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  • 1
    In: Journal of Clinical Oncology, American Society of Clinical Oncology (ASCO), Vol. 37, No. 15_suppl ( 2019-05-20), p. 1059-1059
    Abstract: 1059 Background: H3B-6545 inactivates both wild-type and mutant ERα by targeting cysteine 530 and enforcing a unique antagonist conformation. Methods: Women with locally advanced or metastatic HR+ BC are treated (tx) with H3B-6545 administered once daily orally over a 28 day cycle after progression on at least one hormonal therapy and at least one additional therapy/regimen. Dose escalation uses a 3+3 design with the option to backfill previously cleared doses and allows for intrapatient dose escalation. This phase 1 explores the safety, pharmacokinetics and pharmacodynamics of H3B-6545 in women with HR+ BC to identify the recommended Phase 2 dose. Results: As of 10-Dec-2018, 32 pts have been tx with H3B-6545 at doses of 100 to 450 mg/day; 97% had prior tx with a CDK4/6 inhibitor and 56% had received ≥3 lines of prior anti-cancer therapy. No dose-limiting toxicities and only one Grade 3 treatment related adverse event (TRAE) have been observed (lymphocyte count decrease). The most common (≥10%) TRAEs include asymptomatic sinus bradycardia, diarrhea, nausea, fatigue, anemia, decreased appetite, and hot flush. H3B-6545 was rapidly absorbed with a t max of 2-4 h. Plasma concentration increased with dose from 100 to 450 mg, and was similar on C1D1 and C1D15. Consistent with the H3B-6545 mechanism of action and preclinical data, H3B-6545 inhibits ER target gene expression and shows a 50% decrease in Ki67 levels across all dose levels post-tx. ESR1 (60%) and PIK3CA (34%) mutations were detected in plasma at baseline and changes in mutant allele frequencies show correlation in response to tx. Stable disease was observed in 15 pts (47%) and 34% of pts completed at least 6 months of tx. Partial responses (PRs) were observed in 3 pts: 1 pt (mutant) received 2 prior lines of therapy and 2 pts (1 mutant and 1 wild-type) received 〉 5 prior lines of therapy including fulvestrant and capecitabine; all 3 pts received a prior CDK4/6 inhibitor. Conclusions: H3B-6545 has been well-tolerated up to the 450 mg dose level with early signs of single-agent anti-tumor activity in a post CDK4/6 setting. Dose escalation continues in pts with advanced HR+ BC. Clinical trial information: NCT03250676.
    Type of Medium: Online Resource
    ISSN: 0732-183X , 1527-7755
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    Language: English
    Publisher: American Society of Clinical Oncology (ASCO)
    Publication Date: 2019
    detail.hit.zdb_id: 2005181-5
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  • 2
    In: Nature Medicine, Springer Science and Business Media LLC, Vol. 17, No. 9 ( 2011-9), p. 1101-1108
    Type of Medium: Online Resource
    ISSN: 1078-8956 , 1546-170X
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2011
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  • 3
    In: Blood, American Society of Hematology, Vol. 106, No. 11 ( 2005-11-16), p. 732-732
    Abstract: To produce blood platelets, the megakaryocyte (MK) cytoplasm elaborates proplatelets, accompanied by expansion of membrane surface area and dramatic cytoskeletal rearrangements. Invaginated demarcation membranes (DMS) are thought to be the source for the proplatelet and platelet membranes, however, they have THUS far BEEN INSUFFICIENTLY characterized. We first used a mouse model where the cDNA encoding enhanced yellow fluorescence protein (EYFP) with a C-terminally introduced myristoyl acceptor site has been introduced into the GPIIb locus. Heterozygous knock-in mice reveal yellow fluroescent MKs with an internal staining pattern that resembles the reticiulated pattern of the DMS as found in micrographs. Proplatelet-forming MKs reveal contiguous membrane connection between the internally stained membranes and the outlines of the proplatelet shaft resulting in production of fluorescent platelets. We next sought to characterize the internal membranes biochemically and retrovirally infected MKs to express the green fluorescence protein (EGFP) tagged with the pleckstrin homology domain of phospholipase Cδ1 (PLCδ1) which binds with high specificity to phosphatidylinositol(4,5)P2 (PIP2). Young MKs stain the cell periphery as described for most other cell types. Mature MKs, however, stain the internal membranes, whereas the plasma membrane becomes PIP2-negative as shown by co-staining with CD41. Proplatelet membranes emanate from these internal PIP2-positive membranes, proving that the DMS is indeed the membrane reservoir during platelet biogenesis. Appearance of PI-4,5-P2 in the DMS occurs in proximity to PI-5-P-4-kinaseα (PI4Kα), a protein highly expressed in MKs and platelets, as shown by overexpressing EGFP-tagged kinase in primary MKs. In addition, shRNA-mediated loss of PIP4Kα or depletion of its presumptive substrate block DMS development and expansion of MK size. Thus, PI-4,5-P2 is a marker and essential component of internal membranes and is most likely introduced about the non-canonical pathway using PI5P as the substrate. PI-4,5-P2 promotes actin polymerization by activating small GTPases from the Rac/Rho superfamily as well as Wiskott-Aldrich Syndrome (WASp) family proteins. Indeed, PIP2 is associated with filamentous actin when MKs are co-stained with phalloidin. Expression of a dominant-negative N-WASp C-terminal fragment (CA-domain) that inactivats all WASp/WAVE family members leads to Arp3 binding without assembling the complete Arp2/3 complex, thus inhibiting actin filament nucleation. F-Actin staining in the infected MKs reveals a pattern similar to that of MKs treated with pharmacologic dosage of actin polymerization-antagonists like cytochalasin D, which disrupts actin filaments and inhibits proplatelet formation when administered early in MK culture. Dominant-negative WASp impairs proplatelet elaboration similarly, acting at a step past expansion of the cell volume. These observations implicate a signaling pathway wherein PI-4,5-P2 facilitates DMS development and suggests a pathway that links a DMS lipid marker with local assembly of actin fibers as a requirement for platelet biogenesis.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2005
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  • 4
    Online Resource
    Online Resource
    American Society of Hematology ; 2005
    In:  Blood Vol. 106, No. 11 ( 2005-11-16), p. 738-738
    In: Blood, American Society of Hematology, Vol. 106, No. 11 ( 2005-11-16), p. 738-738
    Abstract: Megakaryocytes are large cells within the bone marrow that undergo complex fragmentation to release up to thousands of virtually identical blood platelets into the periphery. Each platelet contains a characterisitic microtubule (MT) marginal band that is derived from MT filaments present in long protrusion-like intermediate structures, designated proplatelets, that are immediate precursors of platelets. These MT filaments are generated in the MK periphery, where they require massive mobilization that is supposed to be different from either normal interphase MT nucleation that commonly depends on γ-tubulin in the MT-organizing center. or from MTs in the mitotic spindle that require Ran·GTP, which is generated along condensed chromosomes by the chromatin-asociated guanine nucleotide exchange factor (GEF) RCC1. We first demonstrated that γ-tubulin is absent in most of the mature or proplatelet-forming MKs, where it is therefore unlikely to attribute to the total MT nucleation. MTs are tubular cytoskeletal structures that contain polymerized α- or β-tubulin subunits. Mammalian genomes share 5–6 β-tubulin isotypes of which β1-tubulin is the most divergent, especially in its C-terminal domain. β1-tubulin expression is restricted to late MKs and platelets, where it accounts for most of the β-tubulin in MT filaments. Its ablation in the mouse results in thrombocytopenia, spherocytosis and attenuated platelet function. We therefore sought to identify proteins that bind to β1-tubulin and performed a yeast two-hybrid screen using a MK-derived cDNA library. We identified a cytoplasmic Ran-binding protein, RanBP10, as a factor that associates with cellular MTs and unexpectedly harbors GEF activity toward Ran. Loss of RanBP10 in cultured MKs disrupts MT organization and its overexpression drives accumulation of extranuclear Ran and assembly of thick and abnormally long MTs. RanBP10 thus functions as a localized β-tubulin binding protein that harbors GEF activity toward Ran in the cytoplasm, much like RCC1 in the nucleus. Our results suggest that spatiotemporally restricted generation of Ran·GTP in the cytoplasm organizes specialized MTs required for thrombopoiesis and that RanBP10 provides a molecular link between Ran and non-centrosomal MTs.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2005
    detail.hit.zdb_id: 1468538-3
    detail.hit.zdb_id: 80069-7
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  • 5
    In: Blood, American Society of Hematology, Vol. 107, No. 10 ( 2006-05-15), p. 3868-3875
    Abstract: To produce blood platelets, megakaryocytes elaborate proplatelets, accompanied by expansion of membrane surface area and dramatic cytoskeletal rearrangements. The invaginated demarcation membrane system (DMS), a hallmark of mature cells, has been proposed as the source of proplatelet membranes. By direct visualization of labeled DMS, we demonstrate that this is indeed the case. Late in megakaryocyte ontogeny, the DMS gets loaded with PI-4,5-P2, a phospholipid that is confined to plasma membranes in other cells. Appearance of PI-4,5-P2 in the DMS occurs in proximity to PI-5-P-4-kinase α (PIP4Kα), and short hairpin (sh) RNA-mediated loss of PIP4Kα impairs both DMS development and expansion of megakaryocyte size. Thus, PI-4,5-P2 is a marker and possibly essential component of internal membranes. PI-4,5-P2 is known to promote actin polymerization by activating Rho-like GTPases and Wiskott-Aldrich syndrome (WASp) family proteins. Indeed, PI-4,5-P2 in the megakaryocyte DMS associates with filamentous actin. Expression of a dominant-negative N-WASp fragment or pharmacologic inhibition of actin polymerization causes similar arrests in proplatelet formation, acting at a step beyond expansion of the DMS and cell mass. These observations collectively suggest a signaling pathway wherein PI-4,5-P2 might facilitate DMS development and local assembly of actin fibers in preparation for platelet biogenesis.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2006
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    detail.hit.zdb_id: 80069-7
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  • 6
    In: Journal of Clinical Oncology, American Society of Clinical Oncology (ASCO), Vol. 39, No. 15_suppl ( 2021-05-20), p. 1018-1018
    Abstract: 1018 Background: H3B-6545, a selective, small molecule covalent antagonist of ERα demonstrated preclinical and preliminary clinical activity against ER+ breast cancer (Hamilton EP, SABCS, 2020). This study evaluated the activity and tolerability of H3B-6545 in patients (pts) with metastatic ER+, HER2-, breast cancer refractory to endocrine therapy. Methods: Patients received H3B-6545 once daily at the recommended phase II dose of 450 mg. The primary objective of the phase II is to estimate the objective response rate (ORR), progression-free survival (PFS), clinical benefit rate (CBR) and secondary objectives include safety. Results: 83 pts were treated with 450 mg in the phase II part of the trial. Additionally, 11 pts were treated with 450 mg in the phase I part of the trial and are included in this analysis. Median age was 62 years (range: 38 to 87 years), 81% had liver and/or lung metastases, and the median number of prior therapies for metastatic disease was 3 (range: 1 to 8). Prior CDK4/6 inhibitors, aromatase inhibitors, fulvestrant, and chemotherapy were received by 85%, 80%, 72%, and 50% of the pts, respectively. 58 pts (62%) had detectable ESR1 mutations in liquid biopsies, including 10 (11%) and 19 pts (20%) who had clonal Y537S and clonal D538G mutation, respectively. As of January 29, 2021, grade (gr) 2 or higher adverse events (AE) reported in ≥10% were anemia (19%), fatigue (16%), nausea (17%), and diarrhea (12%). Laboratory gr 2 or higher abnormalities reported in ≥10% pts were creatinine clearance decrease (38%), hemoglobin decrease (37%), bilirubin increase (12%), ALT increase (14%), AST increase (13%), and creatinine increase (11%). AE of gr 1 sinus bradycardia (asymptomatic) was reported in 34% and gr 2 (symptomatic, no intervention needed) was reported in 5%. Gr 2 and 3 QTcF prolongation were reported in 2 and 3 pts, respectively. There were no treatment-related deaths. Efficacy estimates are presented in the table below. Responses were observed in heavily pretreated pts, pts with visceral metastases and in pts who received prior fulvestrant, CDK4/6 inhibitor, and/or chemotherapy in the metastatic setting. Conclusions: H3B-6545 has a manageable safety profile and demonstrated single-agent anti-tumor activity in heavily pretreated ER+, HER2- mBC patients. Clinical activity was observed in pts with ESR1 mutations. Clinical trial information: NCT03250676 .[Table: see text]
    Type of Medium: Online Resource
    ISSN: 0732-183X , 1527-7755
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    Language: English
    Publisher: American Society of Clinical Oncology (ASCO)
    Publication Date: 2021
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  • 7
    In: Drug Metabolism and Pharmacokinetics, Elsevier BV, Vol. 34, No. 1 ( 2019-01), p. S22-
    Type of Medium: Online Resource
    ISSN: 1347-4367
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2019
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  • 8
    Online Resource
    Online Resource
    American Association for Cancer Research (AACR) ; 2022
    In:  Cancer Research Vol. 82, No. 12_Supplement ( 2022-06-15), p. 4123-4123
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 82, No. 12_Supplement ( 2022-06-15), p. 4123-4123
    Abstract: Background Real-world data (RWD) has been increasingly used for drug development. RWD coupled with genomic data provides an opportunity to identify the association between certain genomic alterations and response to current standard of care (SOC). Such analyses may help identify predictive biomarkers to select patients who will benefit most from SOC, and/or potential therapeutic nodes that can be pharmacologically targeted to overcome resistance to SOC. Methods We obtained Flatiron CGDB Breast Cancer (as of Q3 2020 release) data set. This data set includes clinical and genomic data from 6,918 breast cancer patients. Time to treatment discontinuation (TTD) was used as real world outcome. We performed two types of genomic-outcome association analysis: 1) Use Cox proportional hazards regression model to identify which baseline mutation (mutation occurred prior to the treatment) could predict the outcome; and 2) use Fisher exact test to identify which mutations are enriched in post-treatment tumors samples, compared to pre-treatment tumor samples. Result We found TP53 mutation is associated with shorter TTD for Palbociclib + Aromatase inhibitor (AI); Palbociclib + Fulvestrant; and endocrine monotherapy. It is consistent with the reports that TP53 mutation is poor prognostic factor (ref). Interestingly, ESR1 mutation is associated with shorter TTD for Palbociclib + AI and AI monotherapy; but not associated with TTD for Palbociclib + Fulvestrant or Fulvestrant monotherapy. On the other hand, MYC amplification is associated shorter TTD for Palbociclib + Fulvestrant or Fulvestrant monotherapy. We found that genes associated with Palbociclib + Endocrine are by and large same as those associated with endocrine monotherapy; suggesting the association is largely driven by endocrine treatment. Comparison of post-treatment vs. pre-treatment analysis found that ESR1 mutation is enriched in post treatment of AI; but not Fulvestrant. Conclusion We demonstrated that real-world clinicogenomic data could identify the biologically meaningful genomic biomarkers that are associated with real world response. This study warrants the further investigation of novel genomic biomarkers identified from the analysis. Citation Format: Kun Yu, Tenghui Chen, Manav Korpal, Ping Zhu, Zhaojie Zhang, Lihua Yu, Yonghong Xiao. Real-world data to identify the genomic association with response to CDK4/6i + Endocrine therapy in ER+ breast cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4123.
    Type of Medium: Online Resource
    ISSN: 1538-7445
    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2022
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    detail.hit.zdb_id: 1432-1
    detail.hit.zdb_id: 410466-3
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  • 9
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 77, No. 13_Supplement ( 2017-07-01), p. 126-126
    Abstract: Dysregulation of RNA splicing can cause various forms of cancer and neuromuscular disorders. Thus, developing compounds with splicing-modulating activity represents a promising therapeutic approach for these diseases. Natural products such as pladienolide, herboxidiene, and spliceostatin have been identified as potent splicing modulators that bind SF3B1, a member of the SF3b subcomplex that assembles into the U2 snRNP. Using integrated chemogenomic, structural and biochemical approaches, we show that PHF5A, another core component of the SF3b complex, is also targeted by these modulators. Whole exome sequencing of E7107 (pladienolide analogue) and herboxidiene resistant clones identified common mutations in either PHF5A-Y36, SF3B1-K1071, SF3B1-R1074, or SF3B1-V1078, which confers resistance to these modulators as assessed by splicing modulation and cell growth inhibition, suggesting a common site of interaction for these splicing modulators. We determine the crystal structure of human PHF5A and find that Y36 is located on the surface in a region of high sequence conservation. Analysis of the cryo-EM spliceosome Bact complex from yeast shows that these mutations cluster in a well-defined pocket surrounding the branch point adenosine suggesting a possible competitive mode of action for these modulators. Whole-transcriptome RNA-seq analysis reveals that PHF5A Y36C alters the profile of splicing modulators from inducing intron-retention events to exon-skipping events. Furthermore, the differential in GC content between adjacent introns and exons correlates with the relative intron strength, making some splicing events more susceptible to modulation. Collectively, we propose that PHF5A-SF3B1 is a central node for binding to these small-molecule splicing modulators offering novel approaches to modulate specific splicing events. Citation Format: Teng Teng, Jennifer Tsai, Xiaoling Puyang, Michael Seiler, Shouyong Peng, Daniel Aird, Silvia Buonamici, Benjamin Caleb, Betty Chan, Laura Corson, Jacob Feala, Peter Fekkes, Craig Karr, Manav Korpal, Yoshiharu Mizui, Eunice Park, James Palacino, Peter Smith, Vanitha Subramanian, Jeremy Wu, Lihua Yu, Agustin Chicas, Markus Warmuth, Nicholas Larsen, Ping Zhu. A chemogenomic approach reveals the action of splicing modulators at the branch point adenosine binding pocket defined by the PHF5A/SF3b complex [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 126. doi:10.1158/1538-7445.AM2017-126
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
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    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2017
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  • 10
    Online Resource
    Online Resource
    American Association for Cancer Research (AACR) ; 2019
    In:  Cancer Research Vol. 79, No. 8 ( 2019-04-15), p. 1740-1745
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 79, No. 8 ( 2019-04-15), p. 1740-1745
    Abstract: The development of tamoxifen and subsequent estrogen receptor alpha (ERα) antagonists represents a tremendous therapeutic breakthrough in the treatment of breast cancer. Despite the ability of ERα antagonists to increase survival rates, resistance to these therapies is an all-too-common occurrence. The majority of resistant tumors, including those with hotspot mutations in the ligand-binding domain of ERα, remain dependent on ERα signaling, indicating that either a more potent or novel class of antagonist could have clinical benefit. With this thought in mind, we developed a novel ERα antagonist that exhibits enhanced potency due to its ability to covalently target a unique cysteine in ER. This review describes the design of this antagonist, H3B-5942, and discusses opportunities for future improvements, which could reduce the risk of escape mutations to this therapeutic modality.
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
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    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2019
    detail.hit.zdb_id: 2036785-5
    detail.hit.zdb_id: 1432-1
    detail.hit.zdb_id: 410466-3
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