In humans, COX is composed of 14 protein subunits, of which 3 are mitochondrially encoded and considered the main subunits (COX1, COX2 and COX3), and the other 11 structural subunits are encoded by nDNA (protein structures COX4, COX5A, COX5B, COX6A, COX6B, COX6C, COX7A, COX7B, COX7C, COX8 and NDUFA4 or COXFA4), reinforcing the fact that constant interaction occurs between mitochondria and nucleus, which can emphasize that genetic destabilization of COX and consequent change in its structure can lead to the progression of BC [21]. This evidence concerns the gene COX6A2 and breast cancer.