title: A label-free mass spectrometry method for relative quantitation of β-tubulin isotype expression in human tumor tissue.
abstract: OBJECTIVE
  Quantitation of β-tubulin isotype expression in taxane resistant human tumor tissue has been difficult to achieve because of the limited availability of validated antibodies. Here we present a label-free MS method to quantitate relative expression levels of β-tubulin isotypes.
  
  
  METHODS
  Using isotype-specific reporter peptides, we determined relative β-tubulin isotype expression levels in human lung tumor tissue.
  
  
  RESULTS
  Four reporter peptides were chosen to quantitate the βI/βII, βIV, βIII, and βV tubulin isotypes. These peptides were validated using human cancer cell lines. The label-free method was then used to determine β-tubulin isotype expression in nine human lung tumor samples, which had been described as high or low βIII-tubulin expressing using immunohistochemistry. It was found that βI/βII (accounting for 18.7-65.7% of total β-tubulin) and βIVa/βIVb (26.3-79.1%) were the most abundant isotypes and that the βIII (0-8.9%) and βV (1.0-10.4%) were less abundant in the tissue. We also categorized the samples as high or low βIII-tubulin expressing.
  
  
  CONCLUSIONS
  With this method we can determine the relative expression levels of β-tubulin isotypes in human tumor tissue. This method will facilitate studies assessing the use of tubulin isotypes as biomarkers of taxane resistance.
authors.affiliation: Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
authors.forename: Leah M
authors.initials: LM
authors.lastname: Miller
authors.forename: Chia-Ping
authors.initials: CP
authors.lastname: Huang Yang
authors.forename: Hui
authors.initials: H
authors.lastname: Xiao
authors.forename: Sylvie
authors.initials: S
authors.lastname: Isaac
authors.forename: Pascal
authors.initials: P
authors.lastname: Sève
authors.forename: Charles
authors.initials: C
authors.lastname: Dumontet
authors.forename: Susan
authors.initials: S
authors.lastname: Band Horwitz
authors.forename: Ruth
authors.initials: R
authors.lastname: Hogue Angeletti
mesh_terms: D000595:Amino Acid Sequence; D001952:Bridged-Ring Compounds / Q000494:pharmacology; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D006801:Humans; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000032:analysis / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D043823:Taxoids / Q000494:pharmacology; D014357:Trypsin / Q000378:metabolism; D014404:Tubulin / Q000032:analysis* / Q000378:metabolism
chemical_list: D001952:Bridged-Ring Compounds; D020033:Protein Isoforms; D043823:Taxoids; D014404:Tubulin; C080625:taxane; D014357:Trypsin