Ketoconazole, which was initially developed as an
antifungal agent, is a potent inhibitor of adrenal steroidogenesis and has therefore been used in the management of
Cushing's disease. Surprisingly, the reduction of
cortisol levels during
ketoconazole treatment is not accompanied by the expected elevation in plasma
adrenocorticotrophic hormone (
ACTH) at the loss of negative
cortisol feedback from corticotrophic cells, suggesting a direct effect of
ketoconazole on these cells. To characterize the direct effects of
ketoconazole, we evaluated its in vitro effect on cell viability using the pituitary tumoural cell lines AtT-20 (which secretes
ACTH), GH3 (which secretes
growth hormone and
prolactin) and αT3.1 (which secretes α-subunit) and we also determined the expression levels of genes involved in apoptosis and DNA replication by the quantitative reverse transcription polymerase chain reaction (qRT-PCR). We also evaluated
ACTH levels in AtT-20 cells during
ketoconazole treatment. We observed a
ketoconazole concentration-dependent decrease in pituitary cell viability and reduced
ACTH levels in AtT-20 cells after removal of the
drug. We also observed increased expression of cell death receptors (e.g. Fas, tumour
necrosis factor receptor) and
caspases (e.g., caspase-6, caspase-7, caspase-9), suggesting activation of the apoptosis pathway. In addition, we observed increased gene expression of the cell cycle inhibitors p21 and p27 in GH3 cells and increased expression of p21 in αT3.1 cells. In conclusion, our findings suggest that
ketoconazole significantly reduces cell viability in a concentration-dependent manner in pituitary tumour cell lines and is associated with an increase in apoptosis- and cell cycle regulation-related gene expression.