Project description:Proliferation, dedifferentiation, loss of cell-cell contacts and angiogenesis are among the first steps of the metastasis cascade. The complex molecular pathways associated with these events in canine mammary tumors are mostly unknown and the value of this spontaneous canine tumor as a comparative model for human breast cancer is therefore still under debate. Messenger RNA profiles of lymph-node positive canine mammary carcinomas and normal mammary glands of the same dogs were compared by microarray analysis to elucidate molecular pathways associated with metastatic progression. Differential gene expression was analyzed by gene set enrichment and pathway analysis and compared with the gene expression data of human breast cancer. Metastatic canine carcinomas had 1,312 significantly differentially expressed genes when compared to the corresponding normal mammary gland. This expression profile included a significantly increased expression of cell division and extracellular matrix invasion genes (MMP1, MMP11, MMP13, SERPINE1, TFPI2, TIMP3). In contrast, genes associated with epithelial differentiation (EGF, EGFR, KRT17, MAP2K6, STAT5), cell adhesion (CLDN5, CLDN8, CTNNAL1, MCAM, MUC1, PECAM1) and angiogenesis (ANGPT2, ANGPTL1, ANGPTL2, ANGPTL4, FGFR1, FIGF, TIE1) were mostly down-regulated. Interestingly, tumors had a significant decrease in membrane receptors and growth factor pathway gene expression (EGFR, FGFR1, GHR, LYVE1, PDGFR, PDGFR, TGFBR, TIE1), indicating a potential independence from these proliferative stimuli. Several of the identified deregulated pathways overlap with gene expression profiles of human breast cancer. Gene expression profiling of metastatic carcinomas therefore identified complex molecular pathways and functional gene families that are deregulated during malignant progression in the tumors. This study provides new insights into canine mammary tumor metastasis and suggests that canine mammary tumors may serve as a valuable model for the human disease. 13 simple mammary carcinomas with lymph node metastases at the time of tumor resection were compared with the non-neoplastic mammary gland of the same dogs. Sufficient amounts of normal mammary gland were not available for dogs no. 1 (822) and 9 (61). In addition, one normal sample without matching tumor sample was analyzed (no. 8; 2609). All patients had no radiographically detectable pulmonary metastases at the time of tumor resection. Postoperative survival was analyzed by bi-yearly telephone interviews with the owners or the attending veterinarian. Distant metastases as the cause of death were determined postoperatively by radiographic detection of metastases (nos. 1-7, 9-12) or necropsy (nos. 13 and 14). Necropsy was not authorized by the owners of dogs nos. 1-7 and 9-12. Tissue specimens of tumors and lymph node metastases were fixed in neutral-buffered 4% formalin or snap frozen in liquid nitrogen within 15 minutes after resection and stored at -80ºC until further use. Formalin-fixed tumor tissue samples were routinely embedded in paraffin and sections of 2-μm thickness were mounted on adhesive glass slides and stained with hematoxylin and eosin. Tumors and lymph nodes were evaluated histologically independently by two board-certified pathologists, following the criteria of the WHO classification of canine mammary tumors (Misdorp et al. 1999).

Project description:Mammary cancer is the most common type of cancer in female dogs with a lifetime risk of over 24% when dogs are not spayed. The elucidation of the complete canine genome opens new areas for development of cancer therapies. These should be tested first by in vitro models such as cell lines. However, to date, no canine mammary cell lines have been characterized by expression profiling. In this study, canine mammary tumour cell lines with histologically distinct primary tumours of origin were characterized using a newly developed canine cDNA microarray. Comparisons of gene expression profiles showed enrichment for distinct biological pathways and were related to biological properties of the cell lines such as growth rate and in vitro tumourigenicity. Additionally, gene expression profiles of cell lines also showed correspondence to their tumour of origin. Major differences were found in Wnt, cell cycle, cytokine/Rho-GTPase, alternative complement and integrin signalling pathways. Because these pathways show an overlap at the molecular level with those found in human breast cancer, the expression profiling of spontaneous canine mammary cancer may also function as a biological sieve to identify conserved gene expression or pathway profiles of evolutionary significance that are involved in tumourigenesis. These results are the basis for further characterization of canine mammary carcinomas and development of new therapies directed towards specific pathways. In addition these cell lines can be used to further investigate identified deregulated pathways and characterize until now unannotated genes. Keywords: cell line type comparision Three canine mammary tumor cell lines (CMT) originating from benign mixed tumor (CMT-U229), primary mammary osteosarcoma (CMT-U335) and primary mammary anaplastic carcinoma (P114) were compared directly to each other in this study. Total RNA was isolated from cells grown to near confluence. In vitro transcription followed by labeling and hybridization to cDNA microarray was carried out. In a loop design of hybridization, labeled cRNA from cell lines were hybridized against each other. Statistical analysis of the log transformed normalized data was done using SAM (significance analysis of microarray) and differentially expressed genes from each experimental subset (comparison of two cell lines) were identified. Dye swaps and at least one biological replicates were included under each experimental subset (each comparision).

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