In sonodynamic therapy, sound energy is used to activate chemical agents that perfuse into tumors. When activated, the chemical agents generate oxygen free radicals, which damages the tumor cells’ DNA and induces cell death. Focused ultrasound may be able to activate these chemical “sonosensitizers.” One such agent is 5-aminolevulinic acid (5-ALA), which is an innocuous dye that is injected intravenously and absorbed preferentially by tumor cells. Researchers from the department of Neurosurgery in the Graduate School of Medicine at Hokkaido University in Sapporo, Japan, investigated whether a 220-kHz transcranial focused ultrasound system could successfully induce apoptosis (or cell death) in a rat model of malignant glioma. Not only did the focused ultrasound/5-ALA combination induce cell death and reduce cell viability, it also suppressed tumor proliferation and invasion. Pathology revealed minimal damage to normal brain tissue. See Ultrasound in Medicine and Biology >
Using histotripsy to non-thermally ablate tumors in a rat model of kidney cancer, researchers at the University of Washington found well-tolerated tumor de-bulking but also an acute systemic inflammatory response. The inflammatory response included significant increases in relative concentrations of plasma tumor necrosis factor and transient elevations in cytokines (e.g., HMGB1, IL-10, and IL-6), including intrarenal cytokines. At 48 hours after ablation, the team also observed enhanced infiltration of cytotoxic T cells in both the treated and un-treated kidneys. See Ultrasound in Medicine and Biology >