M1 Macrophages Induce Protumor Inflammation in Melanoma Cells through TNFR-NF-κB Signaling.

The tumor microenvironment, with distinctive cell types and a complex extracellular matrix has a tremendous impact on cancer progression. In this study, we investigated the effects of proinflammatory (M1) and immunosuppressive (M2) macrophages on hyaluronan (HA) matrix formation and inflammatory response in melanoma cells. Proinflammatory factors secreted from M1 macrophages stimulated the formation of a thick pericellular HA matrix in melanoma cells due to upregulation of HA synthase 2 (HAS2). HAS2 silencing reversed the effect of M1 conditioned medium on pericellular HA coat formation, and interestingly, it also partly downregulated the M1 conditioned medium‒induced upregulation of inflammation-related genes (IL1β, IL6), as did the inhibitors for TNFR and IKKγ. Gene set enrichment analysis revealed that genes related to inflammatory responses and TNF-α signaling via NF-κB are enriched in the M1 conditioned medium‒treated melanoma cells. Moreover, the expression of matrix metalloproteinase 9 and three-dimensional cell invasion were induced in these cells, whereas M2 macrophages had no effect on HA synthesis, inflammatory response, or invasion. Our results indicate that the activation of TNFR-NF-κB signaling in M1 conditioned medium‒treated cells leads to HAS2 upregulation, which associates with a protumor inflammatory and invasive phenotype of melanoma cells.