Evidence of epithelial–mesenchymal transition in canine prostate cancer metastasis
Introduction
The leading cause of death related to cancer in the Western world is metastasis, which represents a final stage of the disease and is associated with a poor prognosis (Pani et al., 2010). Death of patients with metastasis occurs due to failure of the affected tissues, concomitant paraneoplastic syndromes and metabolic changes (Steeg, 2006). Metastasis is a very complex process. Information about metastasis in humans has increased over the years (Pani et al., 2010) but is still limited in veterinary medicine.
Other than humans, dogs are the only species that naturally develops prostatic carcinoma (PCa) with high frequency (Fonseca-Alves et al, 2013a, Palmieri et al, 2014). In dogs, PCa is highly metastatic, and the disease is usually at an advanced stage at diagnosis (Argyle, 2009, Fonseca-Alves et al, 2013b). Many studies from the human cancer literature have described a correlation between the epithelial–mesenchymal transition (EMT) and human PCa (Brabletz, 2012, Frederick et al, 2007, Mani et al, 2008, Thiery et al, 2009). The EMT is an important process in the biology of metastasis. During the EMT, epithelial cells lose their polarity and cell–cell adhesion function and gain invasive and migratory properties (Mani et al., 2008). In this process, the cellular–extracellular matrix interactions and the cellular cytoskeleton are modified to confer migratory and invasive abilities (Radisky, 2005). The EMT and its converse process, the mesenchymal–epithelial transition (MET), are crucial to the carcinogenic process (Frederick et al., 2007).
The E-cadherin/β-catenin complex plays an important role in cell-to-cell adhesion. These molecules are associated with the canonical WNT signalling pathway in human prostate cancer (Schmalhofer et al., 2009). E-cadherin and β-catenin are associated with the epithelial tissue phenotype and are responsible for regulating cell migration and differentiation (Comijn et al., 2001). In the carcinogenic process in epithelial tissues, the absence of these molecules is associated with the invasion of adjacent tissues and metastasis implantation (Schmalhofer et al., 2009).
Loss of E-cadherin protein expression is associated with high-grade prostate cancer in humans, and these tumours demonstrate a metastatic phenotype (Graff et al., 1995). The localisation of β-catenin plays an important role in cell proliferation. When β-catenin is localised in the membrane, it is responsible for cell-to-cell adhesion and has an important role in the cytoskeleton (Schmalhofer et al., 2009). In the metastatic process of human PCa, cancer cells lose E-cadherin and develop β-catenin nuclear staining (Graff et al., 1995). The translocation of membranous β-catenin to the nucleus activates the WNT pathway and promotes cell proliferation.
In veterinary medicine, there are few studies on the EMT in PCa. Changes in E-cadherin (Fonseca-Alves et al, 2013a, Rodrigues et al, 2013), β-catenin (Lean et al, 2014, Rodrigues et al, 2013) and vimentin (Grieco et al, 2003, Lean et al, 2014, Rodrigues et al, 2011) expression were previously described in canine PCa, but these markers have not been evaluated in metastatic prostate carcinomas.
Due to the importance of metastasis to the treatment protocol and survival time of patients, this research aimed to verify evidence of the EMT in canine pre-neoplastic prostate lesions and in prostate carcinomas and their metastases.
Section snippets
Animal data
A total of 36 paraffin blocks from 24 intact adult dogs (aged 1–15 years) with a clinical history of prostate lesions were obtained from the archives of the Pathology Service at Univ. Estadual Paulista. The samples included prostate lesions from five normal prostate cases, five benign prostate hyperplasia (BPH) cases, two prostatic intraepithelial neoplasia (PIN) cases, three prostatic inflammatory atrophy (PIA) cases, five non-metastatic PCa cases, four metastatic PCa cases and 12 metastatic
Clinical data
Five dogs were diagnosed with BPH associated with dyschezia and tenesmus; five dogs were diagnosed with non-metastatic carcinoma associated with dyschezia, tenesmus, haematuria and dysuria; and four dogs were diagnosed with metastatic carcinomas. The dogs with metastatic carcinomas demonstrated dyschezia, tenesmus, haematuria, dysuria, dyspnoea, pain in the lumbosacral region and gait changes in the hind limbs. The most common locations of metastatic foci were the lungs (n = 4) and bone (sacral
Discussion
Our results demonstrated a trend towards a lower survival time among the dogs with metastasis compared with the dogs without metastasis at the time of diagnosis. All of the animals with metastatic disease had metastases in the lung and bone, which are common sites of metastases in humans (Yonou et al., 2001). Lawrence and Saba (2013) described a poor prognosis for dogs with metastatic PCa: dogs with a diagnosis of PCa without treatment showed a survival time of less than 30 days or were
Conclusions
The loss of E-cadherin and the translocation of β-catenin from the membrane to the cytoplasm/nucleus are important events in the invasion and metastatic processes of canine metastatic prostate carcinomas. Vimentin is also important in the carcinogenic process of canine prostate carcinomas. In the present study, the normal and hyperplastic tissues were negative for vimentin, the pre-neoplastic lesions had the same number of vimentin-positive cells as the control, and the tumours had the highest
Acknowledgements
We thank the São Paulo Research Foundation (FAPESP) for their financial support (Grant No. 2010/13774-6, No. 2012/16426-1, and No. 2012/16068-0).
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