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Much of the work carried out by DTT is in support of the National Toxicology Program (NTP), an interagency partnership of the Food and Drug Administration, National Institute for Occupational Safety and Health, and NIEHS.

Molecular Pathogenesis Group

Much of the in vitro research of the biology of human uterine leiomyomas has resulted from the use of explants or primary monolayer cultures established from tissue samples taken after hysterectomy or myomectomy. However, in vitro research using human derived uterine leiomyoma cells can be challenging because these cells tend to grow poorly and senesce quickly in culture compared to uterine myometrial cells.

To overcome the challenges of working with explants or primary monolayer cultures of human leiomyoma cells, immortalized human leiomyoma and myometrial cell lines were created by infecting leiomyoma and myometrial cells with a retroviral vector containing hTERT, the gene for the catalytic subunit of telomerase. Without telomerase, cells lose DNA from the telomeres of the chromosomes with each replication until the telomere shortens to a critical length and the cells senesce.

Telomerase is a ribonucleoprotein reverse transcriptase that stabilizes the telomere and chromosome structure by adding telomeric repeats that are lost during replication. The telomerase enzyme consists of three major components, hTR (human telomerase RNA), hTLP1 (human telomerase associated protein), and hTERT or hTRT (also hEST2; human telomerase reverse transcriptase). Most normal and neoplastic cells express hTR and hTLP1. Malignant cells also express high levels of hTERT, which seems to be sufficient for the cells to regain telomerase activity. On the other hand, most normal cells and benign neoplastic cells, including leiomyoma, do not possess telomerase activity, although some express the hTERT gene at varying levels.

Other successful inductions of telomerase activity in human somatic cells via introduction ofhTERT have not led to phenotypic changes typical of malignant cells.