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M.B. Schabath

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    MO15 - Novel Genes and Pathways (ID 89)

    • Event: WCLC 2013
    • Type: Mini Oral Abstract Session
    • Track: Biology
    • Presentations: 1
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      MO15.01 - Pathway activation mapping of KRAS wild type and mutated adenocarcinomas of the lung: new implications for patient stratification for MAP kinase pathway inhibition (ID 2705)

      16:15 - 17:45  |  Author(s): M.B. Schabath

      • Abstract
      • Presentation
      • Slides

      KRAS proto-oncogene is one of the most frequent mutated genes in Non-Small Cell Lung Cancer (NSCLC) with greater incidence among adenocarcinomas (AD). While the clinical importance of KRAS mutation as a negative predictor for anti-EGFR therapy is not clearly understood in NSCLCs, selection of targeted therapies for KRAS mutated (MUT) patients has often focused on the inhibition of its direct downstream effectors. The aim of this study was to explore the impact of the KRAS status on the cellular signaling network of ADs of the lung harboring different KRAS mutations with a focus on ERK signaling architecture.

      A total of 58 AD samples were collected from chemo-naïve patients at the H. Lee Moffitt Cancer Center & Research Institute (Tampa, FL) and at S. Maria della Misericordia Hospital (Perugia, Italy). Twenty-four tumors were KRAS wild type (WT) and 34 were KRAS MUT (G12C n=18, G12V n=9, G13D n=3 and G12D n=4, respectively). All samples were subjected to laser capture microdissection and reverse phase protein microarray to quantitatively evaluate the activation status of the MAP Kinase signaling network.

      Statistical analysis of signaling protein activation based on KRAS status revealed an overall increase in activation level of the MAPK signaling network in the KRAS MUT tumors compared to tumors expressing KRAS WT: ERK 1/2 (T202/Y204), Elk-1 (S383), p90RSK (S380), Smad2 (S245/250/255) and p70S6K (p<0.01; p<0.01; p<0.01, p=0.04 and p<0.01 respectively). Nevertheless, 6 KRAS WT patients (25%) showed activation of ERK greater than the median of the entire population and an overall MAPK signaling activation comparable to tumors harboring KRAS MUT. Eleven of the KRAS MUT tumors (32%) had ERK activation lower than the median of the population as a whole. Interestingly a high activation level of Estrogen Receptor alpha (ERα) (S118) was detected in the KRAS MUT tumors compared to the KRAS WT one (p=0.02). Moreover the nonparametric test performed to establish the correlation of activated ERK 1/2, Raf, B-Raf, C-Raf and Mek 1/2 with the expression/activation levels of the 152 endpoints analyzed in this study, revealed the activation of distinct pathways in the KRAS MUT tumors when compared to KRAS WT tumors. Significant correlations were detected with Akt, KRAS, their downstream substrates and with several receptor tyrosine kinases (p<0.0003).

      Our results suggest that MAPK signaling activation was clearly observed in KRAS MUT tumors. However, the heterogeneity in the activation level of MAPK downstream substrates within KRAS MUT and WT tumors suggests that selection of patients for MAPK targeting might benefit from the evaluation not only of the mutation itself, but also from a direct analysis of the MAPK protein network architecture. In particular the role played by ERα in KRAS MUT tumors deserves further investigations as a possible novel therapeutic target in KRAS MUT adenocarcinomas of the lung.

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