Expression of somatostatin, dopamine, progesterone and growth hormone receptor mRNA in canine cortisol-secreting adrenocortical tumours

Cortisol-secreting adrenocortical tumours (AT) in dogs are characterised by uncontrolled growth and excessive cortisol secretion. Dysregulated hormone receptor expression might be involved in tumour growth and hypersecretion of cortisol. The relative mRNA expression of growth hormone receptor, progesterone receptor, somatostatin receptors (SSTR1-3) and dopamine receptors (DRD1-2 and DRD5) was evaluated in 36 canine ATs and 15 adrenal glands obtained from healthy dogs. Compared with normal adrenal tissue, DRD2 mRNA expression was relatively lower in carcinomas, while SSTR1 mRNA expression was lower in both adenomas and carcinomas. Both of these features might contribute to loss of inhibition of tumour growth and upregulation of cortisol secretion. In canine ATs that had recurred within 30 months of surgical adrenalectomy, a marked increase in expression of DRD1 mRNA was observed. Targeting of specific hormone receptors, expressed by ATs, might be exploited for therapy.