| Popis: |
Cell death and bystander effect are crucial for both the efficacy of cancer therapy and the modulation of anti-tumour immune response. The ‘bystander effect’ refers to a process whereby untreated cells exhibit either the deleterious or beneficial indirect effects as a result of signals received from nearby targeted cells. Various molecular players and pathways have been suggested to mediate the bystander effects, nevertheless to date it is not known which are the key molecules and cellular mechanisms underpinning cell death signal propagation. Several reports suggest the involvement of both nitric oxide (NO) and reactive nitrogen species (RNS) in mediating the bystander effect. Nevertheless their role in the process has not been totally defined since these molecules can either inhibit or sustain tumour progression. Additionally, the methods conventionally applied for NO tracking do neither necessarily reflect real-time NO production nor allow studies into intact three-dimensional tumour mass. The primary aim of this study was to investigate and characterize cell signals responsible for the bystander effect within the tumour microenvironment, paying particular attention to NO. To this purpose, we exploited intravital microscopy by taking advantage of the novel fluorecent probe for NO (CuFL) and the dorsal skinfold chamber model on living tumour-bearing mice subjected to photodynamic therapy (PDT). Notably, the PDT-triggered bystander effect was associated to the generation of very fast NO and Ca2+ waves within the whole tumour mass, supported the hypothesis that constitutive NOS activity might be crucial for the beneficial spread of bystander response and death signals propagation. Additionally, we demonstrated that PDT triggered apoptosis in bystander cells, through gap junction intercellular communication. Finally, our results, provide the first direct evidence of NO involvement in bystander responses within a three-dimensional tumour mass, and strikingly corroborate the notion that connexin gap junction are instrumental for mediating bystander death signals propagation. |
