Targeting Arachidonic Acid Metabolism Enhances Immunotherapy Efficacy in ARID1A-Deficient Colorectal Cancer

ARID1A, a core constituent of SWI/SNF complex, is mutated in approximately 10% of colorectal cancers (CRC). While ARID1A deficiency corresponds to heightened immune activity in CRC, immune checkpoint inhibitors (ICIs) have shown limited efficacy in these tumors. The discovery of targetable vulnerabilities associated with ARID1A deficiency in CRC could expand treatment options for patients. In this study, we demonstrated that arachidonic acid metabolism inhibitors synergize with ICIs in ARID1A-deficient CRC by enhancing the activity of CD8+ T cells and inhibiting vasculogenic mimicry (VM). Epigenetic analysis using ATAC-seq and ChIP-qPCR revealed that the lack of ARID1A results in reduced levels of PTGS1 and PTGS2, the key enzymes that control the arachidonic acid pathway. Low PTGS1 and PTGS2 expression generated a reliance on the remaining functionality of the arachidonic acid pathway in ARID1A-deficient cells. The arachidonic acid pathway inhibitor aspirin selectively inhibited the growth of ARID1A-deficient CRC, and aspirin sensitized tumors lacking ARID1A to immunotherapy. Together, these findings suggest that blocking arachidonic acid metabolism can enhance immune responses against tumors by activating CD8+ T cells and inhibiting VM, which synergizes with ICIs to improve treatment of ARID1A-deficient CRC.