The role of protein tyrosine phosphatases in prostate cancer biology

Neural stem cell relay from B1 to B2 cells in the adult mouse ventricular-subventricular zone

Neurogenesis and gliogenesis continue in the ventricular-subventricular zone (V-SVZ) of the adult rodent brain. V-SVZ astroglial cells with apical contact with the ventricle (B1 cells) function as neural stem cells (NSCs). B1 cells sharply decline during early postnatal life; in contrast, neurogenesis decreases at a slower rate. Here, we show that a second population of astroglia (B2 cells) that do not contact the ventricle also function as NSCs in the adult mouse brain. B2 cell numbers increase postnatally, are sustained in adults, and decrease with aging. We reveal the transcriptomic profile of B1 and B2 cells and show that, like B1 cells, B2 cells can be quiescent or activated. Transplantation and lineage tracing of B2 cells demonstrate their function as primary progenitors for adult neurogenesis. This study reveals that NSC function is progressively relayed from B1 to B2 progenitors helping explain how neurogenesis is maintained into adult life.

Lathyrol affects the expression of AR and PSA and inhibits the malignant behavior of RCC cells

Objective

To investigate how lathyrol affects aggressive behaviors and related proteins of the androgen receptor (AR) 786-O cells.

Methods

786-O cells were cultured in vitro and divided into these groups at random: the dimethylsulfoxide (DMSO) control group (A group), negative control group (B group), and experimental group (C group). Cells in A group were grown in DMSO working medium (contained RPMI 1640 medium and 1% DMSO), B group cells were cultured in nilutamide working medium (contained DMSO working medium and 325 μg/mL nilutamide), while those in C group were cultured in lathyrol working medium (contained DMSO working medium and 300 μg/mL lathyrol). Cell proliferation was measured via CCK-8 assays, and cell apoptosis was examined through terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining. Scratch tests and Transwell invasion tests were used to evaluate cell movement and penetration. The expression information about p-AR, AR, p-Akt, ki67, caspase3, cleaved-caspase3, Bcl-2, Bax, caspase9, cleaved-caspase9, and GAPDH proteins was investigated through western blotting. Immunocytochemistry was used to identify the 786-O cells' secretion level of matrix metalloproteinase 2 (MMP2), MMP9, and prostate-specific antigen (PSA) proteins.

Results

The negative control and experimental groups' cells exhibited reduced proliferation, migration, and invasion and increased apoptosis after 24 h treatment. Furthermore, these two group cells exhibited a notable reduction in the status of Ki67, Bcl-2, MMP2, MMP9, and p-Akt (P < 0.05) and significantly increased the expressions of AR, p-AR, Bax, cleaved-caspase3, and cleaved-caspase9 (P < 0.05). There was no statistical distance in PSA, caspase3, and caspase9 expressions among the three groups (P > 0.05).

Conclusion

In vitro, lathyrol and nilutamide exert notable anticancer effects by effectively suppressing the proliferation, migration, and invasion of 786-O cells while also inducing apoptosis.

Identification of new small molecule allosteric SHP2 inhibitor through pharmacophore-based virtual screening, molecular docking, molecular dynamics simulation studies, synthesis and in vitro evaluation

Src homology-2 (SH2) domain-containing phosphatase-2 (SHP2) is the first identified protooncogene and is a promising target for developing small molecule inhibitors as cancer chemotherapeutic agents. Pharmacophore-based virtual screening (PBVS) is a pharmacoinformatics methodology that employs physicochemical knowhow of the chemical space into the dynamic environs of computational technology to extract virtual molecular hits that are precise and promising for a drug target. In the current study, PBVS has been applied on EnamineTM Advanced Collection of 551,907 molecules by using a pharmacophore model developed upon SHP099 by Molecular Operating Environment (MOE) software to identify potential small molecule allosteric SHP2 inhibitors. Obtained 37 hits were further filtered through DruLiTo software for drug-likeness and PAINS remover which yielded 35 hits. These were subjected to molecular docking studies against the tunnel allosteric site of SHP2 (PDB ID: 5EHR) to screen them according to their binding affinity for the enzyme. Top 5 molecules having highest binding affinity for 5EHR were passed through an ADMET prediction screening and the top 2 hits (ligands 111675 and 546656) with the most favourable ADMET profile were taken for post screening molecular docking and MD simulation studies. From the protein-ligand interaction pattern, conformational stability and energy parameters, ligand 111675 (SHP2 Ki = 0.118 µM) resulted as the most active molecule. Further, the synthesis and in vitro evaluation of the lead compound 111675 unveiled its potent inhibitory activity (IC50 = 0.878 ± 0.008 µM) against SHP2.Communicated by Ramaswamy H. Sarma.

Neural Stem Cell Relay from B1 to B2 cells in the adult mouse Ventricular-Subventricular Zone

Neurogenesis and gliogenesis continue in the Ventricular-Subventricular Zone (V-SVZ) of the adult rodent brain. B1 cells are astroglial cells derived from radial glia that function as primary progenitors or neural stem cells (NSCs) in the V-SVZ. B1 cells, which have a small apical contact with the ventricle, decline in numbers during early postnatal life, yet neurogenesis continues into adulthood. Here we found that a second population of V-SVZ astroglial cells (B2 cells), that do not contact the ventricle, function as NSCs in the adult brain. B2 cell numbers increase postnatally, remain constant in 12-month-old mice and decrease by 18 months. Transcriptomic analysis of ventricular-contacting and non-contacting B cells revealed key molecular differences to distinguish B1 from B2 cells. Transplantation and lineage tracing of B2 cells demonstrate their function as primary progenitors for adult neurogenesis. This study reveals how NSC function is relayed from B1 to B2 progenitors to maintain adult neurogenesis.

Heparin Oligosaccharides as Vasoactive Intestinal Peptide Inhibitors via their Binding Process Characterization

BACKGROUND

It has been proven that vasoactive intestinal peptide (VIP) was involved in the pathogenesis of prostate cancer. Cardin et al. found that by an alanine scan, the heparin- binding site on VIP was exactly the same sequence in VIP and its receptor. Therefore, heparin could competitively block the binding of VIP and its receptor. However, the structure-activity relationship between heparin and VIP has not been reported, especially in terms of the sequence and sulfation patterns of heparin oligosaccharides upon binding to VIP.

OBJECTIVE

A variety of experiments were designed to study the binding process and structure-activity relationship between heparin oligosaccharides and VIP.

METHODS

Heparin was enzymatically digested and purified to produce heparin oligosaccharides, and the structures were characterized by NMR. The binding capacity between heparin oligosaccharides and VIP was analyzed by GMSA and ITC experiments. The binding between heparin oligosaccharides and VIP was simulated using a molecular docking program to show the complex. ELISA assay was used to investigate the effect of non-anticoagulant heparin oligosaccharides on the VIP-mediated cAMP/PKA signaling pathway in vitro.

RESULTS

The results indicated that both the length and the sulfation pattern of heparin oligosaccharides affected its binding to VIP. VIP could induce the expression of cAMP at a higher level in PC3 cells, which could be regulated by the interaction of heparin oligosaccharides and VIP.

CONCLUSION

The binding between heparin oligosaccharides and VIP could block the binding between VIP and its receptor on tumor cells. Downloading the regulation of the expression level of cAMP could possibly further affect the subsequent activation of PKA. These non-anticoagulant heparin oligosaccharides may block the VIP-mediated cAMP/PKA signaling pathway and thus exert their antitumor activity.

Extracellular Matrix- and Integrin Adhesion Complexes-Related Genes in the Prognosis of Prostate Cancer Patients' Progression-Free Survival

Prostate cancer is a heterogeneous disease, and one of the main obstacles in its management is the inability to foresee its course. Therefore, novel biomarkers are needed that will guide the treatment options. The extracellular matrix (ECM) is an important part of the tumor microenvironment that largely influences cell behavior. ECM components are ligands for integrin receptors which are involved in every step of tumor progression. An underlying characteristic of integrin activation and ligation is the formation of integrin adhesion complexes (IACs), intracellular structures that carry information conveyed by integrins. By using The Cancer Genome Atlas data, we show that the expression of ECM- and IACs-related genes is changed in prostate cancer. Moreover, machine learning methods revealed that they are a source of biomarkers for progression-free survival of patients that are stratified according to the Gleason score. Namely, low expression of FMOD and high expression of PTPN2 genes are associated with worse survival of patients with a Gleason score lower than 9. The FMOD gene encodes protein that may play a role in the assembly of the ECM and the PTPN2 gene product is a protein tyrosine phosphatase activated by integrins. Our results suggest potential biomarkers of prostate cancer progression.

Sequence level genome-wide associations for bull production and fertility traits in tropically adapted bulls

BACKGROUND

The genetics of male fertility is complex and not fully understood. Male subfertility can adversely affect the economics of livestock production. For example, inadvertently mating bulls with poor fertility can result in reduced annual liveweight production and suboptimal husbandry management. Fertility traits, such as scrotal circumference and semen quality are commonly used to select bulls before mating and can be targeted in genomic studies. In this study, we conducted genome-wide association analyses using sequence-level data targeting seven bull production and fertility traits measured in a multi-breed population of 6,422 tropically adapted bulls. The beef bull production and fertility traits included body weight (Weight), body condition score (CS), scrotal circumference (SC), sheath score (Sheath), percentage of normal spermatozoa (PNS), percentage of spermatozoa with mid-piece abnormalities (MP) and percentage of spermatozoa with proximal droplets (PD).

RESULTS

After quality control, 13,398,171 polymorphisms were tested for their associations with each trait in a mixed-model approach, fitting a multi-breed genomic relationship matrix. A Bonferroni genome-wide significance threshold of 5 × 10^- 8 was imposed. This effort led to identifying genetic variants and candidate genes underpinning bull fertility and production traits. Genetic variants in Bos taurus autosome (BTA) 5 were associated with SC, Sheath, PNS, PD and MP. Whereas chromosome X was significant for SC, PNS, and PD. The traits we studied are highly polygenic and had significant results across the genome (BTA 1, 2, 4, 6, 7, 8, 11, 12, 14, 16, 18, 19, 23, 28, and 29). We also highlighted potential high-impact variants and candidate genes associated with Scrotal Circumference (SC) and Sheath Score (Sheath), which warrants further investigation in future studies.

CONCLUSION

The work presented here is a step closer to identifying molecular mechanisms that underpin bull fertility and production. Our work also emphasises the importance of including the X chromosome in genomic analyses. Future research aims to investigate potential causative variants and genes in downstream analyses.

Correlation of expression of Major Vault Protein with androgen receptor and immune checkpoint protein B7-H3, and with poor prognosis in prostate cancer

Prostate cancer diagnosis and early stratification is an important aspect to avoid undertreatment of high-risk prostate cancer patients. Major Vault Protein (MVP) has been proposed as a prognostic biomarker in prostate cancer. PTEN and the immune checkpoint protein B7-H3 interact with MVP and are important in prostate cancer progression and therapy response. We evaluated the expression of MVP by immunohistochemistry of tissue microarray samples from a retrospective cohort consisting of 119 prostate cancer patients. We correlated the protein expression of MVP with clinicopathological characteristics, and protein expression of androgen receptor (AR), PTEN, immune checkpoint proteins B7-H3 and PD-L1. We found MVP to be expressed in 53 % of prostate tumors, and correlated positively with biochemical recurrence (ρ = 0.211/p = 0.021). Furthermore, we found positive correlation of MVP expression with expression of AR (ρ = 0.244/p = 0.009) and the immune checkpoint protein B7-H3 (ρ = 0.200/p = 0.029), but not with PD-L1 (ρ = 0.152/p = 0.117) or PTEN expression (ρ = - 0.034/p = 0.721). Our findings support the notion that expression of MVP is associated with poor prognosis in prostate cancer. The correlation between MVP and immune checkpoint protein B7-H3 in prostate cancer suggests a role for MVP in immunoregulation and drug resistance.

Nuclear size rectification: A potential new therapeutic approach to reduce metastasis in cancer

Research on metastasis has recently regained considerable interest with the hope that single cell technologies might reveal the most critical changes that support tumor spread. However, it is possible that part of the answer has been visible through the microscope for close to 200 years. Changes in nuclear size characteristically occur in many cancer types when the cells metastasize. This was initially discarded as contributing to the metastatic spread because, depending on tumor types, both increases and decreases in nuclear size could correlate with increased metastasis. However, recent work on nuclear mechanics and the connectivity between chromatin, the nucleoskeleton, and the cytoskeleton indicate that changes in this connectivity can have profound impacts on cell mobility and invasiveness. Critically, a recent study found that reversing tumor type-dependent nuclear size changes correlated with reduced cell migration and invasion. Accordingly, it seems appropriate to now revisit possible contributory roles of nuclear size changes to metastasis.

Genome-wide interrogation of structural variation reveals novel African-specific prostate cancer oncogenic drivers

BACKGROUND

African ancestry is a significant risk factor for advanced prostate cancer (PCa). Mortality rates in sub-Saharan Africa are 2.5-fold greater than global averages. However, the region has largely been excluded from the benefits of whole genome interrogation studies. Additionally, while structural variation (SV) is highly prevalent, PCa genomic studies are still biased towards small variant interrogation.

METHODS

Using whole genome sequencing and best practice workflows, we performed a comprehensive analysis of SVs for 180 (predominantly Gleason score ≥ 8) prostate tumours derived from 115 African, 61 European and four ancestrally admixed patients. We investigated the landscape and relationship of somatic SVs in driving ethnic disparity (African versus European), with a focus on African men from southern Africa.

RESULTS

Duplication events showed the greatest ethnic disparity, with a 1.6- (relative frequency) to 2.5-fold (count) increase in African-derived tumours. Furthermore, we found duplication events to be associated with CDK12 inactivation and MYC copy number gain, and deletion events associated with SPOP mutation. Overall, African-derived tumours were 2-fold more likely to present with a hyper-SV subtype. In addition to hyper-duplication and deletion subtypes, we describe a new hyper-translocation subtype. While we confirm a lower TMPRSS2-ERG fusion-positive rate in tumours from African cases (10% versus 33%), novel African-specific PCa ETS family member and TMPRSS2 fusion partners were identified, including LINC01525, FBXO7, GTF3C2, NTNG1 and YPEL5. Notably, we found 74 somatic SV hotspots impacting 18 new candidate driver genes, with CADM2, LSAMP, PTPRD, PDE4D and PACRG having therapeutic implications for African patients.

CONCLUSIONS

In this first African-inclusive SV study for high-risk PCa, we demonstrate the power of SV interrogation for the identification of novel subtypes, oncogenic drivers and therapeutic targets. Identifying a novel spectrum of SVs in tumours derived from African patients provides a mechanism that may contribute, at least in part, to the observed ethnic disparity in advanced PCa presentation in men of African ancestry.

Heterogeneous Expression and Subcellular Localization of Pyruvate Dehydrogenase Complex in Prostate Cancer

Background

Pyruvate dehydrogenase (PDH) complex converts pyruvate into acetyl-CoA by pyruvate decarboxylation, which drives energy metabolism during cell growth, including prostate cancer (PCa) cell growth. The major catalytic subunit of PDH, PDHA1, is regulated by phosphorylation/dephosphorylation by pyruvate dehydrogenase kinases (PDKs) and pyruvate dehydrogenase phosphatases (PDPs). There are four kinases, PDK1, PDK2, PDK3 and PDK4, which can phosphorylate and inactivate PDH; and two phosphatases, PDP1 and PDP2, that dephosphorylate and activate PDH.

Methods

We have analyzed by immunohistochemistry the expression and clinicopathological correlations of PDHA1, PDP1, PDP2, PDK1, PDK2, PDK3, and PDK4, as well as of androgen receptor (AR), in a retrospective PCa cohort of patients. A total of 120 PCa samples of representative tumor areas from all patients were included in tissue microarray (TMA) blocks for analysis. In addition, we studied the subcellular localization of PDK2 and PDK3, and the effects of the PDK inhibitor dichloroacetate (DCA) in the growth, proliferation, and mitochondrial respiration of PCa cells.

Results

We found heterogeneous expression of the PDH complex components in PCa tumors. PDHA1, PDP1, PDK1, PDK2, and PDK4 expression correlated positively with AR expression. A significant correlation of PDK2 immunostaining with biochemical recurrence and disease-free survival was revealed. In PCa tissue specimens, PDK2 displayed cytoplasmic and nuclear immunostaining, whereas PDK1, PDK3 and PDK4 showed mostly cytoplasmic staining. In cells, ectopically expressed PDK2 and PDK3 were mainly localized in mitochondria compartments. An increase in maximal mitochondrial respiration was observed in PCa cells upon PDK inhibition by DCA, in parallel with less proliferative capacity.

Conclusion

Our findings support the notion that expression of specific PDH complex components is related with AR signaling in PCa tumors. Furthermore, PDK2 expression associated with poor PCa prognosis. This highlights a potential for PDH complex components as targets for intervention in PCa.

Post-Translational Modifications That Drive Prostate Cancer Progression

While a protein primary structure is determined by genetic code, its specific functional form is mostly achieved in a dynamic interplay that includes actions of many enzymes involved in post-translational modifications. This versatile repertoire is widely used by cells to direct their response to external stimuli, regulate transcription and protein localization and to keep proteostasis. Herein, post-translational modifications with evident potency to drive prostate cancer are explored. A comprehensive list of proteome-wide and single protein post-translational modifications and their involvement in phenotypic outcomes is presented. Specifically, the data on phosphorylation, glycosylation, ubiquitination, SUMOylation, acetylation, and lipidation in prostate cancer and the enzymes involved are collected. This type of knowledge is especially valuable in cases when cancer cells do not differ in the expression or mutational status of a protein, but its differential activity is regulated on the level of post-translational modifications. Since their driving roles in prostate cancer, post-translational modifications are widely studied in attempts to advance prostate cancer treatment. Current strategies that exploit the potential of post-translational modifications in prostate cancer therapy are presented.

Rational design of PIN1 inhibitors for cancer treatment based on conformational diversity analysis and docking based virtual screening

The parvulin PIN1 (peptidyl-prolyl cis-trans isomerase NIMA-interacting 1), is the only enzyme capable of isomerizing prolines of phospho-Serine/Threonine-Proline motifs. PIN1 binds to a subset of proteins and plays an essential role in regulating protein function post-phosphorylation control. Furthermore, the activity of PIN1 regulates the outcome of the signalling of proline-directed kinases (e.g. MAPK, CDK, or GSK3) and thus regulates cell proliferation and cell survival. For these reasons, PIN1 inhibitors are interesting since they may have therapeutic implications for cancer. Several authors have already reported that the non-structural point mutation Trp34Ala prevents PIN1 from interacting with its downstream effector proteins. In this work, we characterized PIN1 structurally, intending to explore new inhibition targets for the rational design of pharmacological activity compounds. Through a conformational diversity analysis of PIN1, we identified and characterized a highly specific druggable pocket around the residue Trp34. This pocket was used in a high-throughput docking screening of 450,000 drug-like compounds, and the top 10 were selected for re-docking studies on the previously used conformers. Finally, we evaluated the binding of each compound by thermal shift assay and found four molecules with a high affinity for PIN1 and potential inhibitory activity. Through this strategy, we achieved novel drug candidates with the ability to interfere with the phosphorylation-dependent actions of PIN1 and with potential applications in the treatment of cancer.Communicated by Ramaswamy H. Sarma.

PTPRA facilitates cancer growth and migration via the TNF-α-mediated PTPRA-NF-κB pathway in MCF-7 breast cancer cells

Protein tyrosine phosphatase receptor type A (PTPRA), one of the classic protein tyrosine phosphatases, is crucial for modulating tumorigenesis and metastasis in breast cancer; however, its functional mechanism has not fully elucidated. The present study assessed PTPRA expression and estimated its clinical impact on survival using the Gene Expression Profiling Interactive Analysis database (GEPIA). Growth curves, colony formations and Transwell assays were utilized to examine cell proliferation and migration. Additionally, luciferase reporter assays were used to examine the potential tumor signaling pathways targeted by PTPRA in HEK293T cells. Furthermore, quantitative PCR (qPCR) was utilized to confirm the transcriptional regulation of PTPRA expression. Bioinformatic analyses of data from GEPIA identified PTPRA overexpression in patients with breast cancer. The growth curve, colony formation and transwell experiments demonstrated that PTPRA upregulation significantly promoted the cell proliferation and migration of MCF-7 breast cancer cells. In contrast, PTPRA knockdown significantly attenuated cell proliferation and migration. Mechanistic experiments revealed that the transcriptional activity of NF-κB was higher compared with other classic tumor pathways when they were activated by PTPRA in HEK293T cells. Furthermore, the transcriptional activity of NF-κB was altered in a PTPRA-dose-dependent manner. Additionally, following exposure to TNF-α, PTPRA-deficient MCF-7 cells exhibited lower NF-κB transcriptional activity compared with normal control cells. The results of the present study demonstrate that PTPRA overexpression accelerates inflammatory tumor phenotypes in breast cancer and that the TNF-α-mediated PTPRA-NF-κB pathway may offer novel insight into early diagnosis and optimum treatment for breast cancer.

The disruption of protein-protein interactions as a therapeutic strategy for prostate cancer

Prostate cancer (PCa) is one of the most common male-specific cancers worldwide, with high morbidity and mortality rates associated with advanced disease stages. The current treatment options of PCa are prostatectomy, hormonal therapy, chemotherapy or radiotherapy, the selection of which is usually dependent upon the stage of the disease. The development of PCa to a castration-resistant phenotype (CRPC) is associated with a more severe prognosis requiring the development of a new and effective therapy. Protein-protein interactions (PPIs) have been recognised as an emerging drug modality and targeting PPIs is a promising therapeutic approach for several diseases, including cancer. The efficacy of several compounds in which target PPIs and consequently impair disease progression were validated in phase I/II clinical trials for different types of cancer. In PCa, various small molecules and peptides proved successful in inhibiting important PPIs, mainly associated with the androgen receptor (AR), Bcl-2 family proteins, and kinases/phosphatases, thus impairing the growth of PCa cells in vitro. Moreover, a majority of these compounds require further validation in vivo and, preferably, in clinical trials. In addition, several other PPIs associated with PCa progression have been identified and now require experimental validation as potential therapeutic loci. In conclusion, we consider the disruption of PPIs to be a promising though challenging therapeutic strategy for PCa. Agents which modulate PPIs might be employed as a monotherapy or as an adjunct to classical chemotherapeutics to overcome drug resistance and improve efficacy. The discovery of new PPIs with important roles in disease progression, and of novel optimized strategies to target them are major challenges for the scientific and pharmacological communities.

Crosstalk Between Prostate Cancer Cells and Tumor-Associated Fibroblasts Enhances the Malignancy by Inhibiting the Tumor Suppressor PLZF

Although prostate cancer is clinically manageable during the early stages of progression, metastatic progression severely compromises the prognosis and leads to mortality. Constitutive activation of STAT3 has been connected to prostate cancer malignancy, and abolishing the STAT3 activity may diminish tumor growth and metastasis. However, its suppressor genes and pathways have not been well established. In this study, we show that promyelocytic leukemia zinc finger (PLZF) has a putative tumor-suppressor function in prostate cancer by inhibiting phosphorylation of STAT3. Compared with a benign prostate, high-grade prostate cancer patient tissue was negatively correlated with PLZF expression. PLZF depletion accelerated proliferation and survival, migration, and invasion in human prostate cancer cells. Mechanistically, we demonstrated a novel role of PLZF as the transcriptional regulator of the tyrosine phosphatase SHP-1 that inhibits the oncogenic JAKs–STAT3 pathway. These results suggest that the collapse of PLZF expression by the CCL3 derived from fibroblasts accelerates the cell migration and invasion properties of prostate cancer cells. Our results suggest that increasing PLZF could be an attractive strategy for suppressing prostate cancer metastasis as well as for tumor growth.

Loss of Tyrosine Phosphatase Delta Promotes Gastric Cancer Progression via Signal Transducer and Activator of Transcription 3 Pathways

BACKGROUND

The protein tyrosine phosphatase delta (PTPRD) is a tumor suppressor, and its role in gastric cancer (GC) remains poorly understood.

METHODS

The expressions of PTPRD were determined based on public data. In addition, the mRNA expressions of PTPRD in the GC samples, and the expressions of PTPRD in the GC cell lines including HGC27, SGC790, and BGC823, and gastric epithelial cell line GES-1 were determined by western blotting and quantitative real-time PCR. Furthermore, PTPRD siRNA was transfected into the HGC27 cell line, and then, cell proliferation, migration, and invasion were evaluated. The activity of signal transducer and activator of transcription 3 (STAT3) pathways in HGC27 cells transfected with PTPRD siRNA was determined by western blotting.

RESULTS

PTPRD deletion was found in the GC patients, and this deletion was found to be correlated with poor prognosis in the GC patients. Expression of PTPRD was significantly downregulated in gastric carcinoma specimens and tumor cell lines when compared with those in normal controls. PTPRD also plays a key role in the GC cells proliferation, invasion, and migration. Silencing PTPRD expression by siRNA dramatically promoted GC cells proliferation, invasion, and migration. Mechanism study demonstrated that phosphorylation of STAT3 was inhibited by silencing PTPRD expression and the according changes including inhibition of cell migration and invasion were observed.

CONCLUSION

This study supports PTPRD as a tumor suppressor and could be served as a marker for prognostic of GC. Silencing PTPRD could be a potential therapeutic in GC.

Tapping the therapeutic potential of protein tyrosine phosphatase 4A with small molecule inhibitors

Protein tyrosine phosphatases (PTPs) are emerging new targets for drug discovery. PTPs and protein tyrosine kinases (PTKs) maintain cellular homeostasis through opposing roles: tyrosine O-dephosphorylation and -phosphorylation, respectively. An imbalance in the phosphorylation equilibrium results in aberrant protein signaling and pathophysiological conditions. PTPs have historically been considered 'undruggable', in part due to a lack of evidence defining their relationship to disease causality and a focus on purely competitive inhibitors. However, a better understanding of protein-protein interfaces and shallow active sites has recently renewed interest in the pursuit of allosteric and orthosteric modulators of targets outside the major druggable protein families. While their biological mechanism of action still remains to be clarified, PTP4A1-3 (also referred to as PRL1-3) are validated oncology targets and play an important role in cell proliferation, metastasis, and tumor angiogenesis. In this Digest, recent syntheses and structure-activity relationships (SAR) of small molecule inhibitors (SMIs) of PTP4A1-3 are summarized, and enzyme docking studies of the most potent chemotype are highlighted. In particular, the thienopyridone scaffold has emerged as a potent lead structure to interrogate the function and druggability of this dual-specificity PTP.