NTF4 and melanoma: In agreement with further publications [29, 30] we show by qRT-PCR that neurotrophins NGF (nerve growth factor), NT-3, NT-4 (neurotrophins 3 and 4), and BDNF (brain-derived neurotrophic factor) are not only derived from other skin-cells like fibroblasts and keratinocytes, but are produced to different extends by melanoma cells itself (Supplementary Figure S1).