Irida Kastrati

University of Illinois at Chicago, Chicago, Illinois, United States

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Publications (10)42.3 Total impact

  • I Kastrati, E Canestrari, J Frasor
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    ABSTRACT: Crosstalk between estrogen receptor (ER) and the inflammatory nuclear factor κB (NFκB) pathway in ER+ breast cancers may contribute to a more aggressive phenotype. Pleckstrin Homology-Like Domain, Family A, member 1 (PHLDA1), a target gene of ER-NFκB crosstalk, has been implicated in cell survival and stem cell properties. 17β-estradiol (E2), acting through ERα, and pro-inflammatory cytokines, acting through NFκB, increase the nascent transcript and PHLDA1 messenger RNA stability, indicating both transcriptional and post-transcriptional control of PHLDA1 expression. We show that PHLDA1 is a direct target of miR-181 and that mature miR-181a and b, as well as their host gene, are synergistically downregulated by E2 and tumor necrosis factor α, also in an ER- and NFκB-dependent manner. Thus, ER and NFκB work together to upregulate PHLDA1 directly through enhanced transcription and indirectly through repression of miR-181a and b. Previous studies have suggested that PHLDA1 may be a stem cell marker in the human intestine that contributes to tumorigenesis. Our findings that PHLDA1 is upregulated in mammospheres (MS) of ER+ breast cancer cells and that PHLDA1 knockdown impairs both MS formation and the expansion of aldehyde dehydrogenase (ALDH)-positive population, suggest that PHLDA1 may play a similar role in breast cancer cells. Upregulation of PHLDA1 in MS is largely dependent on the NFκB pathway, with downregulated miR-181 expression a contributing factor. Over-expression of miR-181 phenocopied PHLDA1 knockdown and significantly impaired MS formation, which was reversed, in part, by protection of the PHLDA1 3' untranslated region (UTR) or overexpression of PHLDA1 lacking the 3'UTR. Furthermore, we find that elevated PHLDA1 expression is associated with a higher risk of distant metastasis in ER+ breast cancer patients. Altogether, these data suggest that high PHLDA1 expression is controlled through an ER-NFκB-miR-181 regulatory axis and may contribute to a poor clinical outcome in patients with ER+ breast tumors by enhancing stem-like properties in these tumors.Oncogene advance online publication, 23 June 2014; doi:10.1038/onc.2014.180.
    Oncogene 06/2014; · 8.56 Impact Factor
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    ABSTRACT: Nitroglycerin is an organic nitrate that has been used in the clinical treatment of angina for 130 years, yet important details of its mechanism of action remain unanswered. The biological activity of nitrates suggests that they are bioactivated to NO via a three-electron reduction. The involvement of free or bound protein thiols in this reduction has often been proposed. To examine the involvement of thiyl radicals in such a process, the photochemical generation of benzenethiyl radical from thiol and disulfide precursors was studied in the presence of isopropyl nitrate. Analysis of reaction products and kinetics led to the conclusion that photolysis of the nitrate to NO2 dominated the observed photochemistry. Formation of sulfonothioate and NO as products, and trapping of NO2 by 4-chlorophenol, indicated a mechanism involving oxygen atom transfer from N to S via a thionitrate intermediate. The results of the study did not indicate a rapid reaction between thiyl radical and organic nitrate. Despite weak nitrate absorption of light >300 nm and a relatively high BDE for homolysis to give NO2, the photochemistry under thiyl-generating conditions was driven by nitrate photolysis to NO2. A novel nitrate, containing a phenyl disulfanyl group linked to nitrate groups, did not undergo photolysis to NO2 or generate sulfonothioate, but did yield NO. These observations suggest that reaction between thiyl radicals and nitrates leading to NO release is a viable pathway, but it is subservient to other competing reactions, such as photolysis, in the case of IPN, and reaction with thiolate, in the case of the novel nitrate.
    Canadian Journal of Chemistry 02/2011; · 0.96 Impact Factor
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    ABSTRACT: There is association between exposure to estrogens and the development and progression of hormone-dependent gynecological cancers. Chemical carcinogenesis by catechol estrogens derived from oxidative metabolism is thought to contribute to breast cancer, yet exact mechanisms remain elusive. Malignant transformation was studied in MCF-10A human mammary epithelial cells, since estrogens are not proliferative in this cell line. The human and equine estrogen components of estrogen replacement therapy (ERT) and their catechol metabolites were studied, along with the influence of co-administration of selective estrogen receptor modulators (SERMs), raloxifene and desmethyl-arzoxifene (DMA), and histone deacetylase inhibitors. Transformation was induced by human estrogens, and selectively by the 4-OH catechol metabolite, and to a lesser extent by an equine estrogen metabolite. The observed estrogen-induced upregulation of CYP450 1B1 in estrogen receptor negative MCF-10A cells, was compatible with a causal role for 4-OH catechol estrogens, as was attenuated transformation by CYP450 inhibitors. Estrogen-induced malignant transformation was blocked by SERMs correlating with a reduction in formation of nucleobase catechol estrogen (NCE) adducts and formation of 8-oxo-dG. NCE adducts can be formed consequent to DNA abasic site formation, but NCE adducts were also observed on incubation of estrogen quinones with free nucleotides. These results suggest that NCE adducts may be a biomarker for cellular electrophilic stress, which together with 8-oxo-dG as a biomarker of oxidative stress correlate with malignant transformation induced by estrogen oxidative metabolites. The observed attenuation of transformation by SERMs correlated with these biomarkers and may also be of clinical significance in breast cancer chemoprevention.
    PLoS ONE 01/2011; 6(11):e27876. · 3.73 Impact Factor
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    ABSTRACT: Estrogen action, via both nuclear and extranuclear estrogen receptors (ERs), induces a variety of cellular signals that are prosurvival or proliferative, whereas nitric oxide (NO) can inhibit apoptosis via caspase S-nitrosylation and via activation of soluble guanylyl cyclase to produce cGMP. The action of 17β-estradiol (E(2)) at ER is known to elicit NO signaling via activation of NO synthase (NOS) in many tissues. The MCF-10A nontumorigenic, mammary epithelial cell line is genetically stable and insensitive to estrogenic proliferation. In this cell line, estrogens or NOS inhibitors alone had no significant effect, whereas in combination, apoptosis was induced rapidly in the absence of serum; the presence of inducible NOS was confirmed by proteomic analysis. The application of pharmacological agents determined that apoptosis was dependent upon NO/cGMP signaling via cyclic GMP (cGMP)-dependent protein kinase and could be replicated by inhibition of the phosphatidylinositol 3 kinase/serine-threonine kinase pathway prior to addition of E(2). Apoptosis was confirmed by nuclear staining and increased caspase-3 activity in E(2) + NOS inhibitor-treated cells. Apoptosis was partially inhibited by a pure ER antagonist and replicated by agonists selective for extranuclear ER. Cells were rescued from E(2)-induced apoptosis after NOS blockade, by NO-donors and cGMP pathway agonists; preincubation with NO donors was required. The NOS and ER status of breast cancer tissues is significant in etiology, prognosis, and therapy. In this study, apoptosis of preneoplastic mammary epithelial cells was triggered by estrogens via a rapid, extranuclear ER-mediated response, after removal of an antiapoptotic NO/cGMP/cGMP-dependent protein kinase signal.
    Endocrinology 10/2010; 151(12):5602-16. · 4.72 Impact Factor
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    ABSTRACT: Raloxifene and arzoxifene are benzothiophene selective estrogen receptor modulators (SERMs) of clinical use in postmenopausal osteoporosis and treatment of breast cancer and potentially in hormone replacement therapy. The benefits of arzoxifene are attributed to improved bioavailability over raloxifene, whereas the arzoxifene metabolite, desmethylarzoxifene (DMA) is a more potent antiestrogen. As polyaromatic phenolics, benzothiophene SERMs undergo oxidative metabolism to electrophilic quinoids. The long-term clinical use of SERMs demands increased understanding of correlations between structure and toxicity, with metabolism being a key component. A homologous series of 4'-substituted 4'-desmethoxyarzoxifene derivatives was developed, and metabolism was studied in liver and intestinal microsomes. Formation of glutathione conjugates was assayed in rat liver microsomes and novel adducts were characterized by liquid chromatography-tandem mass spectrometry. Formation of glucuronide conjugates was assayed in human intestine and liver microsomes, demonstrating formation of glucuronides ranging from 5 to 100% for the benzothiophene SERMs: this trend was inversely correlated with the loss of parent SERM in rat liver microsomal incubations. Molecular orbital calculations generated thermodynamic parameters for oxidation that correlated with Hammett substituent constants; however, metabolism in liver microsomes correlated with a combination of both Hammett and Hansch lipophilicity parameters. The results demonstrate a rich oxidative chemistry for the benzothiophene SERMs, the amplitude of which can be powerfully modulated, in a predictable manner, by structural tuning of the 4'-substituent. The predicted extensive metabolism of DMA was confirmed in vivo and compared with the relatively stable arzoxifene and F-DMA.
    Drug metabolism and disposition: the biological fate of chemicals 11/2008; 37(1):161-9. · 3.74 Impact Factor
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    ABSTRACT: Oxidative metabolism of estrogens has been associated with genotoxicity. O-methylation of catechol estrogens is considered as a protective mechanism. 4-Methoxyequilenin (4-MeOEN) is the O-methylated product of 4-hydroxyequilenin (4-OHEN). 4-OHEN, the major catechol metabolite of the equine estrogens present in the most widely prescribed hormone replacement therapeutics, causes DNA damage via quinone formation. In this study, estrogen receptor (ERa) binding of 4-MeOEN was compared with estradiol (E2) and equilenin derivatives including 4-BrEN using computer modeling, estrogen response element (ERE)-luciferase induction in MCF-7 cells, and alkaline phosphatase (AP) induction in Ishikawa cells. 4-MeOEN induced AP and luciferase with nanomolar potency and displayed a similar profile of activity to E2. Molecular modeling indicated that MeOEN could be a ligand for ERa despite no binding being observed in the ERa competitive binding assay. Methylation of 4-OHEN may not represent a detoxification pathway, since 4-MeOEN is a full estrogen agonist with nanomolar potency.
    Advances in experimental medicine and biology 02/2008; 617:601-7. · 1.83 Impact Factor
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    ABSTRACT: The search for the "ideal" selective estrogen receptor modulator (SERM) as a substitute for hormone replacement therapy (HRT) or use in cancer chemoprevention has focused on optimization of estrogen receptor (ER) ligand binding. Based on the clinical and preclinical benzothiophene SERMs, raloxifene and arzoxifene, a family of SERMs has been developed to modulate activity and oxidative lability. Antiestrogenic potency measured in human endometrial and breast cancer cells, and ER ligand binding data were correlated and seen to provide a guide to SERM design only when viewed in toto. The in vitro studies were extended to the juvenile rat model, in which the desired antiestrogenic profile and putative cardiovascular benefits of SERMs were observed.
    ChemMedChem 11/2007; 2(10):1520-6. · 2.84 Impact Factor
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    ABSTRACT: 4-Methoxyequilenin (4-MeOEN) is an O-methylated metabolite in equine estrogen metabolism. O-methylation of catechol estrogens is considered as a protective mechanism; however, comparison of the properties of 4-MeOEN with estradiol (E(2)) in human breast cancer cells showed that 4-MeOEN is a proliferative, estrogenic agent that may contribute to carcinogenesis. 4-MeOEN results from O-methylation of 4-hydroxyequilenin, a major catechol metabolite of the equine estrogens present in hormone replacement therapeutics, which causes DNA damage via quinone formation, raising the possibility of synergistic hormonal and chemical carcinogenesis. 4-MeOEN induced cell proliferation with nanomolar potency and induced estrogen response element (ERE)-mediated gene transcription of an ERE-luciferase reporter and the endogenous estrogen-responsive genes pS2 and TGF-alpha. These estrogenic actions were blocked by the antiestrogen ICI 182,780. In the standard radioligand estrogen receptor (ER) binding assay, 4-MeOEN showed very weak binding. To test for alternate ligand-ER-independent mechanisms, the possibility of aryl hydrocarbon receptor (AhR) binding and ER-AhR cross talk was examined using a xenobiotic response element-luciferase reporter and using AhR small interfering RNA silencing in the ERE-luciferase reporter assay. The results negated the possibility of AhR-mediated estrogenic activity. Comparison of gene transcription time course, ER degradation, and rapid activation of MAPK/ERK in MCF-7 cells demonstrated that the actions of 4-MeOEN mirrored those of E(2) with potency for classical and nonclassical estrogenic pathways bracketing that of E(2). Methylation of 4-OHEN may not represent a detoxification pathway because 4-MeOEN is a full, potent estrogen agonist.
    Endocrinology 11/2007; 148(10):4793-802. · 4.72 Impact Factor
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    ABSTRACT: The benzothiophene selective estrogen receptor modulators (SERM) raloxifene and arzoxifene are in clinical use and clinical trials for chemoprevention of breast cancer and other indications. These SERMs are "oxidatively labile" and therefore have potential to activate antioxidant responsive element (ARE) transcription of genes for cytoprotective phase II enzymes such as NAD(P)H-dependent quinone oxidoreductase 1 (NQO1). To study this possible mechanism of cancer chemoprevention, a family of benzothiophene SERMs was developed with modulated redox activity, including arzoxifene and its metabolite desmethylarzoxifene (DMA). The relative antioxidant activity of these SERMs was assayed and correlated with induction of NQO1 in murine and human liver cells. DMA was found to induce NQO1 and to activate ARE more strongly than other SERMs, including raloxifene and 4-hydroxytamoxifen. Livers from female, juvenile rats treated for 3 days with estradiol and/or with the benzothiophene SERMs arzoxifene, DMA, and F-DMA showed substantial induction of NQO1 by the benzothiophene SERMs. No persuasive evidence in this assay or in MCF-7 breast cancer cells was obtained of a major role for the estrogen receptor in induction of NQO1 by the benzothiophene SERMs. These results suggest that arzoxifene might provide chemopreventive benefits over raloxifene and other SERMs via metabolism to DMA and stimulation of ARE-mediated induction of phase II enzymes. The correlation of SERM structure with antioxidant activity and NQO1 induction also suggests that oxidative bioactivation of SERMs may be modulated to enhance chemopreventive activity.
    Molecular Cancer Therapeutics 10/2007; 6(9):2418-28. · 5.60 Impact Factor
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    ABSTRACT: The regulation of estrogenic and antiestrogenic effects of selective estrogen receptor modulators (SERMs) is thought to underlie their clinical use. Most SERMs are polyaromatic phenols susceptible to oxidative metabolism to quinoids, which are proposed to be genotoxic. Conversely, the redox reactivity of SERMs may contribute to antioxidant and chemopreventive mechanisms, providing a new approach to improve the therapeutic properties of SERMs. An improved synthetic strategy was developed to generate a family of benzothiophene SERMs. Using computational modeling methods and measurements of antioxidant activity and estrogen receptor (ER) ligand binding, this SERM family was shown to provide both a range of ERalpha/ERbeta selectivity from 1.2- to 67-fold and a range of redox activity. Antioxidant activity was successfully modulated by varying a substituent remote from the OH group; the source of the antioxidant capacity. An efficient synthetic procedure is reported yielding benzothiophene SERMs wherein redox activity and ER affinity are modulated.
    Journal of Medicinal Chemistry 06/2007; 50(11):2682-92. · 5.61 Impact Factor

Publication Stats

69 Citations
42.30 Total Impact Points

Institutions

  • 2007–2014
    • University of Illinois at Chicago
      • • Department of Physiology and Biophysics (Chicago)
      • • Department of Medicinal Chemistry and Pharmacognosy
      • • College of Pharmacy
      Chicago, Illinois, United States