Endocrine Abstracts

Introduction: Aging is associated with the pathogenesis of many endocrinological disorders, especially for functioning adrenocortical disorders. In addition, mitochondria DNA abnormalities have been reported to be correlated with aging through ROS which eventually resulted in cell senescence. We previously reported that cortisol-producing adenomas (CPA) expressed more abundant cell senescent markers including p16 and p21, compared to other hormone-producing adenomas. However, the detailed pathophysiology of cell senescence and its association with histological features (compact and clear cells) in CPAs have remained unknown. Therefore, we analyzed cell senescent markers examined their correlation with clinicopathological factors in CPA including compact and clear cells respectively. In vitro study was performed with exposure to cortisol using H295R cell lines to explore the pathogenesis of cell senescence caused in cortisol-producing lesions.

Materials and methods: We immunolocalized p16, p21,p53 and ki67 in 20 CPAs. mtDNA abnormalities were examined in 20 CPAs, 10 adjacent ZF of CPA and 6 non-functional adenoma (NFA). mtDNA deletion was evaluated by nested-PCR, mtDNA copy number was studied by the relative ratio of copy number compared with diploidy of nuclear-coding genes using real-time PCR. In vitro study was performed in H295R cell lines with 10 nM hydrocortisone treatment.

Results: mtDNA copy number of CPA and tumoradjacent ZF were significantly lower than that of NFA. On the other hand, 4977bp mtDNA deletion was more frequently detected in CPA (53%) and adjacent ZF (50%) than in NFA (17%) and CPAs with 4977bp mtDNA deletion harbored higher serum cortisol level than those without 4977bp mtDNA deletion. p53 and Ki-67 were significantly higher in clear than compact tumor cells. However, immunoreactivities of CYP11B1, CYP17A1 and p16 as well as mtDNA copy number were significantly higher in compact than in clear tumor cells. In vitro study demonstrated that cortisol could increase p53 and p21 mRNA level, resulting in subsequent suppression of CDK4/6 and cell proliferation in H295R cells.

Discussion: We firstly demonstrated that excessive cortisol did induce cellular and mitochondrial senescent phenotype in CPA as the results of lower mtDNA copy number, frequent mtDNA deletion and higher expression of p21. GR could be involved in the regulation of cell senescence and could possibly control the cell cycles in adrenocortical cells. This study also firstly demonstrated that compact tumor cells harbored high hormonal activity but low proliferative ability while clear cells harbored relatively quiescent but relatively high proliferative ability than compact cells resulting in marked biological intratumoral heterogeneityof CPA.