Moreover, in vitro and in vivo observations have shown that HMGA proteins overexpression has an oncogenic activity, since effectively both HMGA1 and HMGA2 overexpression transforms mouse and rat fibroblasts [11], and both Hmga1 and Hmga2 transgenic mice develop NK-T cell lymphomas and pituitary adenomas [12,13,14]. This evidence concerns the gene HMGA2 and pituitary gland adenoma.