MCU-i4, a mitochondrial Ca uniporter modulator, induces breast cancer BT474 cell death by enhancing glycolysis, ATP production and reactive oxygen species (ROS) burst.

Objectives: Mitochondrial Ca uniporter (MCU) provides a Ca influx pathway from the cytosol into the mitochondrial matrix and a moderate mitochondrial Ca rise stimulates ATP production and cell growth. MCU is highly expressed in various cancer cells including breast cancer cells, thereby increasing the capacity of mitochondrial Ca uptake, ATP production, and cancer cell proliferation. The objective of this study was to examine MCU inhibition as an anti-cancer mechanism.

Methods: The effects of MCU-i4, a newly developed MCU inhibitor, on cell viability, apoptosis, cytosolic Ca, mitochondrial Ca and potential, glycolytic rate, generation of ATP, and reactive oxygen species, were examined in breast cancer BT474 cells.

Results: MCU-i4 caused apoptotic cell death, and it decreased and increased, respectively, mitochondrial and cytosolic Ca concentration. Inhibition of MCU by MCU-i4 revealed that cytosolic Ca elevation resulted from endoplasmic reticulum (ER) Ca release via inositol 1,4,5-trisphosphate receptors (IP3R) and ryanodine receptors (RYR). Unexpectedly, MCU-i4 enhanced glycolysis and ATP production; it also triggered a large production of reactive oxygen species (ROS) and mitochondrial membrane potential collapse.

Conclusion: Cytotoxic mechanisms of MCU-i4 in cancer cells involved enhanced glycolysis and heightened formation of ATP and ROS. It is conventionally believed that cancer cell death could be caused by inhibition of glycolysis. Our observations suggest cancer cell death could also be induced by increased glycolytic metabolism.