Targeted inhibition of Snail family zinc finger transcription factors by oligonucleotide-Co(III) Schiff base conjugate

Department of Cell and Molecular Biology, Northwestern University, Evanston, Illinois, United States
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 09/2009; 106(33):13667-72. DOI: 10.1073/pnas.0906423106
Source: PubMed


A transition metal complex targeted for the inhibition of a subset of zinc finger transcription factors has been synthesized and tested in Xenopus laevis. A Co(III) Schiff base complex modified with a 17-bp DNA sequence is designed to selectively inhibit Snail family transcription factors. The oligonucleotide-conjugated Co(III) complex prevents Slug, Snail, and Sip1 from binding their DNA targets whereas other transcription factors are still able to interact with their target DNA. The attachment of the oligonucleotide to the Co(III) complex increases specificity 150-fold over the unconjugated complex. Studies demonstrate that neither the oligo, or the Co(III) Schiff base complex alone, are sufficient for inactivation of Slug at concentrations that the conjugated complex mediates inhibition. Slug, Snail, and Sip1 have been implicated in the regulation of epithelial-to-mesenchymal transition in development and cancer. A complex targeted to inactivate their transcriptional activity could prove valuable as an experimental tool and a cancer therapeutic.

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    • "By blocking Snail, cell migration and invasion, and, consequently, metastasis of tumor cells are diminished, thus improving the clinical outcome. With the Schiff base complex Co(III)-Ebox, a highly selective inhibitor that prevents Snail from binding to its DNA target has recently been identified [32] and has proven to be a potent inhibitor of Snail-mediated transcriptional repression in breast cancer cells [31]. It is thus feasible that this selective inhibitor could be used to therapeutically target Snail and other zinc-finger transcription factors such as Slug in human cancers. "
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    ABSTRACT: Background: Snail is a key regulator of epithelial-mesenchymal transition of tumor cells. Several studies have shown nuclear Snail expression to be a negative prognostic factor in human cancer, where it is generally associated with more aggressive tumor behavior and worse survival. Objectives and methods: To further explore the role of Snail expression in breast cancer, we conducted a study on a tissue microarray, encompassing 1043 breast cancer cases. Results: A total of 265 (25.4%) breast cancers were positive for Snail. Snail expression was significantly associated with greater tumor size, higher tumor stage and grade, positive lymph node status, and hormone receptor negative status and was differently expressed in the intrinsic subtypes of breast cancer, being the highest in the basal-like subtype and the lowest in the luminal A subtype. In multivariate analysis, Snail proved to be an independent negative prognostic factor for OS. In the intrinsic subtypes, Snail expression was a negative prognostic factor for OS in the luminal B HER2(-), the luminal B HER2(+), and the basal-like subtype. Conclusions: This is the first study demonstrating that nuclear Snail expression is an independent negative predictor of prognosis in breast cancer, thus suggesting that it may represent a potential therapeutic target.
    Full-text · Article · Sep 2013 · Disease markers
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    • "SNAIL homologues are thought to act as transcriptional repressors and show a conserved function in mesoderm development from flies to mammals [5]. Their role in de-lamination and migration is mediated by triggering the processes that leads to the acquisition of EMT by directly repressing the transcription of E-cadherin [6]. Activation of SNAIL has been shown in pathological specimens at the invasive front of chemically induced mouse skin tumors, mammary, ovarian and in human breast carcinomas [7]. "
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    ABSTRACT: HMLEs (HMLE-SNAIL and Kras-HMLE, Kras-HMLE-SNAIL pairs) serve as excellent model system to interrogate the effect of SNAIL targeted agents that reverse epithelial-to-mesenchymal transition (EMT). We had earlier developed a SNAIL-p53 interaction inhibitor (GN-25) that was shown to suppress SNAIL function. In this report, using systems biology and pathway network analysis, we show that GN-25 could cause reversal of EMT leading to mesenchymal-to-epithelial transition (MET) in a well-recognized HMLE-SNAIL and Kras-HMLE-SNAIL models. GN-25 induced MET was found to be consistent with growth inhibition, suppression of spheroid forming capacity and induction of apoptosis. Pathway network analysis of mRNA expression using microarrays from GN-25 treated Kras-HMLE-SNAIL cells showed an orchestrated global re-organization of EMT network genes. The expression signatures were validated at the protein level (down-regulation of mesenchymal markers such as TWIST1 and TWIST2 that was concurrent with up-regulation of epithelial marker E-Cadherin), and RNAi studies validated SNAIL dependent mechanism of action of the drug. Most importantly, GN-25 modulated many major transcription factors (TFs) such as inhibition of oncogenic TFs Myc, TBX2, NR3C1 and led to enhancement in the expression of tumor suppressor TFs such as SMAD7, DD1T3, CEBPA, HOXA5, TFEB, IRF1, IRF7 and XBP1, resulting in MET as well as cell death. Our systems and network investigations provide convincing pre-clinical evidence in support of the clinical application of GN-25 for the reversal of EMT and thereby reducing cancer cell aggressiveness.
    Full-text · Article · Sep 2013 · BMC Systems Biology
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    • "MDA-MB-231 cells are metastatic breast cancer cells that express multiple zinc finger transcriptional repressors, including Snai1 (Figure S1), Snai2, Zeb1 and Zeb2, all of which can bind Eboxes in the E-cadherin promoter and regulate EMT [32], [33], [34]. We have shown that DNA binding by Snai1, Snai2 and Zeb2 is inhibited by Co(III)-Ebox in vitro [27]. MDA-MB-231 cells therefore make an excellent model in which to assess ability of Co(III)-Ebox to inactivate the function of multiple distinct endogenous targets and alleviate the transcriptional repression of the E-cadherin promoter observed in these cells. "
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    ABSTRACT: Snail family proteins are core EMT (epithelial-mesenchymal transition) regulatory factors that play essential roles in both development and disease processes and have been associated with metastasis in carcinomas. Snail factors are required for the formation of neural crest stem cells in most vertebrate embryos, as well as for the migratory invasive behavior of these cells. Snail factors have recently been linked to the formation of cancer stem cells, and expression of Snail proteins may be associated with tumor recurrence and resistance to chemotherapy and radiotherapy. We report that Co(III)-Ebox is a potent inhibitor of Snail-mediated transcriptional repression in breast cancer cells and in the neural crest of Xenopus. We further show that the activity of Co(III)-Ebox can be modulated by temperature, increasing the utility of this conjugate as a Snail inhibitor in model organisms. We exploit this feature to further delineate the requirements for Snail function during neural crest development, showing that in addition to the roles that Snail factors play in neural crest precursor formation and neural crest EMT/migration, inhibition of Snail function after the onset of neural crest migration leads to a loss of neural crest derived melanocytes. Co(III)-Ebox-mediated inhibition therefore provides a powerful tool for analysing the function of these core EMT factors with unparalleled temporal resolution. Moreover, the potency of Co(III)-Ebox as a Snail inhibitor in breast cancer cells suggests its potential as a therapeutic inhibitor of tumor progression and metastasis.
    Preview · Article · Feb 2012 · PLoS ONE
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