A novel type of artificial drug delivery system that blocks cancer cells' ability to expel chemotherapy and thereby acquire drug resistance is published online this week in Nature Biotechnology. In mice, this approach successfully inhibits the growth of drug-resistant colon, breast and uterine tumours and substantially extends life expectancy.

Himanshu Brahmbhatt and colleagues' technique relies on minicells ― empty, lifeless bacteria without genetic material ― which can be filled with different types of drug. Mice were sequentially given two sets of minicells ― the first filled with small RNA molecules to block production of the pumps that confer drug-resistance, and the second one loaded with toxic chemotherapy drugs to kill the tumour cells with disabled pumps.

Since the drugs are not released into general circulation, they can kill cancer cells at much lower dosage than normally required, thus avoiding undesirable side effects.