In a recent study with breast cancer, hsa-miR-21-5p was reported to be sublocated in mitochondria and able to interact with mitochondria-related differentially expressed genes in multiple mechanisms (30), including the collagen metabolism by Discoiding Domain Receptor 2 (DDR2), which, in turn, has been related to diabetic osteopenia (31). The gene discussed is DDR2; the disease is breast cancer.