Histotripsy significantly decreases tumor viability in neuroblastoma xenograft model

Abstract

Children diagnosed with high-stage neuroblastoma (NB) have a <50% 5-year survival rate, resisting intensive treatment. Histotripsy, a focused ultrasound method, can ablate subcutaneous tumors. Here, we characterize histotripsy in an abdominal NB-xenograft model.Intrarenal injection of NGP-Luciferase cells in female NCr Nude mice generated 1–2 g NB tumors after 5–6 weeks. We assessed tumor viability with bioluminescence before, after, and 24h after Histotripsy. A 1-MHz focused source under ultrasound image guidance delivered 4–6 pulses per tumor with individual targets separated by ∼1 mm. Immunostains of the apoptosis marker TUNEL, endothelial marker Isolectin-B4, and hypoxia-marker pimonidazole were imaged or scanned. Statistics were performed using Graphpad.Histotripsy decreased bioluminescence by ∼50% (p = 0.02, n = 7), suggesting a decrease in viability. Untreated tumors did not change (n = 4). TUNEL staining increased in Histotripsy-treated tumors compared to controls (56 ± 6 versus 9 ± 3 %area, n = 3 to 8, p < 0.0001). Histotripsy increased pimonidazole positivity adjacent to targeted areas, suggesting hypoxia. Finally, Histotripsy increased red blood cells compared to controls. Histotripsy dramatically reduces tumor viability by inducing apoptosis of targeted areas. Hypoxia patterns suggest histotripsy alters perfusion and/or permeability within the tumor, indicating potential for synergy with chemotherapy.