High expression of PTPN21 in B-cell non-Hodgkin's gastric lymphoma, a positive mediator of STAT5 activity

PTPN21 inhibits cell apoptosis of acute lymphoblastic leukemia induced by chemotherapeutic agents via GADD45A and JNK signaling pathway

Acute lymphoblastic leukemia (ALL), a hematologic malignancy characterized by the uncontrolled proliferation of immature lymphocytes, often results in unfavorable long-term survival prospects for patients. PTPN21, a protein with established roles in oncogenesis, has been implicated in the pathogenesis of ALL. This study explores the role of PTPN21 in ALL cell apoptosis induced by chemotherapeutic agents. Key findings reveal that elevated PTPN21 levels hinder the apoptosis of ALL cells in response to vincristine (VCR) and daunorubicin (DNR). PTPN21 accomplishes this by inhibiting the GADD45A and JNK signaling pathways, thereby reversing cell cycle arrest in the G2/M phase. Restoring GADD45A reverses the anti-apoptotic effect of PTPN21. These findings suggest that targeting PTPN21 in conjunction with chemotherapy may represent a novel therapeutic strategy for ALL, offering potential implications for improving treatment efficacy and overcoming drug resistance.

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 the FERM domain of human protein tyrosine phosphatase non-receptor type 21

Protein tyrosine phosphatase non-receptor type 21 (PTPN21) is a cytosolic protein tyrosine phosphatase that regulates cell growth and invasion. Due to its oncogenic properties, PTPN21 has recently emerged as a potential therapeutic target for cancer. In this study, the three-dimensional structure of the PTPN21 FERM domain was determined at 2.1 Å resolution by X-ray crystallography. The crystal structure showed that this domain harbors canonical FERM folding and consists of three subdomains that are tightly packed via highly conserved intramolecular hydrophobic interactions. Consistent with this, the PTPN21 FERM domain shares high structural homology with several other FERM domains. Moreover, structural superimposition demonstrated two putative protein-binding sites of the PTPN21 FERM domain, which are presumed to be associated with interaction with its binding partner, kinesin family member 1C. Thus, these data suggest that the FERM domain of PTPN21 serves as a module that mediates protein-protein interaction, like other FERM domains.

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.

Prognostic value and immunological role of PTPN21 in pan-cancer analysis

Introduction

At present, cancer remains a persistent public health challenge facing the whole world. Studies have found that PTPN21 is associated with the development of cancer. However, the prognostic potential of PTPN21 in pan-cancer remains unclear. In this work, we aimed to analyze the expression and prognostic value of PTPN21 in pan-cancer and to further study the relationship between PTPN21 and immune infiltration.

Material and methods

TCGA and GEO data were used for expression and survival analysis. Genetic alterations in PTPN21 from TCGA cancer were studied in cBioPortal. TIMER2 was used to evaluate the correlation between PTPN21 expression and immune infiltration. The R packages "ggplot2" and "clusterProfiler" were used for GO and KEGG analysis.

Results

PTPN21 was found to be a valuable diagnostic biomarker in multiple cancers, including bladder urothelial carcinoma (BLCA), kidney renal clear cell carcinoma (KIRC), kidney renal papillary cell carcinoma (KIRP), and lung squamous cell carcinoma (LUSC). In addition, we observed that PTPN21 expression was associated with a variety of tumor mutations. Our results indicated a correlation between PTPN21 expression and immune infiltration. Enrichment analysis showed that PTPN21 was mainly involved in the regulation of neuroactive ligand-receptor interaction.

Conclusions

Our study showed that PTPN21 expression is associated with clinical prognosis, mutation, and immune infiltration of tumors. PTPN21 may be a potential biomarker for many cancers, especially in KIRC.

PTPN14 promotes gastric cancer progression by PI3KA/AKT/mTOR pathway

Gastric cancer is a high molecular heterogeneous disease with a poor prognosis. Although gastric cancer is a hot area of medical research, the mechanism of gastric cancer occurrence and development is still unclear. New strategies for treating gastric cancer need to be further explored. Protein tyrosine phosphatases play vital roles in cancer. A growing stream of studies shows that strategies or inhibitors targeting protein tyrosine phosphatases have been developed. PTPN14 belongs to the protein tyrosine phosphatase subfamily. As an inert phosphatase, PTPN14 has very poor activity and mainly functions as a binding protein through its FERM (four-point-one, ezrin, radixin, and moesin) domain or PPxY motif. The online database indicated that PTPN14 may be a poor prognostic factor for gastric cancer. However, the function and underlying mechanism of PTPN14 in gastric cancer remain unclear. We collected gastric cancer tissues and detected the expression of PTPN14. We found that PTPN14 was elevated in gastric cancer. Further correlation analysis indicated that PTPN14 was relevant with the T stage and cTNM (clinical tumor node metastasis classification) stage. The survival curve analysis showed that gastric cancer patients with higher PTPN14 expression had a shorter survival time. In addition, we illustrated that CEBP/β (CCAAT enhanced binding protein beta) could transcriptionally activate PTPN14 expression in gastric cancer. The highly expressed PTPN14 combined with NFkB (nuclear factor Kappa B) through its FERM domain and accelerated NFkB nucleus translocation. Then, NFkB promoted the transcription of PI3KA and initiated the PI3KA/AKT/mTOR pathway to promote gastric cancer cell proliferation, migration, and invasion. Finally, we established mice models to validate the function and the molecular mechanism of PTPN14 in gastric cancer. In summary, our results illustrated the function of PTPN14 in gastric cancer and demonstrated the potential mechanisms. Our findings provide a theoretical basis to better understand the occurrence and development of gastric cancer.

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.

Molecular Analysis of the Interaction between Human PTPN21 and the Oncoprotein E7 from Human Papillomavirus Genotype 18

Human papillomaviruses (HPVs) cause cellular hyperproliferation-associated abnormalities including cervical cancer. The HPV genome encodes two major viral oncoproteins, E6 and E7, which recruit various host proteins by direct interaction for proteasomal degradation. Recently, we reported the structure of HPV18 E7 conserved region 3 (CR3) bound to the protein tyrosine phosphatase (PTP) domain of PTPN14, a well-defined tumor suppressor, and found that this intermolecular interaction plays a key role in E7-driven transformation and tumorigenesis. In this study, we carried out a molecular analysis of the interaction between CR3 of HPV18 E7 and the PTP domain of PTPN21, a PTP protein that shares high sequence homology with PTPN14 but is putatively oncogenic rather than tumor-suppressive. Through the combined use of biochemical tools, we verified that HPV18 E7 and PTPN21 form a 2:2 complex, with a dissociation constant of 5 nM and a nearly identical binding manner with the HPV18 E7 and PTPN14 complex. Nevertheless, despite the structural similarities, the biological consequences of the E7 interaction were found to differ between the two PTP proteins. Unlike PTPN14, PTPN21 did not appear to be subjected to proteasomal degradation in HPV18-positive HeLa cervical cancer cells. Moreover, knockdown of PTPN21 led to retardation of the migration/invasion of HeLa cells and HPV18 E7-expressing HaCaT keratinocytes, which reflects its protumor activity. In conclusion, the associations of the viral oncoprotein E7 with PTPN14 and PTPN21 are similar at the molecular level but play different physiological roles.

Integration of transcriptome and cistrome analysis identifies RUNX1-target genes involved in pancreatic cancer proliferation

The extremely high proliferation rate of tumor cells contributes to pancreatic cancer (PC) progression. Runt-related transcription factor 1(RUNX1), a key factor in hematopoiesis that was correlated with tumor progression. However, the role of RUNX1 in PC proliferation was still unclear. We found that RUNX1 was significantly upregulated in PC tissues and its expression was negatively associated with prognosis of PC patients in a multicenter analysis according to immunohistochemical (IHC). RUNX1 downregulation in PC resulted in a significantly reduced cell proliferation rate, which was consistent with in vivo subcutaneous tumor formation assay results. RNA-seq and ChIP-seq results revealed that a portion of target genes, including HAP1, GPRC5B, PTPN21, VHL and EN2, were regulated by RUNX1, a finding successfully validated by ChIP-qPCR, qRT-PCR and Western blot. Subsequently, IHC and proliferation assays showed these target genes to be dysregulated in PC, affecting tumor growth. Our data suggest that RUNX1 plays an oncogenic role in tumor proliferation and is a potential prognostic biomarker and therapeutic target for PC.

The expression patterns and the diagnostic/prognostic roles of PTPN family members in digestive tract cancers

Background

Non-receptor protein tyrosine phosphatases (PTPNs) are a set of enzymes involved in the tyrosyl phosphorylation. The present study intended to clarify the associations between the expression patterns of PTPN family members, and diagnosis as well as the prognosis of digestive tract cancers.

Methods

Oncomine and Ualcan were used to analyze PTPN expressions. Data from The Cancer Genome Atlas (TCGA) were downloaded through UCSC Xena for validation and to explore the relationship of the PTPN expression with diagnosis, clinicopathological parameters and survival of digestive tract cancers. Gene ontology enrichment analysis was conducted using the DAVID database. The gene–gene interaction network was performed by GeneMANIA and the protein–protein interaction (PPI) network was built using STRING portal coupled with Cytoscape. The expression of differentially expressed PTPNs in cancer cell lines were explored using CCLE. Moreover, by histological verification, the expression of four PTPNs in digestive tract cancers were further analyzed.

Results

Most PTPN family members were associated with digestive tract cancers according to Oncomine, Ualcan and TCGA data. Several PTPN members were differentially expressed in digestive tract cancers. For esophageal carcinoma (ESCA), PTPN1 and PTPN12 levels were correlated with incidence; PTPN20 was associated with poor prognosis. For stomach adenocarcinoma (STAD), PTPN2 and PTPN12 levels were correlated with incidence; PTPN3, PTPN5, PTPN7, PTPN11, PTPN13, PTPN14, PTPN18 and PTPN23 were correlated with pathological grade; PTPN20 expression was related with both TNM stage and N stage; PTPN22 was associated with T stage and pathological grade; decreased expression of PTPN5 and PTPN13 implied worse overall survival of STAD, while elevated PTPN6 expression indicated better prognosis. For colorectal cancer (CRC), PTPN2, PTPN21 and PTPN22 levels were correlated with incidence; expression of PTPN5, PTPN12, and PTPN14 was correlated with TNM stage and N stage; high PTPN5 or PTPN7 expression was associated with increased hazards of death. CCLE analyses showed that in esophagus cancer cell lines, PTPN1, PTPN4 and PTPN12 were highly expressed; in gastric cancer cell lines, PTPN2 and PTPN12 were highly expressed; in colorectal cancer cell lines, PTPN12 was highly expressed while PTPN22 was downregulated. Results of histological verification experiment showed differential expressions of PTPN22 in CRC, and PTPN12 in GC and CRC.

Conclusions

Members of PTPN family were differentially expressed in digestive tract cancers. Correlations were found between PTPN genes and clinicopathological parameters of patients. Expression of PTPN12 was upregulated in both STAD and CRC, and thus could be used as a diagnostic biomarker. Differential expression of PTPN12 in GC and CRC, and PTPN22 in CRC were presented in our histological verification experiment.

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

Protein tyrosine phosphatase non-receptor type 21 (PTPN21) is a member of the non-receptor tyrosine phosphatase family. We have found that PTPN21 is mutated in relapsed Philadelphia chromosome-negative acute lymphoblastic leukemia (ALL) after allogeneic hematopoietic stem cell transplantation. PTPN21 consists of three types of isoforms according to the length of the protein encoded. However, the roles of different isoforms in leukemic cells have not been elucidated. In the study, PTPN21 isoform constitution in five ALL cell lines were identified by transcriptome polymerase chain reaction combined with Sanger sequencing, and the relationship between PTPN21 isoforms and sensitivity to natural killer (NK) cells mediated killing in ALL cell lines were further assessed by knock-out of different isoforms of PTPN21 using CRISPR-Cas9 technique. Subsequently, we explored the functional mechanisms through RNA sequencing and confirmatory testing. The results showed that there was no significant change when all PTPN21 isoforms were knocked out in ALL cells, but the sensitivity of NALM6 cells with PTPN21-CDS_long knock-out (NALM6-PTPN21_lk ) to NK-mediated killing was significantly increased. Whole transcriptome sequencing and further validation testing showed that human leukocyte antigen class I (HLA-I) molecules were significantly decreased, accompanied by a significantly downregulated expression of antigen presenting-related chaperones in NALM6-PTPN21_lk cells. Our results uncovered a previously unknown mechanism that PTPN21-CDS_long and CDS_short isoforms may play opposite roles in NK-mediated killing in ALL cells, and showed that the endogenous PTPN21-CDS_long isoform inhibited ALL cells to NK cell-mediated lysis by regulating the KIR-HLA-I axis.