Background: Prostate cancer is a frequent finding in man. In dogs, malignant disease of the prostate is also of clinical relevance, although it is a less common diagnosis. Even though there are numerous differences in origin and development of the disease, man and dog share many similarities in the pathological presentation. For this reason, the dog might be a useful animal model for prostate malignancies in man.

Akin to the situation in humans, dogs are frequently affected by tumors of the prostate. The malignancies share many similarities between both species, for example, median age at the onset of the disease and metastatic behavior. In human prostatic tumor samples, investigations of prepared metaphase spreads showed a variety of chromosomal aberrations, with trisomies of chromosomes 7, 8, and 17 as the leading cytogenetic abnormalities. In this article we present one case of a canine adenocarcinoma of the prostate, including clinical examination and establishment of a cell line from a tumor sample obtained from the affected 10-year-old male Briard. Searching for similarities between both species in respect to chromosomal changes within the tumor samples, we investigated prepared metaphases of the canine cell line cytogenetically. These investigations presented a highly rearranged karyotype showing a large biarmed marker consisting of material from chromosomes 1 and 2 in addition to centromeric fusions between dog chromosomes 1 and 5 that both could be identified in every metaphase investigated, while centric fusions of chromosomes 4 and 5 occurred in up to 50% of the metaphases. The cell line grew very well and showed evidence of being spontaneously immortalized when it crossed the 20th passage.

Cell lines are key tools in cancer research allowing the generation of neoplasias in animal models resembling the initial tumours able to mimic the original neoplasias closely in vivo. Canine lymphoma is the major hematopoietic malignancy in dogs and considered as a valuable spontaneous large animal model for human Non-Hodgkin's Lymphoma (NHL). Herein we describe the establishment and characterisation of an in vivo model using the canine B-cell lymphoma cell line CLBL-1 analysing the stability of the induced tumours and the ability to resemble the original material. CLBL-1 was injected into Rag2−/−γc −/− mice. The generated tumor material was analysed by immunophenotyping and histopathology and used to establish the cell line CLBL-1M. Both cell lines were karyotyped for detection of chromosomal aberrations. Additionally, CLBL-1 was stimulated with IL-2 and DSP30 as described for primary canine B-cell lymphomas and NHL to examine the stimulatory effect on cell proliferation. CLBL-1 in vivo application resulted in lymphoma-like disease and tumor formation. Immunophenotypic analysis of tumorous material showed expression of CD45+, MHCII+, CD11a+ and CD79αcy+. PARR analysis showed positivity for IgH indicating a monoclonal character. These cytogenetic, molecular, immunophenotypical and histological characterisations of the in vivo model reveal that the induced tumours and thereof generated cell line resemble closely the original material. After DSP30 and IL-2 stimulation, CLBL-1 showed to respond in the same way as primary material. The herein described CLBL-1 in vivo model provides a highly stable tool for B-cell lymphoma research in veterinary and human medicine allowing various further in vivo studies.

Besides man, the dog is the only known mammalian species that spontaneously develops carcinomas of the prostate with considerable frequency. For this reason, the dog is considered to be the only useful animal model for spontaneously occurring prostate malignancies in man. Cytogenetic investigations of human prostate cancers have revealed the frequent occurrence of trisomies 7, 8, and 17. Chromosome analyses of canine prostate carcinomas are rare. In this report we present 2 cases of canine prostate cancer showing a clonal polysomy 13 along with complex karyotype changes. Along with a previous report demonstrating polysomy 13 as the only karyotype deviation in a canine prostate cancer the present report supports the hypothesis that in canine prostate cancer, polysomy 13 is a recurrent cytogenetic aberration linked to the development of the disease. As human chromosomes (HSA) 8q and 4q and the canine chromosome (CFA) 13 share high homology, these results suggest that a conserved area on these chromosomes is involved in tumorigenesis in both species.

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The architectural transcription factor HMGA2 is abundantly expressed during embryonic development. In several malignant neoplasias including prostate cancer, high re-expression of HMGA2 is correlated with malignancy and poor prognosis. The let-7 miRNA family is described to regulate HMGA2 negatively. The balance of let-7 and HMGA2 is discussed to play a major role in tumour aetiology. To further analyse the role of HMGA2 in prostate cancer a stable and highly reproducible in vitro model system is precondition. Herein we established a canine CT1258-EGFP-HMGA2 prostate cancer cell line stably overexpressing HMGA2 linked to EGFP and in addition the reference cell line CT1258-EGFP expressing solely EGFP to exclude EGFP-induced effects. Both recombinant cell lines were characterised by fluorescence microscopy, flow cytometry and immunocytochemistry. The proliferative effect of ectopically overexpressed HMGA2 was determined via BrdU assays. Comparative karyotyping of the derived and the initial CT1258 cell lines was performed to analyse chromosome consistency. The impact of the ectopic HMGA2 expression on its regulator let-7a was analysed by quantitative real-time PCR. Fluorescence microscopy and immunocytochemistry detected successful expression of the EGFP-HMGA2 fusion protein exclusively accumulating in the nucleus. Gene expression analyses confirmed HMGA2 overexpression in CT1258-EGFP-HMGA2 in comparison to CT1258-EGFP and native cells. Significantly higher let-7a expression levels were found in CT1258-EGFP-HMGA2 and CT1258-EGFP. The BrdU assays detected an increased proliferation of CT1258-HMGA2-EGFP cells compared to CT1258-EGFP and native CT1258. The cytogenetic analyses of CT1258-EGFP and CT1258-EGFP-HMGA2 resulted in a comparable hyperdiploid karyotype as described for native CT1258 cells. To further investigate the impact of recombinant overexpressed HMGA2 on CT1258 cells, other selected targets described to underlie HMGA2 regulation were screened in addition. The new fluorescent CT1258-EGFP-HMGA2 cell line is a stable tool enabling in vitro and in vivo analyses of the HMGA2-mediated effects on cells and the development and pathogenesis of prostate cancer.

SummaryCytogenetics is the study of normal and abnormal chromosomes. Every species is characterized by a given number of chromosomes that can be recognized by their specific shape. The chromosomes are arranged according to standard classification schemes for the respective species. While pre-and postnatal chromosome analyses investigate the constitutional karyotype, tumor cytogenetics is focused on the detection of clonal acquired, tumor-associated chromosome aberrations. Cytogenetic investigations in dogs are of great value especially for breeders dealing with fertility problems within their pedigrees, for veterinarians and last but not least for the dog owners. Dogs and humans share a variety of genetic diseases, including cancer. Thus, the dog has become an increasingly important model for genetic diseases. However, cytogenetic analyses of canine cells are complicated by the complex karyotype of the dog. Only just 15 years ago, a standard classification scheme for the complete canine karyotype was established. For chromosome analyses of canine cells the same steps of chromosome preparation are used as in human cytogenetics.There are few reports about cytogenetic changes in non-neoplastic cells, involving predominantly the sex chromosomes. Cytogenetic analyses of different entities of canine tumors revealed that, comparable to human tumors, tumors of the dog are often characterized by clonal chromosome aberrations, which might be used as diagnostic and prognostic markers. The integration of modern techniques (molecular genetic approaches, adaptive computer programs) will facilitate and complete conventional cytogenetic studies. However, conventional cytogenetics is still non-replaceable.

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