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Glioblastoma multiforme (GBM) is an aggressive tumor with 14.6 months median survival rate. We have previously shown that laminin-411, a vascular basement membrane (BM) protein is a marker of tumor blood vessels that correlates with aggressiveness of GBMs. The laminin-411 pathway involving its β1 chain-containing integrin receptors, and ligand Dll4 for cancer stem cell (CSC) Notch1 was studied in mouse xenograft models to better understand glial tumor growth and new vasculature system development. To confirm the importance of laminin-411 expression for GBM progression and outcome prediction, sections from formalin-fixed paraffin embedded human brain tumors were studied. Immunohistochemical analysis of 107 GBM samples has revealed 87% cases with overexpression of laminin-411, whereas it was only 34% for high-grade (III) and 10.6% for low-grade (I/II) gliomas. The median survival for patients with GBM overexpressing laminin-411 was 10 months, compared to 20.2 months for those expressing “normal” laminin-421. The median recurrence rate was 5.6 and 9.3 months respectively. Morphometric analysis of CSC Notch1, nestin, CD133, and c-myc was correlated with laminin-411 overexpression in patients with high-grade gliomas. Nanobioconjugate PolycefinTM was synthesized to block BM laminin-411 in mice bearing intracranial human U87MG-derived GBM. Two antisense oligonucleotides against laminin-411 α4 and β1 chains were covalently attached on polymalic acid nanoplatform. The nanodrug, PolycefinTM, was able to cross blood brain tumor barrier and delivered drugs into cancer cells (Ding et al. 2010, 2013) using pH-dependent endosome releasing unit Leu-Leu-Leu. Evidence of cross talk was observed between BM, CSCs and tumor proliferation when mice were treated with PolycefinTM. It is shown that blocking synthesis of laminin-411 leads to significally lower tumor expression of integrin β1 chain, Notch ligand Dll4, and Notch1. The CSC markers nestin, CD133, and c-myc that are known indicators of glial tumor progression also showed quantitative reduction by morphometric analysis in tumors of mice treated with anti-laminin-411 Polycefin compared to PBS-treated animals. The data point to the importance of laminin-411-integrin β1-Dll4-Notch1 pathway in GBM development and to the ability of Polycefin to negatively impact CSC as a possible mechamism of GBM inhibition. The results provide new insights in glioma microenvironment and tumor endothelial and parenchymal cell signaling suggesting a novel approach for future therapeutics to target CSCs in vivo through inhibition of laminin-411 to treat highly infiltrating GBMs. Citation Format: Pallavi R. Gangalum, Alexander V. Ljubimov, Alexandra Chesnokova, Bindu Konda, Hui Ding, Jose Portilla-Arias, Adam Mamelak, Serguei Bannykh, Surasak Phuphanich, Jeremy Rudnick, Jethro Hu, Keith L. Black, Julia Y. Ljubimova. Nanoconjugates for inhibition of laminin-411-integrin β1-Dll4-Notch1 pathway to treat glioblastoma multiforme. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2692. doi:10.1158/1538-7445.AM2014-2692