Telomerase mRNA Expression by In Situ Hybridization in Premalignant Lesions and Carcinomas of the Breast

ABSTRACT

BACKGROUND: Telomerase is a ribonucleoprotein, DNA polymerase that synthesizes telomere repeats onto chromosomal ends and maintains telomere length. Telomerase activity has been detected in a broad range of human malignant neoplasms, but not in normal somatic cells. So, activation of telomerase may represent an essential step in the malignant transformation of cells. However, the expression of telomerase in premalignant lesions remains relatively unexplored. This study was conducted to investigate the reactivation of telomerase in the carcinogenesis of human breast tissue. METHODS: In situ hybridization for the telomerase RNA component (human telomerase mRNA; hTR) was used in a normal breast tissue (n=41), florid ductal hyperplasia (FDH) (n=10), atypical ductal hyperplasia (ADH) (n=3), ductal carcinoma in situ (DCIS) (n=44) and invasive carcinoma (n=33). hTR expression in relation to p53 status and the pathologic parameters in breast cancer was also studied. RESULTS: Expression of hTR was demonstrated in 13 samples (31.7%) of normal breast tissues, 4 (40%) of FDH, 3 (100%) of ADH, 42 (95.5%) of DCIS, and 33 (100%) of invasive carcinoma. The rate of hTR expression of ADH was significantly different from that of FDH (p<0.05), and there were no differences in hTR expression rates among ADH, DCIS and invasive carcinomas. There was no correlation between hTR expression and nuclear grade, tumor size, and p53 status in invasive carcinomas. CONCLUSION: These results suggest that telomerase activation may be an early event and an essential step in the carcinogenesis of human breast tissue, and that telomerase has no correlations with p53 status and prognostic parameters.