It therefore appears that NGFR is expressed in at least two different melanoma subpopulations: a group of NGFR-negative cells, in which it can be reversibly induced upon exposure to T cells or TNF, and as we demonstrate here, a subpopulation of stable NGFRhi cells, which exists in an (largely) irreversible state that is associated with both tumor and immune therapy resistance. This evidence concerns the gene TNF and melanoma.