We first determined the effect of selective BCL2 proteins inhibition on mitochondrial activity in our previously characterised MCF7 breast cancer cells overexpressing either BCL2 (MCF7-BCL2) or BCL(X)L (MCF7-BCL(X)L), or transfected with the corresponding empty vector (MCF7-pSFFV) [23–25]. Here, BCL2 is linked to breast cancer.