Catechol-o-methyltransferase genotypes are associated with progression and biological behaviour of canine mammary tumours

Prognostic Factors for Cancer-Specific Survival and Disease-Free Interval of Dogs with Mammary Carcinomas

Canine mammary tumors (CMTs) are the most diagnosed neoplasms in dogs; however, there are few studies analyzing the influence of epidemiological, clinicopathological, and histopathological data on cancer-specific survival (CSS), disease-free interval (DFI), and overall survival (OS) in a large cohort. To contribute to the understanding of the biological behavior of this neoplasm, 385 cases were analyzed, 89% malignant, 4% benign, and 7% non-neoplastic lesions. Among the dogs diagnosed with malignant neoplasms, 86% had early clinical stages (I-III), while 14% had regional or distant metastasis at the time of diagnosis. Carcinoma in a mixed tumor was the most frequent histological type with 44% of the cases and had the best prognosis. Analyzed factors such as the presence of pseudocyesis, previous history of the disease, advanced clinical stage (IV-V), and presence of ulceration obtained significant results for CSS, DFI, and OS through univariate analysis and had a negative impact on the survival of the patients. Multivariate analysis showed that histological grading and age proved to be the best independent parameters for the prognostic evaluation of CSS and DFI in this study. These factors were also significant in the overall survival analysis. Therefore, these parameters should be considered valuable risk and prognostic factors for CMTs.

Protective Effect of HER2 Gene Polymorphism rs24537331 in the Outcome of Canine Mammary Tumors

The role of HER2 in canine mammary tumors is not completely elucidated, and the contradictory results published so far may be, in part, explained by the genetic variability recognized in the canine HER2 gene. Single nucleotide polymorphism (SNPs) in HER2 were recently associated with less aggressive canine mammary tumor histotypes. This study assesses the relationship between SNPs rs24537329 and rs24537331 in canine HER2 gene and clinicopathological characteristics and outcome of mammary tumors in a group of 206 female dogs. Allelic variants were observed in 69.8% and 52.7% of the dogs for SNP rs24537329 and rs24537331, respectively. Our results demonstrated that SNP rs24537331 was associated with decreased tumoral necrosis (HR: 3.09; p = 0.012) and with longer disease-specific overall survival (HR: 2.59; p = 0.013). However, no statistically significant associations were found between SNP rs24537329 and the tumors' clinicopathological characteristics or survival. Our data suggest that SNP rs24537331 may have a protective effect in canine mammary tumors, allowing the identification of a subgroup of animals prone to develop less aggressive forms of the disease. This study emphasizes the importance of the genetic tests associated with clinical images and histological examinations when assessing CMT outcomes.

Single Nucleotide Polymorphism in Prolactin Gene Is Associated With Clinical Aggressiveness and Outcome of Canine Mammary Malignant Tumors

Prolactin (PRL) is a key hormone involved in canine mammary development and tumorigenesis. In this study, the influence of a single nucleotide polymorphism (SNP) in the PRL gene (rs23932236) on the clinicopathological parameters and survival of dogs with canine mammary tumors (CMTs) was investigated. A total of 206 female dogs with spontaneous mammary tumors were enrolled in this study and circulating blood cells were genotyped. This specific SNP was associated with larger size (>3 cm diameter) for malignant tumors (P = .036), tumors with infiltrative/invasive growth pattern (P = .010), vascular invasion (P = .006), and lymph node metastasis (P = .004). Carriers of the variant allele had a shorter overall survival compared to the wild-type population with an overall survival of 18.7 months and 22.7 months, respectively (P = .004). These findings suggest that SNP rs23932236 of canine PRL gene may be used as an indicator for the development of clinically aggressive forms of CMTs.

Hormonal Carcinogenesis in Canine Mammary Cancer: Molecular Mechanisms of Estradiol Involved in Malignant Progression

Mammary cancer is a frequent neoplasia in female dogs, in which most important risk factors are hormonal. Sexual hormones as estradiol play an important role in mammary carcinogenesis, being able to induce carcinogenic initiation, promotion and progression. However, the molecular mechanisms involved are incompletely understood. Estradiol is synthesized mainly in the ovaries, nevertheless, high concentrations of estradiol and some of its hormonal precursors have also been described in malignant mammary tumor tissue. The mechanisms of action of estradiol include the classic genomic effects that modulate gene transcription, and non-genomic effects, which trigger quick effects after estradiol binds to its specific receptors. These responses modulate various intracellular signaling pathways, triggering post-translational modification of several proteins. This review will discuss the well-known underlying mechanisms associated with the action of estradiol in the malignant progression of canine mammary tumors.

A modern look at the molecular-biological mechanisms of breast tumours in dogs

High morbidity and increase in the number of registrations of breast tumours in dogs, their wide application as biological models, discussion of numerous questions of oncogenesis, and the lack of a uniform/unified methodological approach to the study of molecular and biological mechanisms of treatment of cancer determine the relevance of the problem of cancer both in humans and in our domestic companions. The analysis of publications allowed us to establish the following patterns of carcinogenesis. The peculiarities of the biological behaviour of breast tumours depend on their pathomorphological structure. Genetic predisposition to breast cancer is characteristic only in the single breed aspect. Environmental factors are of critical relevance to carcinogenesis : chemical pollutants initiate oncogenesis indirectly – by altering the expression of several receptors, impaired endocrine balance and direct mutagenic effects. Reproductive status plays a key role in the initiation and progression of breast tumours by reducing the expression of estrogen, progesterone and prolactin receptor genes. The inflammatory response that accompanies the neoplasia process is characterized by increased production of cytokines, cyclooxygenase-2, interleukins (IL-1, IL-6, IL-8), vascular endothelial growth receptors, and impaired hemostatic status (oxidative stress), which promotes progression of disease. In breast cancer in dogs, genomic instability leads to genomic aberrations, and subsequently, mutations that support the proliferation, survival and dissemination of neoplastic cells. The initiation and progression of mammary gland tumours is provided by cancer stem cells by disrupting the regulation of precursor cell self-renewal, which also predispose to resistance to chemotherapeutic agents, radiation, and hormonal cancer therapy. The analysis of the publications revealed the major markers of carcinogenesis that could potentially be used as biological targets for the design of modern diagnostic strategies and high-performance therapeutic protocols.

Estrogen receptors genotypes and canine mammary neoplasia

BACKGROUND

Estrogens are essential for the development and proper function of several hormone-dependent organs. There are, however, several lines of evidence associating estrogens with mammary carcinogenesis. A marked individual genetic variability concerning estrogens biosynthesis, metabolism and mechanism of action was recognized and associated with human breast cancer susceptibility, clinical features and progression. Although some genetic variations in canine ESR1 gene were reported, their influence in clinicopathological features and progression of canine mammary tumors has not been fully evaluated. This study aims to assess the influence of SNPs in ESR1 gene (rs397512133, rs397510462, rs851327560, rs397510612, rs852887655, rs852684753 and rs852398698) in canine mammary tumors characteristics and progression. A group of 155 non-neutered bitches with mammary tumors was included in the study. Follow-up information was assessed 24 months after surgery.

RESULTS

Genetic profiles associated with a later onset of mammary tumors and less aggressive clinicopathological features, namely smaller tumor size (≤ 3 cm) with extensive tubular differentiation and low canine-adapted prognostic index (vet-NPI), were identified in this study.

CONCLUSIONS

Our data suggest that the ESR1 genetic profile may help on the decision regarding the selection of individual tailored preventive measures against canine mammary tumors development, such as early neutering.