A NEW EPIDERMAL GROWTH FACTOR RECEPTOR INHIBITOR IN COLON CANCER CELLS

Introduction Members of the Epidermal Growth Factor Receptor (EGFRs) family of receptor tyrosine kinases act as critical mediators of the cellular communication network regulating complex biological processes such as proliferation and differentiation. Since EGFRs signalling is frequently deregulated in several human cancers, interference with EGFR activation and/or intracellular signal transduction pathway represents a promising strategy for the development of novel and selective anticancer therapies. Small molecules inhibitors of EGFR as well as monoclonal antibodies to EGFR are being utilized as anti-cancer therapeutics. In this respect a shikonin-derivative, -hydroxyisovalerylshikonin, exerts a strong, non-ATP-competitive inhibition of EGFR kinase activity, suggesting that it may bind to the ligand binding site [1]. As this compound has little potential as drug candidate because of its poor solubility, we have designed and synthesized a library of derivatives in order to obtain active compounds endowed with more “drug-like” properties. In this study we have tested the anti-tumour activity of FR18, the first compound of this class, by using the HT29 colon adenocarcinoma cell model and by comparing its potency with an anti-EGFR-blocking monoclonal antibody. Materials and Methods HT29 cells were exposed to increasing doses of FR18 or EGFR-blocking antibody and cell cycle distribution was evaluated by flow cytometry. The effects induced on EGFR auto-phosphorylation were tested by means of immunoprecipitation and western blotting, while spectral confocal microscopy was used to investigate EGF-receptor interaction. Results While EGFR-blocking antibody treatment induced growth arrest in G0/G1, FR18 determined an increase of HT29 cells in the G2/M phase and apoptotic cell death. At the receptor level, FR18 determined a remarkable reduction of EGFR activation, associated to the inhibition of the ligand-receptor interaction. In conclusion our data suggest that FR18 selectively induces apoptosis in HT29 cancer cells by interfering with EGFR receptor signalling. Bibliografia 1. Nakaya K. et al., A shikonin derivative, b-hydroxyisovalerylshikonin, is an ATP-non-competitive inhibitor of protein tyrosine kinases. Anticancer Drugs 2003, 14:683-693.