Immunomodulating role of bisphosphonates on human gamma delta T cells: an intriguing and promising aspect of their antitumour activity

Vγ9Vδ2 T cells have the ability to produce inflammatory cytokines involved in protective immunity against intracellular pathogens and tumours and to display strong cytolytic as well as bactericidal activities. This suggests a direct involvement of Vγ9Vδ2 T lymphocytes in immune control of cancer and infections. These observations have recently aided development of novel immunotherapeutic approaches aimed at Vγ9Vδ2 T cell activation. Nitrogen-containing bisphosphonates (N-BPs) play a crucial role in Vγ9Vδ2 T lymphocyte activation and in the acquisition of effector functions. The preliminary results of these innovative strategies are encouraging. Moreover, compelling evidence in the literature supports the hypothesis that the antitumour effect of bisphosphonates is exerted through direct as well as indirect mechanisms. An additional and not yet well explored mechanism by which N-BPs may display antineoplastic effect is related to their immunomodulatory properties. It is fascinating that N-BPs influence the immune system in various but interrelated ways, being able to enhance the innate and to promote the adaptive immune responses. For all these reasons, Vγ9Vδ2 T lymphocytes represent a particularly interesting target for immunotherapeutic protocols based on N-BP administration. All these unexpected effects of N-BPs on the immune system have opened new and intriguing possibilities of therapeutic use for these drugs.