Heterozygous ATR mutations in mismatch repair-deficient cancer cells have functional significance

Area of Science:

• Molecular biology
• Cancer genetics
• Cell cycle regulation

Background:

• The ATR (ataxia telangiectasia and Rad3-related) kinase pathway is crucial for cellular responses to DNA damage.
• Mutations in the ATR gene, particularly heterozygous truncating mutations in exon 10, are observed in cancers with microsatellite instability.
• Understanding the functional consequences of these ATR mutations is vital for cancer treatment strategies.

Purpose of the Study:

• To investigate the functional impact of heterozygous truncating ATR mutations on DNA damage response pathways.
• To determine the role of ATR mutations in the development and progression of microsatellite instability-positive cancers.

Main Methods:

• Utilizing cell line models of endometrial cancer with ATR mutations.
• Assessing ATR-dependent Chk1 phosphorylation and cell-cycle arrest following DNA damage induction.
• Analyzing the functional consequences of dominant-negative effects of ATR mutations.

Main Results:

• Truncating ATR mutations exhibit a dominant-negative effect, impairing ATR-dependent Chk1 phosphorylation.
• Cells with ATR mutations show defects in cell-cycle arrest mechanisms after DNA damage.
• Endometrial cell lines harboring ATR mutations demonstrate impaired ATR-dependent responses.

Conclusions:

• ATR mutations significantly compromise DNA damage repair pathways, affecting cellular response to genotoxic stress.
• These findings highlight the critical role of ATR mutations in the pathogenesis of a subset of microsatellite instability-positive endometrial, colon, and stomach cancers.
• ATR mutations may serve as a predictive biomarker for chemotherapy response in specific cancer types.