Therapeutic Targeting of the DNA Damage Response Using an ATR Inhibitor in Biliary Tract Cancer

Abstract

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.

Inhibition of ATR Increases the Sensitivity to WEE1 Inhibitor in Biliary Tract Cancer

“…Cells were exposed to 1 μmol/L AZD1775, 1 μmol/L AZD6738, or both for 24 hours. Then, the cells were harvested, and alkaline comet assay was performed as previously described [ 11 ]. The tail moment and intensity were measured using the Comet Assay IV program (Andor Technology, Belfast, UK).…”

Targeting P53 as a Future Strategy to Overcome Gemcitabine Resistance in Biliary Tract Cancers

“…AZD6738, an ATR inhibitor, has shown preclinical activity in panels of BTC cell lines, particularly with SNU478 and SNU869 cell lines (both p53 MUT ) [88]. The combination of AZD6738 and MK1775 has also been reported to have synergistic effects in p53 MUT BTC cell lines [89].…”

The Cancer Stem Cell Inhibitor Napabucasin (BBI608) Shows General Cytotoxicity in Biliary Tract Cancer Cells and Reduces Cancer Stem Cell Characteristics

“…Genetic alterations and overexpression of ATM have been described for several cancer types, including BTC [27,28,29]. Moreover, Nam et al described ATM expression in HuCCt-1 cells [30]. Interestingly, in lung cancer stem-like cells, Chen and coworkers demonstrated that downregulation of ATM sensitizes cells towards radiotherapy, again suggesting that future studies might identify napabucasin as an adjuvant drug for conventional chemotherapeutics or radiotherapy in BTC and other cancer types.…”