Extracellular sphingosine-1-phoshate stimulates NF-kB pathway in cells lacking filamin A

ALVAREZ SE; CAMPOS LE; RODRIGUEZ YI; CASTRO MG; SANCHEZ ES; SPIEGEL S

Simposio; SISTAM 2012; 2012

Sphinghosine-1-phosphate (S1P) is a bioactive sphingolipid metabolite that regulates several biological events of importance in inflammation and cancer. S1P is produced inside the cells by two sphingosine kinases, SphK1and SphK2, and might act as an intracellular messenger or in an autocrine/paracrine manner through binding to five G protein-coupled receptors named S1P1-5. Thus, the biological response to extracellular S1P depends on which receptors are expressed in the surface. We have previously showed that intracellular S1P is required for tumor necrosis factor (TNF)-induced NF-kB activation in melanoma cell lines that express Filamin A (FlnA). Interestingly, NF-kB has been pointed as the critical link between inflammation and cancer. Here, we show that extracellular S1P induces the activation of NF-kB only in melanoma cells lacking FlnA. To examine the pathway, we analyzed IKK and IkBa phosphorylation by western blot. We suggest that S1P1 is the receptor involved in the process, since the activation is inhibited with specific antagonists.  Moreover, by using pharmacological inhibitors and siRNA silencing, our preliminary data indicate that PKCd might be required in the pathway. To address if the absence of FlnA is the only responsible for allowing extracellular S1P to activate NF-kB, we downregulated the protein in FlnA-expressing A7 cells and we are currently evaluating both TNF and S1P induced NF-kB activation. These results support a role of S1P in inflammation mediated progression of melanoma.