Establishment and Characterisation of Two Canine Prostate Cancer Cell Lines with Stem Cell Marker Expression.

Canine prostatic adenocarcinoma is a rare but highly aggressive cancer that is typically diagnosed at an advanced stage, due to the lack of effective screening methods and poor recognition of early lesions. Cancer stem cells are known to drive tumour progression and treatment resistance in human prostate cancer, but their role in naturally occurring canine disease remains poorly defined. A deeper understanding of the biology of canine prostatic adenocarcinoma is therefore essential to improve prognosis and to develop relevant comparative models. We established and comprehensively characterised two novel canine prostatic adenocarcinoma cell lines, Kodiak and Bobby, with detailed comparison to their tumours of origin and, for Kodiak, xenografts generated in immunodeficient mice. Both lines displayed variable epithelial morphology influenced by culture conditions, and Kodiak xenografts recapitulated key histopathological patterns of the primary tumour. Expression of the luminal epithelial marker CK8/18 and the basal marker CK14 was largely retained across tumour, cell line, and xenograft, whereas the basal markers CK5 and p63, and the urothelial marker UPIII, were diminished or lost during in vitro culture. Evaluation of cancer stem cell-associated markers showed consistent expression of CD44, Nanog, Oct3/4, and Sox2 in the original tumours and cell lines, while CD133, Nestin, and Trop2 were present in the tumours but absent in vitro, indicating selective loss of specific stem-like populations. Media-dependent plasticity was evident in the Bobby line. These models retain key epithelial and stemness features and provide robust platforms for translational prostate cancer research in dogs and humans.