Background/Aims: Biliary tract cancers (BTC) are poor prognostic malignancies with few treatment options. PIK kinase signaling pathway hyperactivation is common in malignancy but the rate in BTC is unknown. As a key signalling mediator, mTOR is an attractive target. Responses to mTOR inhibitors have been seen in other tumours with pathway dysregulation. In BTC, promising in vitro data has been reported with the mTOR inhibitor Everolimus and we have completed the Phase II Radichol trial of everolimus in advanced BTC. Our in vitro study aims to evaluate a panel of BTC cell lines for sensitivity to Everolimus with correlation to mutational activation of the PI3K pathway and other biochemical readouts of activity

Methods: A panel of 21 BTC cell lines have been assembled and treated with Everolimus. Effects on cell growth have been determined by MTS assay. Mutation status of PIK3Ca, Kras and other proto-oncogenes have been evaluated and correlated with drug sensitivity. Basal and post-treatment activation status of the mTOR pathway has been measured and comparisons made between everolimus-sensitive and -resistant cell lines. In vitro results will be supported by analysis of the Radichol study.

Results: 21 treated BTC cell lines have shown a spectrum of sensitivity. 23.8% (n=5) had Kras mutations, one with a co-existing PIK3Ca mutation. Kras-mutant cell lines were resistant to everolimus (p=0.03). Decreased p-4EBP1 expression was seen in sensitive versus resistant lines. This study is ongoing with further results to follow. These results will be correlated with mutation and activation status of Radichol trial tumour samples along with patients’ best outcome.

Conclusions: Novel treatments for BTC are urgently needed and Everolimus is a promising new option. We have identified two potential predictive biomarkers for patients with this disease who may benefit from everolimus treatment and which may guide patient selection in further clinical trials.