Histotripsy-induced vascular remodeling in the tumor microenvironment enhances local and off-target intratumoral drug delivery

Solid tumors pose significant challenges in treatment due to their poor vascularization, which impedes immune cell access and drug distribution. A non-invasive ultrasound technique called histotripsy has been shown to disrupt these tumors, reducing hypoxia and boosting anti-tumor immune reactions. In this research, the scientists sought to determine if the post-histotripsy decrease in hypoxia and increase in cytotoxic immune cells correspond to a normalization of tumor blood vessels and improved circulation.

Upon examining both the treated and nearby off-target tumors, the researchers observed substantial vascular remodeling, stronger vessel walls, and reduced vessel permeability in various melanoma, liver, and pancreatic cancer models following partial histotripsy. These changes seemed to be specific to the targeted tumor type, not affecting unrelated tumors.

The underlying mechanism appears to involve the infiltration of CXCR3+CD8+ T cells, which, when genetically removed or chemically inhibited, prevented both vascular remodeling and normalization. Furthermore, histotripsy altered the expression of endothelial receptors CXCR4 and Angiopoietins-1 and -2, which may play a crucial role in promoting vascular normalization and remodeling.

The vascular changes following histotripsy were associated with increased blood flow and improved intratumoral delivery of chemotherapy drugs and targeted antibody therapies. These findings suggest that histotripsy may not only foster a more favorable environment for immune-based treatments but also improve the efficacy of conventional chemotherapy in solid tumors.

The authors propose that using histotripsy in combination with chemotherapy or immunotherapy could represent a groundbreaking therapeutic approach to address the limitations of current solid tumor treatments.