COX-2 overexpression increases malignant potential of human glioma cells through Id1

• Type of Material: Article
• Authors: Kaiming Xu, Emory University; Lanfang Wang, affiliation; Hui-Kuo Shu, Emory University
• Language: English
• Date: 2014-05
• Publisher: Impact Journals
• Publication Version: Final Published Version
• Copyright Statement: © 2014 Xu et al.
• License: Creative Commons Attribution 3.0 Unported
• Final Published Version (URL): http://www.impactjournals.com/oncotarget/index.php?journal=oncotarget&page=issue&op=view&path[]=61
• Title of Journal or Parent Work: Oncotarget
• ISSN: 1949-2553
• Volume: 5
• Issue: 5
• Start Page: 1241
• End Page: 1252
• Keywords: tumorigenesis; glioblastoma; cyclooxygenase-2; brain tumor; Id1; glioma
• Research Categories: Health Sciences, General; Health Sciences, Oncology; Health Sciences, Radiology

Abstract

Increased COX-2 expression directly correlates with glioma grade and is associated with shorter survival in glioblastoma (GBM) patients. COX-2 is also regulated by epidermal growth factor receptor signaling which is important in the pathogenesis of GBMs. However, COX-2 expression has not been previously shown to directly alter malignancy of GBMs. Id1 is a member of the helix-loop-helix (HLH) family of transcriptional repressors that act as dominant-negative inhibitors of basic-HLH factors. This factor has been shown to be regulated by COX-2 in breast carcinoma cells and recent studies suggest that Id1 may also be involved in the genesis/progression of gliomas. We now show that COX-2 increases the aggressiveness of GBM cells. GBM cells with COX-2 overexpression show increased growth of colonies in soft agar. Tumorigenesis in vivo is also increased in both subcutaneous flank and orthotopic intracranial tumor models. COX-2 overexpression induces Id1 expression in two GBM cell lines suggesting a role for Id1 in glioma transformation/tumorigenesis. Furthermore, we find direct evidence of a role for Id1 with significant suppression of in vitro transformation and in vivo tumorigenesis in COX-2-overexpressing GBM cells where Id1 has been knocked down. In fact, Id1 is even more efficient at enhancing transformation/tumorigenesis of GBM cells than COX-2. Finally, GBM cells with COX-2 or Id1 overexpression show greater migration/invasive potential and tumors that arise from these cells also display increased microvessel density, results in line with the increased malignant potential seen in these cells. Thus, COX-2 enhances the malignancy of GBM cells through induction of Id1.