Dual Inhibition of PI3K-AKT-mTOR- and RAF-MEK-ERK-signaling is synergistic in cholangiocarcinoma and reverses acquired resistance to MEK-inhibitors

• Published in: Investigational new drugs Vol. 32; no. 6; pp. 1144 - 1154
• Main Authors: Ewald, Florian, Nörz, Dominik, Grottke, Astrid, Hofmann, Bianca T., Nashan, Björn, Jücker, Manfred
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.12.2014; Springer; Springer Nature B.V
• Subjects: Antineoplastic agents; Antineoplastic Agents - pharmacology; Apoptosis; Benzimidazoles - pharmacology; Bile Duct Neoplasms - metabolism; Bile Ducts, Intrahepatic - metabolism; Biological and medical sciences; Cancer therapies; Cell growth; Cell Proliferation - drug effects; Cholangiocarcinoma; Cholangiocarcinoma - metabolism; Clinical trials; Drug resistance; Drug Resistance, Neoplasm; Extracellular Signal-Regulated MAP Kinases - antagonists & inhibitors; Gastroenterology. Liver. Pancreas. Abdomen; Heterocyclic Compounds, 3-Ring - pharmacology; Humans; Inhibitor drugs; Kinases; Liver. Biliary tract. Portal circulation. Exocrine pancreas; Medical prognosis; Medical sciences; Medicine; Medicine & Public Health; Mitogen-Activated Protein Kinase Kinases - antagonists & inhibitors; Morpholines - pharmacology; Multiple tumors. Solid tumors. Tumors in childhood (general aspects); Oncology; Pharmaceutical sciences; Pharmacology. Drug treatments; Pharmacology/Toxicology; Phosphatidylinositol 3-Kinases - antagonists & inhibitors; Preclinical Studies; Protein Kinase Inhibitors - pharmacology; Proto-Oncogene Proteins c-akt - antagonists & inhibitors; raf Kinases - antagonists & inhibitors; Signal transduction; Signal Transduction - drug effects; Studies; Thoracic surgery; TOR Serine-Threonine Kinases - antagonists & inhibitors; Tumors; Germany; mTOR; Combinatorial treatment; MEK; AKT; Cholangiocarcinoma; Extracellular signal-regulated protein kinase; Acquired; Hepatic disease; Biliary tract disease; Signal transduction; Malignant cholangioma; Protooncogene; Enzyme; Transferases; Akt protein kinase; Mitogen-activated protein kinase; Malignant tumor; 1-Phosphatidylinositol 3-kinase; Resistance; Treatment; C-Onc gene; Mammalian target of rapamycin; Digestive diseases; Reversibility; Inhibitor; Cancer
• ISSN: 0167-6997; 1573-0646
• DOI: 10.1007/s10637-014-0149-7

Summary Until today, there is no systemic treatment available for advanced cholangiocarcinoma (CCA). Recent studies have shown a frequent upregulation of the PI3K-AKT-mTOR and RAF-MEK-ERK pathways in this type of cancer. However, considering their high extend of redundancy and cross-talk, targeting only one pathway is likely to result in therapy failure and emergence of resistances. To provide a rationale for treatment of CCA with inhibitors of these respective pathways, we analyzed the effects of AKT inhibitor MK-2206, MEK inhibitor AZD6244 (ARRY-142886) and mTOR kinase inhibitor AZD8055 on three CCA cell lines in vitro, concerning proliferation, cell signaling and apoptosis. Furthermore, AZD6244 resistant cell lines have been generated to investigate, how their response may be affected by prolonged treatment with only a single inhibitor. Our data demonstrates that co-targeting of both, the PI3K/AKT/mTOR and RAF-MEK-ERK pathway, as well as vertical targeting of AKT and mTOR results in strong synergistic effects on proliferation and cell survival with combination indices below 0.3. Mechanistically, the combinatorial treatment with MK-2206 in addition to AZD8055 is necessary because AKT kinase activity was quickly restored after mTOR kinase inhibition. Interestingly, acquired MEK inhibitor resistance to AZD6244 was reversed by combined treatment with AZD6244 and either MK-2206 or AZD8055. Our data suggest that a combination of inhibitors targeting those respective pathways may be a viable approach for future application in patients with cholangiocarcinoma. Implications: AKT, mTOR and MEK are promising targets for a combinatorial treatment of cholangiocarcinoma cells even after acquisition of MEK inhibitor resistance.