Lactate treatment of estrogen receptor-positive breast cancer cells drives mitochondrial biogenesis, leading to poor survival in a subset of luminal A breast cancer patients. (a) Lactate-treated (10 mM) MCF7 cells show a significant increase in mitochondrial mass, as visualized by staining with antibodies against mitochondrial marker proteins. (b) Lactate-treated (10 mM) MCF7 cells were subjected to transcriptional profiling (exon-array) to generate a gene signature. Interestingly, this lactate-induced gene signature predicts poor clinical outcome in estrogen receptor-positive/luminal A breast cancer patients, which represent nearly 60 to 70% of cases, and is the most common type of breast cancer. Modified and reproduced with permission from .