Energy Metabolism Drugs Block Triple Negative Breast Metastatic Cancer Cell Phenotype

To establish alternative targeted therapies against triple negative (TN) breast cancer, the energy metabolism and the sensitivity of cell growth, migration, and invasiveness toward metabolic, canonical, and NSAID inhibitors were analyzed in MDA-MB-231 and MDA-MB-468, two TN metastatic breast cancer cell lines, under both normoxia (21% O₂) and hypoxia (0.1% O₂). For comparative purposes, the analysis was also carried out in the less-metastatic breast MCF-7 cancer cells. Under normoxia, oxidative phosphorylation (OxPhos) was significantly higher (2-times) in MDA-MB-468 than in MDA-MB-231 and MCF-7, whereas their glycolytic fluxes and OxPhos and glycolytic protein contents were all similar. TN cancer cell lines mainly depended on OxPhos (62-75%), whereas MCF-7 cells equally depended on both pathways for ATP supply. Hypoxia for 24 h promoted a significant increase (>20 times) in the glycolytic transcriptional master factor HIF1-α in its target proteins GLUT-1, HKI and II, and LDH-A (2-4 times) as well as in the glycolytic flux (1.3-2 times) vs normoxia in MDA-MB-468, MDA-MB-231, and MCF-7. On the contrary, hypoxia decreased (15-60%) the contents of COXIV, 2OGDH, ND1, and ATP synthase as well as the OxPhos flux (50-75%), correlating with a high mitophagy level in the three cell lines. Under hypoxia, the three cancer cell lines mainly depended on glycolysis (70-80%). Anti-mitochondrial drugs (oligomycin, casiopeina II-gly, and methoxy-TEA) and celecoxib, at doses used to block OxPhos, significantly decreased TN cancer cell proliferation (IC₅₀ = 2-20 μM), migration capacity (10-90%), and invasiveness (25-65%). The present data support the use of mitochondrially targeted inhibitors for the treatment of TN breast carcinoma.