['Isolated limb perfusion (ILP) with tumor necrosis factor-alpha (TNF) and melphalan for advanced extremity malignancies achieves significant complete response rates. To study molecular mechanisms underlying this response, a nude rat ILP model with a human melanoma xenograft was developed.', 'NIH1286 human melanoma was grown subcutaneously in the hind limb of nude rats. Anesthetized rats underwent a 10-minute ILP via femoral vessels with hetastarch, heparin, and melphalan, TNF, or TNF plus melphalan. The tumors and ulcers were measured and viable tumor area was calculated. Post-ILP tumors were analyzed by electron microscopy for vascular damage and also by liquid chromatography atmospheric pressure chemical ionization tandem mass spectrometry (LC/APCI/MS/MS) for free melphalan levels. Colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-dephenyltetrazolium bromide (MTT) assays were performed on NIH1286 cells and human dermal microvascular endothelial cells (HDMVEC) to test for direct cytotoxicity to TNF and melphalan. Post-ILP tumors sections were also examined by electron microscopy.', 'The mean maximal decrease in viable tumor area after ILP for control, TNF, melphalan, and TNF + melphalan groups were 0%, 22 +/- 13%, 61 +/- 14%, and 100 +/- 0%, respectively. LC/APCI/MS/MS revealed no difference in the free tumor melphalan concentration between melphalan alone and TNF + melphalan groups. The percent cytotoxicity in MTT assays using TNF, melphalan, and TNF + melphalan against NIH1286 were 0%, 51-59%, and 74-81%, respectively, and against HDMVEC were 28%, 16-23%, and 6-13%, respectively. Electron microscopic analyses showed that addition of TNF to the perfusate caused erythrostasis in tumor blood vessels.'] Does a human melanoma xenograft in a nude rat respond to isolated limb perfusion with TNF plus melphalan?