Abstract 1489: Deposition of genetically engineered T cell attracting antigen presenting cells in the glioma microenvironment with low intensity pulsed ultrasound-based blood-brain barrier opening triggers therapeutic responses in preclinical glioma models
Authors: Sabbagh Aria , Beccaria Kevin , Ling Xiaoyang , Marisetty Anantha , Ott Martina , Kong Ling-Yuan , Fang Dexing , Wei Jun , Desseaux Carole , Bouchoux Guillaume , Canney Michael , Carpentier Alexandre , Heimberger Amy B. 
Published: July 2021

Abstract
Introduction: In contrast to brain metastases, gliomas have few antigen-presenting cells (APCs) in the tumor microenvironment, which may limit T cell effector responses. We hypothesized that: (1) an APC could be modified to express a T cell attracting chemokine that could enhance localized immune activation, and (2) that ultrasound-based blood-brain barrier (BBB) opening would enhance delivery of these APCs at the site of tumor antigens.
Methods: Murine F4/80 and CD11c expressing APCs were isolated from the bone marrow of C57BL/6 mice and modified via lentiviral transduction to encode the cDNA of immune cell chemokines CXCL9 or CXCL10 and methionine-deficient green fluorescent protein (co-expression) for cell tagging. C57BL/6 mice were implanted with GL261 cells and treated with 1 x 106 CXCL9 or CXCL10 over-expressing APCs intracranially (i.c.), or intravenously (i.v.) with or without ultrasound-based BBB opening. To determine how the CXCL10 expressing APCs were altering the tumor microenvironment, immune cells were isolated from the glioma implanted hemisphere of all treatment groups and analyzed by multicolor flow cytometry.
Results: Transduced APCs produced 3,392 pg/ml and 2,987 pg/ml of CXCL9 or CXCL10, respectively. Mice tolerated the treatments well without any adverse events, behavioral changes, or neurological toxicity. Survival analysis of mice treated with CXCL9 expressing APCs using i.c., or i.v. with and without BBB opening ultrasound showed no significant survival benefit compared with PBS-treated control mice. Mice treated i.c. with CXCL10-expressing APCs had significantly improved survival relative to the PBS control group (p&lt;0.05), demonstrating that this cellular therapy required access to the tumor microenvironment in order to be effective. Notably, the most therapeutically efficacious administration route was when the CXCL10-expressing APCs were administered i.v. before ultrasound-based BBB opening even relative to the i.c. administered group (p&lt;0.05). Intravenous administration of CXCL10 APCs combined with ultrasound-based BBB opening also significantly increased the percentage of T cells in the glioma microenvironment relative to all other treatment groups.
Conclusions: The delivery of CXCL10-secreting APCs to the glioma microenvironment with ultrasound-based BBB opening was superior to delivery with direct i.c. injection. BBB disruption may have triggered more diffuse dispersal of the APCs throughout the tumor microenvironment or positioned these cells in closer proximity to the T cells emigrating from the vascular space into the localized glioma microenvironment.
Citation Format: Aria Sabbagh, Kevin Beccaria, Xiaoyang Ling, Anantha Marisetty, Martina Ott, Ling-Yuan Kong, Dexing Fang, Jun Wei, Carole Desseaux, Guillaume Bouchoux, Michael Canney, Alexandre Carpentier, Amy B. Heimberger. Deposition of genetically engineered T cell attracting antigen presenting cells in the glioma microenvironment with low intensity pulsed ultrasound-based blood-brain barrier opening triggers therapeutic responses in preclinical glioma models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1489.