Investigating the effects of residual high intensity focused ultrasound exposure on cellular viability and mechanosensitive gene expression in MCF-10A and MDA-MB-231 human mammary epithelial cells

Abstract

High Intensity Focused Ultrasound (HIFU) is a non-invasive therapeutic modality that allows the ablation of unwanted tissues inside the body. In recent years, HIFU gained significant attention for its potential applications in the treatment of multiple disorders including breast cancer. At the focal spot, intensified energy results in immediate cell death due to instantaneous temperature rise or-and cavitation effects in the target tissue. The surrounding tissue, though routinely receives residual energy, is believed to be left undamaged. Considering that HIFU exposure results in pressure-tension waves which can potentially cause transient cellular deformations in exposed tissue due to altered mechanotransduction and that a number of mechanosensitive genes have been shown to be implicated in tumorigenesis, we hypothesize that sub-lethal HIFU treatment would result in mechanotransduction alterations that may induce tumorigenesis of mammary epithelial cells. The objective of this study is to investigate the in vitro effects of residual HIFU exposure on cellular viability and mechanosensitive gene expression in mammary epithelial cells. We are particularly interested in probing the effects of sub-lethal HIFU loading on CAV-1 α, PXN, Hic-5 and TTLL4. An experimental setup was custom-designed and manufactured to permit utilization of a 2.158 MHz HIFU transducer for in vitro exposure of MCF-10A and MDA-MB-231cells. Cellular viability and proliferation were assessed days 1-to-4 post HIFU treatment. Our results show a highly significant decrease in cellular viability and proliferation of MCF-10A and MDA-MB-231cells exposed at the focal spot in comparison to mock controls. However, under the experimental parameters of 2.5percent and 22percent residual ultrasound intensity, we find no significant difference in MCF-10A cellular viability and proliferation in comparison to the mock controls. Real-Time PCR quantification of CAV-1α, PXN, Hic-5 and TTLL4 gene expression in MCF-10A cells that were mechanically loaded with 2.5percent