Protein Tyrosine Phosphatase Receptor Zeta 1 as a Potential Target in Cancer Therapy and Diagnosis

Protein tyrosine phosphatase receptor zeta 1 (PTPRZ1) is a type V transmembrane tyrosine phosphatase that is highly expressed during embryonic development, while its expression during adulthood is limited. PTPRZ1 is highly detected in the central nervous system, affecting oligodendrocytes' survival and maturation. In gliomas, PTPRZ1 expression is significantly upregulated and is being studied as a potential cancer driver and as a target for therapy. PTPRZ1 expression is also increased in other cancer types, but there are no data on the potential functional significance of this finding. On the other hand, low PTPRZ1 expression seems to be related to a worse prognosis in some cancer types, suggesting that in some cases, it may act as a tumor-suppressor gene. These discrepancies may be due to our limited understanding of PTPRZ1 signaling and tumor microenvironments. In this review, we present evidence on the role of PTPRZ1 in angiogenesis and cancer and discuss the phenomenal differences among the different types of cancer, depending on the regulation of its tyrosine phosphatase activity or ligand binding. Clarifying the involved signaling pathways will lead to its efficient exploitation as a novel therapeutic target or as a biomarker, and the development of proper therapeutic approaches.

Implication of the PTN/RPTPβ/ζ Signaling Pathway in Acute Ethanol Neuroinflammation in Both Sexes: A Comparative Study with LPS

Binge drinking during adolescence increases the risk of alcohol use disorder, possibly by involving alterations of neuroimmune responses. Pleiotrophin (PTN) is a cytokine that inhibits Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ. PTN and MY10, an RPTPβ/ζ pharmacological inhibitor, modulate ethanol behavioral and microglial responses in adult mice. Now, to study the contribution of endogenous PTN and the implication of its receptor RPTPβ/ζ in the neuroinflammatory response in the prefrontal cortex (PFC) after acute ethanol exposure in adolescence, we used MY10 (60 mg/kg) treatment and mice with transgenic PTN overexpression in the brain. Cytokine levels by X-MAP technology and gene expression of neuroinflammatory markers were determined 18 h after ethanol administration (6 g/kg) and compared with determinations performed 18 h after LPS administration (5 g/kg). Our data indicate that Ccl2, Il6, and Tnfa play important roles as mediators of PTN modulatory actions on the effects of ethanol in the adolescent PFC. The data suggest PTN and RPTPβ/ζ as targets to differentially modulate neuroinflammation in different contexts. In this regard, we identified for the first time important sex differences that affect the ability of the PTN/RPTPβ/ζ signaling pathway to modulate ethanol and LPS actions in the adolescent mouse brain.

Inhibition of RPTPβ/ζ reduces chronic ethanol intake in adolescent mice and modulates ethanol effects on hippocampal neurogenesis and glial responses in a sex-dependent manner

Pleiotrophin (PTN) is a cytokine that modulates ethanol drinking and reward and regulates glial responses in different contexts. PTN is an inhibitor of Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ. Inhibition of RPTPβ/ζ reduces binge-like drinking in adult male mice. Whether inhibition of RPTPβ/ζ is effective in reducing ethanol consumption during adolescence and in both sexes remained to be studied. In this work, male and female adolescent mice underwent an intermittent access to ethanol (IAE) 2-bottle choice protocol. Treatment with MY10 (60 mg/kg, i.g.), a small-molecule RPTPβ/ζ inhibitor, reduced chronic 3-week ethanol consumption only in male mice. We detected an ethanol-induced overall decrease in hippocampal GFAPir and Iba1ir, independently of the treatment received, suggesting that RPTPβ/ζ is not key in the regulation of IAE-induced glial responses. However, we found a significant negative correlation between the size of microglial cells and the number of hippocampal neuronal progenitors only in male mice after IAE. This correlation was disrupted by treatment with MY10 before each drinking session, which may be related to the ability of MY10 to regulate the intensity of the perineuronal nets (PNNs) in the hippocampus in a sex-dependent manner. The data show for the first time that inhibition of RPTPβ/ζ reduces chronic voluntary ethanol consumption in adolescent mice in a sex-dependent manner. In addition, we show evidence for sex-specific differences in the effects of IAE on glial responses and hippocampal neurogenesis, which may be related to different actions of the RPTPβ/ζ signalling pathway in the brains of male and female mice.

PTN-PTPRZ1 signaling axis blocking mediates tumor microenvironment remodeling for enhanced glioblastoma treatment

Glioblastoma (GBM) is a malignant brain tumor with a poor prognosis that is highly heterogeneous and invasive. One of the most major challenges of GBM treatment in the clinic is the blood-brain barrier (BBB). Additionally, the tumor microenvironment (TME) is highly enriched with immunosuppressed M2-like tumor-associated macrophages (M2 TAMs) and glioblastoma stem cells (GSCs), which promoted the malignancy of GBM through the PTN-PTPRZ1 signaling axis. Here, we developed a self-assembled dual-targeted hybrid micelle (DT-GM1) as a nanocarrier to deliver the chemotherapeutic agent doxorubicin (DOX). We demonstrated that this DT-GM1/DOX can cross the BBB using in vitro and in vivo GBM models, and that M2pep and PTPRZ1 antibodies allow it to precisely target the tumor microenvironment where M2 TAMs and GSCs are enriched, increasing intracellular drug accumulation via multiple internalization pathways. Additionally, simultaneous elimination of M2 TAMs and GSCs blocked the PTN-PTPRZ1 signaling axis, resulting in less M2 TAM infiltration and increased polarization to the M1 phenotype, reshaping the immune microenvironment. Overall, we have established a nanocarrier that can penetrate the BBB and target the TME while also synergizing with GBM chemotherapeutic agents, providing a promising new strategy for GBM treatment.

Tissue Niche Miniature of Glioblastoma Patient Treated with Nano-Awakeners to Induce Suicide of Cancer Stem Cells

Patient-specific cancer therapies can evolve by vitalizing the mother tissue-like cancer niche, cellular profile, genetic signature, and drug responsiveness. This evolution has enabled the elucidation of a key mechanism along with development of the mechanism-driven therapy. After surgical treatment, glioblastoma (GBM) patients require prompt therapy within 14 days in a patient-specific manner. Hence, this study approaches direct culture of GBM patient tissue (1 mm diameter) in a microchannel network chip. Cancer vasculature-mimetic perfusion can support the preservation of the mother tissue-like characteristic signatures and microenvironment. When temozolomide and radiation are administered within 1 day, the responsiveness of the tissue in the chip reflected the clinical outcomes, thereby overcoming the time-consuming process of cell and organoid culture. When the tissue chip culture is continued, the intact GBM signature gets lost, and the outward migration of stem cells from the tissue origin increases, indicating a leaving-home effect on the family dismantle. Nanovesicle production using GBM stem cells enables self-chasing of the cells that escape the temozolomide effect owing to quiescence. The anti-PTPRZ1 peptide display and temozolomide loading to nanovesicles awakes cancer stem cells from the quiescent stage to death. This study suggests a GBM clinic-driven avatar platform and mechanism-learned nanotherapy for translation.

Cerebral Organoids Maintain the Expression of Neural Stem Cell-Associated Glycoepitopes and Extracellular Matrix

During development, the nervous system with its highly specialized cell types forms from a pool of relatively uniform stem cells. This orchestrated process requires tight regulation. The extracellular matrix (ECM) is a complex network rich in signaling molecules, and therefore, of interest in this context. Distinct carbohydrate structures, bound to ECM molecules like Tenascin C (TNC), are associated with neural stem/progenitor cells. We have analyzed the expression patterns of the LewisX (LeX) trisaccharide motif and of the sulfation-dependent DSD-1 chondroitin sulfate glycosaminoglycan epitope in human cerebral organoids, a 3D model for early central nervous system (CNS) development, immunohistochemically. In early organoids we observed distinct expression patterns of the glycoepitopes, associated with rosette-like structures that resemble the neural tube in vitro: Terminal LeX motifs, recognized by the monoclonal antibody (mAb) 487^LeX, were enriched in the lumen and at the outer border of neural rosettes. In contrast, internal LeX motif repeats detected with mAb 5750^LeX were concentrated near the lumen. The DSD-1 epitope, labeled with mAb 473HD, was detectable at rosette borders and in adjacent cells. The epitope expression was maintained in older organoids but appeared more diffuse. The differential glycoepitope expression suggests a specific function in the developing human CNS.

Protein tyrosine phosphatase receptor type Z1 inhibits the cisplatin resistance of ovarian cancer by regulating PI3K/AKT/mTOR signal pathway

Most patients with ovarian cancer (OC) get remission after undergoing cytoreductive surgery and platinum-based standard chemotherapy, but more than 50% of patients with advanced OC relapse within the first 5 years after treatment and develop resistance to standard chemotherapy. The production of medicinal properties is the main reason for the poor prognosis and high mortality of OC patients. Cisplatin (DDP) resistance is a major cause for poor prognosis of OC patients. PTPRZ1 can regulate the growth and apoptosis of ovarian cancer cells, while the molecular mechanism remains unknown. This study was designed to investigate the roles of PTPRZ1 in DDP-resistant OC cells and possible mechanism. PTPRZ1 expression in OC tissues and normal tissues was analyzed by GEPIA database and verified by Real-time Quantitative Reverse Transcription PCR (RT-PCR) assay. PTPRZ1 expression in normal ovarian cancer cells and DDP-resistant OC cells was also analyzed. Subsequently, RT-PCR, Western blot, MTT experiment and flow cytometry were used to assess the effects of PTPRZ1-PI3K/AKT/mTOR regulating axis on DDP resistance of OC. PTPRZ1 expression was abnormally low in OC tissues, and notably reduced in DDP-resistant OC cells. MTT experiment and flow cytometer indicated that overexpression of PTPRZ1 enhanced the DDP sensitivity of OC cells and promoted the cell apoptosis. Moreover, the results of our research showed that PTPRZ1 might exert its biological effects through blocking PI3K/AKT/mTOR pathway. PTPRZ1 overexpression inhibitied OC tumor growth and resistance to DDP in vivo. Overall, PTPRZ1 might suppress the DDP resistance of OC and induce the cytotoxicity by blocking PI3K/AKT/mTOR pathway.

A novel PTPRZ1-ETV1 fusion in gliomas

The aggressive nature of malignant gliomas and their genetic and clinical heterogeneity present a major challenge in their diagnosis and treatment. Development of targeted therapy brought attention on detecting novel gene fusions, since they represent promising therapeutic targets (eg, TRK inhibitors in NTRK fusion-positive tumors). Using targeted next-generation sequencing, we prospectively analyzed 205 primary brain tumors and detected a novel PTPRZ1-ETV1 fusion transcript in 11 of 191 (5.8%) gliomas, including nine glioblastomas, one anaplastic oligodendroglioma and one pilocytic astrocytoma. PTPRZ1-ETV1 fusion was confirmed by RT-PCR followed by Sanger sequencing, and in-silico analysis predicted a potential driver role. The newly detected fusion consists of the PTPRZ1 promoter in frame with the highly conserved DNA-binding domain of ETV1 transcription factor. The ETV1 and PTPRZ1 genes are known oncogenes, involved in processes of tumor development. ETV1 is a member of the ETS family of transcription factors, already known oncogenic drivers in Ewing sarcoma, prostate cancer and gastrointestinal stromal tumors, but not in gliomas. Its overexpression contributes to tumor growth and more aggressive tumor behavior. PTPRZ1 is already considered to be a tumor growth promoting oncogene in gliomas. In 8%-16% of gliomas, PTPRZ1 is fused to the MET oncogene, resulting in a PTPRZ1-MET fusion, which is associated with poorer prognosis but is also a positive predictive biomarker for treatment with kinase inhibitors. In view of the oncogenic role that the two fusion partners, PTPRZ1 and ETV1, exhibit in other malignancies, PTPRZ1-ETV1 fusion might present a novel potential therapeutic target in gliomas. Although histopathological examination of PTPRZ1-ETV1 fusion-positive gliomas did not reveal any specific or unique pathological features, and the follow-up period was too short to assess prognostic value of the fusion, careful monitoring of patients and their response to therapy might provide additional insights into the prognostic and predictive value of this novel fusion.

The Expression, Functions, Interactions and Prognostic Values of PTPRZ1: A Review and Bioinformatic Analysis

Available studies demonstrate that receptor-type tyrosine-protein phosphatase zeta (PTPRZ1) is expressed in different tumor tissues, and functions in cell proliferation, cell adhesion and migration, epithelial-to-mesenchymal transition, cancer stem cells and treatment resistance by interacting with or binding to several molecules. These included pleiotrophin (PTN), midkine, interleukin-34, β-catenin, VEGF, NF-κB, HIF-2, PSD-95, MAGI-3, contactin and ErbB4. PTPRZ1 was involved in survival signaling and could predict the prognosis of several tumors. This review discusses: the current knowledge about PTPRZ1, its expression, co-receptors, ligands, functions, signaling pathway, prognostic values and therapeutic agents that target PTPRZ1.

Development of inhibitors of receptor protein tyrosine phosphatase β/ζ (PTPRZ1) as candidates for CNS disorders

A new series of blood-brain barrier permeable molecules designed to mimic the activity of Pleiotrophin in the CNS has been designed and synthesized. These compounds exert their action by interacting with the intracellular domain PD1 of the Protein Tyrosine-Phosphatase Receptor Z1 (PTPRZ1), and inhibiting its tyrosine phosphatase activity. The most potent compounds 10a and 12b (IC₅₀ = 0,1 μM) significantly increase the phosphorylation of key tyrosine residues of PTPRZ1 substrates involved in neuronal survival and differentiation, and display protective effects against amphetamine-induced toxicity. Docking and molecular dynamics experiments have been used to analyze the binding mode and to explain the observed selectivity against PTP1B. An In vivo experiment has demonstrated that 10a can cross the BBB, thus promoting the possibility of moving forward these candidates for the development of drugs for the treatment of CNS disorders, such as drug addiction and neurodegenerative diseases.

Comprehensive protein tyrosine phosphatase mRNA profiling identifies new regulators in the progression of glioma

The infiltrative behavior of diffuse gliomas severely reduces therapeutic potential of surgical resection and radiotherapy, and urges for the identification of new drug-targets affecting glioma growth and migration. To address the potential role of protein tyrosine phosphatases (PTPs), we performed mRNA expression profiling for 91 of the 109 known human PTP genes on a series of clinical diffuse glioma samples of different grades and compared our findings with in silico knowledge from REMBRANDT and TCGA databases. Overall PTP family expression levels appeared independent of characteristic genetic aberrations associated with lower grade or high grade gliomas. Notably, seven PTP genes (DUSP26, MTMR4, PTEN, PTPRM, PTPRN2, PTPRT and PTPRZ1) were differentially expressed between grade II-III gliomas and (grade IV) glioblastomas. For DUSP26, PTEN, PTPRM and PTPRT, lower expression levels correlated with poor prognosis, and overexpression of DUSP26 or PTPRT in E98 glioblastoma cells reduced tumorigenicity. Our study represents the first in-depth analysis of PTP family expression in diffuse glioma subtypes and warrants further investigations into PTP-dependent signaling events as new entry points for improved therapy.

High PTPRQ Expression and Its Relationship to Expression of PTPRZ1 and the Presence of KRAS Mutations in Colorectal Cancer Tissues

BACKGROUND

The risk of sporadic colorectal cancer (CRC) is strongly influenced by Iifestyle, environmental and genetic factors. Protein tyrosine phosphatases belong to a group of enzymes whose role in CRC has not yet been intensively studied. They play an important role in activation/de-activation of many enzymes, influencing cell biology by catalyzing reactions opposing those catalyzed by kinases. Protein tyrosine phosphatase receptor-like type Q (PTPRQ) and protein tyrosine phosphatase receptor-like type Z polypeptide 1 (PTPRZ1) have both been shown to be important in development of many cancer types including CRC.

MATERIALS AND METHODS

The expression level of PTPRQ and PTPRZ1 was determined by real-time polymerase chain reaction in 16 CRC tissues obtained from patients diagnosed with adenocarcinoma coli.

RESULTS

We revealed a high level of PTPRQ expression (p=0.0080), as well as an association between expression levels of PTPRQ and PTPRZ1 (p<0.0001). Moreover PTPRQ expression was higher in tissues presenting with Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation (p=0.0293).

CONCLUSION

We confirmed the contribution of PTPRZ1 and especially PTPRQ in CRC development, supporting the hypothesis that PTPRQ is a candidate oncogene, playing a crucial role in phosphorylation/dephosphorylation signaling pathways.

Tailor-Made Protein Tyrosine Phosphatases: In Vitro Site-Directed Mutagenesis of PTEN and PTPRZ-B

In vitro site-directed mutagenesis (SDM) of protein tyrosine phosphatases (PTPs) is a commonly used approach to experimentally analyze PTP functions at the molecular and cellular level and to establish functional correlations with PTP alterations found in human disease. Here, using the tumor-suppressor PTEN and the receptor-type PTPRZ-B (short isoform from PTPRZ1 gene) phosphatases as examples, we provide a brief insight into the utility of specific mutations in the experimental analysis of PTP functions. We describe a standardized, rapid, and simple method of mutagenesis to perform single and multiple amino acid substitutions, as well as deletions of short nucleotide sequences, based on one-step inverse PCR and DpnI restriction enzyme treatment. This method of SDM is generally applicable to any other protein of interest.