Expression of claudin-1, -2, -3, -4, -5 and -7 proteins in benign and malignant canine mammary gland epithelial tumours

Identifying luminal and basal mammary cell specific genes and their expression patterns during pregnancy

Mammary gland is present in all mammals and usually functions in producing milk to feed the young offspring. Mammogenesis refers to the growth and development of mammary gland, which begins at puberty and ends after lactation. Pregnancy is regulated by various cytokines, which further contributes to mammary gland development. Epithelial cells, including basal and luminal cells, are one of the major components of mammary gland cells. The development of basal and luminal cells has been observed to significantly differ at different stages. However, the underlying mechanisms for differences between basal and luminal cells have not been fully studied. To explore the mechanisms underlying the differentiation of mammary progenitors or their offspring into luminal and myoepithelial cells, the single-cell sequencing data on mammary epithelia cells of virgin and pregnant mouse was deeply investigated in this work. We evaluated features by using Monte Carlo feature selection and plotted the incremental feature selection curve with support vector machine or RIPPER to find the optimal gene features and rules that can divide epithelial cells into four clusters with different cell subtypes like basal and luminal cells and different phases like pregnancy and virginity. As representations, the feature genes Cldn7, Gjb6, Sparc, Cldn3, Cited1, Krt17, Spp1, Cldn4, Gjb2 and Cldn19 might play an important role in classifying the epithelial mammary cells. Notably, seven most important rules based on the combination of cell-specific and tissue-specific expressions of feature genes effectively classify the epithelial mammary cells in a quantitative and interpretable manner.

Ablation of Red Stable Transfected Claudin Expressing Canine Prostate Adenocarcinoma and Transitional Cell Carcinoma Cell Lines by C-CPE Gold-Nanoparticle-Mediated Laser Intervention

Claudin (CLDN) proteins are commonly expressed in cancers and targeted in novel therapeutic approaches. The C-terminal of Clostridium perfringens enterotoxin (C-CPE) efficiently binds several claudins. In this study, recombinant C-CPE conjugated to gold nanoparticles (AuNPs) has been used for prostate adenocarcinoma (PAC) and transitional cell carcinoma (TCC) cell killing in vitro using gold-nanoparticle-mediated laser perforation (GNOME-LP). A PAC and TCC cell lines, as well as red fluorescence variants, allowing deep tissue imaging, were used. CLDN-3, -4, and -7 expression was confirmed by qPCR and immunofluorescences. The binding of C-CPE-AuNPs complexes on the cell surface was examined by scanning electron microscopy (SEM). Further, transcriptome analysis was carried out to evaluate the effect of C-CPE binder on the biological response of treated cells. Directed C-CPE-AuNP binding verified the capability to target CLDN receptors. Transcriptome analysis showed that C-CPE binding may activate immune and inflammatory responses but does not directly affect cell survival. Cancer cells ablation was demonstrated using a combination of GNOME-LP and C-CPE-AuNPs treatment reducing tumor cell viability to less than 10% depending on cell line. The fluorescent cell lines and the verified proof of concept in vitro provide the basis for perspective xenograft studies in an animal model.

Determining the expression levels of circulating tumour cell markers in canine mammary tumours

Detection of the circulating tumour cells (CTC) in dogs with a mammary tumour is a useful tool to reveal the micrometastases long before metastases are recognised clinically. The aim of this study was to evaluate the association of the epidermal growth factor receptor (EGFR), claudin 7 (CLND7) and epithelial cell adhesion molecule (EPCAM) with the clinical indices and to reveal the diagnostic importance of these biomarkers in canine mammary tumours (CMTs). Peripheral blood (PB) samples were collected from 45 bitches (group MT) which had single mass with malignant epithelial tumours and 9 healthy bitches (group H). Real time PCR (rt-PCR) was performed to determine the expression levels of EGFR, CLDN7, and EPCAM. Mean values of EGFR and CLDN7 expressions were significantly higher in group MT compared to group H (P < 0.01 and P < 0.001, respectively). The expression level of CLDN7 was positively correlated with EGFR and EPCAM (P < 0.001 and P < 0.05, respectively). The EPCAM expression was associated with increased tumour size (P < 0.05) and EPCAM tended to decrease in the presence of skin ulceration on tumour (P = 0.05). Furthermore, expression levels of EGFR in intact dogs were significantly higher compared to spayed dogs in group MT (P < 0.01). The EGFR expression was significantly higher in the presence of metastases (P < 0.05). Also, increased EGFR was determined in grade 2 compared to grade 1 (P < 0.05). In conclusion, these results show that EGFR, CLDN7, EPCAM markers are measureable in PB and they may provide valuable information about the clinical pathophysiology of CMT.

Hydrostatic pressure incubation affects barrier properties of mammary epithelial cell monolayers, in vitro

During lactation, accumulation of milk in mammary glands (MG) causes hydrostatic pressure (HP) and concentration of bioactive compounds. Previously, a changed expression of tight junction (TJ) proteins was observed in mice MGs by accumulation of milk, in vivo. The TJ primarily determines the integrity of the MG epithelium. The present study questioned whether HP alone can affect the TJ in a mammary epithelial cell model, in vitro. Therefore, monolayers of HC11, a mammary epithelial cell line, were mounted into modified Ussing chambers and incubated with 10 kPa bilateral HP for 4 h. Short circuit current and transepithelial resistance were recorded and compared to controls, and TJ proteins were analyzed by Western blotting and immunofluorescent staining. In our first approach HC11 cells could withstand the pressure incubation and a downregulation of occludin was observed. In a second approach, using prolactin- and dexamethasone-induced cells, a decrease of short circuit current was observed, beginning after 2 h of incubation. With the addition of 1 mM barium chloride to the bathing solution the decrease could be blocked temporarily. On molecular level an upregulation of ZO-1 could be observed in hormone-induced cells, which was downregulated after the incubation with barium chloride. In conclusion, bilateral HP incubation affects mammary epithelial monolayers, in vitro. Both, the reduction of short circuit current and the change in TJ proteins may be interpreted as physiological requirements for lactation.

Longitudinal Claudin Gene Expression Analyses in Canine Mammary Tissues and Thereof Derived Primary Cultures and Cell Lines

Human and canine mammary tumours show partial claudin expression deregulations. Further, claudins have been used for directed therapeutic approaches. However, the development of claudin targeting approaches requires stable claudin expressing cell lines. This study reports the establishment and characterisation of canine mammary tissue derived cell lines, analysing longitudinally the claudin-1, -3, -4 and -7 expressions in original tissue samples, primary cultures and developed cell lines. Primary cultures were derived from 17 canine mammary tissues: healthy, lobular hyperplasia, simple adenoma, complex adenoma, simple tubular carcinoma, complex carcinoma, carcinoma arising in a benign mixed tumour and benign mixed tissue. Cultivation was performed, if possible, until passage 30. Claudin mRNA and protein expressions were analysed by PCR, QuantiGene Plex Assay, immunocytochemistry and immunofluorescence. Further, cytokeratin expression was analysed immunocytochemically. Cultivation resulted in 11 established cell lines, eight showing epithelial character. In five of the early passages the claudin expressions decreased compared to the original tissues. In general, claudin expressions were diminished during cultivation. Three cell lines kept longitudinally claudin, as well as epithelial marker expressions, representing valuable tools for the development of claudin targeted anti-tumour therapies.

Cat Mammary Tumors: Genetic Models for the Human Counterpart

The records are not clear, but Man has been sheltering the cat inside his home for over 12,000 years. The close proximity of this companion animal, however, goes beyond sharing the same roof; it extends to the great similarity found at the cellular and molecular levels. Researchers have found a striking resemblance between subtypes of feline mammary tumors and their human counterparts that goes from the genes to the pathways involved in cancer initiation and progression. Spontaneous cat mammary pre-invasive intraepithelial lesions (hyperplasias and neoplasias) and malignant lesions seem to share a wide repertoire of molecular features with their human counterparts. In the present review, we tried to compile all the genetics aspects published (i.e., chromosomal alterations, critical cancer genes and their expression) regarding cat mammary tumors, which support the cat as a valuable alternative in vitro cell and animal model (i.e., cat mammary cell lines and the spontaneous tumors, respectively), but also to present a critical point of view of some of the issues that really need to be investigated in future research.

Clinicopathological significance of immunoexpression of claudin-1 and claudin-7 in feline mammary carcinomas

Claudins (CLDNs) are tight junction proteins that have a role in regulating cell adhesion and polarity, paracellular permeability, proliferation and differentiation. Several immunohistochemical studies have shown reduced expression of CLDN-1 and CLDN-7 in human and canine mammary carcinomas, suggesting that these proteins may participate in mammary carcinogenesis, invasion and metastasis. The present study characterizes expression of CLDN-1 and CLDN-7 in feline mammary carcinomas (n = 52) and their metastases (n = 29). There was an inverse association between CLDN-7 expression and histological grade of tumour. Reduced expression of CLDN-7 was significantly associated with decreased tubule formation, high proliferative activity and metastasis. No significant associations were found between CLDN-1 expression and any of these features. Evaluation of expression of CLDN-7, but not CLDN-1, may therefore provide prognostic information, assisting in the diagnosis of a subgroup of aggressive feline mammary carcinomas that share some features with the recently described 'claudin-low' subgroup of human breast cancer.

Expression of multidrug resistance membrane transporter (Pgp) and p53 protein in canine mammary tumours

The aim of this study was to determine the expression rate of P-glycoprotein (Pgp), a multidrug resistance marker and the p53 tumour-suppressor protein in canine mammary tumours. A total of 30 tumours were examined in parallel to patient history. The tumours were allotted to four groups: tubulopapillar carcinomas, complex carcinomas, benign tumours, and other malignant tumours. A monoclonal mouse antibody (C494) was used for the immunohistochemical evaluation of Pgp and a polyclonal rabbit antibody for p53. We found that the intact ductal epithelium and connective tissue showed pronounced Pgp expression. The most intensive staining was detected in tubulopapillar carcinomas for both Pgp and p53. The expression rate of Pgp and p53 differed significantly between tubulopapillar carcinoma and complex carcinoma, and between tubulopapillar carcinoma and benign mammary tumour, respectively. The expressions of Pgp and p53 highly correlated statistically; therefore, both can determine malignancy in a similar manner. In the case of tubulopapillar carcinomas, more relapsed tumours occurred than in relation to complex carcinomas and other malignant tumours. Pgp expression rate was proportional to the probability of the tumour becoming recidivant postoperatively, as well. These results suggest that routine evaluation of Pgp expression in canine mammary tumours may be prognostically helpful.

Expression of claudins in the normal canine gastric mucosa

The aim of the present study was to investigate the expression pattern of claudin-1, -2, -3, -4, -5, -7, -8, -10 and -18 in the intact fundic and pyloric gastric mucosa of dogs. Intense, linear, membranous claudin-18 positivity was detected in the surface gastric cells and in the epithelial cells of the gastric glands both in the fundic and pyloric stomach regions. The mucous neck cells in the apical part of the glands, furthermore the parietal cells and chief cells of the basal part of the gland were all positive for claudin-18, in the same way as the enteroendocrine cells. Cells of the basal part of the pyloric glands showed intense, linear, membranous claudin-2 positivity, but cells of the superficial portion of these glands and the surface gastric cells in this region were claudin-2 negative. Fibroblasts, endothelial cells, lymphocytes of the propria layer, smooth muscle cells and vegetative neurons were all negative for claudin-2. All gastric epithelial cells were negative for claudin-1, -3, -4, -5, -6, -7, -8 and -10. The endothelial cells of the propria layer had intense claudin-5 positivity. We assume that claudin-18 forms a paracellular barrier against gastric acid in the healthy canine stomach, in the same way as in mice.

Reduced expression of claudin-2 is associated with high histological grade and metastasis of feline mammary carcinomas

Claudins (CLDNs) are a family of tight junction (TJ) proteins that play an important role in maintaining cell polarity, in controlling paracellular ion flux and in regulating cell proliferation and differentiation. There is a growing body of evidence that associates changes in CLDN expression with the development of human breast cancer. In the present study CLDN-2 expression was examined immunohistochemically in samples of normal feline mammary tissue (n = 5) and mammary carcinomas (n = 52), including metastatic lesions (n = 29). Seventy-seven percent of carcinomas showed reduced CLDN-2 expression compared with that observed in normal mammary gland. Reduced expression of CLDN-2 was significantly associated with a high histological grade of carcinoma (P = 0.011), with 88.6% of grade II/III carcinomas showing decreased expression. Furthermore, CLDN-2 down-regulation was significantly associated with metastatic disease (P = 0.0027), with 93.1% of cases with signs of metastasis showing decreased expression of this protein. CLDN-2 may constitute a molecular marker for identification of a subgroup of feline mammary carcinomas characterized by high histological grade and the development of metastasis.

Optimization of an immunohistochemical method to assess distribution of tight junction proteins in canine epidermis and adnexae

Epidermal tight junctions (TJs) have been well characterized in human medicine. Abnormality of these structures is involved in skin diseases such as atopic dermatitis. There is little information about the expression and distribution of TJ proteins in the canine skin. The aim of this study was to develop an optimal immunohistochemical method for assessment of the expression of TJ proteins in the skin of healthy dogs. Formalin-fixed and paraffin wax-embedded skin biopsy samples from healthy human and canine patients were used. Canine skin samples were from the inguinal region and the nasal planum. Immunohistochemistry was used to study the expression of zonula occludens-1 (ZO-1), occludin and claudin-1, -4 and -7. Heat-induced antigen retrieval with EDTA (pH 9.0) yielded the best labelling of TJ proteins. ZO-1 and occludin were expressed in the cytoplasm and along the keratinocyte membrane, while claudin-1 and -4 were mainly membrane in distribution. ZO-1, occludin and claudin-1 were detected in all epidermal layers with the exception of the stratum corneum, while claudin-4 expression was restricted to the stratum granulosum. Expression of claudin-7 was difficult to evaluate. There was no difference in labelling pattern between inguinal and nasal planum skin.

Claudins and the modulation of tight junction permeability

Claudins are tight junction membrane proteins that are expressed in epithelia and endothelia and form paracellular barriers and pores that determine tight junction permeability. This review summarizes our current knowledge of this large protein family and discusses recent advances in our understanding of their structure and physiological functions.

Altered expression of tight junction proteins in mammary epithelium after discontinued suckling in mice

Milk production is modulated by the paracellular barrier function of tight junction (TJ) proteins located in the mammary epithelium. The aim of our study was the molecular analysis of TJs in native lactating murine mammary gland epithelium as this process may strongly challenge epithelial barrier properties and regulation. Mammary gland tissue specimens from lactating control mice and animals after a 20-h interruption of suckling were prepared; histological analyses were performed by light and electron microscopy; and expression of TJ proteins was detected by PCR, Western blotting, immunofluorescent staining, and confocal laser scanning microscopy. Discontinuation of suckling resulted in a substantial accumulation of milk in mammary glands, an increase of alveolar size, and a flattening of epithelial cells without effects on inflammatory indicators. In control tissues, PCR and Western blots showed signals for occludin, and claudin-1, -2, -3, -4, -5, -7, -8, -15, and -16. After a 20-h accumulation of milk, expression of two sealing TJ proteins, claudin-1 and -3, was markedly increased, whereas two TJ proteins involved in cation transport, claudin-2 and -16, were reduced. Real-time PCR validated increased transcripts of claudin-1 and claudin-3. During extension of mammary glands in the process of lactation, claudin-1 and -3 are markedly induced and claudin-2 and -16 are decreased. Volume and composition of milk might be strongly dependent on this counter-regulation of sealing claudins with permeability-mediating claudins, indicating a physiological process of a tightening of TJs against a back-leak of solutes and ions from the alveolar lumen.

Expression of claudin-5 in canine pancreatic acinar cell carcinoma - An immunohistochemical study

Claudin-5 is an endothelium-specific tight junction protein. The aim of the present study was to detect the expression pattern of this molecule in intact pancreatic tissues and in well-differentiated and poorly differentiated pancreatic acinar cell carcinomas from dogs by the use of cross-reactive humanised anticlaudin-5 antibody. The necropsy samples taken from dogs included 10 nonneoplastic pancreatic tissues, 10 well-differentiated pancreatic acinar cell carcinomas, 10 poorly differentiated pancreatic acinar cell carcinomas, 5 intrahepatic metastases of well-differentiated and 5 intrahepatic metastases of poorly differentiated acinar cell carcinomas. A strong lateral membrane claudin-5 positivity was detected in exocrine cells in all intact pancreas samples. The endocrine cells of the islets of Langerhans and the epithelial cells of the ducts were negative for claudin-5. The endothelial cells of vessels and lymphatic channels in the stroma of the intact pancreas showed strong membrane positivity for this claudin. All well-differentiated exocrine pancreas carcinomas and all poorly-differentiated pancreatic acinar cell carcinoma samples showed a diffuse loss of claudin-5 expression. The claudin-5-positive peritumoural vessels and lymphatic channels facilitated the detection of vascular invasion of the claudin-5-negative cancer cells. In liver metastasis samples, the pancreatic carcinomas were negative for claudin-5. It seems that the loss of expression of claudin-5 may lead to carcinogenesis in canine exocrine pancreatic cells.

Molecular carcinogenesis of canine mammary tumors: news from an old disease

Studies focusing on the molecular basis of canine mammary tumors (CMT) have long been hampered by limited numbers of molecular tools specific to the canine species. The lack of molecular information for CMT has impeded the identification of clinically relevant tumor markers beyond histopathology and the introduction of new therapeutic concepts. Additionally, the potential use for the dog as a model for human breast cancer is debatable until questions are answered regarding cellular origin, mechanisms, and cellular pathways. During the past years, increasing numbers of canine molecular tools have been developed on the genomic, RNA, and protein levels, and an increasing number of studies have shed light on specific aspects of canine carcinogenesis, particularly of the mammary gland. This review summarizes current knowledge on the molecular carcinogenesis of CMT, including the role of specific oncogenes, tumor suppressors, regulators of apoptosis and DNA repair, proliferation indices, adhesion molecules, circulating tumor cells, and mediators of angiogenesis in CMT progression and clinical behavior. Whereas the data available are far from complete, knowledge of molecular pathways has a significant potential to complement and refine the current diagnostic and therapeutic approach to this tumor type. Furthermore, current data show that significant similarities and differences exist between canine and human mammary tumors at the molecular level. Clearly, this is only the beginning of an understanding of the molecular mechanisms of CMT and their application in clinical patient management.

Expression of Claudin-7 Molecule in Canine Perianal GlandTumours

The present study evaluated the expression of claudin-7 in 10 intact perianal gland and 67 hyperplastic and neoplastic lesions of the canine perianal (hepatoid) gland. The results have shown intense typical membrane expression of claudin-7 in intact perianal glands, hyperplasia, adenoma, differentiated and anaplastic carcinoma of this gland. In intact glands, hyperplasias, adenomas of the hepatoid gland, normal, hyperplastic and neoplastic basal cells never expressed claudin-7 molecule. Epitheliomas of the hepatoid gland were negative for claudin-7 molecule. Intense membrane-bound claudin-7 immunoreactivity was found in well-differentiated carcinomas, in addition claudin-7 overexpression in poorly differentiated carcinomas of the canine hepatoid gland. Claudin-7 seems to be one of the integral constituents of tight junction structures of intact perianal gland. In addition, claudin-7 seems to be helpful in distinguishing well-differentiated carcinomas and poorly differentiated carcinomas from epitheliomas of the gland; and in distinguishing well-differentiated carcinomas from adenoma of the perianal gland.

Expression of the claudin-4 molecule in benign and malignant canine hepatoid gland tumours

Claudins are integral membrane proteins of the tight junction structures expressed by epithelial and endothelial cells. The present study has evaluated the expression of claudin-4 in 10 normal canine hepatoid glands and in 67 hepatoid glands with hyperplastic and neoplastic lesions. The lesions studied included normal hepatoid glands (n = 10), nodular hyperplasias (n = 10), adenomas (n = 12), epitheliomas (n = 15), differentiated carcinomas (n = 15) and anaplastic carcinomas (n = 15). There was an intensive expression of claudin-4 in normal canine hepatoid glands as well as in hyperplasias and adenomas. Claudin-4 was detected as a well-localised linear circumferential membranous staining pattern of epithelial cells (mature hepatoid cells) in normal hepatoid glands, perianal gland hyperplasias and adenomas. In nodular hyperplasia and adenoma, the reserve cells showed membrane positivity for the claudin-4 molecule. There was a weaker expression in hepatoid gland epitheliomas. In the epitheliomas, the basaloid reserve cells never expressed the claudin-4 molecule. The multiple small parts of epitheliomas in which the cells exhibited typical hepatoid features showed a well-localised linear circumferential membranous staining pattern for claudin-4. The numerical score for cellular expression of claudin-4 was higher in differentiated carcinomas than in epitheliomas, but moderately lower than in adenomas. The anaplastic, poorly differentiated hepatoid gland carcinomas showed an overexpression of claudin-4. These results suggest that low claudin-4 expression in epitheliomas is a molecular characteristic indicative of increasing cellular disorientation, detachment motility and invasion by tumour cells, and claudin-4 seems to be helpful in distinguishing undifferentiated carcinomas from differentiated carcinomas and epitheliomas of the hepatoid gland. In addition, claudin-4 can help distinguish epithelioma from differentiated carcinoma of the canine hepatoid gland.