PTTG1 and pituitary gland adenoma: Based on our results, it seems that the PTTG1 mRNA overexpression in pituitary adenoma is more likely through epigenetic mechanisms rather than variation in the DNA sequence of PTTG1. Holt et al. reported that PTTG1 was regulated by cyclin-dependent kinase (CDK)-mediated phosphorylation [23], suggesting a link between the control of the cell cycle by CDKs and PTTG1.