FLT1 and metastatic melanoma: We identify TGFβ and IL-6 among the main tumour-derived factors responsible for Id1 upregulation in BMDCs, and demonstrate that Id1 and its upstream (TGFβ), as well as downstream mediators (S100A8/9 and VEGFR1) are significantly upregulated in advanced metastatic melanoma patients, confirming the translational value of our pre-clinical findings.