Local
interleukin 2 (IL-2)
therapy is more effective against systemic tumours than systemic
IL-2 therapy, but it remains unclear whether
IL-2 should be injected intratumourally or peritumourally. To investigate this question, we treated DBA/2 mice bearing a large subcutaneous syngeneic SL2
lymphoma with either intra or peritumoural
IL-2 therapy. Both applications enhanced survival, but intratumourally injected
IL-2 was more effective than peritumourally injected
IL-2. Tumours started to regress 4 days after
IL-2 injection. Tumour cells died at the
IL-2 injection site, although
IL-2 is not directly cytotoxic for SL2 cells in vitro. Tumour cell death correlated well with oedema and extravascular erythrocytes, but less with leukocyte infiltrates. In mice bearing two s.c. tumours, intratumoural application
therapy of
IL-2 in one tumour caused decrease in size of both tumours in 4-9 days after
therapy. However, the
IL-2 treated tumours regressed more strongly than the untreated tumours. We conclude that vascular leakage and/or tissue destruction inside the tumour may contribute to the enhanced effect of intratumoural
IL-2 therapy compared to peritumoural
IL-2 therapy. Hence, we recommend applying of intratumoural rather than peritumoural
IL-2 therapy.