ARID1A Mutations Are Associated with Increased Immune Activity in Gastrointestinal Cancer

Because traditional treatment strategies for advanced gastrointestinal (GI) cancers often have a limited therapeutic effect, immunotherapy could be a viable approach for the therapy of advanced GI cancers, considering the recent success of immunotherapy in treating various refractory malignancies, including the DNA mismatch repair-deficient GI cancers. However, only a subset of cancer patients currently respond to immunotherapy. Thus, it is important to identify useful biomarkers for predicting cancer immunotherapy response. The tumor suppressor gene has a high mutation rate in GI cancers and its deficiency is correlated with the microsatellite instability (MSI) genomic feature of cancer. We investigated the correlation between mutations and tumor immunity using three GI cancer genomics datasets by the bioinformatic approach, and found that diverse antitumor immune signatures were more highly enriched in -mutated GI cancers than in -wildtype GI cancers. The elevated immune activity in -mutated GI cancers was associated with the higher tumor mutation burden and lower tumor aneuploidy level, as well as a higher proportion of MSI cancers in this GI cancer subtype. Moreover, we found that -mutated GI cancers more highly expressed than -wildtype GI cancers. The elevated antitumor immune signatures and expression could contribute to the more active immunotherapeutic responsiveness and better survival prognosis in -mutated GI cancers than in -wildtype GI cancers in the immunotherapy setting, as evidenced in three cancer cohorts receiving immunotherapy. Thus, the mutation could be a useful biomarker for identifying GI cancer patients responsive to immunotherapy.