Strategies targeting telomerase inhibition.

Telomerase plays a pivotal role in cellular immortality and tumorigenesis. Its activity is normally not detectable in most somatic cells while it is reactivated in the vast majority of cancer cells. Therefore, inhibition of telomerase has been viewed as a promising anticancer approach due to its specificity for cancer cells. Studies so far have shown that telomerase inhibition can inhibit the proliferation of cancer cells or cause apoptosis while it has no effect on most normal cells. Strategies currently being applied to induce telomerase inhibition target virtually all of the major components of the ribonucleoprotein holoenzyme and related cell signal pathways that regulate its activity. These strategies include inhibition of telomerase through targeting at the telomerase reverse transcriptase (TERT) catalytic subunit, the telomerase RNA (TR) component, and associated proteins. Other strategies have been developed to target the proteins associated with telomerase at the telomeric ends of chromosomes such as tankyrase. The specific mechanisms that mediate those inhibition effects include small molecules, antisense RNA, and ribozymes. Although the beneficial evidence of telomerase inhibition is obvious, limitations of strategies remain to be resolved to increase the feasibility of clinical application. This analysis will summarize recent developments of strategies in telomerase inhibition.