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Background: Trastuzumab showed survival benefit for Her2-positive gastroesophageal cancers (GEC). Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) currently determine eligibility for trastuzumab-based therapy. However, both assays are low throughput with various limitations. Methods: We developed a selected reaction monitoring mass spectrometric (SRM-MS) assay and quantified levels (amol/ug) of Her2-SRM in cell lines (n=27) and GEC tissues (n=139). We compared Her2-SRM expression with IHC/FISH, seeking to determine optimal SRM expression cut-offs to identify HER2 amplification. Results: After demonstrating assay development, precision, and stability, Her2-SRM measurement was observed to be highly concordant with HER2/CEP17 ratio, particularly in a multivariate regression model adjusted for SRM-expression of Met, Egfr, Her3, and HER2-heterogeneity covariates, and their interactions (cell lines r2=0.9842; FFPE r2=0.7643). In GEC tissues, Her2-SRM was detected in 71.2% of cases, and 12.3% were identified as ‘HER2+’. ROC curves demonstrated HER2-SRM levels to have high specificity (100%) at an upper-level cut-off of >750 amol/µg and sensitivity (75%) at lower-level cut-off of

Background: Current cancer treatment regimens rely on the use of chemotherapy agents that inhibit DNA replication and repair machinery. Several proteins are involved in this mechanism, such as TOPO1, TOPO2A, RRM1, FR-alpha and hENT1. The expression levels and activities of these proteins can greatly affect the success of chemotherapy; however current treatment indications are not based on tumor expression levels of these proteins. We have developed a quantitative, multiplexed ChemoPlex SRM method to evaluate these markers in a host of solid tumors from a limited amount of FFPE biopsy tissue using our Liquid Tissue®-SRM (LT-SRM) platform. Use of this method will enable a physician to understand individual tumor molecular machinery and ultimately could lead to individualized treatment decisions leading to better patient care. Methods: We used trypsin digestion mapping of recombinant proteins to identify optimal quantitative peptides for the ChemoPlex SRM assay. Standard curves were generated to determine the LOD, LOQ, accuracy, precision and linearity of the assay. The assay was pre-clinically validated on 14 cell lines with known expression levels of these Chemo-targets, and the assay was then run on microdissected archived FFPE human tissue samples from lung, gastro-esophageal cancer (GEC), breast, liver, colorectal, and ovarian tumors. Results: The peptides chosen for the 5 Chemo-Plex targets had LOD values of 150, 50, 300, 200, and 100 amol (CV Discussion: We describe the development and initial clinical validation of a quantitative proteomic ChemoPlex SRM assay which accurately measures the expression of five chemotherapy targets in FFPE tumor tissue. When multiplexed along with other druggable biomarkers, the ChemoPlex SRM assay will allow more accurate identification of patients that are likely to benefit from the combination of chemotherapy and targeted therapies. Citation Format: Eunkyung An, Wei-Li Liao, Sheeno Thyparambil, Adele Blackler, Jamar Uzzell, Kathleen Bengali, Marlene Darfler, Jon Burrows, Todd Hembrough. Clinical validation of a multiplexed ChemoPlex SRM assay in FFPE human tumor tissue. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 918. doi:10.1158/1538-7445.AM2014-918

The human EGF receptor family (HER's) consists of two clinically validated drug targets (EGFR (HER1) and HER2), and two receptors (HER3 and HER4) which are the subject of intensive preclinical and early clinical investigation. Although drugs inhibiting both EGFR and HER2 show significant antitumor activity in the clinic, the acquisition of resistance is a hallmark of these and other targeted therapies. In the case of both targets, one of the emerging resistance mechanisms is the co-expression of other members of the EGFR superfamily. It was recently shown that HER2 co-expression mediates resistance in EGFR inhibitor (cetuximab) treated head and neck cancer (Sci Transl Med 7(3)99). Similarly, much attention has been paid to HER3 both as a bona fide drug target as well as a resistance mechanism (Oncogene 27, 3944). Finally, HER4, though less well studied may play a role in drug response (Breast Cancer Research 11:R50). We have previously build HER1 and HER2 specific SRM assays. HER3 is usually expressed at much lower levels than EGFR and HER2 (often Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4567. doi:1538-7445.AM2012-4567

Many of the current targeted therapies in oncology target the activity of either receptor tyrosine kinases (Her2, EGFR, IGF1R, cMet, FGFR, PGDFR) or cytoplasmic tyrosine kinases (cSrc, AurA, PI3K, MEK, Raf, Akt). The current slate of clinically useful diagnostic tests measure target expression either directly by immunohistochemistry or indirectly by extrapolation from the level of gene or mRNA expression/amplification. These assays are limited by lack of quantitation, and no assay can directly assess the activation state of the signaling pathway components. The lack of information regarding target activation and downstream signal transduction can be overcome using the Liquid Tissue®-SRM technology platform. This approach enables relative and absolute quantification of multiple proteins and their phosphorylation status directly in formalin fixed tissue. In order to fill this diagnostic ‘gap’ we have used this platform to develop a quantitative multiplexed phospho-target assay format which measures the specific phosphorylation state of many clinically relevant oncogenic kinases (EGFR, cMet, Her3, Erk, cSrc, Mek, Akt, p70S6K) directly in FFPE tumor tissue. This phosphopeptide multiplex assay was initially preclinically validated on the A431 tumor cell line which harbors an amplification of the EGFR gene. These cells were stimulated with a dose range of EGF (50-200ng/ml) or in a time course study (EGF 50ng/ml for 5-30min). Confluent, EGF stimulated cells were then formalin fixed, subjected to Liquid Tissue® processing, and then phospho-enriched using TiO2 magnetic beads. The resulting enriched phosphopeptides were then analyzed by mass spectrometry. This method demonstrated the feasibility, and reproducibility of this method for quantitating EGFR pY1197, EGFRpT693, AKT pS473, p-p70S6K pS447, ERK pT202/pY204. We extended this study by performing phosphoenrichment and mass spectrometric analysis of human tumor xenografts, primary human tumor NSCLC explants and clinical trial tissue from EGFR inhibitor treated NSCLC and colorectal cancer patients. In each case we were able to enrich and measure the phosphorylation of a large set of important oncogenic kinases. Our intention is to develop this diagnostic tool to provide a multiplex assay format in formalin fixed tissue that can be applied from preclinical to clinical studies that will impact both targeted drug development and patient stratification needs in this era of personalized healthcare. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5129. doi:10.1158/1538-7445.AM2011-5129

Background Analysis of key therapeutic targets such as epidermal growth factor receptor (EGFR) in clinical tissue samples is typically done by immunohistochemistry (IHC) and is only subjectively quantitative through a narrow dynamic range. The development of a standardized, highly-sensitive, linear, and quantitative assay for EGFR for use in patient tumor tissue carries high potential for identifying those patients most likely to benefit from EGFR-targeted therapies. Methods A mass spectrometry-based Selected Reaction Monitoring (SRM) assay for the EGFR protein (EGFR-SRM) was developed utilizing the Liquid Tissue®-SRM technology platform. Tissue culture cells (n = 4) were analyzed by enzyme-linked immunosorbent assay (ELISA) to establish quantitative EGFR levels. Matching formalin fixed cultures were analyzed by the EGFR-SRM assay and benchmarked against immunoassay of the non-fixed cultured cells. Xenograft human tumor tissue (n = 10) of non-small cell lung cancer (NSCLC) origin and NSCLC patient tumor tissue samples (n = 23) were microdissected and the EGFR-SRM assay performed on Liquid Tissue lysates prepared from microdissected tissue. Quantitative curves and linear regression curves for correlation between immunoassay and SRM methodology were developed in Excel. Results The assay was developed for quantitation of a single EGFR tryptic peptide for use in FFPE patient tissue with absolute specificity to uniquely distinguish EGFR from all other proteins including the receptor tyrosine kinases, IGF-1R, cMet, Her2, Her3, and Her4. The assay was analytically validated against a collection of tissue culture cell lines where SRM analysis of the formalin fixed cells accurately reflects EGFR protein levels in matching non-formalin fixed cultures as established by ELISA sandwich immunoassay (R2 = 0.9991). The SRM assay was applied to a collection of FFPE NSCLC xenograft tumors where SRM data range from 305amol/μg to 12,860amol/μg and are consistent with EGFR protein levels in these tumors as previously-reported by western blot and SRM analysis of the matched frozen tissue. In addition, the SRM assay was applied to a collection of histologically-characterized FFPE NSCLC patient tumor tissue where EGFR levels were quantitated from not detected (ND) to 670amol/μg. Conclusions This report describes and evaluates the performance of a robust and reproducible SRM assay designed for measuring EGFR directly in FFPE patient tumor tissue with accuracy at extremely low (attomolar) levels. This assay can be used as part of a complementary or companion diagnostic strategy to support novel therapies currently under development and demonstrates the potential to identify candidates for EGFR-inhibitor therapy, predict treatment outcome, and reveal mechanisms of therapeutic resistance.