Telomerase activity is sufficient to allow transformed cells to escape from crisis

Tanya L. Halvorsen, Gil Leibowitz, Fred Levine*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

148 Scopus citations


The introduction of simian virus 40 large T antigen (SVLT) into human primary cells enables them to proliferate beyond their normal replicative life span. In most cases, this temporary escape from senescence eventually ends in a second proliferative block known as 'crisis,' during which the cells cease growing or die. Rare immortalization events in which cells escape crisis are frequently correlated with the presence of telomerase activity. We tested the hypothesis that telomerase activation is the critical step in the immortalization process by studying the effects of telomerase activity in two mortal SVLT-Ras(val12)-transformed human pancreatic cell lines, TRM-6 and βlox5. The telomerase catalytic subunit, hTRT, was introduced into late- passage cells via retrovital gene transfer. Telomerase activity was successfully induced in infected cells, as demonstrated by a telomerase repeat amplification protocol assay. In each of nine independent infections, telomerase-positive cells formed rapidly dividing cell lines while control cells entered crisis. Telomere lengths initially increased, but telomeres were then maintained at their new lengths for at least 20 population doublings. These results demonstrate that telomerase activity is sufficient to enable transformed cells to escape crisis and that telomere elongation in these cells occurs in a tightly regulated manner.

Original languageAmerican English
Pages (from-to)1864-1870
Number of pages7
JournalMolecular and Cellular Biology
Issue number3
StatePublished - Mar 1999
Externally publishedYes


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