PTPN21-CDSlong isoform inhibits the response of acute lymphoblastic leukemia cells to NK-mediated lysis via the KIR/HLA-I axis

Overexpression of PTPN21 promotes proliferation of EGF-stimulated acute lymphoblastic leukemia cells via the MAPK signaling pathways

OBJECTIVES

This study aims to investigate the role of excessive Protein Tyrosine Phosphatase Non-Receptor Type 21 (PTPN21) in the proliferation of Acute Lymphoblastic Leukemia (ALL) cells with EGF stimulation.

METHODS

PTPN21 was overexpressed in ALL cell lines by lentiviral transfection. Apoptosis was assayed by Annexin V/7-AAD staining. The proliferation and cell cycle of EGF-treated ALL cells were assessed by MTT and Ki-67/7-AAD staining respectively. The phosphorylation of Src tyrosine kinase and mediators of distinct MAPK pathways were assessed by Western blot.

RESULTS

Overexpression of PTPN21 had minimal effect on the apoptosis of ALL cells, but significantly promoted the proliferation and cell cycle progression of ALL cells stimulated with EGF. The activity of Src tyrosine kinase and the MAPK pathways was elevated. Inhibition of MAPK pathways by specific inhibitors mitigated this pro-proliferative effect of excessive PTPN21 on EGF-stimulated ALL cells.

CONCLUSION

PTPN21 may facilitate ALL progression by promoting cell proliferation via the Src/MAPK signaling pathways.

Structural analysis of PTPN21 reveals a dominant-negative effect of the FERM domain on its phosphatase activity

PTPN21 belongs to the four-point-one, ezrin, radixin, moesin (FERM) domain-containing protein tyrosine phosphatases (PTP) and plays important roles in cytoskeleton-associated cellular processes like cell adhesion, motility, and cargo transport. Because of the presence of a WPE loop instead of a WPD loop in the phosphatase domain, it is often considered to lack phosphatase activity. However, many of PTPN21's biological functions require its catalytic activity. To reconcile these findings, we have determined the structures of individual PTPN21 FERM, PTP domains, and a complex between FERM-PTP. Combined with biochemical analysis, we have found that PTPN21 PTP is weakly active and is autoinhibited by association with its FERM domain. Disruption of FERM-PTP interaction results in enhanced ERK activation. The oncogenic HPV18 E7 protein binds to PTP at the same location as PTPN21 FERM, indicating that it may act by displacing the FERM domain from PTP. Our results provide mechanistic insight into PTPN21 and benefit functional studies of PTPN21-mediated processes.

Comprehensive analysis of PTPN family expression and prognosis in acute myeloid leukemia

Background: Tyrosyl phosphorylation is carried out by a group of enzymes known as non-receptor protein tyrosine phosphatases (PTPNs). In the current investigation, it is hoped to shed light on the relationships between the expression patterns of PTPN family members and the prognosis of acute myeloid leukemia (AML). Methods: PTPN expression was examined using GEPIA and GEO databases. To investigate the connection between PTPN expression and survival in AML patients, we downloaded data from the Broad TCGA Firehose and Clinical Proteomic Tumor Analysis (CPTAC) of the Cancer Genome Atlas (TCGA). We used quantitative real-time PCR (qRT-PCR) to confirm that essential genes were performed in clinical samples and cell lines. We then used western blot to verify that the genes expressed in the above databases were positive in normal tissues, AML patient samples, and AML cell lines. Next, we investigated associations between genome-wide expression profiles and PTPN6 expression using the GEO datasets. We investigated the interactive exploration of multidimensional cancer genomics using the cBioPortal datasets. Using the DAVID database, a study of gene ontology enrichment was performed. The protein-protein interaction (PPI) network was created using the STRING portal, and the gene-gene interaction network was performed using GeneMANIA. Results: Data from GEO and GEPIA revealed that most PTPN family members were linked to AML. Patients with leukemia have elevated levels of several PTPN members. All of the AML patients' poor overall survival (OS, p < .05) was significantly linked with higher expression of PTPN1, PTPN6, and PTPN7. Additionally, clinical samples showed that the expression of PTPN 6, PTPN 7, PTPN 13, and PTPN 14 was higher than normal in AML patients (p = .0116, p = .0034, p = .0092, and p = .0057, respectively) and AML cell lines (p = .0004, p = .0035, p = .0357, and p = .0177, respectively). Western blotting results showed that the expression of PTPN6 in AML samples and AML cell lines was significantly higher than that in normal control samples. Conclusion: Differentially expressed PTPN family members were found in AML. The prognosis of patients and PTPN gene expression were shown to be correlated. PTPN6 is one of these members and may be used as an AML diagnostic and prognostic marker.

Inhibition of PTPN21 has antitumor effects in glioma by restraining the EGFR/PI3K/AKT pathway

Protein tyrosine phosphatase non-receptor type 21 (PTPN21) has been recognised as a new tumour-associated protein that is implicated in diverse tumours. However, the correlation between PTPN21 and glioma remains unaddressed. This investigation focused on the relevance of PTPN21 in glioma. The Cancer Genome Atlas (TCGA) analysis identified PTPN21 as being up-regulated in glioma tissue. The elevation of PTP21 in glioma was validated by evaluating clinical specimen. Kaplan-Meier plot analysis revealed that a high PTPN21 level predicted poor survival rate in glioma patient. Silencing of PTPN21 produced remarkable anticancer effects in glioma cells including proliferation inhibition, cell cycle arrest, metastasis suppression and enhanced chemosensitivity. Mechanistic studies uncovered that PTPN21 contributes to mediation of the phosphatidyl-inositole-3 kinase (PI3K)/AKT pathway via the regulation of epidermal growth factor receptor (EGFR). Restraint of EGFR diminished PTPN21 overexpression-induced promoting effect on PI3K/AKT pathway. Reactivation of AKT reversed PTPN21 silencing-evoked antitumor effect. The tumorigenic potential of PTPN21-silenced glioma cells in vivo was markedly compromised. In summary, this study demonstrates that silencing of PTPN21 produces remarkable anticancer effects in glioma by restraining the EGFR/PI3K/AKT pathway.