ATR inhibitor AZD6738 increases the sensitivity of colorectal cancer cells to 5‑fluorouracil by inhibiting repair of DNA damage

Abstract

The repair of DNA damage caused by chemotherapy in cancer cells occurs mainly at two cell cycle checkpoints (G 1 and G 2 ) and is a factor contributing to chemoresistance. Most colorectal cancers harbor mutations in p53, the main pathway involved in the G 1 checkpoint, and thus, are particularly dependent on the G 2 checkpoint for DNA repair. The present study examined the effect of AZD6738, a specific inhibitor of ataxia telangiectasia mutated and rad3-related (ATR) involved in the G 2 checkpoint, combined with 5-fluorouracil (5-FU), a central chemotherapeutic agent, on colorectal cancer cells. Since 5-FU has a DNA-damaging effect, its combination with AZD6738 is likely to enhance the therapeutic effect. The effects of the AZD6738/5-FU combination were evaluated in various colorectal cancer cells (HT29, SW480, HCT116 and DLD-1 cells) by flow cytometry (HT29 cells), western blotting (HT29 cells) and water-soluble tetrazolium 1 assays (HT29, SW480, HCT116 and DLD-1 cells), as well as in an experimental animal model (HT29 cells). In vitro, the AZD6738/5-FU combination increased the number of mitotic cells according to flow cytometry, decreased the checkpoint kinase 1 phosphorylation levels and increased cleaved caspase-3 and phosphorylated form of H2A.X variant histone levels according to western blotting, and decreased the proliferation rate of four colon cancer cell lines according to cell viability experiments. In vivo, xenografted colorectal cancer cells treated with the AZD6738/5-FU combination exhibited a marked decrease in proliferation compared with the 5-FU alone group. The present results suggested that AZD6738 enhanced the effect of 5-FU in p53-mutated colorectal cancer.

AZD6738 Inhibits fibrotic response of conjunctival fibroblasts by regulating checkpoint kinase 1/P53 and PI3K/AKT pathways

“…Anyway, the safety of AZD6738 in ophthalmic applications needs to be evaluated in further in vivo experiments. Furthermore, AZD6738 can enhance the sensitivity of cancer cells to 5-FU ( Suzuki et al, 2022 ), which provides the possibility of AZD6738/5-FU combination to fight subconjunctival scarring in the eye, implying lower dosage, higher safety, and better efficacy.…”

AZD6738 promotes the tumor suppressive effects of trifluridine in colorectal cancer cells

“…The combination index scores were calculated to show the synergistic effects ( 25 ). The AZD6738 concentration of 0.5 µM was previously determined via cytotoxicity experiments in our laboratory ( 20 ). Cells (1.0×10 4 cells/well in 100 µl) were seeded in 96-well plates and allowed to adhere for 24 h at 37°C.…”

“…Our previous study demonstrated the treatment-enhancing effects of combination therapy with AZD6738 and 5-fluorouracil (5-FU) ( 20 ). 5-FU acts outside the S phase, and DNA-damaged cancer cells can be repaired at various cell cycle checkpoints.…”

ARPC1B promotes mesenchymal phenotype maintenance and radiotherapy resistance by blocking TRIM21-mediated degradation of IFI16 and HuR in glioma stem cells

“…AZD6738 has been widely evaluated the efficiency among colorectal cancer, head and neck cancer, lung cancer, neuroblastoma, etc. [ 35 – 39 ]. Besides, AZD6738 exhibited a promising antitumor activity in a phase II study for the treatment of advanced melanoma [ 40 ].…”