The two faces of PTP1B in cancer

PTPN1/2 inhibition promotes muscle stem cell differentiation in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a lethal disease caused by mutations in the DMD gene that encodes dystrophin. Dystrophin deficiency also impacts muscle stem cells (MuSCs), resulting in impaired asymmetric stem cell division and myogenic commitment. Using MuSCs from DMD patients and the DMD mouse model mdx, we found that PTPN1 phosphatase expression is up-regulated and STAT3 phosphorylation is concomitantly down-regulated in DMD MuSCs. To restore STAT3-mediated myogenic signaling, we examined the effect of K884, a novel PTPN1/2 inhibitor, on DMD MuSCs. Treatment with K884 enhanced STAT3 phosphorylation and promoted myogenic differentiation of DMD patient-derived MuSCs. In MuSCs from mdx mice, K884 treatment increased the number of asymmetric cell divisions, correlating with enhanced myogenic differentiation. Interestingly, the pro-myogenic effect of K884 is specific to human and murine DMD MuSCs and is absent from control MuSCs. Moreover, PTPN1/2 loss-of-function experiments indicate that the pro-myogenic impact of K884 is mediated mainly through PTPN1. We propose that PTPN1/2 inhibition may serve as a therapeutic strategy to restore the myogenic function of MuSCs in DMD.

Theoretical study on the design of allosteric inhibitors of diabetes associated protein PTP1B

The protein tyrosine phosphatase 1B (PTP1B) is a critical therapeutic target for type 2 diabetes mellitus (T2DM). Many PTP1B inhibitors have been reported, however, most of them lack high specificity and have adverse effects. Designing effective PTP1B inhibitors requires understanding the molecular mechanism of action between inhibitors and PTP1B. To this end, molecular dynamics (MD) simulations and molecular mechanics Poisson Boltzmann Surface Area (MM-PB/SA) methods were used to observe the binding patterns of compounds with similar pentacyclic triterpene parent ring structures but different inhibition abilities. Through structure and energy analysis, we found that the positions of cavities and substituents significantly affect combining capacity. Besides, we constructed a series of potential inhibitor molecules using LUDI and rational drug design methods. The ADMET module of Discovery Studio 2020 was used to predict the properties of these inhibitor molecules. Lastly, we obtained compounds with low toxicity and significant inhibitory activity. The study will contribute to the treatment of T2DM.

An expanded trove of fragment-bound structures for the allosteric enzyme PTP1B from computational reanalysis of large-scale crystallographic data

Due to their low binding affinities, detecting small-molecule fragments bound to protein structures from crystallographic datasets has been a challenge. Here, we report a trove of 65 new fragment hits for PTP1B, an "undruggable" therapeutic target enzyme for diabetes and cancer. These structures were obtained from computational analysis of data from a large crystallographic screen, demonstrating the power of this approach to elucidate many (∼50% more) "hidden" ligand-bound states of proteins. Our new structures include a fragment hit found in a novel binding site in PTP1B with a unique location relative to the active site, one that links adjacent allosteric sites, and, perhaps most strikingly, a fragment that induces long-range allosteric protein conformational responses. Altogether, our research highlights the utility of computational analysis of crystallographic data, makes publicly available dozens of new ligand-bound structures of a high-value drug target, and identifies novel aspects of ligandability and allostery in PTP1B.

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.

Recent Developments in the Role of Protein Tyrosine Phosphatase 1B (PTP1B) as a Regulator of Immune Cell Signalling in Health and Disease

Protein tyrosine phosphatase 1B (PTP1B) is a non-receptor tyrosine phosphatase best known for its role in regulating insulin and leptin signalling. Recently, knowledge on the role of PTP1B as a major regulator of multiple signalling pathways involved in cell growth, proliferation, viability and metabolism has expanded, and PTP1B is recognised as a therapeutic target in several human disorders, including diabetes, obesity, cardiovascular diseases and hematopoietic malignancies. The function of PTP1B in the immune system was largely overlooked until it was discovered that PTP1B negatively regulates the Janus kinase-a signal transducer and activator of the transcription (JAK/STAT) signalling pathway, which plays a significant role in modulating immune responses. PTP1B is now known to determine the magnitude of many signalling pathways that drive immune cell activation and function. As such, PTP1B inhibitors are being developed and tested in the context of inflammation and autoimmune diseases. Here, we provide an up-to-date summary of the molecular role of PTP1B in regulating immune cell function and how targeting its expression and/or activity has the potential to change the outcomes of immune-mediated and inflammatory disorders.

Differences in the expression of the phosphatase PTP-1B in patients with localized prostate cancer with and without adverse pathological features

Introduction

Patients with adverse pathological features (APF) at radical prostatectomy (RP) for prostate cancer (PC) are candidates for adjuvant treatment. Clinicians lack reliable markers to predict these APF preoperatively. Protein tyrosine phosphatase 1B (PTP-1B) is involved in migration and invasion of PC, and its expression could predict presence of APF. Our aim was to compare PTP-1B expression in patients with and without APF, and to explore PTP-1B expression as an independent prognostic factor.

Methods

Tissue microarrays (TMAs) were constructed using RP archival specimens for immunohistochemical staining of PTP-1B; expression was reported with a standardized score (0-9). We compared median PTP-1B score between cases with and without APF. We constructed two logistic regression models, one to identify the independence of PTP-1B score from biologically associated variables (metformin use and type 2 diabetes mellitus [T2DM]) and the second to seek independence of known risk factors (Gleason score and prostate specific antigen [PSA]).

Results

A total of 73 specimens were suitable for TMA construction. Forty-four (60%) patients had APF. The median PTP-1B score was higher in those with APF: 8 (5-9) vs 5 (3-8) (p=0.026). In the logistic regression model including T2DM and metformin use, the PTP-1B score maintained statistical significance (OR 1.21, 95% CI 1.01-1.45, p=0.037). In the model including PSA and Gleason score; the PTP-1B score showed no independence (OR 1.68, 95% CI 0.97-1.41, p=0.11). The area under the curve to predict APF for the PTP-1B score was 0.65 (95% CI 0.52-0.78, p=0.03), for PSA+Gleason 0.71 (95% CI 0.59-0.82, p=0.03), and for PSA+Gleason+PTP-1B score 0.73 (95% CI 0.61-0.84, p=0.001).

Discussion

Patients with APF after RP have a higher expression of PTP-1B than those without APF, even after adjusting for T2DM and metformin exposure. PTP-1B has a good accuracy for predicting APF but does not add to known prognostic factors.

Proteomic analysis of DEN and CCl4-induced hepatocellular carcinoma mouse model

Hepatocellular carcinoma (HCC) seriously threatens human health, mostly developed from liver fibrosis or cirrhosis. Since diethylnitrosamine (DEN) and carbon tetrachloride (CCl4)-induced HCC mouse model almost recapitulates the characteristic of HCC with fibrosis and inflammation, it is taken as an essential tool to investigate the pathogenesis of HCC. However, a comprehensive understanding of the protein expression profile of this model is little. In this study, we performed proteomic analysis of this model to elucidate its proteomic characteristics. Compared with normal liver tissues, 432 differentially expressed proteins (DEPs) were identified in tumor tissues, among which 365 were up-regulated and 67 were down-regulated. Through Gene Ontology (GO) analysis, Ingenuity Pathway Analysis (IPA), protein-protein interaction networks (PPI) analysis and Gene-set enrichment analysis (GSEA) analysis of DEPs, we identified two distinguishing features of DEN and CCl4-induced HCC mouse model in protein expression, the upregulation of actin cytoskeleton and branched-chain amino acids metabolic reprogramming. In addition, matching DEPs from the mouse model to homologous proteins in the human HCC cohort revealed that the DEN and CCl4-induced HCC mouse model was relatively similar to the subtype of HCC with poor prognosis. Finally, combining clinical information from the HCC cohort, we screened seven proteins with prognostic significance, SMAD2, PTPN1, PCNA, MTHFD1L, MBOAT7, FABP5, and AGRN. Overall, we provided proteomic data of the DEN and CCl4-induced HCC mouse model and highlighted the important proteins and pathways in it, contributing to the rational application of this model in HCC research.

Integrated use of ligand and structure-based virtual screening, molecular dynamics, free energy calculation and ADME prediction for the identification of potential PTP1B inhibitors

Protein tyrosine phosphatases (PTPs) are the group of enzymes that control both cellular activity and the dephosphorylation of tyrosine (Tyr)-phosphorylated proteins. Dysregulation of PTP1B has contributed to numerous diseases including Diabetes Mellitus, Alzheimer's disease, and obesity rendering PTP1B as a legitimate target for therapeutic applications. It is highly challenging to target this enzyme because of its highly conserved and positively charged active-site pocket motivating researchers to find novel lead compounds against it. The present work makes use of an integrated approach combining ligand-based and structure-based virtual screening to find hit compounds targeting PTP1B. Initially, pharmacophore modeling was performed to find common features like two hydrogen bond acceptors, an aromatic ring and one hydrogen bond donor from the potent PTP1B inhibitors. The dataset of compounds matching with the common pharmacophoric features was filtered to remove Pan-Assay Interference substructure and to match the Lipinski criteria. Then, compounds were further prioritized using molecular docking and top fifty compounds with good binding affinity were selected for absorption, distribution, metabolism, and excretion (ADME) predictions. The top five compounds with high solubility, absorption and permeability holding score of - 10 to - 9.3 kcal/mol along with Ertiprotafib were submitted to all-atom molecular dynamic (MD) studies. The MD studies and binding free energy calculations showed that compound M4, M5 and M8 were having better binding affinity for PTP1B enzyme with ∆Gtotal score of - 24.25, - 31.47 and - 33.81 kcal/mol respectively than other compounds indicating that compound M8 could be a suitable lead compound as PTP1B inhibitor.

An expanded view of ligandability in the allosteric enzyme PTP1B from computational reanalysis of large-scale crystallographic data

The recent advent of crystallographic small-molecule fragment screening presents the opportunity to obtain unprecedented numbers of ligand-bound protein crystal structures from a single high-throughput experiment, mapping ligandability across protein surfaces and identifying useful chemical footholds for structure-based drug design. However, due to the low binding affinities of most fragments, detecting bound fragments from crystallographic datasets has been a challenge. Here we report a trove of 65 new fragment hits across 59 new liganded crystal structures for PTP1B, an "undruggable" therapeutic target enzyme for diabetes and cancer. These structures were obtained from computational analysis of data from a large crystallographic screen, demonstrating the power of this approach to elucidate many (~50% more) "hidden" ligand-bound states of proteins. Our new structures include a fragment hit found in a novel binding site in PTP1B with a unique location relative to the active site, one that validates another new binding site recently identified by simulations, one that links adjacent allosteric sites, and, perhaps most strikingly, a fragment that induces long-range allosteric protein conformational responses via a previously unreported intramolecular conduit. Altogether, our research highlights the utility of computational analysis of crystallographic data, makes publicly available dozens of new ligand-bound structures of a high-value drug target, and identifies novel aspects of ligandability and allostery in PTP1B.

Cancer Pathways Targeted by Berberine: Role of microRNAs

Cancer is a complex and heterogeneous malignant disease. Due to its multifactorial nature, including progressive changes in genetic, epigenetic, transcript, and protein levels, conventional therapeutics fail to save cancer patients. Evidence indicates that dysregulation of microRNA (miRNA) expression plays a crucial role in tumorigenesis, metastasis, cell proliferation, differentiation, metabolism, and signaling pathways. Moreover, miRNAs can be used as diagnostic and prognostic markers and therapeutic targets in cancer. Berberine, a naturally occurring plant alkaloid, has a wide spectrum of biological activities in different types of cancers. Inhibition of cell proliferation, metastasis, migration, invasion, and angiogenesis, as well as induction of cell cycle arrest and apoptosis in cancer cells, is reported by berberine. Recent studies suggested that berberine regulates many oncogenic and tumor suppressor miRNAs implicated in different phases of cancer. This review discussed how berberine inhibits cancer growth and propagation and regulates miRNAs in cancer cells. And how berberine-mediated miRNA regulation changes the landscape of transcripts and proteins that promote or suppress cancer progression. Overall, the underlying molecular pathways altered by berberine and miRNA influencing the tumor pathophysiology will enhance our understanding to combat the malignancy.

A PTP1B-Cdk3 Signaling Axis Promotes Cell Cycle Progression of Human Glioblastoma Cells through an Rb-E2F Dependent Pathway

PTP1B plays a key role in developing different types of cancer. However, the molecular mechanism underlying this effect is unclear. To identify molecular targets of PTP1B that mediate its role in tumorigenesis, we undertook a SILAC-based phosphoproteomic approach, which allowed us to identify Cdk3 as a novel PTP1B substrate. Substrate trapping experiments and docking studies revealed stable interactions between the PTP1B catalytic domain and Cdk3. In addition, we observed that PTP1B dephosphorylates Cdk3 at tyrosine residue 15 in vitro and interacts with it in human glioblastoma cells. Next, we found that pharmacological inhibition of PTP1B or its depletion with siRNA leads to cell cycle arrest with diminished activity of Cdk3, hypophosphorylation of Rb, and the downregulation of E2F target genes Cdk1, Cyclin A, and Cyclin E1. Finally, we observed that the expression of a constitutively active Cdk3 mutant bypasses the requirement of PTP1B for cell cycle progression and expression of E2F target genes. These data delineate a novel signaling pathway from PTP1B to Cdk3 required for efficient cell cycle progression in an Rb-E2F dependent manner in human GB cells.

Schnurri-3 drives tumor growth and invasion in cancer cells expressing interleukin-13 receptor alpha 2

Interleukin 13 receptor alpha 2 (IL13Rα2) is a relevant therapeutic target in glioblastoma (GBM) and other tumors associated with tumor growth and invasion. In a previous study, we demonstrated that protein tyrosine phosphatase 1B (PTP1B) is a key mediator of the IL-13/IL13Rα2 signaling pathway. PTP1B regulates cancer cell invasion through Src activation. However, PTP1B/Src downstream signaling mechanisms that modulate the invasion process remain unclear. In the present research, we have characterized the PTP1B interactome and the PTP1B-associated phosphoproteome after IL-13 treatment, in different cellular contexts, using proteomic strategies. PTP1B was associated with proteins involved in signal transduction, vesicle transport, and with multiple proteins from the NF-κB signaling pathway, including Tenascin-C (TNC). PTP1B participated with NF-κB in TNC-mediated proliferation and invasion. Analysis of the phosphorylation patterns obtained after PTP1B activation with IL-13 showed increased phosphorylation of the transcription factor Schnurri-3 (SHN3), a reported competitor of NF-κB. SHN3 silencing caused a potent inhibition in cell invasion and proliferation, associated with a down-regulation of the Wnt/β-catenin pathway, an extensive decline of MMP9 expression and the subsequent inhibition of tumor growth and metastasis in mouse models. Regarding clinical value, high expression of SHN3 was associated with poor survival in GBM, showing a significant correlation with the classical and mesenchymal subtypes. In CRC, SHN3 expression showed a preferential association with the mesenchymal subtypes CMS4 and CRIS-B. Moreover, SHN3 expression strongly correlated with IL13Rα2 and MMP9-associated poor prognosis in different cancers. In conclusion, we have uncovered the participation of SNH3 in the IL-13/IL13Rα2/PTP1B pathway to promote tumor growth and invasion. These findings support a potential therapeutic value for SHN3.

PTPN1 is a prognostic biomarker related to cancer immunity and drug sensitivity: from pan-cancer analysis to validation in breast cancer

Background

Protein tyrosine phosphatase non-receptor type 1 (PTPN1), a member of the protein tyrosine phosphatase superfamily, has been identified as an oncogene and therapeutic target in various cancers. However, its precise role in determining the prognosis of human cancer and immunological responses remains elusive. This study investigated the relationship between PTPN1 expression and clinical outcomes, immune infiltration, and drug sensitivity in human cancers, which will improve understanding regarding its prognostic value and immunological role in pan-cancer.

Methods

The PTPN1 expression profile was obtained from The Cancer Genome Atlas and Cancer Cell Line Encyclopedia databases. Kaplan-Meier, univariate Cox regression, and time-dependent receiver operating characteristic curve analyses were utilized to clarify the relationship between PTPN1 expression and the prognosis of pan-cancer patients. The relationships between PTPN1 expression and the presence of tumor-infiltrated immune cells were analyzed using Estimation of Stromal and Immune cells in Malignant Tumor tissues using Expression data and Tumor Immune Estimation Resource. The cell counting kit-8 (CCK-8) assay was performed to examine the effects of PTPN1 level on the sensitivity of breast cancer cells to paclitaxel. Immunohistochemistry and immunoblotting were used to investigate the relationship between PTPN1 expression, immune cell infiltration, and immune checkpoint gene expression in human breast cancer tissues and a mouse xenograft model.

Results

The pan-cancer analysis revealed that PTPN1 was frequently up-regulated in various cancers. High PTPN1 expression was associated with poor prognosis in most cancers. Furthermore, PTPN1 expression correlated highly with the presence of tumor-infiltrating immune cells and the expression of immune checkpoint pathway marker genes in different cancers. Furthermore, PTPN1 significantly predicted the prognosis for patients undergoing immunotherapy. The results of the CCK-8 viability assay revealed that PTPN1 knockdown increased the sensitivity of MDA-MB-231 and MCF-7 cells to paclitaxel. Finally, our results demonstrated that PTPN1 was associated with immune infiltration and immune checkpoint gene expression in breast cancer.

Conclusion

PTPN1 was overexpressed in multiple cancer types and correlated with the clinical outcome and tumor immunity, suggesting it could be a valuable potential prognostic and immunological biomarker for pan-cancer.

Analysis of neutral mutational drift in an allosteric enzyme

Neutral mutational drift is an important source of biological diversity that remains underexploited in fundamental studies of protein biophysics. This study uses a synthetic transcriptional circuit to study neutral drift in protein tyrosine phosphatase 1B (PTP1B), a mammalian signaling enzyme for which conformational changes are rate limiting. Kinetic assays of purified mutants indicate that catalytic activity, rather than thermodynamic stability, guides enrichment under neutral drift, where neutral or mildly activating mutations can mitigate the effects of deleterious ones. In general, mutants show a moderate activity-stability tradeoff, an indication that minor improvements in the activity of PTP1B do not require concomitant losses in its stability. Multiplexed sequencing of large mutant pools suggests that substitutions at allosterically influential sites are purged under biological selection, which enriches for mutations located outside of the active site. Findings indicate that the positional dependence of neutral mutations within drifting populations can reveal the presence of allosteric networks and illustrate an approach for using synthetic transcriptional systems to explore these mutations in regulatory enzymes.

The Potential Role of Epigallocatechin-3-Gallate (EGCG) in Breast Cancer Treatment

Breast cancer is one of the most diagnosed cancers worldwide, with an incidence of 47.8%. Its treatment includes surgery, radiotherapy, chemotherapy, and antibodies giving a mortality of 13.6%. Breast tumor development is driven by a variety of signaling pathways with high heterogeneity of surface receptors, which makes treatment difficult. Epigallocatechin-3-gallate (EGCG) is a natural polyphenol isolated as the main component in green tea; it has shown multiple beneficial effects in breast cancer, controlling proliferation, invasion, apoptosis, inflammation, and demethylation of DNA. These properties were proved in vitro and in vivo together with synergistic effects in combination with traditional chemotherapy, increasing the effectiveness of the treatment. This review focuses on the effects of EGCG on the functional capabilities acquired by breast tumor cells during its multistep development, the molecular and signal pathways involved, the synergistic effects in combination with current drugs, and how nanomaterials can improve its bioavailability on breast cancer treatment.

Can Allostery Be a Key Strategy for Targeting PTP1B in Drug Discovery? A Lesson from Trodusquemine

Protein tyrosine phosphatase 1B (PTP1B) is an enzyme crucially implicated in aberrations of various signaling pathways that underlie the development of different human pathologies, such as obesity, diabetes, cancer, and neurodegenerative disorders. Its inhibition can prevent these pathogenetic events, thus providing a useful tool for the discovery of novel therapeutic agents. The search for allosteric PTP1B inhibitors can represent a successful strategy to identify drug-like candidates by offering the opportunity to overcome some issues related to catalytic site-directed inhibitors, which have so far hampered the development of drugs targeting this enzyme. In this context, trodusquemine (MSI-1436), a natural aminosterol that acts as a non-competitive PTP1B inhibitor, appears to be a milestone. Initially discovered as a broad-spectrum antimicrobial agent, trodusquemine exhibited a variety of unexpected properties, ranging from antidiabetic and anti-obesity activities to effects useful to counteract cancer and neurodegeneration, which prompted its evaluation in several preclinical and clinical studies. In this review article, we provide an overview of the main findings regarding the activities and therapeutic potential of trodusquemine and their correlation with PTP1B inhibition. We also included some aminosterol analogues and related structure-activity relationships that could be useful for further studies aimed at the discovery of new allosteric PTP1B inhibitors.

Effects of dietary wild bitter melon (Momordica charantia var. abbreviate Ser.) extract on glucose and lipid metabolism in HFD/STZ-induced type 2 diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Plant-based extracts to interfere with the onset of diabetes may be a promising approach towards type 2 diabetes mellitus (T2DM). Bitter gourd (Momordica charantia L.) is popularly consumed as an edible and medicinal resource with hypoglycemic effect in China. Wild bitter gourd (Momordica Charantia var. abbreviata Ser.) is a variant of bitter gourd, but there are relatively few studies on it.

AIM OF THE STUDY

The purpose of the experiment is to first screen out the most effective extraction part of Momordica charantia L. and Momordica Charantia var. abbreviata Ser. through the hypoglycemic activity experiment in vitro, and by using a high-fat and high-sugar diet with STZ-induced diabetic rat model in vivo to explore the possible mechanism of action against diabetes.

MATERIALS AND METHODS

This study first performed α-glucosidase, PTP1B and lipase activities inhibition experiments on the alcohol and water extracts of Momordica charantia L. and Momordica Charantia var. abbreviata Ser. Sprague Dawley rats were either given normal feed or a high sugar and fat diet for four weeks, followed STZ (25 mg/kg, via i. p.) was given. Rats with fasting blood glucose ≥11.1 mmol/l after one week were deemed to be diabetic, treatments were administered for four weeks, and then blood samples were used to evaluate hematological and biochemical indicators, and liver was removed for post-analysis. The expression levels of p-AMPK, AMPK, p-PI3K, PI3K, p-AKT, AKT, p-GSK3β, GSK3β, p-IRS-1, IRS-1, GLUT2 were determined by Western blot. At the same time, the chemical components was identified by liquid-mass spectrometry.

RESULTS

Data showed that the ethanol extract of wild bitter gourd (WBGE) had the best ability to regulate glucose and lipid metabolism in vitro. Therefore, we further investigated the antidiabetic effects of oral consumption of WBGE on high-fat diet (HFD) and streptozotocin (STZ)-induced T2DM in SD rats. WBGE effectively reduced blood glucose and lipid levels, alleviated glucose intolerance and insulin resistant. Moreover, WBGE consumption could also inhibited oxidant responses and inflammatory damage. Mechanism studies have shown that WBGE may act by regulating AMPK/PI3K signaling pathway. On the other hand, the content of total phenol, total flavonoids, total saponins and total polysaccharide were measured by UV, 27 compounds were identified by LC-MS.

CONCLUSIONS

These studies explored the role and mechanism of WBGE in regulating glucose and lipid metabolism, and may support the utilization and further investigation of wild bitter gourd as a dietary intervention strategy to prevent diabetes and related metabolic abnormalities.

Isosteviol derivatives as protein tyrosine Phosphatase-1B inhibitors: Synthesis, biological evaluation and molecular docking

Protein tyrosine phosphatase (PTP1B) antagonizes insulin signaling and acts as a potential therapeutic target for insulin resistance associated with obesity and type II diabetes. In this work, a series of isosteviol derivatives 1-28 was synthesized and the inhibitory activity on PTP1B was evaluated by double antibody sandwich ELISA (DAS-ELISA) in vitro. Most isosteviol derivatives showed moderate PTP1B inhibitory activities. Among them, derivatives 10, 13, 24, 27 showed remarkable bioactivities with IC₅₀ values ranging from 0.24 to 0.40 µM. Particularly, derivative 24 exhibited the best inhibitory activity against PTP1B (IC₅₀ = 0.24 µM) in vitro; moreover, it showed 7-fold selectivity to PTP1B over T-cell protein tyrosine phosphatase (TCPTP) and 14-fold selectivity to PTP1B over cell division cycle 25 homolog B (CDC25B). Molecular docking studies demonstrated the hydrogen bond interaction between 24 and LYS-116 residue in PTP1B might be essential for the inhibitory activity. The results suggested that derivative 24 has great potential to be employed as drug candidate for the treatment of obesity and type II diabetes.

Status of research on natural protein tyrosine phosphatase 1B inhibitors as potential antidiabetic agents: Update

Protein tyrosine phosphatase 1B (PTP1B) is a crucial therapeutic target for multiple human diseases comprising type 2 diabetes (T2DM) and obesity because it is a seminal part of a negative regulator in both insulin and leptin signaling pathways. PTP1B inhibitors increase insulin receptor sensitivity and have the ability to cure insulin resistance-related diseases. However, the few PTP1B inhibitors that entered the clinic (Ertiprotafib, ISIS-113715, Trodusquemine, and JTT-551) were discontinued due to side effects or low selectivity. Molecules with broad chemical diversity extracted from natural products have been reported to be potent PTP1B inhibitors with few side effects. This article summarizes the recent PTP1B inhibitors extracted from natural products, clarifying the current research progress, and providing new options for designing new and effective PTP1B inhibitors.

The role of PTP1B (PTPN1) in the prognosis of solid tumors: A meta-analysis

BACKGROUND

Protein tyrosine phosphatase 1B (PTP1B) played different role in different solid tumors, and was associated with the prognosis of solid tumors. However, the roles existed controversy. This meta-analysis was performed to determine whether PTP1B was relevant to the prognosis of solid tumors.

MATERIALS AND METHODS

A literature search in Web of Science, Embase and PubMed databases were performed up to November 1, 2021. A meta-analysis dealed with PTP1B assessment in solid tumors, providing clinical stages and survival comparisons according to the PTP1B status.

RESULTS

High PTP1B expression was significantly associated with later clinical stage of solid tumors (Odds ratio [OR] 2.25, 95% confidence interval [CI]: 1.71-2.98, P < .001). For solid tumors, the hazard ratio (HR) for disease free survival (DFS) detrimental with high PTP1B expression compared with low PTP1B expression was 1.07 (95%CI: 0.67-1.73, P = .77) with the obvious heterogeneity (P = .03, I2 = 66%). The HR of overall survival (OS) for solid tumors with high PTP1B expression versus low PTP1B expression was 1.26 (95%CI: 1.03-1.55, P = .03) with significant publication bias (t = 3.28, P = .005). Subgroup analysis indicated that the high expression of PTP1B was remarkably correlated with poor OS in colorectal carcinoma, only (HR = 1.43; 95%CI: 1.18-1.74; P = .003).

CONCLUSIONS

High PTP1B expression is significantly associated with later clinical stage of solid tumors. The high expression of PTP1B is remarkably correlated with poor OS in colorectal carcinoma, only. There is no definite conclusion that PTP1B was, or not associated with DFS and OS of solid tumors because of heterogeneity and publication bias. Whether PTP1B can be used as a biomarker for predicting the prognosis of solid tumors needs further study.

Developing New Treatment Options for Castration-Resistant Prostate Cancer and Recurrent Disease

Prostate cancer (PCa) is a major diagnosed cancer among men globally, and about 20% of patients develop metastatic prostate cancer (mPCa) in the initial diagnosis. PCa is a typical androgen-dependent disease; thus, hormonal therapy is commonly used as a standard care for mPCa by inhibiting androgen receptor (AR) activities, or androgen metabolism. Inevitably, almost all PCa will acquire resistance and become castration-resistant PCa (CRPC) that is associated with AR gene mutations or amplification, the presence of AR variants, loss of AR expression toward neuroendocrine phenotype, or other hormonal receptors. Treating CRPC poses a great challenge to clinicians. Research efforts in the last decade have come up with several new anti-androgen agents to prolong overall survival of CRPC patients. In addition, many potential targeting agents have been at the stage of being able to translate many preclinical discoveries into clinical practices. At this juncture, it is important to highlight the emerging strategies including small-molecule inhibitors to AR variants, DNA repair enzymes, cell survival pathway, neuroendocrine differentiation pathway, radiotherapy, CRPC-specific theranostics and immune therapy that are underway or have recently been completed.

Interplay between EGFR, E-cadherin, and PTP1B in epidermal homeostasis

Maintaining epithelial homeostasis is crucial to allow embryo development but also the protective barrier which is ensured by the epidermis. This homeostasis is regulated through the expression of several molecules among which EGFR and E-cadherin which are of major importance. Indeed, defects in the regulation of these proteins lead to abnormalities in cell adhesion, proliferation, differentiation, and migration. Hence, regulation of these two proteins is of the utmost importance as they are involved in numerous skin pathologies and cancers. In the last decades it has been described several pathways of regulation of these two proteins and notably several mechanisms of cross-regulation between these partners. In this review, we aimed to describe the current understanding of the regulation of EGFR and interactions between EGFR and E-cadherin and, in particular, the implication of these cross-regulations in epithelium homeostasis. We pay particular attention to PTP1B, a phosphatase involved in the regulation of EGFR.

Computational Methods in Cooperation with Experimental Approaches to Design Protein Tyrosine Phosphatase 1B Inhibitors in Type 2 Diabetes Drug Design: A Review of the Achievements of This Century

Protein tyrosine phosphatase 1B (PTP1B) dephosphorylates phosphotyrosine residues and is an important regulator of several signaling pathways, such as insulin, leptin, and the ErbB signaling network, among others. Therefore, this enzyme is considered an attractive target to design new drugs against type 2 diabetes, obesity, and cancer. To date, a wide variety of PTP1B inhibitors that have been developed by experimental and computational approaches. In this review, we summarize the achievements with respect to PTP1B inhibitors discovered by applying computer-assisted drug design methodologies (virtual screening, molecular docking, pharmacophore modeling, and quantitative structure–activity relationships (QSAR)) as the principal strategy, in cooperation with experimental approaches, covering articles published from the beginning of the century until the time this review was submitted, with a focus on studies conducted with the aim of discovering new drugs against type 2 diabetes. This review encourages the use of computational techniques and includes helpful information that increases the knowledge generated to date about PTP1B inhibition, with a positive impact on the route toward obtaining a new drug against type 2 diabetes with PTP1B as a molecular target.

Synthesis, In Vitro, and Computational Studies of PTP1B Phosphatase Inhibitors Based on Oxovanadium(IV) and Dioxovanadium(V) Complexes

One of the main goals of recent bioinorganic chemistry studies has been to design and synthesize novel substances to treat human diseases. The promising compounds are metal-based and metal ion binding components such as vanadium-based compounds. The potential anticancer action of vanadium-based compounds is one of area of investigation in this field. In this study, we present five oxovanadium(IV) and dioxovanadium(V) complexes as potential PTP1B inhibitors with anticancer activity against the MCF-7 breast cancer cell line, the triple negative MDA-MB-231 breast cancer cell line, and the human keratinocyte HaCaT cell line. We observed that all tested compounds were effective inhibitors of PTP1B, which correlates with anticancer activity. [VO(dipic)(dmbipy)]·2 H2O (Compound 4) and [VOO(dipic)](2-phepyH)·H2O (Compound 5) possessed the greatest inhibitory effect, with IC50 185.4 ± 9.8 and 167.2 ± 8.0 nM, respectively. To obtain a better understanding of the relationship between the structure of the examined compounds and their activity, we performed a computer simulation of their binding inside the active site of PTP1B. We observed a stronger binding of complexes containing dipicolinic acid with PTP1B. Based on our simulations, we suggested that the studied complexes exert their activity by stabilizing the WPD-loop in an open position and limiting access to the P-loop.

Human Protein Tyrosine Phosphatase 1B (PTP1B): From Structure to Clinical Inhibitor Perspectives

Phosphorylation is an essential process in biological events and is considered critical for biological functions. In tissues, protein phosphorylation mainly occurs on tyrosine (Tyr), serine (Ser) and threonine (Thr) residues. The balance between phosphorylation and dephosphorylation is under the control of two super enzyme families, protein kinases (PKs) and protein phosphatases (PPs), respectively. Although there are many selective and effective drugs targeting phosphokinases, developing drugs targeting phosphatases is challenging. PTP1B, one of the most central protein tyrosine phosphatases (PTPs), is a key player in several human diseases and disorders, such as diabetes, obesity, and hematopoietic malignancies, through modulation of different signaling pathways. However, due to high conservation among PTPs, most PTP1B inhibitors lack specificity, raising the need to develop new strategies targeting this enzyme. In this mini-review, we summarize three classes of PTP1B inhibitors with different mechanisms: (1) targeting multiple aryl-phosphorylation sites including the catalytic site of PTP1B; (2) targeting allosteric sites of PTP1B; (3) targeting specific mRNA sequence of PTP1B. All three types of PTP1B inhibitors present good specificity over other PTPs and are promising for the development of efficient small molecules targeting this enzyme.

Licoflavone A Suppresses Gastric Cancer Growth and Metastasis by Blocking the VEGFR-2 Signaling Pathway

Objectives

Licoflavone A (LA) is a natural flavonoid compound derived from the root of Glycyrrhiza. This study investigated the antitumor effect and underlying molecular mechanisms of LA against gastric cancer (GC) in vitro and in vivo.

Materials and Methods

A CCK8 assay was used to measure the antiproliferative activity of LA in human GC SGC-7901, MKN-45, MGC-803 cells, and human GES-1 cells. Target prediction and protein-protein interaction (PPI) analysis were used to identify the potential molecular targets of LA. The binding pattern of LA to VEGFR-2 was analyzed by molecular docking and molecular dynamic (MD). The affinity of LA for VEGFR-2 was determined by microscale thermophoresis (MST). The protein tyrosine kinase activity of VEGFR-2 in the presence of LA was determined by an enzyme activity test. The effect of LA on the proliferation of VEGF-stimulated MKN-45 cells was measured with CCK8 assays, clone formation assays, and 3D microsphere models. Hoechst 33342 staining, FCM, MMP, and WB assays were used to investigate the ability of LA to block cell cycle and promote apoptosis of VEGF-stimulated MKN-45 cells. Transwell matrix assays were used to measure migration and invasion, and WB assays were used to measure EMT.

Results

LA inhibited the proliferation of SGC-7901, MKN-45, and MGC-803 cells and VEGF-stimulated MKN-45 cells. VEGFR-2 was identified as the target of LA. LA could also block cell cycle, induce apoptosis, and inhibit migration, invasion, and EMT of VEGF-stimulated MKN-45 cells. Functional analyses further revealed that the cytotoxic effect of LA on VEGF-stimulated MKN-45 cells potentially involved the PI3K/AKT and MEK/ERK signaling pathways.

Conclusions

This study demonstrates that LA has anti-GC potency in vitro and in vivo. LA affects the proliferation, cycle, apoptosis, migration, invasion, and EMT by targeting VEGFR-2 and blocks the PI3K/AKT and MEK/ERK signaling pathways in VEGF-stimulated MKN-45 cells.

Research progress on antineoplastic, antibacterial, and anti-inflammatory activities of seven-membered heterocyclic derivatives

Abstract:

Seven-membered heterocyclic compounds are important drug scaffolds, because of their unique chemical structures. They widely exist in natural products and show a variety of biological activities. They have commonly been used in central nervous system drugs in the past 30 years. In the past decade, there are many studies on the activities of antitumor, antibacterial, etc. Herein, we summarize the research advances in different kinds of seven-membered heterocyclic compounds containing nitrogen, oxygen, and sulfur heteroatoms with antitumor, antisepsis, and anti-inflammation activities in the past ten years, which is expected to be beneficial to the development and design of novel drugs for the corresponding indications.

Samarium(ii) iodide-mediated reactions applied to natural product total synthesis

Natural product synthesis remains a field in which new synthetic methods and reagents are continually being evaluated. Due to the demanding structures and complex functionality of many natural products, only powerful and selective methods and reagents will be highlighted in this proceeding. Since its introduction by Henri Kagan, samarium(ii) iodide (SmI2, Kagan's reagent) has found increasing use in chemical synthesis. Over the years, many reviews have been published on the application of SmI2 in numerous reductive coupling procedures as well as in natural product total synthesis. This review highlights recent advances in SmI2-mediated synthetic strategies, as applied in the total synthesis of natural products since 2004.

Myeloid-Specific PTP1B Deficiency Attenuates Inflammation-Induced and Ovariectomy-Induced Bone Loss in Mice by Inhibiting Osteoclastogenesis

The differentiation and activity of bone-resorbing osteoclasts are tightly regulated to maintain the homeostasis of healthy bones. In this study, the role of protein tyrosine phosphatase 1B (PTP1B) during osteoclastogenesis was studied in myeloid-specific Ptpn1-deficient (conditional knockout [cKO]) mice. The mRNA and protein expression of PTP1B increased during the formation of mature osteoclasts from mouse bone macrophages on stimulation with macrophage-colony stimulating factor (M-CSF) and receptor activator of nuclear factor κB ligand (RANKL). The Ptpn1 cKO mice exhibited increased femoral trabecular bone volume with a decreased number and activity of osteoclasts compared with control mice. The in vitro culture of osteoclast precursors corroborated the inhibition of osteoclastogenesis in cKO cells compared with control, with concomitantly decreased RANKL-dependent proliferation, lower osteoclast marker gene expression, reduced nuclear expression of nuclear factor of activated T cells cytoplasmic 1 (NFATc1), diminished intracellular Ca²⁺ oscillations, and increased phosphorylation of proto-oncogene tyrosine-protein kinase Src on inhibitory tyrosine residue. In a ligature-induced periodontitis model, Ptpn1 cKO mice exhibited attenuated osteoclastogenesis and alveolar bone loss following the induction of inflammation. The Ptpn1-deficient mice were similarly protected from ovariectomy-induced bone loss compared with control mice. These results provide a novel regulatory role of PTP1B in osteoclastogenesis and suggest a potential as a therapeutic target for bone-lytic diseases. © 2021 American Society for Bone and Mineral Research (ASBMR).

Protein tyrosine phosphatase 1B regulates fibroblasts proliferation, motility and extracellular matrix synthesis via the MAPK/ERK signalling pathway in keloid

Keloid is a fibroproliferative disorder resulting from trauma, characterized by abnormal activation of keloid fibroblasts and excessive deposition of extracellular matrix (ECM). It affects life quality of patients and lacks of effective therapeutic targets. Protein tyrosine phosphatase 1B (PTP1B) belongs to the protein tyrosine phosphatases and participates in many cellular processes such as metabolism, proliferation and motility. It has been reported that PTP1B negatively regulated diabetic wound healing and tumor progression. However, its effects in keloid remain unclear. Here, we aimed to evaluate the effects of PTP1B on keloid fibroblasts which play essential roles in keloids pathogenesis. Our results revealed that PTP1B expression was decreased both in keloid tissues and in keloid fibroblasts compared to healthy controls. Keloid fibroblasts (KFs) showed higher cell proliferation, motility, ECM production and ERK activity than normal fibroblasts (NFs). Overexpression of PTP1B in KFs and NFs inhibited cell proliferation, motility, ECM synthesis and the MAPK/ERK signalling pathway while knockdown of PTP1B showed converse effects. The rescue experiments with ERK inhibitor further verified that MAPK/ERK signalling pathway involved in PTP1B regulatory network. Taken together, our findings indicated that overexpression of PTP1B suppressed keloid fibroblasts bio-behaviours and promoted their phenotype switch to normal cells via inhibiting the MAPK/ERK signalling pathway, suggesting it may be a potential anti-keloid therapy.

Modulation of Intracellular Copper Levels as the Mechanism of Action of Anticancer Copper Complexes: Clinical Relevance

Copper (Cu) is a vital element required for cellular growth and development; however, even slight changes in its homeostasis might lead to severe toxicity and deleterious medical conditions. Cancer patients are typically associated with higher Cu content in serum and tumor tissues, indicating increased demand of cancer cells for this micronutrient. Cu is known to readily cycle between the +1 and +2 oxidation state in biological systems. The mechanism of action of Cu complexes is typically based on their redox activity and induction of reactive oxygen species (ROS), leading to deadly oxidative stress. However, there are a number of other biomolecular mechanisms beyond ROS generation that contribute to the activity of anticancer Cu drug candidates. In this review, we discuss how interfering with intracellular Cu balance via either diet modification or addition of inorganic Cu supplements or Cu-modulating compounds affects tumor development, progression, and sensitivity to treatment modalities. We aim to provide the rationale for the use of Cu-depleting and Cu-overloading conditions to generate the best possible patient outcome with minimal toxicity. We also discuss the advantages of the use of pre-formed Cu complexes, such as Cu-(bis)thiosemicarbazones or Cu-N-heterocyclic thiosemicarbazones, in comparison with the in situ formed Cu complexes with metal-binding ligands. In this review, we summarize available clinical and mechanistic data on clinically relevant anticancer drug candidates, including Cu supplements, Cu chelators, Cu ionophores, and Cu complexes.

Indole- and Pyrazole-Glycyrrhetinic Acid Derivatives as PTP1B Inhibitors: Synthesis, In Vitro and In Silico Studies

Regulating insulin and leptin levels using a protein tyrosine phosphatase 1B (PTP1B) inhibitor is an attractive strategy to treat diabetes and obesity. Glycyrrhetinic acid (GA), a triterpenoid, may weakly inhibit this enzyme. Nonetheless, semisynthetic derivatives of GA have not been developed as PTP1B inhibitors to date. Herein we describe the synthesis and evaluation of two series of indole- and N-phenylpyrazole-GA derivatives (4a-f and 5a-f). We measured their inhibitory activity and enzyme kinetics against PTP1B using p-nitrophenylphosphate (pNPP) assay. GA derivatives bearing substituted indoles or N-phenylpyrazoles fused to their A-ring showed a 50% inhibitory concentration for PTP1B in a range from 2.5 to 10.1 µM. The trifluoromethyl derivative of indole-GA (4f) exhibited non-competitive inhibition of PTP1B as well as higher potency (IC₅₀ = 2.5 µM) than that of positive controls ursolic acid (IC₅₀ = 5.6 µM), claramine (IC₅₀ = 13.7 µM) and suramin (IC₅₀ = 4.1 µM). Finally, docking and molecular dynamics simulations provided the theoretical basis for the favorable activity of the designed compounds.

Gastric Cancer: Identification of microRNAs Inhibiting Druggable Targets and Mediating Efficacy in Preclinical In Vivo Models

In addition to chemotherapy, targeted therapies have been approved for treatment of locally advanced and metastatic gastric cancer. The therapeutic benefit is significant but more durable responses and improvement of survival should be achieved. Therefore, the identification of new targets and new approaches for clinical treatment are of paramount importance. In this review, we searched the literature for down-regulated microRNAs which interfere with druggable targets and exhibit efficacy in preclinical in vivo efficacy models. As druggable targets, we selected transmembrane receptors, secreted factors and enzymes. We identified 38 microRNAs corresponding to the criteria as outlined. A total of 13 miRs target transmembrane receptors, nine inhibit secreted proteins and 16 attenuate enzymes. These microRNAs are targets for reconstitution therapy of gastric cancer. Further target validation experiments are mandatory for all of the identified microRNAs.

The PTP1B mutant PTP1B∆2-4 is a positive regulator of the JAK/STAT signalling pathway in Hodgkin lymphoma

The neoplastic Hodgkin/Reed-Sternberg (HRS) cells of classical Hodgkin lymphoma (cHL) depend on chronic activation of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signalling pathways to maintain survival and proliferation. Accumulating reports highlight the importance of the inactivation or reduced expression of negative JAK/STAT regulators such as the protein-tyrosine phosphatase 1B (PTP1B/PTPN1) in this process. Various PTPN1 mRNA variants as well as truncated PTP1B proteins were identified in cHL cell lines and primary cHL tumour samples. These PTPN1 mRNA variants lack either one or several exon sequences and therefore render these PTP1B variants catalytically inactive. Here, we show that one of these mutants, PTP1B∆2-4, is not only a catalytically inactive variant, but also augmented the IL-4-induced JAK/STAT activity similar to the recently reported PTP1B∆6 splice variant. Moreover, while PTP1B∆6 diminished the activity and protein levels of PTP1BWT, PTP1BWT remained unaffected by PTP1B∆2-4, arguing for different molecular mechanisms of JAK/STAT modulation by PTP1B∆6 and PTP1B∆2-4. Collectively, these data indicate that PTPN1 variants missing one or more exon sequences originated either from alternative splicing or from gene mutation, create PTP1B gain-of-function variants with oncogenic potential by augmenting JAK/STAT signalling in cHL.

Pharmacological Inhibition of miR-130 Family Suppresses Bladder Tumor Growth by Targeting Various Oncogenic Pathways via PTPN1

Previously, we have revealed that the miR-130 family (miR-130b, miR-301a, and miR-301b) functions as an oncomiR in bladder cancer. The pharmacological inhibition of the miR-130 family molecules by the seed-targeting strategy with an 8-mer tiny locked nucleic acid (LNA) inhibits the growth, migration, and invasion of bladder cancer cells by repressing stress fiber formation. Here, we searched for a functionally advanced target sequence with LNA for the miR-130 family with low cytotoxicity and found LNA #9 (A(L)^i^i^A(L)^T(L)^T(L)^G(L)^5(L)^A(L)^5(L)^T(L)^G) as a candidate LNA. LNA #9 inhibited cell growth in vitro and in an in vivo orthotopic bladder cancer model. Proteome-wide tyrosine phosphorylation analysis suggested that the miR-130 family upregulates a wide range of receptor tyrosine kinases (RTKs) signaling via the expression of phosphorylated Src (pSrc^Tyr416). SILAC-based proteome analysis and a luciferase assay identified protein tyrosine phosphatase non-receptor type 1 (PTPN1), which is implicated as a negative regulator of multiple signaling pathways downstream of RTKs as a target gene of the miR-130 family. The miR-130-targeted LNA increased and decreased PTPN1 and pSrc^Tyr416 expressions, respectively. PTPN1 knockdown led to increased tumor properties (cell growth, invasion, and migration) and increased pSrc^Tyr416 expression in bladder cancer cells, suggesting that the miR-130 family upregulates multiple RTK signaling by targeting PTPN1 and subsequent Src activation in bladder cancer. Thus, our newly designed miR-130 family targeting LNA could be a promising nucleic acid therapeutic agent for bladder cancer.

PD-L1 tumor-intrinsic signaling and its therapeutic implication in triple-negative breast cancer

Although the immune checkpoint role of programmed death ligand 1 (PD-L1) has been established and targeted in cancer immunotherapy, the tumor-intrinsic role of PD-L1 is less appreciated in tumor biology and therapeutics development, partly because of the incomplete mechanistic understanding. Here we demonstrate a potentially novel mechanism by which PD-L1 promotes the epithelial-mesenchymal transition (EMT) in triple-negative breast cancer (TNBC) cells by suppressing the destruction of the EMT transcription factor Snail. PD-L1 directly binds to and inhibits the tyrosine phosphatase PTP1B, thus preserving p38-MAPK activity that phosphorylates and inhibits glycogen synthase kinase 3β (GSK3β). Via this mechanism, PD-L1 prevents the GSK3β-mediated phosphorylation, ubiquitination, and degradation of Snail and consequently promotes the EMT and metastatic potential of TNBC. Significantly, PD-L1 antibodies that confine the tumor-intrinsic PD-L1/Snail pathway restricted TNBC progression in immunodeficient mice. More importantly, targeting both tumor-intrinsic and tumor-extrinsic functions of PD-L1 showed strong synergistic tumor suppression effect in an immunocompetent TNBC mouse model. Our findings support that PD-L1 intrinsically facilitates TNBC progression by promoting the EMT, and this potentially novel PD-L1 signaling pathway could be targeted for better clinical management of PD-L1–overexpressing TNBCs.

Endoplasmic Reticulum-Plasma Membrane Contact Sites: Regulators, Mechanisms, and Physiological Functions

The endoplasmic reticulum (ER) forms direct membrane contact sites with the plasma membrane (PM) in eukaryotic cells. These ER-PM contact sites play essential roles in lipid homeostasis, ion dynamics, and cell signaling, which are carried out by protein-protein or protein-lipid interactions. Distinct tethering factors dynamically control the architecture of ER-PM junctions in response to intracellular signals or external stimuli. The physiological roles of ER-PM contact sites are dependent on a variety of regulators that individually or cooperatively perform functions in diverse cellular processes. This review focuses on proteins functioning at ER-PM contact sites and highlights the recent progress in their mechanisms and physiological roles.

Polyhydroxy p-Terphenyls from a Mangrove Endophytic Fungus Aspergillus candidus LDJ-5

Six undescribed polyhydroxy p-terphenyls, namely asperterphenyllins A–F, were isolated from an endophytic fungus Aspergillus candidus LDJ-5. Their structures were determined by NMR and MS data. Differing from the previously reported p-terphenyls, asperterphenyllin A represents the first p-terphenyl dimer connected by a C-C bond. Asperterphenyllin A displayed anti-influenza virus A (H1N1) activity and protein tyrosine phosphatase 1B (PTP1B) inhibitory activity with IC₅₀ values of 53 μM and 21 μM, respectively. The anti-influenza virus A (H1N1) activity and protein tyrosine phosphatase 1B (PTP1B) inhibitory activity of p-terphenyls are reported for the first time. Asperterphenyllin G exhibited cytotoxicity against nine cell lines with IC₅₀ values ranging from 0.4 to 1.7 μM. Asperterphenyllin C showed antimicrobial activity against Proteus species with a MIC value of 19 μg/mL.

Redox Regulation of the Actin Cytoskeleton in Cell Migration and Adhesion: On the Way to a Spatiotemporal View

The actin cytoskeleton of eukaryotic cells is a dynamic, fibrous network that is regulated by the concerted action of actin-binding proteins (ABPs). In particular, rapid polarization of cells in response to internal and external stimuli is fundamental to cell migration and invasion. Various isoforms of ABPs in different tissues equip cells with variable degrees of migratory and adhesive capacities. In addition, regulation of ABPs by posttranslational modifications (PTM) is pivotal to the rapid responsiveness of cells. In this context, phosphorylation of ABPs and its functional consequences have been studied extensively. However, the study of reduction/oxidation (redox) modifications of oxidation-sensitive cysteine and methionine residues of actin, ABPs, adhesion molecules, and signaling proteins regulating actin cytoskeletal dynamics has only recently emerged as a field. The relevance of such protein oxidations to cellular physiology and pathophysiology has remained largely elusive. Importantly, studying protein oxidation spatiotemporally can provide novel insights into localized redox regulation of cellular functions. In this review, we focus on the redox regulation of the actin cytoskeleton, its challenges, and recently developed tools to study its physiological and pathophysiological consequences.

Synthesis and Evaluation of a Novel Series of 2,7-Substituted-6-tetrazolyl-1,2,3,4-tetrahydroisoquinoline Derivatives as Selective Peroxisome Proliferator-Activated Receptor γ Partial Agonists

A novel series of 7-substituted-2-[3-(2-furyl)acryloyl]-6-tetrazolyl-1,2,3,4-tetrahydroisoquinoline derivatives were synthesized to clarify structure-activity relationships for peroxisome proliferator-activated receptor γ (PPARγ) partial agonist activity and identify more efficacious PPARγ partial agonists with minor adverse effects. Among the derivatives synthesized, compound 26v with a 2-(2,5-dihydropyrrol-1-yl)-5-methyloxazol-4-ylmethoxy group at the 7-position of the tetrahydroisoquinoline structure exhibited stronger PPARγ agonist and antagonist activities (EC50 = 6 nM and IC50 = 101 nM) than previously reported values for compound 1 (EC50 = 13 nM and IC50 = 512 nM). Compound 26v had very weak protein tyrosine phosphatase 1B (PTP1B) inhibitory activity and showed higher oral absorption (Cmax = 11.4 µg/mL and area under the curve (AUC) = 134.7 µg·h/mL) than compound 1 (Cmax = 7.0 µg/mL and AUC = 63.9 µg·h/mL) in male Sprague-Dawley (SD) rats. A computational docking calculation revealed that 26v bound to PPARγ in a similar manner to that of compound 1. In male Zucker fatty rats, 26v and pioglitazone at 10 and 30 mg/kg for 4 weeks similarly reduced plasma triglyceride levels, increased plasma adiponectin levels, and attenuated increases in plasma glucose levels in the oral glucose tolerance test, while only pioglitazone decreased hematocrit values. In conclusion, 6-tetrazolyl-1,2,3,4-tetrahydroisoquinoline derivatives provide a novel scaffold for selective PPARγ partial agonists and 26v attenuates insulin resistance possibly by adiponectin enhancements with minor adverse effects.

Tubeimoside I Inhibits Cell Proliferation and Induces a Partly Disrupted and Cytoprotective Autophagy Through Rapidly Hyperactivation of MEK1/2-ERK1/2 Cascade via Promoting PTP1B in Melanoma

Tubeimoside I (TBMS1), also referred to as tubeimoside A, is a natural compound extracted from the plant Tu Bei Mu (Bolbostemma paniculatum), which is a traditional Chinese herb used to treat multiple diseases for more than 1,000 years. Studies in recent years reported its anti-tumor activity in several cancers. However, whether it is effective in melanoma remains unknown. In the current study, we discovered that TBMS1 treatment inhibited melanoma cell proliferation in vitro and tumorigenecity in vivo. Besides, we also observed that TBMS1 treatment induced a partly disrupted autophagy, which still remained a protective role, disruption of which by chloroquine (CQ) or 3-methyladenine (3-MA) enhanced TBMS1-induced cell proliferation inhibition. CQ combined with TBMS1 even induced cellular apoptosis. BRAF(V600E) mutation and its continuously activated downstream MEK1/2-ERK1/2 cascade are found in 50% of melanomas and are important for malanomagenesis. However, hyperactivating MEK1/2-ERK1/2 cascade can also inhibit tumor growth. Intriguingly, we observed that TBMS1 rapidly hyperactivated MEK1/2-ERK1/2, inhibition of which by its inhibitor SL-327 rescued the anti-cancerous effects of TBMS1. Besides, the targets of TBMS1 were predicted by the ZINC Database based on its structure. It is revealed that protein-tyrosine phosphatase 1B (PTP1B) might be one of the targets of TBMS1. Inhibition of PTP1B by its selective inhibitor TCS401 or shRNA rescued the anti-cancerous effects of TBMS1 in melanoma cells. These results indicated that TBMS1 might activate PTP1B, which further hyperactivates MEK1/2-ERK1/2 cascade, thereby inhibiting cell proliferation in melanoma. Our results provided the potentiality of TBMS1 as a drug candidate for melanoma therapy and confirmed that rapidly hyperactivating an oncogenic signaling pathway may also be a promising strategy for cancer treatment.

Green Tea Catechins Induce Inhibition of PTP1B Phosphatase in Breast Cancer Cells with Potent Anti-Cancer Properties: In Vitro Assay, Molecular Docking, and Dynamics Studies

The catechins derived from green tea possess antioxidant activity and may have a potentially anticancer effect. PTP1B is tyrosine phosphatase that is oxidative stress regulated and is involved with prooncogenic pathways leading to the formation of a.o. breast cancer. Here, we present the effect of selected green tea catechins on enzymatic activity of PTP1B phosphatase and viability of MCF-7 breast cancer cells. We showed also the computational analysis of the most effective catechin binding with a PTP1B molecule. We observed that epigallocatechin, epigallocatechin gallate, epicatechin, and epicatechin gallate may decrease enzymatic activity of PTP1B phosphatase and viability of MCF-7 cells. Conclusions: From the tested compounds, epigallocatechin and epigallocatechin gallate were the most effective inhibitors of the MCF-7 cell viability. Moreover, epigallocatechin was also the strongest inhibitor of PTP1B activity. Computational analysis allows us also to conclude that epigallocatechin is able to interact and bind to PTP1B. Our results suggest also the most predicted binding site to epigallocatechin binding to PTP1B.

The phosphatase PTPN1/PTP1B is a candidate marker of better chemotherapy response in metastatic high-grade serous carcinoma

OBJECTIVE

To analyse the expression and clinical role of the phosphatase PTPN1 (PTP1B) in serous effusions.

METHODS

PTPN1 mRNA expression by quantitative RT-PCR was analysed in 83 high-grade serous carcinoma (HGSC) and 15 malignant mesothelioma (MM) effusions. PTP1B and phospho-PTP1B (pPTP1B) protein expression by immunohistochemistry was analysed in 62 HGSC and 44 MM effusions.

RESULTS

PTPN1 mRNA (P = .048), PTP1B protein (P = .047) and pPTP1B protein (P < .001) were overexpressed in HGSC compared to MM effusions. PTPN1 mRNA was additionally overexpressed in post-chemotherapy HGSC effusions compared to chemo-naïve effusions (P = .005). However, pPTP1B protein expression was higher in effusions from patients with FIGO stage III compared to stage IV (P = .006), and higher expressions of both PTPN1 mRNA (P = .041) and PTP1B protein (P = .035) in HGSC effusions were associated with better (complete) chemotherapy response at diagnosis. PTPN1 RNA and protein expression was unrelated to survival in HGSC, whereas a trend for shorter overall survival (P = .06) was found for MM patients whose tumours expressed pPTP1B protein.

CONCLUSION

PTPN1 is overexpressed in HGSC compared to MM effusions, and may be a marker of better chemotherapy response in the former. Whether PTPN1 activation is informative of adverse outcome in MM merits further investigation.

The biological activities of the spiderworts (Tradescantia)

Widely used throughout the world as traditional medicine for treating a variety of diseases ranging from cancer to microbial infections, members of the Tradescantia genus show promise as sources of desirable bioactive compounds. The bioactivity of several noteworthy species has been well-documented in scientific literature, but with nearly seventy-five species, there remains much to explore in this genus. This review aims to discuss all the bioactivity-related studies of Tradescantia plants and the compounds discovered, including their anticancer, antimicrobial, antioxidant, and antidiabetic activities. Gaps in knowledge will also be identified for future research opportunities.

CAPN1 promotes malignant behavior and erlotinib resistance mediated by phosphorylation of c-Met and PIK3R2 via degrading PTPN1 in lung adenocarcinoma

BACKGROUND

Calpain 1 (CAPN1) has been found to be a promoter of cancer progression. PTPN1 as a physiological target molecule of CAPN1 plays a dephosphorylated role on multiple receptor tyrosine kinases. This study aimed to reveal the effects of CAPN1/PTPN1 on malignant phenotype and EGFR-TKI resistance of lung adenocarcinoma (LUAD) cells.

METHODS

A total of 84 primary LUAD tissues and paired paracancerous normal tissues were collected. Quantitative real-time PCR (qRT-PCR) and immunohistochemical (IHC) methods were used to measure the expression of CAPN1 and PTPN1 in tissues. qRT-PCR and western blot were used to detect the expressions of CAPN1, PTPN1, c-Met and PIK3R2 in cell lines. Cell counting kit-8 (CCK-8), colony formation and transwell assay were carried out to evaluate cell erlotinib resistance, proliferation, migration and invasion. Co-IP assay was used to verify the interaction between proteins. Cycloheximide (CHX) was applied to block protein synthesis.

RESULTS

CAPN1, c-Met and PIK3R2 were significantly upregulated and the correlation was positive in LUAD, while PTPN1 was decreased. EGFR-sensitive mutation was related to CAPN1/PTPN1. in vitro studies showed that PTPN1 can mediate dephosphorylation of c-Met and PIK3R2 by binding with both, thereby weakening cell proliferation, metastasis and erlotinib resistance, while CAPN1 could enhance the degradation of PTPN1 protein as a cancer promoter.

CONCLUSIONS

CAPN1 enhances the malignant behavior and erlotinib resistance of LUAD cells via degrading PTPN1 and then activating c-Met/PIK3R2, which suggests CAPN1/PTPN1 may serve as tumor markers or potential targets for diagnosis and treatment of LUAD.

KEY POINTS

Significant findings of the study Superior CAPN1 and inferior PTPN1 were related to activation of c-Met/PIK3R2 in lung adenocarcinoma. Moreover, regulations of CAPN1 and PTPN1 induced the changes of malignant behavior and erlotinib resistance. What this study adds Our findings confirmed that CAPN1/PTPN1 play crucial roles on proliferation, metastasis and erlotinib resistance of LUAD cells as c-Met/PIK3R2 regulators, and validated the regulatory mechanism of CAPN1 on PTPN1 in tumor model for the first time.

A Preliminary Study on the Effect and Mechanism of Breviscapine for Improving Insulin Resistance in HepG2 Cells

Insulin resistance (IR) is known to be a critical factor, which can lead to the onset of type 2 diabetes. Traditional Chinese medicine (TCM) has special advantages in treating IR, but the active components and action mechanisms of most TCM remain unclear. Therefore, the elucidation of the potential mechanisms is a major challenge in TCM research. In the study, we tried to elucidate the potential pharmacological efficacy and mechanism of breviacapine for improving IR through network analysis and validate the possible biological target for its quality evaluation. We computationally recognized the active components, potential targets, and the targets closely related to IR by using integrative analysis based on network pharmacology approach. We also established the active components-targets network, protein interactions network and analyzing the biological functions and pathways of targets to evaluate the links between components and pharmacological actions to help explain the action mechanisms of breviscapine. Based on the network analysis, our experimental data preliminarily confirmed that breviscapine could improve IR in HepG2 cells, which may be associated with the dynamic regulation of the PTP1B. This study combined network pharmacology with partial experiment validation to clarify the underlying mechanism of breviscapine in improving IR and thus laid the experimental foundation for the depth exploration of its functional mechanism.

Inhibition of protein-tyrosine phosphatase 1B phosphorylation enhances early adhesion of mesenchymal stem cells to facilitate fabrication of tissue-engineered bone

Enhancement of cell-matrix adhesion is preferable and crucial in various fields of tissue engineering. Integrins are important receptors that facilitate cell-matrix adhesion, mediated by intracellular molecules and crosstalk with the cadherin adhesion pathway, which mainly facilitates cell-cell adhesion. Protein-tyrosine phosphatase 1B (PTP1B) has emerged as a pivot in the crosstalk between the cadherin adhesion pathway and the integrin adhesion pathway. The phosphorylation state of PTP1B tyrosine-152 (Y152) plays a central role in balancing the two different cell adhesion forms. In this study, a PTP1B Y152 region mimicking (152RM) peptide was designed to decrease the phosphorylation of PTP1B Y152 via competitive inhibition. As a result, the dissociation of cadherin complexes and the release of PTP1B from cadherin had sharply increased, and Src, an important intracellular component of integrin, was activated, indicating that the cadherin adhesion pathway was inhibited, whereas the integrin adhesion pathway was enhanced. Moreover, upon treatment with the 152RM peptide, we observed that the early adhesion of human bone marrow-derived mesenchymal stem cells (MSCs) was accelerated and the anchoring of MSCs on the surface of integrin ligands was enhanced by an enhanced matrix adhesion ability of MSCs themselves. Importantly, the 152RM peptide significantly promoted the adhesion efficiency of MSCs in the selective cell retention technology, which fabricates instant bone implants in clinical settings, to stimulate osteogenesis in vivo.

Protein Tyrosine Phosphatase-1B Inhibition Disrupts IL13Rα2-Promoted Invasion and Metastasis in Cancer Cells

Background: Interleukin 13 receptor alpha 2 subunit (IL13Rα2) is overexpressed in glioblastoma (GBM), metastatic colorectal cancer (CRC) and ovarian cancer (OC). Here, we investigated the IL13Rα2 interactome searching for novel targets in cancer invasion and metastasis. Methods: The interactome of IL13Rα2 was determined in GBM by using a proteomic analysis and then validated in CRC and OC. Cell signaling was investigated using siRNA interference, protein tyrosine phosphatase-1B (PTP1B) inhibitors and Western blot analysis. Animal models of GBM and metastatic CRC were used for testing PTP1B inhibitors. Results: PTP1B was identified and validated as a mediator of IL13Rα2 signaling. An in silico analysis revealed that PTP1B overexpression is associated with lower overall survival of patients in the three types of cancer. PTP1B silencing or treatment with Claramine, a PTP1B inhibitor, caused a significant decrease in IL-13-mediated adhesion, migration and invasion of IL13Rα2-expressing cancer cells by inhibiting the dephosphorylation of Src Tyr₅₃₀ and consequently, the phosphorylation of Src Tyr₄₁₉, AKT and ERK1/2. In addition, Claramine inhibited EGF-mediated activation of EGFR Tyr_1068. In vivo treatment with Claramine caused a total inhibition of liver metastasis in mice inoculated with CRC cells and a significant increase in the survival of mice bearing intracranial GBM patient-derived xenografts. Conclusions: We have uncovered that IL13 signaling through IL13Rα2 requires PTP1B activity and therefore, PTP1B inhibition represents a promising therapeutic strategy in multiple types of cancer, including glioblastoma.