Telomerase activity and Bcl-2 expression in human breast cancer

Aims: Telomerase is a ribonucleoprotein that synthesizes telomeres and plays an important role in cellular immortalization. Bcl-2 gene encodes for a mitochondrial protein thought to prevent apoptosis of normal cells. We previously reported telomerase activity in 74% of human invasive breast cancers and detected a significant association between telomerase activity and prognostic parameters such as nodal status, tumour size and cellular proliferation. We hypothesized that telomerase reactivation in human breast cancer was associated with increased immunohistochemical expression of Bcl-2. Methods: Bcl-2 immunohistochemical expression was determined in 25 infiltrating breast carcinomas with known telomerase activity (17 telomerase-positive and 8 telomerase-negative). The percentage of strongly and moderately stained tumour cells for Bcl-2 was determined by a breast pathologist who was blinded to telomerase data. Fisherʹs exact test was used to examine the association between telomerase activity and Bcl-2 expression. Results: The median percentage of strongly stained tumour cells was 50% for telomerase-positive tumours (range, 0–100%) and 45% for telomerase-negative tumours (range, 0–100%). Twelve (70%) of 17 telomerase-positive tumours expressed strong or moderate Bcl-2 staining in >50% of tumour cells compared with six (75%) of eight telomerase-negative tumours (P=1.0). Conclusion: Telomerase reactivation seems to be independent of Bcl-2 protein expression in human breast cancer.