Profiling of the immune landscape in murine glioblastoma following blood brain/tumor barrier disruption with MR image-guided focused ultrasound

J Neurooncol. 2022 Jan;156(1):109-122. doi: 10.1007/s11060-021-03887-4. Epub 2021 Nov 3.

Abstract

Purpose: Glioblastoma (GB) poses formidable challenges to systemic immunotherapy approaches owing to the paucity of immune infiltration and presence of the blood brain/tumor barriers (BBB/BTB). We hypothesize that BBB/BTB disruption (BBB/BTB-D) with focused ultrasound (FUS) and microbubbles (MB) increases immune infiltration in GB. As a prelude to rational combination of FUS with ITx, we herein investigate the impact of localized BBB/BTB-D on innate and adaptive immune responses in an orthotopic murine GB model.

Methods: Mice with GL261 gliomas received i.v. MB and underwent FUS BBB/BTB-D (1.1 MHz, 0.5 Hz pulse repetition frequency, 10 ms bursts, 0.4-0.6 MPa). Brains, meninges, and peripheral lymphoid organs were excised and examined by flow cytometry 1-2 weeks following FUS.

Results: The number of dendritic cells (DC) was significantly elevated in GL261 tumors and draining cervical LN in response to sonication. CD86 + DC frequency was also upregulated with 0.6 MPa FUS, suggesting increased maturity. While FUS did not significantly alter CD8 + T cell frequency across evaluated organs, these cells upregulated checkpoint molecules at 1 week post-FUS, suggesting increased activation. By 2 weeks post-FUS, we noted emergence of adaptive resistance mechanisms, including upregulation of TIGIT on CD4 + T cells and CD155 on non-immune tumor and stromal cells.

Conclusions: FUS BBB/BTB-D exerts mild, transient inflammatory effects in gliomas-suggesting that its combination with adjunct therapeutic strategies targeting adaptive resistance may improve outcomes. The potential for FUS-mediated BBB/BTB-D to modify immunological signatures is a timely and important consideration for ongoing clinical trials investigating this regimen in GB.

Keywords: Blood brain barrier; Focused ultrasound; Glioblastoma; Image guidance; Immune; Immunotherapy.

MeSH terms

  • Animals
  • Blood-Brain Barrier / pathology
  • Brain Neoplasms* / immunology
  • Brain Neoplasms* / pathology
  • Brain Neoplasms* / therapy
  • Glioblastoma* / immunology
  • Glioblastoma* / pathology
  • Glioblastoma* / therapy
  • Magnetic Resonance Imaging / methods
  • Mice
  • Ultrasonic Therapy*