It has been reported that, under chronic energy deprivation, mitochondrial activity is enhanced in muscle cells.17,22 CPT1C, a mitochondrial enzyme, has been shown to maintain survival of breast cancer cells treated with metformin under metabolic stress.36 Interestingly, mitochondrial biogenesis and its function are elevated in response to chronic energy deprivation in muscle.17 In agreement with these findings, we report that mitochondrial activity is enhanced in cancer cells under glucose-limiting conditions. Here, CPT1C is linked to breast cancer.