P-Rex1 may be important for several other cancer-promoting pathways. For example, estrogen-receptor signaling also appears to rely on P-Rex1, which means that targeted inhibitors of P-Rex1 might improve responses to anti-estrogen therapies such as tamoxifen.

The authors also found that P-Rex1 is also used by another receptor, CXCR4, which has recently shown up in many cancer studies. Despite being used in numerous pathways during cancerous growth, P-Rex1 is not expressed in many normal tissues. "That gives us a very good target. It is really cancer specific," Kazanietz says. "What's more, as P-Rex1 is expressed in some subtypes of breast tumors, it may be an excellent prototype for future personalized medicine."

Preclinical data from other groups supports the importance of the Rac pathway in cancer, according to Kazanietz. And small molecule inhibitors that block proteins in the Rac pathway appear to have strong anti-cancer effects in model systems, though their use in patients still needs to be tested.

Source: University of Pennsylvania School of Medicine