Publications by authors named "Yukinori Minoshima"

20 Publications

  • Page 1 of 1

Pharmacodynamic Biomarkers Predictive of Survival Benefit with Lenvatinib in Unresectable Hepatocellular Carcinoma: From the Phase III REFLECT Study.

Clin Cancer Res 2021 Jun 9. Epub 2021 Jun 9.

Beatson West of Scotland Cancer Centre, University of Glasgow, Glasgow, UK.

Purpose: In REFLECT, lenvatinib demonstrated an effect on overall survival (OS) by confirmation of noninferiority to sorafenib in unresectable hepatocellular carcinoma. This analysis assessed correlations between serum or tissue biomarkers and efficacy outcomes from REFLECT.

Experimental Design: Serum biomarkers (VEGF, ANG2, FGF19, FGF21, and FGF23) were measured by ELISA. Gene expression in tumor tissues was measured by the nCounter PanCancer Pathways Panel. Pharmacodynamic changes in serum biomarker levels from baseline, and associations of clinical outcomes with baseline biomarker levels, were evaluated.

Results: Four hundred and seven patients were included in the serum analysis set (lenvatinib = 279, sorafenib = 128); 58 patients were included in the gene-expression analysis set (lenvatinib = 34, sorafenib = 24). Both treatments were associated with increases in VEGF; only lenvatinib was associated with increases in FGF19 and FGF23 at all time points. Lenvatinib-treated responders had greater increases in FGF19 and FGF23 versus nonresponders at cycle 4, day 1 (FGF19: 55.2% vs. 18.3%, = 0.014; FGF23: 48.4% vs. 16.4%, = 0.0022, respectively). Higher baseline VEGF, ANG2, and FGF21 correlated with shorter OS in both treatment groups. OS was longer for lenvatinib than sorafenib [median, 10.9 vs. 6.8 months, respectively; HR, 0.53; 95% confidence interval (CI), 0.33-0.85; interaction = 0.0397] with higher baseline FGF21. In tumor tissue biomarker analysis, VEGF/FGF-enriched groups showed improved OS with lenvatinib versus the intermediate VEGF/FGF group (HR, 0.39; 95% CI, 0.16-0.91; = 0.0253).

Conclusions: Higher baseline levels of VEGF, FGF21, and ANG2 may be prognostic for shorter OS. Higher baseline FGF21 may be predictive for longer OS with lenvatinib compared with sorafenib, but this needs confirmation.
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http://dx.doi.org/10.1158/1078-0432.CCR-20-4219DOI Listing
June 2021

High Response Rate and Durability Driven by HLA Genetic Diversity in Patients with Kidney Cancer Treated with Lenvatinib and Pembrolizumab.

Mol Cancer Res 2021 May 26. Epub 2021 May 26.

Immunogenomics and Precision Oncology Platform, Memorial Sloan Kettering Cancer Center, New York, New York.

Immune checkpoint blockade (ICB) therapy has substantially improved the outcomes of patients with many types of cancers, including renal cell carcinoma (RCC). Initially studied as monotherapy, immunotherapy-based combination regimens have improved the clinical benefit achieved by ICB monotherapy and have revolutionized RCC treatment. While biomarkers like PD-L1 and tumor mutational burden (TMB) are FDA approved as biomarkers for ICB monotherapy, there are no known biomarkers for combination immunotherapies. Here, we describe the clinical outcomes and genomic determinants of response from a phase Ib/II clinical trial on patients with advanced RCC evaluating the efficacy of lenvatinib, a multi-kinase inhibitor mainly targeting VEGFR and FGFR plus pembrolizumab, an anti-PD1 immunotherapy. Concurrent treatment with lenvatinib and pembrolizumab resulted in an objective response rate of 79% (19/24) and tumor shrinkage in 96% (23/24) of patients. While tumor mutational burden (TMB) did not predict for clinical benefit, germline HLA-I diversity strongly impacted treatment efficacy. Specifically, HLA-I evolutionary divergence (HED), which measures the breadth of a patient's immunopeptidome, was associated with both improved clinical benefit and durability of response. Our results identify lenvatinib plus pembrolizumab as a highly active treatment strategy in RCC and reveal HLA-I diversity as a critical determinant of efficacy for this combination. HED also predicted better survival in a separate cohort of patients with RCC following therapy with anti-PD-1-based combination therapy. IMPLICATIONS: These findings have substantial implications for RCC therapy and for understanding immunogenetic mechanisms of efficacy and warrants further investigation.
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http://dx.doi.org/10.1158/1541-7786.MCR-21-0053DOI Listing
May 2021

Correlative serum biomarker analyses in the phase 2 trial of lenvatinib-plus-everolimus in patients with metastatic renal cell carcinoma.

Br J Cancer 2021 01 7;124(1):237-246. Epub 2020 Oct 7.

Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY, USA.

Background: No biomarkers have been established to predict treatment efficacy in renal cell carcinoma (RCC). In an exploratory retrospective analysis of a Phase 2 study, we constructed composite biomarker scores (CBSs) to predict progression-free survival (PFS) and overall survival (OS) in patients with metastatic RCC randomised to receive lenvatinib-plus-everolimus.

Methods: Of 40 biomarkers tested, the 5 most strongly associated with PFS (HGF, MIG, IL-18BP, IL-18, ANG-2) or OS (TIMP-1, M-CSF, IL-18BP, ANG-2, VEGF) were used to make a 5-factor PFS-CBS or OS-CBS, respectively. A 2-factor CBS was generated with biomarkers common to PFS-CBS and OS-CBS. Patients were divided into groups accordingly (5-factor-CBS high: 3-5, CBS-low: 0-2; 2-factor-CBS high: 1-2, CBS-low: 0).

Results: PFS/OS with lenvatinib-plus-everolimus were significantly longer in the 5-factor CBS-high group versus the CBS-low group (P = 0.0022/P < 0.0001, respectively). In the CBS-high group, PFS/OS were significantly longer with lenvatinib-plus-everolimus versus everolimus (P < 0.001/P = 0.0079, respectively); PFS was also significantly longer with lenvatinib-plus-everolimus versus lenvatinib (P = 0.0046). The 5-factor-CBS had a predictive role in PFS and OS after multivariate analysis. Similar trends were observed with the 2-factor-CBS for PFS (i.e., lenvatinib-plus-everolimus versus everolimus).

Conclusions: The 5-factor CBS may identify patients with metastatic RCC who would benefit from lenvatinib-plus-everolimus versus everolimus; additional validation is required.

Clinical Trial Registration: The clinical trial registration number is NCT01136733.
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http://dx.doi.org/10.1038/s41416-020-01092-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7782770PMC
January 2021

Activated FGF2 signaling pathway in tumor vasculature is essential for acquired resistance to anti-VEGF therapy.

Sci Rep 2020 02 19;10(1):2939. Epub 2020 Feb 19.

Tsukuba Research Laboratories, Eisai Co., Ltd., Tsukuba, Ibaraki, 5-1-3 Tokodai, Tsukuba, Ibaraki, 300-2635, Japan.

Anti-vascular endothelial growth factor (VEGF) therapy shows antitumor activity against various types of solid cancers. Several resistance mechanisms against anti-VEGF therapy have been elucidated; however, little is known about the mechanisms by which the acquired resistance arises. Here, we developed new anti-VEGF therapy-resistant models driven by chronic expression of the mouse VEGFR2 extracellular domain fused with the human IgG4 fragment crystallizable (Fc) region (VEGFR2-Fc). In the VEGFR2-Fc-expressing resistant tumors, we demonstrated that the FGFR2 signaling pathway was activated, and pericytes expressing high levels of FGF2 were co-localized with endothelial cells. Lenvatinib, a multiple tyrosine kinase inhibitor including VEGFR and FGFR inhibition, showed marked antitumor activity against VEGFR2-Fc-expressing resistant tumors accompanied with a decrease in the area of tumor vessels and suppression of phospho-FGFR2 in tumors. Our findings reveal the key role that intercellular FGF2 signaling between pericytes and endothelial cells plays in maintaining the tumor vasculature in anti-VEGF therapy-resistant tumors.
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http://dx.doi.org/10.1038/s41598-020-59853-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7031295PMC
February 2020

Lenvatinib inhibits angiogenesis and tumor fibroblast growth factor signaling pathways in human hepatocellular carcinoma models.

Cancer Med 2018 06 7;7(6):2641-2653. Epub 2018 May 7.

Tsukuba Research Laboratories, Eisai Co., Ltd., Ibaraki, Japan.

Unresectable hepatocellular carcinoma (uHCC) is one of the most lethal and prevalent cancers worldwide, and current systemic therapeutic options for uHCC are limited. Lenvatinib, a multiple receptor tyrosine kinase inhibitor targeting vascular endothelial growth factor receptors (VEGFRs) and fibroblast growth factor receptors (FGFRs), recently demonstrated a treatment effect on overall survival by statistical confirmation of noninferiority to sorafenib in a phase 3 study of uHCC. Here, we investigated mechanisms underlying the antitumor activity of lenvatinib in preclinical HCC models. In vitro proliferation assay of nine human HCC cell lines showed that lenvatinib selectively inhibited proliferation of FGF signal-activated HCC cells including FGF19-expressing Hep3B2.1-7. Lenvatinib suppressed phosphorylation of FRS2, a substrate of FGFR1-4, in these cells in a concentration-dependent manner. Lenvatinib inhibited in vivo tumor growth in Hep3B2.1-7 and SNU-398 xenografts and decreased phosphorylation of FRS2 and Erk1/2 within the tumor tissues. Lenvatinib also exerted antitumor activity and potently reduced tumor microvessel density in PLC/PRF/5 xenograft model and two HCC patient-derived xenograft models. These results suggest that lenvatinib has antitumor activity consistently across diverse HCC models, and that targeting of tumor FGF signaling pathways and anti-angiogenic activity underlies its antitumor activity against HCC tumors.
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http://dx.doi.org/10.1002/cam4.1517DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6010799PMC
June 2018

Selective degradation of splicing factor CAPERα by anticancer sulfonamides.

Nat Chem Biol 2017 06 24;13(6):675-680. Epub 2017 Apr 24.

Eisai Inc., Woodcliff Lake, New Jersey, USA.

Target-protein degradation is an emerging field in drug discovery and development. In particular, the substrate-receptor proteins of the cullin-ubiquitin ligase system play a key role in selective protein degradation, which is an essential component of the anti-myeloma activity of immunomodulatory drugs (IMiDs), such as lenalidomide. Here, we demonstrate that a series of anticancer sulfonamides NSC 719239 (E7820), indisulam, and NSC 339004 (chloroquinoxaline sulfonamide, CQS) induce proteasomal degradation of the U2AF-related splicing factor coactivator of activating protein-1 and estrogen receptors (CAPERα) via CRL4 mediated ubiquitination in human cancer cell lines. Both CRISPR-Cas9-based knockout of DCAF15 and a single amino acid substitution of CAPERα conferred resistance against sulfonamide-induced CAPERα degradation and cell-growth inhibition. Thus, these sulfonamides represent selective chemical probes for disrupting CAPERα function and designate DCAFs as promising drug targets for promoting selective protein degradation in cancer therapy.
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http://dx.doi.org/10.1038/nchembio.2363DOI Listing
June 2017

E7090, a Novel Selective Inhibitor of Fibroblast Growth Factor Receptors, Displays Potent Antitumor Activity and Prolongs Survival in Preclinical Models.

Mol Cancer Ther 2016 11 17;15(11):2630-2639. Epub 2016 Aug 17.

Tsukuba Research Laboratories, Eisai Co., Ltd, Tsukuba-shi, Ibaraki, Japan.

The FGFR signaling pathway has a crucial role in proliferation, survival, and migration of cancer cells, tumor angiogenesis, and drug resistance. FGFR genetic abnormalities, such as gene fusion, mutation, and amplification, have been implicated in several types of cancer. Therefore, FGFRs are considered potential targets for cancer therapy. E7090 is an orally available and selective inhibitor of the tyrosine kinase activities of FGFR1, -2, and -3. In kinetic analyses of the interaction between E7090 and FGFR1 tyrosine kinase, E7090 associated more rapidly with FGFR1 than did the type II FGFR1 inhibitor ponatinib, and E7090 dissociated more slowly from FGFR1, with a relatively longer residence time, than did the type I FGFR1 inhibitor AZD4547, suggesting that its kinetics are more similar to the type V inhibitors, such as lenvatinib. E7090 showed selective antiproliferative activity against cancer cell lines harboring FGFR genetic abnormalities and decreased tumor size in a mouse xenograft model using cell lines with dysregulated FGFR Furthermore, E7090 administration significantly prolonged the survival of mice with metastasized tumors in the lung. Our results suggest that E7090 is a promising candidate as a therapeutic agent for the treatment of tumors harboring FGFR genetic abnormalities. It is currently being investigated in a phase I clinical trial. Mol Cancer Ther; 15(11); 2630-9. ©2016 AACR.
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http://dx.doi.org/10.1158/1535-7163.MCT-16-0261DOI Listing
November 2016

Preclinical Evidence of Anti-Tumor Activity Induced by EZH2 Inhibition in Human Models of Synovial Sarcoma.

PLoS One 2016 8;11(7):e0158888. Epub 2016 Jul 8.

Epizyme Inc., Cambridge, Massachusetts, United States of America.

The catalytic activities of covalent and ATP-dependent chromatin remodeling are central to regulating the conformational state of chromatin and the resultant transcriptional output. The enzymes that catalyze these activities are often contained within multiprotein complexes in nature. Two such multiprotein complexes, the polycomb repressive complex 2 (PRC2) methyltransferase and the SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeler have been reported to act in opposition to each other during development and homeostasis. An imbalance in their activities induced by mutations/deletions in complex members (e.g. SMARCB1) has been suggested to be a pathogenic mechanism in certain human cancers. Here we show that preclinical models of synovial sarcoma-a cancer characterized by functional SMARCB1 loss via its displacement from the SWI/SNF complex through the pathognomonic SS18-SSX fusion protein-display sensitivity to pharmacologic inhibition of EZH2, the catalytic subunit of PRC2. Treatment with tazemetostat, a clinical-stage, selective and orally bioavailable small-molecule inhibitor of EZH2 enzymatic activity reverses a subset of synovial sarcoma gene expression and results in concentration-dependent cell growth inhibition and cell death specifically in SS18-SSX fusion-positive cells in vitro. Treatment of mice bearing either a cell line or two patient-derived xenograft models of synovial sarcoma leads to dose-dependent tumor growth inhibition with correlative inhibition of trimethylation levels of the EZH2-specific substrate, lysine 27 on histone H3. These data demonstrate a dependency of SS18-SSX-positive, SMARCB1-deficient synovial sarcomas on EZH2 enzymatic activity and suggests the potential utility of EZH2-targeted drugs in these genetically defined cancers.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0158888PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4938529PMC
July 2017

EPZ011989, A Potent, Orally-Available EZH2 Inhibitor with Robust in Vivo Activity.

ACS Med Chem Lett 2015 May 4;6(5):491-5. Epub 2015 Mar 4.

Epizyme, Inc. , 400 Technology Square, Fourth Floor, Cambridge, Massachusetts 02139, United States.

Inhibitors of the protein methyltransferase Enhancer of Zeste Homolog 2 (EZH2) may have significant therapeutic potential for the treatment of B cell lymphomas and other cancer indications. The ability of the scientific community to explore fully the spectrum of EZH2-associated pathobiology has been hampered by the lack of in vivo-active tool compounds for this enzyme. Here we report the discovery and characterization of EPZ011989, a potent, selective, orally bioavailable inhibitor of EZH2 with useful pharmacokinetic properties. EPZ011989 demonstrates significant tumor growth inhibition in a mouse xenograft model of human B cell lymphoma. Hence, this compound represents a powerful tool for the expanded exploration of EZH2 activity in biology.
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http://dx.doi.org/10.1021/acsmedchemlett.5b00037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4434464PMC
May 2015

Antitumor activity of lenvatinib (e7080): an angiogenesis inhibitor that targets multiple receptor tyrosine kinases in preclinical human thyroid cancer models.

J Thyroid Res 2014 10;2014:638747. Epub 2014 Sep 10.

Biomarkers and Personalized Medicine Core Function Unit, Eisai Inc., 4 Corporate Drive, Andover, MA 01810, USA.

Inhibition of tumor angiogenesis by blockading the vascular endothelial growth factor (VEGF) signaling pathway is a promising therapeutic strategy for thyroid cancer. Lenvatinib mesilate (lenvatinib) is a potent inhibitor of VEGF receptors (VEGFR1-3) and other prooncogenic and prooncogenic receptor tyrosine kinases, including fibroblast growth factor receptors (FGFR1-4), platelet derived growth factor receptor α (PDGFRα), KIT, and RET. We examined the antitumor activity of lenvatinib against human thyroid cancer xenograft models in nude mice. Orally administered lenvatinib showed significant antitumor activity in 5 differentiated thyroid cancer (DTC), 5 anaplastic thyroid cancer (ATC), and 1 medullary thyroid cancer (MTC) xenograft models. Lenvatinib also showed antiangiogenesis activity against 5 DTC and 5 ATC xenografts, while lenvatinib showed in vitro antiproliferative activity against only 2 of 11 thyroid cancer cell lines: that is, RO82-W-1 and TT cells. Western blot analysis showed that cultured RO82-W-1 cells overexpressed FGFR1 and that lenvatinib inhibited the phosphorylation of FGFR1 and its downstream effector FRS2. Lenvatinib also inhibited the phosphorylation of RET with the activated mutation C634W in TT cells. These data demonstrate that lenvatinib provides antitumor activity mainly via angiogenesis inhibition but also inhibits FGFR and RET signaling pathway in preclinical human thyroid cancer models.
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http://dx.doi.org/10.1155/2014/638747DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4177084PMC
October 2014

Selective inhibition of EZH2 by EPZ-6438 leads to potent antitumor activity in EZH2-mutant non-Hodgkin lymphoma.

Mol Cancer Ther 2014 Apr 21;13(4):842-54. Epub 2014 Feb 21.

Authors' Affiliations: Epizyme Inc., Cambridge; Eisai Inc., Andover, Massachusetts; and Eisai Co. Ltd., Tsukuba-shi, Ibaraki, Japan.

Mutations within the catalytic domain of the histone methyltransferase EZH2 have been identified in subsets of patients with non-Hodgkin lymphoma (NHL). These genetic alterations are hypothesized to confer an oncogenic dependency on EZH2 enzymatic activity in these cancers. We have previously reported the discovery of EPZ005678 and EPZ-6438, potent and selective S-adenosyl-methionine-competitive small molecule inhibitors of EZH2. Although both compounds are similar with respect to their mechanism of action and selectivity, EPZ-6438 possesses superior potency and drug-like properties, including good oral bioavailability in animals. Here, we characterize the activity of EPZ-6438 in preclinical models of NHL. EPZ-6438 selectively inhibits intracellular lysine 27 of histone H3 (H3K27) methylation in a concentration- and time-dependent manner in both EZH2 wild-type and mutant lymphoma cells. Inhibition of H3K27 trimethylation (H3K27Me3) leads to selective cell killing of human lymphoma cell lines bearing EZH2 catalytic domain point mutations. Treatment of EZH2-mutant NHL xenograft-bearing mice with EPZ-6438 causes dose-dependent tumor growth inhibition, including complete and sustained tumor regressions with correlative diminution of H3K27Me3 levels in tumors and selected normal tissues. Mice dosed orally with EPZ-6438 for 28 days remained tumor free for up to 63 days after stopping compound treatment in two EZH2-mutant xenograft models. These data confirm the dependency of EZH2-mutant NHL on EZH2 activity and portend the utility of EPZ-6438 as a potential treatment for these genetically defined cancers.
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http://dx.doi.org/10.1158/1535-7163.MCT-13-0773DOI Listing
April 2014

Novel ATP-competitive MEK inhibitor E6201 is effective against vemurafenib-resistant melanoma harboring the MEK1-C121S mutation in a preclinical model.

Mol Cancer Ther 2014 Apr 21;13(4):823-32. Epub 2014 Jan 21.

Authors' Affiliations: Eisai Co., Ltd.; and Genomics-Based Drug Discovery, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.

Many clinical cases of acquired resistance to the BRAF inhibitor vemurafenib have recently been reported. One of the causes of this acquired resistance is the BRAF downstream kinase point mutation MEK1-C121S. This mutation confers resistance to not only vemurafenib, but also to the allosteric MEK inhibitor selumetinib (AZD6244). Here, we investigated the pharmacologic activities and effectiveness of the novel MEK inhibitor E6201 against BRAF (v-raf murine sarcoma viral oncogene homolog B1)-V600E mutant melanoma harboring the MEK1-C121S mutation. A cell-free assay confirmed that E6201 is an ATP-competitive MEK inhibitor, meaning it has a different binding mode with MEK compared with allosteric MEK inhibitors. E6201 is more effective against BRAF-V600E mutant melanoma compared with BRAF wild-type melanoma based on MEK inhibition. We found that the acquired MEK1-C121S mutation in BRAF-V600E mutant melanoma conferred resistance to both vemurafenib and selumetinib but not E6201. The effectiveness of E6201 in this preclinical study is a result of its binding with MEK1 far from the C121S point mutation so the mutation is unable to influence the MAPK pathway inhibitory activity. These results support further clinical investigation of E6201.
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http://dx.doi.org/10.1158/1535-7163.MCT-13-0667DOI Listing
April 2014

Biological validation that SF3b is a target of the antitumor macrolide pladienolide.

FEBS J 2011 Dec 31;278(24):4870-80. Epub 2011 Oct 31.

Tsukuba Research Laboratories, Eisai Co., Ltd, Tsukuba, Ibaraki, Japan.

Pladienolide is a naturally occurring macrolide that binds to the SF3b complex to inhibit mRNA splicing. It has not been fully validated whether the splicing impairment is a relevant mechanism for the potent antitumor activity of pladienolide. We established pladienolide-resistant clones from WiDr and DLD1 colorectal cancer cells that were insensitive to the inhibitory action of pladienolide on cell proliferation and splicing. An mRNA-Seq differential analysis revealed that these two cell lines have an identical mutation at Arg1074 in the gene for SF3B1, which encodes a subunit of the SF3b complex. Reverse expression of the mutant protein transferred pladienolide resistance to WiDr cells. Furthermore, immunoprecipitation analysis using a radiolabeled probe showed that the mutation impaired the binding affinity of paldienolide to its target. These results clearly demonstrate that pladienolide exerts its potent activity by targeting SF3b and also suggest that inhibition of SF3b is a promising drug target for anticancer therapy.
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http://dx.doi.org/10.1111/j.1742-4658.2011.08387.xDOI Listing
December 2011

A Rac GTPase-activating protein, MgcRacGAP, is a nuclear localizing signal-containing nuclear chaperone in the activation of STAT transcription factors.

Mol Cell Biol 2009 Apr 21;29(7):1796-813. Epub 2009 Jan 21.

Division of Cellular Therapy, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.

In addition to their pleiotropic functions under physiological conditions, transcription factors STAT3 and STAT5 also have oncogenic activities, but how activated STATs are transported to the nucleus has not been fully understood. Here we show that an MgcRacGAP mutant lacking its nuclear localizing signal (NLS) blocks nuclear translocation of p-STATs both in vitro and in vivo. Unlike wild-type MgcRacGAP, this mutant did not promote complex formation of phosphorylated STATs (p-STATs) with importin alpha in the presence of GTP-bound Rac1, suggesting that MgcRacGAP functions as an NLS-containing nuclear chaperone. We also demonstrate that mutants of STATs lacking the MgcRacGAP binding site (the strand betab) are hardly tyrosine phosphorylated after cytokine stimulation. Intriguingly, mutants harboring small deletions in the C'-adjacent region (betab-betac loop region) of the strand betab became constitutively active with the enhanced binding to MgcRacGAP. The molecular basis of this phenomenon will be discussed, based on the computer-assisted tertiary structure models of STAT3. Thus, MgcRacGAP functions as both a critical mediator of STAT's tyrosine phosphorylation and an NLS-containing nuclear chaperone of p-STATs.
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http://dx.doi.org/10.1128/MCB.01423-08DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2655612PMC
April 2009

The spatial and temporal expression of delta-like protein 1 in the rat pituitary gland during development.

Histochem Cell Biol 2009 Jan 27;131(1):141-53. Epub 2008 Aug 27.

Integrated Bioscience Section, Graduate School of Science and Technology, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka 422-8529, Japan.

An analysis of secreted proteins by the signal sequence trap method using a cDNA library of the rat pituitary anlage at embryonic days (E) 13.5 revealed the abundant expression of delta-like protein 1 (Dlk1) in the pituitary gland. Dlk1, an epidermal growth factor-like repeat protein in preadipocytes, functions in maintaining the preadipose state. Expression of Dlk1 mRNA in the pituitary at E13.5 and in the adult pituitary was confirmed by in situ hybridization. The expression pattern of Dlk1 during pituitary development was also studied by immunohistochemistry. Dlk1 protein first appeared in Rathke's pouch and the infundibulum at E11.5; as development proceeded, expression became restricted to the pars distalis and pars tuberalis (PT). Dlk1 was expressed in most ACTH cells during the embryonic stages, but its expression was limited to only a few ACTH cells in the adult pituitary. It was also expressed in a small population of TSH, GTH, and PRL cells throughout development, whereas it was present in the cytoplasm of most GH cells at all developmental stages. Similarly, Dlk1 was localized in the cytoplasm of PT cells during development. These findings provide new insights into the mechanism of Dlk1 regarding its regulation of pituitary hormone-secreting cells during development.
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http://dx.doi.org/10.1007/s00418-008-0494-8DOI Listing
January 2009

Rac1 and a GTPase-activating protein, MgcRacGAP, are required for nuclear translocation of STAT transcription factors.

J Cell Biol 2006 Dec;175(6):937-46

Division of Cellular Therapy, The Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.

STAT transcription factors are tyrosine phosphorylated upon cytokine stimulation and enter the nucleus to activate target genes. We show that Rac1 and a GTPase-activating protein, MgcRacGAP, bind directly to p-STAT5A and are required to promote its nuclear translocation. Using permeabilized cells, we find that nuclear translocation of purified p-STAT5A is dependent on the addition of GTP-bound Rac1, MgcRacGAP, importin alpha, and importin beta. p-STAT3 also enters the nucleus via this transport machinery, and mutant STATs lacking the MgcRacGAP binding site do not enter the nucleus even after phosphorylation. We conclude that GTP-bound Rac1 and MgcRacGAP function as a nuclear transport chaperone for activated STATs.
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http://dx.doi.org/10.1083/jcb.200604073DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2064703PMC
December 2006

The constitutive centromere component CENP-50 is required for recovery from spindle damage.

Mol Cell Biol 2005 Dec;25(23):10315-28

National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan.

We identified CENP-50 as a novel kinetochore component. We found that CENP-50 is a constitutive component of the centromere that colocalizes with CENP-A and CENP-H throughout the cell cycle in vertebrate cells. To determine the precise role of CENP-50, we examined its role in centromere function by generating a loss-of-function mutant in the chicken DT40 cell line. The CENP-50 knockout was not lethal; however, the growth rate of cells with this mutation was slower than that of wild-type cells. We observed that the time for CENP-50-deficient cells to complete mitosis was longer than that for wild-type cells. Centromeric localization of CENP-50 was abolished in both CENP-H- and CENP-I-deficient cells. Coimmunoprecipitation experiments revealed that CENP-50 interacted with the CENP-H/CENP-I complex in chicken DT40 cells. We also observed severe mitotic defects in CENP-50-deficient cells with apparent premature sister chromatid separation when the mitotic checkpoint was activated, indicating that CENP-50 is required for recovery from spindle damage.
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http://dx.doi.org/10.1128/MCB.25.23.10315-10328.2005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1291240PMC
December 2005

A GTPase-activating protein binds STAT3 and is required for IL-6-induced STAT3 activation and for differentiation of a leukemic cell line.

Blood 2004 Dec 29;104(12):3550-7. Epub 2004 Jul 29.

Division of Cellular Therapy, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.

We previously identified a guanosine triphosphatase (GTPase)-activating protein (GAP) male germ cell Rac GAP (MgcRacGAP) that enhanced interleukin-6 (IL-6)-induced macrophage differentiation of murine M1 leukemia cells. Later, MgcRacGAP was found to play crucial roles in cell division. However, how MgcRacGAP enhanced IL-6-induced differentiation remained elusive. Here we show that MgcRacGAP enhances IL-6-induced differentiation through enhancement of signal transducer and activator of transcription-3 (STAT3) activation. MgcRacGAP, Rac, and STAT3 formed a complex in IL-6-stimulated M1 cells, where MgcRacGAP interacted with Rac1 and STAT3 through its cysteine-rich domain and GAP domain. In reporter assays, the wild-type MgcRacGAP enhanced transcriptional activation of STAT3 while a GAP-domain deletion mutant (DeltaGAP) did not significantly enhance it, suggesting that the GAP domain was required for enhancement of STAT3-dependent transcription. Intriguingly, M1 cells expressing DeltaGAP had no effect on the differentiation signal of IL-6, while forced expression of MgcRacGAP rendered M1 cells hyperresponsive to the IL-6-induced differentiation. Moreover, knockdown of MgcRacGAP by RNA interference profoundly suppressed STAT3 activation, implicating MgcRacGAP in the STAT3-dependent transcription. All together, our data not only reveal an important role for MgcRacGAP in STAT3 activation, but also demonstrate that MgcRacGAP regulates IL-6-induced cellular differentiation in which STAT3 plays a pivotal role.
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http://dx.doi.org/10.1182/blood-2004-03-1066DOI Listing
December 2004

Phosphorylation by aurora B converts MgcRacGAP to a RhoGAP during cytokinesis.

Dev Cell 2003 Apr;4(4):549-60

Division of Hematopoietic Factors, The Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.

Cell division is finely controlled by various molecules including small G proteins and kinases/phosphatases. Among these, Aurora B, RhoA, and the GAP MgcRacGAP have been implicated in cytokinesis, but their underlying mechanisms of action have remained unclear. Here, we show that MgcRacGAP colocalizes with Aurora B and RhoA, but not Rac1/Cdc42, at the midbody. We also report that Aurora B phosphorylates MgcRacGAP on serine residues and that this modification induces latent GAP activity toward RhoA in vitro. Expression of a kinase-defective mutant of Aurora B disrupts cytokinesis and inhibits phosphorylation of MgcRacGAP at Ser387, but not its localization to the midbody. Overexpression of a phosphorylation-deficient MgcRacGAP-S387A mutant, but not phosphorylation-mimic MgcRacGAP-S387D mutant, arrests cytokinesis at a late stage and induces polyploidy. Together, these findings indicate that during cytokinesis, MgcRacGAP, previously known as a GAP for Rac/Cdc42, is functionally converted to a RhoGAP through phosphorylation by Aurora B.
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http://dx.doi.org/10.1016/s1534-5807(03)00089-3DOI Listing
April 2003
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