Oncogene HER-2 in canine mammary gland carcinomas: an immunohistochemical and chromogenic in situ hybridization study

Canine Mammary Tumors: Classification, Biomarkers, Traditional and Personalized Therapies

In recent years, many studies have focused their attention on the dog as a proper animal model for human cancer. In dogs, mammary tumors develop spontaneously, involving a complex interplay between tumor cells and the immune system and revealing several molecular and clinical similarities to human breast cancer. In this review, we summarized the major features of canine mammary tumor, risk factors, and the most important biomarkers used for diagnosis and treatment. Traditional therapy of mammary tumors in dogs includes surgery, which is the first choice, followed by chemotherapy, radiotherapy, or hormonal therapy. However, these therapeutic strategies may not always be sufficient on their own; advancements in understanding cancer mechanisms and the development of innovative treatments offer hope for improved outcomes for oncologic patients. There is still a growing interest in the use of personalized medicine, which should play an irreplaceable role in the research not only in human cancer therapy, but also in veterinary oncology. Moreover, immunotherapy may represent a novel and promising therapeutic option in canine mammary cancers. The study of novel therapeutic approaches is essential for future research in both human and veterinary oncology.

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.

ERBB Receptors and Their Ligands in the Developing Mammary Glands of Different Species: Fifteen Characters in Search of an Author

The ERBB tyrosine kinase receptors and their ligands belong to a complex family that has diverse biological effects and expression profiles in the developing mammary glands, where its members play an essential role in translating hormone signals into local effects. While our understanding of these processes stems mostly from mouse models, there is the potential for differences in how this family functions in the mammary glands of other species, particularly in light of their unique histomorphological features. Herein we review the postnatal distribution and function of ERBB receptors and their ligands in the mammary glands of rodents and humans, as well as for livestock and companion animals. Our analysis highlights the diverse biology for this family and its members across species, the regulation of their expression, and how their roles and functions might be modulated by varying stromal composition and hormone interactions. Given that ERBB receptors and their ligands have the potential to influence processes ranging from normal mammary development to diseased states such as cancer and/or mastitis, both in human and veterinary medicine, a more complete understanding of their biological functions should help to direct future research and the identification of new therapeutic targets.

HER2 Overexpression and Cytogenetical Patterns in Canine Mammary Carcinomas

Human epidermal growth factor receptor 2 (HER2) is a tyrosine kinase receptor that promotes tumor cell growth and is implicated in the pathogenesis of human breast cancer. The role of HER2 in canine mammary carcinomas (CMCs) is not clear. Therefore, this study aimed to examine the protein expression and cytogenetic changes of HER2 and their correlation with other clinical–pathological parameters in CMC. We retrospectively selected 112 CMCs. HER2, ER, and Ki67 were assessed by immunohistochemistry. HER2 antibody validation was investigated by immunoblot on mammary tumor cell lines. Fluorescence in situ hybridization (FISH) was performed with probes for HER2 and CRYBA1 (control gene present on CFA9). HER2 protein overexpression was detected in 15 carcinomas (13.5%). A total of 90 carcinomas were considered technically adequate by FISH, and 8 out of 90 CMC (10%) were HER2 amplified, 3 of which showed a cluster-type pattern. HER2 overexpression was correlated with an increased number of HER2 gene copies (p = 0.01; R = 0.24) and overall survival (p = 0.03), but no correlation with ER, Ki67, grade, metastases, and tumor-specific survival was found. Surprisingly, co-amplification or polysomy was identified in three tumors, characterized by an increased copy number of both HER2 and CRYBA1. A morphological translocation-fusion pattern was recognized in 20 carcinomas (22%), with a co-localized signal of HER2 and CRYBA1. HER2 is not associated with clinical–pathological parameters of increased malignancy in canine mammary tumors, but it is suitable for studying different amplification patterns.

VEGF-B, VEGF-A, FLT-1, KDR, ERBB2, EGFR, GRB2, RAC1, CDH1 and HYAL-1 Genes Expression Analysis in Canine Mammary Gland Tumors and the Association with Tumor ClinicoPathological Parameters and Dog Breed Assessment

Canine mammary gland tumors (CMTs) are one of the most prevalent cancers in dogs and a good model for human breast cancer (BC), however gene expression analysis of CMTs is scarce. Although divergence of genes expression has been found in BC of different human races, no such research of different dog's breeds has been done. The purpose of this study was to investigate expression of the VEGF-B, VEGF-A, FLT-1, KDR, ERBB2, EGFR, GRB2, RAC1, CDH1 and HYAL-1 genes of canine mammary carcinomas, compare the expression levels with clinicopathological parameters and analyze expression disparities between different breeds. Carcinomas and adjacent tissues were collected from female dogs to perform routine histopathology, immunohistochemistry (IHC) and quantitative real-time polymerase chain reaction (qRT-PCR). We found that VEGF-B and EGFR genes were overexpressed in the mammary gland carcinomas compared to adjacent tissue. VEGF-B gene expression had associations with different parameters (tumor size, grade, and absence of metastasis). Furthermore, differences in VEGF-B, FLT1, ERBB2, GRB2, RAC1, CDH1 and HYAL-1 genes expression have been found in different breed dogs (German Shepherd, Yorkshire Terrier) and mixed-breed dogs indicating that a dog's breed could determine a molecular difference, outcome of cancer and should be accounted as a confounding factor in the future gene expression research.

ErbB2 copy number gain is associated with adverse outcome in canine mammary carcinoma

Copy number gain (CNG) and/or protein overexpression of ErbB2 have been observed in human breast cancer patients and are associated with poor prognosis. Similarly, ErbB2 overexpression has also been observed in canine mammary carcinoma; however, data on ErbB2 copy number is limited. The purposes of this study were to evaluate ErbB2 copy number in dogs with mammary carcinoma and to investigate associations of ErbB2 CNG with ErbB2 expression, histological and clinical characteristics, and survival. DNA samples were isolated from 59 formalin-fixed paraffin-embedded canine mammary gland tissues (34 carcinoma, 14 adenoma, and 11 normal). Using a digital PCR assay, the ErbB2 copy number in these samples was determined as compared to a reference gene on canine chromosome 8. ErbB2 CNG was detected in 14/34 (41%) carcinomas and 2/14 (14%) adenomas. ErbB2 overexpression was observed in 3/34 (9%) carcinomas but not in adenomas. Neither ErbB2 CNG nor ErbB2 overexpression were detected in the normal controls. There was no significant association of the ErbB2 CNG with histological and clinical characteristics such as age, neutered status, histological grade, tumor size, lymph node involvement, distant metastasis, and clinical stage in the dogs with mammary carcinoma. The presence of ErbB2 CNG, but not ErbB2 overexpression, was significantly related to the shorter overall survival. These findings suggest that ErbB2 CNG is a prognostic factor in dogs with mammary carcinoma.

Establishment and Characterization of Canine Mammary Gland Carcinoma Cell Lines With Vasculogenic Mimicry Ability in vitro and in vivo

Mammary tumors affect intact and elderly female dogs, and almost 50% of these cases are malignant. Cell culture offers a promising preclinical model to study this disease and creates the opportunity to deposit cell lines at a cell bank to allow greater assay reproducibility and more reliable validation of the results. Another important aspect is the possibility of establishing models and improving our understanding of tumor characteristics, such as vasculogenic mimicry. Because of the importance of cancer cell lines in preclinical models, the present study established and characterized primary cell lines from canine mammary gland tumors. Cell cultures were evaluated for morphology, phenotype, vasculogenic mimicry (VM), and tumorigenicity abilities. We collected 17 primary mammary carcinoma and three metastases and obtained satisfactory results from 10 samples. The cells were transplanted to a xenograft model. All cell lines exhibited a spindle-shaped or polygonal morphology and expressed concomitant pancytokeratin and cytokeratin 8/18. Four cell lines had vasculogenic mimicry ability in vitro, and two cell lines showed in vivo tumorigenicity and VM in the xenotransplanted tumor. Cellular characterization will help create a database to increase our knowledge of mammary carcinomas in dogs, including studies of tumor behavior and the identification of new therapeutic targets.

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.

ErbB2 Copy Number Aberration in Canine Urothelial Carcinoma Detected by a Digital Polymerase Chain Reaction Assay

Urothelial carcinoma (UC) is the most common tumor affecting the urinary bladder of dogs. Protein overexpression of ErbB2 (the canine homolog of HER2) has been observed in dogs with UC. However, no study regarding ErbB2 copy number aberration (CNA) is reported in dogs with UC. In this study, a digital PCR assay for detecting CNA of canine ErbB2 was developed. DNA samples were isolated from 83 formalin-fixed, paraffin-embedded urinary bladder tissues (36 UC, 8 polypoid cystitis, and 39 normal) and 94 urinary sediments (54 UC, 30 nonneoplastic, and 10 normal). The copy number of canine chromosome 8 (CFA8) was used as a control. In the urinary bladder tissues, ErbB2 CNA was detected in 12 of 36 (33%) UC, 2 of 8 (25%) polypoid cystitis, and 0 of 39 (0%) normal controls. In the urinary sediments, ErbB2 CNA was also detected in 19 of 54 (35%) UC; however, no ErbB2 CNA was detected in nonneoplastic diseases or normal controls. The sensitivity and specificity of ErbB2 CNA in urinary sediment for the detection of UC were 35% and 100%, respectively. There was a positive correlation between the copy number ratios of ErbB2 to CFA8 in the urinary bladder tissues and urinary sediments. Our findings indicate that the digital PCR assay of urinary sediments may be a useful, noninvasive method for detecting ErbB2 CNA in dogs with UC.

Assessment of HER2 Expression in Canine Urothelial Carcinoma of the Urinary Bladder

Canine urothelial carcinoma (UC) has a poor prognosis and high metastatic rate. Human epidermal growth factor receptor 2 (HER2), a receptor tyrosine kinase involved in cell proliferation and differentiation regulation, has been attracting interest as a therapeutic target molecule for human breast cancer. This study investigated expression of the canine homolog of HER2 (ERBB2) in canine UC, and its association with clinical factors. Since it has been controversial whether commercial anti-human HER2 antibody (Dako A0485) correctly recognizes the canine homolog of HER2, an application of the antibody using a canine UC cell line was validated first. By Western blot, a single band at the appropriate size for canine HER2 (185 kDa) was recognized. Immunohistochemistry for HER2 was performed on 23 samples of UC, 8 samples of polypoid cystitis, and 8 samples of normal urinary bladder, and the results were scored as either 0, 1+, 2+, or 3+ with reference to the evaluation method for human UC. Intense membranous HER2 immunoreactivity was frequently observed in neoplastic cells, especially in grade 2 UC. Minor HER2 expression was found in the epithelial cells of polypoid cystitis and normal bladder. The incidence of HER2 positivity (scores of 2+ or 3+) was 14 of 23 (60.9%) in UC, 3 of 8 (37.5%) in polypoid cystitis, and 0 of 8 (0%) in normal bladder. There was no significant correlation between HER2 positivity and clinical factors. While increased HER2 expression was observed in a subset of urothelial carcinomas, further mechanistic studies are needed to determine its role in the pathogenesis and targeted therapy of this cancer.

Canine invasive mammary carcinomas as models of human breast cancer. Part 1: natural history and prognostic factors

Purpose

Dogs have been proposed as spontaneous animal models of human breast cancer, based on clinicopathologic similarities between canine and human mammary carcinomas. We hypothesized that a better knowledge of the natural history and prognostic factors of canine invasive mammary carcinomas would favor the design of preclinical trials using dogs as models of breast cancer.

Methods

The 2-year outcome of 350 female dogs with spontaneous invasive mammary carcinoma was studied. The investigated prognostic factors included age at diagnosis, pathologic tumor size, pathologic nodal stage, lymphovascular invasion, histological grade, and expression of Estrogen Receptor alpha (ERα), Progesterone Receptor, Ki-67, Human Epidermal Growth Factor Receptor 2, basal cytokeratins 5/6, and Epidermal Growth Factor Receptor. Multivariate survival analyses were performed using the Cox proportional hazards model.

Results

The overall survival after mastectomy was 11 months. Within 1 year post mastectomy, 41.5% of dogs (145/350) died from their mammary carcinoma. By multivariate analysis, the significant prognostic factors for overall survival included a pathologic tumor size larger than 20 mm [HR 1.47 (95% confidence interval 1.15–1.89)], a positive nodal stage [pN+, HR 1.89 (1.43–2.48)], a histological grade III [HR 1.32 (1.02–1.69)], ERα negativity [HR 1.39 (1.01–1.89)], a high Ki-67 proliferation index [HR 1.32 (1.04–1.67)], and EGFR absence [HR 1.33 (1.04–1.69)].

Conclusion

The short natural history of spontaneous canine invasive mammary carcinomas and high rate of cancer-related death allow for rapid termination of preclinical investigations. The prognostic factors of invasive mammary carcinomas are remarkably similar in dogs and humans, highlighting the similarities in cancer biology between both species.

In vitro comparative models for canine and human breast cancers

During the past four decades, an increased number of similarities between canine mammary tumors and human breast cancer have been reported: molecular, histological, morphological, clinical and epidemiological, which lead to comparative oncological studies. One of the most important goals in human and veterinary oncology is to discover potential molecular biomarkers that could detect breast cancer in an early stage and to develop new effective therapies. Recently, cancer cell lines have successfully been used as an in vitro model to study the biology of cancer, to investigate molecular pathways and to test the efficiency of anticancer drugs. Moreover, establishment of an experimental animal model for the study of human breast cancer will improve testing potential anti-cancer therapies and the discovery of effective therapeutic schemes suitable for human clinical trials.

In this review, we collected data from previous studies that strengthen the value of canine mammary cancer cell lines as an in vitro model for the study of human breast cancer.

Dogs as a Model for Cancer

Spontaneous cancers in client-owned dogs closely recapitulate their human counterparts with respect to clinical presentation, histological features, molecular profiles, and response and resistance to therapy, as well as the evolution of drug-resistant metastases. In several instances the incorporation of dogs with cancer into the preclinical development path of cancer therapeutics has influenced outcome by helping to establish pharmacokinetic/pharmacodynamics relationships, dose/regimen, expected clinical toxicities, and ultimately the potential for biologic activity. As our understanding regarding the molecular drivers of canine cancers has improved, unique opportunities have emerged to leverage this spontaneous model to better guide cancer drug development so that therapies likely to fail are eliminated earlier and therapies with true potential are optimized prior to human studies. Both pets and people benefit from this approach, as it provides dogs with access to cutting-edge cancer treatments and helps to insure that people are given treatments more likely to succeed.

Investigation of HER2 expression in canine mammary tumors by antibody-based, transcriptomic and mass spectrometry analysis: is the dog a suitable animal model for human breast cancer?

Canine mammary tumors (CMTs) share many features with human breast cancer (HBC), specifically concerning cancer-related pathways. Although the human epidermal growth factor receptor 2 (HER2) plays a significant role as a therapeutic and prognostic biomarker in HBC, its relevance in the pathogenesis and prognosis of CMT is still controversial. The aim of this study was to investigate HER2 expression in canine mammary hyperplasic and neoplastic tissues as well as to evaluate the specificity of the most commonly used polyclonal anti HER2 antibody by multiple molecular approaches. HER2 protein and RNA expression were determined by immunohistochemistry (IHC) and by quantitative real-time (qRT) PCR. A strong cell membrane associated with non-specific cytoplasmic staining was observed in 22% of carcinomas by IHC. Adenomas and carcinomas exhibited a significantly higher HER2 mRNA expression when compared to normal mammary glands, although no significant difference between benign and malignant tumors was noticed by qRT-PCR. The IHC results suggest a lack of specificity of the FDA-approved antibody in CMT samples as further demonstrated by Western immunoblotting (WB) and reverse phase protein arrays (RPPA). Furthemore, HER2 was not detected by mass spectrometry (MS) in a protein-expressing carcinoma at the IHC investigation. This study highlights that caution needs to be used when trying to translate from human to veterinary medicine information concerning cancer-related biomarkers and pathways. Further investigations are necessary to carefully assess the diagnostic and biological role specifically exerted by HER2 in CMTs and the use of canine mammary tumors as a model of HER2 over-expressing breast cancer.

EGFR, HER-2 and KRAS in canine gastric epithelial tumors: a potential human model?

Epidermal growth factor receptor (EGFR or HER-1) and its analog c-erbB-2 (HER-2) are protein tyrosine kinases correlated with prognosis and response to therapy in a variety of human cancers. KRAS mediates the transduction of signals between EGFR and the nucleus, and its mutation has been identified as a predictor of resistance to anti-EGFR drugs. In human oncology, the importance of the EGFR/HER-2/KRAS signalling pathway in gastric cancer is well established, and HER-2 testing is required before initiating therapy. Conversely, this pathway has never been investigated in canine gastric tumours. A total of 19 canine gastric epithelial neoplasms (5 adenomas and 14 carcinomas) were retrospectively evaluated for EGFR/HER-2 immunohistochemical expression and KRAS mutational status. Five (35.7%) carcinomas were classified as intestinal-type and 9 (64.3%) as diffuse-type. EGFR was overexpressed (≥1+) in 8 (42.1%) cases and HER-2 (3+) in 11 (57.9%) cases, regardless of tumour location or biological behaviour. The percentage of EGFR-positive tumours was significantly higher in the intestinal-type (80%) than in the diffuse-type (11.1%, p = 0.023). KRAS gene was wild type in 18 cases, whereas one mucinous carcinoma harboured a point mutation at codon 12 (G12R). EGFR and HER-2 may be promising prognostic and therapeutic targets in canine gastric epithelial neoplasms. The potential presence of KRAS mutation should be taken into account as a possible mechanism of drug resistance. Further studies are necessary to evaluate the role of dog as a model for human gastric cancer.

Canine mammary tumors: a review and consensus of standard guidelines on epithelial and myoepithelial phenotype markers, HER2, and hormone receptor assessment using immunohistochemistry

Although there have been several studies on the use of immunohistochemical biomarkers of canine mammary tumors (CMTs), the results are difficult to compare. This article provides guidelines on the most useful immunohistochemical markers to standardize their use and understand how outcomes are measured, thus ensuring reproducibility of results. We have reviewed the biomarkers of canine mammary epithelial and myoepithelial cells and identified those biomarkers that are most useful and those biomarkers for invasion and lymph node micrometastatic disease. A 10% threshold for positive reaction for most of these markers is recommended. Guidelines on immunolabeling for HER2, estrogen receptors (ERs), and progesterone receptors (PRs) are provided along with the specific recommendations for interpretation of the results for each of these biomarkers in CMTs. Only 3+ HER2-positive tumors should be considered positive, as found in human breast cancer. The lack of any known response to adjuvant endocrine therapy of ER- and PR-positive CMTs prevents the use of the biological positive/negative threshold used in human breast cancer. Immunohistochemistry results of ER and PR in CMTs should be reported as the sum of the percentage of positive cells and the intensity of immunolabeling (Allred score). Incorporation of these recommendations in future studies, either prospective or retrospective, will provide a mechanism for the direct comparison of studies and will help to determine whether these biomarkers have prognostic significance. Finally, these biomarkers may ascertain the most appropriate treatment(s) for canine malignant mammary neoplasms.

Genome aberrations in canine mammary carcinomas and their detection in cell-free plasma DNA

Mammary tumors are the most frequent cancers in female dogs exhibiting a variety of histopathological differences. There is lack of knowledge about the genomes of these common dog tumors. Five tumors of three different histological subtypes were evaluated. Massive parallel sequencing (MPS) was performed in comparison to the respective somatic genome of each animal. Copy number and structural aberrations were validated using droplet digital PCR (ddPCR). Using mate-pair sequencing chromosomal aneuploidies were found in two tumors, frequent smaller deletions were found in one, inter-chromosomal fusions in one other, whereas one tumor was almost normal. These aberrations affect several known cancer associated genes such as cMYC, and KIT. One common deletion of the proximal end of CFA27, harboring the tumor suppressor gene PFDN5 was detected in four tumors. Using ddPCR, this deletion was validated and detected in 50% of tumors (N = 20). Breakpoint specific dPCRs were established for four tumors and tumor specific cell-free DNA (cfDNA) was detected in the plasma. In one animal tumor-specific cfDNA was found >1 year after surgery, attributable to a lung metastasis. Paired-end sequencing proved that copy-number imbalances of the tumor are reflected by the cfDNA. This report on chromosomal instability of canine mammary cancers reveals similarities to human breast cancers as well as special canine alterations. This animal model provides a framework for using MPS for screening for individual cancer biomarkers with cost effective confirmation and monitoring using ddPCR. The possibility exists that ddPCR can be expanded to screening for common cancer related variants.

Analysis of a New Histological and Molecular-Based Classification of Canine Mammary Neoplasia

Canine mammary tumors (CMTs) are morphologically and biologically heterogeneous, prompting several attempts to classify such tumors on the basis of their histopathological characteristics. Recently, molecular-based analysis methods borrowed from human breast cancer research have also been applied to the classification of CMTs. In this study, canine mammary neoplasms ( n = 648) occurring in Korea from 2008 to 2011 were analyzed according to the histological classification and grading system proposed by Goldschmidt et al. Furthermore, randomly selected mammary carcinomas ( n = 159) were classified according to the molecular subtype using immunohistochemical characteristics. Canine mammary neoplasia accounted for 52.6% (648/1250) of the tumors in female dogs, and 51.7% (340/648) of these were malignant. All of the carcinoma-anaplastic subtypes were grade III tumors (5/5, 100%), while most of the carcinoma-tubular subtypes (15/18, 83.3%) and carcinoma arising in a complex adenoma/mixed-tumor subtype (115/135, 85.2%) were grade I tumors. Tumor cell invasion into lymphatic vessels was most common in the comedocarcinoma, carcinoma-anaplastic, and inflammatory carcinoma subtypes. The most frequently occurring molecular subtype (70/159, 44%) was luminal A. However, the basal-like subtype was the most malignant and was frequently associated with grade III tumors and lymphatic invasion. The carcinoma-solid subtypes were also often of the basal-like subtype. Reclassification of CMTs using the newly proposed histopathological classification system and molecular subtyping could aid in determining the prognosis and the most suitable anticancer treatment for each case.

HER-2 expression in canine morphologically normal, hyperplastic and neoplastic mammary tissues and its correlation with the clinical outcome

The proto-oncogene HER-2/neu (c-erbB-2) encodes a transmembrane receptor protein with tyrosine-kinase activity. Previous studies have shown that HER-2 protein over-expression is present in canine mammary tumours, however, possible prognostic and predictive analogies between protein over-expression patterns in canine and human species are still controversial. Thirty-five canine mammary carcinomas, 11 mammary adenomas, and normal, hyperplastic or dysplastic tissues taken at the marginal area of the tumours were evaluated by immunohistochemistry (IHC) for HER-2 expression, using the Hercept Test® system scoring guidelines. HER-2 over-expression was detected in 3/11 adenomas and 10/35 carcinomas. Normal, hyperplastic and dysplastic mammary tissues were also found to be positive. The correlations between HER-2 expression and tumour histological grading, mitotic index, the presence of lymphatic invasion, and overall survival (OS) were evaluated. In carcinomas, HER-2 positive status only correlated with the mitotic index. A positive correlation was also found between HER-2 positive status and the presence of HER-2 over-expression in normal, hyperplastic or/and dysplastic mammary tissues surrounding the tumours. The percentage of HER-2 over-expressing tumours was similar to the percentage previously observed in canine benign and malignant mammary tumours. However an investigation regarding morphologically normal and hyperplastic or dysplastic tissues surrounding neoplastic lesions also showed HER-2 over-expression. In contrast with human mammary tumours, this study confirmed that in canine species, HER-2 over-expression does not identify a subgroup of tumours with a poor prognosis. In fact, we found HER-2 over-expression in morphologically non-neoplastic mammary tissues, surrounding hyperplastic and neoplastic lesions.

Comparative oncology: ErbB-1 and ErbB-2 homologues in canine cancer are susceptible to cetuximab and trastuzumab targeting

To facilitate comparative oncology trials we compared the biological and molecular homologies of canine (dog; Canis lupus familiaris) and human tumor-associated antigens ErbB-1 and -2. Further, we investigated whether they could serve as targets for anti-ErbB-1 (cetuximab) and anti-ErbB-2 antibodies (trastuzumab), which are highly relevant in human clinical oncology.

Immunohistochemistry of canine mammary cancer showed ErbB-1 overexpression in 3/10 patients and ErbB-2 in 4/10. We report 91% amino acid homology for ErbB-1 and 92% for ErbB-2 between canine and human molecules. Modeling of canine on human ErbB-1 revealed that the cetuximab epitope only differs by 4 amino acids: Lys443 is replaced by Arg, Ser468 by Asn, Gly471 by Asp, and Asn473 by Lys in canines. The trastuzumab binding site is identical in human and canine ErbB-2 apart from a single amino acid change (Pro557 to Ser). Binding of cetuximab and trastuzumab to canine mammary carcinoma cells CF33, CF41, Sh1b and P114 was confirmed by flow cytometry. Both antibodies significantly inhibited canine tumor cell proliferation partly due to growth arrest in G₀/G₁ phase. We explain the lower efficiency on the tested canine than on human SKBR3 and A431 cells, by a 2-log lower expression level of the canine ErbB-1 and -2 molecules.

Our results indicate significant homology of human and canine Erb-1 and -2 tumor associated antigens. The fact that the canine homologues express the cetuximab and trastuzumab epitopes may facilitate antibody-based immunotherapy in dogs. Importantly, the striking similarities of ErbB-1 and -2 molecules open up avenues towards comparative strategies for targeted drug development.

Possible role of Snail expression as a prognostic factor in canine mammary neoplasia

Epithelial cells adhere tightly to each other by cell-to-cell adhesion and through the basement membrane barrier to prohibit movement. In carcinomas, neoplastic epithelial cells lose their epithelial characteristics and acquire a mesenchymal phenotype during the epithelial-mesenchymal transition (EMT) for invasion and metastasis. The aim of this study was to identify Snail expression and examine the role of Snail protein in canine mammary tumour progression. Immunohistochemical expression of Snail, E-cadherin, oestrogen receptor, human epidermal growth factor receptor-2, cytokeratin 14 and p63 was analyzed in 54 samples of canine mammary epithelial tumours (11 adenomas and 43 carcinomas). Expression of mRNA encoding Snail was evaluated in seven samples (one normal mammary gland, two adenomas and four carcinomas) by reverse transcriptase-polymerase chain reaction. Snail mRNA was detected in all samples. Snail expression correlated significantly with histological type, grade and lymphatic invasion. However, there was no association between Snail expression and molecular subtype and between Snail expression and that of E-cadherin. Snail, a hallmark of EMT, might play an important role in invasion and metastasis of canine mammary carcinomas.

Pathological classification of canine mammary tumor based on quantifying mRNA levels of hormonal receptors, SATB1, and Snail in tissue and fine needle biopsy samples

Cytological diagnosis is not generally conclusive enough to identify histopathological malignancy in canine mammary tumors (CMTs). To establish cytological examination using fine needle biopsy (FNB) samples, gene expressions of hormonal receptors, human epidermal growth factor receptor 2 (HER2), and transcription regulators (Special AT-rich binding protein 1: SATB1 and Snail) were investigated in both tissue and FNB samples of CMTs. In tissue samples of malignant CMTs, especially invasive ones, low expressions of hormonal receptors and high expressions of SATB1 and Snail were detected. On discriminant analysis of tissue samples, 73.2% of CMTs were correctly classified according to histopathological examinations. In FNB samples of malignant CMTs, low expressions of hormonal receptors were detected. On discriminant analysis of FNB samples, 74.2% of CMTs were correctly classified according to histopathological examination. In conclusion, FNB gene expressions had a utility for diagnosis of CMTs malignancy in some degree. By researching more sensitive genes for malignant CMTs, the gene examination of FNB samples from CMTs will become a useful diagnostic tool that can be performed easily without anesthesia and could predict tumor malignancy and invasion prior to surgical removal.

Histological and Immunohistochemical Identification of Atypical Ductal Mammary Hyperplasia as a Preneoplastic Marker in Dogs

This study describes and evaluates the morphological and molecular relationship between canine mammary ductal hyperplasias with atypia and canine mammary neoplasias. Ductal hyperplasia was identified in association with malignant neoplasia in 56 of the 115 cases (48,8%), and although ductal hyperplasia without atypia was the type most frequently noted in the cases, most examples of hyperplasia with atypia were associated with mammary tumors. Estrogen receptor, E-cadherin, and cytokeratins 1, 5, 10 and 14 (CK34bE12) expression was quite lower than in normal mammary tissue, and HER2 overexpression was absent in all proliferative cells of ductal hyperplasia. The Ki-67 expression, epidermal growth factor receptor and progesterone receptor expression appeared higher in those hyperplastic lesions analyzed than in normal mammary glands. These findings suggest that canine mammary atypical hyperplasia may play an important role in the process of malignant neoplastic transformation, with molecular alterations that are similar to precursor lesions reported in humans.

Columnar cell lesions of the canine mammary gland: pathological features and immunophenotypic analysis

BACKGROUND

It has been suggested that columnar cell lesions indicate an alteration of the human mammary gland involved in the development of breast cancer. They have not previously been described in canine mammary gland. The aim of this paper is describe the morphologic spectrum of columnar cell lesions in canine mammary gland specimens and their association with other breast lesions.

METHODS

A total of 126 lesions were subjected to a comprehensive morphological review based upon the human breast classification system for columnar cell lesions. The presence of preinvasive (epithelial hyperplasia and in situ carcinoma) and invasive lesions was determined and immunophenotypic analysis (estrogen receptor (ER), progesterone receptor (PgR), high molecular weight cytokeratin (34betaE-12), E-cadherin, Ki-67, HER-2 and P53) was perfomed.

RESULTS

Columnar cell lesions were identified in 67 (53.1%) of the 126 canine mammary glands with intraepithelial alterations. They were observed in the terminal duct lobular units and characterized at dilated acini may be lined by several layers of columnar epithelial cells with elongated nuclei. Of the columnar cell lesions identified, 41 (61.2%) were without and 26 (38.8%) with atypia. Association with ductal hyperplasia was observed in 45/67 (67.1%). Sixty (89.5%) of the columnar cell lesions coexisted with neoplastic lesions (20 in situ carcinomas, 19 invasive carcinomas and 21 benign tumors). The columnar cells were ER, PgR and E-cadherin positive but negative for cytokeratin 34betaE-12, HER-2 and P53. The proliferation rate as measured by Ki-67 appeared higher in the lesions analyzed than in normal TDLUs.

CONCLUSIONS

Columnar cell lesions in canine mammary gland are pathologically and immunophenotypically similar to those in human breast. This may suggest that dogs are a suitable model for the comparative study of noninvasive breast lesions.

Molecular-based tumour subtypes of canine mammary carcinomas assessed by immunohistochemistry

Background

Human breast cancer is classified by gene expression profile into subtypes consisting of two hormone (oestrogen and/or progesterone) receptor-positive types (luminal-like A and luminal-like B) and three hormone receptor-negative types [human epidermal growth factor receptor 2-expressing, basal-like, and unclassified ("normal-like")]. Immunohistochemical surrogate panels are also proposed to potentially identify the molecular-based groups. The present study aimed to apply an immunohistochemical panel (anti-ER, -PR, -ERB-B2, -CK 5/6 and -CK14) in a series of canine malignant mammary tumours to verify the molecular-based classification, its correlation with invasion and grade, and its use as a prognostic aid in veterinary practice.

Results

Thirty-five tumours with luminal pattern (ER+ and PR+) were subgrouped into 13 A type and 22 B type, if ERB-B2 positive or negative. Most luminal-like A and basal-like tumours were grade 1 carcinomas, while the percentage of luminal B tumours was higher in grades 2 and 3 (Pearson Chi-square P = 0.009). No difference in the percentage of molecular subtypes was found between simple and complex/mixed carcinomas (Pearson Chi-square P = 0.47). No significant results were obtained by survival analysis, even if basal-like tumours had a more favourable prognosis than luminal-like lesions.

Conclusion

The panel of antibodies identified only three tumour groups (luminal-like A and B, and basal-like) in the dog. Even though canine mammary tumours may be a model of human breast cancer, the existence of the same carcinoma molecular subtypes in women awaits confirmation. Canine mammary carcinomas show high molecular heterogeneity, which would benefit from a classification based on molecular differences. Stage and grade showed independent associations with survival in the multivariate regression, while molecular subtype grouping and histological type did not show associations. This suggests that caution should be used when applying this classification to the dog, in which invasion and grade supply the most important prognostic information.

Prevalence and Classification of Spontaneous Mammary Intraepithelial Lesions in Dogs Without Clinical Mammary Disease

Mammary intraepithelial lesions (IELs) are noninvasive epithelial proliferations that include ductal hyperplasia (DH), atypical DH (ADH), and ductal carcinoma in situ (DCIS). In women, IELs are associated with increased risk of invasive breast cancer and form a basis for therapeutic decisions. Similarly, in female dogs, IELs are common in tumor-bearing glands and in non-tumor-bearing glands. To determine the prevalence and types of spontaneous IELs, mammary glands from 108 female dogs without clinical mammary disease were evaluated histologically and immunohistochemically. Within this population, 56 dogs (52%) had at least one type of spontaneous IEL, including DH (49 dogs), ADH (14 dogs), low-grade DCIS (19 dogs), intermediate-grade DCIS (12 dogs), and high-grade DCIS (1 dog). Twenty-one dogs had two or more different IEL types. In 23 of 24 dogs with atypical IELs (ADH or DCIS), immunohistochemical expression was determined for estrogen receptor α (ER-α), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER-2/neu), and Ki-67. For all markers examined, low-grade DCIS had significantly lower scores than did adjacent nonlesional gland; PR expression was significantly decreased in low-grade DCIS compared to other atypical lesions. Sixty-one lesions were ER-α negative (12 ADH, 36 low-grade DCIS, 13 intermediate-grade DCIS), and no lesions overexpressed HER-2/neu. Based on the dog’s prevalence of spontaneous mammary IELs that precede clinical mammary disease, the remarkable histologic similarity between canine and human IELs, and the loss of ER expression in certain IELs in both species, the dog shows promise as a model for human breast preneoplasia.

Heat shock proteins in animal neoplasms and human tumours--a comparison

Heat shock proteins (HSPs) are implicated in all phases of cancer from proliferation, impaired apoptosis and sustained angiogenesis to invasion and metastasis. The presence of abnormal HSP levels in several human tumours suggests that these proteins could be used as diagnostic and/or prognostic markers, whilst the direct correlation between HSP expression and drug resistance in neoplastic tissues means they could also be used to predict cancer response to specific treatment. HSPs have also been successfully targeted in clinical trials modifying their expression or chaperone activity. Preliminary studies in veterinary medicine have also demonstrated the presence of altered HSP expression in neoplasms, and the study of carcinogenesis and the role of HSPs in animal models will surely be an additional source of information for clinical cancer research.

Identification of molecular phenotypes in canine mammary carcinomas with clinical implications: application of the human classification

Similarly to humans, canine mammary cancer represents a heterogeneous group in terms of morphology and biological behaviour. In the present study, we evaluated a series of canine mammary carcinomas based on a new human classification, initially based on gene expression profiling analysis. Similarly to human breast cancer, by using an immunohistochemistry surrogate panel based on five molecular markers [estrogen receptor, human epidermal growth factor receptor 2 (HER2), cytokeratin 5, p63 and P-cadherin], we were able to classify canine mammary carcinomas into four different subtypes: luminal A [estrogen receptor (ER)+/HER2-; 44.8%], luminal B (ER+/HER2+; 13.5%), basal (ER-/HER2- and a basal marker positive; 29.2%) and HER2 overexpressing tumours (ER-/HER2+; 8.3%). Luminal A-type tumours were characterised by lower grade and proliferation rate, whereas basal-type tumours were mostly high grade, high proliferative and positive for cytokeratin 5, p63 and P-cadherin. In addition, as in humans, basal subtype was significantly associated with shorter disease-free and overall survival rates, and we propose canine mammary carcinomas as a suitable natural model for the study of this particular subset of human carcinomas.

Increased survival in dogs with malignant mammary tumours overexpressing HER-2 protein and detection of a silent single nucleotide polymorphism in the canine HER-2 gene

The aims of this study were to explore the relationship between clinical outcome and HER-2 protein expression in dogs with malignant mammary tumours after surgery and to determine the sequence of the HER-2 gene. Tissues from 91 dogs diagnosed with malignant mammary tumours, six with benign lesions and two normal mammary glands were analysed for the expression of HER-2 by immunohistochemistry (IHC). Exons 14-18 of the HER-2 gene were amplified by reverse transcriptase polymerase chain reaction and sequenced in 19 tumours with IHC scores >2+; larger coding regions of HER-2 were analysed in five tumours. HER-2 protein overexpression was found in 27/91 (29.7%) of canine malignant mammary tumours. Dogs with HER-2-overexpressing malignant mammary tumours tended to have a higher survival rate than those that expressed a normal level of HER-2 within 2 years of surgery. In 3/19 cases, HER-2 sequences had a single nucleotide polymorphism, T(1725)C, with no change in the amino acid identity (Cys). No other sequence aberration of HER-2 was found.

Proto-oncogene HER-2 in normal, dysplastic and tumorous feline mammary glands: an immunohistochemical and chromogenic in situ hybridization study

Background

Feline mammary carcinoma has been proposed as a natural model of highly aggressive, hormone-independent human breast cancer. To further explore the utility of the model by adding new similarities between the two diseases, we have analyzed the oncogene HER-2 status at both the protein and the gene levels.

Methods

Formalin-fixed, paraffin-embedded tissue samples from 30 invasive carcinomas, 7 benign lesions and two normal mammary glands were analyzed. Tumour features with prognostic value were recorded. The expression of protein HER-2 was analyzed by immunohistochemistry and the number of gene copies by means of DNA chromogenic in situ hybridization.

Results

Immunohistochemical HER-2 protein overexpression was found in 40% of feline mammary carcinomas, a percentage higher to that observed in human breast carcinoma. As in women, feline tumours with HER-2 protein overexpression had pathological features of high malignancy. However, amplification of HER-2 was detected in 16% of carcinomas with protein overexpression, a percentage much lower than that observed in their human counterpart.

Conclusion

Feline mammary carcinoma would be a suitable natural model of that subset of human breast carcinomas with HER-2 protein overexpression without gene amplification.

Heat shock protein expression in canine malignant mammary tumours

Background

Abnormal levels of Heat Shock Proteins (HSPs) have been observed in many human neoplasms including breast cancer and it has been demonstrated that they have both prognostic and therapeutic implications. In this study, we evaluated immunohistochemical expression of HSPs in normal and neoplastic canine mammary glands and confronted these results with overall survival (OS), in order to understand the role of HSPs in carcinogenesis and to establish their potential prognostic and/or therapeutic value.

Methods

Immunohistochemical expression of Hsp27, Hsp72, Hsp73 and Hsp90 was evaluated in 3 normal canine mammary glands and 30 malignant mammary tumours (10 in situ carcinomas, 10 invasive carcinomas limited to local structures without identifiable invasion of blood or lymphatic vessels, 10 carcinomas with invasion of blood or lymphatic vessels and/or metastases to regional lymph nodes). A semi-quantitative method was used for the analysis of the results.

Results

Widespread constitutive expression of Hsp73 and Hsp90 was detected in normal tissue, Hsp72 appeared to be focally distributed and Hsp27 showed a negative to rare weak immunostaining. In mammary tumours, a significant increase in Hsp27 (P < 0.01), Hsp72 (P < 0.05) and Hsp90 (P < 0.01) expression was observed as well as a significant reduction in Hsp73 (P < 0.01) immunoreactivity compared to normal mammary gland tissue. Hsp27 demonstrated a strong positivity in infiltrating tumour cells and metaplastic squamous elements of invasive groups. High Hsp27 expression also appeared to be significantly correlated to a shorter OS (P = 0.00087). Intense immunolabelling of Hsp72 and Hsp73 was frequently detected in infiltrative or inflammatory tumour areas. Hsp90 expression was high in all tumours and, like Hsp73, it also showed an intense positivity in lymphatic emboli.

Conclusion

These results suggest that Hsp27, Hsp72 and Hsp90 are involved in canine mammary gland carcinogenesis. In addition, Hsp27 appears to be implicated in tumour invasiveness and its high immunodetection in invasive tumours is indicative of a poorer clinical outcome.

Matrix metalloproteinase inhibitor RECK expression in canine tumors

Matrix metalloproteinases (MMPs) selectively degrade the extracellular matrix, and they have been reported to play an important role in tumor invasion, metastasis and angiogenesis. These enzymes are closely related to tumor malignancy and patient survival time. Recently, reversion-inducing cysteine-rich protein with Kazal motifs (RECK) gene was identified as an endogenous membrane-anchored MMP inhibitor. The down-regulation of RECK has been implicated in tumor progression. In this study, the expression levels of the RECK messenger ribonucleic acid (mRNA) in various spontaneously developed canine tumors were investigated by using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), and the correlation between RECK and clinicopathological factors, as well as MMP-9 expression were analyzed. The median age of 36 dogs investigated in this study was 9 years old (range, 1-15 years old). Quantitative RT-PCR could detect low levels of expression of RECK mRNA in the tumor samples. The expression levels of RECK mRNA in some tumor tissue samples were significantly lower than those in normal tissue samples. No significant associations of RECK with clinicopathological factors were observed. Using the Mann-Whitney U test, the expression level of the MMP-9 mRNA was observed to be significantly correlated to RECK expression (p<0.05).

Molecular cloning of canine membrane-anchored inhibitor of matrix metalloproteinase, RECK

The reversion-inducing cysteine-rich protein with Kazal motifs (RECK) gene is one of the endogenous matrix metalloproteinase (MMP) inhibitors. It was reported that decreased RECK expression closely correlated with tumor malignancy. We determined the cDNA sequence of the canine RECK gene. The cDNA sequence and deduced amino acid of canine RECK were 2,913 bases and 971 residues, respectively. The predicted amino acid sequence of the protein showed 95.5% and 91.9% homology with human and mouse RECK, respectively. RECK mRNA expression was analyzed in various canine tissues and tumor cell lines by quantitative RT-PCR. The highest RECK expression was detected in lung and testis. In comparison with the tissues, a remarkably low expression level was detected in tumor cell lines. In addition, the RECK gene was transfected in the canine transitional cell carcinoma, and its influence on cell proliferation, migration, and invasion was analyzed. The transfected RECK gene suppressed only canine tumor invasion. These results showed that RECK might play an important role in tumor malignancy in dogs as well as in other mammalians.

A prospective analysis of immunohistochemically determined estrogen receptor alpha and progesterone receptor expression and host and tumor factors as predictors of disease-free period in mammary tumors of the dog

The immunohistochemically determined estrogen receptor (ER) alpha (ERalpha) and progesterone receptor (PR) status, as well as recognized, well-accepted prognostic indicators and host factors were prospectively analyzed in 84 cases of primary canine mammary carcinoma for their effect on disease-free period (recurrence free, metastasis free, or combined) (DFP) after an observation period of 18 months. The presence of one or both receptors, as well as tumor size, lymph node status, histologic grading, intravascular growth, and necrosis, were of prognostic value for DFP. In multivariate analysis, only tumor size and histologic grading proved to be independent prognosticators. None of the host factors analyzed were of prognostic value for DFP. ERalpha, PR, or both were detected in 173 out of 228 tumors: 70 ERalpha and PR; 5 ERalpha only; 98 PR only. Statistically significant differences regarding the presence of one or both receptors were observed between benign and malignant tumors and between complex, mixed, and simple histologic subtypes of benign and malignant tumors. In the group of malignant tumors (n=155), the presence of one or both receptors was more frequent in tumors smaller than 3 cm, without lymph node metastasis, with tubulopapillary rather than solid patterns of growth among simple carcinomas, of histologic grades I and II, without both intravascular growth and necrosis, and with lymphocyte cell infiltrates. The most frequent groups of hormone receptors-positive tumors were the ERalpha-positive and PR-positive group among benign and the ERalpha-negative and PR-positive group among malignant tumors.

Overexpression of HER-2 in feline invasive mammary carcinomas: an immunohistochemical survey and evaluation of its prognostic potential

The role of c-erbB-2 protooncogene status in feline invasive mammary carcinomas (FMCs) was assessed through the HER-2 receptor immunohistochemical expression. The HER-2 overexpression was then correlated with some relevant histologic parameters and with the clinical course of the disease during a 2-year follow-up. Forty-seven FMCs from surgically treated queens were considered. Tumors were classified according to the WHO criteria and stromal or lymphatic invasion (or both) and histologic grading were recorded. The immunohistochemical staining was performed on paraffin sections and a well-defined scoring system based upon numbers of HER-2 receptors expressed on the cell surface was applied according to standard guidelines. Overall survival (OS) distributions were generated with the Kaplan-Meier method. HER-2 overexpression was detected in 28 of the 47 carcinomas (59.6%). This parameter was demonstrated to be significantly correlated with the shorter OS (P = 0.02). However, the HER-2 overexpression did not show significant correlation with histologic type, tumor grading, or presence of lymphatic invasion. Furthermore, the HER-2 overexpression appeared with a higher percentage in FMCs than what is reported in canine or human mammary carcinomas. The significant correlation with a shorter OS suggests a possible role of HER-2 as an additional marker of malignancy in FMCs and as a reliable prognostic indicator. As in the human oncology practice, the identification of the FMCs that overexpress HER-2 may also promote new therapeutic strategies.

Spontaneous Feline Mammary Carcinoma Is a Model of HER2 Overexpressing Poor Prognosis Human Breast Cancer

Companion animal spontaneous tumors are suitable models for human cancer, primarily because both animal population and the tumors are genetically heterogeneous. Feline mammary carcinoma (FMC) is a highly aggressive, mainly hormone receptor–negative cancer, which has been proposed as a model for poor prognosis human breast cancer. We have identified and studied the feline orthologue of the HER2 gene, which is both an important prognostic marker and therapeutic target in human cancer. Feline HER2 (f-HER2) gene kinase domain is 92% similar to the human HER2 kinase. F-HER2–specific mRNA was found 3- to 18-fold increased in 3 of 3 FMC cell lines, in 1 of 4 mammary adenomas and 6 of 11 FMC samples using quantitative reverse transcription-PCR. Western blot showed that an anti-human HER2 antibody recognized a protein comigrating with the human p185HER2 in FMC cell lines. The same antibodies strongly stained 13 of 36 FMC archival samples. These data show that feline HER2 overexpression qualifies FMC as homologous to the subset of HER2 overexpressing, poor prognosis human breast carcinomas and as a suitable model to test innovative approaches to therapy of aggressive tumors.