Immunohistochemical Expression of p16 and p21 in Pituitary Tissue Adjacent to Pituitary Adenoma versus Pituitary Tissue Obtained at Autopsy: Is There a Difference?

Normal pituitary tissue is frequently used for comparison with protein expression in tumor tissue, being obtained either at surgery or at autopsy. p16 and p21 proteins are cyclin-dependent kinase inhibitors, belonging to INK4 and Cip/Kip family, respectively. Their expression is increased in response to DNA damage or other cellular stressors, resulting in the activation of cell cycle checkpoints. They also play important roles in cellular senescence. The purpose of this study was to investigate differences in p16 and p21 immunohistochemical expression in normal pituitary tissue adjacent to pituitary adenoma obtained during neurosurgical procedure with pituitary tissue obtained at autopsy, from patients who died from non-endocrinological diseases. Our results show significant difference in p16 nuclear and p21 cytoplasmic immunohistochemical expression between two types of normal pituitary tissues. One of the reasons for this difference could be the age of subjects because those who underwent autopsy for a non-endocrinological disease were significantly older than subjects who underwent neurosurgery for a pituitary adenoma. Our finding that differences are probably not influenced by postmortem changes is supported by no significant correlation between postmortem interval and immunohistochemical p16 and p21 expression. The influence of the presence of a pituitary adenoma could not be evaluated in these specimens.