Abstract 575: Brain delivery of clinically suitable nanobioconjugates to inhibit glioblastoma growth through extracellular matrix-immune cell crosstalk

Abstract Introduction: Tumor growth, invasion, and escape from immune surveillance largely depend on cancer microenvironment. Laminins are trimeric proteins and essential components of glioblastoma (GBM) microenvironment/extracellular matrix (ECM). In brain glioma samples from 230 patients, we found a correlation between the overexpression of tumor ECM protein laminin-411 (α4β1γ1) and faster tumor recurrence with shorter patient survival. Laminin-411 is produced by endothelial cells, neutrophils, monocytes, platelets, lymphocytes, and glioma cells and can modulate the immune system. Novel nanotechnology approach to block trimeric laminin-411 and activate of brain local immune system with brain delivery of PD-1 checkpoint inhibitor was developed for future translational application. Methods: Nanobioconjugates (NBC) based on poly (β-L-malic acid, P), were synthesized, characterized and used to intravenously treat mice with intracranial syngeneic GL261 or CT-2A GBM. The lead NBCs P/PEG/LLL(40%)/AON(α4β1)(2.0%)/AP-2(2%) and P/PEG/LLL(40%)/AP-2(2%)/αPD-1(0.2%) contained antisense to laminin-411 α4 and β1 chains, or αPD-1 antibody as well as trileucine (LLL) peptide for endosomal escape and AP-2 peptide for BBB crossing and tumor cell targeting. CRISPR/Cas9 constructs were used to knockdown α4 and β1 laminin chains in GBM ex vivo. Flow cytometry and RNA-seq analyses were performed to evaluate treatment. Results: Laminin-411 depletion with CRISPR/Cas9 and multifunctional NBC in vivo treatment equally suppressed GBM growth and significantly prolonged animal survival. The brain privileged immune system was activated upon treatment with a significant increase of CD3+, CD8+ T cells, NK, IFNγ+ NK cells, and M1 macrophages. RNA-sec analyses after treatment with a combination of NBC suppressing laminin-411 and checkpoint PD-1 showed enhanced anti-tumor effect with upregulation of genes coding for apoptotic Caspase 3 and IFNγ, and reduction of proliferation markers EGFR, c-Myc and Ki-67. Conclusion: Study describes novel GBM treatment strategy via NBCs crossing blood-brain barrier and targeting critical ECM and immune components of tumor microenvironment largely independent of heterogeneous genetic mutations in glioblastoma. Citation Format: Alexander V. Ljubimov, Rameshwar Patil, Hui Ding, Liron Israel, Eggehard Holler, Julia Y. Ljubimova, Tao Sun, Keith L. Black. Brain delivery of clinically suitable nanobioconjugates to inhibit glioblastoma growth through extracellular matrix-immune cell crosstalk [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 575.