Papers by Mohamed El Ezzy
Cancer research, Mar 22, 2024
Minerva Biotecnologica
Aim. In the Mediterranean countries, several described medicinal plants are derived from Lebanon.... more Aim. In the Mediterranean countries, several described medicinal plants are derived from Lebanon. According to Tohme et al. there are 2597 species in Lebanon. More than fifty two percent are endemic to Lebanon. In this paper we show that the ethanol fraction of the stem of Berberis libanotica is able to inhibit the viability of HTLV-1 positive (HuT-102) and HTLV-1 negative (CEM) cell lines of malignant T-cell leukemia. Methods. After traditional maceration to extract the ethanol fraction from Berberis libanotica stem, the in vitro viability was assayed. Results. The results suggest that Berberis libanotica (a Lebanese medicinal plant) contains a substantial amount of secondary metabolites such as alkaloids powerful in inhibiting the viability of HuT-102 and CEM cell lines. Conclusion. The obtained results demonstrate a novel anticancer property of Berberis libanotica stem extracts, in addition to the previously reported anti-inflammatory activity.
Inhibitory activities of antiestrogens on estrogen receptor alpha (ERα) range from mixed antagoni... more Inhibitory activities of antiestrogens on estrogen receptor alpha (ERα) range from mixed antagonism/agonism (selective ER modulators; SERMs) to complete antiestrogenicity associated with accelerated ERα turnover (selective ER degraders; SERDs). Here, we show using a panel of SERMs, SERDs and a PROTAC that efficient induction of ERα SUMOylation better accounts for complete transcriptional repression than increased suppression of coactivator recruitment or accelerated ERα degradation. Antiestrogen-induced ERα SUMOylation depends on the hydrophobicity of N-terminal residues of ligand binding domain (LBD) helix 12 (H12). L536 mutations, including those occurring in endocrine therapy-resistant breast cancer, abolished SUMOylation with all antiestrogens. Structures of the L536S human ERα LBD bound to fulvestrant analogs and molecular dynamics simulations predict dynamic side chain interactions with wild-type ERα H12 in the coactivator-binding groove and model the impact of L536 mutations....
Journal of Biological Chemistry
Oncogene, 2018
Antiestrogens (AEs) are widely used for treatment of estrogen receptor alpha (ERα)-positive breas... more Antiestrogens (AEs) are widely used for treatment of estrogen receptor alpha (ERα)-positive breast cancer, but display variable degrees of partial agonism in estrogen target tissues and breast cancer (BC) cells. The fact that BC cells resistant to selective ER modulators (SERMs) like tamoxifen (Tam) can still be sensitive to pure AEs, also called selective ER downregulators, suggests different mechanisms of action, some of which may contribute to the more complete suppression of estrogen target genes by pure AEs. We report herein that pure AEs such as fulvestrant induce transient binding of ERα to DNA, followed by rapid release after 30-40 min without loss of nuclear localization. Loss of DNA binding preceded receptor degradation and was not prevented by proteasome inhibition. Chromatin was less accessible in the presence of fulvestrant than with estradiol or Tam as early as 20 min following treatment, suggesting that chromatin remodeling by pure AEs at ERα target regions prevents transcription in spite of receptor binding. SUMO2/3 marks were detected on chromatin at the peak of ERα binding in cells treated with pure AEs, but not SERMs. Furthermore, decreasing SUMOylation by overexpressing the deSUMOylase SENP1 significantly delayed receptor release from DNA and de-repressed expression of estrogen target genes in the presence of fulvestrant, both in ERα-expressing MCF-7 cells and in transiently transfected ERnegative SK-BR-3 cells. Finally, mutation V534E, identified in a breast metastasis resistant to hormonal therapies, prevented ERα modification and resulted in increased transcriptional activity of estrogen target genes in the presence of fulvestrant in SK-BR-3 cells. Together, our results establish a role for SUMOylation in achieving a more complete transcriptional shut-off of estrogen target genes by pure AEs vs. SERMs in BC cells.
Proceedings of the National Academy of Sciences of the United States of America, Mar 27, 2018
There is currently an unmet need for versatile techniques to monitor the assembly and dynamics of... more There is currently an unmet need for versatile techniques to monitor the assembly and dynamics of ternary complexes in live cells. Here we describe bioluminescence resonance energy transfer with fluorescence enhancement by combined transfer (BRETFect), a high-throughput technique that enables robust spectrometric detection of ternary protein complexes based on increased energy transfer from a luciferase to a fluorescent acceptor in the presence of a fluorescent intermediate. Its unique donor-intermediate-acceptor relay system is designed so that the acceptor can receive energy either directly from the donor or indirectly via the intermediate in a combined transfer, taking advantage of the entire luciferase emission spectrum. BRETFect was used to study the ligand-dependent cofactor interaction properties of the estrogen receptors ERα and ERβ, which form homo- or heterodimers whose distinctive regulatory properties are difficult to dissect using traditional methods. BRETFect uncovered...
Journal of molecular endocrinology, Jan 11, 2016
About 70% of breast tumors express estrogen receptor alpha (ERα), which mediates the proliferativ... more About 70% of breast tumors express estrogen receptor alpha (ERα), which mediates the proliferative effects of estrogens on breast epithelial cells, and are candidates for treatment with antiestrogens, steroidal or non-steroidal molecules designed to compete with estrogens and antagonize ERs. The variable patterns of activity of antiestrogens (AEs) in estrogen target tissues and the lack of systematic cross-resistance between different types of molecules have provided evidence for different mechanisms of action. AEs are typically classified as Selective Estrogen Receptor Modulators (SERMs), which display tissue-specific partial agonist activity (e.g. tamoxifen and raloxifene), or as pure AEs (e.g. fulvestrant), which enhance ERα post-translational modification by ubiquitin-like molecules and accelerate its proteasomal degradation. Characterization of second and third generation AEs however suggests induction of diverse ERα structural conformations, resulting in variable degrees of re...
Proceedings of the National Academy of Sciences, 2008
1,25-dihydroxyvitamin D 3 (1,25D) regulates gene expression by signaling through the nuclear vita... more 1,25-dihydroxyvitamin D 3 (1,25D) regulates gene expression by signaling through the nuclear vitamin D receptor (VDR) transcription factor and exhibits calcium homeostatic, anticancer, and immunomodulatory properties. Histone deacetylase inhibitors (HDACis) alter nuclear and cytoplasmic protein acetylation, modify gene expression, and have potential for treatment of cancer and other indications. The function of nuclear receptor ligands, including 1,25D, can be enhanced in combination with HDACi. We designed triciferol, a hybrid molecule in which the 1,25D side chain was replaced with the dienyl hydroxamic acid of HDACi trichostatin A. Triciferol binds directly to the VDR, and functions as an agonist with 1,25D-like potency on several 1,25D target genes. Moreover, unlike 1,25D, triciferol induces marked tubulin hyperacetylation, and augments histone acetylation at concentrations that largely overlap those where VDR agonism is observed. Triciferol also exhibits more efficacious antipr...
Molecular and Cellular Biology, 2012
The selective estrogen receptor downregulator (SERD) fulvestrant can be used as second-line treat... more The selective estrogen receptor downregulator (SERD) fulvestrant can be used as second-line treatment for patients relapsing after treatment with tamoxifen, a selective estrogen receptor modulator (SERM). Unlike tamoxifen, SERDs are devoid of partial agonist activity. While the full antiestrogenicity of SERDs may result in part from their capacity to downregulate levels of estrogen receptor alpha (ERα) through proteasome-mediated degradation, SERDs are also fully antiestrogenic in the absence of increased receptor turnover in HepG2 cells. Here we report that SERDs induce the rapid and strong SUMOylation of ERα in ERα-positive and -negative cell lines, including HepG2 cells. Four sites of SUMOylation were identified by mass spectrometry analysis. In derivatives of the SERD ICI164,384, SUMOylation was dependent on the length of the side chain and correlated with full antiestrogenicity. Preventing SUMOylation by the overexpression of a SUMO-specific protease (SENP) deSUMOylase partiall...
Journal of the Endocrine Society
Disclosure: A. Vallet: None. M. Diennet: None. K. Thiombane: None. A. Vivet: None. S. Weber: None... more Disclosure: A. Vallet: None. M. Diennet: None. K. Thiombane: None. A. Vivet: None. S. Weber: None. M. El Ezzy: None. F. Shaikh: None. J. Poupart: None. R. Mendoza-Sanchez: None. D. Schuetz: None. A. Marinier: None. G.L. Greene: None. S.W. Fanning: None. S.N. Mader: None. Inhibitory activities of antiestrogens on estrogen receptor alpha (ERα) range from mixed antagonism/agonism (selective ER modulators; SERMs) to complete antiestrogenicity associated with accelerated ERα turnover (selective ER degraders; SERDs). Using a panel of SERMs, SERDs and PROTACs, we show that antiestrogens induce variable degrees of SUMOylation of ERα and that efficient induction of SUMOylation, rather than increased suppression of coactivator recruitment or accelerated ERα degradation, correlates with suppression of ERα basal and induced transcriptional activity in reporter assays. Antiestrogens did not induce SUMOylation of ERβ and did not suppress its basal transcriptional activity in the same assays. Chim...
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Papers by Mohamed El Ezzy