23411

SIRT1

sirtuin 1;SIRT1;sirtuin 1

NAD-dependent deacetylase sirtuin-1|NAD-dependent protein deacetylase sirtuin-1|SIR2-like protein 1|SIR2alpha|regulatory protein SIR2 homolog 1|sir2-like 1|sirtuin type 1

10q21.3

protein-coding

BACKGROUND: Our previous studies showed that SIRT1 was over-expressed in gastric cancer specimens and related with lymph node metastasis. However, the mechanism of SIRT1 up-regulation and its association with metastasis in gastric cancer remain unclear. The present study was undertaken to understand the role of microRNA in regulation of SIRT1 in the progression of gastric cancer. METHODS: expression of miR-204 and SIRT1 was assessed in two gastric cancer cell lines and 24 matched cancer specimens. Luciferase reporter assay was carried to verify that miR-204 targeting SIRT1. Cell invasion ability of AGS and BGC was detected by transwell invasion assay. Annexin V/PI assay was used to investigate the cell sensitivity of anoikis. Western blot analysis to assess SIRT1, Vimentin, E-Cadherin, LKB1, and beta-actin expression was performed in gastic cancer cell lines. RESULTS: SIRT1 was defined as the target gene and elucidated the biological functions of miR-204 with a luciferase reporter assay and Western blot analysis. We verified that miR-204 levels were down-regulated and significantly associated with the up-regulation of SIRT1 mRNA levels in gastric cancer specimens. Over-expression of miR-204 reduced cell invasion and anoikis resistance in gastric cancer cells. Up-regulation of miR-204 influenced the levels of the epithelial mesenchymal transition (EMT)-associated genes, increasing E-cadherin levels and decreasing Vimentin levels. We demonstrated that the regulation of EMT by miR-204 involves cooperation with LKB1. Furthermore, silencing of SIRT1 phenocopied the effects of miR-204 in gastric cancer cells. These data demonstrate that miR-204 plays an important role in regulating metastasis of gastric cancer, which is involved in post-transcriptional repression of SIRT1. CONCLUSION: Our results suggest that down-regulation of miR-204 promotes gastric cancer cell invasion by activating the SIRT1-LKB1 pathway. These data demonstrate that miR-204 plays an important role in regulating metastasis of gastric cancer, which is involved in post-transcriptional repression of SIRT1.

Brain metastases are a frequent and ongoing major complication of non-small cell lung cancer (NSCLC). To deepen our understanding to the underlying mechanisms by which NSCLC cells metastasize to brain and hence to improve the therapy, a high throughput RNAi screening with shRNA library of 153 epigenetic genes was subjected to A549, a NSCLC cell line with high migration ability, to examine the effects of these genes on cell migration by wound-healing assay. The screening results showed that knockdown of 2 genes (KDM5B and SIRT1) dramatically and specifically inhibits A549 migration but not affects the proliferation, which was subsequently confirmed through transwell migration assay. Furthermore, SIRT1 is found to be highly expressed in brain metastasis tissues of NSCLC, compared to the NSCLC tissues, suggesting that SIRT1 may play roles in brain metastasis of NSCLC. The relationship between SIRT1 expression and cell migration ability was further investigated in three NSCLC cell lines and the result indicated that SIRT1 expression is tightly correlated with cell migration ability. Collectively, our work provides potential biomarker and therapeutic target for brain metastasis of NSCLC.

The epithelial-to-mesenchymal transition (EMT) is a crucial program for the invasion and metastasis of epithelial tumors that involves loss of cell-cell adhesion and increased cell mobility; however, mechanisms underlying this transition are not fully elucidated. Here, we propose a novel mechanism through which the nicotinamide adenine dinucleotide-dependent histone deacetylase SIRT1 regulates EMT in prostate cancer cells through cooperation with the EMT inducing transcription factor ZEB1. We found that forced expression of SIRT1 in non-transformed PZ-HPV-7 prostate epithelial cells disrupts the epithelial morphology concomitant with decreased expression of the epithelial marker, E-cadherin, and increased expression of mesenchymal markers. In contrast, silencing SIRT1 in metastatic prostate tumor cells restores cell-cell adhesion and induces a shift toward an epithelial morphology concomitant with increased expression of E-cadherin and decreased expression of mesenchymal markers. We also found that SIRT1 has a physiologically relevant role in endogenous EMT induced by EGF signaling in prostate cancer cells. We propose that the regulation of EMT by SIRT1 involves modulation of, and cooperation with, the EMT inducing transcription factor ZEB1. Specifically, we show that SIRT1 silencing reduces expression of ZEB1 and that SIRT1 is recruited to the E-cadherin proximal promoter by ZEB1 to deacetylate histone H3 and to reduce binding of RNA polymerase II, ultimately suppressing E-cadherin transcription. We thus identify a necessary role for ZEB1 in SIRT1-mediated EMT. Finally, we show that reduction of SIRT1 decreases prostate cancer cell migration in vitro and metastasis in vivo in immunodeficient mice, which is largely independent of any general effects of SIRT1 on prostate cancer growth and survival. We therefore identify SIRT1 as a positive regulator of EMT and metastatic growth of prostate cancer cells and our findings implicate overexpressed SIRT1 as a potential therapeutic target to reverse EMT and to prevent prostate cancer progression.