High-intensity focused ultrasound is synergistic with anti-neoplastic drugs that target endoplasmic reticulum stress

Abstract

Previous studies from our laboratory show that combination of High-Intensity Focused Ultrasound (HIFU) and anti-neoplastic agents not only reduces cellular viability and proliferation, but also shifts cellular populations to late apoptotic/necrotic stages. Nelfinavir, a well-tolerated HIV protease-inhibitor, is known to increase endoplasmic reticulum (ER) stress, and is thus being repurposed as an anti-neoplastic agent. This led us to combine Nelfinavir with HIFU in order to create a safe and more effective treatment for patients with prostate cancer. 2.7 million cells/ml suspensions of DU145 and C4-2B prostate cancer cells were placed in PCR tubes and split into 4 treatment groups: Control, HIFU alone, Nelfinavir(2μM) alone, and Nelfinavir(2μM) + HIFU. HIFU treatment was applied for 30 seconds at an acoustic output power of 8.7 W. Apoptosis and necrosis of cells was measured via AnnexinV/PI staining, cell proliferation was measured by a WST-8 assay, and ROS was stained using cellular ROS detection assay kit. The population percentage of Late Apoptotic/Necrotic cells and ROS production was found to be significantly greater, while proliferation rate was significantly reduced post exposure to Nelfinavir + HIFU 24 and 72h post treatment. HIFU and Nelfinavir have a synergistic effect on both increasing cellular death via apoptosis/necrosis and decreasing proliferation in vitro.