Abstract 4931: Inhibitor of DNA binding 4 (Id4) suppresses MMP2 mediated invasion of glioblastoma-derived cells by direct inactivation of twist-1 function.

Abstract

Abstract Invasion of normal tissues by high grade glioma is a key aspect of increased morbidity and mortality associated with these tumors. Malignant glioma comprise over 70% of primary brain tumors with a median survival ranging from 12 to 15 months for patients with glioblastoma multiforme (GBM), the highest grade of glial tumors. Inhibitor of DNA binding (Id) genes are highly expressed in development and tumorigenesis and some members (Id1, Id2 and Id3) have been linked to increased tumor invasion. In sharp contrast to these members of the Id gene family, we found that Id4 expression in GBM-derived cells decreased invasion in in vitro assays. Results of gain-of-function and loss-of-function experiments indicated that Id4 expression decreased GBM invasion and suppressed a gene, matrix metallo-protease 2 (MMP-2), which encodes a proteolytic enzyme key for the destruction of glial tumor extracellular matrix. Western blot and zymography analysis demonstrated that conditioned media from Id4 expressing cells had low levels of pro-MMP2 and cleaved MMP2. An antibody that is known to inactivate MMP-2 was used to demonstrate that MMP2 accumulated in media conditioned by Id4 deficient cells was sufficient to rescue the invasive activity lost in cells expressing high levels of Id4. These findings confirmed that MMP2 suppression by Id4 is responsible for the decrease in invasion observed in Id4 expressing glioma cells. Twist-1 is a well described mediator of invasion. Co-IP and co-localization studies demonstrated an interaction suggesting a direct inhibition of Twist-1 by Id4. Other data indicate that Id4 also blocks Twist-1 induced transcription of MMP2. Importantly, Twist-1 overexpression can rescue the invasion defect induced by Id4 expression, providing further support that the Id4/Twist-1 interaction mediates the function of Id4 in suppressing GBM invasion. Analysis of The Cancer Genome Atlas (TCGA) data indicated a significantly better survival and prognosis for GBM patients with high Id4 expression (Z>1) suggesting that Id4 could have an important role in the survival of GBM patients. Our data provide strong evidence demonstrating that Id4 suppresses GBM invasion by inhibiting Twist-1 induced expression of MMP2. To our knowledge, this is the first report of an Id protein acting as an inhibitor of invasion rather than mediating the pro-invasive functions of the other Id-gene family members. Citation Format: Gilbert J. Rahme, Mark A. Israel. Inhibitor of DNA binding 4 (Id4) suppresses MMP2 mediated invasion of glioblastoma-derived cells by direct inactivation of twist-1 function. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4931. doi:10.1158/1538-7445.AM2013-4931