This study tests the hypothesis that the activators of peroxisome proliferator-activated receptors (PPARs) and 9-cis-retinoic acid receptor (RXR) regulate human semaphorin 6B (Sema6B) gene expression. The human MCF-7 breast adenocarcinoma cell line was chosen because it expresses Sema6B at a high level. The Sema6B mRNA level was analyzed by RT-PCR and the semaphorin 6B protein content was determined using a polyclonal antibody that we have produced and characterized. Treatments with fenofibrate (a PPARα activator) and troglitazone (a PPARγ ligand) strongly decreased the Sema6B mRNA. The drop in Sema6B mRNA level and in protein content was more important when the treatment combined the action of fenofibrate or troglitazone and 9-cis-retinoic acid. On the other hand, no significant change was observed in the Sema6B mRNA and protein levels when the cells were exposed to the combined action of GW610742 (a PPARβ activator) and 9-cis-retinoic acid. These data suggest that PPARα/RXR and PPARγ/RXR heterodimers are involved in the regulation of Sema6B gene expression and open new perspectives concerning the participation of these nuclear receptors in cell recognition and migration.

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