Targeting diagnostic agents or drugs to tumours could make cancer diagnosis and treatment more effective. Researchers have devised ways to get molecules to home in on tumours, but getting them deep into the bulk of the tumour has proved difficult.
Erkki Ruoslahti of the Burnham Institute for Medical Research in Santa Barbara, California, and his co-workers have identified a peptide that they bound to a known cancer drug, as well as to imaging agents, and then injected these into tumour-bearing mice. Magnetic resonance imaging and other methods revealed an 8–11-fold higher level of the peptide-bound drug in tumours than of the drug alone.
The researchers show that the peptide targets and penetrates tumours by first binding to a set of tumour-specific receptors, called αv integrins. It is then cleaved, exposing a motif that binds to another receptor, neuropilin-1, to gain entry to the cell.