Evaluation of Bcl-2, Bcl-XL and Bax Expression and Apoptotic Index in Canine Mammary Tumours

Mammary tumours are the most common neoplasms in intact female dogs. Dysregulation of programmed cell death mechanisms plays an important role in the pathogenesis and progression of mammary gland tumours. The aim of this study was to investigate the relationship between some anti-apoptotic proteins (Bcl-2, Bcl-X-L and Bax), apoptotic index (AI) and histopathological diagnosis, tumour grading, tumour staging and survival time of canine mammary tumours (CMT). Twenty seven tissue samples were collected from twenty seven animals with mammary tumours. The samples were evaluated and graded histopathologically. All cases were staged according to the TNM system. The expression of Bcl-2, Bcl-X-L and Bax proteins was investigated using indirect immunoperoxidase test and apoptosis was evaluated using terminal deoxynucleotidyltransferase (TdT)-mediated nick end-labelling (TUNEL) technique. Follow-up examination and survival estimation analysis were performed. While there was a significant statistical relation between Bcl-2 expression and histopathological diagnosis (P<0.005), there was no considerable association between histopathological diagnosis and Bax, Bcl-X-L and AI (P>0.05). The differences between T1 and T5, T2 and T5 stages were statistically significant in terms of Bax expression (P<0.05), and Bax expressions were higher in T5 when compared with T1 or T2. No association between survival time and Bcl-2, Bax, Bcl-X-L and AI was determined (P>0.05). Bcl-2 was overexpressed in highly malignant tumours such as solid and tubulopapillary adenocarcinomas and Bax had high expression levels in metastatic tumours. As a result, it is concluded that Bcl-2 and Bax expression can be accessory parameters for anticipating the biologic behaviour and prognosis of CMT but these markers alone are not sufficient for the determination of survival time.