Targeting a single protein can help fight both breast cancers and leukemias, according to two reports published online in the Journal of Experimental Medicine.

The single protein is HSP90, which acts as a chaperone to protect other proteins in the cell.

A team led by Ute Moll at the University of Göttingen in Germany found that blocking HSP90 activity rendered normally protected proteins vulnerable to attack and destruction. One of these proteins - called migration inhibitory factor - drives the growth of breast tumors. HSP90 inhibitors slowed the growth of MIF-expressing breast tumors in mice but had little effect on tumors lacking MIF.

HSP90 inhibitors also look promising for certain forms of leukemia, according to a study by David Weinstock and coworkers at the Dana-Farber Cancer Institute. They showed that HSP90 inhibitors slowed the growth of leukemias driven by hyperactive versions of the enzyme JAK2, many of which become resistant to JAK2-blocking drugs. The HSP90 inhibitors delayed the growth of resistant leukemia cells in mice.

Together these studies suggest that HSP90 may represent a therapeutic target in many cancers.