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A Positive Feed-forward Loop Associating EGR1 and PDGFA Promotes Proliferation and Self-renewal in Glioblastoma Stem Cells.

ABSTRACT: Glioblastomas are the most common primary brain tumors, highly vascularized, infiltrating, and resistant to current therapies. This cancer leads to a fatal outcome in less than 18 months. The aggressive behavior of glioblastomas, including resistance to current treatments and tumor recurrence, has been attributed to glioma stemlike/progenitor cells. The transcription factor EGR1 (early growth response 1), a member of a zinc finger transcription factor family, has been described as tumor suppressor in gliomas when ectopically overexpressed. Although EGR1 expression in human glioblastomas has been associated with patient survival, its precise location in tumor territories as well as its contribution to glioblastoma progression remain elusive. In the present study, we show that EGR1-expressing cells are more frequent in high grade gliomas where the nuclear expression of EGR1 is restricted to proliferating/progenitor cells. We show in primary cultures of glioma stemlike cells that EGR1 contributes to stemness marker expression and proliferation by orchestrating a PDGFA-dependent growth-stimulatory loop. In addition, we demonstrate that EGR1 acts as a positive regulator of several important genes, including SHH, GLI1, GLI2, and PDGFA, previously linked to the maintenance and proliferation of glioma stemlike cells.

SUBMITTER: Sakakini N

PROVIDER: S-EPMC4865916 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Analysis of miRNA expression in human breast cancer samples with Agilent's miRNA arrays. These samples are part of a study where we have investigated the mammalian cell proliferation control network consisting of transcription regulators, E2F and p53, their targets, and a family of 14 microRNAs. We observed that indicative of their significance, expression of these microRNAs is down-regulated in senescent cells and in breast cancers harboring wild-type p53. These microRNAs are repressed by p53 in an E2F1-mediated manner. Abstract of paper: Normal cell growth is governed by a complicated biological system, featuring multiple levels of control, often deregulated in cancers. The role of microRNAs in the control of gene expression is now increasingly appreciated, yet their involvement in controlling cell proliferation is still not well understood. Here we investigated the mammalian cell proliferation control network consisting of transcription regulators, E2F and p53, their targets, and a family of 14 microRNAs. Indicative of their significance, expression of these microRNAs is down-regulated in senescent cells and in breast cancers harboring wild-type p53. These microRNAs are repressed by p53 in an E2F1-mediated manner. Furthermore, we show that these microRNAs silence anti-proliferative genes, which themselves are E2F1 targets. Thus, microRNAs and transcriptional regulators appear to cooperate in the framework of a multi-gene transcriptional and post-transcriptional feed-forward loop. Finally, we show that, similarly to p53 inactivation, overexpression of representative microRNAs promotes proliferation and delays senescence, manifesting the detrimental phenotypic consequence of perturbations in this circuit. Together these findings position microRNAs as novel key players in the mammalian cellular proliferation network. Keywords: Breast Cancer, miRNA, p53. 18 Primary human breast cancer samples analyzed for their miRNA expression. From two to four replicates were performed for each sample. Quality check (QC) were performed with Feature Extraction 9.1.3.44 and arrays not passing QC were excluded

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A Positive Feed-forward Loop Associating EGR1 and PDGFA Promotes Proliferation and Self-renewal in Glioblastoma Stem Cells.

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