Anti-proliferative effect of peroxisome proliferator-activated receptor γ agonists on human malignant melanoma cells in vitro

Malignant melanoma has a poor reputation for early spread and no curative treatment is yet available. As peroxisome proliferator-activated receptor gamma (PPAR gamma) agonists (glitazones) have recently been shown to have growth-inhibiting effects on different cancer lineages, the aim of this study was to analyze the effects of four glitazones (rosiglitazone, ciglitazone, pioglitazone and troglitazone) on the growth of six human malignant melanoma cells in vitro. Proliferation of six human melanoma cell lines under glitazone treatment over a broad concentration range (0.15-300 mu mol/l) was assessed by means of the XTT cell proliferation assay, and expression of PPAR gamma in these cell lines was analyzed using both immunohistochemical and molecular biological techniques. All four glitazones showed a significant dose-dependent anti-proliferative effect on all six cell lines starting at a concentration of 0.3 mu mol/l, with ciglitazone being the most potent inhibitor of cell growth, followed by troglitazone, rosiglitazone and pioglitazone. PPAR gamma was predominantly localized in the cytoplasm; however, there were quantitative differences in PPAR gamma expression between the different cell lines as demonstrated by quantification of Western blots. As an already approved class of drugs, glitazones have been found to significantly inhibit growth of human malignant melanoma cells in vitro and might be a promising tool for further therapeutic studies.