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3613 Background: One-third of colorectal cancer (CRC) recurs following curative surgery and chemotherapy. Accordingly, novel methods are needed to predict recurrence to enable clinical course mitigating strategies. Serial monitoring of plasma by mass spectrometry (MS) and multi-omics modeling (MMO) of CRC relapse chronology provide the framework for liquid biopsy test development to supersede existing imaging modalities such as CT scans according to relapse related pathologies. We hypothesized that plasma MS and MMO analysis of relapse related pathologies can deconvolute high risk stratification for CRC recurrence within the cancer continuum of care pre/post-surgery and/or pre/post adjuvant chemotherapy (ACT). Methods: 189 CRC patients (Stage I-III) underwent one of three treatment modalities: Modality 1 (Surgery followed by ACT), Modality 2 (Surgery only), Modality 3 (Neoadjuvant chemotherapy followed by surgery and ACT). Plasma samples (n = 441) were collected from patients before surgery, 30 days post-op, and every 3 months until death or month 24 whichever came first. The MMO approach was used to analyze biological features encompassing native peptides, proteins, metabolites, lipids, and ceramides. MMO panels were developed comprising the significantly perturbed features as per the treatment modalities. These panels were used to predict relapse from plasma collected pre-op, 30-day post-op or after adjuvant chemotherapy. CEA levels were monitored in parallel. Results: Follow-up data was available for 135 patients (Stage I-III) and 25/135 had evidence of radiological recurrence. Irrespective of the treatment modality, longitudinal follow-up using the MMO panel was able to predict disease recurrence greater than 7 months before clinical progression was confirmed by CT scan. There was no significant correlation between longitudinal CEA levels and recurrence status, hence CEA levels alone did not provide any lead time advantage over the MMO panel or radiological surveillance. Kaplan-Meier (KM) survival analysis revealed that patients that were MMO panel positive had a poor survival irrespective of treatment modalities used: Modality 1 (HR = 6.2, p value = 0.003, test immediately post-surgery and immediately before ACT; HR = 31.6, p value = 0.01, test immediately after ACT); Modality 2 (HR = 11.2; p value = 0.01, test immediately after-surgery); Modality 3 (HR > 40, p value = 0.08, test immediately after neo-ACT and before-surgery; HR > 40, p value = 0.004, test immediately after-surgery). Conclusions: The MMO panel predicts CRC recurrence several months prior to detection by conventional CT scans, thus providing opportunity for alternative therapeutic strategies much earlier in the disease course.

97 Background: The incidence and mortality of early-onset colorectal cancer (EO-CRC) is on the rise. Consequently, there is an urgent unmet need to better understand their unique tumor biology to expand therapeutic options and improve clinical outcomes. Methods: Exploratory Targeted multiplex proteomics (TMP) and targeted 648 gene panel was performed on specimens from 35 patients with resected colon cancer diagnosed at age < = 40 years. TMP panel consisted of 72 proteins involved in differentiation, tumorigenesis, and response to chemotherapy, targeted therapy, and immunotherapy. Clinicopathologic and genomic data were also collected. Results: The median age of diagnosis was 33 years. The cohort included 15 male and 20 female patients. 20 (57%) had left-sided tumors and 6 (17%) had stage IV disease. Notable genomic alterations included mutations in: BRAF V600E (2/35); RAS (15/35); PIK3CA exon 9 or 20 (5/35); and ERBB2 (2/35). One patient exhibited ERBB2 amplification. 9/35 tumors were MSI-H. TMP analysis revealed overexpression of chemotherapy resistance proteins in several patients: ALDH1A1:16/35; ERCC1:1/35; GART:26/35; MDR1:9/35; MGMT:5/35; RRM1:6/35; TUBB3:1/35; TYMS:2/35; XRCC1:11/35. In contrast, some tumors exhibited elevated biomarkers of chemosensitivity: hENT1:8/35; DHFR:12/35; TYMP:15/35; OPRT:8/35; SLFN11:1/35; TLE:11/35; TOPO1:12/35; TOPO2A:1/35. Protein targets of cell signaling pathways were overexpressed in a number of tumors: CAT:16/35; CAV-1: 6/35; CBL:2/35; E-Cadherin: 19/35; HSP90A:16/35; HSP90B:18/35; MET:5/35; NQO1:18/35; paxillin:4/35; SRC:21/35; STAT3:11/35. Regarding EGFR and KRAS, none of the tumors exhibited elevated protein expression level. Furthermore, RAS mutational status did not correlate with the level of EGFR or KRAS protein expression. Antibody drug conjugate biomarkers were observed. HER2 overexpression was noted in one patient who had a confirmed ERBB2 amplification. Regarding immunotherapy targets, PDL-1 protein was not overexpressed in any tumor, whereas MSLN and TROP2 were elevated in 1/35 and 2/35 patients, respectively. Conclusions: TMP analysis of EO-CRC patients revealed marked heterogeneity in the expression of proteins involved in differentiation, tumorigenesis, and response to chemotherapy, targeted therapy, and immunotherapy. Differential protein expression may provide insight into therapeutic vulnerabilities for EO-CRC. Furthermore, the discordance between detected genomic alterations and protein expression levels highlights the complementary nature of genomic sequencing and TMP analysis.

e16098 Background: Human serum proteome and metabolome profiles have been analyzed to explore the molecular changes that occur with aging. We hypothesized that deep phenomic profiling of longitudinal sera would allow the identification of distinct phenomic chronologic patterns as a normal biological clock baseline to study personal aging. We further hypothesized that molecular assessment of this chronologic deviation, due to advance adenoma and early CRC, from the normal reference ageotypes would be instrumental as potential early diagnostics and reveal underlying pathophysiology. Methods: A cohort of 7673 normal, 746 advanced adenoma, 1177 stage I, 103 stage II and 119 stage III blood samples were assembled. Innovative multi-omics approaches, with global and targeted LCMS data production (metabolomics, lipidomics, and 2D proteomics), were applied to deep profile these subjects. Identification of the age-associated molecular patterns in normal subjects, modeled with an elastic net algorithm, established the reference baseline to mirror a biological clock. CRC associated deviation from this chronologically paced multi-omics clock was quantified to screen for early CRCs and explore the underlying pathophysiology. Results: Multiple mProbe aging indices of proteins and metabolites were identified, strongly predicting chronologic age ( P < 0.001, R > 0.90). Significant disruptions from normal molecular patterns were observed in advanced adenoma and early CRCs patients (R < 0.7). Pathway analysis of the proteins/metabolites with deviating patterns revealed both known and new pathways underlying CRC. Unsupervised cluster analysis identified unique aging subgroups among advanced adenoma and different stage CRC patients, indicating unique underlying biology relating to aging with different severities of cancer burdens. Conclusions: Deviations from the meticulously timed phenomic aging patterns may provide utility to allow future early CRC screening. Close examination of the underlying pathophysiology associated with early CRC, relating to ageotypes, not only may improve the sensitivity and specificity of prognostic and diagnostic tests of early CRCs, but also shed new insights into CRC therapeutics.

2555 Background: Glioblastoma (GBM) is an aggressive primary brain tumor with poor prognosis. Treatment at diagnosis is largely confined to surgery, radiation and temozolomide (TMZ) with median progression-free survival (PFS) of 7 months and median overall survival (mOS) of 15 months. GBM tumors recur in most cases and in patients with recurrent GBM, the mOS is 6.2 months. The lack of effective therapies underscores the importance of exploring other agents. We propose that quantitating therapy-associated protein biomarkers can improve treatment personalization for GBM. Methods: 97 FFPE GBM tissues were microdissected and solubilized for mass spectrometry-based proteomic analysis of therapy-associated protein biomarkers in our CLIA certified lab. We quantified protein levels of MGMT, hENT1, RRM1, TOPO1 and EGFR/TUBB3 (antibody target and payload resistance markers, respectively, for anti-EGFR ADCs) simultaneously. The multiplexed assay also quantified additional 24 clinically relevant proteins. Results: 43/57 patients were predicted to respond to TMZ based on undetectable levels of MGMT, confirming wide utility of this agent. 42/97(43%) patients were predicted to have gemcitabine sensitivity based on high expression of the response marker (hENT1 > 100 amol/ug) and low expression of the resistance marker (RRM1 < 700 amol/ug). 11/97(11%) patients expressed TOPO1 > 1350 amol/ug (75th percentile of all indications tested by author’s laboratory), suggesting likely response to irinotecan and topotecan. EGFR expression ranged from < 100 amol/ug to > 25000 amol/ug, including overexpression (> 1500 amol/ug) in 22%(21/97) of cases. While expression of EGFR(81/97, 84%) suggested likely response to anti-EGFR ADC, concurrent expression of TUBB3(78/81) may indicate resistance to several known payloads, such as taxanes and MMAE. Conjugation with another payload that targets sensitivity marker TOPO1 (68% expression) is a likely option. Proteomic analysis also revealed detectable levels of multiple RTKs (FGFR(4), AXL(20), IGF1R(10), MET overexpression(1), and HER2 overexpression(2)), indicating potential response to RTK inhibitors. Exploratory investigation in tumor vs TME using proteomics and metabolomics is ongoing. Conclusions: In this population of GBM patients, proteomic analysis identified protein targets of multiple approved and investigational therapies. Gemcitabine, which crosses the blood-brain barrier, may be considered as a salvage option after TMZ failure. Proteomic quantitation of EGFR and TUBB3 may improve patient selection for EGFR-targeting ADCs.

17 Background: Multiple ADCs are in clinical trials for CRC and the optimal strategy for selecting patients who may benefit from the treatment is evolving. Due to the unique mechanism of ADCs, patient selection should involve screening not only for the presence of the antibody target, but also for markers of resistance or response to the payload. We have built a multiplexed ADC biomarker panel in FFPE tumor tissue that simultaneously quantifies the protein levels of the antibody targets and also the payload markers. Methods: FFPE tumor tissues from 363 CRC patients were microdissected and solubilized for mass spectrometry-based targeted proteomic analysis in our CLIA certified laboratory. We quantified protein levels of EGFR, HER2, HER3, Axl, Mesothelin, FRalpha, Trop2 (antibody targets), tubulin-beta3 and TOPO1 (payload resistance and response markers, respectively) simultaneously. The multiplexed assay also quantified additional 22 clinically relevant proteins. Results: Expression of EGFR(83%), HER2(52%), HER3(21.5%), Axl(3.7%), Mesothelin(26.5%), FRalpha(3.7%), and Trop2(59.8%) may indicate likely response to ADCs. Expression of TUBB3(+) and TOPO1 (>1350amol/µg) in antibody target-positive subset may suggest resistance or response to payloads, such as taxanes and irinotecan, respectively (Table). Previously we identified that HER2 expression >750amol/µg correlated with HER2 positivity. Accordingly, 1.4% (5/355) of CRC patients were HER2 positive, of which 40% (2/5) had TOPO1 expression >1350amol/µg (75th percentile) suggesting that these 2 patients may receive benefit from a HER2/TOPO1 ADC. (+) indicates expression ≥LOQ; (-) indicates expression [Table: see text]

6053Background: Adenoid cystic carcinoma (ACC) is a rare cancer of secretory glands accounting for 10% of salivary gland cancers and 1% of head and neck cancers. ACC rarely responds to chemotherapy...

8574Background: Even with standard platinum doublet therapy, most patients with small-cell lung cancer (SCLC) survive < 1 year. For those with refractory or relapsed disease, second-line, single-ag...

1045 Background: The folate pathway is a critical nucleotide biosynthetic pathway in many tumor cells, and blockade of this pathway with antifolates has demonstrated clinical utility in NSCLC and m...

605 Background: To be eligible for an anti-HER therapy, tumors have to be HER2-positive as determined by IHC or in situ hybridization (ISH) analyses. Although gene amplification is generally consid...

4050 Background: Trastuzumab-based chemotherapy is standard treatment for HER2-positive advanced gastric cancer (AGC). Although increased HER2 gene amplification by fluorescent in situ hybridizatio...

82 Background: HER2+ GEC derived benefit from trastuzumab. Her2 IHC is semi-quantitative, subjective, and sensitive to antigen instability; HER2 FISH is laborious, expensive, and subjective. False positivity/negativity have been described. Also, these are low throughput assays; there is known molecular heterogeneity, with several putative biomarkers, and only scarce tissue to assess for each. We sought to evaluate the association of Her2 MS expression with HER2 FISH, along with other markers within the ‘GEC-plex’. Methods: We utilized a previously described unique Her2 peptide and quantification method (Hembrough et al J Clin Oncol 32,2014(suppl 3;abstr17)). The assay was run on 27 cell lines, in parallel with HER2:CEP17 FISH. Her2 expression thresholds were established for HER2 amplification using ROC curves. We adjusted for Her3, Egfr, and Met MS expression levels and sample HER2:CEP17 ratio heterogeneity in a multiple linear regression model. The model/cut-offs were then validated prospectively on GEC tissues (n=142). Results: Her2 MS on cell lines revealed concordance with FISH (HER2:CEP17) ratio (R2=0.75), which improved by adjusting for Her3 MS, Egfr MS, Met MS and HER2:CEP17 heterogeneity (R2>0.98), with significant interactions. IHC correlation with HER2:CEP17 ratio was poor (R2=0.12). A wide range of expression was noted within IHC3+ patients (150 amol/ug) was seen in 72.9% (102/142) of tissues (range 750 amol/ug - all were HER2 FISH amplified. 6/142 (4%) cases

649 Background: There is evidence that increased absolute levels of the HER2 receptor in breast cancer positively correlates with a clinical benefit from anti-HER2 therapies. The current method of HER2 evaluation, immunohistochemistry (IHC), does not allow for absolute HER2 quantification and is prone to false-positives. Thus, a significant portion of patients classified as HER2-positive actually express low levels of the receptor. We quantitated absolute levels of HER2 using a mass spectrometry-based assay and correlated expression levels with the anti-HER2 therapy benefit. Methods: Formalin-fixed, paraffin-embedded (FFPE) tumor sections were microdissected and proteins were solubilized and digested by trypsin in Liquid Tissue buffer. After digestion, internal standards were added and absolute quantitation for multiple proteins was performed using selected reaction monitoring (SRM) mass spectrometry. Results: 26 HER2-positive (IHC 3+) breast cancer samples from patients treated with anti-HER2 therapy wer...

16 Background: Overexpression of MET in gastroesophageal cancer (GEC) is associated with poor prognosis and potentially predictive of anti-MET therapeutic benefit. IHC has been the method chosen to quantify MET expression to date. However, IHC is semi-quantitative, suffers from cross-reactivity, and is low throughput. Moreover, MET IHC is hampered by antigenic instability in FFPE sections, limiting its utility to recently cut FFPE sections. Increasing recognition of the importance of other biomarkers in GEC suggests that ‘economic’ testing of scarce samples will be required. We sought to develop a MET quantitative assay within our ‘GEC-plex’ Liquid-Tissue-selected reaction monitoring (LT-SRM) MS test. Methods: We used trypsin digestion mapping of rMET to identify unique peptides for MS assay development. The assay was pre-clinically validated in 5 cell lines, where electrochemiluminescence (ECL) immunoassay measurement of MET was also performed. To assess the MET MS assay stability from archival FFPE sections, freshly cut FFPE tissue sections were immediately microdissected, processed and analyzed, while adjacent sections were processed and analyzed one year after cutting, to compare temporal quantification from the same FFPE samples (n=33). MET expression was assessed in GEC cases (n=121), and compared to IHC and FISH in select cases. Results: Tryptic digestion mapping of rMET showed that peptide TEFTTALQR was optimal for MET quantification. The LLOD for this peptide was 150 amol with CV2=0.99). The MET MS assay demonstrated temporal stability of serial sections cut from 33 samples analyzed one year apart: CVs2=0.75. Analysis of 121 GEC FFPE tissues showed a broad range of MET expression levels (

e19057 Background: The diagnosis of adenocarcinoma (ADC) vs. squamous cell carcinoma (SCC) in NSCLC is critical since new therapies (e.g. pemetrexed) are restricted to non-squamous NSCLC. Most diagnoses are made based on histopathology, though IHC is often performed as well. Since IHC is not quantitative, interpretation of intensity is subjective, and reproducibility can be problematic. Using the Liquid Tissue-SRM mass spectrometry (MS) platform, we have developed a quantitative, multiplexed clinical diagnostic assay to measure the adeno/squamous markers TTF-1/CK7 (ADC) and K5 and p63/40 (SCC) in FFPE tissue. This proteomic assay is epitope independent, and highly reproducible. Methods: Recombinant K5, K7, TTF-1 and p63/p40, were subjected to trypsin digestion mapping to identify peptides for MS analysis. Heavy isotope labeled peptides were synthesized as positive control peptides for quantitation. The multiplexed assay was technically validated on cell lines, and human tumor tissues. Results: ADC/SCC proteomic analysis was performed on a training set of 39 NSCLC tissues from U. of Chicago (20 ADC and 19 SCC). Principal Component Analysis was used to define optimal quantitative cutoffs for each of the four markers for the two tumor subtypes. The ADC diagnosis was unequivocal for all 20 ADC samples, however within the 19 SCC’s, one sample appeared to be ADC and two samples had markers for both ADC and SCC. Proteomic analysis of a test set of 194 NSCLC tumors (98 ADC and 98 SCC based on pathology reports) from MD Anderson Cancer Center was consistent with the observations in the training set. 93/98 ADC cases were confirmed by proteomic analysis, four ADC cases showed mixed or SCC phenotypes. Proteomic analysis confirmed 58/98 SCC cases but identified 27 cases as mixed ADC SCC or ADC based on TTF1/K5 expression. Further studies are ongoing to determine the clinical utility of these findings. Conclusions: These data demonstrate that quantitative proteomic analysis can define cut offs for ADC and SCC Biomarkers profiles in NSCLC tumors. These profiles can determine ADC, SCC and mixed phenotypes and provide physicians with accurate information to help them stratify their patients to the right evidence based treatment therapy.

e21068 Background: The human EGF receptor family (HER’s) consists of two clinically validated drug targets (EGFR 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 receptor tyrosine kinases, including members of the EGFR superfamily, cMet and IGF1R. As an example, it was recently shown that HER2 co-expression mediates resistance in cetuximab treated head and neck cancer. Similarly, much attention has been paid to HER3 both as a bona fide drug target and a resistance mechanism. Methods: Using trypsin digestion mapping of recombinant proteins, we identified unique peptide sequences from each of these receptors, and built quantitative mass spectrometric (MS) assays which could be multiplexed into a single MS analysis of 1ug of tumor protein. Assays were preclinically validated on 10 formalin fixed cell lines, and FFPE human NSCLC primary tumor xenografts. Results: The validated multiplex assay was used to measure expression levels of HER1-3, cMET and IGF1R in two cohorts of clinical tumor tissue which had been treated with HER family antagonists. One, a set of gefitinib treated NSCLC tumors (N=15) , and a second, a cohort of advanced breast cancer tissues which had adjuvant treatment with trastuzumab(N=18). Here we present expression patterns for each of the RTKs studied, with the intent to begin to define the relationship between RTK expression and response to either gefitinib or trastuzumab treatment. Conclusions: It is important to not only understand primary mechanisms of tumor growth, but also mechanisms of resistance in patients undergoing targeted therapies. Our Liquid Tissue-SRM promises to be a platform which can deliver extremely high sensitivity, absolute specificity as well as multiplexing capabilities to assess critical oncology targets.

10069 Background: The IGF-1R pathway is activated in many cancer types which has led to clinical development of many IGF1R targeted therapeutics. Multiple clinical trials targeting IGF1R are currently underway, however after initial optimism in NSCLC and Ewing’s sarcoma, several trials have failed to show efficacy or had severe toxicity. Pretreatment quantitation of tumor IGF1R protein expression remains a challenge due to high homology between IGF1R and the insulin receptor. Thus, there is a need for a specific and quantitative clinical assay for IGF1R protein expression. The ability to quantify IGF1R expression and determine signaling pathway activation status directly in formalin-fixed paraffin-embedded (FFPE) patient tissue biopsies should help identify patients most likely to benefit from anti-IGF1R therapies. Methods: We have developed a quantitative IGF1R assay which can be performed directly in FFPE patient tissue. This approach is based on the Liquid Tissue-SRM technology platform which enables r...

e11130 Background: Trastuzumab treatment of Her2+ breast cancer is the benchmark success story for targeted cancer therapy, however, a significant number of patients are either non-responsive or experience disease progression. A novel mechanism of resistance in some patients is the expression of truncated Her2 (p95Her2), formed by proteolytic cleavage of the HER2 molecule. Truncated p95Her2 loses its extracellular trastuzumab binding epitope, but retains a constitutively active kinase domain predicted to be sensitive to kinase inhibitors, like lapatinib and neratinib. At present there are no diagnostic assays for this p95Her2. Methods: Using the Liquid Tissue-SRM (selective reaction monitoring) platform we have developed multiple mass spectrometric assays to quantify specific cytoplasmic or extracellular domain (ECD) peptides from Her2 directly from formalin fixed paraffin embedded (FFPE) clinical tissue. Results: We validated these assays using recombinant human Her2, where we saw equivalent intracellula...

e14117 Background: The epidermal growth factor receptor (EGFR) is the target of antibody therapeutics, with cetuximab approved for use in metastatic colorectal carcinoma (mCRC) among other indications. While KRAS mutation is a negative predictor of cetuximab response, patients with wtKRAS may show low response rates through a number of resistance mechanisms. Co-expression of receptor tyrosine kinases, such as IGF1R or cMet, can confer resistance by providing alternative ways to activate tumor growth pathways. Additionally, current diagnostic assays cannot quantitate receptor or pathway activation in tissue. Characterization of these various resistance mechanisms are critical to maximizing response rates to EGFR targeted therapies. Methods: In order to address these issues, we used mass spectrometry to develop a multiplexed SRM (selective reaction monitoring) assay to measure levels of multiple protein targets on FFPE tumor tissue. These assays are based on the Liquid Tissue-SRM technology platform. This a...