Transfer of the human telomerase reverse transcriptase (TERT) gene into T lymphocytes results in extension of replicative potential

In most human somatic cells telomeres progressively shorten with each cell division eventually leading to chromosomal instability and cell senescence. The loss of telomere repeats with cell divisions may also limit the replic ative life span of antigen-specific T lymphocytes. Recent studies have show n that the replicative life span of various primary human cells can be prol onged by induced expression of the telomerase reverse transcriptase (hTERT) gene. To test whether introduction of hTERT can extend the life span of pr imary human T lymphocytes, naive CD8(+) T lymphocytes were transfected with retroviral vectors containing the hTERT gene. Transduced T-cell clones exp ressed high levels of telomerase and either maintained or elongated their t elomere lengths upon culture for extended periods of time. Two of the trans duced subclones retained a normal cloning efficiency for more than 170 popu lation doublings (PDs). In contrast, T-cell clones transfected with control vectors exhibited progressive telomere length shortening and stopped proli feration at around 108 PDs. Telomerase-positive T clones had a normal 46,XY karyotype, maintained their cytotoxic properties, and showed very little s taining for the apoptotic marker annexin-V. These results indicate that ect opic hTERT gene expression is capable of extending the replicative life spa n of primary human CD8(+) cytotoxic T lymphocytes.