Bystander Effects in Photodynamic Therapy of Cancer

The aim of this study is to cast new light on the role of NO and Ca2+ in bystander effect propagation during PDT. This work is based on the novel fluorescent probe CuFi and provides the first direct evidence of NO involvement in bystander response during PDT. Moreover, the shape of NO signals suggests a dual mechanism that involves direct release from the target cell as well as enzymatic production. By analyzing our data in the light of simple NO diffusion model, we were able to estimate the contribution of the diffusive component relative to enzymatc production, which amounts to at least 50% of the total NO signals.