Role of adhesion molecules and proliferation hyperplasic, pre neoplastic and neoplastic lesions in canine prostate

Molecular Similarities and Differences between Canine Prostate Cancer and Human Prostate Cancer Variants

Dogs are one of few species that naturally develop prostate cancer (PCa), which clinically resembles aggressive, advanced PCa in humans. Moreover, PCa-tumor samples from dogs are often androgen receptor (AR)-negative and may enrich our understanding of AR-indifferent PCa in humans, a highly lethal subset of PCa for which few treatment modalities are available This narrative review discusses the molecular similarities between dog PCa and specific human-PCa variants, underscoring the possibilities of using the dog as a novel pre-clinical animal model for human PCa, resulting in new therapies and diagnostics that may benefit both species.

A Review on Canine and Feline Prostate Pathology

Prostatic diseases are very common in male dogs, accounting for 3–10% of cases submitted to the veterinary practitioners. Commonly reported canine prostatic disorders include prostatic hyperplasia, prostatitis, prostatic cysts and prostatic carcinoma. However, clinical signs may be non-specific, or many cases are asymptomatic, thus leading to a difficult estimation of the actual prevalence of clinical cases. On the other side, because of the rare occurrence of prostate disease in cats, very little is known about pathogenesis, diagnostic approaches and treatment. The goal of this review is to provide detailed clinical and pathological overview of the feline and canine prostatic pathology, including the most up-to-date classification systems and histological findings. Emphasis is places on gross, cytological and histological features that are critical to reach a definitive diagnosis for a proper treatment and prognosis.

Comparative Pathobiology of Canine and Human Prostate Cancer: State of the Art and Future Directions

First described in 1817, prostate cancer is considered a complex neoplastic entity, and one of the main causes of death in men in the western world. In dogs, prostatic carcinoma (PC) exhibits undifferentiated morphology with different phenotypes, is hormonally independent of aggressive character, and has high rates of metastasis to different organs. Although in humans, the risk factors for tumor development are known, in dogs, this scenario is still unclear, especially regarding castration. Therefore, with the advent of molecular biology, studies were and are carried out with the aim of identifying the main molecular mechanisms and signaling pathways involved in the carcinogenesis and progression of canine PC, aiming to identify potential biomarkers for diagnosis, prognosis, and targeted treatment. However, there are extensive gaps to be filled, especially when considering the dog as experimental model for the study of this neoplasm in humans. Thus, due to the complexity of the subject, the objective of this review is to present the main pathobiological aspects of canine PC from a comparative point of view to the same neoplasm in the human species, addressing the historical context and current understanding in the scientific field.

Association between decreased expression of estrogen receptor alpha, androgen receptor and phosphatase and tensin homolog immunoexpression in the canine prostate

ABSTRACT: Canine prostate gland is a hormonal dependent organ and its imbalance of estrogen and androgen receptor expressions are directly associated with the development of different diseases. Due to the lack of information regarding the behavior of the aforementioned receptors in canine prostate cancer (PC), this study aimed to identify estrogen receptor alpha (ERα), androgen receptor (AR), Ki67 and phosphatase and tensin homolog (PTEN) protein expressions in canine PC by immunohistochemistry. We found nuclear expression of ERα and AR in the epithelial cells of normal canine samples and a loss of protein expression in PC samples. Normal samples showed Ki67 expression in a few basal cells and the PC samples showed the highest mean of positive cells (253.1). Canine prostate cancer showed a high proliferative index, which was associated with independence of hormonal actuation. PTEN showed positive nuclear and cytoplasmic expression in normal canine samples and a loss in PC. Loss of ERα, AR and PTEN indicated that canine PC exhibits the same immunohistochemical phenotype as in human patients with PC resistant to hormonal therapy. Therefore, canine PC should be considered as a model to study human PC resistant to hormonal therapy.

Deregulation of E-cadherin, β-catenin, APC and Caveolin-1 expression occurs in canine prostate cancer and metastatic processes

Prostate cancer is a heterogeneous disease with high levels of clinical and gene heterogeneity, consequently offering several targets for therapy. Dogs with naturally occurring prostate cancer are useful models for molecular investigations and studying new treatment efficacy. Three genes and proteins associated with the WNT pathway (β-catenin, APC and E-cadherin) and Caveolin-1 (CAV-1) were evaluated in canine pre-neoplastic proliferative inflammatory atrophy (PIA), prostate cancer and metastatic disease. The APC gene methylation status was also investigated. As in human prostate cancer, cytoplasmic and nuclear β-catenin, which are fundamental for activating the canonical WNT pathway, were found in canine prostate cancer and metastasis. Membranous E-cadherin was also lost in these lesions, allowing cellular migration to the stroma and nuclear localization of β-catenin. In contrast to human prostate tumours, no APC downregulation or hypermethylation was found in canine prostate cancer. The CAV-1 gene and protein overexpression were found in canine prostate cancer, and as in humans, the highest levels were found in Gleason scores ≥8. In conclusion, as with human prostate cancer, β-catenin and E-cadherin in the WNT pathway, as well as Caveolin-1, are molecular drivers in canine prostate cancer. These findings provide additional evidence that dogs are useful models for studying new therapeutic targets in prostate cancer.

Diagnostic Utility of Cytokeratin-5 for the Identification of Proliferative Inflammatory Atrophy in the Canine Prostate

Proliferative inflammatory atrophy (PIA), which is comprised of highly proliferative but atrophic prostate epithelial cells in association with chronic inflammation, is considered a risk lesion for prostate cancer in men, while its role in canine prostate carcinogenesis is still unknown. We evaluated the value of immunohistochemical labelling for the basal cell marker cytokeratin-5 (CK5) in identifying PIA lesions in 87 samples of formalin-fixed and paraffin wax-embedded canine prostate. Canine PIA showed cytological features identical to the human counterpart and in most cases was associated with chronic lymphoplasmacytic inflammation. PIA lesions were identified in a higher number of CK5-labelled slides (43 out of 87) compared with slides stained by haematoxylin and eosin (HE) (24 out of 87). This lesion was frequently present in normal, hyperplastic and neoplastic canine prostates, although it was underestimated on evaluation of HE-stained slides. Therefore, CK5 can be considered a useful basal cell marker with high sensitivity and specificity for PIA.

Evidence of epithelial-mesenchymal transition in canine prostate cancer metastasis

The epithelial-mesenchymal transition (EMT) is a fundamental event responsible for the invasiveness and metastasis of epithelial tumours. The EMT has been described in many human cancers, but there are few reports of this phenomenon in veterinary oncology. Due to the importance of this process, the current study evaluated mesenchymal and epithelial marker protein expression in prostate lesions from dogs. Our results indicate both a loss of E-cadherin and translocation of β-catenin from the membrane to the cytoplasm and nucleus in the tumour group. Vimentin expression in the tumour group was higher than in normal tissue. All of the metastases were positive for prostate-specific antigen, pan-cytokeratin and E-cadherin, although fewer positive cells were present than in the primary tumours. The immunohistochemical results showed a loss of epithelial markers and a gain of a mesenchymal marker among metastatic cells, suggesting that the EMT occurs during the metastatic process of canine prostate carcinoma.

Alterations of C-MYC, NKX3.1, and E-cadherin expression in canine prostate carcinogenesis

The dog (canis lupus familiaris) is the only other species besides humans that develop spontaneous prostatic carcinomas (PCa) at a high frequency. The canine model is primarily utilized for the study of the PCa molecular mechanisms and provides a natural animal model for the study of potential therapies. In humans, the PCa frequently exhibits mutations in the C-MYC and a reduced expression of the E-cadherin and NKX3.1 proteins. This study's objective was to evaluate the NKX3.1, C-MYC, and E-cadherin expression in the canine normal prostate, benign prostatic hyperplasia (BPH), proliferative inflammatory atrophy (PIA) and PCa and to verify differences in expression and subcellular localization of these proteins in the prostatic carcinogenesis. A tissue microarray (TMA) slide was constructed, and immunohistochemistry with antibodies raised against C-MYC, NKX3.1, E-cadherin and p63 was performed using the peroxidase and DAB methods. The C-MYC protein expression was elevated in the cytoplasm and nuclei of the canine PCa and PIA compared with the normal prostate (P = 0.004. The NKX3.1 protein expression was reduced in 94.75% of the PCa and 100% of the PIA compared with the normal prostate (P = 0.0022). In fact, the expression of E-cadherin trended towards a decrease in carcinomas when compared to normal prostate and PIA. By immunohistochemistry, more p63-positive basal cells were observed in the PCa and PIA when compared with the normal prostate (P = 0.0002). This study has demonstrated that the carcinogenesis of canine prostatic tissue may be related to basal cell proliferation, the gain of C-MYC function and the loss of NKX3.1 protein expression.