Effects of tamoxifen on telomerase activity in breast carcinoma cell lines.

BACKGROUND: The authors tested the effects of the antiestrogenic agent tamoxifen on telomerase activity and cell proliferation in MCF-7 and MDA-MB-231 breast carcinoma cell lines. MCF-7 cells belong to a known estrogen receptor positive cell line, whereas MDA-MB-231 cells, previously thought to be estrogen receptor negative, are now shown to contain estrogen receptor-beta. METHODS: Both cell lines were grown in the presence of tamoxifen 10(-6), 10(-7), 10(-8), and 10(-9) M for 10 days. Cells in separate flasks were harvested daily for determination of total cell number, protein was extracted for determination of telomerase activity, and RNA was extracted for reverse transcriptase-polymerase chain reaction analysis to measure expression levels of the telomerase components (the RNA component and the catalytic subunit) and estrogen receptors. RESULTS: Total cell counts and telomerase activity levels of both cell lines with 10(-8) M tamoxifen treatment were lower than control cells and other tamoxifen treatments. Changes in the expression of individual telomerase components correlated with telomerase activity. Estrogen receptor status did not correlate with telomerase activity. CONCLUSIONS: Tamoxifen strongly affected both cell count and telomerase activity within the 10(-8) M concentration of both cell lines. Cells were able to overcome drug inhibition at all other doses after 4 days. Telomerase activity and cell proliferation were correlated in both cell lines and depended on drug concentration. Tamoxifen showed long term effects on cell proliferation of the MCF-7 cells.

Telomerase activity in solid transitional cell carcinoma, bladder washings, and voided urine.

Telomerase activity has been detected in a wide variety of human malignancies. It appears to be one of the fundamental ingredients necessary for cellular immortality. We sought to determine the incidence of telomerase activity in solid transitional cell carcinoma (TCC) specimens, benign urothelium, bladder washings, and voided urine from patients with TCC identified cystoscopically compared with controls. Telomerase activity was measured in 26 solid bladder cancers and 13 benign urothelial specimens using the telomere repeat amplification protocol (TRAP), a polymerase chain reaction (PCR) based assay. Telomerase activity was further measured in the centrifuged cellular material obtained from the bladder washings of 26 patients with TCC and 40 with benign urologic disease found to have a normal cystoscopy. All patients with hematuria were additionally evaluated with an upper tract radiographic examination and found to be free of malignancy. Voided urine was likewise evaluated in 11 patients with TCC, 12 with benign urologic diseases, and 56 asymptomatic control subjects. Telomerase activity was detected in 25 of 26 (96%) solid specimens, 21 of 26 (81%) bladder washings, and 6 of 11 (54%) voided urine specimens from patients with histologically confirmed TCC. In the control group, 2 of 13 (15%) benign urothelial specimens and 2 of 56 (4%) voided urine specimens from the asymptomatic volunteer group demonstrated telomerase activity. Of those with benign urologic disease, 16 of 40 (40%) bladder barbotage specimens and 6 of 12 (50%) voided urine specimens demonstrated telomerase activity. Sensitivity and specificity of telomerase as a marker for TCC were 81% and 60%, respectively, in the bladder washings group and 54% and 50%, respectively, in voided urine. These data indicate that activation of telomerase is frequent in solid TCC and appears to be a sensitive marker in bladder washings of patients with TCC. We noted an unexpectedly high false positive detection rate in patients with benign urologic diseases, especially those with symptomatic benign prostatic hyperplasia. An additional study of a larger number of both bladder cancer patients and those at risk is necessary to determine if telomerase activity could play a role as a diagnostic and/or surveillance marker of TCC. Published by Elsevier Science Inc.