Levamisole plus 5-fluorouracil inhibits the growth of human colorectal xenografts in nude mice

Fragments of human colorectal adenocarcinomas were inserted under the renal capsule of nude mice. The growth of these tumour grafts was significantly inhibited by the combination of 5-fluorouracil (5-FU) and levamisole. An alternating regimen of levamisole 2.5 mg/kg and 5-FU 20 mg/kg decreased the size of tumour implants by 33–59% and/or increased the number of macroscopically disappeared fragments in the combined group compared with ineffective monotherapy with saline, levamisole or 5-FU. This model could be valuable for investigating the mechanism of action of levamisole and to evaluate the effects of this adjuvant therapy in other oncological settings.