Immunohistochemical investigation of the stem cell landscape of canine prostate cancer.

Prostate cancer is aggressive in dogs and characterized by limited therapeutic responsiveness and a poor prognosis. While cancer stem cells (CSCs) are increasingly recognized as key drivers of tumour progression, therapeutic resistance and metastasis in human prostate cancer, their role in canine prostate cancer remains poorly defined. This study aimed to characterize the expression of stem cell-associated markers in canine prostatic adenocarcinoma by assessing a broad panel of CSC-associated markers in primary prostate tissues. Immunohistochemistry evaluated the expression and subcellular localization of seven CSC-associated markers (CD44, CD133, Nanog, Nestin, Oct3/4, Sox2 and Trop2) in non-neoplastic canine prostate samples and prostatic adenocarcinoma cases. Marker expression was semiquantitatively assessed and differences between groups analysed using non-parametric statistical tests. Neoplastic prostatic tissue demonstrated significantly increased immunolabelling of CD44, CD133, Nanog (nuclear and cytoplasmic), Nestin (nuclear and cytoplasmic), Oct3/4 (cytoplasmic), Sox2 (cytoplasmic) and Trop2 compared with non-neoplastic prostate tissue (P <0.05). In contrast, nuclear Oct3/4 and nuclear Sox2 immunolabelling did not differ significantly between groups. Distinct patterns of nuclear and cytoplasmic localization were observed for several markers, suggesting context-dependent regulation and potential functional heterogeneity within CSC-like populations. These findings demonstrate that canine prostatic adenocarcinomas have multiple stem cell-associated markers, consistent with the presence of a stemness-associated phenotype within these tumours.