Drug resistance stops cancer treatments in their tracks between 20% and 50% of the time. In hopes of defeating resistance, researchers have begun employing RNA interference. As various mutations accumulate during cancer's uncontrolled growth, many cells become resistant through overexpression of one protein, Pglycoprotein, which ferries drugs out of cells. Other cancer-drug targets become mutated or overexpressed to win out over therapeutics. Recent reports of RNAi used to stop or stall such overproduction and reverse malignant cell's multidrug resistance have added to the heap of applications for the technology.