GDF15 reprograms the microenvironment to drive the development of uveal melanoma liver metastases.

Uveal melanoma (UM) results in fatal liver metastasis, yet little is known about the interactions between UM and host cells in the tumor microenvironment that promote this distinctive proclivity. Here, we used single cell (sc)-RNA-Seq analysis of UM-hepatic stellate cell (HSC) co-cultures to demonstrate that HSCs enriched for UM cell states that expressed genes implicated in cell survival, metabolic reprogramming and angiogenesis. A lead candidate driver of HSC reprogramming was the TGF-β family member GDF15, which was associated with a metastatic UM phenotype. Silencing of BAP1 in UM cells led to increased GDF15 expression and accumulation of H3K27ac marks at the GDF15 promoter. Treatment of HSCs with GDF15 led to increased expression extracellular matrix proteins, inflammatory cytokines and angiogenic factors, including IL-8. Both exogenous GDF15, IL-8 and conditioned media from UM-HSC co-cultures increased endothelial cell network formation in vitro, an effect that was blocked by anti-GDF15 antibodies. In multiple models of metastatic UM, silencing of GDF15 inhibited the outgrowth of metastatic lesions, associated with reduced deposition of extracellular matrix and recruitment of endothelial cells. UM liver metastasis development is dependent upon GDF15-mediated remodeling of the liver microenvironment leading to an angiogenic response and matrix deposition that supports tumor growth.