TIM-3 Is a Potential Immune Checkpoint Target in Cats with Mammary Carcinoma

Recent findings in human breast cancer (HBC) indicate that T-cell immunoglobulin and mucin-domain-containing molecule-3 (TIM-3)-targeted therapies may effectively activate anticancer immune responses. Although feline mammary carcinoma (FMC) is a valuable cancer model, no studies on TIM-3 have been developed in this species. Thus, we evaluated the expression of TIM-3 by immunohistochemistry in total (t), stromal (s), and intra-tumoral (i) tumor-infiltrating lymphocytes (TILs) and in cancer cells, of 48 cats with mammary carcinoma. In parallel, serum TIM-3 levels were quantified using ELISA and the presence of somatic mutations in the TIM-3 gene was evaluated in 19 tumor samples. sTILs-TIM3+ were more frequent than iTILs-TIM-3+, with the TIM-3 ex-pression in sTILs and cancer cells being associated with more aggressive clinicopathological features. In contrast, the TIM-3 expression in iTILs and tTILs was associated with a more benign clinical course. Moreover, the serum TIM-3 levels were lower in animals with FMC when compared to healthy animals (p < 0.001). Only one somatic mutation was found in the TIM-3 gene, at intron 2, in one tumor sample. Altogether, our results suggest that the expression of TIM-3 among TILs subpopulations and cancer cells may influence the clinical outcome of cats with FMC, in line with the previous reports in HBC.

Comparative gene expression study highlights molecular similarities between triple negative breast cancer tumours and feline mammary carcinomas

Triple negative breast cancer (TNBC) is a rare, highly metastatic subtype of breast cancer that typically develops tumours of a high histological grade. As TNBC is negative for the oestrogen, progesterone and HER2 receptors it is also not eligible for targeted hormonal therapies. Therefore, those diagnosed with TNBC are faced with a very poor prognosis. Feline mammary carcinomas (FMCs) have been shown to share key characteristics of TNBC and are being investigated as novel animal models of this disease. A study by Granados‐Soler et al., investigating prognostic markers of FMCs provided the basis of this research, and their prognostic value in TNBC was evaluated using a ‘data‐mining’ research approach. Overall, the comparative genomic aspect of this research identified several potential prognostic markers translatable across TNBC and FMCs. These prognostic markers warrant further investigation in comparative oncology studies.

VISTA Is a Diagnostic Biomarker and Immunotherapy Target of Aggressive Feline Mammary Carcinoma Subtypes

Simple Summary

Mammary tumors are common in cats, showing aggressive behavior and few therapeutic options. Recently, feline mammary carcinomas have become a reliable cancer model for human breast cancer studies, due to the similarities between the two species. Thus, the identification of new tumor biomarkers and therapeutic targets to improve cat’s prognosis is needed. VISTA is an important immune checkpoint protein that has gained importance over the past few years in women’s cancers. In this study, the serum VISTA levels and tumor expression were analyzed in cats with mammary tumors, being correlated with other immune checkpoints. In the diseased animals, VISTA is overexpressed in more aggressive tumor subtypes (HER2-positive and triple-negative), showing a positive correlation with the expression of VISTA in tumor-infiltrating lymphocytes, and is associated with an immunosuppressive status, suggesting that VISTA could be a promising non-invasive prognostic biomarker and therapeutic target in cats with mammary carcinomas, as reported in humans.

Abstract

Feline mammary carcinoma (FMC) is a common neoplasia, showing aggressive clinicopathological features, without viable therapeutic options. The study of tumor microenvironment has gained importance, due to the ability to control tumor progression by regulating the immune response. Considering the lack of knowledge, feline serum VISTA levels from cats with mammary carcinoma were compared with healthy controls, and with serum levels of PD-1/PD-L1, CTLA-4, LAG-3, IL-6, and TNF-α. In parallel, VISTA tumor expression was evaluated in FMC samples. The obtained data revealed that serum VISTA levels were significantly higher in cats presenting HER2-positive (p = 0.0025) or triple-negative subtypes (p = 0.0019), with higher serum levels in luminal A (p = 0.0025) correlated to the presence of metastasis (p = 0.0471). Furthermore, in HER2-positive or triple-negative tumors, correlations were obtained between serum VISTA levels and the serum levels of the above-mentioned molecules. In tumors, VISTA expression revealed a stronger intensity in cancer cells, when compared to TILs (p < 0.0001). Stratifying the samples by subtypes, a higher number of VISTA-positive TILs was observed in the HER2-positive subtype, compared with triple-negative tumors (p = 0.0138). In conclusion, results support the development of therapeutic strategies for HER2-positive and triple-negative FMC subtypes, reinforcing the use of cats as a human oncology model.

Emerging Biomarkers and Targeted Therapies in Feline Mammary Carcinoma

Feline mammary carcinoma (FMC) is a common aggressive malignancy with a low survival rate that lacks viable therapeutic options beyond mastectomy. Recently, increasing efforts have been made to understand the molecular mechanisms underlying FMC development, using the knowledge gained from studies on human breast cancer to discover new diagnostic and prognostic biomarkers, thus reinforcing the utility of the cat as a cancer model. In this article, we review the current knowledge on FMC pathogenesis, biomarkers, and prognosis factors and offer new insights into novel therapeutic options for HER2-positive and triple-negative FMC subtypes.

Anaplastic Mammary Carcinoma in Cat

Clinical, pathological, and immunohistochemical findings related to a feline mammary tumor with similar features to canine anaplastic mammary carcinoma are herein described for the first time. A female cat was presented for clinical evaluation with gastrointestinal signs, oedema, erythema, and painful lesion in the right inguinal region. Three weeks later, the mass had doubled in size and radiographic revaluation of the thoracic cavity revealed a metastatic pattern. Due to the poor prognosis and decline of the clinical status the owners decided for euthanasia. Post-mortem examination exposed a mammary tumoral mass with subcutaneous oedema, an enlargement of the right inguinal lymph node, and nodules in several organs. Histological analysis confirmed the presence of large pleomorphic epithelial cells, often grouped in small clusters with bizarre nuclei. Immunohistochemical study of the different lesions was performed and both primary tumor and regional metastasis showed tumor cells to be negative estrogen receptor alpha, positive progesterone receptor, positive HER-2, and positive pan-cytokeratin. Given that the clinical history was compatible with an inflammatory mammary carcinoma, the cyclooxygenase-2 expression levels were evaluated and presented a weak immunoreactivity. Regarding the distant metastatic lesions, tumor cells were negative for ER-α and PR and, positive both for HER-2 and pan-cytokeratin.

HER2-Targeted Immunotherapy and Combined Protocols Showed Promising Antiproliferative Effects in Feline Mammary Carcinoma Cell-Based Models

Simple Summary

Mammary tumors are common in cats, presenting an aggressive behavior with high tumor recurrence. Therefore, new and efficient therapeutic protocols are urgent. Monoclonal antibodies (mAbs; ADC) are widely used in human breast cancer therapy, inhibiting the HER2 dimerization and leading to cell apoptosis. Furthermore, drug combinations, with tyrosine kinase inhibitors (TKi) are valuable in patients’ therapeutic protocols. In this study, two mAbs, and an ADC, as well as combined protocols between mAbs and mAbs plus lapatinib (TKi) were tested to address if the drugs could be used as new therapeutic options in feline mammary tumors. All the compounds and the combined treatments revealed valuable antiproliferative effects, and a conserved cell death mechanism, by apoptosis, in the feline cell lines, where the mutations found in the extracellular domain of the HER2 suggest no immunotherapy resistance.

Abstract

Feline mammary carcinoma (FMC) is a highly prevalent tumor, showing aggressive clinicopathological features, with HER2-positive being the most frequent subtype. While, in human breast cancer, the use of anti-HER2 monoclonal antibodies (mAbs) is common, acting by blocking the extracellular domain (ECD) of the HER2 protein and by inducing cell apoptosis, scarce information is available on use these immunoagents in FMC. Thus, the antiproliferative effects of two mAbs (trastuzumab and pertuzumab), of an antibody–drug conjugate compound (T-DM1) and of combined treatments with a tyrosine kinase inhibitor (lapatinib) were evaluated on three FMC cell lines (CAT-MT, FMCm and FMCp). In parallel, the DNA sequence of the her2 ECD (subdomains II and IV) was analyzed in 40 clinical samples of FMC, in order to identify mutations, which can lead to antibody resistance or be used as prognostic biomarkers. Results obtained revealed a strong antiproliferative effect in all feline cell lines, and a synergistic response was observed when combined therapies were performed. Additionally, the mutations found were not described as inducing resistance to therapy in breast cancer patients. Altogether, our results suggested that anti-HER2 mAbs could become useful in the treatment of FMC, particularly, if combined with lapatinib, since drug-resistance seems to be rare.

Tyrosine Kinase Inhibitors Are Promising Therapeutic Tools for Cats with HER2-Positive Mammary Carcinoma

Feline mammary carcinoma (FMC) is a common neoplasia in cat, being HER2-positive the most prevalent subtype. In woman’s breast cancer, tyrosine kinase inhibitors (TKi) are used as a therapeutic option, by blocking the phosphorylation of the HER2 tyrosine kinase domain. Moreover, clinical trials demonstrated that TKi produce synergistic antiproliferative effects in combination with mTOR inhibitors, overcoming resistance to therapy. Thus, to uncover new chemotherapeutic strategies for cats, the antiproliferative effects of two TKi (lapatinib and neratinib), and their combination with a mTOR inhibitor (rapamycin), were evaluated in FMC cell lines (CAT-M, FMCp and FMCm) and compared with a human breast cancer cell line (SkBR-3). Results revealed that both TKi induced antiproliferative effects in all feline cell lines, by blocking the phosphorylation of EGFR members and its downstream effectors. Furthermore, combined treatments with rapamycin presented synergetic antiproliferative effects. Additionally, the DNA sequence of the her2 TK domain (exons 18 to 20) was determined in 40 FMC tissue samples, and despite several mutations were found none of them were described as inducing resistance to therapy. Altogether, our results demonstrated that TKi and combined protocols may be useful in the treatment of cats with mammary carcinomas, and that TKi-resistant FMC are rare.

Histone Deacetylase Inhibitors and Microtubule Inhibitors Induce Apoptosis in Feline Luminal Mammary Carcinoma Cells

Simple Summary

Feline mammary tumors (FMT) are very common in cats, associated with very aggressive behavior and a short life expectancy. Surgery is the most used treatment but tumor recurrence is common. Currently, available therapies are insufficient, therefore, new molecular targets are needed to develop more efficient therapeutics. Histone deacetylases inhibitors (HDACis) have been developed to target tumor cells, by disrupting gene expression and leading to cell death. Microtubules inhibitors (MTIs) have also been a focus of research, to target polymerization of microtubules, and consequently disturbing the cytoskeleton and leading to cell cycle arrest and apoptosis. However, there are few studies on the use of HDACis and MTIs in cats. In this study, we addressed if these two drug classes could be used as new therapeutic options in FMTs. All HDACis and MTIs exhibited suitable and dose-dependent antitumor effects in FMT cell lines. Immunoblot analysis confirmed that the mode of action of HDACis is conserved in feline mammary tumor cell lines. Finally, flow cytometry showed that exposure with HDACis and MTIs lead to the induction of cellular apoptosis. In summary, HDACis and MTIs possess antitumor properties suggesting further studies on their use in the treatment of feline mammary tumors.

Abstract

Feline mammary carcinoma (FMC) is the third most common type of neoplasia in cats, sharing similar epidemiological features with human breast cancer. In humans, histone deacetylases (HDACs) play an important role in the regulation of gene expression, with HDAC inhibitors (HDACis) disrupting gene expression and leading to cell death. In parallel, microtubules inhibitors (MTIs) interfere with the polymerization of microtubules, leading to cell cycle arrest and apoptosis. Although HDACis and MTIs are used in human cancer patients, in cats, data is scarce. In this study, we evaluated the antitumor properties of six HDACis (CI-994, panobinostat, SAHA, SBHA, scriptaid, and trichostatin A) and four MTIs (colchicine, nocodazole, paclitaxel, and vinblastine) using three FMC cell lines (CAT-MT, FMCp, and FMCm), and compared with the human breast cancer cell line (SK-BR-3). HDACis and MTIs exhibited dose-dependent antitumor effects in FMC cell lines, and for all inhibitors, the IC50 values were determined, with one feline cell line showing reduced susceptibility (FMCm). Immunoblot analysis confirmed an increase in the acetylation status of core histone protein HDAC3 and flow cytometry showed that HDACis and MTIs lead to cellular apoptosis. Overall, our study uncovers HDACis and MTIs as promising anti-cancer agents to treat FMCs.

Serum and Tissue Expression Levels of Leptin and Leptin Receptor Are Putative Markers of Specific Feline Mammary Carcinoma Subtypes

Obesity is an established risk factor for breast cancer in post-menopausal women, being associated with elevated serum levels of leptin. Although overweight is a common condition in cat, the role of leptin and its receptor in feline mammary carcinoma remains unsettled. In this study, serum leptin and leptin receptor (ObR) levels were investigated in 58 cats with mammary carcinoma and compared with those of healthy animals, as were the expression levels of leptin and ObR in tumor tissues. The results showed that the Free Leptin Index is significantly decreased in cats with mammary carcinoma (p = 0.0006), particularly in those with luminal B and HER2-positive tumors, and that these animals also present significantly lower serum leptin levels (p < 0.0001 and p < 0.005, respectively). Interestingly, ulcerating tumors (p = 0.0005) and shorter disease-free survival (p = 0.0217) were associated to serum leptin levels above 4.17 pg/mL. In contrast, elevated serum ObR levels were found in all cats with mammary carcinoma (p < 0.0001), with levels above 16.89 ng/mL being associated with smaller tumors (p = 0.0118), estrogen receptor negative status (p = 0.0291) and increased serum levels of CTLA-4 (p = 0.0056), TNF-α (p = 0.0025), PD-1 (p = 0.0023), and PD-L1 (p = 0.0002). In tumor samples, leptin is overexpressed in luminal B and triple-negative carcinomas (p = 0.0046), whereas ObR is found to be overexpressed in luminal B tumors (p = 0.0425). Altogether, our results support the hypothesis that serum levels of leptin and ObR can be used as biomarkers of specific feline mammary carcinoma subtypes, and suggests the use of leptin antagonists as a therapeutic tool, reinforcing the utility of the cat as a cancer model.

Immunoexpression and Prognostic Significance of Multidrug Resistance Markers in Feline Mammary Carcinomas

Feline mammary carcinomas (FMCs) are commonly characterized by high clinical aggressiveness and poor prognosis. FMCs share many features with the corresponding human disease, allowing the comparative investigation of tumour biology and therapeutic strategies, including multidrug resistance (MDR) mechanisms. Although transporting/binding proteins, including permeability glycoprotein (P-gp), lung resistance protein (LRP) and metallothionein (MT), are frequently associated with tumour aggressiveness and unresponsiveness to chemotherapy in human breast cancer, they have not been analysed in FMCs. We investigated the immunoexpression of P-gp, LRP and MT in FMCs and their correlation with clinicopathological parameters and overall survival (OS) time in 46 FMCs, with a median follow-up period of 289 days. These markers were co-expressed in 85% of tumours. P-gp was expressed in 93.4% of FMCs and was positively associated with tumour grade (P = 0.049). While unequivocally observed in all FMCs, LRP immunoexpression did not correlate with any clinicopathological parameters or OS. Expression of MT was significant in triple-negative basal- and normal-like molecular subtypes of FMCs (P = 0.023). The concurrent expression of MDR proteins indicates the potential existence of chemotherapy resistance-related mechanisms in FMCs. The positive association between P-gp and MT immunoexpression and aggressive phenotypes could open new therapeutic and translational strategies for FMCs.

Diagnostic Value of VEGF-A, VEGFR-1 and VEGFR-2 in Feline Mammary Carcinoma

Vascular endothelial growth factor (VEGF-A) plays an essential role in tumor-associated angiogenesis, exerting its biological activity by binding and activating membrane receptors, as vascular endothelial growth factor receptor 1 and 2 (VEGFR-1, VEGFR-2). In this study, serum VEGF-A, VEGFR-1, and VEGFR-2 levels were quantified in 50 cats with mammary carcinoma and 14 healthy controls. The expression of these molecules in tumor-infiltrating lymphocytes (TILs) and in cancer cells was evaluated and compared with its serum levels. Results obtained showed that serum VEGF-A levels were significantly higher in cats with HER2-positive and Triple Negative (TN) Normal-Like subtypes, when compared to control group (p = 0.001, p = 0.020). Additionally, serum VEGFR-1 levels were significantly elevated in cats presenting luminal A, HER2-positive and TN Normal-Like tumors (p = 0.011, p = 0.048, p = 0.006), as serum VEGFR-2 levels (p = 0.010, p = 0.046, p = 0.005). Moreover, a positive interaction was found between the expression of VEGF-A, VEGFR-1, and VEGFR-2 in TILs and their serum levels (p = 0.002, p = 0.003, p = 0.003). In summary, these findings point to the usefulness of VEGF-A and its serum receptors assessment in clinical evaluation of cats with HER2-positive and TN Normal-Like tumors, suggesting that targeted therapies against these molecules may be effective for the treatment of these animals, as described in human breast cancer.

Serum PD-1/PD-L1 Levels, Tumor Expression and PD-L1 Somatic Mutations in HER2-Positive and Triple Negative Normal-Like Feline Mammary Carcinoma Subtypes

Tumor microenvironment has gained great relevance due to its ability to regulate distinct checkpoints mediators, orchestrating tumor progression. Serum programmed cell death protein-1 (PD-1) and programmed death ligand-1 (PD-L1) levels were compared with healthy controls and with serum cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and tumor necrosis factor-alpha (TNF-α) levels in order to understand the role of PD-1/PD-L1 axis in cats with mammary carcinoma. PD-1 and PD-L1 expression was evaluated in tumor-infiltrating lymphocytes (TILs) and cancer cells, as the presence of somatic mutations. Results showed that serum PD-1 and PD-L1 levels were significantly higher in cats with HER2-positive (p = 0.017; p = 0.032) and triple negative (TN) normal-like mammary carcinomas (p = 0.004; p = 0.015), showing a strong positive correlation between serum CTLA-4 and TNF-α levels. In tumors, PD-L1 expression in cancer cells was significantly higher in HER2-positive samples than in TN normal-like tumors (p = 0.010), as the percentage of PD-L1-positive TILs (p = 0.037). PD-L1 gene sequencing identified two heterozygous mutations in exon 4 (A245T; V252M) and one in exon 5 (T267S). In summary, results support the use of spontaneous feline mammary carcinoma as a model for human breast cancer and suggest that the development of monoclonal antibodies may be a therapeutic strategy.

Identification of an immune-suppressed subtype of feline triple-negative basal-like invasive mammary carcinomas, spontaneous models of breast cancer

Feline invasive mammary carcinomas are characterized by their high clinical aggressiveness, rare expression of hormone receptors, and pathological resemblance to human breast cancer, especially triple-negative breast cancer (negative to estrogen receptor, progesterone receptor, and epidermal growth factor receptor type 2). Recent gene expression studies of triple-negative breast cancers have highlighted their heterogeneity and the importance of immune responses in their biology and prognostic assessment. Indeed, regulatory T cells may play a crucial role in producing an immune-suppressed microenvironment, notably in triple-negative breast cancers. Feline invasive mammary carcinomas arise spontaneously in immune-competent animals, in which we hypothesized that the immune tumor microenvironment also plays a role. The aims of this study were to determine the quantity and prognostic value of forkhead box protein P3-positive peritumoral and intratumoral regulatory T cells in feline invasive mammary carcinomas, and to identify an immune-suppressed subgroup of triple-negative basal-like feline invasive mammary carcinomas. One hundred and eighty female cats with feline invasive mammary carcinomas, treated by surgery only, with 2-year follow-up post-mastectomy, were included in this study. Forkhead box protein P3, estrogen receptor, progesterone receptor, Ki-67, epidermal growth factor receptor type 2, and cytokeratin 14 expression were assessed by automated immunohistochemistry. Peritumoral regulatory T cells were over 300 times more abundant than intratumoral regulatory T cells in feline invasive mammary carcinomas. Peritumoral and intratumoral regulatory T cells were associated with shorter disease-free interval and overall survival in both triple-negative (ER-, PR-, HER2-, N = 123 out of 180) and luminal (ER+ and/or PR+, N = 57) feline invasive mammary carcinomas. In feline triple-negative basal-like (CK14+) mammary carcinomas, a regulatory T-cell-enriched subgroup was associated with significantly poorer disease-free interval, overall survival, and cancer-specific survival than regulatory T-cell-poor triple-negative basal-like feline invasive mammary carcinomas. High regulatory T-cell numbers had strong and negative prognostic value in feline invasive mammary carcinomas, especially in the triple-negative basal-like subgroup, which might contain a "basal-like immune-suppressed" subtype, as described in triple-negative breast cancer. Cats with feline invasive mammary carcinomas may thus be interesting spontaneous animal models to investigate new strategies of cancer immunotherapy in an immune-suppressed tumor microenvironment.

HER2 Amplification Status in Feline Mammary Carcinoma: A Tissue Microarray-Fluorescence In Situ Hydridization-Based Study

Human epidermal growth factor receptor 2 (HER2) is a tyrosine kinase receptor overexpressed in a subset of breast cancer due to HER2 gene amplification. HER2 protein is expressed in feline mammary carcinomas, but little is known about its cytogenetic alterations. The aim of this study was to evaluate HER2 gene amplification status and its correlation with HER2 protein expression in feline mammary carcinomas. Feline mammary carcinomas were retrospectively selected and immunohistochemically (IHC) evaluated for HER2 protein expression. All the HER2 IHC-positive (3+) and equivocal (2+) cases and a subset of negative cases (0/1+) were selected for fluorescence in situ hybridization (FISH). Dual-core tissue microarrays were prepared for FISH. IHC and FISH were evaluated according to the 2013 American Society of Clinical Oncology/College of American Pathologists guidelines. The study included 107 feline mammary carcinomas from 88 queens. HER2 protein expression was positive (3+) in 7 cases (6.5%), equivocal (2+) in 48 cases (45%), and negative (0/1+) in 52 cases (48.5%). HER2 status was indeterminate in 8 feline mammary carcinomas (12%), amplified in 3 (4%), equivocal in 4 (6%), and nonamplified in 53 (78%). HER2 gene amplification and protein expression were significantly positively correlated ( R = 0.283; P < .0001). HER2 gene is amplified in a subset of feline mammary carcinomas despite the HER2 positive or equivocal protein expression, but it remains to be determined if the HER2 amplification is a gene alteration that drives mammary tumor carcinogenesis or only a bystander passenger mutation.

Serum SDF-1 levels are a reliable diagnostic marker of feline mammary carcinoma, discriminating HER2-overexpressing tumors from other subtypes

The feline mammary carcinoma (FMC) is the third most common tumor in cat, sharing many clinicopathological features with human breast cancer and thus, considered a suitable model for comparative oncology. Due to its poor prognosis, further studies are required to improve the diagnostic accuracy and treatment of cats with spontaneous mammary carcinoma. Recently, it was reported that the overexpression of stromal cell-derived factor-1 (SDF-1) has great value in human breast cancer diagnosis, suggesting that diagnostic tools and therapies targeting the SDF-1 ligand can improve the clinical outcome. In this study, we aimed to evaluate if serum SDF-1 levels can also be used as a biomarker of mammary carcinoma in cats and to analyze if serum SDF-1 levels are associated with clinicopathological features, linked to a specific FMC subtype or correlated with the tumor expression of SDF-1 receptor, the chemokine C-X-C motif receptor 4 (CXCR4). Results showed that cats with mammary carcinoma had significantly higher serum SDF-1 levels than healthy controls (p=0.035) and ROC analysis revealed that the best cut-off value to differentiate sick from healthy animals was 2 ng/ml (specificity: 80%; sensitivity: 57%; AUC=0.715). Significant associations were also found between cats with elevated serum SDF-1 concentrations (≥ 2 ng/ml) and HER2-overexpressing mammary carcinomas (Luminal B-like and HER2-positive subtypes, p<0.0001), CXCR4-negative mammary carcinomas (p=0.027), mammary carcinomas with small size (<3 cm, p=0.027) and tumors with low Ki-67 expression (p=0.012). No statistical associations were found between serum SDF-1 levels and overall or disease-free survival. In summary, our results show that serum SDF-1 levels can be used as a biomarker of feline mammary carcinoma, especially in cats with HER2-overexpressing mammary tumors. Data suggest that targeted therapies against the SDF-1 ligand and/or its CXC4 receptor may be effective for the treatment of FMC, as described for human breast cancer, strengthening the concept that spontaneous feline mammary carcinoma is a suitable model for comparative oncology.

Immunohistochemical Expression Profiles of Cell Adhesion Molecules, Matrix Metalloproteinases and their Tissue Inhibitors in Central and Peripheral Neoplastic Foci of Feline Mammary Carcinoma

Feline mammary carcinoma (FMC) is a common cancer with high metastatic potential and high mortality rate. Loss of cell-cell interactions and degradation of the extracellular matrix by proteinases enhances tumour invasion and metastasis. Peripheral neoplastic foci (PNF) are defined as the presence of discrete tumour cell clusters, splitting off from central neoplastic foci (CNF) and lodging around these CNF. PNF therefore locate at the tumour-host interface at the site of invasion. The aim of this study was to evaluate immunohistochemically the expression of cell adhesion molecules (e-cadherin [CDH-1], syndecan 1 [SDC-1] and nectin-2), matrix metalloproteinases (matrix metalloproteinase [MMP]-2, MMP-7 and MMP-9) and their tissue inhibitors (tissue inhibitor of matrix metalloproteinase [TIMP]-1 and TIMP-2) together with the cellular proliferation marker, Ki67, in CNF and PNF of FMCs of different clinical stages and histological grades. Compared with control sections from areas of mammary gland hyperplasia, lower expression of MMP-7 and TIMP-2 was observed in all stages. Increased expression of TIMP-1 was observed in PNF in early-stage disease with no metastasis, while marked expression of CDH-1 and Ki67 occurred in late-stage FMC. In addition, the expression of MMP-2, MMP-9 and TIMP-1 in PNF of tumours with high histological grade (grade III) was higher than in low-grade tumours. The observed divergent protein expression in PNF could potentially form the basis of acting as novel markers in FMC. Potential markers may include the expression of TIMP-1 in PNF in early stage lesions, the expression of CDH-1 and Ki67 in late stages and the expression of MMP-2, MMP-9 and TIMP-1 in high-grade tumours.

Ki-67 as a Prognostic Factor in Feline Mammary Carcinoma: What Is the Optimal Cutoff Value?

Ki-67 is a nuclear protein and a proliferation marker frequently used in establishing the prognosis for breast cancer patients. To investigate the prognostic value of the Ki-67 proliferation index in female cats with mammary carcinoma, a prospective study was conducted with 96 animals. The Ki-67 index of primary tumors (n = 96) was initially determined, and whenever possible, the Ki-67 index of regional lymph node metastasis (n = 38) and distant metastasis (n = 16) was also estimated. The optimal cutoff value for the Ki-67 index was determined by univariate and multivariate analysis. Ki-67 indices ≥ 14% were detected in 72.9% (70 of 96) of the tumors. Tumors with a Ki-67 index ≥ 14% were significantly associated with large size (P = .022), poor differentiation (P = .009), presence of necrotic areas (P = .008), estrogen receptor-negative status (P < .0001), fHER2-negative status (P = .003), and shorter overall survival (P = .012). Moreover, Ki-67 expression in the primary tumor was strongly and positively correlated with both regional metastasis (P < .0001; r = 0.83) and distant metastasis (P < .0001; r = 0.83), and was significantly higher in distant metastases when compared with the primary tumor (P = .0009). A similar correlation was also observed between regional and distant metastasis (P < .0001; r = 0.75). On the basis of the above results, the authors propose the adoption of the 14% value as the optimal cutoff for Ki-67 to identify tumors with high risk of disease progression.

Prognostic value of histologic grading for feline mammary carcinoma: a retrospective survival analysis

Feline mammary carcinoma is highly malignant and generally associated with a poor prognosis, although studies suggest the range of survival times in affected cats is broad. Histologic grading of these tumors is achieved using the Elston and Ellis system, originally developed for human breast cancer. In cats, however, classification using this method has variable prognostic value. Therefore, objectives of this study were (1) to evaluate the Elston and Ellis grading system for feline mammary carcinoma in a predominantly spayed population and (2) to determine whether modification of this system or development of a novel system improved the prognostic value of histologic grading. Survey data and histologic features for 108 carcinomas from 97 cats were analyzed with respect to overall survival. Elston and Ellis grading failed to correlate significantly with overall survival. Using multivariable analysis, lymphovascular invasion, nuclear form, and mitotic count each demonstrated independent prognostic significance (P = .008, <.001, and .004, respectively). Modifications of the Elston and Ellis system and a novel grading system were proposed based on these results; all showed significant correlation with overall survival (P < .001). Median survival times were 27, 29, or 31 months for grade I; 14, 12, or 14 months for grade II; and 13, 5, or 8 months for grade III carcinomas using the mitotic-modified Elston and Ellis, the revised Elston and Ellis, or the novel grading system, respectively. Based on this retrospective study, adoption of the species-specific systems as proposed here may improve the prognostic value of histologic grading for feline mammary carcinoma.