title: Mice null for the deubiquitinase USP18 spontaneously develop leiomyosarcomas.
abstract: BACKGROUND
  USP18 (ubiquitin-specific protease 18) removes ubiquitin-like modifier interferon stimulated gene 15 (ISG15) from conjugated proteins. USP18 null mice in a FVB/N background develop tumors as early as 2 months of age. These tumors are leiomyosarcomas and thus represent a new murine model for this disease.
  
  
  METHODS
  Heterozygous USP18 +/- FVB/N mice were bred to generate wild-type, heterozygous and homozygous cohorts. Tumors were characterized immunohistochemically and two cell lines were derived from independent tumors. Cell lines were karyotyped and their responses to restoration of USP18 activity assessed. Drug testing and tumorigenic assays were also performed. USP18 immunohistochemical staining in a large series of human leiomyosacomas was examined.
  
  
  RESULTS
  USP18 -/- FVB/N mice spontaneously develop tumors predominantly on the back of the neck with most tumors evident between 6-12 months (80 % penetrance). Immunohistochemical characterization of the tumors confirmed they were leiomyosarcomas, which originate from smooth muscle. Restoration of USP18 activity in sarcoma-derived cell lines did not reduce anchorage dependent or independent growth or xenograft tumor formation demonstrating that these cells no longer require USP18 suppression for tumorigenesis. Karyotyping revealed that both tumor-derived cell lines were aneuploid with extra copies of chromosomes 3 and 15. Chromosome 15 contains the Myc locus and MYC is also amplified in human leiomyosarcomas. MYC protein levels were elevated in both murine leiomyosarcoma cell lines. Stabilized P53 protein was detected in a subset of these murine tumors, another feature of human leiomyosarcomas. Immunohistochemical analyses of USP18 in human leiomyosarcomas revealed a range of staining intensities with the highest USP18 expression in normal vascular smooth muscle. USP18 tissue array analysis of primary leiomyosarcomas from 89 patients with a clinical database revealed cases with reduced USP18 levels had a significantly decreased time to metastasis (P = 0.0441).
  
  
  CONCLUSIONS
  USP18 null mice develop leiomyosarcoma recapitulating key features of clinical leiomyosarcomas and patients with reduced-USP18 tumor levels have an unfavorable outcome. USP18 null mice and the derived cell lines represent clinically-relevant models of leiomyosarcoma and can provide insights into both leiomyosarcoma biology and therapy.
authors.affiliation: Department of Pharmacology and Toxicology, Dartmouth, Hanover, NH, USA. Fadzai.Chinyengetere.MED@dartmouth.edu.|Geisel School of Medicine, Dartmouth, Hanover, NH, USA. Fadzai.Chinyengetere.MED@dartmouth.edu.|Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA. Fadzai.Chinyengetere.MED@dartmouth.edu.
authors.forename: Fadzai
authors.initials: F
authors.lastname: Chinyengetere
authors.affiliation: Department of Pharmacology and Toxicology, Dartmouth, Hanover, NH, USA. DJSekula@mdanderson.org.|Geisel School of Medicine, Dartmouth, Hanover, NH, USA. DJSekula@mdanderson.org.|Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA. DJSekula@mdanderson.org.
authors.forename: David J
authors.initials: DJ
authors.lastname: Sekula
authors.affiliation: Department of Pharmacology and Toxicology, Dartmouth, Hanover, NH, USA. yun.lu@dartmouth.edu.|Geisel School of Medicine, Dartmouth, Hanover, NH, USA. yun.lu@dartmouth.edu.|Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA. yun.lu@dartmouth.edu.
authors.forename: Yun
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Geisel School of Medicine, Dartmouth, Hanover, NH, USA. giustini@stanford.edu.|Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA. giustini@stanford.edu.|Thayer School of Engineering, Dartmouth College, Hanover, NH, USA. giustini@stanford.edu.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Giustini
authors.affiliation: Norris Cotton Cancer Center, Lebanon, NH, USA. aarti.sanglikar@dartmouth.edu.
authors.forename: Aarti
authors.initials: A
authors.lastname: Sanglikar
authors.affiliation: Department of Pharmacology and Toxicology, Dartmouth, Hanover, NH, USA. MKawakami@mdanderson.org.|Geisel School of Medicine, Dartmouth, Hanover, NH, USA. MKawakami@mdanderson.org.|Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA. MKawakami@mdanderson.org.
authors.forename: Masanori
authors.initials: M
authors.lastname: Kawakami
authors.affiliation: Department of Pharmacology and Toxicology, Dartmouth, Hanover, NH, USA. tmtianma@gmail.com.|Geisel School of Medicine, Dartmouth, Hanover, NH, USA. tmtianma@gmail.com.|Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA. tmtianma@gmail.com.
authors.forename: Tian
authors.initials: T
authors.lastname: Ma
authors.affiliation: Comparative Molecular Cytogenetics Core, Mouse Cancer Genetics Program, National Cancer Institute, Frederick, MD, USA. burketts@mail.nih.gov.
authors.forename: Sandra S
authors.initials: SS
authors.lastname: Burkett
authors.affiliation: Department of Surgery, Dartmouth, Hanover, NH, USA. Burton.Eisenberg@hoag.org.|Norris Cotton Cancer Center, Lebanon, NH, USA. Burton.Eisenberg@hoag.org.|Geisel School of Medicine, Dartmouth, Hanover, NH, USA. Burton.Eisenberg@hoag.org.|Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA. Burton.Eisenberg@hoag.org.
authors.forename: Burton L
authors.initials: BL
authors.lastname: Eisenberg
authors.affiliation: Department of Pathology, Dartmouth, Hanover, NH, USA. Wendy.A.Wells@dartmouth.edu.|Norris Cotton Cancer Center, Lebanon, NH, USA. Wendy.A.Wells@dartmouth.edu.|Geisel School of Medicine, Dartmouth, Hanover, NH, USA. Wendy.A.Wells@dartmouth.edu.|Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA. Wendy.A.Wells@dartmouth.edu.
authors.forename: Wendy A
authors.initials: WA
authors.lastname: Wells
authors.affiliation: Department of Surgery, Dartmouth, Hanover, NH, USA. P.Jack.Hoopes@dartmouth.edu.|Norris Cotton Cancer Center, Lebanon, NH, USA. P.Jack.Hoopes@dartmouth.edu.|Geisel School of Medicine, Dartmouth, Hanover, NH, USA. P.Jack.Hoopes@dartmouth.edu.|Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA. P.Jack.Hoopes@dartmouth.edu.|Thayer School of Engineering, Dartmouth College, Hanover, NH, USA. P.Jack.Hoopes@dartmouth.edu.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Hoopes
authors.affiliation: Department of Pathology, The Mount Sinai Hospital, New York, NY, USA. elizabeth.demicco@mountsinai.org.
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Demicco
authors.affiliation: Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA. alazar@mdanderson.org.|Sarcoma Research Center, The University of Texas MD Anderson Cancer Center, Houston, TX, USA. alazar@mdanderson.org.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Lazar
authors.affiliation: Sarcoma Research Center, The University of Texas MD Anderson Cancer Center, Houston, TX, USA. ktorres@mdanderson.org.|Department of Surgical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA. ktorres@mdanderson.org.
authors.forename: Keila E
authors.initials: KE
authors.lastname: Torres
authors.affiliation: Department of Pathology, Dartmouth, Hanover, NH, USA. Vincent.A.Memoli@hitchcock.org.|Norris Cotton Cancer Center, Lebanon, NH, USA. Vincent.A.Memoli@hitchcock.org.|Geisel School of Medicine, Dartmouth, Hanover, NH, USA. Vincent.A.Memoli@hitchcock.org.|Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA. Vincent.A.Memoli@hitchcock.org.
authors.forename: Vincent
authors.initials: V
authors.lastname: Memoli
authors.affiliation: Department of Pharmacology and Toxicology, Dartmouth, Hanover, NH, USA. sarah.freemantle@dartmouth.edu.|Geisel School of Medicine, Dartmouth, Hanover, NH, USA. sarah.freemantle@dartmouth.edu.|Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA. sarah.freemantle@dartmouth.edu.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Freemantle
authors.affiliation: Department of Pharmacology and Toxicology, Dartmouth, Hanover, NH, USA. ethan.dmitrovsky@dartmouth.edu.|Department of Medicine, Dartmouth, Hanover, NH, USA. ethan.dmitrovsky@dartmouth.edu.|Norris Cotton Cancer Center, Lebanon, NH, USA. ethan.dmitrovsky@dartmouth.edu.|Geisel School of Medicine, Dartmouth, Hanover, NH, USA. ethan.dmitrovsky@dartmouth.edu.|Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA. ethan.dmitrovsky@dartmouth.edu.|Present address: MD Anderson Cancer Center, Houston, TX, 77030-4009, USA. ethan.dmitrovsky@dartmouth.edu.
authors.forename: Ethan
authors.initials: E
authors.lastname: Dmitrovsky
mesh_terms: D000818:Animals; D063646:Carcinogenesis / Q000235:genetics*; D004195:Disease Models, Animal; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007890:Leiomyosarcoma / Q000235:genetics* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D009362:Neoplasm Metastasis; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D043222:Ubiquitin Thiolesterase / Q000096:biosynthesis / Q000235:genetics*; D014594:Uterine Neoplasms / Q000235:genetics* / Q000473:pathology
chemical_list: D016159:Tumor Suppressor Protein p53; C118306:Usp18 protein, mouse; D043222:Ubiquitin Thiolesterase