BMP4 and pituitary gland adenoma: For example, downregulation of BMP4 in pituitary tumors is related to histone methylation, but is DNA methylation-independent [25], and HMGA1 overexpression in pituitary adenomas is due to hypermethylation and silencing of the genes encoding for miRNAs targeting HMGA transcripts, rather than to direct methylation of the HMGA-encoding gene [26,27].