Abstract: The present invention relates to compositions and methods for reducing cell proliferation and/or promoting cell death by inhibiting Drp1. It is based, at least in part, on the discoveries that (i) Drp1 disruption-induced mitochondrial hyperfusion is functionally linked to the cell cycle regulation apparatus, so that Drp1 inhibition results in a disruption of the cell cycle and DNA aberrancies; (ii) inhibition of both Drp1 and ATR are synthetic lethal causing increased DNA damage and apoptotic cell death; and (iii) even in resistant cell lines, Drp1 inhibitor (e.g., mdivi-1) together with a second antiproliferative agent (e.g., cisplatin or carboplatin) act synergistically to promote apoptosis. Accordingly, the present invention provides for novel anticancer strategies.