HIFU Thermal Ablation in Breast Cancer Cells: Monolayers vs. Spheroids

ObjectiveThe primary objective of our study was to investigate the efficiency of high intensity focused ultrasound (HIFU) ablation in two distinct cellular configurations, 2D monolayers and 3D spheroids of epithelial breast cancer cell lines. The study also compares empirical findings from experiments with results obtained through numerical simulations using a bioheat computational model. This comparison is intended to provide a comprehensive understanding of the acoustic energy conversion within the biological system during HIFU treatment. MethodsHIFU was applied to 2D and 3D cultured MDA-MB 231 and MCF7 epithelial breast cancer cell lines while systematically varying ultrasound intensity and duty cycle (DC) during sonication sessions of different durations. Temperature elevation was measured and the ablation percentage was calculated based on bright field and fluorescent imaging of the treated regions. Experimental results were validated through simulations of the ablation setup. ResultsUpon HIFU, spheroids exhibited a lower temperature increase (approximately 20 {degrees}C) when subjected to comparable acoustic intensities and duty cycles. The level of tumor ablation was highly influenced by DC, with higher DCs leading to greater ablation percentages. However, sonication duration had a minimal impact on the degree of ablation. Numerical simulations corroborated these observations, demonstrating uniform heat distribution within the cultured cells. At higher DCs and intensities, complete ablation of spheroids was achieved, whereas at lower levels, only the outermost layers exhibited ablation. ConclusionOur study reveals a significant disparity in the response of 2D monolayers and 3D spheroids to HIFU treatment. Specifically, tumor spheroids require lower temperature elevations for effective ablation, and their ablation percentage significantly increases with elevated DC.