HDAC9 and melanoma: Histone hypoacetylation is also involved in the progression of melanoma cells since the reversible deacetylation by histone deacetylases (HDAC) can down-regulate several onco-suppressor genes, such as CDKN1A and phosphatidylinositol-4,5-biphosphate 5-phosphatase A (PIB5PA) [62,63].