Radioimmunoassay in blood plasma of arginine esterase: the major secretory product of dog prostate

Comparative pathology of dog and human prostate cancer

Though relatively rare in dogs, prostate cancer (PCa) is the most common non-cutaneous cancer in men. Human and canine prostate glands share many functional, anatomical and physiological features. Due to these similarities, canine PCa has been proposed as a model for PCa in men. PCa is typically androgen-dependent at diagnosis in men and for this reason, androgen deprivation therapies (ADT) are important treatments for advanced PCa in men. In contrast, there is some evidence that PCa is diagnosed more commonly in castrate dogs, at which point, limited therapeutic options are available. In men, a major limitation of current ADT is that progression to a lethal and incurable form of PCa, termed castrate-resistant prostate cancer (CRPC), is common. There is, therefore, an urgent need for a better understanding of the mechanism of PCa initiation and progression to CRPC to enable the development of novel therapeutic approaches. This review focuses on the functional, physiological, endocrine and histopathological similarities and differences in the prostate gland of these species. In particular, we focus on common physiological roles for androgen signalling in the prostate of men and dogs, we review the short- and longer-term effects of castration on PCa incidence and progression in the dog and relate how this knowledge may be relevant to understanding the mechanisms of CRPC in men.

Evaluation of biomarker canine-prostate specific arginine esterase (CPSE) for the diagnosis of benign prostatic hyperplasia

Background

Benign prostatic hyperplasia (BPH) is the most common canine prostatic disorder. Although most or even all intact male dogs may develop BPH by 5–8 years of age, many show no clinical signs. Taking into account the non-specific character of clinical and ultrasonographic findings, a new diagnostic approach has recently been proposed based on the augmentation of blood canine prostate-specific arginine esterase (CPSE) in hyperplasic dogs. The aim of the present study was to verify CPSE levels in negative controls and hyperplasic dogs, considering cytological findings as the reference method and taking into account the fact that controls were middle-aged intact dogs (median of 5.0 years), contrarily to previous studies carried out with very young control dogs.

Results

Significant differences of median CPSE levels were found between controls and hyperplasic dogs (29.1 versus 160.7 ng/mL, respectively); and significant positive correlations were found between median CPSE levels and age or prostatic volume (r = 0.549 and 0.448, respectively; p < 0.001). Sensitivity, specificity, positive and negative likelihood ratios put into evidence the good performance of the test. The agreement between methods was found to be very high, notably between CPSE levels and cytological results (Cohen’s kappa coefficients above 0.8).

Conclusions

Considering the results all together, measurement of CPSE is confirmed as a useful and accurate method and should be considered as an alternative or complementary tool to conventional methods for the diagnosis of BPH in middle-aged dogs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-0996-5) contains supplementary material, which is available to authorized users.

Serum and seminal markers in the diagnosis of disorders of the genital tract of the dog: a mini-review

Serum and seminal biologic substances that are produced either by normal or abnormal tissues of the organism and that can be used to diagnose pathological conditions are usually referred as markers. The aim of this article is to briefly review the most relevant clinical features of the main genital markers in the male dog: alkaline phosphatase (AP), carnitine and canine prostate-specific arginine esterase (CPSE). Carnitine and AP are markers for the presence of epididymal fluid in the ejaculate and their measurement in azoospermic dogs has been used as an indicator of tubular patency of the ductal network. Although AP is not present in high concentrations in the testis, this does not preclude the possibility that testicular cells might secrete some AP. If this were true, AP could also reflect, at least in some degree, germ cell function in this species. Prostate-specific arginine esterase, the major secretory product of the canine prostate, is a known marker of gland secretion in the dog. Tumor markers frequently used in human medicine, such as prostatic acid phosphatase and prostate-specific antigen, are is still controversial in the diagnosis of prostatic carcinoma of the dog. Although further research is necessary to define the exact role of CPSE, it seems to be a promising diagnostic tool in nonneoplasic canine prostatic disorders. Future studies should also address the quantitative relationship among serum and prostatic androgen levels, prostatic androgen-dependent problems and how these are affected by anti-androgen treatment. The aim of this article is to briefly review the most relevant clinical features of three main genital markers of the male dog.

Identification of glandular kallikrein in dog pancreas and determination of its tissue distribution

In order to establish a formal link between previously purified canine urinary kallikrein and dog pancreatic kallikrein whose cDNA sequence has recently been published, we have isolated the pancreatic kallikrein from that animal species. Pancreatic cytosol proteins were sequentially subjected to chromatography on DEAE-Sepharose CL-6B and Concanavalin A-Sepharose, to an autolysis step and finally to two-dimensional gel electrophoresis. Kallikrein immunoreactive spots were identified with an antibody directed against canine urinary kallikrein. These proteins were isolated after electroblotting and the amino acid sequence of their NH2-terminal portion was determined by microsequencing. The sequence was found to be identical to the one deduced from pancreatic kallikrein cDNA. Using the same antibody and immunohistochemical procedures, kallikrein was found to be present in the pancreas, the salivary glands, the kidney, the colon, the lungs and the testis. These results thus confirm the molecular nature of a glandular kallikrein in the canine species.

The major dog pancreas protein recognized by an antiserum to dog prostate kallikrein is the anionic trypsin

1. On the basis of its immunoreactivity with a polyclonal antiserum to dog prostate kallikrein in Western blot experiments, a 30 kDa protein was purified from the pancreas of the dog using ion-exchange and gel filtration chromatography. 2. That protein was identified as the anionic trypsin by its NH2-terminal amino acid sequence. 3. The immunoreaction occurred despite an overall amino acid homology which was limited to 39% between the prostate kallikrein and anionic trypsin. 4. Otherwise, the anti-prostatic kallikrein antiserum was rather specific since it did not react with dog cationic trypsin, dog renal kallikrein and human prostate specific antigen.

Characterization and expression of the prostatic arginine esterase gene, a canine glandular kallikrein

The prostatic arginine esterase gene was isolated from a genomic library prepared with dog liver DNA in lambda EMBL3. The selected clone contained an insert of approximately 17 kb which included the whole coding portion of arginine esterase mRNA (5 exons plus 4 introns), 2 kb upstream from the initiation site and 12 kb downstream from the polyadenylation site. The intron-exon boundaries were identical to all known mammalian kallikrein genes. The deduced amino acid sequence indicated a high degree of identity (51-61%) with other kallikreins expressed not only in the prostate but also in the pancreas of various animal species. The 5'-flanking sequences contained potential regulatory elements such as a variant TATA box (TTTAAA), a CCAAT box, a SP1 transcriptional factor binding site (GGGCGG), and two TGTCCT motifs resembling glucocorticoid response elements. Southern blot analysis with an amplified cDNA fragment of 487 bp corresponding to the 5' portion of the mRNA and with a DNA probe from a different portion of the arginine esterase gene indicated the presence of two to three homologous genes in the canine genome while in a previous study a single band was detected using a 400-bp arginine esterase cDNA corresponding to the 3' portion of the mRNA. These results suggest that the arginine esterase gene belongs to a small kallikrein gene family. Arginine esterase mRNA is expressed primarily in the prostate but also at an extremely low level (approximately a thousandfold less) in several other tissues including the liver, the gracilis thigh muscle, the kidney, and the pancreas.

Effects of androgen and antiandrogen treatment on canine prostatic arginine esterase

A series of experiments were conducted to investigate the regulation of the primary secretory protein of the canine prostate, arginine esterase, by androgens and/or new antiandrogen under development. In the first experiment, castration decreased (P less than 0.05) prostatic arginine esterase levels relative to intact controls (0.26 +/- 0.1 and 17.0 +/- 0.1 mumole/min/mg protein, respectively). Treatment of castrate dogs with either 5, 10, or 20 silastic capsules (8 cm length) containing the androgen 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol) plus 1 capsule containing estradiol-17 beta (E2) or the i.m. injection of 25 mg 3 alpha-diol and 0.25 mg E2 for 12 weeks resulted in a dose-dependent increase (P less than 0.05) in prostatic arginine esterase activity (6.8 +/- 1.7, 19.0 +/- 3.6, 21.3 +/- 0.9, and 14.2 +/- 0.7 mumole/min/mg protein, respectively). In the second experiment, steroid treatment (10 3 alpha-diol plus 1 E2 silastic capsules) of castrate dogs for 12 weeks resulted in prostatic arginine esterase activity of 17.8 +/- 2.3 mu mole/min/mg. Co-administration of the steroidal androgen receptor antagonist. Win 49,596 (WIN) at doses of 0.625, 2.5, 10, or 40 mg/kg/day p.o., dose-dependently inhibited (P less than 0.05) prostatic arginine esterase activity (14.9 +/- 1.1, 14.3 +/- 1.3, 3.4 +/- 1.9, and 0.21 +/- 0.1 mumole/min/mg, respectively) to levels similar to that observed in castrate controls (0.14 +/- 0.03 mumole/min/mg). Administration of the nonsteroidal androgen receptor antagonist flutamide at 10 mg/kg/day p.o. to steroid-induced dogs also inhibited (P less than 0.05) arginine esterase activity (0.07 +/- 0.02 mumole/min/mg). In the last experiment, treatment of intact dogs with WIN at 0.625, 2.5, 10, and 40 mg/kg/day for 16 weeks dose-dependently reduced (P less than 0.05) arginine esterase levels (17.0 +/- 1.0, 16.3 +/- 1.5, 10.2 +/- 1.2, and 3.9 +/- 2.5 mumole/min/mg, respectively) compared to intact controls (14.4 +/- 1.2 mumole/min/mg). Histomorphologic and ultrastructural evaluation of prostates from dogs indicated that antiandrogen treatment resulted in glandular epithelial atrophy as well as a reduction in the number of secretory granules. The results of these experiments support that canine prostatic arginine esterase activity is under androgenic control, can be inhibited by antiandrogen treatment and may serve as a functional marker of the androgenic state of the prostate. Whether the effects of androgen and antiandrogens on prostatic arginine esterase is direct or indirect due to a general inhibitory effect on secretory epithelial cell function requires additional study. Furthermore, subject to further evaluation, the steroidal androgen receptor antagonist.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of 2-week combination therapy with the luteinizing hormone-releasing hormone (LHRH) agonist [D-Trp6, des-Gly-NH2(10)]LHRH ethylamide and the antiandrogen flutamide on prostate structure and steroid levels in the dog

Treatment of adult dogs for 15 days with the luteinizing hormone-releasing hormone (LHRH) agonist [D-Trp6, des-Gly-NH2(10)]LHRH ethylamide (50 micrograms daily, s.c.) causes a 41.6% inhibition of prostatic weight while a 55% inhibition is achieved when the antiandrogen flutamide (250 mg, twice daily) is given in association with the LHRH agonist (p less than 0.01). At histology, the glandular acini in the prostate of animals treated with the combination therapy are more atrophied than with either treatment used alone. A 2-week treatment with the LHRH agonist is characterized by two distinct phases, namely a stimulation of testicular androgen secretion between days 0 and 8 followed by an inhibition between days 9 and 15. During the inhibitory phase, the concentration of all testicular steroids progressively decreased to castration levels, thus indicating that the differences observed at the prostatic level at 2 weeks are due to the inhibition of androgen action by the antiandrogen flutamide during the period which precedes complete chemical castration by the LHRH agonist. Flutamide administered alone had no effect on plasma or prostatic steroid levels measured after 2 weeks and it did not interfere with the potent and generalized inhibitory effect of the LHRH agonist on the serum and prostatic concentration of all steroids measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose-dependent hormonal induction of benign prostatic hyperplasia (BPH) in castrated dogs

A model for the dose-dependent hormonal induction of benign prostatic hyperplasia (BPH) in castrated dogs has been established using subcutaneously implanted Silastic capsules containing 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol) and estradiol-17 beta. In vivo release rates per capsule approximated 122.0 +/- 4.2 micrograms 3 alpha-diol and 22.7 +/- 0.8 micrograms estradiol per day based on in vitro studies and resulted in dose-dependent increases in serum 3 alpha-diol and dihydrotestosterone concentrations. The implantation of castrated dogs with either 10 or 20 Silastic capsules containing 3 alpha-diol and one capsule containing estradiol or the intramuscular injection of 3 alpha-diol (75 mg/week) and estradiol (0.75 mg/week) for 99 days significantly increased (P less than .01) prostatic weights and total prostatic DNA over intact controls. These treatments also resulted in a histomorphological pattern similar to that observed in dogs with the glandular form of spontaneous BPH. In addition, normal prostatic secretory function as determined by semen volume was maintained in these dogs. Although subcutaneous implantation of five Silastic capsules containing 3 alpha-diol and one capsule containing estradiol into castrated dogs resulted in prostatic weights and total prostatic DNA that were similar (P less than .10) to intact controls, these prostates were characterized histomorphologically by glandular atrophy and squamous metaplasia. Furthermore, prostatic secretory function was decreased (P less than .05) in these animals compared with intact controls at 3 months of treatment. This study has led to the development of a model of steroid-induced BPH that will facilitate the evaluation of competitive androgen-receptor antagonists in the dog.