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Telomerase activity and bcl2 expression in human breast cancer


Telomerase is a ribonucleoprotein that synthesizes telomers and plays an important role in cellular immortalization. Bcl2 gene encodes for a mitochondrial protein that is 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 reduced immunohisto-chemical expression of bcl2.

Materials and method

Bcl2 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 bcl2 was determined by a breast pathologist who was blinded to telomerase data. Fisher's exact test was used to examine the association between telomerase activity and bcl2 expression.


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%) out of 17 telomerase-positive tumours expressed strong or moderate bcl2 staining in more than 50% of tumour cells, compared with six (75%) out of eight telomerase-negative tumours (P = 1.0).


Telomerase reactivation appears to be independent of bcl2 protein expression in human breast cancer.

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Elkak, A., Kirkpatrick, K., Mears, L. et al. Telomerase activity and bcl2 expression in human breast cancer. Breast Cancer Res 3 (Suppl 1), A24 (2001).

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