Expression and Regulation of BCL-2 Family Genes in Human Adrenocortical Adenomas in Comparison with Adrenal Hyperplasia of Cushing's Disease

The significance of increases in the expression of apoptosis-suppressing genes such as bcl-2 and mcl-1/EAT in human adrenal tumors has not yet been fully elucidated. Furthermore the roles of these genes in cell proliferation may involve interaction with steroidogenesis in the tumors via intracellular second messengers. Cyclic AMP (cAMP) caused human adrenocortical H295R cells to overexpress hCYP17 resulting in hypersecretion of cortisol. At the same time, however, expression of bcl-2, which has a cAMP response element (CRE), was not affected. Furthermore, in vivo Bcl-2 protein analysis showed its down-regulation in adrenal hyperplasia of Cushing's disease despite ACTH stimulation. Exogenous addition of glucocorticoid did not affect the expression of bcl-2 family genes. Expressions of Mcl-1/EAT and Bax did not differ markedly among human adrenal glands affected by various pathologies. In conclusion the down-regulation of Bcl-2 in Cushing's disease did not agree with no induction of this gene by cAMP in H295R cells, suggesting that expression of Bcl-2 protein was not regulated mainly by cAMP-protein kinase (PKA) pathways in human adrenal hyperplasia.