Identification of ATR-Chk1 pathway inhibitors that selectively target p53-deficient cells without directly...

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• Chemotherapy resistance is a major challenge in cancer treatment, often exacerbated by p53 deficiency.
• In p53-deficient cancers, cell survival post-DNA damage depends on ATR and Chk1 kinases regulating intra-S and G2-M checkpoints.

Purpose of the Study:

• To identify novel small molecules that inhibit the ATR pathway, specifically targeting ATR-Chk1 function.
• To sensitize p53-deficient cancer cells to DNA-damaging chemotherapy agents.

Main Methods:

• Conducted a phenotype-based screen of 9,195 compounds to identify inhibitors of hydroxyurea-induced Chk1 phosphorylation (Ser345).
• Evaluated identified compounds for their ability to inhibit ATR-selective phosphorylation and sensitize cancer cells in vitro and in vivo.
• Assessed the mechanism of action, distinguishing from typical ATP-competitive ATR inhibitors.

Main Results:

• Identified four small-molecule compounds (anthothecol, dihydrocelastryl, erysolin, and MARPIN) that inhibit ATR-Chk1 signaling.
• These compounds sensitized p53-deficient cancer cells to DNA-damaging agents, both in vitro and in vivo.
• The compounds demonstrated a distinct mechanism, disabling ATR-Chk1 function without inhibiting ATR catalytic activity.

Conclusions:

• Discovered novel molecular probes (anthothecol, dihydrocelastryl, erysolin, MARPIN) for studying the ATR pathway.
• These compounds offer a mechanistically distinct approach to sensitizing p53-deficient cancers to chemotherapy.
• Provides potential avenues for developing improved therapeutic strategies against DNA-damaging drug-resistant cancers.