Successful treatment of solid tumors with chemotherapeutics requires that adequate levels reach the tumor cells. Tumor vascular normalization has been proposed to enhance drug delivery and improve tumor response to chemotherapy.
Addition of high-dose tumor necrosis factor-alpha to melphalan-based isolated limb perfusion enhances anti-tumor effects impressively. Unfortunately, the mechanism of action of tumor necrosis factor-alpha is still not fully understood. Here, we investigated the effects of tumor necrosis factor-alpha on the tumor microenvironment and on secondary immunological events during and shortly after isolated limb perfusion in soft-tissue sarcoma-bearing rats. Already during isolated limb perfusion, softening of the tumor was observed. Co-administration of tumor necrosis factor-alpha in the isolated limb perfusion with melphalan induced a six-fold enhanced drug accumulation of melphalan in the tumor compared with isolated limb perfusion with melphalan alone. In addition, directly after perfusion with tumor necrosis factor-alpha plus melphalan, over a time-frame of 30 min, vascular destruction, erythrocyte extravasation and hemorrhage was detected. Interstitial fluid pressure and pH in the tumor, however, were not altered by tumor necrosis factor-alpha and no clear immune effects, cellular infiltration or cytokine expression were observed. Taken together, these results indicate that tumor necrosis factor-alpha induces rapid damage to the tumor vascular endothelial lining resulting in augmented drug accumulation. As other important parameters were not changed (e.g. interstitial fluid pressure and pH), we speculate that the tumor vascular changes, and concurrent hemorrhage and drug accumulation are the key explanations for the observed synergistic anti-tumor response.
The cytokine interleukin 2 (IL-2) is a mediator of immune cell activation with some antitumor activity, mainly in renal cell cancer and melanoma. We have previously shown that tumor necrosis factor (TNF)-A has strong synergistic antitumor activity in combination with chemotherapeutics in the isolated limb perfusion (ILP) setting based on a TNF-mediated enhanced tumor-selective uptake of the chemotherapeutic drug followed by a selective destruction of the tumor vasculature. IL-2 can cause vascular leakage and edema and for this reason we examined the antitumor activity of a combined treatment with IL-2 and melphalan in our wellestablished ILP in soft tissue sarcoma-bearing rats (BN175). ILP with either IL-2 or melphalan alone has no antitumor effect, but the combination of IL-2 and melphalan resulted in a strong synergistic tumor response, without any local or systemic toxicity. IL-2 enhanced significantly melphalan uptake in tumor tissue. No signs of significant vascular damage were detected to account for this observation, although the tumor sections of the IL-2-and IL-2 plus melphalan-treated animals revealed scattered extravasation of erythrocytes compared with the untreated animals. Clear differences were seen in the localization of ED-1 cells, with an even distribution in the sham, IL-2 and melphalan treatments, whereas in the IL-2 plus melphalan-treated tumors clustered ED-1 cells were found. Additionally, increased levels of TNF mRNA were found in tumors treated with IL-2 and IL-2 plus melphalan. These observations indicate a potentially important role for macrophages in the IL-2-based perfusion. The results in our study indicate that the novel combination of IL-2 and melphalan in ILP has synergistic antitumor activity and may be an alternative for ILP with TNF and melphalan. (Cancer Res 2005; 65(10): 4300-8)
Histamine (Hi) combined to melphalan in a rat experimental model of isolated limb perfusion (ILP) for lower limb soft tissue sarcoma, resulted in overall response rates (OR) of 66%. Likewise, ILP with interleukin-2 (IL-2) resulted in OR of 67%, when combined to melphalan, in the same experimental model. In systemic immunotherapy, the combination of IL-2 and Hi has been used for solid tumor treatment based on immunomodulatory effects. In this study, we used our well-established ILP experimental model to evaluate whether the synergistic effect between the two drugs seen in the systemic setting, could further improve response rates in a loco-regional setting. Histological evaluation was done directly and 24 h after ILP. Melphalan uptake by tumor and muscle were measured. Hi and IL-2 together, combined to melphalan in the ILP led to OR of only 28%. Histology of tumors demonstrated partial loss of Hi-induced hemorrhagic effect when IL-2 was present. Melphalan accumulation in the tumor when both Hi and IL-2 were added (3.1-fold) was very similar to accumulation with Hi only (2.8-fold), or IL-2 only (3.5-fold) combined to melphalan. In vitro there was no synergy between the drugs. In conclusion there was a negative synergistic effect between IL-2 and Hi in the regional setting.
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