Protein SNAI1 Research Articles

Abstract 62: Vitamin D3 induces 15-Hydroxyprostaglandin Dehydrogenase to suppress pancreatic cancer cell proliferation

Abstract BACKGROUND: Excess prostaglandin E2 (PGE2) mediates growth and survival of several cancers, including prostate and pancreatic cancers (PaCa). 15-Hydroxyprostaglandin dehydrogenase (PGDH) catalyzes PGE2 to an inactive 15-keto metabolite. We have previously shown that PGDH is down-regulated in human PaCa, contributing to accumulated levels of PGE2 that can subsequently feed back to suppress further PGDH expression. In contrast, PGDH expression has been reportedly up-regulated by vitamin D3 (VD3) in prostate cancer cells but has not been confirmed in pancreatic cancer cells. AIM: The study focuses on whether VD3 up-regulates PGDH expression in pancreatic cancer cells. METHODS: Human PaCa cell lines BxPC-3, HPAF-II and MIA PaCa-2 were treated with VD3 were analyzed for vitamin D receptor (VDR), cyclooxygenase-2 (COX-2) and PGDH expression by RT-PCR. Protein extracts were analyzed by Western blotting for VDR, COX-2, PGDH, SNAI1, SNAI2 and GAPDH expression. Cellular proliferation was analyzed by MTT assay. PGE2 was measured by ELISA. RESULTS: Dose-dependent treatment with VD3 at 1000 nM resulted in a maximal decrease in proliferation by 1.3 ± 0.1-fold in BxPC-3, 1.7 ± 0.3-fold in HPAF-II expressing elevated VDR and 1.1 ± 0.3-fold in MIA PaCa-2. VD3 at 10 nM resulted a time-dependent increase in PGDH mRNA expression by 3.8 ± 0.3-fold in BxPC-3 and 7.7 ± 0.6-fold in HPAF-II, whereas expression remained unchanged in MIA PaCa-2. Conversely, COX-2 mRNA expression decreased by 0.5 ± 0.1-fold in BxPC-3 and 0.6 ± 0.1-fold in HPAF-II, but not in MIA PaCa-2. PGDH protein expression increased at 96 and 120 hrs following treatment with VD3 in BxPC-3 and HPAF-II whereas COX-2 protein expression decreased in HPAF-II cells but was abolished by 96 and 120 hrs in BxPC-3 cells. PGDH protein expression was increased at 120 hrs in MIA PaCa-2 following addition of VD3 but COX-2 protein expression in this cell line was not detected. VD3 decreased the PGDH transcriptional regulators SNAI1 protein expression by 120 hrs in BxPC-3 and HPAF-II cells but not MIA PaCa-2 whereas SNAI2 decreased in all cell types by 96 hrs. Knockdown of SNAI by siRNA at 100 nM in HPAF-II resulted in a 1.3 ± 0.3-fold decrease proliferation and 1.4 ± 0.1-fold decrease in PGE2 production. Combined treatment with 100 nM of siSNAI and 10 nM of VD3 did not result in synergistic decrease in proliferation or PGE2 production. CONCLUSION: PaCa cells expressing vitamin D receptors responded to VD3 treatment with a corresponding increase in PGDH coupled with a decrease in COX-2 expression. VD3 or siSNAI resulted in a decrease in cellular proliferation and PGE2 production but the combined treatment did not augment further decreases, suggesting that the decrease by VD3 could be mediated through SNAI regulation of PGDH. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 62. doi:1538-7445.AM2012-62

Upregulation of the high mobility group AT-hook 2 gene in acute aortic dissection is potentially associated with endothelial-mesenchymal transition.

The high mobility group AT-hook 2 (HMGA2) gene is proposed to regulate the genes involved in the epithelial-mesenchymal transition (EMT). One form of EMT is endothelial-mesenchymal transition (EndMT). We analyzed the expression profile of the HMGA2 gene in different human aortic diseases. Aortic specimens were collected from 51 patients, including 19 with acute aortic dissection, 26 with aortic aneurysm, two with Marfan syndrome and four aortic valves. Quantitative real-time polymerase chain reaction was carried out for HMGA2 and immunohistochemical analyses were performed for HMGA2, SNAI1, Vimentin, CD34, MKI-67 and TGFB1. The expression of let-7d microRNA, which is assumed to play a role in the regulation of HMGA2, was also quantified. The level of HMGA2 gene expression was significantly higher in acute aortic dissection compared with all the other samples (193.1 vs. 8.1 fold normalized to calibrator, P<0.001). The immunohistochemical investigation showed that HMGA2, SNAI1, and Vimentin proteins were mainly detected in the endothelial cells of the vasa vasorum. The HMGA2 gene is upregulated in acute aortic dissection. This is the first report describing a link between HMGA2 and acute aortic dissection. The HMGA2, SNAI1 and Vimentin proteins were mainly detected in the endothelium of the vasa vasorum. It seems that HMGA2 overexpression in acute aortic dissection occurs in a let-7d-independent manner and is associated with EndMT of the vasa vasorum.

Expression of transcription factor Snai1 and tubulointerstitial fibrosis in progressive nephropathy

Tubulointerstitial fibrosis (TIF) is seen as the final stage of progressive nephropathy, and the degree of TIF is reported to be a major determinant in renal outcomes. In recent years, epithelial-mesenchymal transition (EMT) and the zinc-finger transcription factor snail homolog 1 (Snai1) have each been implicated in the mechanism of TIF. The relationship between EMT and these transcription factors is unclear, however, so in this study we attempted to elucidate the correlation between the expression of Snai1 and clinical markers. We performed immunohistochemical staining on human renal tissue obtained from patients with diabetic nephropathy (DN), IgA nephropathy (IgAN), minimal change disease (MCD) and minor glomerular abnormality (MGA) using anti-Snai1 and anti-vimentin antibodies. We counted Snai1-positive and Snai1/vimentin double positive tubular epithelial cells. Snai1 protein was mainly observed in the nuclei of flattened, damaged tubular epithelial cells, especially in IgAN and DN, and positive cell numbers were significantly higher in IgAN than in MGA, MCD or DN. Snai1/vimentin double staining showed that some vimentin-positive tubular epithelial cells also contained Snai1-positive nuclei, and double positive cell numbers were increased in IgAN and DN. Statistical analysis revealed positive correlations between Snai1/vimentin double positive cell numbers and proteinuria and creatinine in IgAN. Positive correlations were also seen between Snai1/vimentin double positive cell numbers and the severity of proteinuria in DN. The results of this study indicate that Snai1 plays an important role in TIF in patients with progressive nephropathy.

Epithelial–mesenchymal transition with expression of SNAI1-induced chemoresistance in colorectal cancer

Background Previous reports have demonstrated that SNAI1 plays a role in epithelial–mesenchymal transition (EMT) through the suppression of CDH1. Its role in the pathology and regulation of EMT expression to chemoresistance in colorectal cancer (CRC) has not yet been fully elucidated. Methods Immunohistochemistry was performed to evaluate the expression of Snai1 protein in 30 primary CRC samples. The biological significance of Snai1 expression was studied by induction of the wild-type ( WT) and mutant SNAI1 gene in CRC SW480 cells. Results Examination of 20 surgical specimens of CRC indicated that Snai1 protein expression was localized outer regions of invasive tumors. Introduction of phosphorylation-defective active EMT forms, SNAI1-6SA and SNAI1-8SA, caused downregulation of CDH1 and upregulation of VIM compared with SNAI1- WT and the negative control (NC). Chemoresistance to 5-fluorouracil (IC50) was higher in SNAI1-6SA and SNAI1-8SA transfectants compared with SNAI1-WT and NC. All the above results were significantly different. Conclusion The present study demonstrated that Snai1 plays a role in CRC invasion through phosphorylation, suggesting a plausible mechanism for overcoming chemoresistance that will lead to the development of effective treatments for CRC.

Integration of Transforming Growth Factor β and RAS Signaling Silences a RAB5 Guanine Nucleotide Exchange Factor and Enhances Growth Factor-Directed Cell Migration

Transforming growth factor beta (TGF-beta) receptor (TbetaR) signaling contributes to normal development as well as tumorigenesis. Here we report that RIN1, a RAB5 guanine nucleotide exchange factor (GEF) and down regulator of receptor tyrosine kinases (RTKs), promotes TbetaR signaling through enhanced endocytosis. TbetaR activation induces SNAI1 (Snail), a transcription repressor that reduces RIN1 expression, providing a negative feedback mechanism to control TbetaR trafficking and downstream signaling. Persistent RAS signaling disrupts this equilibrium by stabilizing SNAI1 protein, resulting in strong silencing of RIN1 and stabilization of RTKs. TGF-beta-induced RIN1 silencing in breast cancer cells prolonged sensitivity to hepatocyte growth factor, a ligand for the MET-type RTK, and enhanced growth factor-directed cell motility. We conclude that in some tumor cells TbetaR and RAS signals are integrated through the silencing of RIN1, leading to a reduction in RAB5-mediated endocytosis. These findings shed new light on the basis for distinct interpretations of TGF-beta signaling by normal versus transformed cells.