TGFB1 and melanoma: Furthermore, RNA sequencing and flow cytometry analyses of melanoma patients showed that downregulation of MHC class I molecules is a hallmark of PD-1 inhibitor resistance that is associated with TGF-β, upregulation of SNAI1, CAF (cancer-associated fibroblast) related signatures and the MITF-low/AXL-high melanoma phenotype.