Immunosuppressants in cancer prevention and therapy

Rapalogs such as rapamycin (sirolimus), everolimus, temserolimus, and deforolimus are indicated for the treatment of some malignancies. Rapamycin is the most effective cancer-preventive agent currently known, at least in mice, dramatically delaying carcinogenesis in both normal and cancer-prone murine strains. In addition, rapamycin and everolimus decrease the risk of cancer in patients receiving these drugs in the context of immunosuppressive regimens. In general, the main concern about the use of immunosuppressants in humans is an increased risk of cancer. Given that rapalogs are useful in cancer prevention and therapy, should they be viewed as immunosuppressants or immunostimulators? Or should we reconsider the role of immunity in cancer altogether? In addition to its anti-viral, anti-inflammatory, anti-angiogenic and anti-proliferative effects, rapamycin operates as a gerosuppressant, meaning that it inhibits the cellular conversion to a senescent state (the so-called geroconversion), a fundamental process involved in aging and age-related pathologies including cancer.