Rapamycin (RAPA) is a bacterial macrolide with antifungal and immunosupressant activities, which is used to prevent allograft rejection in organ transplant patients. In February Nature Medicine, Markus Guba and colleagues from University of Regensburg, Germany, show that in addition to providing effective immunosuppression, RAPA may also reduce the risk of cancer development.

Guba et al. used a murine model of adenocarcinoma and observed that mice treated with immunosuppressive doses of RAPA had a reduced incidence of tumor in the liver, whereas those treated with another common immunosupressant (cyclosporine) showed the opposite — an increased amount of liver metastasis. They suggested that this could be explained by the potent antiangiogenetic effect of RAPA, which is linked to reduced production of vascular endothelial growth factor (VEGF) and to blockage of VEGF-induced endothelial cell signaling (Nat Med 2002, 8:128-135).

"These findings are of considerable interest because treatment with...