S100A4 is upregulated via the binding of c-Myb in methylation-free laryngeal cancer cells

442 Abstract. DNA hypomethylation is correlated with the over- expression of the S100A4 gene in several types of cancers including laryngeal cancer, but the molecular mechanism is unknown. We speculated that the methylation status of the promoter affects its binding to the corresponding transcription factors. In the present study, luciferase reporter assay results indicated that the sequences -485 - +73 and -486 - -530 of the S100A4 promoter may harbor the positive and negative cis-acting elements, respectively; and moreover, the luciferase activity promoted by the sequence -485 - +73 increased and the S100A4 gene was significantly upregulated in 5-Aza-induced HEp2 cells. This implies that the methylation status of the sequence is important in regulating the expression of S100A4. Four transcription factor binding motifs including c-Myb, C/EBpα, Ap2 and Msx-1 in the region were predicted by P-Match software. c-Myb and C/EBpα but not Ap2 and Msx-1 were confirmed by EMSA and ChIP as transcription factors of S100A4. The decreased luciferase activity in methylation-free HEp2 cells transfected by the mutant c-Myb motif related to the methylated cytosine suggests that the hypomethylation of the c-Myb motif upregulates the S100A4 expression in laryn- geal cancer.