Geron Inc. is developing telomerase, a reverse transcriptase that increases a cell's proliferative capacity by lengthening the ends of chromosomes (telomeres), to postpone or reverse cell senescence in a variety of disorders. But a finding that telomerase-driven cell proliferation may be associated with the activation of the c-myc oncogene raises questions about use of the technology for therapeutic applications.

Genetica Inc. (Cambridge, Mass.) and University College London researchers last week published in Nature that expression of human TERT (hTERT) in human mammary epithelial cells increased the cells' proliferative capacity. Unfortunately, expression of TERT, the catalytic subunit of telomerase, also activated expression of c-myc, which in turn immortalized cells by activating TERT. High telomerase activity was seen even after exogenous TERT was removed.