Abstract 5365: Molecular and pharmacological (EGFRi, MEKi) characterisation of a colorectal cancer (CRC) cell line panel to evaluate cellular phenotype and efficacy of targeted therapies in CRC

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Abstract A broad range of targeted agents are in early development for treatment of solid tumours. It is important that patients receive treatments which are tailored to work optimally based on their individual tumour biology. Retrospective analysis of clinical data for the EGFR tyrosine kinase inhibitor, Iressa, in lung cancer demonstrated cell line panels can provide a platform to direct targeted therapies towards specific patient subpopulations. In order to evaluate targeted agents in colorectal cancer we have characterized a panel of 49 colorectal tumour cell lines derived from Dukes stage A-D of CRC for commonly occurring mutations (KRas, BRAF, PI3Ka, PTEN), microsatellite instability, gene copy number alterations (Agilent 244K ArrayCGH), mRNA expression (Affymetrics HG_U133_plus_2) and miRNA expression (TLDA – 177 miRNAs). These data have been used to characterize the differentiation status of the cell lines and to link to compound activity. We have probed the anti-proliferative activity of compounds from several growth factor pathways, EGFR, RAS/MEK and PI3K to evaluate pathway dependence and linkage to molecular data. The greatest activity of the EGFR TKI inhibitor was in Ras, Raf, PTEN, PI3K wild type (quadruple negative (QN)) CRC lines, in agreement with clinical data for EGFR antibodies. However, of the 9 QN lines profiled, only 4 were hypersensitive (GI50 <0.5uM), the hypersensitive lines had an epithelial phenotype (E-cadherin mRNA, miR200c & B-Cat protein positive; vimentin mRNA negative). In contrast the QN lines that did not respond to EGFR inhibition had either a mesenchymal (E-cadherin mRNA, miR200c, B-Catenin protein negative, vimentin positive) or an intermediate phenotype (E-cadherin mRNA, miR200c & B-Cat protein low; vimentin negative). KRAS and BRAF mutant cell lines were relatively resistant to EGFRi compared to QN cell lines (p = 0.009 and 0.06 respectively), with the exception of two lines with G13D KRAS mutations which had GI50s of 0.3 and 1.8uM. Interestingly, the epithelial QN lines were co-sensitive to EGFR, MEK and PI3K inhibitors. In contrast the mesenchymal QN lines were relatively insensitive to the kinase inhibitors used. The QN lines with an intermediate phenotype did not respond to EGFR or MEKi but did respond to PI3K inhibition. In conclusion, the data suggests that both mutation status and cellular differentiation status contribute to the response to targeted agents. Through profiling the anti-proliferative activity of inhibitors from across a range of pathways co-dependencies of kinase targets were revealed as well as anti-correlations which indicate potential combination strategies. 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 5365. doi:10.1158/1538-7445.AM2011-5365