Activation of the mitochondrial GTPase dynamin-related protein-1 (DRP-1) reflects regulatory kinases (cyclin B1/CDK1) that respond to signals from growth factors. In pulmonary hypertensive patients, cyclin B1 levels are elevated leading to activation of DRP-1. If fission (which is required for mitochondrial division) is inhibited, by blocking the activation of DRP-1, the cell cycle is halted, causing cells to be blocked in G2/M arrest. The intersection of the mitochondrial and cell cycles is cyclin B1/CDK1-mediated mitotic fission, and this exposes an “Achilles heel” for rapidly proliferating cells that can be therapeutically targeted. Reproduced with permission from [62].