Triphenylphosphonium (TPP) conjugated agents induce mitochondrial dysfunction in cancer cells. However, the onset of mitophagy to remove the dysfunctional mitochondria is unknown. Here, a series of mitochondria targeted redox active agents (MTA) that contain TPP were used to investigate mitochondrial dysfunction and mitophagy in MDA-MB-231 cells as compared to MCF-12A cells. Three different MTAs were identified to induced mitochondrial depolarization and enhanced autophagic flux selectively in MDA-MB-231 cells. Mitochondrial reactive oxygen species generation and respiration indicated that MDA-MB-231 cells had a heighten sensitivity to MTA treatments. Using stably expressing mt-mKeima MDA-MB-231 and MCF-12A cell lines, a non-cell type selective decline in mitochondrial alkalinity and altered mitochondrial morphology was detected. Furthermore, FACS analysis of mt-mKeima revealed MTAs induced lysosomal dependent mitochondrial degradation in the presence of Bafilomycin, a lysosomal inhibitor. To confirm MTAs induced mitochondrial autophagy in MDA-MB-231 cells, MitoTracker Red preloaded GFP-LC3 expressing MDA-MB-231 cells were used to identify autophagosomes containing mitochondria using confocal microscopy, in addition to coimmunoprecipitation for the detection of an endogenous autophagy-related protein complex, and immunoblot to for mitochondrial PINK1 accumulation. To translate these in vitro studies to an in vivo rat SST-2 xenograph breast cancer model, tumor mitochondrial extracts from rats treated with MitoQ demonstrated an accumulation of mitochondrial PINK1. Collectively, these data suggest that mitochondrial agents selectively caused mitochondrial depolarization, PINK1 accumulation and mitophagy in MDA-MB-231 cancer cells as compared to MCF-12A healthy cells.

Citation Format: Thomas Biel, Ashutosh Rao. Breast cancer cells treated with mitochondria targeted redox active agents induce mitophagy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1505. doi:10.1158/1538-7445.AM2017-1505