Abstract 5844: Initial findings on the immunomodulatory effects of histotripsy combined with N-dihydrogalactochitosan in a comparative oncology model of canine osteosarcoma
Authors: Ny Luong, Alayna Hay, Elliana Vickers, Samuel S. Lam, Wei R. Chen, Eli Vlaisavljevich, Joanne Tuohy
Journal: Cancer Research (2025)

Abstract Background: Osteosarcoma (OS) is the most common primary malignant bone tumor in children and adolescents, associated with poor prognosis, especially in cases with metastatic disease at diagnosis. Canine OS shares many biological and clinical similarities with human OS, making dogs valuable comparative models for OS research. Histotripsy is a non-thermal, non-invasive high-intensity focused ultrasound modality that mechanically disrupts tumor cells, triggering the release of neoantigens and damage-associated molecular patterns (DAMPs) to potentially promote an anti-tumor immune response. N-dihydrogalactochitosan (GC) is a novel immunostimulant shown to enhance systemic immune responses when delivered intratumorally after thermal ablation. However, the combination of GC with a non-thermal ablation modality such as histotripsy remains unexplored. This study evaluates the safety, feasibility, and immunomodulatory effects of combining histotripsy with GC in pet dogs with spontaneous OS. Methods: Pet dogs with spontaneous OS were treated with a 700 kHz histotripsy system at a1000 Hz pulse repetition frequence and 500-750 pulses/point. Patients underwent 1-5 fractionated histotripsy treatments , ablating the majority of the tumor. After the final histotripsy treatment, GC (10 mg/mL) was injected intratumorally under ultrasound guidance, with the dose proportional to tumor size. Peripheral blood was collected at baseline and 2-, 4-, and 8-weeks post-histotrispy+GC treatment and peripheral blood mononuclear cells (PBMCs) were isolated and immune cell signatures were characterized, serum cytokines and chemokines profiles were evaluated using a Milliplex Canine Cytokine Panel. At the follow up timepoints lung metastases were monitored via thoracic radiographs. Results: The combination of histotripsy and GC was tolerated, with swelling at the treatment site resolving within one week. At 2 weeks post-treatment, circulating monocytes (CD11b+CD14+) increased with upregulation of CD80 and CD62L expression compared to baseline level. Although the percentage of gated CD11b+CD14+CD80+ monocytes remained stable after two weeks, CD80 expression continued to increase, suggesting sustained monocyte activation. CD62L expression on CD4+ and CD8+ T cells decreased at 2 weeks but increased again by 4 weeks post treatment, potentially reflecting changes in T cell trafficking. Two of three patients remained free of lung metastases at 10 weeks post treatment. Cytokine and gene expression analyses are ongoing and will further inform systemic immune responses. Conclusion: These preliminary findings suggest that histotripsy combined with GC may induce immune activation and holds promise as a therapeutic strategy for targeting primary tumors and metastases in OS. Citation Format: Ny Luong, Alayna Hay, Elliana Vickers, Samuel S. Lam, Wei R. Chen, Eli Vlaisavljevich, Joanne Tuohy. Initial findings on the immunomodulatory effects of histotripsy combined with N-dihydrogalactochitosan in a comparative oncology model of canine osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5844.