Focused Ultrasound Blood-Tumor Barrier Opening Rapidly Augments Intratumor CD4 and CD8 T Cell Representation in a Genetically Engineered Mouse Model of Glioma

Abstract

Glioblastoma (GBM) is a highly aggressive primary brain tumor that remains difficult to treat due in part to its disorganized and heterogeneous vasculature, known as the blood-tumor barrier (BTB), which limits therapeutic delivery and beneficial immune cell infiltration. Focused ultrasound (FUS) with microbubbles (MBs) can transiently disrupt the BTB to enhance drug delivery and may induce sterile inflammation (SI) that can beneficially remodel the tumor immune landscape. However, this concept has only been explored in implanted tumor models with modest immune effects. Here, we utilized a physiologically relevant genetically engineered mouse model (GEMM) generated via in utero electroporation targeting Nf1, Tp53, and Pten to study tumor-vascular-immune interactions. This 3x CRISPR-Cas9 GEMM recapitulates key features of human glioma, including infiltrative growth, histopathology, molecular alterations, and stage-dependent blood-brain barrier disruption. FUS+MBs were applied to transiently disrupt the BTB, and MRI confirmed increased vascular permeability in treated tumors. Flow cytometry revealed robust increases in tumor-infiltrating CD4+ helper and CD8+ effector T cells three days post-FUS treatment, without altering the CD8/Treg ratio. These findings were supported by immunofluorescence imaging. Double-negative and double-positive T cells were detected, but they were not significantly altered by FUS. Ki67 analysis indicated that increased T-cell accumulation was not driven by local proliferation. By seven days post-treatment, immune differences were no longer observed. Collectively, these results demonstrate that FUS-mediated BTB disruption selectively and rapidly enhances lymphocyte infiltration in a clinically relevant glioma model, supporting its potential as a temporally controlled immunomodulatory strategy for GBM.