Immunomodulation of intracranial melanoma in response to blood-tumor barrier opening with focused ultrasound.

Authors: Curley CT, Stevens AD, Mathew AS, Stasiak K, Garrison WJ, Miller GW, Sheybani ND, Engelhard VH, Bullock TNJ, Price RJ

Background: Focused ultrasound (FUS) activation of microbubbles (MBs) for blood-brain (BBB) and blood-tumor barrier (BTB) opening permits targeted therapeutic delivery. While the effects of FUS+MBs mediated BBB opening have been investigated for normal brain tissue, no such studies exist for intracranial tumors. As this technology advances into clinical immunotherapy trials, it will be crucial to understand how FUS+MBs modulates the tumor immune microenvironment. Methods and Results: Bulk RNA sequencing revealed that FUS+MBs BTB/BBB opening (1 MHz, 0.5 MPa peak-negative pressure) of intracranial B16F1cOVA tumors increases the expression of genes related to proinflammatory cytokine and chemokine signaling, pattern recognition receptor signaling, and antigen processing and presentation. Flow cytometry revealed increased maturation (i.e. CD86) of dendritic cells (DCs) in the meninges and altered antigen loading of DCs in both the tumor and meninges. For DCs in tumor draining lymph nodes, FUS+MBs had no effect on maturation and elicited only a trend towards increased presentation of tumor-derived peptide by MHC. Neither tumor endothelial cell adhesion molecule expression nor homing of activated T cells was affected by FUS+MBs. Conclusion: FUS+MBs-mediated BTB/BBB opening elicits signatures of inflammation; however, the response is mild, transient, and unlikely to elicit a systemic response independent of administration of immune adjuvants.

Introduction

Purpose Drug delivery with BBB opening

Study Objective To determine how focused ultrasound with microbubbles (FUS+MBs) BTB/BBB opening modulates the immune microenvironment of intracranial melanoma brain tumors, meninges, and draining lymph nodes.

Disease model Intracranial melanoma brain tumor (B16F1cOVA)

Targeted brain region(s) Intracranial B16F1Cova Tumor

Outcomes and Safety

Summary of Outcomes FUS+microbubble BTB/BBB opening produced a mild, transient proinflammatory response in intracranial B16 melanoma (upregulation of TNF, IL-6, chemokines, PRR and antigen‑processing/MHC I genes), increased meningeal DC maturation (CD86) and tumor DC antigen uptake/presence, but did not increase endothelial adhesion‑molecule protein expression or enhance activated T cell homing. Successful FUS+MBs parameters used were ~1–1.1 MHz, 0.5 MPa peak‑negative pressure with 0.5% duty cycle (with microbubbles), which achieved BTB/BBB opening.

Duration of biological effect 24 hours

Safety-related matter FUS+MBs was applied at 0.5 MPa (~1–1.1 MHz), which the authors state is within the safe (stable cavitation) range; the treatment elicited only a mild, transient proinflammatory response and the authors report no overt adverse effects observed (no protein-level upregulation of endothelial adhesion molecules, no acute leukocyte recruitment, and no increased homing of activated T cells), suggesting no safety concerns in this mouse tumor model.

Brain Region

Ultrasound Parameters

FUS Frequency 1 MHz

FUS Pressure 0.5 MPa

Focal Characteristics focal depth: None; focal length: None; aperture size: None

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