The impact of surgery and mild hyperthermia on tumor response and angioneogenesis of malignant melanoma in a rat perfusion model

Expression of chemoresistance-related genes and heat shock protein 72 in hyperthermic isolated limb perfusion of malignant melanoma: an experimental study

Hyperthermic isolated limb perfusion (HILP) is considered an established treatment for multiple locoregional intransit metastases in malignant melanoma of the extremities. Various mechanisms such as the expression of chemoresistance genes and heat shock proteins by the tumor may be responsible for varying response rates and locoregional recurrences of the treatment. The aim of the experimental animal study was to investigate the direct impact of HILP on such mechanisms of resistance. Tissue temperature, administration of the cytostatic drug, and duration of perfusion were varied. Expression of the chemoresistance genes mdr1, mrp1, mrp2, and lrp and of heat shock protein 72 (HSP72) in the tumor tissue was analysed using RT-PCR and western blot analysis. The untreated SK-MEL-3 tumor expressed mdr1, mrp1, and lrp, but not mrp2. Neither variation of temperature, administration of the cytostatic drug, nor duration of perfusion changed the expression of this “resistance pattern”. In contrast to the cytostatic drug, hyperthermia causes a persistent induction of HSP72. Both observations could offer a potential explanation for failure of HILP in malignant melanoma.

Suppression of beta-catenin by antisense oligomers augments tumor response to isolated limb perfusion in a rodent model of adenomatous polyposis coli-mutant colon cancer

BACKGROUND

Isolated hepatic perfusion has been used in patients with colorectal cancer (CRC) metastatic to the liver. We sought to determine whether perfusion with antisense oligodeoxynucleotides results in the downregulation of beta-catenin and whether this improves tumor response to isolated limb perfusion (ILP) in a heterotopic model of human CRC.

METHODS

Adenomatous polyposis coli-mutant human CRC xenografts were implanted into athymic rats. Animals were randomized to the following groups: (1) no treatment, (2) control ILP, (3) melphalan ILP, (4) ILP with antisense specific for beta-catenin, (5) ILP with nonspecific antisense, and (6) melphalan plus beta-catenin-specific antisense ILP. Tumor response and Western blot analysis of protein expression were evaluated.

RESULTS

The maximal decrease (mean +/- SE) in tumor volume was 0% +/- 10% for no treatment, 19% +/- 14% for control ILP, 58% +/- 3% for melphalan ILP, 58% +/- 9% for beta-catenin-specific ILP, 13% +/- 19% for nonspecific antisense ILP, and 73% +/- 6% for melphalan plus beta-catenin-specific ILP (P < .05 for melphalan ILP, beta-catenin-specific ILP, and melphalan plus antisense ILP). Tumor regrowth was delayed for 6 days after control ILP, 24 days after melphalan ILP, 20 days after beta-catenin-specific ILP, 10 days after nonspecific antisense ILP, and 60 days after melphalan plus beta-catenin-specific ILP (P < .05 for melphalan plus beta-catenin-specific ILP compared with all others). Western blotting revealed prolonged suppression of beta-catenin expression after beta-catenin-specific ILP.

CONCLUSIONS

Short-term beta-catenin antisense treatment improves tumor response rates after ILP in a rodent model of human CRC.