This proteindelivery system is currently limited to membrane-bound proteins, butgiven the centrality of the surface receptors in cancer, includingthe tyrosine kinase receptor family42 andthe G protein-coupled receptor family,43 there is a clear potential for widespread use of this system inrapidly engineering receptor-driven cancers, which represent targetsfor over half of all cancer drugs approved in the last decade. The gene discussed is NTRK1; the disease is cancer.