Abstract LB-343: Integrative functional genomic analysis identifies epigenetically regulated fibromodulin as an essential gene for glioma cell migration
Authors: Mondal Baisakhi 
Published: July 2016

Glioblastoma (GBM), the grade IV astrocytoma, is the most malignant form of glioma with a median survival of 15 months approximately. In spite of all the progress in the fields of treatments, the prognosis of GBM still remains very poor. One of the major reasons why GBM is resistant to various therapeutic modalities is its diffused nature which makes it difficult to accurately identify the tumor margin by MRI. This makes the complete tumor resection impossible. Thus, it is important to study the molecules regulating cell migration and invasion for better understanding and developing targeted therapies in GBM.

In this study, we present an integrated genomic and epigenomic strategy utilizing genome-wide DNA methylation and transcriptome profile data to ascertain epigenetically regulated genes implicated in cancer development and invasive progression. This analysis identified Fibromodulin (FMOD) as a GBM upregulated gene due to the loss of promoter methylation. FMOD, a member of small leucine-rich repeat proteoglycan, is an extracellular matrix protein and its C-terminus is known to interact with collagen fibrils aiding in the proper formation of extracellular matrix. Secreted FMOD (full length), not ΔFMOD (lacks C-terminal domain that interacts with collagen), promotes glioma cell migration through its ability to induce

ilamentous actin stress fiber formation. A 9-mer synthetic peptide (either wild type or mutant) against FMOD C-terminal domain was used to compete with full length FMOD to assess the effect on migration phenotype. We observed that the wild type 9-mer peptide was able to decrease FMOD-induced migration completely but not the mutant peptide thereby indicating that the secreted FMOD induces migration by its interaction with collagen fibrils, a ligand for integrins. siRNA and small molecule inhibitor-based studies identified that FMOD-induced glioma cell migration is dependent on Integrin-FAK-Src-Rho-ROCK signaling pathway. ChIP-PCR experiments revealed that TGF-β1 regulates FMOD expression through epigenetic remodeling of FMOD promoter that involved demethylation and gain of active histone marks with a simultaneous loss of DNMT3A and EZH2 occupancy, but with an enrichment of SMAD2 and CBP. FMOD silencing inhibited the TGF-β1 mediated glioma cell migration significantly. In univariate and multivariate cox regression analysis, both FMOD promoter methylation and transcript levels predicted prognosis in GBM. To summarize, we found secreted FMOD as an important regulator of glioma cell migration downstream of TGF-β1 pathway and forms a potential basis for therapeutic intervention in GBM.

Citation Format: Baisakhi Mondal. Integrative functional genomic analysis identifies epigenetically regulated fibromodulin as an essential gene for glioma cell migration. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-343.