Mitochondrial fragmentation, elevated mitochondrial superoxide and respiratory supercomplexes disassembly is connected with the tamoxifen-resistant phenotype of breast cancer cells.
Tamoxifen resistance remains a clinical obstacle in the treatment of hormone sensitive breast cancer. It has been reported that tamoxifen is able to target respiratory complex I within mitochondria. Therefore, we established two tamoxifen-resistant cell lines, MCF7 Tam5R and T47D Tam5R resistant to 5 μM tamoxifen and investigated whether tamoxifen-resistant cells exhibit mitochondrial changes which could help them survive the treatment. The function of mitochondria in this experimental model was evaluated in detail by studying i) the composition and activity of mitochondrial respiratory complexes; ii) respiration and glycolytic status; iii) mitochondrial distribution, dynamics and reactive oxygen species production. We show that Tam5R cells exhibit a significant decrease in mitochondrial respiration, low abundance of assembled mitochondrial respiratory supercomplexes, a more fragmented mitochondrial network connected with DRP1 Ser637 phosphorylation, higher glycolysis and sensitivity to 2-deoxyglucose. Tam5R cells also produce significantly higher levels of mitochondrial superoxide but at the same time increase their antioxidant defense (CAT, SOD2) through upregulation of SIRT3 and show phosphorylation of AMPK at Ser 485/491. Importantly, MCF7 ρ0 cells lacking functional mitochondria exhibit a markedly higher resistance to tamoxifen, supporting the role of mitochondria in tamoxifen resistance. We propose that reduced mitochondrial function and higher level of reactive oxygen species within mitochondria in concert with metabolic adaptations contribute to the phenotype of tamoxifen resistance.
['Tomková|Veronika|V|', 'Sandoval-Acuña|Cristian|C|', 'Torrealba|Natalia|N|', 'Truksa|Jaroslav|J|']
D000818:Animals D018931:Antineoplastic Agents, Hormonal D017209:Apoptosis D001943:Breast Neoplasms D002453:Cell Cycle D002465:Cell Movement D049109:Cell Proliferation D019008:Drug Resistance, Neoplasm D042967:Electron Transport Complex I D005260:Female D006019:Glycolysis D006801:Humans D051379:Mice D008819:Mice, Nude D008928:Mitochondria D010641:Phenotype D017382:Reactive Oxygen Species D013481:Superoxides D013629:Tamoxifen D014407:Tumor Cells, Cultured D023041:Xenograft Model Antitumor Assays
Mitochondrial fragmentation Breast cancer Tamoxifen resistance Mitochondria Reactive oxygen species