NTSR1 and melanoma: To explore the effect of macrophages ablation on melanoma invasion in the zebrafish xenograft model, we took advantage of the mpeg1:GAL4FF, UAS:NTR-mCherry transgenic line that expresses bacterial nitroreductase (NTR) fused to mCherry in macrophages, allowing the conversion of the prodrug metronidazole (MTZ) in a cytotoxic compound that causes macrophage death [32].