Project description: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.
Project description:Mutations in the parkin gene, which encodes a ubiquitin ligase, are a major genetic cause of parkinsonism. Interestingly, parkin also plays a role in cancer as a putative tumor suppressor, and the gene is frequently targeted by deletion and inactivation in human malignant tumors. Here, we investigated a potential tumor suppressor role for parkin in gliomas. We found that parkin expression was dramatically reduced in glioma cells. Restoration of parkin expression promoted G1 phase cell cycle arrest and mitigated the proliferation rate of glioma cells in vitro and in vivo. Notably, parkin-expressing glioma cells showed a reduction in levels of cyclin D1, but not cyclin E, and a selective downregulation of Akt serine-473 phosphorylation and VEGF receptor levels. In accordance, cells derived from a parkin null mouse model exhibited increased levels of cyclin D1, VEGF receptor and Akt phosphorylation and divided significantly faster when compared with wild type cells, with suppressionof these changes following parkin re-introduction. Clinically, analysis of parkin pathway activation was predictive for the survival outcome of glioma patients. Taken together, our study provides mechanistic insight into the tumor suppressor function of parkin in brain tumors, and suggests that measurement of parkin pathway activation may be used clinically as a prognostic tool in brain tumor patients.
Project description:HOX genes encode a family of homeodomain-containing transcription factors involved in the determination of cell fate and identity during embryonic development. They also behave as oncogenes in some malignancies. In this study, we found high expression of the HOXD9 gene transcript in glioma cell lines and human glioma tissues by quantitative real-time PCR. Using immunocytochemistry, we observed HOXD9 protein expression in human brain tumor tissues, including astrocytomas and glioblastomas. To investigate the role of HOXD9 in gliomas, we silenced its expression in the glioma cell line U87 using HOXD9-specific siRNA, and observed decreased cell proliferation, cell cycle arrest, and induction of apoptosis. It was suggested that HOXD9 contributes to both cell proliferation and/or cell survival. The HOXD9 gene was highly expressed in a side population (SP) of SK-MG-1 cells that was previously identified as an enriched-cell fraction of glioma cancer stem-like cells. HOXD9 siRNA treatment of SK-MG-1 SP cells resulted in reduced cell proliferation. Finally, we cultured human glioma cancer stem cells (GCSCs) from patient specimens found with high expression of HOXD9 in GCSCs compared with normal astrocyte cells and neural stem/progenitor cells (NSPCs). Our results suggest that HOXD9 may be a novel marker of GCSCs and cell proliferation and/or survival factor in gliomas and glioma cancer stem-like cells, and a potential therapeutic target. we analyzed the expression and function of HOXD9 in human gliomas and found high expression of HOXD9 in GCSCs. HOXD9 contributes to cell proliferation and/or survival in glioma cells and glioma cancer stem-like cells.
Project description:Analysis of whole genome gene expression in control and PARKIN patient lines. The hypothesis tested in the present study was that the deficient of PARKIN expression affects multiple pathways. Results provide important information on relationship between PARKIN and mitochondria related gene expression. Total RNA obtained from patient fibroblast and iPSC compare to control fibroblast and iPSC.
Project description:Genome-wide mRNA expression profiles of 200 primary gastric tumors from the Singapore patient cohort. Gastric cancer (GC) is the second leading cause of global cancer mortality, with individual gastric tumors displaying significant heterogeneity in their deregulation of various oncogenic pathways. We aim to identify major oncogenic pathways in GC that robustly impact patient survival and treatment response. We used an in silico strategy based on gene expression signatures and connectivity analytics to map patterns of oncogenic pathway activation in 25 unique GC cell lines, and in 301 primary gastric cancers from three independent patient cohorts. Of 11 oncogenic pathways previously implicated in GC, we identified three predominant pathways (proliferation/stem cell, NF-kB, and Wnt/b-catenin) deregulated in the majority (>70%) of gastric tumors. Using a variety of proliferative, Wnt, and NF-kB-related assays, we experimentally validated the pathway predictions in multiple GC cell lines showing similar pathway activation patterns in vitro. Patients stratified at the level of individual pathways did not exhibit consistent differences in clinical outcome. However, patients grouped by oncogenic pathway combinations demonstrated robust and significant survival differences (e.g., high proliferation/high NF-kB vs. low proliferation/low NF-kB), suggesting that tumor behavior in GC is likely influenced by the combined effects of multiple oncogenic pathways. Our results demonstrate that GCs can be successfully taxonomized by oncogenic pathway activity into biologically and clinically relevant subgroups. Experiment Overall Design: Profiling of 200 primary gastric tumors on Affymetrix GeneChip Human Genome U133 Plus 2.0 Array. All tumors were collected with approvals from the National Cancer Centre, Singapore; the Research Ethics Review Committee; and signed patient informed consent.