Nuclear Factor of Activated T Cells-dependent Down-regulation of the Transcription Factor Glioma-associated Protein 1 (GLI1) Underlies the Growth Inhibitory Properties of Arachidonic Acid

Abstract

Numerous reports have demonstrated a tumor inhibitory effect of polyunsaturated fatty acids (PUFAs). However, the molecular mechanisms modulating this phenomenon are in part poorly understood. Here, we provide evidence of a novel antitumoral mechanism of the PUFA arachidonic acid (AA). In vivo and in vitro experiments showed that AA treatment decreased tumor growth and metastasis and increased apoptosis. Molecular analysis of this effect showed significantly reduced expression of a subset of antiapoptotic proteins, including BCL2, BFL1/A1, and 4-1BB, in AA-treated cells. We demonstrated that down-regulation of the transcription factor gliomaassociated protein 1 (GLI1) in AA-treated cells is the underlying mechanism controlling BCL2, BFL1/A1, and 4-1BB expression. Using luciferase reporters, chromatin immunoprecipitation, and expression studies, we found that GLI1 binds to the promoter of these antiapoptotic molecules and regulates their expression and promoter activity. We provide evidence that AA-induced apoptosis and down-regulation of antiapoptotic genes can be inhibited by overexpressing GLI1 in AA-sensitive cells. Conversely, inhibition of GLI1 mimics AA treatments, leading to decreased tumor growth, cell viability, and expression of antiapoptotic molecules. Further characterization showed that AA represses GLI1 expression by stimulating nuclear translocation of NFATc1, which then binds the GLI1 promoter and represses its transcription. AA was shown to increase reactive oxygen species. Treatment with antioxidants impaired the AAinduced apoptosis and down-regulation of GLI1 and NFATc1 activation, indicating that NFATc1 activation and GLI1 repression require the generation of reactive oxygen species. Collectively, these results define a novel mechanism underlying AA antitumoral functions that may serve as a foundation for future PUFA-based therapeutic approaches.

Arachidonic acid and lipoxin A4 attenuate alloxan‐induced cytotoxicity to RIN5F cells in vitro and type 1 diabetes mellitus in vivo

“…In addition, AA also regulates glioma‐associated protein 1 (GLI1) transcription factor. It was reported that AA modulates the expression and promoter activity of antiapoptotic genes (BCL2, BFL1/A1, and 4‐1BB), alter nuclear translocation of NFATc1 and consequently influence generation of reactive oxygen species . It remains to be seen whether AA and LXA4 are able to modulate GLI1 transcription factor in RINF cells in vitro and pancreatic β cells in vivo (type 1 DM) to produce their beneficial actions reported here.…”

NFATc1 is a tumor suppressor in hepatocellular carcinoma and induces tumor cell apoptosis by activating the FasL‐mediated extrinsic signaling pathway

“…However, other studies suggested NFATc1 might function as a tumor suppressor in some types of cancer. [33][34][35][36][37][38] Lucena et al 39 found that different murine Nfatc1 isoforms played distinct roles in NIH 3T3 cells. While Nfatc1 isoform 3 induced cell transformation, Nfatc1 isoform 1 reduced cell proliferation and induce apoptosis.…”

Cell cycle and apoptosis regulation by NFAT transcription factors: new roles for an old player

“…119 , 120 Of note, besides all those studies reporting NFAT2 as an oncogene, it was shown that one of the antitumor effects of arachidonic acid treatment in mammary and pancreatic cancer cell lines was through the induction of NFAT2, which downregulates GLI-1 transcription, resulting in decreased expression of anti-apoptotic genes such as Bcl-2 and 4-1BB . 121 However, it remains to be clarified whether a specific NFAT2 isoform is induced in this context or whether the arachidonic acid modifies the expression of putative NFAT2 partners.…”