CASP3 and neoplasm: To assess ROS levels in circulating tfRFP-B16 cells, especially those passing through hepatic sinusoids under fluid shear stress from blood flow 35, we screened B16 tumor cells stably expressing the mitochondria localized-ROS probe (MLS-HyPer7-B16 cells) and tfRFP-B16 tumor cells stably expressing the caspase-3 probe (tfRFP-C3-B16 cells).