An EPR Study Using Cyclic Hydroxylamines to Assess the Level of Mitochondrial ROS in Superinvasive Cancer Cells

It has been proposed that a mitochondrial switch involving a high mitochondrial superoxide production is associated with cancer metastasis. We here report an EPR analysis of ROS production using cyclic hydroxylamines in superinvasive SiHa-F3 compared with less invasive SiHa wild-type human cervix cancer cells. Using the CMH probe, no significant difference was observed in the overall level of ROS between SiHa and SiHa-F3 cells. However, using mitochondria-targeted cyclic hydroxylamine probe mitoTEMPO-H, we detected a significantly higher mitochondrial ROS content in SiHa-F3 compared with the wild-type SiHa cells. To investigate the nature of mitochondrial ROS, we overexpressed superoxide dismutase 2, a SOD isoform exclusively localized in mitochondria, in SiHa-F3 superinvasive cells. A significantly lower signal was detected in SiHa-F3 cells overexpressing SOD2 compared with SiHa-F3. Despite some limitations discussed in the paper, our EPR results suggest that mitochondrial ROS (at least partly superoxide) are produced to a larger extent in superinvasive cancer cells compared with less invasive wild-type cancer cells.