ARID1A Mutation in Cancer
Tumor SuppressorAT-Rich Interaction Domain 1A
ARID1A is a subunit of the SWI/SNF chromatin remodeling complex. Loss-of-function mutations alter gene expression programs and are frequent in ovarian clear cell, endometrial, and gastric cancers.
What Is ARID1A?
ARID1A (AT-Rich Interaction Domain 1A) encodes a key subunit of the SWI/SNF (BAF) chromatin remodeling complex, one of the most important epigenetic regulators in human cells. The SWI/SNF complex uses ATP hydrolysis to reposition nucleosomes, controlling access to DNA for transcription, repair, and replication. ARID1A specifically helps target the complex to AT-rich DNA sequences near gene promoters and enhancers. When ARID1A is lost, chromatin remodeling is disrupted, leading to aberrant gene expression programs.
ARID1A Mutations in Cancer
ARID1A is one of the most frequently mutated chromatin regulators in cancer, with loss-of-function mutations found in approximately 6-8% of all tumors. It is particularly prevalent in ovarian clear cell carcinoma (~50%), endometrial cancer (~40%), gastric cancer (~25%), bladder cancer (~25%), and cholangiocarcinoma (~15%). Unlike oncogenes with activating hotspot mutations, ARID1A mutations are predominantly truncating (nonsense, frameshift) and scattered throughout the gene, leading to complete protein loss.
Emerging Therapeutic Strategies
ARID1A loss creates synthetic lethal vulnerabilities that are being exploited therapeutically. ARID1A-deficient tumors depend more heavily on the residual SWI/SNF subunit ARID1B, the EZH2 histone methyltransferase, and PARP. EZH2 inhibitors (tazemetostat) show selective activity in ARID1A-mutant cancers. ARID1A loss may also enhance immunogenicity through increased mutational burden and altered antigen presentation, potentially predicting response to immune checkpoint inhibitors.
Morphological Associations
ARID1A-mutant tumors display characteristic histological features. In ovarian cancer, ARID1A loss defines the clear cell carcinoma subtype with its distinctive glycogen-rich cytoplasm. In endometrial cancer, ARID1A loss associates with dedifferentiated morphology. In gastric cancer, it correlates with microsatellite instability and lymphocyte-rich stroma. HistoAtlas quantifies these morphological patterns across 33 TCGA cancer types using computational analysis of whole slide images.
Frequently Asked Questions
What is an ARID1A mutation?
An ARID1A mutation is a loss-of-function change in the ARID1A gene, which encodes a subunit of the SWI/SNF chromatin remodeling complex. When ARID1A is lost, cells cannot properly regulate gene expression through chromatin remodeling. ARID1A mutations are common in ovarian clear cell carcinoma (~50%), endometrial cancer (~40%), and gastric cancer (~25%).
What cancers have ARID1A mutations?
ARID1A mutations are most common in ovarian clear cell carcinoma (~50%), endometrial carcinoma (~40%), gastric adenocarcinoma (~25%), bladder cancer (~25%), and cholangiocarcinoma (~15%). ARID1A is one of the most frequently mutated chromatin regulators across all cancer types.
How are ARID1A-mutant cancers treated?
ARID1A-mutant cancers are being targeted through synthetic lethality approaches. EZH2 inhibitors (tazemetostat) show selective activity in ARID1A-deficient tumors. ARID1A loss may also enhance response to immune checkpoint inhibitors due to increased tumor immunogenicity. Clinical trials are investigating these strategies across multiple tumor types.