title: Loss of mesothelin expression by mesothelioma cells grown in vitro determines sensitivity to anti-mesothelin immunotoxin SS1P.
abstract: OBJECTIVE
  To determine if early passage tumor cells obtained from patients with mesothelioma continue to express the tumor differentiation antigen mesothelin and their sensitivity to the anti-mesothelin immunotoxin SS1P.
  
  
  METHODS
  Cell cultures were established from ascites or pleural effusion of 6 peritoneal and 3 pleural mesothelioma patients, respectively. These cells were evaluated for mesothelin expression by immunohistochemistry and flow cytometry.
  
  
  RESULTS
  Although mesothelin was highly expressed in tumor biopsies of all patients, only 3 out of 9 malignant effusions from these patients when grown in short-term culture showed strong mesothelin positivity by IHC. By flow cytometry, the number of mesothelin sites per cell was variable ranging from 580 to 210,000 sites/cell. Cells with strong mesothelin expression by IHC and increased number of mesothelin sites/cell were sensitive to SS1P.
  
  
  CONCLUSIONS
  Most mesothelioma tumors loose mesothelin when grown in vitro and the sensitivity of these cells to SS1P is dependent on the number of mesothelin sites/cell.
authors.affiliation: Laboratory of Molecular Biology, National Cancer Institute, 37 Convent Drive, Room 5116, Bethesda, MD 20892-4264, USA.
authors.forename: Jingli
authors.initials: J
authors.lastname: Zhang
authors.forename: Shuo
authors.initials: S
authors.lastname: Qiu
authors.forename: Yujian
authors.initials: Y
authors.lastname: Zhang
authors.forename: Maria
authors.initials: M
authors.lastname: Merino
authors.forename: Patricia
authors.initials: P
authors.lastname: Fetsch
authors.forename: Itzhak
authors.initials: I
authors.lastname: Avital
authors.forename: Armando
authors.initials: A
authors.lastname: Filie
authors.forename: Ira
authors.initials: I
authors.lastname: Pastan
authors.forename: Raffit
authors.initials: R
authors.lastname: Hassan
mesh_terms: D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology*; D001201:Ascites / Q000473:pathology; D005260:Female; D005434:Flow Cytometry; D058851:GPI-Linked Proteins / Q000096:biosynthesis / Q000172:deficiency* / Q000276:immunology; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D000090204:Mesothelin; D008654:Mesothelioma / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D008875:Middle Aged; D010534:Peritoneal Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D016066:Pleural Effusion, Malignant / Q000473:pathology; D010997:Pleural Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D014407:Tumor Cells, Cultured; D055815:Young Adult
chemical_list: D000911:Antibodies, Monoclonal; D058851:GPI-Linked Proteins; C474515:SS1(dsFv)PE38; D000090204:Mesothelin