Evaluation of Clinicopathological Characteristics and Oestrogen Receptor Gene Expression in Oestrogen Receptor-negative, Progesterone Receptor-positive Canine Mammary Carcinomas

Mammary neoplasms in female dogs: Clinical, diagnostic and therapeutic aspects

With the increase in the life expectancy of domestic animals and their increasingly affectionate relationship with their owners, it is possible to observe an increase in cases of neoplasms in these animals. Mammary neoplasia mainly affects older females who have not been castrated, due to hormonal dependence for the development of the tumour. The main form of treatment is surgery. This study aims to carry out an updated review on mammary neoplasms in female dogs covering the anatomy, physiology, prevalence, causes, diagnoses, treatments, prevention and prognosis, based on scientific articles by renowned researchers.

Profiling canine mammary tumors: A potential model for studying human breast cancer

Despite all clinical progress recorded in the last decades, human breast cancer (HBC) remains a major challenge worldwide both in terms of its incidence and its management. Canine mammary tumors (CMTs) share similarities with HBC and represent an alternative model for HBC. The utility of the canine model in studying HBC relies on their common features, include spontaneous development, subtype classification, mutational profile, alterations in gene expression profile, and incidence/prevalence. This review describes the similarities between CMTs and HBC regarding genomic landscape, microRNA expression alteration, methylation, and metabolomic changes occurring during mammary gland carcinogenesis. The primary purpose of this review is to highlight the advantages of using the canine model as a translational animal model for HBC research and to investigate the challenges and limitations of this approach.

Hormone, Targeted, and Combinational Therapies for Breast Cancers: From Humans to Dogs

Breast cancer (BC) is the most frequent cancer in women. In female dogs, canine mammary gland tumor (CMT) is also the leading neoplasm. Comparative oncology indicates similar tumor behaviors between human BCs (HBCs) and CMTs. Therefore, this review summarizes the current research in hormone and targeted therapies and describes the future prospects for HBCs and CMTs. For hormone receptor-expressing BCs, the first medical intervention is hormone therapy. Monoclonal antibodies against Her2 are proposed for the treatment of Her2+ BCs. However, the major obstacle in hormone therapy or monoclonal antibodies is drug resistance. Therefore, increasing alternatives have been developed to overcome these difficulties. We systemically reviewed publications that reported inhibitors targeting certain molecules in BC cells. The various treatment choices for humans decrease mortality in females with BC. However, the development of hormone or targeted therapies in veterinary medicine is still limited. Even though some clinical trials have been proposed, severe side effects and insufficient case numbers might restrict further explorations. This difficulty highlights the urgent need to develop updated hormone/targeted therapy or novel immunotherapies. Therefore, exploring new therapies to provide more precise use in dogs with CMTs will be the focus of future research. Furthermore, due to the similarities shared by humans and dogs, well-planned prospective clinical trials on the use of combinational or novel immunotherapies in dogs with CMTs to obtain solid results for both humans and dogs can be reasonably anticipated in the future.

Canine Mammary Cancer: State of the Art and Future Perspectives

Mammary cancer is the most frequently diagnosed neoplasia in women and non-spayed female dogs and is one of the leading causes of death in both species. Canines develop spontaneous mammary tumors that share a significant number of biological, clinical, pathological and molecular characteristics with human breast cancers. This review provides a detailed description of the histological, molecular and clinical aspects of mammary cancer in canines; it discusses risk factors and currently available diagnostic and treatment options, as well as remaining challenges and unanswered questions. The incidence of mammary tumors is highly variable and is impacted by biological, pathological, cultural and socioeconomic factors, including hormonal status, breed, advanced age, obesity and diet. Diagnosis is mainly based on histopathology, although several efforts have been made to establish a molecular classification of canine mammary tumors to widen the spectrum of treatment options, which today rely heavily on surgical removal of tumors. Lastly, standardization of clinical study protocols, development of canine-specific biological tools, establishment of adequate dog-specific disease biomarkers and identification of targets for the development of new therapies that could improve survival and have less adverse effects than chemotherapy are among the remaining challenges.

The Novel Diagnostic Techniques and Biomarkers of Canine Mammary Tumors

Canine mammary tumors (CMTs) are considered a serious clinical problem in older bitches. Due to the high malignancy rate and poor prognosis, an early diagnosis is essential. This article is a summary of novel diagnostic techniques as well as the main biomarkers of CMTs. So far, CMTs are detected only when changes in mammary glands are clinically visible and surgical removal of the mass is the only recommended treatment. Proper diagnostics of CMT is especially important as they represent a very diverse group of tumors and therefore different treatment approaches may be required. Recently, new diagnostic options appeared, like a new cytological grading system of CMTs or B-mode ultrasound, the Doppler technique, contrast-enhanced ultrasound, and real-time elastography, which may be useful in pre-surgical evaluation. However, in order to detect malignancies before macroscopic changes are visible, evaluation of serum and tissue biomarkers should be considered. Among them, we distinguish markers of the cell cycle, proliferation, apoptosis, metastatic potential and prognosis, hormone receptors, inflammatory and more recent: metabolomic, gene expression, miRNA, and transcriptome sequencing markers. The use of a couple of the above-mentioned markers together seems to be the most useful for the early diagnosis of neoplastic diseases as well as to evaluate response to treatment, presence of tumor progression, or further prognosis. Molecular aspects of tumors seem to be crucial for proper understanding of tumorigenesis and the application of individual treatment options.

Establishment of a new cell line of canine inflammatory mammary cancer: IMC-118

Canine inflammatory mammary cancer (IMC) has long been regarded as an attractive animal model for research into human inflammatory breast cancer (IBC), Although some canine mammary tumour cell lines corresponding to human mammary cancer cell lines have been established, there is still a need to supplement the canine mammary tumour cell bank. The goal of this study was to create a new type of IMC cell line. The primary tumour, IMC-118, was identified as IMC by pathology examination. Immunohistochemistry analysis revealed negative immunoreactivity to oestrogen receptor (ER), but positive immunoreactivity to progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER-2). Immunofluorescence (IF) analysis revealed that the IMC-118 cell line from this primary tumour was negative for ER but positive for PR and HER-2, and was also positive for epithelial and mesenchymal cell markers. This cell line was cultured stably for more than 50 passages and grew well after cryopreservation. In vivo, tumour masses and metastases in the lungs were discovered after inoculating the IMC-118 cells into the nude mice model. As a result, a novel canine IMC cell line, IMC-118, was effectively established, and could be employed as a promising model for immunotherapy and epithelial-mesenchymal transition mechanism of IMC research in both dogs and humans.

Hormonal Homologies between Canine Mammary Cancer and Human Breast Cancer in a Series of Cases

Simple Summary

There is worldwide interest in understanding the cancerous diseases that are causing increasing deaths in humans. In recent years, interest has grown in finding suitable models of different types of cancer in animals to lead the scientific community to a better understanding of the disease, in order to win the battle against cancer. The aim of this investigation was to compare breast cancer samples and canine mammary tumors from a hormonal point of view to validate the canine species as a model to study human breast cancer. There was a close similarity between premenopausal human breast cancer and canine mammary cancer in terms of hormonal receptors. In both species, all hormones assayed were increased in tumors compared to normal mammary gland samples. This research not only further supports canine mammary cancer as a spontaneous model for the study of human breast cancer but is also important in providing a deeper understanding of the hormonal pathogenesis of breast/mammary cancer in each independent species.

Abstract

The validity of spontaneous canine mammary cancer (CMC) as a natural model for the study of human breast cancer (HBC) from a hormonal point of view has never been thoroughly investigated. In this study, we analyzed the immunohistochemical expression of aromatase (Arom) and steroid receptors [estrogen receptor α (ER α), estrogen receptor β (ER β), progesterone receptor (PR) and androgen receptor (AR)] and intratumor steroid hormone levels of 17β-estradiol (E2), estrone sulfate (SO4E1), progesterone (P4), androstenedione (A4), dehydroepiandrosterone (DHEA), and testosterone (T) in 78 samples of mammary cancer—51 human breast cancer (HBC) and 27 canine mammary cancer (CMC)—and corresponding controls. Frequency of tumors expressing Arom, ERβ, PR, and AR was similar in both species, whereas ERα+ tumors were less frequent in the canine species. There was a closer similarity between premenopausal HBC and CMC. In HBC and CMC, all hormones assayed were increased in tumors compared to control samples. Intratumor androgen levels were similar in the two species, although levels of progesterone and estrogens were higher in the HBC samples than the CMC samples. Statistical associations among Arom, receptors, and hormones analyzed suggest that the major hormonal influence in both species is estrogenic through the ER, being the α isoform predominant in the human samples. Our findings further support CMC as a spontaneous model for the study of HBC, especially premenopausal HBC, although several differences, such as the more prevalent ERα immunoexpression and higher intratumor levels of estrogens and P4 in HBC, should be taken into account in comparative hormonal studies.

Naturally-Occurring Canine Mammary Tumors as a Translational Model for Human Breast Cancer

Despite extensive research over many decades, human breast cancer remains a major worldwide health concern. Advances in pre-clinical and clinical research has led to significant improvements in recent years in how we manage breast cancer patients. Although survival rates of patients suffering from localized disease has improved significantly, the prognosis for patients diagnosed with metastatic disease remains poor with 5-year survival rates at only 25%. In vitro studies using immortalized cell lines and in vivo mouse models, typically using xenografted cell lines or patient derived material, are commonly used to study breast cancer. Although these techniques have undoubtedly increased our molecular understanding of breast cancer, these research models have significant limitations and have contributed to the high attrition rates seen in cancer drug discovery. It is estimated that only 3-6% of drugs that show promise in these pre-clinical models will reach clinical use. Models that can reproduce human breast cancer more accurately are needed if significant advances are to be achieved in improving cancer drug research, treatment outcomes, and prognosis. Canine mammary tumors are a naturally-occurring heterogenous group of cancers that have several features in common with human breast cancer. These similarities include etiology, signaling pathway activation and histological classification. In this review article we discuss the use of naturally-occurring canine mammary tumors as a translational animal model for human breast cancer research.

α-catenin, β-catenin and P-120-catenin immunoexpression in canine mammary tissues and their relationship with E-cadherin

Mammary tumors represent the second most common neoplasia in the canine species, where more than 50% of the cases are classified as malignant. The histological classification is used as a prognostic tool. Cadherins and catenins are responsible for cell adhesion and are intrinsic connected with the process of metastasis. E-cadherin expression in canine mammary tissues have been extensively studied. However, the studies with catenins are still scarce in the canine species. This study evaluated 74 canine mammary tissues by assessing the expression of E-cadherin and α, β and P-120 catenin molecules using the immunohistochemistry technique and their relationship with clinicopathological parameters. Three patterns of expression were identified in this study: membranous, cytoplasmic and both (membranous and cytoplasmic). In benign tumors, more than 80% of the cases had preserved expression and in malignant tumors 20% of the cases had reduced expression. A correlation between E-cadherin and P-120-catenin expression was found as well as a significant relationship between the histological type and the expression of α-catenin in malignant 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.

The clinical heterogeneity of preeclampsia is related to both placental gene expression and placental histopathology

BACKGROUND

Preeclampsia is a life-threatening disorder of pregnancy, demonstrating a high degree of heterogeneity in clinical features such as presentation, disease severity, and outcomes. This heterogeneity suggests distinct pathophysiological mechanisms may be driving the placental disease underlying this disorder. Our group recently reported distinct clusters of placental gene expression in preeclampsia and control pregnancies, allowing for the identification of at least 3 clinically relevant gene expression-based subtypes of preeclampsia. Histopathological examination of a small number of samples from 2 of the gene expression-based subtypes revealed placental lesions consistent with their gene expression phenotype, suggesting that detailed placental histopathology may provide further insight into the pathophysiology underlying these distinct gene expression-based subtypes.

OBJECTIVES

The objective of the study was to assess histopathological lesions in the placentas of patients belonging to each identified gene expression-based subtype of preeclampsia, characterized in our previous study. Our goal was to further understand the pathophysiologies defining these gene expression-based subtypes by integrating gene expression with histopathological findings, possibly identifying additional subgroups of preeclampsia patients.

STUDY DESIGN

Paraffin-embedded placental biopsies from patients included in the gene expression profiling study (n = 142 of 157, 90.4%) were sectioned, hematoxylin and eosin stained, and imaged. An experienced perinatal pathologist, blinded to gene expression findings and clinical information, assessed the presence and severity of histological lesions using a comprehensive, standardized data collection form. The frequency and severity scores of observed histopathological lesions were compared among gene expression-based subtypes as well as within each subtype using using Fisher exact tests, Kruskal-Wallis tests, and hierarchical clustering. The histological findings of the placental samples were visualized using t-distributed stochastic neighbor embedding and phylogenetic trees. Concordance and discordance between gene expression findings and histopathology were also investigated and visualized using principal component analysis.

RESULTS

Several histological lesions were found to be characteristic of each gene expression-based preeclampsia subtype. The overall concordance between gene expression and histopathology for all samples was 65% (93 of 142), with characteristic placental lesions for each gene expression-based subtype complementing prior gene enrichment findings (ie, placentas with enrichment of hypoxia-associated genes showed severe lesions of maternal vascular malperfusion). Concordant samples were located in the central area of each gene expression-based cluster when viewed on a principal component analysis plot. Interestingly, discordant samples (gene expression and histopathology not reflective of one another) were generally found to lie at the periphery of the gene expression-based clusters and tended to border the group of patients with phenotypically similar histopathology.

CONCLUSION

Our findings demonstrates a high degree of concordance between placental lesions and gene expression across subtypes of preeclampsia. Additionally, novel integrative analysis of scored placental histopathology severity and gene expression findings allowed for the identification of patients with intermediate phenotypes of preeclampsia not apparent through gene expression profiling alone. Future investigations should examine the temporal relationship between these 2 modalities as well as consider the maternal and fetal contributions to these subtypes of disease.

Current biomarkers of canine mammary tumors

Mammary tumors are the second most common neoplasia in dogs. Due to the high similarity of canine mammary tumors (CMT) to human breast cancers (HBC), human biomarkers of HBC are also detectable in cases of CMT. The evaluation of biomarkers enables clinical diagnoses, treatment options and prognosis for bitches suffering from this disease. The aim of this article is to give a short summary of the biomarkers of CMT based on current literature. Very promising biomarkers are miRNAs, cancer stem cells, and circulating tumor cells, as well as mutations of the breast cancer 1 gene (BRCA1) and breast cancer 2 gene (BRCA2). Until now, the most studied and reliable biomarkers of CMT have remained antigen Ki-67 (Ki-67), endothelial growth factor receptor, human epidermal growth factor receptor 2 (HER-2), estrogen receptor, progesterone receptor and cyclooxygenase 1 (COX-2), which can be detected in both serum and tissue samples using different molecular methods. However, carcinoembryonic antigen and cancer antigen 15-3 (CA 15-3), while poorly studied, seem to be good biomarkers, especially for the early detection and prognosis of CMT. We will also mention the following: proliferative cell nuclear antigen, tumor protein p53 (p53), E-cadherin, vascular endothelial growth factor, microRNAs, cancer stem cells and circulating tumor cells, which can also be useful biomarkers. Although many studies have been conducted so far, the estimation of biomarkers in cases of CMT is still not a common practice, and more detailed research should be done.

DNA Methylation Status of the Estrogen Receptor α Gene in Canine Mammary Tumors

Estrogen receptor α (ERα) has an important role in mammary carcinogenesis, prognosis, and treatment. In human and canine mammary cancer, the most aggressive tumors show loss of ERα expression, which in human breast cancer has been attributed to methylation of the cytosine followed by guanine (CpG) island within the estrogen receptor α gene ( ESR1) promoter. This study aimed to investigate the role of ESR1 CpG island (CGI) methylation in ERα expression in canine mammary tumors. Twenty-one canine mammary samples were sorted into three groups: malignant tumor (n = 9), benign tumor (n = 8), and normal gland (n = 4). Immunohistochemical analysis and reverse-transcription quantitative real-time PCR were performed to assess ERα expression and ESR1 mRNA levels. The methylation status was determined using sodium-bisulfite-treated DNA sequencing. All normal mammary glands and benign tumors showed high ERα expression (score range, 5-8). Six of the nine malignant tumors did not show ERα expression (score 0), two had score 2, and one had score 4. Lower ERα ( P < .005) and ESR1 mRNA levels ( P < .005) were found in malignant mammary tumors than in the other two groups. Canine ESR1 has an intragenic and non-promoter-associated CGI, different from humans. No significant variation in methylation percentage was observed among the groups, suggesting that ESR1 is not regulated by DNA methylation, unlike that in humans. This difference should be considered in further research using ERα as a biomarker for mammary tumors in canine studies on ERα-targeting therapy.

Hormone Receptor Expression Analyses in Neoplastic and Non-Neoplastic Canine Mammary Tissue by a Bead Based Multiplex Branched DNA Assay: A Gene Expression Study in Fresh Frozen and Formalin-Fixed, Paraffin-Embedded Samples

Immunohistochemistry (IHC) is currently considered the method of choice for steroid hormone receptor status evaluation in human breast cancer and, therefore, it is commonly utilized for assessing canine mammary tumors. In case of low hormone receptor expression, IHC is limited and thus is complemented by molecular analyses. In the present study, a multiplex bDNA assay was evaluated as a method for hormone receptor gene expression detection in canine mammary tissues. Estrogen receptor (ESR1), progesterone receptor (PGR), prolactin receptor (PRLR) and growth hormone receptor (GHR) gene expressions were evaluated in neoplastic and non-neoplastic canine mammary tissues. A set of 119 fresh frozen and 180 formalin-fixed, paraffin-embedded (FFPE) was comparatively analyzed and used for assay evaluation. Furthermore, a possible association between the hormone receptor expression in different histological subtypes of canine malignant mammary tumors and the castration status, breed and invasive growth of the tumor were analyzed. The multiplex bDNA assay proved to be more sensitive for fresh frozen specimens. Hormone receptor expression found was significantly decreased in malignant mammary tumors in comparison to non-neoplastic tissue and benign mammary tumors. Among the histological subtypes the lowest gene expression levels of ESR1, PGR and PRLR were found in solid, anaplastic and ductal carcinomas. In summary, the evaluation showed that the measurement of hormone receptors with the multiplex bDNA assay represents a practicable method for obtaining detailed quantitative information about gene expression in canine mammary tissue for future studies. Still, comparison with IHC or quantitative real-time PCR is needed for further validation of the present method.