Characterisation of genome-wide structural aberrations in canine mammary tumours using single nucleotide polymorphism (SNP) genotyping assay.

Characterisation of copy number variation (CNV) and loss of heterozygosity (LOH) has pro- vided evidence for the relationship of this type of genetic variation with the occurrence of a broad spectrum of diseases, including cancer lesions. The role of CNVs and germinal or somatic LOHs in canine mammary tumours is still unknown. Therefore, the aim of this study was to identify CNVs and LOHs in canine mammary tumours. Forty-eight samples obtained from normal (n=24) and tumour (n=24) tissues of dogs were analysed. In the study, we used CanineHD BeadChip assay (Illumina) and OncoSNP software to identify copy number alternations in genomes of dif- ferent dog breeds and in different mammary cancer types occurring in this species. The analyses revealed that, in the case of CNV, the amplification-type variants were longer and more frequent than deletions. Based on the analysis of the frequency of different types of aberrations in the in- dividual parts of the genome, regions that are particularly susceptible to structural aberrations were indicated. The fraction of genes identified within these regions was associated with major processes of neoplastic transformation. Association analysis of such traits as tumour grading as well as the size and age of dogs demonstrated that structural aberrations were more frequent in dogs diagnosed with tumour malignancy grade II and III, in dogs with a larger body size, and in large dogs aged 7-8. The promising results of these pioneering investigations prompt continuation thereof to analyse other types of cancer.

Epidemiological Study of Canine Mast Cell Tumours According to the Histological Malignancy Grade.

The aim of the study was to identify significant relationships between the tumour malignancy grade and dogs' age, breed, sex, size, and location of mast cell tumours (MCTs). MCTs accounted for 13.27% of all diagnosed canine skin tumours. The highest incidence was recorded among Boxers, Labrador Retrievers, American Staffordshire Terriers, and Golden Retrievers. Statistical analysis revealed significantly higher probability of occurrence of the grade I mast cell tumour in the French Bulldog in the head, neck, torso, and limb regions, the grade-II mast cell tumour in Boxer, Doberman, Dachshund, shepherds, and setters in the scrotal region, and the grade III mast cell tumour in Shar-Pei in the axilla region. In the group of the oldest dogs aged 11-16, there was higher risk of development of MCTs grade II and III. Young dogs (aged 2-3 and 4-6) were found to be more prone to development of MCTs grade I. There was no correlation between MCTs grade and dogs' sex and size. To the authors' knowledge this is the first report on statistical relationships between the degree of mast cell tumour malignancy and dogs' phenotypic traits, age and tumour location. This analysis indicate predilections for development of the particular mast cell tumour malignancy degrees in certain dog breeds, age, and anatomical location.

Defect of the mitochondrial DNA hypervariable region as a risk factor for canine mammary tumour.

The aim of this study was to identify mutations in the hypervariable region of mitochondrial DNA in canine mammary tumours and to determine their association with the process of neoplastic transformation. A total of 93 biological samples, including blood as well as normal and neoplastic tissue samples from 31 dogs with diagnosed malignant canine mammary tumours were analysed. DNA extraction, amplification and sequencing of the D-loop as well as bioinformatic and statistical analyses were performed. In the mitochondrial D-loop sequence, 26 polymorphic loci and 5 mutations were identified. For the first time, D-loop length heteroplasmy was detected in dogs with mammary tumours. The malignancy grade exerted no effect on the presence of nucleotide changes. A statistically significant association between the presence of mutations and polymorphisms and the size of dogs was demonstrated. The 100% frequency of length heteroplasmy may imply that this is a hotspot mutation of canine mammary tumour.

Defect in ND2, COX2, ATP6 and COX3 mitochondrial genes as a risk factor for canine mammary tumour.

The aim of this study was to identify mutations in ND2, COX2, ATP6 and COX3 mitochondrial genes in canine mammary tumour, determine their association with the process of neoplastic transformation, and phenotypic traits of dogs. In total, 93 biological samples, including blood, normal and neoplastic tissue samples from 31 dogs with diagnosed malignant canine mammary tumours were analysed. DNA sequencing of genes as well as bioinformatics and statistical analyses were performed. A total of 28 polymorphic loci and 11 mutations were identified. One of the mutations was blood heteroplasmy and two of the mutations caused an amino acid change in p.N117S and p.A184T. For the first time, mutations in mitochondrial genes were detected in dogs with mammary tumours. A statistically significant association between the presence of mutations and the size and age of dogs was demonstrated. Some of these changes may imply that these are the hotspot mutations of canine mammary tumour.

Relevance of Molecular Changes in the ND4 Gene in German Shepherd Dog Tumours.

The aim of the study was to identify polymorphisms and mutations in the mitochondrial ND4 gene and to analyse the associations between the occurrence of molecular changes in mtDNA and phenotypic traits in tumours in German Shepherd dogs. Fifty samples obtained from blood and tumour tissues of German Shepherd dogs with diagnosed tumours were analysed. DNA extraction, amplification, and sequencing of the mtDNA ND4 gene, and bioinformatics, statistical, and in silico protein coding SNP analyses were performed. ND4 mutations and/or polymorphisms were noted in eleven nucleotide positions in nearly half of the examined dogs. All the changes were substitution mutations. A majority of the changes identified were homoplasmic. In one dog with osteosarcoma, blood heteroplasmy was detected. In two positions of the ND4 gene, presence of non-synonymous mutations leading to amino acid changes in the ND4 protein was reported. Analyses carried out to determine the deleterious effect of mutations indicated an almost 97 and 62% probability that a single amino acid substitution (p.G239V and p.I401T, respectively) in the protein has a negative impact on its function. The results of statistical analyses indicate a significant association between the occurrence of mutations in three loci of the ND4 gene and the location of tumours. The mutations identified may be a result of cell adaptation to the changes in the environment occurring during carcinogenesis. The high frequency of mutations in the tumours may indicate genetic instability of mtDNA, which may also play a role in carcinogenesis.