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Loss-of-parkin function enhances cyclin D1 expression and AKT signalling and promotes glioblastoma cell proliferation

ABSTRACT: Mutations in the parkin gene, which encodes a ubiquitin ligase, are a major cause of autosomal recessive parkinsonism. Interestingly, parkin also plays a role in cancer as a putative tumor suppressor. Consistent with this, the gene is frequently targeted by deletion and inactivation in human malignant tumors. Here, we show that parkin expression is dramatically reduced in glioma cells, which correlates with increased cancer mortality. We further show that restoration of parkin expression in these cells promotes their arrest at G1 phase and significantly mitigates their proliferation rate both in vitro and in vivo. Notably, the level of cyclin D1, but not cyclin E, is reduced in parkin-expressing glioma cells. Moreover, parkin expression also leads to a selective downregulation of Akt serine-473 phosphorylation and VEGF receptor levels. Supporting this, cells derived from parkin null mouse exhibit increased levels of cyclin D1, VEGF receptor and Akt phosphorylation and divide significantly faster compared to their wild type counterparts. Importantly, analysis of parkin pathway activation revealed its predictive power for survival outcome of glioma patients. Taken together, our study provides a mechanism by which parkin exerts its tumor suppressor function and a signature pathway of parkin that is of potential prognostic value. Total RNA obtained from U-87MG cells stably expressing parkin or vector alone. Replicate arrays were performed for each of the 3 vector and parkin-expressing U-87MG clones.

ORGANISM(S): Homo sapiens

SUBMITTER: Yeo CW

PROVIDER: S-ECPF-GEOD-29494 | biostudies-other | 2012 May

REPOSITORIES: biostudies-other

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Project description:Objective: The tyrosine phosphatase SHP2 has a dual role in cancer initiation and progression in a tissue type-dependent manner. Several studies have linked SHP2 to the aggressive behavior of breast cancer cells and poorer outcomes in people with cancer. Nevertheless, the mechanistic details of how SHP2 promotes breast cancer progression remain largely undefined. Methods: The relationship between SHP2 expression and the prognosis of patients with breast cancer was investigated by using the TCGA and GEO databases. The expression of SHP2 in breast cancer tissues was analyzed by immunohistochemistry. CRISPR/Cas9 technology was used to generate SHP2-knockout breast cancer cells. Cell-counting kit-8, colony formation, cell cycle, and EdU incorporation assays, as well as a tumor xenograft model were used to examine the function of SHP2 in breast cancer proliferation. Quantitative RT-PCR, western blotting, immunofluorescence staining, and ubiquitination assays were used to explore the molecular mechanism through which SHP2 regulates breast cancer proliferation. Results: High SHP2 expression is correlated with poor prognosis in patients with breast cancer. SHP2 is required for the proliferation of breast cancer cells in vitro and tumor growth in vivo through regulation of Cyclin D1 abundance, thereby accelerating cell cycle progression. Notably, SHP2 modulates the ubiquitin-proteasome-dependent degradation of Cyclin D1 via the PI3K/AKT/GSK3β signaling pathway. SHP2 knockout attenuates the activation of PI3K/AKT signaling and causes the dephosphorylation and resultant activation of GSK3β. GSK3β then mediates phosphorylation of Cyclin D1 at threonine 286, thereby promoting the translocation of Cyclin D1 from the nucleus to the cytoplasm and facilitating Cyclin D1 degradation through the ubiquitin-proteasome system. Conclusions: Our study uncovered the mechanism through which SHP2 regulates breast cancer proliferation. SHP2 may therefore potentially serve as a therapeutic target for breast cancer.

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Loss-of-parkin function enhances cyclin D1 expression and AKT signalling and promotes glioblastoma cell proliferation

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