ARID2 Deficiency Correlates with the Response to Immune Blockade in Melanoma

The SWI/SNF chromatin remodeler family includes the BAF and PBAF complexes. ARID2, encoding a PBAF complex subunit, is frequently mutated in melanoma independently of BRAF/RAS mutations. Emerging evi-dence shows that SWI/SNF complexes regulate tumor immunity; for instance, the loss of PBRM1, another PBAF complex subunit, enhances susceptibility to immune checkpoint inhibitors in melanoma. Notably, ARID2 mutations are more frequent in melanoma than PBRM1 mutations. However, the role of ARID2 as a modulator of tumor immunity remains unclear. In this study, we show that ARID2 knockout sensitizes melanoma to im-mune checkpoint inhibitors. Anti-PD-L1 treatment restricts tumor growth in mice bearing ARID2-knockout melanoma cells, correlating with an increase in the infiltration of cytotoxic CD8(+) T cells. Furthermore, ARID2 deficiency leads to signal transducer and activator of transcription 1 upregulation, which subsequently causes increased expression of T-cell-attracting chemokines such as CXCL9, CXCL10, and CCL5. These results demonstrate that ARID2 is an immunomodulator and a potential biomarker that indicates immune checkpoint inhibitor effectiveness in patients with melanoma.