PARP and Cancer — If It's Broke, Don't Fix It

With apologies to Nietzsche, who once said “that which does not kill us makes us stronger,” sometimes that which does not kill weakens us so the next blow will be lethal. In this issue of the Journal, O'Shaughnessy and colleagues1 describe a study in which poly(adenosine diphosphate–ribose) polymerase (PARP) inhibition was added to cytotoxic chemotherapy in an effort to set breast cancers up for that “next blow” (ClinicalTrials.gov number, NCT00540358). PARP inhibitors represent an exciting new therapeutic direction in oncology: the rational targeting of tumor-cell vulnerability during DNA repair.Cellular DNA is under constant assault; over 150 genes, in multiple . . .