Of humans and canines: A comparative evaluation of heat shock and apoptosis-associated proteins in mammary tumors

Abstract

Background Mammary tumors are the most common neoplasms in humans and canines. Human and canine mammary tumors share several important epidemiological, clinicopathological and biochemical features. Dysregulation of normal programmed cell death mechanisms play an important role in the pathogenesis and progression of breast cancer. We investigated the expression of heat shock proteins (Hsps) as well as apoptosis-associated proteins in both human and canine mammary tumors. Methods Twenty breast cancer patients who were categorized as pre- and postmenopausal and 20 mammary gland tumors obtained from dogs were included in this study The expression of Bcl-2, Bcl-X L, Bax, caspases 8 and 3 as well as Hsp 70 and 90 in tumor tissues and adjacent tissues were investigated using Western blotting. Results While expression of Bcl-2, Bcl-X L, Hsp 70 and 90 was increased, expression of Bax and caspases 8 and 3 was significantly lower in both human as well as canine mammary tumor tissues compared to corresponding adjacent tissues. The magnitude of the changes was however more pronounced in premenopausal patients compared to postmenopausal patients. Conclusions The shift of balance towards expression of Hsp and antiapoptotic proteins may lead to evasion of apoptosis both in humans and canines. The similar pattern of changes in Hsps and apoptosis-associated proteins in human and canine mammary tumors validate use of the canine model to understand the molecular mechanisms of mammary carcinogenesis.