Characterization of PTPN2 and its use as a biomarker

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

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

Crosstalk between alternative splicing and inflammatory bowel disease: Basic mechanisms, biotechnological progresses and future perspectives

BACKGROUND

Alternative splicing (AS) is an omnipresent regulatory mechanism of gene expression that enables the generation of diverse splice isoforms from a single gene. Recently, AS events have gained considerable momentum in the pathogenesis of inflammatory bowel disease (IBD).

METHODS

Our review has summarized the complex process of RNA splicing, and firstly highlighted the potential involved molecules that target aberrant splicing events in IBD. The quantitative transcriptome analyses such as microarrays, next-generation sequencing (NGS) for AS events in IBD have been also discussed.

RESULTS

Available evidence suggests that some abnormal splicing RNAs can lead to multiple intestinal disorders during the onset of IBD as well as the progression to colitis-associated cancer (CAC), including gut microbiota perturbations, intestinal barrier dysfunctions, innate/adaptive immune dysregulations, pro-fibrosis activation and some other risk factors. Moreover, current data show that the advanced technologies, including microarrays and NGS, have been pioneeringly employed to screen the AS candidates and elucidate the potential regulatory mechanisms of IBD. Besides, other biotechnological progresses such as the applications of third-generation sequencing (TGS), single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics (ST), will be desired with great expectations.

CONCLUSIONS

To our knowledge, the current review is the first one to evaluate the potential regulatory mechanisms of AS events in IBD. The expanding list of aberrantly spliced genes in IBD along with the developed technologies provide us new clues to how IBD develops, and how these important AS events can be explored for future treatment.

Protein tyrosine phosphatase non-receptor type 2 as the therapeutic target of atherosclerotic diseases: past, present and future

Tyrosine-protein phosphatase non-receptor type 2(PTPN2), an important member of the protein tyrosine phosphatase family, can regulate various signaling pathways and biological processes by dephosphorylating receptor protein tyrosine kinases. Accumulating evidence has demonstrated that PTPN2 is involved in the occurrence and development of atherosclerotic cardiovascular disease. Recently, it has been reported that PTPN2 exerts an anti-atherosclerotic effect by regulating vascular endothelial injury, monocyte proliferation and migration, macrophage polarization, T cell polarization, autophagy, pyroptosis, and insulin resistance. In this review, we summarize the latest findings on the role of PTPN2 in the pathogenesis of atherosclerosis to provide a rationale for better future research and therapeutic interventions.

Macromolecular crowding amplifies allosteric regulation of T-cell protein tyrosine phosphatase

T-cell protein tyrosine phosphatase (TC-PTP) is a negative regulator of T-cell receptor and oncogenic receptor tyrosine kinase signaling and implicated in cancer and autoimmune disease. TC-PTP activity is modulated by an intrinsically disordered C-terminal region (IDR) and suppressed in cells under basal conditions. In vitro structural studies have shown that the dynamic reorganization of IDR around the catalytic domain, driven by electrostatic interactions, can lead to TC-PTP activity inhibition; however, the process has not been studied in cells. Here, by assessing a mutant (³⁷⁸KRKRPR³⁸³ mutated into ³⁷⁸EAAAPE³⁸³, called TC45^E/A) with impaired tail-PTP domain interaction, we obtained evidence that the downmodulation of TC-PTP enzymatic activity by the IDR occurs in cells. However, we found that the regulation of TC-PTP by the IDR is only recapitulated in vitro when crowding polymers that mimic the intracellular environment are present in kinetic assays using a physiological phosphopeptide. Our FRET-based assays in vitro and in cells confirmed that the effect of the mutant correlates with an impairment of the intramolecular inhibitory remodeling of TC-PTP by the IDR. This work presents an early example of the allosteric regulation of a protein tyrosine phosphatase being controlled by the cellular environment and provides a framework for future studies and targeting of TC-PTP function.

Common polymorphisms of protein tyrosine phosphate non-receptor type 2 gene are not associated with risk of Crohn’s disease in Indian

BACKGROUND

Multiple genetic risk factors for Crohn’s disease (CD) have been identified. However, these observations are not consistent across different populations. The protein tyrosine phosphate non-receptor type 2 (PTPN2) gene plays a role in various aspects of host defense including epithelial barrier function, autophagy, and innate and adaptive immune response. Two common polymorphisms in the PTPN2 gene (rs2542151 and rs7234029) have been associated with risk of CD in Western countries.

AIM

To evaluate the association of PTPN2 gene polymorphisms with risk of CD in Indian population.

METHODS

We conducted a prospective case-control study. Patients with CD were recruited, and their clinical and investigation details were noted. Controls were patients without organic gastrointestinal disease or other comorbid illnesses. Two common polymorphisms in the PTPN2 gene (rs2542151 and rs7234029) were assessed. DNA was extracted from peripheral blood samples of cases and controls and target DNA was amplified using specific sets of primers. The amplified fragments were digested with restriction enzymes and the presence of polymorphism was detected by restriction fragment length polymorphism. The frequency of alleles was determined. The frequencies of genotypes and alleles were compared between cases and controls to look for significant differences.

RESULTS

A total of 108 patients with CD (mean age 37.5 ± 12.7 years, females 42.6%) and 100 controls (mean age 39.9 ± 13.5 years, females 37%) were recruited. For the single nucleotide polymorphism (SNP) rs7234029, the overall frequency of G variant genotype (AG or GG) was noted to be significantly lower in the cases compared to controls (35.2% vs 50%, P = 0.05). For the SNP rs2542151, the overall frequency of G variant genotype (GT or GG) was noted to be similar in cases compared to controls (43.6% vs 47%, P = 0.73). There were no significant differences in minor allele (G) frequency for both polymorphisms between the cases and controls. Both the SNPs had no significant association with age of onset of illness, gender, disease location, disease behaviour, perianal disease, or extraintestinal manifestations of CD.

CONCLUSION

Unlike observation form the West, polymorphisms in the PTPN2 gene (rs7234029 and rs2542151) are not associated with an increased risk of developing CD in Indian patients.

PTPN2 elicits cell autonomous and non-cell autonomous effects on antitumor immunity in triple-negative breast cancer

The tumor-suppressor PTPN2 is diminished in a subset of triple-negative breast cancers (TNBCs). Paradoxically, PTPN2-deficiency in tumors or T cells in mice can facilitate T cell recruitment and/or activation to promote antitumor immunity. Here, we explored the therapeutic potential of targeting PTPN2 in tumor cells and T cells. PTPN2-deficiency in TNBC associated with T cell infiltrates and PD-L1 expression, whereas low PTPN2 associated with improved survival. PTPN2 deletion in murine mammary epithelial cells TNBC models, did not promote tumorigenicity but increased STAT-1-dependent T cell recruitment and PD-L1 expression to repress tumor growth and enhance the efficacy of anti-PD-1. Furthermore, the combined deletion of PTPN2 in tumors and T cells facilitated T cell recruitment and activation and further repressed tumor growth or ablated tumors already predominated by exhausted T cells. Thus, PTPN2-targeting in tumors and/or T cells facilitates T cell recruitment and/or alleviates inhibitory constraints on T cells to combat TNBC.

T Cell Protein Tyrosine Phosphatase in Glucose Metabolism

T cell protein tyrosine phosphatase (TCPTP), a vital regulator in glucose metabolism, inflammatory responses, and tumor processes, is increasingly considered a promising target for disease treatments and illness control. This review discusses the structure, substrates and main biological functions of TCPTP, as well as its regulatory effect in glucose metabolism, as an attempt to be referenced for formulating treatment strategies of metabolic disorders. Given the complicated regulation functions in different tissues and organs of TCPTP, the development of drugs inhibiting TCPTP with a higher specificity and a better biocompatibility is recognized as a promising therapeutic strategy for diabetes or obesity. Besides, treatments targeting TCPTP in a specific tissue or organ are suggested to be considerably promising.

T Cell Protein Tyrosine Phosphatase in Osteoimmunology

Osteoimmunology highlights the two-way communication between bone and immune cells. T cell protein tyrosine phosphatase (TCPTP), also known as protein-tyrosine phosphatase non-receptor 2 (PTPN2), is an intracellular protein tyrosine phosphatase (PTP) essential in regulating immune responses and bone metabolism via dephosphorylating target proteins. Tcptp knockout in systemic or specific immune cells can seriously damage the immune function, resulting in bone metabolism disorders. This review provided fresh insights into the potential role of TCPTP in osteoimmunology. Overall, the regulation of osteoimmunology by TCPTP is extremely complicated. TCPTP negatively regulates macrophages activation and inflammatory factors secretion to inhibit bone resorption. TCPTP regulates T lymphocytes differentiation and T lymphocytes-related cytokines signaling to maintain bone homeostasis. TCPTP is also expected to regulate bone metabolism by targeting B lymphocytes under certain time and conditions. This review offers a comprehensive update on the roles of TCPTP in osteoimmunology, which can be a promising target for the prevention and treatment of inflammatory bone loss.

Deletion of Protein Tyrosine Phosphatase Nonreceptor Type 2 in Intestinal Epithelial Cells Results in Upregulation of the Related Phosphatase Protein Tyrosine Phosphatase Nonreceptor Type 23

Background/Aims

Knockdown of protein tyrosine phosphatase nonreceptor type 2 (PTPN2) exaggerates IFN-γ-induced intestinal barrier defects, but mice constitutively lacking PTPN2 in epithelial cells (PTPN2xVilCre mice) do not show changes in epithelial function or enhanced susceptibility to experimental colitis. Here, we investigated whether PTPN2 modulates the expression of related tyrosine phosphatases.

Methods

PTPN2 knockdown in HT-29 cells was induced using siRNA constructs. Acute colitis in PTPN2xVilCre mice was induced by 2% dextran sulfate sodium (DSS) in drinking water for 7 days. Colitis-associated tumors were induced by injection of azoxymethane prior to treatment with DSS for 3 consecutive cycles.

Results

In HT-29 cells, PTPN2 depletion resulted in enhanced mRNA expression of PTPN11 and PTPN23 and in parallel to upregulation of IL-18 mRNA upon treatment with TNF for 24 h. DSS treatment of PTPN2-deficient mice resulted in a strong induction of Ptpn23 mRNA in colon tissue in vivo. In the tumor model, Ptpn23 mRNA was again clearly upregulated in nontumor tissue from PTPN2-deficient mice; however, this was not observed in tumor tissue.

Conclusions

Our experiments show that PTPN23 function might, at least partially, compensate lack of PTPN2 in epithelial cells. Upregulation of PTPN23 might therefore crucially contribute to the lack of a colitis phenotype in PTPN2-VilCre mice.

The effects of PTPN2 loss on cell signalling and clinical outcome in relation to breast cancer subtype

Purpose

The protein tyrosine phosphatase PTPN2 dephosphorylates several tyrosine kinases in cancer-related signalling pathways and is thought to be a tumour suppressor. As PTPN2 is not frequently studied in breast cancer, we aimed to explore the role of PTPN2 and the effects of its loss in breast cancer.

Methods

Protein expression and gene copy number of PTPN2 were analysed in a cohort of pre-menopausal breast cancer patients with immunohistochemistry and droplet digital PCR, respectively. PTPN2 was knocked down in three cell lines, representing different breast cancer subtypes, with siRNA transfection. Several proteins related to PTPN2 were analysed with Western blot.

Results

Low PTPN2 protein expression was found in 50.2% of the tumours (110/219), gene copy loss in 15.4% (33/214). Low protein expression was associated with a higher relapse rate in patients with Luminal A and HER2-positive tumours, but not triple-negative tumours. In vitro studies further suggested a subtype-specific role of PTPN2. Knockdown of PTPN2 had no effect on the triple-negative cell line, whilst knockdown in MCF7 inhibited phosphorylation of Met and promoted that of Akt. Knockdown in SKBR3 led to increased Met phosphorylation and decreased Erk phosphorylation as well as EGF-mediated STAT3 activation.

Conclusion

We confirm previous studies showing that the PTPN2 protein is lost in half of the breast cancer cases and gene deletion occurs in 15–18% of the cases. Furthermore, the results suggest that the role of PTPN2 is subtype-related and should be further investigated to assess how this could affect breast cancer prognosis and treatment response.

PTPN2 deficiency along with activation of nuclear Akt predict endocrine resistance in breast cancer

Purpose

The protein tyrosine phosphatase, non-receptor type 2 (PTNP2) regulates receptor tyrosine kinase signalling, preventing downstream activation of intracellular pathways like the PI3K/Akt pathway. The gene encoding the protein is located on chromosome 18p11; the 18p region is commonly deleted in breast cancer. In this study, we aimed to evaluate PTPN2 protein expression in a large breast cancer cohort, its possible associations to PTPN2 gene copy loss, Akt activation, and the potential use as a clinical marker in breast cancer.

Methods

PTPN2 protein expression was analysed by immunohistochemistry in 664 node-negative breast tumours from patients enrolled in a randomised tamoxifen trial. DNA was available for 146 patients, PTPN2 gene copy number was determined by real-time PCR.

Results

PTPN2 gene loss was detected in 17.8% of the tumours. Low PTPN2 protein expression was associated with higher levels of nuclear-activated Akt (pAkt-n). Low PTPN2 as well as the combination variable low PTPN2/high pAkt-n could be used as predictive markers of poor tamoxifen response.

Conclusion

PTPN2 negatively regulates Akt signalling and loss of PTPN2 protein along with increased pAkt-n is a new potential clinical marker of endocrine treatment efficacy, which may allow for further tailored patient therapies.

When one becomes many-Alternative splicing in β-cell function and failure

Pancreatic β-cell dysfunction and death are determinant events in type 1 diabetes (T1D), but the molecular mechanisms behind β-cell fate remain poorly understood. Alternative splicing is a post-transcriptional mechanism by which a single gene generates different mRNA and protein isoforms, expanding the transcriptome complexity and enhancing protein diversity. Neuron-specific and certain serine/arginine-rich RNA binding proteins (RBP) are enriched in β-cells, playing crucial roles in the regulation of insulin secretion and β-cell survival. Moreover, alternative exon networks, regulated by inflammation or diabetes susceptibility genes, control key pathways and processes for the correct function and survival of β-cells. The challenge ahead of us is to understand the precise role of alternative splicing regulators and splice variants on β-cell function, dysfunction and death and develop tools to modulate it.

25-Hydroxyvitamin D3 -enhanced PTPN2 positively regulates periodontal inflammation through the JAK/STAT pathway in human oral keratinocytes and a mouse model of type 2 diabetes mellitus

BACKGROUND AND OBJECTIVE

Periodontitis is an increasingly prevalent complication of diabetes mellitus (known as diabetes mellitus-associated periodontitis), and 25-hydroxyvitamin D₃ (25VD₃ ) was recently found to be a critical regulator of innate immunity in this disease, but the underlying mechanisms remain poorly understood. T-cell protein tyrosine phosphatase non-receptor type 2 (PTPN2) is a potential downstream protein of the 25VD₃ /vitamin D receptor pathway. The aim of this study was to investigate the regulation of PTPN2 in periodontal inflammation in diabetes mellitus-associated periodontitis.

MATERIAL AND METHODS

Porphyromonas gingivalis-infected db/db mice were treated with 25VD₃ . Their fasting blood glucose and body weight were monitored every other week, and the levels of alveolar bone loss and serum inflammatory cytokines (tumor necrosis factor-α, interferon-γ and interleukin-6) were determined at the time of killing. The effect of PTPN2 on human OKF6-TERT2 oral keratinocytes was examined through the knockout of PTPN2 using the CRISPR/Cas9 knockout plasmid. The expression levels of the PTPN2, vitamin D receptor and JAK1/STAT3 signaling proteins in the gingival epithelium and OKF6-TERT2 cells were determined through western blot and immunohistochemical analyses.

RESULTS

After 25VD₃ treatment, db/db mice exhibited alleviated serum inflammatory cytokines and alveolar bone loss, and 25VD₃ -enhanced PTPN2 expression decreased the expression of the JAK1/STAT3 signaling proteins in the gingival epithelium. Analyses of human oral keratinocytes showed that 25VD₃ increased the expression of PTPN2, which dephosphorylates protein substrates in the JAK1/STAT3 signaling pathway.

CONCLUSION

PTPN2 contributed to a decrease in periodontal inflammation in type 2 diabetes mellitus via dephosphorylate protein substrates in the JAK1/STAT3 signaling pathway after 25VD₃ treatment in human oral keratinocytes and a mouse model of type 2 diabetes mellitus. A thorough understanding of PTPN2 and its involvement in inhibiting inflammation might provide alternative therapeutic approaches for the pathogenesis and treatment of diabetes mellitus-associated periodontitis.

Protein tyrosine phosphatase nonreceptor type 2: an important regulator of lnterleukin-6 production in rheumatoid arthritis synovial fibroblasts

OBJECTIVE

To investigate the role of protein tyrosine phosphatase nonreceptor type 2 (PTPN2) in the pathogenesis of rheumatoid arthritis (RA).

METHODS

Synovial tissue samples from patients with RA and patients with osteoarthritis (OA) were stained for PTPN2. Synovial fibroblasts were stimulated with tumor necrosis factor (TNF) and interleukin-1β (IL-1β), lipopolysaccharide (LPS), TRAIL, or thapsigargin. The expression of PTPN2 in synovial fibroblasts and peripheral blood mononuclear cells (PBMCs) was analyzed by real-time polymerase chain reaction and Western blotting. Cell death, the release of IL-6 and IL-8, and the induction of autophagy were analyzed after PTPN2 silencing. Methylated DNA immunoprecipitation analysis was used to evaluate DNA methylation-regulated gene expression of PTPN2.

RESULTS

PTPN2 was significantly overexpressed in synovial tissue samples from RA patients compared to OA patients. Patients receiving anti-TNF therapy showed significantly reduced staining for PTPN2 compared with patients treated with nonbiologic agents. PTPN2 expression was higher in RA synovial fibroblasts (RASFs) than in OASFs. This differential expression was not regulated by DNA methylation. PTPN2 was further up-regulated after stimulation with TNF, TNF combined with IL-1β, or LPS. There was no significant difference in basal PTPN2 expression in PBMCs from patients with RA, ankylosing spondylitis, or systemic lupus erythematosus or healthy controls. Most interestingly, PTPN2 silencing in RASFs significantly increased the production of the inflammatory cytokine IL-6 but did not affect levels of IL-8. Moreover, functional analysis showed that high PTPN2 levels contributed to the increased apoptosis resistance of RASFs and increased autophagy.

CONCLUSION

This is the first study of PTPN2 in RASFs showing that PTPN2 regulates IL-6 production, cell death, and autophagy. Our findings indicate that PTPN2 is linked to the pathogenesis of RA via synovial fibroblasts.

TC-PTP and PTP1B: Regulating JAK-STAT signaling, controlling lymphoid malignancies

Lymphoid malignancies are characterized by an accumulation of genetic lesions that act co-operatively to perturb signaling pathways and alter gene expression programs. The Janus kinases (JAK)-signal transducers and activators of transcription (STATs) pathway is one such pathway that is frequently mutated in leukemia and lymphoma. In response to cytokines and growth factors, a cascade of reversible tyrosine phosphorylation events propagates the JAK-STAT pathway from the cell surface to the nucleus. Activated STAT family members then play a fundamental role in establishing the transcriptional landscape of the cell. In leukemia and lymphoma, somatic mutations have been identified in JAK and STAT family members, as well as, negative regulators of the pathway. Most recently, inactivating mutations in the protein tyrosine phosphatase (PTP) genes PTPN1 (PTP1B) and PTPN2 (TC-PTP) were sequenced in B cell lymphoma and T cell acute lymphoblastic leukemia (T-ALL) respectively. The loss of PTP1B and TC-PTP phosphatase activity is associated with an increase in cytokine sensitivity, elevated JAK-STAT signaling, and changes in gene expression. As inactivation mutations in PTPN1 and PTPN2 are restricted to distinct subsets of leukemia and lymphoma, a future challenge will be to identify in which cellular contexts do they contributing to the initiation or maintenance of leukemogenesis or lymphomagenesis. As well, the molecular mechanisms by which PTP1B and TC-PTP loss co-operates with other genetic aberrations will need to be elucidated to design more effective therapeutic strategies.

Comparison of Experimental Diabetic Periodontitis Induced by Porphyromonas gingivalis in Mice

Periodontitis is one of the severe complications in diabetic patients and gingival epithelium plays an initial role on the onset and progression of this disease. However the potential mechanism is yet sufficiently understood. Meanwhile, the research on the correlational experimental animal models was also insufficient. Here, we established periodontitis with type 2 diabetes in db/db and Tallyho/JngJ (TH) mice and periodontitis with type 1 diabetes in streptozotocin induced diabetes C57BL/6J (STZ-C57) mice by oral infection of periodontal pathogen Porphyromonas gingivalis W50. We demonstrated that periodontal infected mice with high blood glucose levels showed dramatically more alveolar bone loss than their counterparts, in which infected db/db mice exhibited the most bone defects. No contrary impact could be observed between this periodontal infection and onset and severity of diabetes. The expressions of PTPN2 were inhibited whereas the expression of JAK1, STAT1, and STAT3 increased dramatically in gingival epithelia and the serum TNF-α also significantly increased in the mice with diabetic periodontitis. Our results indicated that the variations of inflammation-related protein expressions in gingival epithelia might lead to the phenotype differences in the mice with diabetic periodontitis.

Loss of protein tyrosine phosphatase, non-receptor type 2 is associated with activation of AKT and tamoxifen resistance in breast cancer

Breast cancer is a heterogeneous disease and new clinical markers are needed to individualise disease management and therapy further. Alterations in the PI3K/AKT pathway, mainly PIK3CA mutations, have been shown frequently especially in the luminal breast cancer subtypes, suggesting a cross-talk between ER and PI3K/AKT. Aberrant PI3K/AKT signalling has been connected to poor response to anti-oestrogen therapies. In vitro studies have shown protein tyrosine phosphatase, non-receptor type 2 (PTPN2) as a previously unknown negative regulator of the PI3K/AKT pathway. Here, we evaluate possible genomic alterations in the PTPN2 gene and its potential as a new prognostic and treatment predictive marker for endocrine therapy benefit in breast cancer. PTPN2 gene copy number was assessed by real-time PCR in 215 tumour samples from a treatment randomised study consisting of postmenopausal patients diagnosed with stage II breast cancer 1976-1990. Corresponding mRNA expression levels of PTPN2 were evaluated in 86 available samples by the same methodology. Gene copy loss of PTPN2 was detected in 16% (34/215) of the tumours and this was significantly correlated with lower levels of PTPN2 mRNA. PTPN2 gene loss and lower mRNA levels were associated with activation of AKT and a poor prognosis. Furthermore, PTPN2 gene loss was a significant predictive marker of poor benefit from tamoxifen treatment. In conclusion, genomic loss of PTPN2 may be a previously unknown mechanism of PI3K/AKT upregulation in breast cancer. PTPN2 status is a potential new clinical marker of endocrine treatment benefit which could guide further individualised therapies in breast cancer.