Abstract
Incidence of canine mammary carcinoma is two times higher than the rate of human breast cancer. Mammary tumors are the most common type of cancer in intact female dogs and account for about half of all neoplasms in these dogs. Well-established models of breast cancer have shown that neoplastic cells often have a loss of intercellular communication, particularly gap junction proteins. Thus, the objective of this study is to explore the aspect of gap junction intercellular communication in canine mammary carcinoma, non-cancerous (CMEC) and cancerous (CMT12, CMT27, and CF41.Mg) cells, and patient-derived tumors. Both non-cancerous and cancerous mammary cells express connexins 26 and 43 using immunofluorescence; however, the level of expression is significantly different in quantitative analysis using western blot in which connexin 43 in both CMT12 and CMT27 is significantly decreased compared to CMEC. Furthermore, a decrease of gap junction capacity in CMT12 and CMT27 was observed compared to CMEC. Immunostaining of CMT27-xenograft tumors revealed positive Cx26 and negative Cx43 expression. Similarly, immunostaining of spontaneous canine mammary tumors revealed that Cx26 is present in all tumors while Cx43 is present in 25% of tumors. Overall, the study provides for the first time that a differential pattern of connexin expression exists between non-cancerous and cancerous mammary cells in dogs. This study will pave the path for further in vitro work of connexins in comparative canine models and possibly allow for novel therapeutics to be developed.
Highlights
Mammary cancer is the most common type of neoplasia in female dogs and accounted for70% of all cancer cases in Genoa, Italy in 1985–2002 [1]
Three independent experiments of triplicate western blot measurements revealed a significant decrease of Cx26, Cx32, and Cx45 in CMT12, and Cx36 and Cx43 in both CMT12 and CMT27 (Figure 2)
The assay showed that Lucifer yellow passes through three adjacent CMEC cells bidirectionally from the scrape, whereas CMT12 and CMT27 cells passed dye through a single cell and CF41.Mg passed dye through two to three cells, in the same time frame (Figure 3). These results suggest that cancerous cells, CMT12 and CMT27, have relatively lower gap junction capacity than CMEC non-cancerous cells
Summary
Mammary cancer is the most common type of neoplasia in female dogs and accounted for70% of all cancer cases in Genoa, Italy in 1985–2002 [1]. Mammary cancer is the most common type of neoplasia in female dogs and accounted for. The incidence of canine mammary tumors varies throughout the world depending on the commonality of spaying. Gap junctions are composed of two hemichannels, known as connexons—one from each cell; each connexon is composed of a ring of six connexin (Cx) proteins that surround a hydrophilic pore. This structure allows a variety of molecules such as cAMP and other second messengers and inorganic molecules, like K+ and Ca2+ , to pass between cells [6]
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