title: Mithramycin Depletes Specificity Protein 1 and Activates p53 to Mediate Senescence and Apoptosis of Malignant Pleural Mesothelioma Cells.
abstract: OBJECTIVE
  Specificity protein 1 (SP1) is an oncogenic transcription factor overexpressed in various human malignancies. This study sought to examine SP1 expression in malignant pleural mesotheliomas (MPM) and ascertain the potential efficacy of targeting SP1 in these neoplasms.
  
  
  METHODS
  qRT-PCR, immunoblotting, and immunohistochemical techniques were used to evaluate SP1 expression in cultured MPM cells and MPM specimens and normal mesothelial cells/pleura. MTS, chemotaxis, soft agar, β-galactosidase, and Apo-BrdUrd techniques were used to assess proliferation, migration, clonogenicity, senescence, and apoptosis in MPM cells following SP1 knockdown, p53 overexpression, or mithramycin treatment. Murine subcutaneous and intraperitoneal xenograft models were used to examine effects of mithramycin on MPM growth in vivo. Microarray, qRT-PCR, immunoblotting, and chromatin immunoprecipitation techniques were used to examine gene expression profiles mediated by mithramycin and combined SP1 knockdown/p53 overexpression and correlate these changes with SP1 and p53 levels within target gene promoters.
  
  
  RESULTS
  MPM cells and tumors exhibited higher SP1 mRNA and protein levels relative to control cells/tissues. SP1 knockdown significantly inhibited proliferation, migration, and clonogenicity of MPM cells. Mithramycin depleted SP1 and activated p53, dramatically inhibiting proliferation and clonogenicity of MPM cells. Intraperitoneal mithramycin significantly inhibited growth of subcutaneous MPM xenografts and completely eradicated mesothelioma carcinomatosis in 75% of mice. Mithramycin modulated genes mediating oncogene signaling, cell-cycle regulation, senescence, and apoptosis in vitro and in vivo. The growth-inhibitory effects of mithramycin in MPM cells were recapitulated by combined SP1 knockdown/p53 overexpression.
  
  
  CONCLUSIONS
  These findings provide preclinical rationale for phase II evaluation of mithramycin in patients with mesothelioma.
authors.affiliation: Thoracic Epigenetics Section, Thoracic and GI Oncology Branch, National Cancer Institute, Bethesda, Maryland.
authors.forename: Mahadev
authors.initials: M
authors.lastname: Rao
authors.affiliation: Thoracic Epigenetics Section, Thoracic and GI Oncology Branch, National Cancer Institute, Bethesda, Maryland.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Atay
authors.affiliation: Thoracic Epigenetics Section, Thoracic and GI Oncology Branch, National Cancer Institute, Bethesda, Maryland.
authors.forename: Vivek
authors.initials: V
authors.lastname: Shukla
authors.affiliation: Thoracic Epigenetics Section, Thoracic and GI Oncology Branch, National Cancer Institute, Bethesda, Maryland.
authors.forename: Young
authors.initials: Y
authors.lastname: Hong
authors.affiliation: Thoracic Epigenetics Section, Thoracic and GI Oncology Branch, National Cancer Institute, Bethesda, Maryland.
authors.forename: Trevor
authors.initials: T
authors.lastname: Upham
authors.affiliation: Thoracic Epigenetics Section, Thoracic and GI Oncology Branch, National Cancer Institute, Bethesda, Maryland.
authors.forename: R Taylor
authors.initials: RT
authors.lastname: Ripley
authors.affiliation: Thoracic Epigenetics Section, Thoracic and GI Oncology Branch, National Cancer Institute, Bethesda, Maryland.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Hong
authors.affiliation: Thoracic Epigenetics Section, Thoracic and GI Oncology Branch, National Cancer Institute, Bethesda, Maryland.
authors.forename: Mary
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Thoracic Epigenetics Section, Thoracic and GI Oncology Branch, National Cancer Institute, Bethesda, Maryland.
authors.forename: Emily
authors.initials: E
authors.lastname: Reardon
authors.affiliation: Laboratory of Pathology, National Cancer Institute, Bethesda, Maryland.
authors.forename: Patricia
authors.initials: P
authors.lastname: Fetsch
authors.affiliation: Laboratory of Pathology, National Cancer Institute, Bethesda, Maryland.
authors.forename: Markku
authors.initials: M
authors.lastname: Miettinen
authors.affiliation: Clinical Micro-array Core, University of California, Los Angeles, California.
authors.forename: Xinmin
authors.initials: X
authors.lastname: Li
authors.affiliation: Molecular Pharmacology Section, Genitourinary Malignancies Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland.
authors.forename: Cody J
authors.initials: CJ
authors.lastname: Peer
authors.affiliation: Molecular Pharmacology Section, Genitourinary Malignancies Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland.
authors.forename: Tristan
authors.initials: T
authors.lastname: Sissung
authors.affiliation: Molecular Pharmacology Section, Genitourinary Malignancies Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland.
authors.forename: William D
authors.initials: WD
authors.lastname: Figg
authors.affiliation: Division of Thoracic Surgery, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Assunta
authors.initials: A
authors.lastname: De Rienzo
authors.affiliation: Division of Thoracic Surgery, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Raphael
authors.initials: R
authors.lastname: Bueno
authors.affiliation: Thoracic Epigenetics Section, Thoracic and GI Oncology Branch, National Cancer Institute, Bethesda, Maryland. david.schrump@nih.gov.
authors.forename: David S
authors.initials: DS
authors.lastname: Schrump
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D014408:Biomarkers, Tumor / Q000096:biosynthesis* / Q000235:genetics; D049109:Cell Proliferation / Q000187:drug effects; D016922:Cellular Senescence / Q000187:drug effects; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D008654:Mesothelioma / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D000086002:Mesothelioma, Malignant; D051379:Mice; D008875:Middle Aged; D010997:Pleural Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D008926:Plicamycin / Q000008:administration & dosage; D012333:RNA, Messenger / Q000096:biosynthesis; D016329:Sp1 Transcription Factor / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis* / Q000235:genetics; D023041:Xenograft Model Antitumor Assays
chemical_list: D014408:Biomarkers, Tumor; D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; C108209:SP1 protein, human; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D008926:Plicamycin