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. Canine, hepatoid gland tumours, claudin-7, immunohistochemistry Perianal or hepatoid glands are modified sebaceous glands in canines located mainly in perianal skin but they also occur in the skin lateral to the prepuce, in the dorsal lumbosacral region, along the ventral midline area, and circumferentially around the proximal third of the tail. The cells of the lobules of these glands can be divided into two groups: mature hepatoid cells and peripheral basal reserve cells (Isitior and Weinman 1979). The function of the hepatoid glands is unknown. The perianal glands have been of interest to veterinarians because they frequently give rise to tumours. The proliferative and neoplastic lesions of the hepatoid gland include hyperplasia, adenoma, epithelioma, well differentiated and poorly differentiated carcinoma. The hepatoid gland hyperplasia and adenoma are common lesions in canines and account for 8% to 18% of all canine skin tumours (Goldschmidt and Hendrick 2000). The hepatoid gland epitheliomas are of low-grade malignancy. These neoplasms are characterized by the majority of cells being reserve cells, with fewer hepatoid cells (Goldschmidt and Shofer 1992). Well-differentiated hepatoid gland carcinomas have a similar histological architecture and morphology to adenomas, but infiltrative growth is present at the tumour margins. Small foci of well-differentiated carcinoma may occur within adenomas, which may represent carcinoma in situ. Poorly differentiated carcinomas of the perianal gland are invasive masses comprising trabeculae and cords of large, polygonal cells (Ihrke et al. 2006). Claudins are a relatively large family of 17–27 kDa integral membrane tight junction tetraspanin proteins that are classified on the basis of the size of the molecules that pass through the paracellular spaces between epithelial and endothelial cells. Tight junctions are the most apical cell-cell contacts and are important for barrier function in epithelial and endothelial cells (Tsukita and Furuse 2002; Tsukita et al. 2001). The claudin family consists of at least 24 members (Morita et al. 1999). Claudins encode proteins with four ACTA VET. BRNO 2010, 79: 127–133; doi:10.2754/avb201079010127 Address for correspondence: Csaba Jakab Szent István University, Faculty of Veterinary Science Department of Pathology and Forensic Veterinary Medicine 1078 István utca 2., Budapest, Hungary Phone: +36-1-478-4181 Fax: +36-1-478-4284 E-mail: [email protected] http://www.vfu.cz/acta-vet/actavet.htm transmembrane domains, and their Nand C-terminal ends are located in the cytoplasm. Claudin molecules interact with each other through homoand heterophilic interactions. In addition, the C-terminal domain of claudins also serves as a binding site of PDZ domain proteins that are potentially involved in signalling (Hamazaki et al. 2002). The aim of the present study was to characterise the expression pattern of claudin-7 tight junction protein in canine intact hepatoid glands and in proliferative lesions of this gland including nodular hyperplasia, adenoma, epithelioma, well-differentiated carcinoma and poorly differentiated carcinoma. Materials and Methods