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Mass-spectrometry-based quantitation of Her2 in gastroesophageal tumor tissue: comparison to IHC and FISH

Cited 32 time in Web of Science Cited 34 time in Scopus

Catenacci, Daniel V. T.; Liao, Wei-Li; Zhao, Lei; Whitcomb, Emma; Henderson, Les; O'Day, Emily; Xu, Peng; Thyparambil, Sheeno; Krizman, David; Bengali, Kathleen; Uzzell, Jamar; Darfler, Marlene; Cecchi, Fabiola; Blackler, Adele; Bang, Yung-Jue; Hart, John; Xiao, Shu-Yuan; Lee, Sang Mee; Burrows, Jon; Hembrough, Todd

Issue Date
Springer Verlag
Gastric Cancer, Vol.19 No.4, pp.1066-1079
Trastuzumab has shown a survival benefit in cases of Her2-positive gastroesophageal cancer (GEC). Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) currently determine eligibility for trastuzumab-based therapy. However, these low-throughput assays often produce discordant or equivocal results. We developed a targeted proteomic assay based on selected reaction monitoring mass spectrometry (SRM-MS) and quantified levels (amol/mu g) of Her2-SRM protein in cell lines (n = 27) and GEC tissues (n = 139). We compared Her2-SRM protein expression with IHC/FISH, seeking to determine optimal SRM protein expression cutoffs in order to identify HER2 gene amplification. After demonstrating assay development, precision, and stability, Her2-SRM protein measurement was observed to be highly concordant with the HER2/CEP17 ratio, particularly in a multivariate regression model adjusted for SRM expression of the covariates Met, Egfr, Her3, and HER2 heterogeneity, as well as their interactions (cell lines r (2) = 0.9842; FFPE r (2) = 0.7643). In GEC tissues, Her2-SRM protein was detected at any level in 71.2 % of cases. ROC curves demonstrated that Her2-SRM protein levels have a high specificity (100 %) at an upper-level cutoff of > 750 amol/A mu g and sensitivity of 75 % at a lower-level cutoff of < 450 amol/mu g for identifying HER2 FISH-amplified tumors. An "equivocal zone" of 450-750 amol/A mu g of Her2-SRM protein was analogous to IHC2+ but represented fewer cases (9-16 % of cases versus 36-41 %). Compared to IHC, targeted SRM-Her2 proteomics provided more objective and quantitative Her2 expression with excellent HER2/CEP17 FISH correlation and fewer equivocal cases. Along with its multiplex capability for other relevant oncoproteins, these results demonstrate a refined HER2 protein expression assay for clinical application.
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  • College of Medicine
  • Department of Medicine
Research Area Clinical Medicine


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