Combination of radiotherapy with the immunocytokine L19-IL2: Additive effect in a NK cell dependent tumour model.

Background and purpose Recently, we have shown that radiotherapy (RT) combined with the immunocytokine L19-IL2 can induce long-lasting antitumour effects, dependent on ED-B expression and infiltration of cytotoxic T cells. On the other hand, in certain tumours, IL2 treatment can trigger a natural killer cell (NK) immune response. The aim of this study is to investigate the therapeutic effect of our combination therapy in the ED-B positive F9 teratocarcinoma model, lacking MHCI expression and known to be dependent on NK immune responses. Material and methods In syngeneic F9 tumour bearing 129/FvHsd mice tumour growth delay was evaluated after local tumour irradiation (10 Gy) combined with systemic administration of L19-IL2. Immunological responses were investigated using flow cytometry. Results Tumour growth delay of L19-IL2 can be further improved by a single dose of RT administered before immunotherapy, but not during immunotherapy. Furthermore, treatment of L19-IL2 favours a NK response and lacks cytotoxic T cell tumour infiltrating immune cells, which may be explained by the absence of MHCI expression. Conclusion An additive effect can be detected when the NK dependent F9 tumour model is treated with radiotherapy and L19-IL2 and therefore this combination could be useful in the absence of tumoural MHCI expression. [ABSTRACT FROM AUTHOR]