Tumor size in mice is reduced by Viagra treatments (right).
In cancer patients, though the body generates tumor-specific antibodies, their efficacy is neutralized by the tumor itself. Tumors recruit cells such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells, which suppress the body's immune system, thus allowing the tumors to escape immune recognition. Borrello's team has been investigating ways to overcome this immunosuppression.
Suppression of T cells by MDSCs requires, among other things, nitric oxide production. The team reasoned, therefore, that reducing nitric oxide levels might boost immunity in cancer patients. They thus turned to Viagra. Besides its well-known vasodilatory effect, Viagra also reduces nitric oxide production through a separate but linked pathway.
The team gave Viagra to mice with colon carcinoma and found that...
