Date of Graduation
Doctor of Philosophy (PhD)
Studies from our laboratory have recently demonstrated that Gal-3 regulates autotaxin through NFAT1 and support melanoma progression. These findings prompted us to further study the role of NFAT1 in melanoma progression and metastasis. NFAT1 is a transcription factor that was first identified in immune cells, acting as a positive regulator of interleukin-2 by binding to its promoter during T cell activation. NFAT1 has an important role in the innate and adaptive immune response. In this dissertation I studied the mechanisms by which NFAT1 contributes to the acquisition of the melanoma metastatic phenotype.
To identify the role of NFAT1 in melanoma progression we stably silenced NFAT1 expression in the highly metastatic cell line, A375SM, and subjected the cells to gene expression microarray analysis. We identified and validated two downstream targets of NFAT1, i.e; IL-8 and MMP-3 to be downregulated following silencing NFAT1. While silencing of NFAT1 reduced IL-8 and MMP-3 in highly metastatic cell lines, A375SM and WM902B, overexpression of NFAT1 in the low metastatic cell line, SB2 induced the expression of both IL-8 and MMP-3. We further demonstrated that silencing NFAT1 significantly reduced the promoter activity of IL-8 and MMP-3 and mutations of the NFAT1 binding sites at either promoter reduced the promoter activity. Rescue of NFAT1 increased both IL-8 and MMP-3 expression back to their initial levels, indicating that they are directed targets of NFAT1. Importantly, we demonstrated in melanoma patient specimens and cell lines that overexpression of NFAT1 is correlated with disease progression and staging. Moreover, our in vivo studies demonstrated that NFAT1 is a major contributor of tumor growth and lung metastasis. The role of MMP-3 in melanoma progression has not been previously described. Therefore, we next decided to elucidate the role of MMP-3 in melanoma. Our in vivo studies demonstrated that MMP-3 contributes to melanoma tumor growth and metastasis.
Collectively, our data assign a previously undescribed role for NFAT1in melanoma progression through the regulation of IL-8 and MMP-3.