Cytological detection of telomerase activity using an in situ telomeric repeat amplification protocol assay.

A previously reported highly sensitive assay for measuring telomerase activity on cell and tissue extracts indicates that most human tumor tissues, but not cells adjacent to tumors, have detectable telomerase activity. Although this assay has provided a significant amount of information about the presence or absence of telomerase activity, it does not indicate whether all cells within a tumor have telomerase activity or whether only a subset does. The present report demonstrates the ability to advance this technology to an in situ assay. Using fluorescent telomerase primers and in situ PCR, we show that telomerase activity can be detected at the cellular level. This study demonstrates that telomerase activity is not detected in normal cells but is detected in tumor cells of clinical specimens and in tumor-derived cell lines.