Effects of sub-lethal high intensity focused ultrasound (HIFU) exposure on mammary epithelial tumorigenesis and cytotoxic response to anti-neoplastic agents -

Abstract

High Intensity Focused Ultrasound (HIFU) is a therapeutic modality that is used to destroy unwanted tissues including solid tumors inside the body. At the focal point where the acoustic waves are intensified, cell death can result from cavitation and-or thermal ablation effects. However, the effects of sub-lethal HIFU exposure on cell function remain to be elucidated. Given that HIFU exposure results in pressure-tension waves that can cause cellular deformations, we hypothesize that sub-lethal HIFU treatment could result in mechanotransduction alterations that may alter tumorigenesis of mammary epithelial cells and may modulate their response to anti-neoplastic agents. The objective of this study is to examine the alterations in mechanotransduction due to changes in the physical properties resulting from the exposure of MDA-MB-231 breast cancer cells and MCF-10A immortalized mammary epithelial cells to ultrasonic waves from a custom-designed HIFU setup and to determine consequences on cellular response to anti-neoplastic agents. Combined with data from a previous study, we had assessed the in vitro effects of sub-lethal HIFU exposure on the expression of sevenmechanosensitive genesnamely CAV-1 (Caveolin-1 α and β), Hic-5 (Hydrogen Peroxide-Inducible Clone 5), PXN (Paxillin), TTLL4 (Tubulin-Tyrosine Ligase-Like Protein 4), TWIST1 (Twist-Related Protein 1), CTSD (Cathepsin D), and HSPA1A (Heat Shock Protein 70) whereby we quantified significant enhanced expression of CAV-1, PXN, and Hic-5 that was immediate-early in MCF-10A cells and delayed in MDA-MB-231 Cells. Additionally, we noted an immediate -early transient increase in TTLL4 expression in both cell lines and in TWIST1 expression in MDA-MB-231 cells. Notably, sub-lethal HIFU exposure had no significant effect on the expression of CAV-1(total pool), CTSD, and HSPA1A in both cell lines. Moreover, sub-lethal HIFU exposure of cells at 6hr or 30hr prior to the in vitro addition ofanti-neoplastic agents sensitized MDA-MB-231 and MCF-10A cells to s