Inhibiting estrogen responses in breast cancer cells using a fusion protein encoding estrogen receptor-α and the transcriptional repressor PLZF

Buluwela, Lakjaya; Pike, Joanna; Mazhar, Danish; Kamalati, Tahereh; Hart, Stephen M.; Al-Jehani, R.; Yahaya, H.; Patel, Naina; Sarwarl, N.; Heathcote, Dean A.; Schwickerath, Oliver; Phoenix, Fladia; Hill, Richard; Aboagye, Eric O.; Shousha, Sami; Waxman, Jonathan; Lemoine, Nick R.; Zelent, Arthur; Coombes, R. Charles; Ali, Simak

doi:10.1038/sj.gt.3302421

Cited by 18 publications

(11 citation statements)

References 40 publications

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“…RNA was prepared and RT-PCR performed as described previously [17]. For Immunoblotting MCF-7 and MLET cells (1x10 6 ) were seeded in 10-cm plates DMEM containing 10% FCS and lysed after 48 hours, as described [17].…”

Section: Rt-pcr Analysismentioning

confidence: 99%

“…For Immunoblotting MCF-7 and MLET cells (1x10 6 ) were seeded in 10-cm plates DMEM containing 10% FCS and lysed after 48 hours, as described [17]. For experiments where ligands were to be added, the cells were incubated in DMEM-PR containing 10% DSS for three days prior to seeding.…”

Section: Rt-pcr Analysismentioning

confidence: 99%

“…Cell lysates were prepared 24 hours later. Immunoblotting was carried out as described previously [17], using antibodies detailed in Supplementary Material.…”

Section: Rt-pcr Analysismentioning

confidence: 99%

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Transient over-expression of estrogen receptor-α in breast cancer cells promotes cell survival and estrogen-independent growth

Tolhurst

Thomas

Kyle

et al. 2010

Breast Cancer Res Treat

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Section: Rt-pcr Analysismentioning

confidence: 99%

Section: Rt-pcr Analysismentioning

confidence: 99%

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Transient over-expression of estrogen receptor-α in breast cancer cells promotes cell survival and estrogen-independent growth

Tolhurst

Thomas

Kyle

et al. 2010

Breast Cancer Res Treat

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“…As a control we used an MCF-7-TO (MCF-7-Tet-Off)-derived cell line, JP13, that conditionally overexpresses a protein composed of the zinc finger transcriptional repressor PLZF fused to ER␣ (PLZF-ER␣), acting as a dominant-negative that inhibits expression of estrogen-regulated genes and estrogen-stimulated growth of MCF-7 cells (24). Following E2 stimulation and before microarray hybridization, we assessed the reliability of the system using quantitative real time PCR (RT-qPCR) to reveal expression levels of the ER␣-regulated gene GREB1 [supporting information (SI) Fig.…”

Section: Er␣ Induction Reveals Pri-mir-17-92 Upregulationmentioning

confidence: 99%

The estrogen receptor-α-induced microRNA signature regulates itself and its transcriptional response

Castellano

Giamas²,

Jacob³

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

316

242

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Following estrogenic activation, the estrogen receptor-␣ (ER␣) directly regulates the transcription of target genes via DNA binding. MicroRNAs (miRNAs) modulated by ER␣ have the potential to fine tune these regulatory systems and also provide an alternate mechanism that could impact on estrogen-dependent developmental and pathological systems. Through a microarray approach, we identify the subset of microRNAs (miRNAs) modulated by ER␣, which include upregulation of miRNAs derived from the processing of the paralogous primary transcripts (pri-) mir-17-92 and mir-106a-363. Characterization of the mir-17-92 locus confirms that the ER␣ target protein c-MYC binds its promoter in an estrogen-dependent manner. We observe that levels of pri-mir-17-92 increase earlier than the mature miRNAs derived from it, implicating precursor cleavage modulation after transcription. Pri-mir-17-92 is immediately cleaved by DROSHA to pre-miR-18a, indicating that its regulation occurs during the formation of the mature molecule from the precursor. The clinical implications of this novel regulatory system were confirmed by demonstrating that pre-miR-18a was significantly upregulated in ER␣-positive compared to ER␣-negative breast cancers. Mechanistically, miRNAs derived from these paralogous pri-miRNAs (miR-18a, miR-19b, and miR-20b) target and downregulate ER␣, while a subset of pri-miRNA-derived miRNAs inhibit protein translation of the ER␣ transcriptional p160 coactivator, AIB1. Therefore, different subsets of miRNAs identified act as part of a negative autoregulatory feedback loop. We propose that ER␣, c-MYC, and miRNA transcriptional programs invoke a sophisticated network of interactions able to provide the wide range of coordinated cellular responses to estrogen.AIB1 ͉ autoregulatory feedback loop ͉ primary transcript ͉ processing U pon 17-␤-estradiol (E2) binding, estrogen receptors (ERs) mediate transcription by interacting directly to specific estrogen response elements (EREs) located in the promoter/ enhancer region of its target genes or indirectly by tethering to nuclear proteins, such as AP1 and SP1 transcription factors (2-4). The cellular response to estrogen is highly regulated at multiple levels including transcription, RNA stability, and posttranslational modifications (5-8). Following treatment with E2, ER␣ transcription and mRNA stability is substantially reduced within 1 h of stimulation (7). Furthermore, E2-ER␣ interactions accelerate receptor degradation through the ubiquitinproteasome pathway, an effect associated with its major coactivator AIB1 (8).MicroRNAs (miRNAs) are a class of noncoding short RNAs, 21-24 nucleotides (nt) in length, that play a role in gene regulation. They downregulate expression of their target genes by base pairing to the 3Ј-UTR of target messenger RNAs (mRNAs) (9). During their biogenesis most miRNAs are transcribed as part of a longer transcript named pri-miRNA (10). These molecules are processed inside the nucleus by DROSHA, producing a pre-miRNA that is a 70-nt ''imperfect'' stem loop ...

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“…Expression of fusion protein between ERα and the promyelocytic leukemia zinc-finger (PLZF) protein, a transcriptional repressor that acts through chromatin remodeling inhibited growth of estrogen regulated cells when PLZF-ERalpha expression is induced in vitro and in vivo showing it could be useful for treatment of breast cancer [Buluwela et al, 2005].…”

Section: Inhibiting Steroid Receptorsmentioning

confidence: 99%

Targeting Transcription Factors for Cancer Gene Therapy

Libermann¹,

Zerbini

2006

CGT

133

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A high proportion of oncogenes and tumor suppressor genes encode transcription factors. Deregulated expression or activation and inactivation of transcription factors as well as mutations and translocations play critical roles in tumorigenesis. Furthermore, the majority of oncogenic signaling pathways converge on sets of transcription factors that ultimately control gene expression patterns resulting in tumor formation and progression as well as metastasis. Under normal physiological conditions whole sets of genes with similar functions are regulated by highly specific, tightly regulated upstream transcriptional regulators, whereas in cancer aberrant activation of these transcription factors leads to deregulated expression of multiple gene sets associated with tumor development and progression. The activity of these transcription factors can be modulated by multiple mechanisms including posttranslational modifications. Activation or inactivation of transcription factors promote cancer development, cell survival and proliferation and induce tumor angiogenesis. Since many of these transcription factors are inactive under normal physiological conditions and their expression and activities are tightly regulated, these transcription factors represent highly desirable and logical points of therapeutical interference in cancer development and progression. Three major families of transcription factors have emerged as important players in human cancer and are validated targets in drug discovery for cancer therapy: 1) the NF-kappaB and AP-1 families of transcription factors, 2) the STAT family members and 3) the steroids receptors. This review aims to elucidate the divergent molecular mechanisms involved in the deregulated activation of transcription factor signaling in malignant transformation, although additional transcription factor families such as the Ets factors, ATF family members, basic helix-loop-helix transcription factors etc. are additional critical transcriptional regulators in human cancer. We explore new approaches to specifically inhibit these transcription factors in cancer in order to validate them as a drug targets. Efforts to develop novel viral vectors for therapeutic applications are also discussed.

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Inhibiting estrogen responses in breast cancer cells using a fusion protein encoding estrogen receptor-α and the transcriptional repressor PLZF

Cited by 18 publications

References 40 publications

Transient over-expression of estrogen receptor-α in breast cancer cells promotes cell survival and estrogen-independent growth

Transient over-expression of estrogen receptor-α in breast cancer cells promotes cell survival and estrogen-independent growth

The estrogen receptor-α-induced microRNA signature regulates itself and its transcriptional response

Targeting Transcription Factors for Cancer Gene Therapy

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