Selective Disruption of Respiratory Supercomplexes as a New Strategy to Suppress Her2 high Breast Cancer.

Aims: Expression of the HER2 oncogene in breast cancer is associated with resistance to treatment, and Her2 may regulate bioenergetics. Therefore, we investigated whether disruption of the electron transport chain (ETC) is a viable strategy to eliminate Her2 ^high disease.
Results: We demonstrate that Her2 ^high cells and tumors have increased assembly of respiratory supercomplexes (SCs) and increased complex I-driven respiration in vitro and in vivo. They are also highly sensitive to MitoTam, a novel mitochondrial-targeted derivative of tamoxifen. Unlike tamoxifen, MitoTam efficiently suppresses experimental Her2 ^high tumors without systemic toxicity. Mechanistically, MitoTam inhibits complex I-driven respiration and disrupts respiratory SCs in Her2 ^high background in vitro and in vivo, leading to elevated reactive oxygen species production and cell death. Intriguingly, higher sensitivity of Her2 ^high cells to MitoTam is dependent on the mitochondrial fraction of Her2.
Innovation: Oncogenes such as HER2 can restructure ETC, creating a previously unrecognized therapeutic vulnerability exploitable by SC-disrupting agents such as MitoTam.
Conclusion: We propose that the ETC is a suitable therapeutic target in Her2 ^high disease. Antioxid. Redox Signal. 26, 84-103.
Competing Interests: Author Disclosure Statement J.N. and J.S. are inventors of a patent, ‘Tamoxifen analogs for treatment of neoplastic diseases, especially with high Her2 protein level’. The authors declare no additional competing financial interests.