Hypoxia/reoxygenation induction of monocyte chemoattractant protein-1 in melanoma cells: involvement of nuclear factor-kappaB, stimulatory protein-1 transcription factors and mitogen-activated protein kinase pathways.

Monocyte chemoattractant protein-1 (MCP-1) expression is found in malignant melanoma and melanoma metastases. Since areas of hypoxia/reoxygenation (H/R) are a common feature of malignant tumours and metastases, we addressed the question whether melanoma cells produce MCP-1 upon exposure to H/R. In the present study, we show that melanoma cells up-regulate MCP-1 mRNA and protein under H/R. By means of reporter gene analysis, we further demonstrate that H/R induces transcriptional activation of the MCP-1 promoter carrying a stimulatory protein-1 (SP1) and two nuclear factor-kappaB (NF-kappaB) binding motifs. Accordingly, H/R-stimulated melanoma cells showed enhanced binding activity of both transcription factors NF-kappaB and SP1 in electrophoretic mobility-shift assay. A common upstream activator of NF-kappaB, inhibitory kappaBalpha kinase, was not significantly activated under H/R conditions. Further analysis of upstream signalling events revealed that members of the mitogen-activated protein kinases family, namely extracellular signal-regulated protein kinase, c-Jun N-terminal kinase/ stress-activated protein kinase and p38 stress kinase, may be involved in MCP-1 transcriptional regulation under H/R. In summary, we conclude that H/R induces MCP-1 production in melanoma cells via the co-operative action of both transcription factors NF-kappaB and SP1, and involves mitogen-activated protein kinase signalling pathways. Functionally, H/R-induced MCP-1 production may contribute to tumour progression by committing selective pressure on tumour cells via chemoattraction and activation of tumour-infiltrating monocytes/macrophages.