Inhibition of PTPN3 Expressed in Activated Lymphocytes Enhances the Antitumor Effects of Anti-PD-1 Therapy in Head and Neck Cancer, Especially in Hypoxic Environments.

In the tumor microenvironment, wherein cytotoxic lymphocytes interact with cancer cells, lymphocyte exhaustion, an immune checkpoint inhibitor target, is promoted. However, the efficacy of these inhibitors is limited, and improving response rates remains challenging. We previously reported that protein tyrosine phosphatase nonreceptor type (PTPN) 3 is a potential immune checkpoint molecule for activated lymphocytes and that PTPN3 inhibition should be a focus area for cancer immunotherapy development. Therefore, in this study, we focused on PTPN3-suppressive therapy in terms of lymphocyte exhaustion under hypoxic conditions, which are a cancer microenvironment, and investigated measures for improving the response to anti-programmed death receptor (PD)-1 antibody drugs. We found that PTPN3 expression was upregulated in activated lymphocytes under hypoxic conditions, similar to the findings for other immune checkpoint molecules, such as PD-1, T cell immunoglobulin mucin-3, and lymphocyte-activation gene-3; furthermore, it functioned as a lymphocyte exhaustion marker. In addition, PTPN3-suppressed activated lymphocytes promoted the mammalian target of rapamycin (mTOR)-Akt signaling pathway activation and enhanced proliferation, migration, and cytotoxic activities under hypoxic conditions. Furthermore, PTPN3 suppression in activated lymphocytes increased PD-1 expression and enhanced the antitumor effects of anti-PD-1 antibody drugs against head and neck cancer in vitro and in vivo. These results suggest that the suppression of PTPN3 expression in activated lymphocytes enhances the therapeutic effect of anti-PD-1 antibody drugs in head and neck cancer, especially under hypoxic conditions that cause lymphocyte exhaustion.

Identification and verification of PTPN3 as a novel biomarker in predicting cancer prognosis, immunity, and immunotherapeutic efficacy.

BACKGROUND: The importance of protein tyrosine phosphatase non-receptor type 3 (PTPN3) in controlling multifaceted tumor cell behaviors throughout cancer development has received widespread attention. Nevertheless, little is known about the biological roles of PTPN3 in drug sensitivity, immunotherapeutic effectiveness, tumor immune microenvironment, and cancer prognosis. METHODS: The Cancer Genome Atlas (TCGA) database's RNAseq data were used to examine the expression of PTPN3 in 33 different cancer types. In addition, immunohistochemistry (IHC) was performed to validate the expression of PTPN3 across various cancer types within our clinical cohorts. The features of PTPN3 alterations were demonstrated throughout the cBioPortal database. This study focused on examining the prognostic and clinicopathological importance of PTPN3 through the acquisition of clinical data from the TCGA database. The investigation of PTPN3's probable role in the tumor immune microenvironment was demonstrated by the application of CIBERSORT, ESTIMATE algorithms, and the TISIDB database. Using Spearman's rank correlation coefficient, the relationships between PTPN3 expression and tumor mutation burden (TMB) and microsatellite instability (MSI) were evaluated. To further investigate the putative biological activities and downstream pathways of PTPN3 in various cancers in humans, Gene Set Enrichment Analysis (GSEA) was carried out. In addition, an examination was conducted to explore the associations between PTPN3 and the effectiveness of PD-1/PD-L1 inhibitors, utilizing data extracted from the GEO database. RESULTS: PTPN3 was abnormally expressed in multiple cancer types and was also strictly associated with the prognosis of cancer patients. IHC was used to investigate and confirm the various expression levels of PTPN3 in various malignancies, including breast cancer, lung cancer, sarcoma, and kidney renal clear cell carcinoma in our clinical cohorts. There is a high correlation between the levels of PTPN3 expression in different cancers and infiltrating immune cells, including mast cells, B cells, regulatory T cells, CD8 + T cells, macrophages, and dendritic cells. Infiltrating immune cells, such as regulatory T cells, CD8 + T cells, macrophages, B cells, dendritic cells, and mast cells, are strongly correlated with PTPN3 expression levels in various tumors. The expression of PTPN3 exhibited a substantial correlation with many immune-related biomolecules and the expression of TMB and MSI in multiple types of cancer. In addition, PTPN3 has demonstrated promise in predicting the therapeutic benefits of PD-1/PD-L1 inhibitors and the susceptibility to anti-cancer medications in the treatment of clinical cancer. CONCLUSIONS: Our findings highlight the importance of PTPN3 as a prognostic biomarker and predictor of immunotherapy success in various forms of cancer. Furthermore, PTPN3 appears to have an important role in modifying the tumor immune microenvironment, highlighting its potential as a promising biomarker for prognosis prediction, immunotherapeutic efficacy evaluation, and identification of immune-related characteristics in diverse cancer types.

PTPN3 inhibition contributes to the activation of the dendritic cell function to be a promising new immunotherapy target.

PURPOSE: In a previous study, protein tyrosine phosphatase non-receptor type (PTPN) 3 was identified as an immune checkpoint molecule in lymphocytes, and its potential as a novel target for cancer immunotherapy was anticipated. However, evaluation of dendritic cell (DC) function as antigen-presenting cells is critical for the development of immunotherapy. In this study, we aimed to analyze the biological effect of PTPN3 on DCs induced from human peripheral blood monocytes obtained from healthy individuals. METHODS: We used short-interfering RNA to knock down PTP3 in DCs. For DC maturation, we added cancer cell lysate and tumor necrosis factor-α/interferon-α to immature DCs. In the cytotoxic assay, the target cancer cells were SBC5, unmatched with DCs from healthy human leukocyte antigen (HLA)-A24, or Sq-1, matched with DCs. Enzyme-linked immunosorbent assay was used to determine the amount of cytokines. To examine the intracellular signaling system, intracellular staining was used. RESULTS: PTPN3 knockdown significantly increased the number of DCs, expression of CD80 and chemokine receptor (CCR)7, and production of interleukin-12p40/p70 in mature DCs. In the HLA-A24-restricted DC and human lung squamous cell carcinoma cell cytotoxic assay, inhibition of PTPN3 expression in mature DCs induced cytotoxic T lymphocytes with increased production of INF-γ and granzyme B, and enhanced toxicity against cancer cells and migration to cancer. Furthermore, inhibition of PTPN3 expression activated the mitogen-activated protein kinase pathway in DCs. CONCLUSION: Based on our findings, inhibition of PTPN3 expression could contribute to the development of novel cancer immunotherapies that activate not only lymphocytes but also DCs.

PTPN3 Could Βe a Therapeutic Target of Pancreatic Cancer.

BACKGROUND/AIM: Recently, protein tyrosine phosphatase non-receptor type 3 (PTPN3) has gained attention. However, the role of PTPN3 in cancer has not been fully elucidated. In the present study, we analyzed the role of PTPN3 in pancreatic cancer and investigated whether PTPN3 could be a new therapeutic target for pancreatic cancer. MATERIALS AND METHODS: Two pancreatic ductal adenocarcinoma (PDAC) cell lines were used as target cells. Cell proliferation was investigated using cell counting and a xenograft mouse model. Migration and invasion were analyzed using Transwell inserts. Activation-related signaling molecules were examined by western blotting. RESULTS: PTPN3 contributes to the proliferation, migration, and invasion of PDAC cells in vitro. PTPN3 promotes tumor growth in a mouse xenograft model, an action mediated partially through the MAPK pathway. CONCLUSION: PTPN3 could be a new therapeutic target for pancreatic cancer.

Molecular basis of the interaction of the human tyrosine phosphatase PTPN3 with the hepatitis B virus core protein.

Interactions between the hepatitis B virus core protein (HBc) and host cell proteins are poorly understood, although they may be essential for the propagation of the virus and its pathogenicity. HBc has a C-terminal PDZ (PSD-95, Dlg1, ZO-1)-binding motif (PBM) that is responsible for interactions with host PDZ domain-containing proteins. In this work, we focused on the human protein tyrosine phosphatase non-receptor type 3 (PTPN3) and its interaction with HBc. We solved the crystal structure of the PDZ domain of PTPN3 in complex with the PBM of HBc, revealing a network of interactions specific to class I PDZ domains despite the presence of a C-terminal cysteine in this atypical PBM. We further showed that PTPN3 binds the HBc protein within capsids or as a homodimer. We demonstrate that overexpression of PTPN3 significantly affects HBV infection in HepG2 NTCP cells. Finally, we performed proteomics studies on both sides by pull-down assays and screening of a human PDZ domain library. We identified a pool of human PBM-containing proteins that might interact with PTPN3 in cells and that could be in competition with the HBc PBM during infection, and we also identified potential cellular partners of HBc through PDZ-PBM interactions. This study opens up many avenues of future investigations into the pathophysiology of HBV.

NFκB and TGFß contribute to the expression of PTPN3 in activated human lymphocytes.

We previously reported that protein tyrosine phosphatase non-receptor type 3 (PTPN3), which is upregulated in activated lymphocytes, acts as an immune checkpoint. However, the mechanism by which PTPN3 expression is enhanced in activated lymphocytes is unknown. In this study, we analyzed the mechanism of PTPN3 expression in activated lymphocytes with a view for developing a novel immune checkpoint inhibitor that suppresses PTPN3. Through the activation process, lymphocytes showed enhanced NFκB activation as well as increased PTPN3 expression. NFκB enhanced proliferation, migration, and cytotoxicity of lymphocytes. Furthermore, NFκB enhanced PTPN3 expression and tyrosine kinase activation. TGFß reduced PTPN3 expression and NFκB activation in the cancer microenvironment, and suppressed the biological activity of lymphocytes. The results of this study are expected to provide significant implications for improving existing immunotherapy and developing novel immunotherapy.

PTPN3 Inhibits the Growth and Metastasis of Clear Cell Renal Cell Carcinoma via Inhibition of PI3K/AKT Signaling.

The underlying molecular mechanism driving clear cell renal cell carcinoma (ccRCC) progression is still to be explored. The significant downregulation of protein tyrosine phosphatase nonreceptor type 3 (PTPN3) expression in the tumor tissues suggested its protective role in ccRCC progression. IHC analysis of PTPN3 protein in 172 ccRCC tissue revealed that PTPN3 was an independently favorable prognostic factor for progression-free survival (P = 0.0166) and overall survival (P = 0.0343) of patients. The ccRCC cell lines SN12C, 1932, ACHN, and Caki-1 were used to evaluate, both in vitro and in vivo, the biological roles of PTPN3. We observed that overexpression of PTPN3 significantly inhibited the proliferation, migration, and invasion of ccRCC cells. In contrast, the knocking down of PTPN3 elicited opposite effects. Overexpressing PTPN3 inhibited xenograft tumor growth and lung metastasis displayed by the in vivo mice models. PTPN3 inhibited tumor cell motility by suppressing the phosphorylation of AKT, and subsequently inactivating the PI3K/AKT signaling pathway of renal cell carcinoma cells. Furthermore, the inhibition of phospho-AKTThr308 and phospho-AKTSer473 reversed PTPN3-induced silencing in tumor cell migration. Our work revealed that the overexpression of PTPN3 could suppress kidney cancer progression by negatively regulating the AKT signaling pathway, and served as a favorable prognostic factor in patients with ccRCC. Our findings provided insight that PTPN3 could be a potential target for therapy aiming to inhibit the malignant behaviors of ccRCC. IMPLICATIONS: PTPN3 is an independent favorable prognostic factor for patients with ccRCC and could be a potential target for therapy aiming to inhibit the malignant behaviors of ccRCC.

MicroRNA-574-5p in gastric cancer cells promotes angiogenesis by targeting protein tyrosine phosphatase non-receptor type 3 (PTPN3).

We elucidate in this study that up-regulation of miR-574-5p in gastric cancer cells under hypoxic conditions contributed to angiogenesis. We found that miR-574-5p and HIF-1α were up-regulated in gastric cancer cells cultured under 2% O2 or in medium containing CoCl2, and in muscle tissues of mice injected with NaNO2, indicating up-regulation of miR-574-5p in vitro or in vivo in response to hypoxic conditions. We hypothesized that up-regulation of miR-574-5p could promote angiogenesis. Transfection of gastric cancer cells with miR-574-5p mimics or inhibitor resulted in increase or decrease in the expression of VEGFA. Viability, migration, invasion and tube formation of HUVECs cultured with conditioned medium from SGC/574 cells transfected with miR-574-5p inhibitor were reduced. Tube formation of HUVECs cultured with conditioned medium from SGC-7901 cells transfected with miR-574-5p mimics was increased. An in vivo study demonstrated that inhibition of miR-574-5p in the tumor xenografts of mice reduced the expression of CD31 one of the endothelial cell markers. We identified PTPN3 a tyrosine phosphatase as a target of miR-574-5p that bound to the 3'UTR of PTPN3 mRNA to inhibit the expression of PTPN3. Furthermore, the data in this study demonstrated that inhibition of PTPN3 in gastric cancer cells enhanced phosphorylation of p44/42 MAPKs and promoted angiogenesis. We conclude that miR-574-5p in gastric cancer cells promoted angiogenesis via enhancing phosphorylation of p44/42 MAPKs by miR-574-5p inhibition of PTPN3 expression.

PTPN3 suppresses the proliferation and correlates with favorable prognosis of perihilar cholangiocarcinoma by inhibiting AKT phosphorylation.

BACKGROUND: Perihilar cholangiocarcinoma (PHCCA) is the most common type of human cholangiocarcinoma with a very dismal prognosis. Tumor markers and target drugs of PHCCA are desperately needed. Protein phosphatase N3 (PTPN3) has dual roles in the progression of human cancers, but its expression and functions in PHCCA have not been elucidated. MATERIALS AND METHODS: The expression of PTPN3 in PHCCA was detected with western blotting, qRT-PCR and immunohistochemistry. The clinical significance of PTPN3 was identified by analyzing the correlations between its expression and the clinicopathological variables, and the prognostic value was evaluated by univariate and multivariate analyses. The functions of PTPN3 in the progression of PHCCA were estimated with both in vitro and in vivo experiments. RESULTS: PTPN3 expression was down-regulated in PHCCA compared with normal bile duct. Low PTPN3 expression was markedly associated with large tumor size and unfavorable prognosis. After knocking down PTPN3, the percentages of G2/S phase of PHCCA cells were elevated, and the proliferation increased significantly. Moreover, we demonstrated that the phosphorylation of AKT was elevated by PTPN3 knockdown, and it was required in PTPN3-involved proliferation of PHCCA. Within vivo experiments, PTPN3 and AKT inhibitor MK-2206 were demonstrated to suppress tumor size of PHCCA. CONCLUSION: PTPN3 was a favorable prognostic biomarker of PHCCA. PTPN3 suppressed the proliferation of PHCCA by inhibiting AKT phosphorylation and arresting cell cycle. Our results suggested thatpost-operative detection of PTPN3 would be a helpful approach to stratify the PHCCA patients with high-risk.

PTPN3 expressed in activated T lymphocytes is a candidate for a non-antibody-type immune checkpoint inhibitor.

It has been shown that protein tyrosine phosphatase non-receptor type (PTPN) 3 inhibits T-cell activation. However, there is no definitive conclusion about how the inhibition of PTPN3 in lymphocytes affects immune functions in human lymphocytes. In the present study, we showed that PTPN3 inhibition significantly contributes to the enhanced activation of activated human lymphocytes. The PTPN3 expression of lymphocytes was significantly increased through the activation process using IL-2 and anti-CD3 mAb. Interestingly, inhibiting the PTPN3 expression in activated lymphocytes significantly augmented the proliferation, migration, and cytotoxicity through the phosphorylation of zeta-chain-associated protein kinase 70 (ZAP-70), lymphocyte-specific protein tyrosine kinase (LCK), and extracellular signal-regulated kinases (ERK). Lymphocyte activation by PTPN3 inhibition was observed only in activated CD3+ T cells and not in NK cells or resting T cells. In therapy experiments using autologous tumors and lymphocytes, PTPN3 inhibition significantly augmented the number of tumor-infiltrated lymphocytes and the cytotoxicity of activated lymphocytes. Our results strongly imply that PTPN3 acts as an immune checkpoint in activated lymphocytes and that PTPN3 inhibitor may be a new non-antibody-type immune checkpoint inhibitor for cancer therapy.

PTPN3 suppresses lung cancer cell invasiveness by counteracting Src-mediated DAAM1 activation and actin polymerization.

Cancer cell migration plays a crucial role during the metastatic process. Reversible tyrosine phosphorylation by protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs) have been implicated in the regulation of cancer cell migration and invasion. However, the underlying mechanisms have not been fully elucidated. Here, we show that depletion of the FERM and PDZ domain-containing protein tyrosine phosphatase PTPN3 enhances lung cancer cell migration/invasion and metastasis by promoting actin filament assembly and focal adhesion dynamics. We further identified Src and DAAM1 (dishevelled associated activator of morphogenesis 1) as interactors of PTPN3. DAAM1 is a formin-like protein involved in the regulation of actin cytoskeletal remodeling. PTPN3 inhibits Src activity and Src-mediated phosphorylation of Tyr652 on DAAM1. The tyrosine phosphorylation of DAAM1 is essential for DAAM1 homodimer formation and actin polymerization. Ectopic expression of a DAAM1 phosphodeficient mutant inhibited F-actin assembly and suppressed lung cancer cell migration and invasion. Our findings reveal a novel mechanism by which reversible tyrosine phosphorylation of DAAM1 by Src and PTPN3 regulates actin dynamics and lung cancer invasiveness.

PTPN3 acts as a tumor suppressor and boosts TGF-ß signaling independent of its phosphatase activity.

TGF-ß controls a variety of cellular functions during development. Abnormal TGF-ß responses are commonly found in human diseases such as cancer, suggesting that TGF-ß signaling must be tightly regulated. Here, we report that protein tyrosine phosphatase non-receptor 3 (PTPN3) profoundly potentiates TGF-ß signaling independent of its phosphatase activity. PTPN3 stabilizes TGF-ß type I receptor (TßRI) through attenuating the interaction between Smurf2 and TßRI. Consequently, PTPN3 facilitates TGF-ß-induced R-Smad phosphorylation, transcriptional responses, and subsequent physiological responses. Importantly, the leucine-to-arginine substitution at amino acid residue 232 (L232R) of PTPN3, a frequent mutation found in intrahepatic cholangiocarcinoma (ICC), disables its role in enhancing TGF-ß signaling and abolishes its tumor-suppressive function. Our findings have revealed a vital role of PTPN3 in regulating TGF-ß signaling during normal physiology and pathogenesis.

Up-regulation of microRNA-497-5p inhibits colorectal cancer cell proliferation and invasion via targeting PTPN3.

To investigate the role of microRNA-497-5p (miR-497-5p) in the tumorigenesis of colorectal cancer (CRC), the present study applied qRT-PCR to detect the expression level of miR-497-5p in both clinical samples and CRC cell lines. Furthermore, to specifically evaluate the carcinogenic role of miR-497-5p in CRC, the expression of miR-497-5p was monitored by transfecting with the mimics or inhibitors of miR-497-5p. Transwell assay as well as CCK-8 assay were used to determine the functions of miR-497-5p on cell invasion, migration and proliferation, respectively. miR-497-5p expression was remarkably down-regulated in clinical samples with cancer development as well as in CRC cell lines. Additionally, low miR-497-5p expression was remarkably correlated with higher TNM stage and lymph node metastasis of CRC patients. Up-regulation of miR-497-5p significantly inhibited proliferation, migration, and invasion of LOVO CRC cell line. Conversely, antagonizing miR-497-5p significantly promoted cell proliferation, migration and invasion. Mechanistic analysis revealed that miR-497-5p directly bound to its downstream target, protein tyrosine phosphatase non-receptor type 3 (PTPN3), whose aberrant expression partially reversed inhibition of cell proliferation and migration. Taken together, the present study elucidated the inhibitory role of miR-497-5p in CRC via targeting PTPN3, which potentiated miR-497-5p as a potential therapeutic target for combating CRC.

Structural and functional characterization of the PDZ domain of the human phosphatase PTPN3 and its interaction with the human papillomavirus E6 oncoprotein.

The human protein tyrosine phosphatase non-receptor type 3 (PTPN3) is a PDZ (PSD-95/Dlg/ZO-1) domain-containing phosphatase with a tumor-suppressive or a tumor-promoting role in many cancers. Interestingly, the high-risk genital human papillomavirus (HPV) types 16 and 18 target the PDZ domain of PTPN3. The presence of a PDZ binding motif (PBM) on E6 confers interaction with a number of different cellular PDZ domain-containing proteins and is a marker of high oncogenic potential. Here, we report the molecular basis of interaction between the PDZ domain of PTPN3 and the PBM of the HPV E6 protein. We combined biophysical, NMR and X-ray experiments to investigate the structural and functional properties of the PDZ domain of PTPN3. We showed that the C-terminal sequences from viral proteins encompassing a PBM interact with PTPN3-PDZ with similar affinities to the endogenous PTPN3 ligand MAP kinase p38γ. PBM binding stabilizes the PDZ domain of PTPN3. We solved the X-ray structure of the PDZ domain of PTPN3 in complex with the PBM of the HPV E6 protein. The crystal structure and the NMR chemical shift mapping of the PTPN3-PDZ/peptide complex allowed us to pinpoint the main structural determinants of recognition of the C-terminal sequence of the E6 protein and the long-range perturbations induced upon PBM binding.

The Protein Tyrosine Phosphatase H1 PTPH1 Supports Proliferation of Keratinocytes and is a Target of the Human Papillomavirus Type 8 E6 Oncogene.

Human papillomaviruses (HPV) replicate their DNA in the suprabasal layer of the infected mucosa or skin. In order to create a suitable environment for vegetative viral DNA replication HPV delay differentiation and sustain keratinocyte proliferation that can lead to hyperplasia. The mechanism underlying cell growth stimulation is not well characterized. Here, we show that the E6 oncoprotein of the ßHPV type 8 (HPV8), which infects the cutaneous skin and is associated with skin cancer in Epidermodysplasia verruciformis patients and immunosuppressed organ transplant recipients, binds to the protein tyrosine phosphatase H1 (PTPH1), which resulted in increased protein expression and phosphatase activity of PTPH1. Suppression of PTPH1 in immortalized keratinocytes reduced cell proliferation as well as the level of epidermal growth factor receptor (EGFR). Furthermore, we report that HPV8E6 expressing keratinocytes have increased level of active, GTP-bound Ras. This effect was independent of PTPH1. Therefore, HPV8E6-mediated targeting of PTPH1 might result in higher level of EGFR and enhanced keratinocyte proliferation. The HPV8E6-mediated stimulation of Ras may be an additional step to induce cell growth. Our results provide novel insights into the mechanism how ßHPVE6 proteins support proliferation of infected keratinocytes, thus creating an environment with increased risk of development of skin cancer particularly upon UV-induced DNA mutations.

PTPH1 immunohistochemical expression and promoter methylation in breast cancer patients from India: A retrospective study.

Protein Tyrosine Phosphatase H1/Protein Tyrosine Phosphatase Non receptor Type 3 (PTPH1/PTPN3) is upregulated and/or mutated in glioma, ovarian, gastric, and colorectal cancers. Previous studies have documented that PTPH1-associated breast cancers exhibit enhanced sensitivity to tamoxifen and tyrosine kinase inhibitors through dephosphorylation of ER and epidermal growth factor receptor, respectively. Owing to the key role that PTPH1 plays as a biomarker in predicting the response of chemotherapeutic drugs and lack of studies on Indian breast cancer patients, the present study investigated PTPH1 protein expression and its relationship to clinical features, ER/PR/HER2/neu statuses, and methylation of promoter in breast cancer tissues (n = 67) among Indian population by immunohistochemistry and methylation specific polymerase chain reaction. PTPH1 expression was upregulated in 58.21% (39/67) and downregulated in the rest of tumor specimens, and it correlated with ER, PR, and HER2/neu statuses with p values of <0.0001, 0.0113, and 0.0448, respectively. Additionally, we found that the 2 kb region upstream of PTPH1 gene harbored CpG sites within, and was ubiquitously methylated in breast cancer (n = 13), colon cancer tissue (n = 1), uterine cancer tissue (n = 1), normal breast tissue (n = 1) in addition to Hela and MCF7 cell lines. In conclusion, our data showed a strong correlation of the PTPH1 status with the ER and ubiquitous nature of PTPH1 promoter methylation at specific CpG sites irrespective of cancer types and protein expression. Our findings underscore the clinical relevance of PTPH1 expression in Indian patients and warrant additional studies to explore the importance of ubiquitously methylated promoter at specific CpG sites in upstream of the PTPH1 gene.

High Expression of PTPN3 Predicts Progression and Unfavorable Prognosis of Glioblastoma.

BACKGROUND PTPN3 was demonstrated to be involved in the progression of several types of cancers, such as gastric adenocarcinoma, lung cancer, and intrahepatic cholangiocarcinoma. However, its clinical significance in glioblastoma (GBM) has not been elucidated. MATERIAL AND METHODS We investigated the expression of PTPN3 in 95 cases of GBM with immunohistochemistry and in 8 pairs of fresh GBMs and their adjacent tissues with qualitative polymerase chain reaction. Moreover, the correlation between PTPN3 and clinicopathological factors was evaluated by chi-square test. The prognostic value of PTPN3 was investigated with univariate analysis and multivariate analysis. With MTT assay and Transwell assay, the oncogenic functions of PTPN3 in GBM proliferation and invasion were further investigated. RESULTS Expression of PTPN3 in GBM tissues was significantly higher than in their corresponding adjacent tissues. High expression of PTPN3 was significantly associated with unfavorable prognosis of GBM. Moreover, in GBM cell lines, PTPN3 promoted cell proliferation and invasion, and the PTP common inhibitor pervanadate suppressed GBM proliferation and invasion. CONCLUSIONS Our experiments show that PTPN3 is an independent prognostic factor in GBM and indicated that postoperative detection of PTPN3 can be used to identify high-risk patients and guide individual treatment.

Protein tyrosine phosphatase PTPN3 promotes drug resistance and stem cell-like characteristics in ovarian cancer.

The current standard treatment for ovarian cancer is aggressive surgery followed by platinum-based combination chemotherapy. Recurrence and chemotherapeutic drug resistance are the two main factors that account for the high mortality of most ovarian cancers. Liposomal doxorubicin is primarily used for the treatment of ovarian cancer when the disease has progressed after platinum-based chemotherapy. However, relatively little is known about the genomic changes that contribute to both cisplatin and doxorubicin resistance in high-grade serous ovarian cancer (HGSC) under the selective pressure of chemotherapy. Here, we found that protein tyrosine phosphatase PTPN3 gene expression was substantially increased in both cisplatin and doxorubicin-resistant ovarian cancer cells. Silencing of PTPN3 restored sensitivity to cisplatin and doxorubicin in resistant ovarian cancer cells. Down-regulation of PTPN3 also inhibited cell cycle progression, migration, stemness in vitro and the tumorigenicity of resistant ovarian cancer cells in vivo. Meanwhile, the expression of PTPN3 was found to be regulated by miR-199 in resistant ovarian cancer cells. These findings suggest that PTPN3 promotes tumorigenicity, stemness and drug resistance in ovarian cancer, and thus is a potential therapeutic target for the treatment of ovarian cancer.

PTPH1 promotes tumor growth and metastasis in human glioma.

OBJECTIVE: Glioma is the most common form of brain tumor, accounting for over 50% of all primary tumors. Despite progress in the treatment of glioma, the prognosis is still poor. In this study, we examined protein-tyrosine phosphatase H1 (PTPH1) in human gliomas. MATERIALS AND METHODS: Cell growth potential was measured by CCK-8 assay and colony formation. Cell cycle distribution was measured by flow cytometry. Transwell assay was used to detect the motility of tumor cells. Real-time PCR and Western blot were used to measure the mRNA and protein expression of indicated genes. Xenograft model was established to measure the role of PTPH1 in vivo. RESULTS: The expression of PTPH1 was significantly higher in the tumor tissues as compared with that in the adjacent normal tissues. Knockdown of PTPH1 significantly slowed cell proliferation and reduced colony formation abilities in glioma cell lines U87 and U251. Additionally, knockdown of PTPH1 caused cell cycle arrest in the S-phase. Furthermore, depletion of PTPH1 in glioma U87 cells significantly limited tumor growth in a xenograft model. Interestingly, knockdown of PTPH1 also decreased cell migration abilities in both U87 and U251 cells. Accordingly, matrix metalloproteinase 9 (MMP9) was also decreased upon knockdown of PTPH1 in both cell lines. Moreover, we found that phosphorylated MEK (p-MEK) and phosphorylated MAPK (p-MAPK) were both decreased, whereas the total levels of MEK and MAPK remained unchanged after depletion of PTPH1 in both cell lines. CONCLUSIONS: Our data suggest that PTPH1 may be a novel biomarker that indicates the aggressiveness of gliomas. Targeting PTPH1 might be a promising strategy for the treatment of gliomas.

Tyrosine dephosphorylation enhances the therapeutic target activity of epidermal growth factor receptor (EGFR) by disrupting its interaction with estrogen receptor (ER).

Protein-protein interactions can increase or decrease its therapeutic target activity and the determining factors involved, however, are largely unknown. Here, we report that tyrosine-dephosphorylation of epidermal growth factor receptor (EGFR) increases its therapeutic target activity by disrupting its interaction with estrogen receptor (ER). Protein tyrosine phosphatase H1 (PTPH1) dephosphorylates the tyrosine kinase EGFR, disrupts its interaction with the nuclear receptor ER, and increases breast cancer sensitivity to small molecule tyrosine kinase inhibitors (TKIs). These effects require PTPH1 catalytic activity and its interaction with EGFR, suggesting that the phosphatase may increase the sensitivity by dephosphorylating EGFR leading to its dissociation with ER. Consistent with this notion, a nuclear-localization defective ER has a higher EGFR-binding activity and confers the resistance to TKI-induced growth inhibition. Additional analysis show that PTPH1 stabilizes EGFR, stimulates the membranous EGFR accumulation, and enhances the growth-inhibitory activity of a combination therapy of TKIs with an anti-estrogen. Since EGFR and ER both are substrates for PTPH1 in vitro and in intact cells, these results indicate that an inhibitory EGFR-ER protein complex can be switched off through a competitive enzyme-substrate binding. Our results would have important implications for the treatment of breast cancer with targeted therapeutics.