Expression of the ACTH receptor, steroidogenic acute regulatory protein, and steroidogenic enzymes in canine cortisol-secreting adrenocortical tumors

Studies of human adrenocortical tumors (ATs) causing Cushing's syndrome suggest that hypersecretion of cortisol is caused by altered expression of steroidogenic enzymes and that steroidogenesis can only be maintained when there is expression of the ACTH receptor (ACTH-R). Here we report the screening for the mRNA expression of the ACTH-R, steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme, 3β-hydroxysteroid dehydrogenase, 21-hydroxylase (all in 38 cortisol-secreting ATs), 17α-hydroxylase, and 11β-hydroxylase (both in 28 cortisol-secreting ATs). Real-time PCR (RT-PCR) was applied in all samples and was compared with that in normal canine adrenal glands. Messenger-RNA encoding StAR, steroidogenic enzymes, and ACTH-R were present in both normal adrenal glands and cortisol-secreting ATs. The amounts of mRNA encoding StAR and enzymes of the steroidogenic cluster needed for cortisol production did not differ significantly between either adenomas or carcinomas and normal adrenal glands. The amount of mRNA encoding ACTH-R was significantly lower in carcinomas than in normal adrenal glands (P = 0.008). In conclusion, RT-PCR analysis revealed no overexpression of StAR and steroidogenic enzymes in canine cortisol-secreting ATs. Significant downregulation of ACTH-R in carcinomas might be associated with the malignant character of the AT.

Canine prostate carcinoma: epidemiological evidence of an increased risk in castrated dogs

The present retrospective study investigated the frequency of prostate carcinoma (PCA) among prostate abnormalities in dogs and determined whether castration influences the incidence of PCA in dogs. During the years 1993-1998, 15,363 male dogs were admitted to the Utrecht University Clinic of Companion Animals, and of these dogs 225 were diagnosed with prostatic disease. In addition, another 206 male dogs were diagnosed as having prostatic disease based on cytologic examination of aspiration biopsies submitted by referring veterinarians. Benign prostatic hyperplasia was diagnosed in 246 dogs (57.1%), prostatitis in 83 dogs (19.3%), and PCA in 56 dogs (13%). Dogs with PCA were significantly older (mean age=9.9 years) than dogs with other prostatic diseases (mean age=8.4 years). The Bouvier des Flandres breed had an increased risk (odds ratio (OR)=8.44; 95% CI 4.38-16.1) of having PCA. Castration (26/56) increased the risk (OR=4.34; 95% CI 2.48-7.62) of PCA. The mean age at diagnosis of PCA in castrated dogs and in intact male dogs was not significantly different. The interval between castration and onset of prostatic problems was highly variable, suggesting that castration does not initiate the development of PCA in the dog, but it does favour tumor progression.