Drug resistance in cancer: a perspective.

Drug resistance remains the thorniest obstacle in developing improved systemic therapies for disseminated cancer. The combination of genetic instability together with the great molecular heterogeneity that are displayed by malignant cells makes constructing effective, rational treatment programs difficult in the extreme. However, new insights into the action of antitumor agents at the molecular level plus greater understanding of the relationship of drug resistant states to the fundamental abnormalities that generate malignancy point the way to producing therapies that are more specific and therapeutically effective. However, a non-trival problem is the drug development system itself which is currently poorly set up to yield patient specific drug programs in a timely fashion.