Regulation of KiSS-1 metastasis suppressor gene expression in breast cancer cells by direct interaction of transcription factors activator protein-2α and specificity protein-1

KiSS- 1 has been shown to function as a tumor metastasis suppressor gene and reduce the number of metastases in different cancers. The expression of KiSS- 1 or KiSS1, like other tumor suppressor, is commonly reduced or completely ablated in a variety of cancers via an unknown mechanism. Here we show that the loss of KiSS- 1 expression in highly metastatic breast cancer cell lines correlates directly with the expression levels of two transcription factors, activator protein- 2 alpha( AP- 2 alpha) and specificity protein 1 ( Sp1), which synergistically activate the transcriptional regulation of KiSS- 1 in breast cancer cells. Although the KiSS- 1 promoter contains multiple AP- 2 alpha binding elements, AP- 2 alpha- mediated regulation occurs indirectly through Sp1 sites, as determined by deletion and mutation analysis. Overexpression of AP- 2 alpha into highly metastatic breast cell lines did not alter KiSS- 1 promoter- driven luciferase gene activity. However, co- transfection of AP- 2 alpha wild- type or the dominant negative form of AP- 2 lacking its C- terminal DNA-binding domain, AP- 2B, together with Sp1, increased KiSS- 1 promoter activity dramatically, suggesting that AP- 2 alpha regulation of KiSS- 1 transcription does not require direct binding to the KiSS- 1 promoter. Furthermore, we demonstrated that AP- 2 alpha directly interacted with Sp1 to form transcription complexes at two tandem Sp1- binding sites of the promoter to activate KiSS- 1 transcription. Together, our results indicate that AP- 2 alpha and Sp1 are strong transcriptional regulators of KiSS- 1 and that loss or decreased expression of AP- 2 alpha in breast cancer may account for the loss of tumor metastasis suppressor KiSS- 1 expression and thus increased cancer metastasis.