Mammary neoplasms represent the second most frequent neoplasm in dogs, and since there are no reports on the study of connexins in canine mammary glands, the present study investigated the expression of connexins 26 and 43 in normal, hyperplastic, and neoplastic mammary glands of this species, to verify if altered patterns of connexin staining are related to higher cell proliferation and malignant phenotypes.
A total of 4 normal, 8 hyperplastic mammary glands, 9 benign, and 51 malignant mammary gland neoplasms were submitted for the immunostaining of connexins 26 and 43, E-cadherin, and proliferating cell nuclear antigen (PCNA).
Normal, hyperplastic, and benign neoplastic mammary glands showed a punctate pattern for connexin 26 and 43 staining and an intercellular E-cadherin staining.
Malignant neoplasms, especially the most aggressive cases with high cell proliferation rates, presented either fewer gap junction spots on the cell membranes or increased cytoplasmic immunostaining.
Malignant tumors also expressed a less intense immunostaining of E-cadherin; the expression of this adhesion molecule is important for the transportation of connexins to cell membranes and in forming communicating gap junctions.
Deficient expression of E-cadherin could be related to the aberrant connexin localization and may contribute to the malignant phenotype.
In conclusion, the expression and distribution of connexins and E-cadherin are inversely correlated to cell proliferation in malignant mammary neoplasms of dogs and may well be related to their more aggressive histologic type and biologic behavior.
Source: Torres LN, Matera JM, Vasconcellos CH, Avanzo JL, Hernandez-Blazquez FJ, Dagli ML. (2005): Expression of connexins 26 and 43 in canine hyperplastic and neoplastic mammary glands. In: Vet Pathol. 2005 Sep;42(5):633-41.
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