Suppression of telomerase activity as an indicator of drug-induced cytotoxicity against cancer cells: In vitro studies with fresh human tumor samples

Telomerase is a ribonucleoprotein complex with reverse-transcriptase activi ty responsible for telomere reconstitution. High telomerase activity was fo und in cancer cells, but not in differentiated homologous nonmalignant tiss ues. We demonstrated previously that the disappearance of telomerase activi ty is a reliable marker of tumor cell killing in human cancer cell lines. W e have investigated the possibility of evaluating chemosensitivity of neopl astic cells of different origin [ovary, lung, breast, gastrointestinal, ski n (melanoma)] obtained from cancer patients. by measuring residual telomera se activity after drug treatment in vitro. Using the classical telomeric re peal amplification protocol ("TRAP") assay based on polymerase chain reacti on, we examined telomerase activity of untreated or drug-treated tumor cell suspensions, derived from the processing of surgical specimens. Feasibilit y and reproducibility of the assay were evaluated according to various para meters, including drug concentration, time of in vitro culture, and type of tumor. The results indicated that the assay is highly sensitive and reprod ucible, and can be performed using surgical specimens in a reasonable perce ntage of cases, ranging from 40% (breast cancer) to 100% (ovarian cancer). Moreover, the assay provides comparable results using a wide range of tumor cells, and the presence of normal cells does not interfere with the result s. Prolonged tumor cell culture is not required because the assay can be co mpleted within 24 to 72 hours after sample collection. In conclusion, the p resent investigation provides the technical bases for future studies to eva luate whether this assay would be able to predict patient's response to ant itumor agents.