The Experts below are selected from a list of 1950 Experts worldwide ranked by ideXlab platform

Robert Clarke - One of the best experts on this subject based on the ideXlab platform.

  • nf κb signaling is required for xbp1 unspliced and spliced mediated effects on antiestrogen responsiveness and cell fate decisions in breast cancer
    Molecular and Cellular Biology, 2015
    Co-Authors: Anni Warri, Rebecca B. Riggins, Lu Jin, Alan Zwart, Hongbin Fang, Robert Clarke
    Abstract:

    Antiestrogen therapy induces the unfolded protein response (UPR) in estrogen receptor-positive (ER(+)) breast cancer. X-box binding protein 1 (XBP1), which exists in the transcriptionally inactive unspliced form [XBP1(U)] and the spliced active form [XBP1(S)], is a key UPR component mediating antiestrogen resistance. We now show a direct link between the XBP1 and NF-κB survival pathways in driving the cell fate decisions in response to Antiestrogens in ER(+) breast cancer cells, both in vitro and in a xenograft mouse model. Using novel spliced and nonspliceable forms of XBP1, we show that XBP1(U) functions beyond being a dominant negative of XBP1(S). Both isoforms regulate NF-κB activity via ERα; XBP1(S) is more potent because it also directly regulates p65/RelA expression. These findings provide new insights into the fundamental signaling activities of spliced and unspliced XBP1 in breast cancer, establish NF-κB to be a mediator of these activities, and identify XBP1 and its splicing to be novel therapeutic targets.

  • abstract 679 glutamine metabolism in myc driven antiestrogen resistant breast cancer cells confers metabolic flexibility through the unfolded protein response
    Cancer Research, 2014
    Co-Authors: Ayesha N Shajahanhaq, Katherine L Cook, Jessica L Schwartzroberts, Anni Warri, Ahreej E Eltayeb, Diane M Demas, Leena Hilakiviclarke, Robert Clarke
    Abstract:

    Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Antiestrogens are used to treat estrogen receptor positive (ER+) breast tumors that constitute 70% of all breast cancer cases. Unfortunately, acquired resistance to antiestrogen therapy remains a critical clinical obstacle. Here we show that human breast cancer cells and rat mammary tumors that have acquired resistance to Antiestrogens express increased levels of MYC, a major regulator of both glutamine and glucose. Glutamine metabolism and glucose uptake were elevated in ER+ antiestrogen resistant cells (LCC9) compared with sensitive cells (LCC1). Inhibition of MYC, with siRNA or small molecule inhibitor, reduced cell viability and uptake of both glutamine and glucose in resistant cells. In resistant cells, MYC expression controlled protein levels of glutamine, glutamate and glucose transporters as well as GLUL and GLS, two enzymes that promote glutamate-glutamine inter-conversion. Increased MYC function in resistant cells correlated with increased cellular sensitivity to deprivation of, and also inhibitors of, both glutamine and glucose. While apoptosis eliminated all resistant cells in glucose-only conditions beyond 72 h, in glutamine-only conditions, the unfolded protein response (UPR) via GRP78-IRE1α and activating JNK and increased CHOP, induced apoptosis in majority of the cells but promoted survival in some. The antiestrogen faslodex (FAS; ICI 182,780) significantly reduced glucose uptake in antiestrogen resistant cells compared with sensitive cells. Thus, our findings reveal unique roles for MYC in promoting metabolic flexibility in and promoting survival in antiestrogen resistant breast cancer cells via the UPR. Targeting glutamine and glucose metabolism pathways, therefore, may provide novel strategies in treating endocrine resistant breast cancers. Citation Format: Ayesha N. Shajahan-Haq, Katherine L. Cook, Jessica L. Schwartz-Roberts, Ahreej E. Eltayeb, Diane M. Demas, Anni M. Warri, Leena A. Hilakivi-Clarke, Robert Clarke. Glutamine metabolism in MYC-driven antiestrogen resistant breast cancer cells confers metabolic flexibility through the unfolded protein response. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 679. doi:10.1158/1538-7445.AM2014-679

  • knockdown of estrogen receptor α induces autophagy and inhibits antiestrogen mediated unfolded protein response activation promoting ros induced breast cancer cell death
    The FASEB Journal, 2014
    Co-Authors: Katherine L Cook, Pamela A G Clarke, Jignesh H Parmar, Jessica L Schwartzroberts, Mones Abuasab, Anni Warri, William T Baumann, Robert Clarke
    Abstract:

    Approximately 70% of all newly diagnosed breast cancers express estrogen receptor (ER)-α. Although inhibiting ER action using targeted therapies such as fulvestrant (ICI) is often effective, later emergence of antiestrogen resistance limits clinical use. We used antiestrogen-sensitive and -resistant cells to determine the effect of Antiestrogens/ERα on regulating autophagy and unfolded protein response (UPR) signaling. Knockdown of ERα significantly increased the sensitivity of LCC1 cells (sensitive) and also resensitized LCC9 cells (resistant) to antiestrogen drugs. Interestingly, ERα knockdown, but not ICI, reduced nuclear factor (erythroid-derived 2)-like (NRF)-2 (UPR-induced antioxidant protein) and increased cytosolic kelch-like ECH-associated protein (KEAP)-1 (NRF2 inhibitor), consistent with the observed increase in ROS production. Furthermore, autophagy induction by Antiestrogens was prosurvival but did not prevent ERα knockdown–mediated death. We built a novel mathematical model to elucidate the ...

  • abstract 5397 myc driven glutamine metabolism promotes antiestrogen resistance in breast cancer
    Cancer Research, 2013
    Co-Authors: Ayesha N Shajahan, Katherine L Cook, Jessica L Schwartzroberts, Anni Warri, Ahreej E Eltayeb, Diane M Demas, Leena Hilakiviclarke, Steven J Metallo, Robert Clarke
    Abstract:

    About 70% of newly diagnosed cases of invasive breast cancer in the U.S. will be estrogen receptor alpha positive (ER+). Endocrine therapy is the least toxic and most effective means to manage the hormone-dependent breast cancer, administered as an antiestrogen, e.g., Tamoxifen (TAM) or Faslodex (FAS; Fulvestrant; ICI 182,780) or an aromatase inhibitor (AI), e.g., Letrozole (LET). However, advanced ER+ breast cancer that has become resistant to endocrine therapy remains a significant clinical problem. Here we show that in breast cancer cells and rat tumors with acquired antiestrogen resistance, MYC, a oncogenic transcription factor, is overexpressed. Inhibition of MYC with small molecule inhibitor or siRNA resensitizes resistant cells to antiestorgens by inducing apoptosis. MYC inhibition in resistant cells also inhibited glutamine uptake and decreased levels of ASCT2/SLC1A5, a glutamine transporter. Resistant cells showed significant increase in cell proliferation in response to glutamine than sensitive cells. Moreover, resistant cells showed increased sensitivity to an inhibitor of glutaminase, GLS, an enzyme that hydrolysis of glutamine to glutamate. Thus, MYC promotes increased dependence on glutamine in antiestrogen resistant cells, and targeting glutamine metabolism could help circumvent antiestrogen resistance. Overreaching goal of this study is to and to identify effective therapies to treat endocrine resistant breast cancer. Citation Format: Ayesha N. Shajahan, Katherine L. Cook, Jessica L. Schwartz-Roberts, Ahreej E. Eltayeb, Diane M. Demas, Anni Warri, Leena Hilakivi-Clarke, Steven Metallo, Robert Clarke. MYC-driven glutamine metabolism promotes antiestrogen resistance in breast cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5397. doi:10.1158/1538-7445.AM2013-5397

  • abstract 2266 beclin 1 regulation of autophagy in endocrine resistant breast cancer
    Cancer Research, 2012
    Co-Authors: Caroline O B Facey, Ayesha N Shajahan, Robert Clarke
    Abstract:

    Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Resistance to endocrine therapy occurs in nearly 50% of all patients diagnosed with estrogen receptor ≤ positive breast cancer, thus elucidating mechanism(s) of endocrine resistance is of major importance. To provide a model, we selected MCF7 variants that are estrogen independent and either sensitive (LCC1) or resistant (LCC9) to Antiestrogens: Faslodex (FAS; ICI 182, 780) and Tamoxifen (TAM). Antiestrogens induce endoplasmic reticulum stress which, depending on cell type, stimulus, and duration, may subsequently activate the unfolded protein response (UPR), autophagy, and/or apoptosis. Gene microarray analysis of LCC9 cells show high expression levels of X-box binding protein 1 (XBP1), implicating the unfolded protein response (UPR) as a pro-survival mechanism of resistance. In addition to an elevated UPR, autophagy is substantially elevated in response to Antiestrogens. To better understand the role of autophagy in antiestrogen responsiveness, we investigated the consequence of knocking down BECLIN-1 in LCC1 and LCC9 cells treated with FAS and TAM. Preliminary results indicate a time-dependent change in autophagy following knock-down of beclin-1 in response to short-term (48h) and long-term (6 day) treatment. At 48h, sensitive LCC1 cells respond to Antiestrogens with high levels of autophagy measured by increased LC3BII to LC3BI ratio and decreased expression of p62. Relative cell density (measured by crystal violet assay) decreases by 20% at 48h and by 80% at 6 days in LCC1 cells however, LCC9 cells are minimally affected by antiestrogen treatment. The level of autophagy remains high at 6 days in sensitive cells however levels remain constant in resistant cells. Autophagy is significantly lowered by reduced BECN1 in both sensitive and resistant cells however there is an increase in cell density in sensitive cells transfected with BECN1- shRNA at 6 days, indicating an autophagy associated programmed cell death mechanism in response to antiestrogen treatment. Protein expression of an active form of caspase −12/4 (an initiator caspase activated during endoplasmic reticulum stress) is elevated in sensitive cells at 6 days in response to antiestrogen treatment, also indicating the onset of apoptosis at this time. Elevated expression of Bcl-2 family members in resistant cells may play a more substantial role than BECN1 alone, as the combination of Bcl-2 family protein inhibitors and BECN1-shRNA sensitizes resistant cells to a greater extent. Thus, Bcl-2 family members in resistant cells may play a critical role in managing the balance between cell survival (moderate autophagy) and programmed cell death (excessive autophagy and apoptosis) in response to antiestrogen treatment. 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 2266. doi:1538-7445.AM2012-2266

Claude Labrie - One of the best experts on this subject based on the ideXlab platform.

  • comparison of the effects of em 652 sch57068 tamoxifen toremifene droloxifene idoxifene gw 5638 and raloxifene on the growth of human zr 75 1 breast tumors in nude mice
    International Journal of Cancer, 2002
    Co-Authors: Matthieu Gutman, Steeve Couillard, Jenny Roy, Fernand Labrie, Bernard Candas, Claude Labrie
    Abstract:

    EM-652 exerts pure antiestrogenic activity in the mammary gland and endometrium, while tamoxifen, the antiestrogen most widely used for the treatment of breast cancer, exerts mixed antiestrogenic-estrogenic activity in these tissues. Our objective was to compare the agonistic and antagonistic effects of EM-652 with tamoxifen and 5 other Antiestrogens on the growth of ZR-75-1 human breast xenografts in ovariectomized nude mice. During the 23 weeks of treatment at a daily oral dose of 50 microg, EM-652 was the only compound that decreased tumor size relative to pretreatment values, whereas the 6 other Antiestrogens only decreased to various extents the progression rate stimulated by estrone. Under estrone stimulation, all groups of animals had more than 60% of their tumors in the progression category except for the EM-652-treated group, where only 7% of the tumors progressed. In the absence of estrone stimulation, progression was seen in 60%, 33%, 21% and 12% of tumors in the tamoxifen-, idoxifene-, toremifene- and raloxifene-treated groups, respectively, while only 4% of tumors progressed in the EM-652-treated group. The agonistic and antagonistic actions of each antiestrogen were also measured on endometrial epithelial cell thickness. Our present findings indicate that EM-652, in addition to being the most potent antiestrogen on human breast tumor growth, has no agonistic effect in breast and endometrial tissues. Since previous data have shown benefits of EM-652 on bone density and lipid profile, this compound could be an ideal candidate for chemoprevention of breast and uterine cancers, while protecting against osteoporosis and cardiovascular disease.

  • comparison of the effects of em 652 sch57068 tamoxifen toremifene droloxifene idoxifene gw 5638 and raloxifene on the growth of human zr 75 1 breast tumors in nude mice
    International Journal of Cancer, 2002
    Co-Authors: Matthieu Gutman, Steeve Couillard, Fernand Labrie, Bernard Candas, Claude Labrie
    Abstract:

    EM-652 exerts pure antiestrogenic activity in the mammary gland and endometrium, while tamoxifen, the antiestrogen most widely used for the treatment of breast cancer, exerts mixed antiestrogenic–estrogenic activity in these tissues. Our objective was to compare the agonistic and antagonistic effects of EM-652 with tamoxifen and 5 other Antiestrogens on the growth of ZR-75-1 human breast xenografts in ovariectomized nude mice. During the 23 weeks of treatment at a daily oral dose of 50 μg, EM-652 was the only compound that decreased tumor size relative to pretreatment values, whereas the 6 other Antiestrogens only decreased to various extents the progression rate stimulated by estrone. Under estrone stimulation, all groups of animals had more than 60% of their tumors in the progression category except for the EM-652–treated group, where only 7% of the tumors progressed. In the absence of estrone stimulation, progression was seen in 60%, 33%, 21% and 12% of tumors in the tamoxifen-, idoxifene-, toremifene- and raloxifene-treated groups, respectively, while only 4% of tumors progressed in the EM-652–treated group. The agonistic and antagonistic actions of each antiestrogen were also measured on endometrial epithelial cell thickness. Our present findings indicate that EM-652, in addition to being the most potent antiestrogen on human breast tumor growth, has no agonistic effect in breast and endometrial tissues. Since previous data have shown benefits of EM-652 on bone density and lipid profile, this compound could be an ideal candidate for chemoprevention of breast and uterine cancers, while protecting against osteoporosis and cardiovascular disease. © 2002 Wiley-Liss, Inc.

  • synthesis and biological activity of new halo steroidal Antiestrogens
    Journal of Medicinal Chemistry, 1991
    Co-Authors: Charles Levesque, Claude Labrie, Yves Merand, Jean Marc Dufour, Fernand Labrie
    Abstract:

    Antiestrogen therapy is the most widely used endocrine manipulation for the treatment of breast cancer, especially in postmenopausal women. Unfortunately, the compounds presently available possess mixed agonistic/antagonistic activity, thus potentially limiting their therapeutic efficacy. Following the observations that an aliphatic chain at the 7 alpha-position of 17 beta-estradiol does not prevent binding to the estrogen receptor while halogenation of estradiol can increase the affinity of its binding (expressed as RBA) to the estrogen receptor, we have synthesized a series of new steroidal Antiestrogens (6-10) which possess both an 7 alpha-undecanamide group and an halogen atom (Cl, Br, or I) at the 16 alpha-position. The stereochemistry of these compounds was unambiguously established by high-field (400-MHz) nuclear magnetic resonance. Some of the compounds obtained possess potent in vivo antiestrogenic activity. At the low twice daily 3-micrograms dose, 16 alpha-chloro 3,17 beta-diol amide, 16 alpha-iodo 3,17 beta-diol amide, 16 alpha-bromo 3,17 beta-diol amide, 16 alpha-chloro 3,17 alpha-diol amide, and 16 alpha-bromo 3,17 alpha-diol amide inhibit by 74, 63, 52, 35, and 60%, respectively, the estradiol-induced stimulation of uterine weight in ovariectomized Balb/c mice while 78-99% blockade of estradiol action is achieved at the 20-micrograms dose. These new Antiestrogens show no estrogenic activity on uterine weight at the doses used while tamoxifen (2-[4-(1,2-diphenyl-1-butenyl)phenoxy]-N,N- dimethylethanamine) shows full estrogenic activity and is only a weak partial antiestrogen in the same assay.

Fernand Labrie - One of the best experts on this subject based on the ideXlab platform.

  • effect of Antiestrogens and aromatase inhibitor on basal growth of the human breast cancer cell line mcf 7 in serum free medium
    The Journal of Steroid Biochemistry and Molecular Biology, 2003
    Co-Authors: Janne Jensen, Fernand Labrie, Jason W Kitlen, Per Briand, Anne E. Lykkesfeldt
    Abstract:

    Antiestrogens are efficient inhibitors of estrogen-mediated growth of human breast cancer. Besides inhibiting estradiol-stimulated growth, Antiestrogens may have a direct growth-inhibitory effect on estrogen receptor (ER) positive cells and thus be more efficient than aromatase inhibitors, which will only abrogate estrogen-dependent tumor growth. To address this issue, we have used the human breast cancer cell line MCF-7/S9 as a model system which is maintained in a chemically defined medium without serum and estrogen. The addition of estradiol results in an increase in cell growth rate. Thus, the MCF-7/S9 cell line is estrogen-responsive but not estrogen-dependent. Three different types of Antiestrogens, namely tamoxifen, ICI 182,780 and EM-652 were found to exert a significant and dose-dependent inhibition of basal growth of MCF-7/S9 cells. The growth-inhibitory effect of the three Antiestrogens was prevented by simultaneous estradiol treatment. Antiestrogen treatment also reduced the basal pS2 mRNA expression level, thus indicating spontaneous estrogenic activity in the cells. However, treatment with the aromatase inhibitor had no effect on basal cell growth, excluding that endogenous estrogen synthesis is involved in basal growth. These data demonstrate that in addition to their estrogen antagonistic effect, Antiestrogens have a direct growth-inhibitory effect which is ER-mediated. Consequently, in the subset of ER positive breast cancer patients with estrogen-independent tumor growth, antiestrogen therapy may be superior to treatment with aromatase inhibitors which only inhibit estrogen formation but do not affect cancer cell growth in the absence of estrogens.

  • comparison of the effects of em 652 sch57068 tamoxifen toremifene droloxifene idoxifene gw 5638 and raloxifene on the growth of human zr 75 1 breast tumors in nude mice
    International Journal of Cancer, 2002
    Co-Authors: Matthieu Gutman, Steeve Couillard, Jenny Roy, Fernand Labrie, Bernard Candas, Claude Labrie
    Abstract:

    EM-652 exerts pure antiestrogenic activity in the mammary gland and endometrium, while tamoxifen, the antiestrogen most widely used for the treatment of breast cancer, exerts mixed antiestrogenic-estrogenic activity in these tissues. Our objective was to compare the agonistic and antagonistic effects of EM-652 with tamoxifen and 5 other Antiestrogens on the growth of ZR-75-1 human breast xenografts in ovariectomized nude mice. During the 23 weeks of treatment at a daily oral dose of 50 microg, EM-652 was the only compound that decreased tumor size relative to pretreatment values, whereas the 6 other Antiestrogens only decreased to various extents the progression rate stimulated by estrone. Under estrone stimulation, all groups of animals had more than 60% of their tumors in the progression category except for the EM-652-treated group, where only 7% of the tumors progressed. In the absence of estrone stimulation, progression was seen in 60%, 33%, 21% and 12% of tumors in the tamoxifen-, idoxifene-, toremifene- and raloxifene-treated groups, respectively, while only 4% of tumors progressed in the EM-652-treated group. The agonistic and antagonistic actions of each antiestrogen were also measured on endometrial epithelial cell thickness. Our present findings indicate that EM-652, in addition to being the most potent antiestrogen on human breast tumor growth, has no agonistic effect in breast and endometrial tissues. Since previous data have shown benefits of EM-652 on bone density and lipid profile, this compound could be an ideal candidate for chemoprevention of breast and uterine cancers, while protecting against osteoporosis and cardiovascular disease.

  • comparison of the effects of em 652 sch57068 tamoxifen toremifene droloxifene idoxifene gw 5638 and raloxifene on the growth of human zr 75 1 breast tumors in nude mice
    International Journal of Cancer, 2002
    Co-Authors: Matthieu Gutman, Steeve Couillard, Fernand Labrie, Bernard Candas, Claude Labrie
    Abstract:

    EM-652 exerts pure antiestrogenic activity in the mammary gland and endometrium, while tamoxifen, the antiestrogen most widely used for the treatment of breast cancer, exerts mixed antiestrogenic–estrogenic activity in these tissues. Our objective was to compare the agonistic and antagonistic effects of EM-652 with tamoxifen and 5 other Antiestrogens on the growth of ZR-75-1 human breast xenografts in ovariectomized nude mice. During the 23 weeks of treatment at a daily oral dose of 50 μg, EM-652 was the only compound that decreased tumor size relative to pretreatment values, whereas the 6 other Antiestrogens only decreased to various extents the progression rate stimulated by estrone. Under estrone stimulation, all groups of animals had more than 60% of their tumors in the progression category except for the EM-652–treated group, where only 7% of the tumors progressed. In the absence of estrone stimulation, progression was seen in 60%, 33%, 21% and 12% of tumors in the tamoxifen-, idoxifene-, toremifene- and raloxifene-treated groups, respectively, while only 4% of tumors progressed in the EM-652–treated group. The agonistic and antagonistic actions of each antiestrogen were also measured on endometrial epithelial cell thickness. Our present findings indicate that EM-652, in addition to being the most potent antiestrogen on human breast tumor growth, has no agonistic effect in breast and endometrial tissues. Since previous data have shown benefits of EM-652 on bone density and lipid profile, this compound could be an ideal candidate for chemoprevention of breast and uterine cancers, while protecting against osteoporosis and cardiovascular disease. © 2002 Wiley-Liss, Inc.

  • ligand independent activation of the estrogen receptors alpha and beta by mutations of a conserved tyrosine can be abolished by Antiestrogens
    Cancer Research, 1998
    Co-Authors: Gilles Bernard Tremblay, Fernand Labrie, Andre Tremblay, Vincent Giguere
    Abstract:

    It has recently been suggested that mutation of a conserved tyrosine to asparagine within the ligand-binding domain of the estrogen receptor (ER) alpha confers hormone-independent activation and insensitivity to Antiestrogens (Q. X. Zhang et al., Cancer Res., 57: 1244-1249, 1997). In view of the recent discovery of ERbeta and the development of the novel nonsteroidal antiestrogen EM-800 and its active metabolite EM-652, we decided to reexamine this issue by introducing a series of mutations at the conserved tyrosine 537 in ERalpha and 443 in ERbeta and measuring their transcriptional activity in the absence and presence of estradiol and the Antiestrogens EM-652, ICI 182,780, and 4-hydroxytamoxifen. As demonstrated previously for ERalpha, we observed that substituting a serine or asparagine but not a phenylalanine for the conserved tyrosine 443 in ERbeta confers constitutive transcriptional activity to the receptor. This activity was apparent on both the vitA2-ERE and the pS2 promoters in Cos-1 and HeLa cell lines as well as the human breast cancer cell line MDA-MB-231. However, the ligand-independent transcriptional activity of all ERalpha and ERbeta mutants examined, including the tyrosine to asparagine substitutions, was completely abolished by the three Antiestrogens tested in this system. Furthermore, hormone-independent interaction of ERalpha and ERbeta mutant receptors with the steroid receptor coactivator-1 was abrogated by these Antiestrogens. Our report, therefore, indicates that Antiestrogens would be effective agents against constitutively active tyrosine ERalpha and ERbeta mutants and suggests that this particular type of modified receptors are unlikely to contribute to resistance toward Antiestrogens in breast cancer therapy.

  • synthesis and biological activity of new halo steroidal Antiestrogens
    Journal of Medicinal Chemistry, 1991
    Co-Authors: Charles Levesque, Claude Labrie, Yves Merand, Jean Marc Dufour, Fernand Labrie
    Abstract:

    Antiestrogen therapy is the most widely used endocrine manipulation for the treatment of breast cancer, especially in postmenopausal women. Unfortunately, the compounds presently available possess mixed agonistic/antagonistic activity, thus potentially limiting their therapeutic efficacy. Following the observations that an aliphatic chain at the 7 alpha-position of 17 beta-estradiol does not prevent binding to the estrogen receptor while halogenation of estradiol can increase the affinity of its binding (expressed as RBA) to the estrogen receptor, we have synthesized a series of new steroidal Antiestrogens (6-10) which possess both an 7 alpha-undecanamide group and an halogen atom (Cl, Br, or I) at the 16 alpha-position. The stereochemistry of these compounds was unambiguously established by high-field (400-MHz) nuclear magnetic resonance. Some of the compounds obtained possess potent in vivo antiestrogenic activity. At the low twice daily 3-micrograms dose, 16 alpha-chloro 3,17 beta-diol amide, 16 alpha-iodo 3,17 beta-diol amide, 16 alpha-bromo 3,17 beta-diol amide, 16 alpha-chloro 3,17 alpha-diol amide, and 16 alpha-bromo 3,17 alpha-diol amide inhibit by 74, 63, 52, 35, and 60%, respectively, the estradiol-induced stimulation of uterine weight in ovariectomized Balb/c mice while 78-99% blockade of estradiol action is achieved at the 20-micrograms dose. These new Antiestrogens show no estrogenic activity on uterine weight at the doses used while tamoxifen (2-[4-(1,2-diphenyl-1-butenyl)phenoxy]-N,N- dimethylethanamine) shows full estrogenic activity and is only a weak partial antiestrogen in the same assay.

Benita S. Katzenellenbogen - One of the best experts on this subject based on the ideXlab platform.

  • estrogen receptor alpha somatic mutations y537s and d538g confer breast cancer endocrine resistance by stabilizing the activating function 2 binding conformation
    eLife, 2016
    Co-Authors: Sean W Fanning, Christopher G Mayne, Venkatasubramanian Dharmarajan, Kathryn E Carlson, Teresa A Martin, Scott J Novick, Weiyi Toy, B D Green, Srinivas Panchamukhi, Benita S. Katzenellenbogen
    Abstract:

    Around one in every eight women will be diagnosed with breast cancer in their lifetime. Hormone-based therapies – also referred to antiestrogen drugs – target a protein called estrogen receptor alpha and are effective treatments for the majority of these cancers. Unfortunately, about half of patients will develop recurrent breast cancers even though the cancer continues to produce the target of the drugs. The estrogen receptor alpha drives breast cancer in a number of ways, many of which require the receptor to be activated by binding to the hormone estrogen. When estrogen binds it causes the receptor to change shape to expose a surface where other proteins called coactivators can bind. Once a coactivator is bound, the estrogen receptor is active and signals the cancer cell to grow, divide, invade local tissues, and spread to new sites in the body. Antiestrogen drugs competitively block the binding of estrogen to the receptor and cause the receptor to take on a different shape that inhibits the binding of the coactivator. However, recent studies identified mutations at specific sites in the gene that encodes estrogen receptor alpha in a large subset of patients with breast cancers that have spread. These mutations make the receptor resistant to antiestrogen drugs, and two mutations (called Y537S and D538G) account for approximately 70% of cases. However, it was not clear how these mutations altered the activity of estrogen receptor alpha at the molecular level. Fanning, Mayne, Dharmarajan et al. now show these two most common mutations allow estrogen receptor alpha to bind to the coactivator in the absence of hormone. This unfortunately also reduces the effectiveness of one of the mostly widely administered antiestrogen therapies – a drug called tamoxifen. However, Fanning, Mayne, Dharmarajan et al. also show that the newer and more potent Antiestrogens that are currently under examination in clinical trials should be highly effective at treating the cancers with the mutated versions of estrogen receptor alpha. Applying the knowledge gained from these new findings toward the development of new Antiestrogens could help reverse the impact of these common mutations. If successful, these new drugs will provide life-saving treatments for many breast cancer patients.

  • the estrogen receptor enhances ap 1 activity by two distinct mechanisms with different requirements for receptor transactivation functions
    Molecular Endocrinology, 1999
    Co-Authors: Paul Webb, Benita S. Katzenellenbogen, Eileen M. Mcinerney, Phuong H Nguyen, Cathleen D Valentine, Gabriela N Lopez, Grace R Kwok, Eva Enmark, Stefan Nilsson
    Abstract:

    Estrogen receptors (ERs α and β) enhance transcription in response to estrogens by binding to estrogen response elements (EREs) within target genes and utilizing transactivation functions (AF-1 and AF-2) to recruit p160 coactivator proteins. The ERs also enhance transcription in response to estrogens and Antiestrogens by modulating the activity of the AP-1 protein complex. Here, we examine the role of AF-1 and AF-2 in ER action at AP-1 sites. Estrogen responses at AP-1 sites require the integrity of the ERα AF-1 and AF-2 activation surfaces and the complementary surfaces on the p160 coactivator GRIP1 (glucocorticoid receptor interacting protein 1), the NID/AF-1 region, and NR boxes. Thus, estrogen-liganded ERα utilizes the same protein-protein contacts to transactivate at EREs and AP-1 sites. In contrast, antiestrogen responses are strongly inhibited by ERα AF-1 and weakly inhibited by AF-2. Indeed, ERα truncations that lack AF-1 enhance AP-1 activity in the presence of Antiestrogens, but not estrogens. T...

  • the estrogen receptor enhances ap 1 activity by two distinct mechanisms with different requirements for receptor transactivation functions
    Molecular Endocrinology, 1999
    Co-Authors: Paul Webb, Benita S. Katzenellenbogen, Eileen M. Mcinerney, Cathleen D Valentine, Gabriela N Lopez, Grace R Kwok, Eva Enmark, Phuong Nguyen, Janake Gustafsson, Stefan Nilsson
    Abstract:

    Estrogen receptors (ERs alpha and beta) enhance transcription in response to estrogens by binding to estrogen response elements (EREs) within target genes and utilizing transactivation functions (AF-1 and AF-2) to recruit p160 coactivator proteins. The ERs also enhance transcription in response to estrogens and Antiestrogens by modulating the activity of the AP-1 protein complex. Here, we examine the role of AF-1 and AF-2 in ER action at AP-1 sites. Estrogen responses at AP-1 sites require the integrity of the ERalpha AF-1 and AF-2 activation surfaces and the complementary surfaces on the p160 coactivator GRIP1 (glucocorticoid receptor interacting protein 1), the NID/AF-1 region, and NR boxes. Thus, estrogen-liganded ERalpha utilizes the same protein-protein contacts to transactivate at EREs and AP-1 sites. In contrast, antiestrogen responses are strongly inhibited by ERalpha AF-1 and weakly inhibited by AF-2. Indeed, ERalpha truncations that lack AF-1 enhance AP-1 activity in the presence of Antiestrogens, but not estrogens. This phenotype resembles ERbeta, which naturally lacks constitutive AF-1 activity. We conclude that the ERs enhance AP-1 responsive transcription by distinct mechanisms with different requirements for ER transactivation functions. We suggest that estrogen-liganded ER enhances AP-1 activity via interactions with p160s and speculate that antiestrogen-liganded ER enhances AP-1 activity via interactions with corepressors.

  • an estrogen receptor selective coregulator that potentiates the effectiveness of Antiestrogens and represses the activity of estrogens
    Proceedings of the National Academy of Sciences of the United States of America, 1999
    Co-Authors: Monica M. Montano, Kirk Ekena, Regis Delagemourroux, Weiru Chang, Paolo G V Martini, Benita S. Katzenellenbogen
    Abstract:

    The action of nuclear hormone receptors is tripartite, involving the receptor, its ligands, and its coregulator proteins. The estrogen receptor (ER), a member of this superfamily, is a hormone-activated transcription factor that mediates the stimulatory effects of estrogens and the inhibitory effects of Antiestrogens such as tamoxifen in breast cancer and other estrogen target cells. To understand how Antiestrogens and dominant negative ERs suppress ER activity, we used a dominant negative ER as bait in two-hybrid screening assays from which we isolated a clone from breast cancer cells that potentiates the inhibitory activities of dominant negative ERs and antiestrogen-liganded ER. At higher concentrations, it also represses the transcriptional activity of the estradiol-liganded ER, while having no effect on other nuclear hormone receptors. This clone, denoted REA for “repressor of estrogen receptor activity,” encodes a 37-kDa protein that is an ER-selective coregulator. Its competitive reversal of steroid receptor coactivator 1 enhancement of ER activity and its direct interaction with liganded ER suggest that it may play an important role in determining the sensitivity of estrogen target cells, including breast cancer cells, to Antiestrogens and estrogens.

  • transcriptional regulation of the human quinone reductase gene by antiestrogen liganded estrogen receptor α and estrogen receptor β
    Journal of Biological Chemistry, 1998
    Co-Authors: Monica M. Montano, Anil K Jaiswal, Benita S. Katzenellenbogen
    Abstract:

    Abstract We have previously reported that Antiestrogens stimulate quinone reductase (NAD(P)H:(quinone-acceptor) oxidoreductase (QR or NQO1); EC 1.6.99.2) enzymatic activity, an action that may provide protective effects against the toxicity and mutagenicity caused by quinones. We have now investigated the transcriptional regulation of the QR gene by Antiestrogens. In transfection experiments employing the 5′-flanking (863-base pair) region of the human QR gene promoter with its electrophile/antioxidant response element (EpRE/ARE) or deleted or mutated constructs, we observe that Antiestrogens induced an increase in QR gene promoter reporter activity in estrogen receptor (ER) negative breast cancer and endometrial cancer cells transfected with ER, and this induction by Antiestrogens was repressed by estradiol. The stimulation of QR transcriptional activity required the 31-base pair electrophile-responsive region from the human QR gene promoter and a functional ER. Intriguingly, Antiestrogens were stronger activators of the QR EpRE via the ER subtype ERβ than ERα. Oligonucleotide gel mobility and antibody shift assays reveal that the ER binds to the EpRE but is only a minor component of the proteins bound to the EpRE in ER-containing MCF-7 breast cancer cells. While binding of ERβ to the estrogen response element was weaker when compared with ERα, ERβ and ERα showed similar binding to the EpRE. Together these findings provide evidence that QR gene regulation by the antiestrogen-occupied ER is mediated by the EpRE-containing region of the human QR gene and indicate that the ER is one of the complex of proteins that binds to the EpRE. In addition, that ERβ is a more potent activator at EpRE elements than is ERα suggests that the different levels of these two receptors in various estrogen target cells could impact importantly on the antioxidant potency of Antiestrogens in different target cells. These findings have broad implications regarding the potential beneficial effects of Antiestrogens since EpREs mediate the transcriptional induction of numerous genes, including QR, which encode chemoprotective detoxification enzymes.

Anne E. Lykkesfeldt - One of the best experts on this subject based on the ideXlab platform.

  • 1Breast Cancer Group, Unit of Cell Death and Metabolism, Danish Cancer
    2016
    Co-Authors: Cousarah L Larsen, Anne E. Lykkesfeldt, Christina W Yde, Anne-vibeke Laenkholm, Birgitte B Rasmussen, Anne Katrine Duun-henriksen, Martin Bak, Tove Kirkegaard
    Abstract:

    Aurora kinase B is important for antiestrogen resistant cell growth and a potential biomarker for tamoxifen resistant breast cancer with acquired resistance to Antiestrogens

  • HIF2α contributes to antiestrogen resistance via positive bilateral crosstalk with EGFR in breast cancer cells.
    Oncotarget, 2016
    Co-Authors: Muhammad Wasi Alam, Camilla Persson, Susann Reinbothe, Julhash U. Kazi, Lars Rönnstrand, Caroline Wigerup, Henrik J. Ditzel, Anne E. Lykkesfeldt, Sven Påhlman, Annika Jögi
    Abstract:

    The majority of breast cancers express estrogen receptor α (ERα), and most patients with ERα-positive breast cancer benefit from antiestrogen therapy. The ERα-modulator tamoxifen and ERα-downregulator fulvestrant are commonly employed Antiestrogens. Antiestrogen resistance remains a clinical challenge, with few effective treatments available for patients with antiestrogen-resistant breast cancer. Hypoxia, which is intrinsic to most tumors, promotes aggressive disease, with the hypoxia-inducible transcription factors HIF1 and HIF2 regulating cellular responses to hypoxia. Here, we show that the ERα-expressing breast cancer cells MCF-7, CAMA-1, and T47D are less sensitive to Antiestrogens when hypoxic. Furthermore, protein and mRNA levels of HIF2α/HIF2A were increased in a panel of antiestrogen-resistant cells, and antiestrogen-exposure further increased HIF2α expression. Ectopic expression of HIF2α in MCF-7 cells significantly decreased sensitivity to Antiestrogens, further implicating HIF2α in antiestrogen resistance. EGFR is known to contribute to antiestrogen resistance: we further show that HIF2α drives hypoxic induction of EGFR and that EGFR induces HIF2α expression. Downregulation or inhibition of EGFR led to decreased HIF2α levels. This positive and bilateral HIF2-EGFR regulatory crosstalk promotes antiestrogen resistance and, where intrinsic hypoxic resistance exists, therapy itself may exacerbate the problem. Finally, inhibition of HIFs by FM19G11 restores antiestrogen sensitivity in resistant cells. Targeting HIF2 may be useful for counteracting antiestrogen resistance in the clinic.

  • antiestrogen resistant human breast cancer cells require activated protein kinase b akt for growth
    Endocrine-related Cancer, 2005
    Co-Authors: T Frogne, J S Jepsen, S S Larsen, C K Fog, B L Brockdorff, Anne E. Lykkesfeldt
    Abstract:

    Development of acquired resistance to Antiestrogens is a major clinical problem in endocrine treatment of breast cancer patients. The IGF system plays a profound role in many cancer types, including breast cancer. Thus, overexpression and/or constitutive activation of the IGF-I receptor (IGF-IR) or different components of the IGF-IR signaling pathway have been reported to render breast cancer cells less estrogen dependent and capable of sustaining cell proliferation in the presence of Antiestrogens. In this study, growth of the antiestrogen-sensitive human breast cancer cell line MCF-7 was inhibited by treatment with IGF-IR-neutralizing antibodies. In contrast, IGFIR-neutralizing antibodies had no effect on growth of two different antiestrogen-resistant MCF-7 sublines. A panel of antiestrogen-resistant cell lines was investigated for expression of IGF-IR and either undetectable or severely reduced IGF-IR levels were observed. No increase in insulin receptor substrate 1 (IRS-1) or total PKB/Akt (Akt) was detected in the resistant cell lines. However, a significant increase in phosphorylated Akt (pAkt) was found in four of six antiestrogen-resistant cell lines. Overexpression of pAkt was associated with increased Akt kinase activity in both a tamoxifenand an ICI 182,780-resistant cell line. Inhibition of Akt phosphorylation by the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin or the Akt inhibitor SH-6 (structurally modified phosphatidyl inositol ether liquid analog PIA 6) resulted in a more pronounced growth inhibitory effect on the antiestrogen-resistant cells compared with the parental cells, suggesting that signaling via Akt is required for antiestrogen-resistant cell growth in at least a subset of our antiestrogen-resistant cell lines. PTEN expression and activity was not decreased in cell lines overexpressing pAkt. Our data demonstrate that Akt is a target for treatment of antiestrogen-resistant breast cancer cell lines and we suggest that antiestrogen-resistant breast cancer patients may benefit from treatment targeted to inhibit Akt signaling.

  • validation of real time rt pcr for analysis of human breast cancer cell lines resistant or sensitive to treatment with Antiestrogens
    Endocrine-related Cancer, 2003
    Co-Authors: P De Cremoux, B L Brockdorff, Nils Brunner, Carine Tranperennou, E Boudou, H Magdelenat, Anne E. Lykkesfeldt
    Abstract:

    Using a quantitative real-time RT-PCR technique we have compared the expression of a number of genes in two different human breast cancer model systems for development of acquired resistance to Antiestrogens. The model system developed at the Danish Cancer Society comprises the cell lines MCF-7, MCF-7/TAMR-1, MCF-7/182R-6 and MCF-7/182R-7, and the model system developed at the Lombardi Cancer Research Center consists of the cell lines MCF-7/LCC1, MCF-7/LCC2 and MCF-7/LCC9. The findings on the well-known parameters estrogen receptor (ER)alpha, progesterone receptor (PR) and epidermal growth factor receptor (EGFR) are in good agreement with previous reports, thus documenting the usefulness of the real-time RT-PCR technique for multiparametric RNA analysis. The gene expression levels in the two model systems were found to be quite similar in relation to ERalpha, AIB1 (amplified in breast cancer-1), breast cancer antiestrogen resistance gene 1 (BCAR1) and ErbB-2 mRNA expression, whereas significant differences were observed on the expression of ERbeta, multidrug resistance gene 1 (MDR1), PR and EGFR. Furthermore, the presented data suggest that ERbeta, AIB1, BCAR1, CYP19 and MDR1 are unlikely to be causally involved in development of antiestrogen resistance in these breast cancer cell lines.

  • effect of Antiestrogens and aromatase inhibitor on basal growth of the human breast cancer cell line mcf 7 in serum free medium
    The Journal of Steroid Biochemistry and Molecular Biology, 2003
    Co-Authors: Janne Jensen, Fernand Labrie, Jason W Kitlen, Per Briand, Anne E. Lykkesfeldt
    Abstract:

    Antiestrogens are efficient inhibitors of estrogen-mediated growth of human breast cancer. Besides inhibiting estradiol-stimulated growth, Antiestrogens may have a direct growth-inhibitory effect on estrogen receptor (ER) positive cells and thus be more efficient than aromatase inhibitors, which will only abrogate estrogen-dependent tumor growth. To address this issue, we have used the human breast cancer cell line MCF-7/S9 as a model system which is maintained in a chemically defined medium without serum and estrogen. The addition of estradiol results in an increase in cell growth rate. Thus, the MCF-7/S9 cell line is estrogen-responsive but not estrogen-dependent. Three different types of Antiestrogens, namely tamoxifen, ICI 182,780 and EM-652 were found to exert a significant and dose-dependent inhibition of basal growth of MCF-7/S9 cells. The growth-inhibitory effect of the three Antiestrogens was prevented by simultaneous estradiol treatment. Antiestrogen treatment also reduced the basal pS2 mRNA expression level, thus indicating spontaneous estrogenic activity in the cells. However, treatment with the aromatase inhibitor had no effect on basal cell growth, excluding that endogenous estrogen synthesis is involved in basal growth. These data demonstrate that in addition to their estrogen antagonistic effect, Antiestrogens have a direct growth-inhibitory effect which is ER-mediated. Consequently, in the subset of ER positive breast cancer patients with estrogen-independent tumor growth, antiestrogen therapy may be superior to treatment with aromatase inhibitors which only inhibit estrogen formation but do not affect cancer cell growth in the absence of estrogens.