Through unknown mechanisms, heat shock protein 90 (USP90), histone deacetylase 2 (HDAC2), Cdk5 and Abl enzyme substrate 1 (CABLES1), the pituitary tumor apoptosis gene (PTAG), thrombospondin-1 (TSP-1), and caspase-8 (CASP-8) are also involved in the tumorigenesis of corticotrophinomas [23]. This evidence concerns the gene HDAC2 and neoplasm.