Effect of Bifidobacterium -induced changes in tumor tissue acoustic properties on efficacy of high-intensity focused ultrasound ablation

To investigate the effects of on the acoustic characteristics of tumor tissue and how such acoustic changes affect the efficacy of high-intensity focused ultrasound (HIFU) ablation in nude mice. Forty mice bearing human breast cancer cell (MDA-MB-231) xenograft were randomized into experimental group ( =20) and control group ( =20) for intravenous injection of suspension (200 μL, 4 × 10 cfu/mL) and PBS (200 μL) for 3 consecutive days, respectively. Before and at 3 and 7 days after the first injection, shear wave elastography was used to evaluate the hardness of the tumor tissue. On day 7 after the first injection, 10 mice from each group were sacrificed and the sound velocity and sound attenuation of the tumor tissues were measured. The changes in the collagen fibers in the tumors were evaluated using Masson staining, and neovascularization in the tumor was assessed with immunohistochemistry for platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31). The remaining 10 tumor-bearing mice in each group wer