Kang, Jeonghan

Abstract Malignant primary brain tumors represent one of the most common causes of cancer death in the world. Grade IV gliomas (glioblastoma multiform, GBM) are routinely resistant to current chemoradiationchemo radiation therapy with a median progression-free and overall survival for glioblastoma following current chemoradiation of ~7 and 15 months, respectively. While TGF-β functions as a growth inhibitor for most normal cell types, many tumors (including GBMs) have lost this inhibitory response and TGF-β now functions to promote tumor progression and/or dissemination. As aberrant TGF-β signaling is often considered a hallmark of high-grade gliomas, we examined whether inhibition of specific components would impact the malignant phenotype of glioblastoma. The primary mediators of TGF-β action are the Smad proteins (R-Smads), Smad2 and Smad3. Following receptor activation and R-Smad phosphorylation, they translocate to the nucleus to modulate gene expression. Since we previously determined that a cell penetrating peptide conjugate of the HIV TAT protein fused to a 30 amino acid sequence from sorting nexin 9 (SNX9) prevented Smad3, but not Smad2, nuclear import and target gene expression in models of organ fibrosis, we further investigated whether it might similarly impact aspects of GBM proliferation. To that end, twenty-one patient-derived xenografts (PDXs) were examined for their responsiveness to TGF-β. Of those, TGF-β stimulated migration and fibronectin expression in seven (33%), which was prevented by inhibiting Smad3 signaling with the TAT-SNX9 peptide but not a control peptide unable to block Smad3 action. These findings indicate that the TGB-b/Smad3 axis is a potentially important mediator of glioma cell invasion in a significant minority of GBM models. specifically targeting Smad3 might be effective in a subset of gliomas. This work was supported by Public Health Service grants GM-055816 and GM-054200 from the National Institutes of General Medical Sciences and P50 CA-108961 Developmental Pilot Award from the National Cancer Institute. Citation Format: Jeonghan Kang. Inhibition of Smad3 signaling with a TAT fusion peptide prevented TGF-β-induced fibronectin expression and cell migration in malignant gliomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 354. doi:10.1158/1538-7445.AM2017-354