SHP2, and patient-derived acute myeloid leukemia cells. These novel compounds are effective chemical probes of active SHP2 and may serve as starting points for therapeutics targeting WT or mutant SHP2 in cancer.

Recent advances in the development of allosteric protein tyrosine phosphatase inhibitors for drug discovery

Protein tyrosine phosphatases (PTPs) superfamily catalyzes tyrosine de-phosphorylation which affects a myriad of cellular processes. Imbalance in signal pathways mediated by PTPs has been associated with development of many human diseases including cancer, metabolic, and immunological diseases. Several compelling evidence suggest that many members of PTP family are novel therapeutic targets. However, the clinical development of conventional PTP-based active-site inhibitors originally was hampered by the poor selectivity and pharmacokinetic properties. In this regard, PTPs has been widely dismissed as "undruggable." Nonetheless, allosteric modulation has become increasingly an influential and alternative approach that can be exploited for drug development against PTPs. Unlike active-site inhibitors, allosteric inhibitors exhibit a remarkable target-selectivity, drug-likeness, potency, and in vivo activity. Intriguingly, there has been a high interest in novel allosteric PTPs inhibitors within the last years. In this review, we focus on the recent advances of allosteric inhibitors that have been explored in drug discovery and have shown an excellent result in the development of PTPs-based therapeutics. A special emphasis is placed on the structure-activity relationship and molecular mechanistic studies illustrating applications in chemical biology and medicinal chemistry.

Invadopodia, a Kingdom of Non-Receptor Tyrosine Kinases

Non-receptor tyrosine kinases (NRTKs) are crucial mediators of intracellular signaling and control a wide variety of processes such as cell division, morphogenesis, and motility. Aberrant NRTK-mediated tyrosine phosphorylation has been linked to various human disorders and diseases, among them cancer metastasis, to which no treatment presently exists. Invasive cancer cells leaving the primary tumor use invadopodia, feet-like structures which facilitate extracellular matrix (ECM) degradation and intravasation, to escape the primary tumor and disseminate into distant tissues and organs during metastasis. A major challenge in metastasis research is to elucidate the molecular mechanisms and signaling pathways underlying invadopodia regulation, as the general belief is that targeting these structures can potentially lead to the eradication of cancer metastasis. Non-receptor tyrosine kinases (NRTKs) play a central role in regulating invadopodia formation and function, but how they coordinate the signaling leading to these processes was not clear until recently. Here, we describe the major NRTKs that rule invadopodia and how they work in concert while keeping an accurate hierarchy to control tumor cell invasiveness and dissemination.

Cancer stem cell phosphatases

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

Druggable cancer phosphatases

The phosphorylation status of oncoproteins is regulated by both kinases and phosphatases. Kinase inhibitors are rarely sufficient for successful cancer treatment, and phosphatases have been considered undruggable targets for cancer drug development. However, innovative pharmacological approaches for targeting phosphatases have recently emerged. Here, we review progress in the therapeutic targeting of oncogenic Src homology region 2 domain-containing phosphatase-2 (SHP2) and tumor suppressor protein phosphatase 2A (PP2A) and select other druggable oncogenic and tumor suppressor phosphatases. We describe the modes of action for currently available small molecules that target phosphatases, their use in drug combinations, and advances in clinical development toward future cancer therapies.

The liposomal delivery of hydrophobic oxidovanadium complexes imparts highly effective cytotoxicity and differentiating capacity in neuroblastoma tumour cells

Oxidovanadium complexes with organic ligands are well known to have cytotoxic or differentiating capabilities against a range of cancer cell types. Their limited use in clinical testing though has resulted largely from uncertainties about the long-term toxicities of such complexes, due in part to the speciation to vanadate ions in the circulation. We hypothesised that more highly stable complexes, delivered using liposomes, may provide improved opportunities for oxidovanadium applications against cancer. In this study we sourced specifically hydrophobic forms of oxidovanadium complexes with the explicit aim of demonstrating liposomal encapsulation, bioavailability in cultured neuroblastoma cells, and effective cytotoxic or differentiating activity. Our data show that four ethanol-solubilised complexes with amine bisphenol, aminoalcohol bisphenol or salan ligands are equally or more effective than a previously used complex bis(maltolato)oxovanadium(V) in neuroblastoma cell lines. Moreover, we show that one of these complexes can be stably incorporated into cationic liposomes where it retains very good bioavailability, apparently low speciation and enhanced efficacy compared to ethanol delivery. This study provides the first proof-of-concept that stable, hydrophobic oxidovanadium complexes retain excellent cellular activity when delivered effectively to cancer cells with nanotechnology. This offers the improved prospect of applying oxidovanadium-based drugs in vivo with increased stability and reduced off-target toxicity.

A cellular target engagement assay for the characterization of SHP2 (PTPN11) phosphatase inhibitors

The nonreceptor protein-tyrosine phosphatase (PTP) SHP2 is encoded by the proto-oncogene PTPN11 and is a ubiquitously expressed key regulator of cell signaling, acting on a number of cellular processes and components, including the Ras/Raf/Erk, PI3K/Akt, and JAK/STAT pathways and immune checkpoint receptors. Aberrant SHP2 activity has been implicated in all phases of tumor initiation, progression, and metastasis. Gain-of-function PTPN11 mutations drive oncogenesis in several leukemias and cause developmental disorders with increased risk of malignancy such as Noonan syndrome. Until recently, small molecule-based targeting of SHP2 was hampered by the failure of orthosteric active-site inhibitors to achieve selectivity and potency within a useful therapeutic window. However, new SHP2 allosteric inhibitors with excellent potency and selectivity have sparked renewed interest in the selective targeting of SHP2 and other PTP family members. Crucially, drug discovery campaigns focusing on SHP2 would greatly benefit from the ability to validate the cellular target engagement of candidate inhibitors. Here, we report a cellular thermal shift assay that reliably detects target engagement of SHP2 inhibitors. Using this assay, based on the DiscoverX InCell Pulse enzyme complementation technology, we characterized the binding of several SHP2 allosteric inhibitors in intact cells. Moreover, we demonstrate the robustness and reliability of a 384-well miniaturized version of the assay for the screening of SHP2 inhibitors targeting either WT SHP2 or its oncogenic E76K variant. Finally, we provide an example of the assay's ability to identify and characterize novel compounds with specific cellular potency for either WT or mutant SHP2.

Comparative Genomics Reveals Shared Mutational Landscape in Canine Hemangiosarcoma and Human Angiosarcoma

Angiosarcoma is a highly aggressive cancer of blood vessel-forming cells with few effective treatment options and high patient mortality. It is both rare and heterogenous, making large, well-powered genomic studies nearly impossible. Dogs commonly suffer from a similar cancer, called hemangiosarcoma, with breeds like the golden retriever carrying heritable genetic factors that put them at high risk. If the clinical similarity of canine hemangiosarcoma and human angiosarcoma reflects shared genomic etiology, dogs could be a critically needed model for advancing angiosarcoma research. We assessed the genomic landscape of canine hemangiosarcoma via whole-exome sequencing (47 golden retriever hemangiosarcomas) and RNA sequencing (74 hemangiosarcomas from multiple breeds). Somatic coding mutations occurred most frequently in the tumor suppressor TP53 (59.6% of cases) as well as two genes in the PI3K pathway: the oncogene PIK3CA (29.8%) and its regulatory subunit PIK3R1 (8.5%). The predominant mutational signature was the age-associated deamination of cytosine to thymine. As reported in human angiosarcoma, CDKN2A/B was recurrently deleted and VEGFA, KDR, and KIT recurrently gained. We compared the canine data to human data recently released by The Angiosarcoma Project, and found many of the same genes and pathways significantly enriched for somatic mutations, particularly in breast and visceral angiosarcomas. Canine hemangiosarcoma closely models the genomic landscape of human angiosarcoma of the breast and viscera, and is a powerful tool for investigating the pathogenesis of this devastating disease. IMPLICATIONS: We characterize the genomic landscape of canine hemangiosarcoma and demonstrate its similarity to human angiosarcoma.

Protein tyrosine phosphatases: promising targets in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer. It is the fourth leading cause of cancer-related death and is associated with a very poor prognosis. KRAS driver mutations occur in approximately 95% of PDAC cases and cause the activation of several signaling pathways such as mitogen-activated protein kinase (MAPK) pathways. Regulation of these signaling pathways is orchestrated by feedback loops mediated by the balance between protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs), leading to activation or inhibition of its downstream targets. The human PTPome comprises 125 members, and these proteins are classified into three distinct families according to their structure. Since PTP activity description, it has become clear that they have both inhibitory and stimulatory effects on cancer-associated signaling processes and that deregulation of PTP function is closely associated with tumorigenesis. Several PTPs have displayed either tumor suppressor or oncogenic characteristics during the development and progression of PDAC. In this sense, PTPs have been presented as promising candidates for the treatment of human pancreatic cancer, and many PTP inhibitors have been developed since these proteins were first associated with cancer. Nevertheless, some challenges persist regarding the development of effective and safe methods to target these molecules and deliver these drugs. In this review, we discuss the role of PTPs in tumorigenesis as tumor suppressor and oncogenic proteins. We have focused on the differential expression of these proteins in PDAC, as well as their clinical implications and possible targeting for pharmacological inhibition in cancer therapy.

To reveal pharmacological targets and molecular mechanisms of curcumol against interstitial cystitis

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A PPI network showing protein interaction was produced.

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3 top biotargets of curcumol against IC were identified.

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Human IC sections showed increased PTK2, p-PTK2^Tyr397 expressions.

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Curcumol-treated IC mice benefited reduced PTK2, p-PTK2^Tyr397 expressions.

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PTK2 may be a potential biomarker for screening and treating IC.

This study was designed to reveal the predictive targets and biological mechanisms of curcumol against interstitial cystitis (IC). By use of available databases and bioinformatic assays, pathogenetic targets of IC and functional targets of curcumol were identified respectively. A network of functional protein-protein interaction (PPI) was produced before screening the main predictive targets, biological processes and signaling pathways of curcumol against IC. In bioinformatic findings, the data of ingenuity pathway analysis (IPA) delineated that curcumol exerted anti-IC benefits through regulating multipronged signaling pathways, including tyrosine protein kinase-2 (PTK2) pathway. Further, optimal 18 biotargets of curcumol against IC were harvested through differential expression analysis. And the predictive targets of receptor tyrosine-protein kinase erbB-2 (ERBB2), epidermal growth factor receptor (EGFR) and PTK2 were the most important molecules. In further validated experiments, PTK2 and phosphorylation PTK2 (p-PTK2) were representatively selected for testing by human and animal IC samples. As results, increased immunoreactive proteins of tumor necrosis factor alpha (TNF-α), PTK2 and p-PTK2^Tyr397 in human IC sections were observed, accompanied with altered urinary parameters. Interestingly, curcumol-treated IC mice showed that intracellular expressions of PTK2, p-PTK2^Tyr397 in bladder samples were reduced, accompanied with lowered blood inflammatory cytokines of interleukin 6 (IL-6), TNF-α. In conclusion, the current bioinformatic data and preliminary findings unravel that the predominant targets of curcumol against IC may be the potential biological markers for screening and treating IC, such as PTK2 molecule.

Aberrant promoter 2 methylation‑mediated downregulation of protein tyrosine phosphatase, non‑receptor type 6, is associated with progression of esophageal squamous cell carcinoma

The human protein tyrosine phosphatase, non‑receptor type 6 (PTPN6) gene is located on chromosome 12p13 and encodes an Mr 68,000 non‑receptor type protein‑tyrosine phosphatase. The PTPN6 gene has been considered as a candidate tumor suppressor in hematological and solid malignancies, and promoter methylation may be an epigenetic modification silencing its expression. However, the detailed role of PTPN6 and its promoter methylation status in the pathogenesis of esophageal squamous cell carcinoma (ESCC) has not been fully elucidated. The aim of the present study was to investigate PTPN6 expression in ESCC tissues and esophageal cancer cell lines, detect the effect of CpG hypermethylation on the activity of PTPN6, and additionally elucidate the role and prognostic significance of PTPN6 in ESCC tumorigenesis and progression. The expression of PTPN6 was identified to be significantly downregulated in esophageal cancer cell lines and ESCC tissues. Marked upregulation of PTPN6 was detected in 5‑aza‑2'‑deoxycytidine‑treated esophageal cancer cells, and frequent hypermethylation of the CpG sites within the P2 promoter (P2) was detected in ESCC tissues and esophageal cancer cell lines. The expression and methylation status of PTPN6 was associated with tumor node metastasis stage, pathological differentiation and lymph node metastasis in patients with ESCC. Aberrant hypermethylation of the P2 exhibited marked tumor specificity and was identified to be associated with the expression level of PTPN6. Downregulation and hypermethylation of PTPN6 were identified to be associated with poor ESCC patient survival. Furthermore, upregulation of PTPN6 inhibited the proliferation and invasion of esophageal cancer cells in vitro. The results of the present study suggest that PTPN6 may serve as a tumor suppressor in ESCC, and it may serve as a potential target for antitumor therapy.

High-resolution crystal structures of the D1 and D2 domains of protein tyrosine phosphatase epsilon for structure-based drug design

Here, new crystal structures are presented of the isolated membrane-proximal D1 and distal D2 domains of protein tyrosine phosphatase epsilon (PTPℇ), a protein tyrosine phosphatase that has been shown to play a positive role in the survival of human breast cancer cells. A triple mutant of the PTPℇ D2 domain (A455N/V457Y/E597D) was also constructed to reconstitute the residues of the PTPℇ D1 catalytic domain that are important for phosphatase activity, resulting in only a slight increase in the phosphatase activity compared with the native D2 protein. The structures reported here are of sufficient resolution for structure-based drug design, and a microarray-based assay for high-throughput screening to identify small-molecule inhibitors of the PTPℇ D1 domain is also described.

The impact of phosphatases on proliferative and survival signaling in cancer

The dynamic and stringent coordination of kinase and phosphatase activity controls a myriad of physiologic processes. Aberrations that disrupt the balance of this interplay represent the basis of numerous diseases. For a variety of reasons, early work in this area portrayed kinases as the dominant actors in these signaling events with phosphatases playing a secondary role. In oncology, these efforts led to breakthroughs that have dramatically altered the course of certain diseases and directed vast resources toward the development of additional kinase-targeted therapies. Yet, more recent scientific efforts have demonstrated a prominent and sometimes driving role for phosphatases across numerous malignancies. This maturation of the phosphatase field has brought with it the promise of further therapeutic advances in the field of oncology. In this review, we discuss the role of phosphatases in the regulation of cellular proliferation and survival signaling using the examples of the MAPK and PI3K/AKT pathways, c-Myc and the apoptosis machinery. Emphasis is placed on instances where these signaling networks are perturbed by dysregulation of specific phosphatases to favor growth and persistence of human cancer.

The roles of protein tyrosine phosphatases in bone-resorbing osteoclasts

Maintaining the proper balance between osteoblast-mediated production of bone and its degradation by osteoclasts is essential for health. Osteoclasts are giant phagocytic cells that are formed by fusion of monocyte-macrophage precursor cells; mature osteoclasts adhere to bone tightly and secrete protons and proteases that degrade its matrix. Phosphorylation of tyrosine residues in proteins, which is regulated by the biochemically-antagonistic activities of protein tyrosine kinases and protein tyrosine phosphatases (PTPs), is central in regulating the production of osteoclasts and their bone-resorbing activity. Here we review the roles of individual PTPs of the classical and dual-specificity sub-families that are known to support these processes (SHP2, cyt-PTPe, PTPRO, PTP-PEST, CD45) or to inhibit them (SHP1, PTEN, MKP1). Characterizing the functions of PTPs in osteoclasts is essential for complete molecular level understanding of bone resorption and for designing novel therapeutic approaches for treating bone disease.

Vanadium Compounds as PTP Inhibitors

Phosphotyrosine signaling is regulated by the opposing actions of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Here we discuss the potential of vanadium derivatives as PTP enzyme inhibitors and metallotherapeutics. We describe how vanadate in the V oxidized state is thought to inhibit PTPs, thus acting as a pan-inhibitor of this enzyme superfamily. We discuss recent developments in the biological and biochemical actions of more complex vanadium derivatives, including decavanadate and in particular the growing number of oxidovanadium compounds with organic ligands. Pre-clinical studies involving these compounds are discussed in the anti-diabetic and anti-cancer contexts. Although in many cases PTP inhibition has been implicated, it is also clear that many such compounds have further biochemical effects in cells. There also remain concerns surrounding off-target toxicities and long-term use of vanadium compounds in vivo in humans, hindering their progress through clinical trials. Despite these current misgivings, interest in these chemicals continues and many believe they could still have therapeutic potential. If so, we argue that this field would benefit from greater focus on improving the delivery and tissue targeting of vanadium compounds in order to minimize off-target toxicities. This may then harness their full therapeutic potential.