Results demonstrate that histamine and H4R agonists significantly decreased clonogenic proliferation of human melanoma cells (IC50= 1.6 μM; 0.7 μM; 1 μM for histamine, clozapine and JNJ28610244, respectively), effect that was blocked with the combined treatment with the H4R antagonist JNJ7777120 (Figure 2A). This evidence concerns the gene HRH4 and melanoma.