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.

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.

PTPH1 cooperates with vitamin D receptor to stimulate breast cancer growth through their mutual stabilization.

Tyrosine phosphorylation is tightly regulated by protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs), and has a critical role in malignant transformation and progression. Although PTKs have a well-established role in regulating breast cancer growth, contribution of PTPs remains mostly unknown. Here, we report that the tyrosine phosphatase PTPH1 stimulates breast cancer growth through regulating vitamin D receptor (VDR) expression. PTPH1 was shown to be overexpressed in 49% of primary breast cancer and levels of its protein expression positively correlate with the clinic metastasis, suggesting its oncogenic activity. Indeed, PTPH1 promotes breast cancer growth by a mechanism independent of its phosphatase activity, but dependent of its stimulatory effect on the nuclear receptor VDR protein expression and depletion of induced VDR abolishes the PTPH1 oncogenic activity. Additional analyses showed that PTPH1 binds VDR and increases its cytoplasmic accumulation, leading to their mutual stabilization and stable expression of a nuclear localization-deficient VDR abolishes the growth-inhibitory activity of the receptor independent of 1,25-dihydroxyvitamin D3. These results reveal a new paradigm in which a PTP may stimulate breast cancer growth through increasing cytoplasmic translocation of a nuclear receptor, leading to their mutual stabilization.

PTPH1 dephosphorylates and cooperates with p38gamma MAPK to increase ras oncogenesis through PDZ-mediated interaction.

Protein phosphatases are believed to coordinate with kinases to execute biological functions, but examples of such integrated activities, however, are still missing. In this report, we have identified protein tyrosine phosphatase H1 (PTPH1) as a specific phosphatase for p38gamma mitogen-activated protein kinase (MAPK) and shown their cooperative oncogenic activity through direct binding. p38gamma, a Ras effector known to act independent of its phosphorylation, was first shown to require its unique PDZ-binding motif to increase Ras transformation. Yeast two-hybrid screening and in vitro and in vivo analyses further identified PTPH1 as a specific p38gamma phosphatase through PDZ-mediated binding. Additional experiments showed that PTPH1 itself plays a role in Ras-dependent malignant growth in vitro and/or in mice by a mechanism depending on its p38gamma-binding activity. Moreover, Ras increases both p38gamma and PTPH1 protein expression and there is a coupling of increased p38gamma and PTPH1 protein expression in primary colon cancer tissues. These results reveal a coordinative oncogenic activity of a MAPK with its specific phosphatase and suggest that PDZ-mediated p38gamma/PTPH1 complex may be a novel target for Ras-dependent malignancies.