Cutaneous inflammation accelerates the premalignant expansion of melanocytes bearing oncogenic mutations

How the cutaneous microenvironment influences early melanomagenesis is poorly understood. Here, we assessed the effects of three immune perturbations on premalignant melanocyte expansion in an autochthonous mouse model of disease. Depletion of regulatory T (T _reg ) cells markedly accelerated melanoproliferation, an unexpected phenotype that was associated with monocyte and macrophage infiltration, the production of inflammatory and angiogenic factors, and vascular leakage. In line with these observations, single cell transcriptomic analysis of T _reg cell deficient skin revealed robust accumulation of monocyte-derived macrophages with tissue remodeling characteristics. Acute UV irradiation and 2,4-dinitrofluorobenzene (DNFB)-induced contact hypersensitivity had analogous effects on both the cellular microenvironment of the skin and the expansion of local premalignant melanocytes. Treatment with the anti-inflammatory agent dexamethasone attenuated DNFB-induced melanocyte expansion and vascular remodeling. Collectively, these results identify a conserved inflammatory axis linked to the early outgrowth of oncogenic melanocytes in the skin.