Dataset Information

SMARCA4 deficiency-associated heterochromatin induces intrinsic DNA replication stress and susceptibility to ATR inhibition in lung adenocarcinoma.

ABSTRACT: The SWI/SNF chromatin remodeling complex regulates transcription through the control of chromatin structure and is increasingly thought to play an important role in human cancer. Lung adenocarcinoma (LADC) patients frequently harbor mutations in SMARCA4, a core component of this multisubunit complex. Most of these mutations are loss-of-function mutations, which disrupt critical functions in the regulation of chromatin architecture and can cause DNA replication stress. This study reports that LADC cells deficient in SMARCA4 showed increased DNA replication stress and greater sensitivity to the ATR inhibitor (ATRi) in vitro and in vivo. Mechanistically, loss of SMARCA4 increased heterochromatin formation, resulting in stalled forks, a typical DNA replication stress. In the absence of SMARCA4, severe ATRi-induced single-stranded DNA, which caused replication catastrophe, was generated on nascent DNA near the reversed forks around heterochromatin in an Mre11-dependent manner. Thus, loss of SMARCA4 confers susceptibility to ATRi, both by increasing heterochromatin-associated replication stress and by allowing Mre11 to destabilize reversed forks. These two mechanisms synergistically increase susceptibility of SMARCA4-deficient LADC cells to ATRi. These results provide a preclinical basis for assessing SMARCA4 defects as a biomarker of ATRi efficacy.

SUBMITTER: Kurashima K

PROVIDER: S-EPMC8210217 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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<i>SMARCA4</i> deficiency-associated heterochromatin induces intrinsic DNA replication stress and susceptibility to ATR inhibition in lung adenocarcinoma.

Kurashima Kiminori K Kashiwagi Hideto H Shimomura Iwao I Suzuki Ayako A Takeshita Fumitaka F Mazevet Marianne M Harata Masahiko M Yamashita Takayuki T Yamamoto Yusuke Y Kohno Takashi T Shiotani Bunsyo B

NAR cancer 20200501 2

The SWI/SNF chromatin remodeling complex regulates transcription through the control of chromatin structure and is increasingly thought to play an important role in human cancer. Lung adenocarcinoma (LADC) patients frequently harbor mutations in SMARCA4, a core component of this multisubunit complex. Most of these mutations are loss-of-function mutations, which disrupt critical functions in the regulation of chromatin architecture and can cause DNA replication stress. This study reports that LAD ...[more]

PMID: 34316685

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Project description:Targeting cell cycle checkpoints has emerged as a promising strategy in cancer therapy, yet single-agent inhibitors often fail due to compensatory mechanisms. Here, we demonstrate that co-inhibition of ATR (RP-3500) and PKMYT1 (RP-6306) induces synthetic lethality in Rb1-deficient breast cancers by disrupting both S/G2 and G2/M checkpoints, resulting in replication stress, premature mitotic entry, and DNA damage accumulation. In vitro, Rb1-deficient breast cancer cell lines exhibited marked apoptosis and loss of clonogenic potential, whereas Rb1-proficient models remained largely resistant to combination treatment. Genetic manipulation of Rb1 confirmed this dependency: Rb1 knockdown sensitized resistant models, and overexpression conferred protection. In vivo, patient-derived xenograft (PDX) models recapitulated these findings. Rb1-deficient tumors underwent complete regression, while Rb1-proficient tumors showed limited response with RP-3500/RP-6306 treatment. Combination therapy was well tolerated in vivo, without significant toxicity or weight loss. Biomarker analysis revealed increased γH2AX and reduced Ki67 staining exclusively in Rb1-deficient PDX models, underscoring the specificity of this response. Mechanistically, Rb1 loss impaired double-strand DNA repair by attenuating homologous recombination and non-homologous end joining, leading to replication fork collapse, chromosomal instability, and mitotic catastrophe. Proteogenomic analysis identified JNK/p38 stress response pathway activation as a key driver of apoptosis following ATR/PKMYT1 inhibition in Rb1-deficient cells. Clinically, analysis of stage IV breast cancer patient datasets revealed that Rb1-low tumors display reduced DNA repair pathway activity and are enriched in triple-negative and CDK4/6 inhibitor-resistant luminal breast cancers. These findings establish Rb1 loss as a functional biomarker for ATR/PKMYT1-targeted therapy, offering a precision treatment strategy for advanced breast cancers.

Dataset Information

SMARCA4 deficiency-associated heterochromatin induces intrinsic DNA replication stress and susceptibility to ATR inhibition in lung adenocarcinoma.

Publications

<i>SMARCA4</i> deficiency-associated heterochromatin induces intrinsic DNA replication stress and susceptibility to ATR inhibition in lung adenocarcinoma.

Similar Datasets

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