Telomerase enzyme activity and RNA expression in Adriamycin-resistant human breast carcinoma MCF-7 cells

Telomerase activity has been reported in cancer cells after treatment with antineoplastic agents. Assessment of telomerase activity could be a valuabl e tool to measure the reduction of aggression caused by chemotherapy, This study was designed to investigate the significance of telomerase for chemot herapy with respect to Adriamycin (ADM)-resistance. MCF-7 and its ADM-resis tant line (AdrR) were treated with ADM, 5-fluorouracil (5FU) or taxotere (T AXO). Telomerase activity and human telomerase RNA component (hTR) were qua ntitatively measured by the telomeric repeat amplification protocol assay a nd RT-PCR, respectively. Cell counting and MTT assay were also performed. I n MCF-7, enzyme activity was significantly reduced by ADM and 5FU treatment s. In AdrR, 5FU and TAXO reduced enzyme activity, while ADM significantly i ncreased the activity. No significant changes in hTR were seen in these two cell lines after treatment with any of these drugs. When Bcl-2 expression was examined after drug treatments, ADM increased Bcl-2 expression in AdrR cells, while not changing it in MCF-7 cells. We conclude that an unusual re action of telomerase activity in AdrR may explain, at least in part, one of the mechanisms of the malignant biological behavior related with the drug- resistance to ADM. (C) 1999 Elsevier Science Ireland Ltd. All rights reserv ed.