K-Ras mutation and amplification status is predictive of resistance and high basal pAKT is predictive of sensitivity to everolimus in biliary tract cancer cell lines.

Yvonne Yeung,Andrew M Scott,Fiona Chionh,David K Lau,Mehrdad Nikfarjam,Niall C Tebbutt,Hoanh Tran,John M Mariadason,Andrew J Weickhardt,Janson W T Tse

doi:10.1002/1878-0261.12078

Yvonne Yeung, Andrew M Scott + Show 8 more

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https://doi.org/10.1002/1878-0261.12078

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Abstract

Advanced biliary tract cancer (BTC) has a poor prognosis and limited treatment options. The PI3K/Akt/mTOR signalling pathway is hyperactivated in a subset of BTCs, and clinical activity of the mTOR inhibitor everolimus has been observed in some patients with BTC. The goal of this study was to identify biomarkers predictive of everolimus response. Twenty BTC cell lines were assessed for everolimus sensitivity with a spectrum of growth inhibitory responses observed. Molecular biomarkers of sensitivity and resistance were identified by interrogation of the activation status of the Ras/MAPK and PI3K/Akt/mTOR pathways. K‐Ras mutations and/or amplifications were identified in 45% of cell lines and were associated with resistance to everolimus. Activating mutations in PIK3CA or loss of PTEN was not predictive of everolimus response; however, high basal levels of pAKT were associated with sensitivity, independent of Ras/MAPK pathway activation status. Notably, everolimus inhibited mTOR signalling to a similar extent in sensitive and resistant cell lines, suggesting that relative dependence on the mTOR pathway rather than the magnitude of pathway inhibition determines everolimus response. Consistent with the known limitations of rapalogs, everolimus induced feedback‐mediated activation of AKT in BTC cell lines, which could be overcome by cotreatment with an AKT inhibitor or ATP‐competitive mTORC1/mTORC2 inhibitors. However, both approaches failed to induce greater apoptosis compared to everolimus, and mTORC1/mTORC2 kinase inhibitors induced compensatory activation of pERK, identifying an inherent limitation of these agents in BTC cell lines. These findings suggest that future trials of everolimus in BTC would benefit from preselecting patients based on their K‐Ras and PI3K/mTOR pathway activation status. The study also identifies strategies for enhancing inhibition of the PI3K/mTOR pathway in BTC cell lines.

Highlights

Biliary tract cancers (BTCs) are a heterogeneous group of anatomically distinct adenocarcinomas, which include intra- and extrahepatic cholangiocarcinoma and gallbladder cancer that are extremely challenging to diagnose and treat
To characterize the response of BTC cell lines to everolimus, each of 20 BTC cell lines was treated with a range of everolimus concentrations (0.1– 100 nM), and the effect on cell proliferation was assessed after 72 h using the MTS assay
As we had established that Ras/mitogen-activated protein kinase (MAPK) pathway mutations conferred resistance to everolimus, we examined the impact of activating mutations in PIK3CA or PTEN loss on everolimus response in the K-Ras WT subset

Summary

Introduction

Biliary tract cancers (BTCs) are a heterogeneous group of anatomically distinct adenocarcinomas, which include intra- and extrahepatic cholangiocarcinoma and gallbladder cancer that are extremely challenging to diagnose and treat. The incidence of the disease varies around the world, with highest rates in northeastern Thailand and neighbouring Laos and Cambodia where liver fluke infestations (Opisthorchis viverrini) are endemic (Charbel and Al-Kawas, 2011; Geynisman and Catenacci, 2012). In the United States, there are approximately 12 000 new cases of BTC annually, with the majority (80–90%) presenting with advanced disease (Charbel and Al-Kawas, 2011; Hezel et al, 2010). The incidence of BTC, intrahepatic cholangiocarcinoma, is increasing in the Western world for reasons that are presently unknown (Hezel et al, 2010). There is an urgent need for new treatments for this disease

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