ARID1B Deficiency Leads to Impaired DNA Damage Response and Activated cGAS-STING Pathway in Non-Small Cell Lung Cancer

Purpose: Lung cancer is a major cause of morbidity and mortality globally, necessitating the identification of predictive markers for effective immunotherapy. Mutations in SWI/SNF chromatin remodeling complex genes were reported sensitized human tumors to immune checkpoint inhibitors (ICIs), but the underlying mechanisms are unclear. This study aims to investigate the association between SWI/SNF gene ARID1B mutation and ICI response in non-small cell lung cancer (NSCLC) patients, to explore the functional consequences of ARID1B mutation on DNA damage response, immune microenvironment, and cGAS-STING pathway activation. Methods: TCGA LUAD, LUSC, and AACR GENIE data are analyzed to assess ARID1B mutation status in NSCLC patients. Prognostic analysis evaluates the effect of ARID1B mutation on patient outcomes. In vitro experiments carried to investigate the consequences of ARID1B knockdown on DNA damage response and repair. The immune microenvironment is assessed based on ARID1B expression, and the relationship between ARID1B and the cGAS-STING pathway is explored. Results: ARID1B mutation frequency is 5.7% in TCGA databases and 4.4% in the AACR GENIE project. NSCLC patients with ARID1B mutation showed improved overall and progression-free survival following ICIs treatment. ARID1B knockdown in lung cancer cell lines enhances DNA damage, impairs DNA repair, alters chromatin accessibility, and activates the cGAS-STING pathway. ARID1B deficiency is associated with immune suppression, indicated by reduced immune scores, decreased immune cell infiltration, and negative correlations with immune-related cell types and functions. Conclusion: ARID1B mutation may predict improved response to ICIs in NSCLC patients. ARID1B mutation leads to impaired DNA damage response and repair, altered chromatin accessibility, and cGAS-STING pathway activation. These findings provide insights into ARID1B's biology and therapeutic implications in lung cancer, highlighting its potential as a target for precision medicine and immunotherapy. Further validation and clinical studies are warranted.

Genetic background determines synaptic phenotypes in Arid1b-mutant mice

ARID1B, a chromatin remodeler, is strongly implicated in autism spectrum disorders (ASD). Two previous studies on Arid1b-mutant mice with the same exon 5 deletion in different genetic backgrounds revealed distinct synaptic phenotypes underlying the behavioral abnormalities: The first paper reported decreased inhibitory synaptic transmission in layer 5 pyramidal neurons in the medial prefrontal cortex (mPFC) region of the heterozygous Arid1b-mutant (Arid1b+/-) brain without changes in excitatory synaptic transmission. In the second paper, in contrast, we did not observe any inhibitory synaptic change in layer 5 mPFC pyramidal neurons, but instead saw decreased excitatory synaptic transmission in layer 2/3 mPFC pyramidal neurons without any inhibitory synaptic change. In the present report, we show that when we changed the genetic background of Arid1b+/- mice from C57BL/6 N to C57BL/6 J, to mimic the mutant mice of the first paper, we observed both the decreased inhibitory synaptic transmission in layer 5 mPFC pyramidal neurons reported in the first paper, and the decreased excitatory synaptic transmission in mPFC layer 2/3 pyramidal neurons reported in the second paper. These results suggest that genetic background can be a key determinant of the inhibitory synaptic phenotype in Arid1b-mutant mice while having minimal effects on the excitatory synaptic phenotype.

ARID1B-mediated disorders: Mutations and possible mechanisms

Mutations in the gene encoding AT-rich interactive domain-containing protein 1B (ARID1B) were recently associated with multiple syndromes characterized by developmental delay and intellectual disability, in addition to nonsyndromic intellectual disability. While the majority of ARID1B mutations identified to date are predicted to result in haploinsufficiency, the underlying pathogenic mechanisms have yet to be fully understood. ARID1B is a DNA-binding subunit of the Brahma-associated factor chromatin remodelling complexes, which play a key role in the regulation of gene activity. The function of remodelling complexes can be regulated by their subunit composition, and there is some evidence that ARID1B is a component of the neuron-specific chromatin remodelling complex. This complex is involved in the regulation of stem/progenitor cells exiting the cell cycle and differentiating into postmitotic neurons. Recent research has indicated that alterations in the cell cycle contribute to the underlying pathogenesis of syndromes associated with ARID1B haploinsufficiency in fibroblasts derived from affected individuals. This review describes studies linking ARID1B to neurodevelopmental disorders and it summarizes the function of ARID1B to provide insights into the pathogenic mechanisms underlying ARID1B-mediated disorders. In conclusion, ARID1B is likely to play a key role in neurodevelopment and reduced levels of wild-type protein compromise normal brain development. Additional studies are required to determine the mechanisms by which impaired neural development contributes to the intellectual disability and speech impairment that are consistently observed in individuals with ARID1B haploinsufficiency.