{
  "abstract": "Background SWI/SNF mutations have been associated with improved responses to immunotherapy across multiple cancer types. Head and neck squamous cell carcinoma (HNSCC) has frequent amplification of the SWI/SNF subunit ACTL6A, which is associated with increased chromatin occupancy of SWI/SNF and up-regulation of proliferative pathways. The role of SWI/SNF in regulating immune phenotypes of HNSCC has not been established.Methods Tumor deconvolution studies were performed using the HNSCC TCGA database. shACTL6A was used to generate stable knockdowns of the mouse oral cavity cell lines MOC1 and MOC2, which were used for a syngeneic tumor model and interferon-gamma (IFNG) induction of PD-L1, respectively. siACTL6A was used for RNA-seq studies of the HNSCC cell line SCC1. The SMARCA2/SMARCA4 PROTAC degrader AU-15330 was used for RNA-seq of the HNSCC cell line FaDu and IFNG induction of PD-L1 in FaDu and SCC1 cells. T cell cytotoxicity assay was done by co-culturing SIINFEKL expressing MOC2 cells and OT-I expressing CD8+ T cells.Results ACTL6A amplification was associated with decreased CD8+ T cell and increased myeloid derived suppressor cell (MDSC) infiltration while SWI/SNF subunit mutations had the opposite effect in HNSCC tumors using CIBERSORTx. Using a syngeneic tumor model, shACTL6A MOC1 cells had significantly slower tumor growth in vivo compared to control. Using flow cytometry, we detected significantly increased intra-tumoral lymphocytes in shACTL6A MOC1 cells. We performed RNA-seq after siACTL6A treatment of SCC1 cells and found decreased IFNG signaling and increased inflammatory pathways (NFKB) on gene set enrichment analysis (GSEA). Since ACTL6A is not currently druggable, we tested whether the SMARCA2/SMARCA4 PROTAC degrader AU-15330 (1 µM) had similar effects to siACTL6A. FaDu cells were treated with AU-15330 or DMSO for 72 hours and RNA-seq was performed. GSEA revealed similar down-regulation of IFNG pathways and up-regulation of NFKB with AU-15330 treatment, suggesting these effects are mediated by SWI/SNF. Based on IFNG’s role in regulating PD-L1 expression, we tested whether AU-15330 influences IFNG-mediated up-regulation of PD-L1 and p-STAT1. AU-15330 significantly abrogated induction of PD-L1 and p-STAT1 in SCC1 and FaDu cells. We then performed T-cell killing assay (OT-1/SIINFEKL) with the immune cold MOC2 cell line and found that treatment with AU-15330 significantly improved CD8+ T cell mediated killing.Conclusions ACTL6A over-expression is common in HNSCC and leads to immune evasion by enhancing IFNG signaling and induction of PD-L1. A translational approach using SWI/SNF inhibitors may overcome this phenotype and improve immunotherapy outcomes in patients.Ethics Approval The experiments in this protocol are approved by the Stanford IACUC (protocol #34643)",
  "authors": [
    {
      "affiliations": [
        "Stanford University, Stanford, CA, USA"
      ],
      "name": "Mehri Monavarian"
    },
    {
      "affiliations": [
        "Stanford University, Stanford, CA, USA"
      ],
      "name": "Patrick Galligan"
    },
    {
      "affiliations": [
        "Stanford University, Stanford, CA, USA"
      ],
      "name": "Ivan Stepanek"
    },
    {
      "affiliations": [
        "Stanford University, Stanford, CA, USA"
      ],
      "name": "Andrey Finegersh"
    }
  ],
  "title": "1282 SWI/SNF regulates anti-tumor immunity and PD-L1 expression in head and neck squamous cell carcinoma",
  "uid": "62f4bc62-69e1-5399-830c-8b2f9e0e6b13"
}