Therapeutic Targeting of the DNA Damage Response Using an ATR Inhibitor in Biliary Tract Cancer.
PURPOSE
The DNA damage response (DDR) is a multi-complex network of signaling pathways involved in DNA damage repair, cell cycle checkpoints, and apoptosis. In the case of biliary tract cancer (BTC), the strategy of DDR targeting has not been evaluated, even though many patients have DNA repair pathway alterations. The purpose of this study was to test the DDR-targeting strategy in BTC using an ataxia-telangiectasia and Rad3-related (ATR) inhibitor.


MATERIALS AND METHODS
A total of nine human BTC cell lines were used for evaluating anti-tumor effect of AZD6738 (ATR inhibitor) alone or combination with cytotoxic chemotherapeutic agents through MTT assay, colony-forming assays, cell cycle analyses, and comet assays. We established SNU478-mouse model for in vivo experiments to confirm our findings.


RESULTS
Among nine human BTC cell lines, SNU478 and SNU869 were the most sensitive to AZD6738, and showed low expression of both ataxia-telangiectasia mutated (ATM) and p53. AZD6738 blocked p-Chk1 and p-glycoprotein and increased γH2AX, a marker of DNA damage, in sensitive cells. AZD6738 significantly increased apoptosis, G2/M arrest and p21, and decreased CDC2. Combinations of AZD6738 and cytotoxic chemotherapeutic agents exerted synergistic effects in colony-forming assays, cell cycle analyses, and comet assays. In our mouse models, AZD6738 monotherapy decreased tumor growth and the combination with cisplatin showed more potent effects on growth inhibition, decreased Ki-67, and increased terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling than monotherapy with each drug.


CONCLUSION
In BTC, DDR targeting strategy using ATR inhibitor demonstrated promising antitumor activity alone or in combination with cytotoxic chemotherapeutic agents. This supports further clinical development of DDR targeting strategy in BTC.
['Nam|Ah-Rong|AR|', 'Jin|Mei Hua|MH|', 'Park|Ji Eun|JE|', 'Bang|Ju-Hee|JH|', 'Oh|Do-Youn|DY|', 'Bang|Yung-Jue|YJ|']
D000818:Animals D064007:Ataxia Telangiectasia Mutated Proteins D001661:Biliary Tract Neoplasms D045744:Cell Line, Tumor D049109:Cell Proliferation D002470:Cell Survival D002945:Cisplatin D004260:DNA Repair D015536:Down-Regulation D004357:Drug Synergism D005260:Female D015972:Gene Expression Regulation, Neoplastic D006801:Humans D007211:Indoles D051379:Mice D009025:Morpholines D011743:Pyrimidines D013449:Sulfonamides D013454:Sulfoxides D016159:Tumor Suppressor Protein p53 D023041:Xenograft Model Antitumor Assays
DNA damage response ATR inhibitor ATM p53 Biliary tract neoplasms