Melanin enhances metastatic melanoma colonization by inhibiting ferroptosis

Melanoma associated death is mainly caused by metastatic disease. Increased melanin levels are associated with decreased melanoma patient survival, yet the contribution of melanin to this process is unknown. Here we show that melanin protects circulating melanoma cells from ferroptosis, enhancing their metastatic potential. We observed that melanin levels in patient-derived uveal melanoma cells as well as cutaneous and conjunctival melanoma cell lines correlate with their metastatic potential in zebrafish xenografts. We find strong associations of the melanin biosynthesis gene TYRP1, ferroptosis related enzyme GPX4 and mitochondrial anion channel (VDAC1) with reduced melanoma-specific survival in TCGA data of cutaneous melanoma. Modulation of melanin levels significantly impacts melanoma metastatic potential, increasing or decreasing in concordance with melanin levels. Furthermore, melanin depletion significantly sensitized melanoma cells to ferroptosis leading to a decreased metastatic capacity and enhanced efficacy of ferroptosis induction based anti-cancer therapeutic strategies. Collectively, our results reveal that combined inhibition of melanin biosynthetic enzymes and induction of ferroptosis has potential as a treatment strategy of metastatic melanoma. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=148 SRC="FIGDIR/small/535376v1_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@1fc21a5org.highwire.dtl.DTLVardef@502b6org.highwire.dtl.DTLVardef@f522beorg.highwire.dtl.DTLVardef@1bbfdfa_HPS_FORMAT_FIGEXP M_FIG C_FIG