Telomerase promoter-driven cancer gene therapy

Human telomerase is highly active in more than 85% of primary cancers, regardless of their tissue origins, but not in most differentiated somatic tissues. Because of this, telomerase recently has become a popular target of anticancer therapy and has been used as a marker of cancer. Similarly, telomerase promoters, especially telomerase reverse transcriptase (TERT) promoter, have been zealously tested for targeted cancer gene therapy. In vitro and in vivo studies have demonstrated that the human TERT (hTERT) promoter is highly active in human and murine cancer cells but not in normal differentiated human cells, normal human CD34(+) progenitor cells, normal mouse fibroblasts, or normal mouse livers. Moreover, transcription factors can dramatically augment transgene expression from the hTERT promoter without the promoter losing its specificity. Thus far, telomerase promoters have been tested for targeted cancer gene therapy with proapoptotic, cytotoxic, and prodrug-activating genes and with replication-competent viral vectors. Here, we review recent achievements in telomerase promoter-based targeted cancer gene therapy.