Abstract 4324: Axl receptor tyrosine kinase expression regulates tumor cell invasion and migration in colorectal cancer
Authors: Dunne Philip , Schaeybroeck Sandra Van , Kalimutho Murugan , Johnston Patrick 
Published: August 2012

Abstract
Background Colorectal cancer (CRC) is the third most common cancer in the UK with around 80% of patients undergoing surgery followed by adjuvant chemotherapy treatment. Among patients with clinicopathologically defined poor stage II and stage III CRC, there are subsets of patients who will not benefit from adjuvant 5-FU or 5-FU/oxaliplatin treatment. In fact, there is preclinical evidence to suggest that some of these patients may actually do worse when treated with adjuvant chemotherapy. The aim of this study was to develop in vitro adjuvant colon cancer models with the ultimate goal to identify novel treatment strategies for early stage CRC. Method Progressively invasive populations from parental HCT116 were generated using invasion chambers. Analysis of migration and invasion was carried out using the XCELLigence system, protein activity/expression using receptor tyrosine kinase array (RTK) and Western blotting, colony forming ability was assessed by survival assays and drug sensitivity using MTT assay and Flow cytometry. Results Six sublines of HCT116 cells were initially generated (I1-6) which displayed an increasing invasive/migratory phenotype compared to the parental cell line. At the molecular level, we found increases in basal activity of a number of RTK in the invasive sublines, such as Axl (a phenomenon which is characterized with a more aggressive nature in cancers) and also in other kinases such as ERK1/2, Akt and STAT3. Decreased activation of the EGFR and HER2 receptors was also noted in the invasive cell lines. In addition, exposure to sub-lethal 5-FU(IC20) doses resulted in significant increases in migration in these cell line models. Silencing of Axl resulted in significant decreases in migration of the invasive subpopulations even in the presence of 5-FU. Colony forming assays highlighted an increased ability to form colonies in the invasive sub-populations which also displayed drug resistance to both 5-FU and Oxaliplatin. The generation of invasive cell lines was also carried out in a number of other cell lines which confirmed that an increase in Axl expression could increase the migratory phenotype regardless of the genetic background of the cell and also that the results obtained are not an artefact of the cell line we have used. Conclusion Using our in-house developed in vitro preclinical cell line model we have begun to characterise the changes which tumour cells appear to go through during the transition to an invasive phenotype. We have highlighted Axl as a potential target for inhibition in early stage colorectal cancer as increases in total Axl protein levels correlate well with increases in invasive capacity in our models and silencing of the protein expression by siRNA results in ablation of the invasive potential in our model and also in a panel of CRC cell lines. Combination of an Axl small molecule inhibitor could potentially be a novel treatment strategy for early stage CRC.
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 4324. doi:1538-7445.AM2012-4324