@article{TEXTUAL,
      recid = {10511},
      author = {Catenacci, Daniel V. T. and Liao, Wei-Li and Thyparambil,  Sheeno and Henderson, Les and Xu, Peng and Zhao, Lei and  Rambo, Brittany and Hart, John and Xiao, Shu-Yuan and  Bengali, Kathleen and Uzzell, Jamar and Darfler, Marlene  and Krizman, David B. and Cecchi, Fabiola and Bottaro,  Donald P. and Karrison, Theodore and Veenstra, Timothy D.  and Hembrough, Todd},
      title = {Absolute Quantitation of Met Using Mass Spectrometry for  Clinical Application: Assay Precision, Stability, and  Correlation with &amp;lt;i&amp;gt;MET&amp;lt;/i&amp;gt; Gene Amplification  in FFPE Tumor Tissue},
      journal = {PLOS ONE},
      address = {2014-07-01},
      number = {TEXTUAL},
      abstract = {&lt;p&gt;Background: Overexpression of Met tyrosine kinase  receptor is associated with poor prognosis. Overexpression,  and particularly &lt;em&gt;MET&lt;/em&gt; amplification, are predictive  of response to Met-specific therapy in preclinical models.  Immunohistochemistry (IHC) of formalin-fixed  paraffin-embedded (FFPE) tissues is currently used to  select for ‘high Met’ expressing tumors for Met inhibitor  trials. IHC suffers from antibody non-specificity, lack of  quantitative resolution, and, when quantifying multiple  proteins, inefficient use of scarce tissue.&lt;/p&gt;&lt;p&gt;Methods:  After describing the development of the  Liquid-Tissue-Selected Reaction Monitoring-mass  spectrometry (LT-SRM-MS) Met assay, we evaluated the  expression level of Met in 130 FFPE gastroesophageal cancer  (GEC) tissues. We assessed the correlation of SRM Met  expression to IHC and mean &lt;em&gt;MET&lt;/em&gt; gene copy number  (GCN)/nucleus or &lt;em&gt;MET/CEP7 ratio&lt;/em&gt; by fluorescence in  situ hybridization (FISH).&lt;/p&gt;&lt;p&gt;Results: Proteomic mapping  of recombinant Met identified  &lt;sup&gt;418&lt;/sup&gt;TEFTTALQR&lt;sup&gt;426&lt;/sup&gt; as the optimal SRM  peptide. Limits of detection (LOD) and quantitation (LOQ)  for this peptide were 150 and 200 amol/µg tumor protein,  respectively. The assay demonstrated excellent precision  and temporal stability of measurements in serial sections  analyzed one year apart. Expression levels of 130 GEC  tissues ranged (&lt;150 amol/µg to 4669.5 amol/µg. High  correlation was observed between SRM Met expression and  both &lt;em&gt;MET&lt;/em&gt; GCN and &lt;em&gt;MET/CEP7&lt;/em&gt; ratio as  determined by FISH (n = 30; R&lt;sup&gt;2&lt;/sup&gt; = 0.898). IHC did  not correlate well with SRM (n = 44; R&lt;sup&gt;2&lt;/sup&gt; = 0.537)  nor FISH GCN (n = 31; R&lt;sup&gt;2&lt;/sup&gt; = 0.509). A Met SRM  level of ≥1500 amol/µg was 100% sensitive (95% CI 0.69–1)  and 100% specific (95% CI 0.92–1) for &lt;em&gt;MET&lt;/em&gt;  amplification.&lt;/p&gt;&lt;p&gt;Conclusions: The Met SRM assay  measured the absolute Met levels in clinical tissues with  high precision. Compared to IHC, SRM provided a  quantitative and linear measurement of Met expression,  reliably distinguishing between non-amplified and amplified  &lt;em&gt;MET&lt;/em&gt; tumors. These results demonstrate a novel  clinical tool for efficient tumor expression profiling,  potentially leading to better informed therapeutic  decisions for patients with GEC.&lt;/p&gt;},
      url = {http://knowledge.uchicago.edu/record/10511},
}