MacroH2A restricts melanoma progression via inhibition of chemokine expression in cancer-associated fibroblasts [spatial transcriptomics]

MacroH2A has tumor suppressive functions in melanoma and other cancers, yet its role in the tumor microenvironment remains unappreciated. Using an autochthonous, immunocompetent mouse model of melanoma, we demonstrate that mice devoid of macroH2A variants exhibit increased tumor burden compared to wild type counterparts. MacroH2A-deficient tumors accumulate immunosuppressive monocytes and decreased functional cytotoxic T cells, and consistent with this compromised anti-tumor response, exhibit upregulation of pro-inflammatory cytokines. Single cell transcriptomics not only identifies cancer-associated fibroblasts (CAFs), whose frequency and activation increase in the absence of macroH2A, as the source of myeloid chemoattractants but also demonstrates dedifferentiation along the neural crest lineage of the tumor compartment. CAFs lacking macroH2A display hyper-inducible inflammatory gene expression and promoters of these genes present increased chromatin looping to enhancers that gain H3K27ac. In sum, we reveal a tumor suppressive role for macroH2A variants through regulation of chromatin architecture of inflammatory genes in the tumor stroma with potential implications for human melanoma. Overall design: Spatial transcriptomics was carried out in WT and macroH2A deficient melanomas to map the localization of cell types previously identified by scRNA-seq.