Telomerase plays an important role in cell proliferation and carcinogenesis and 
is believed to be a good target for anti-cancer drugs. Elimination of template 
function of telomerase RNA may repress the telomerase activity. A hammer-headed 
ribozyme (telomerase ribozyme, teloRZ) directed against the RNA component of 
human telomerase (hTR) was designed and synthesized. TeloRZ showed a specific 
cleavage activity against the hTR. The cleavage efficacy reached 60%. A 
eukaryotic expression plasmid containing teloRZ gene was inducted into HeLa 
cells by lipofectamine, the telomerase activity in HeLa cells expressing teloRZ 
decreased to one eighth of that in the control cells. The doubling time 
increased significantly and the apoptosis ratio was elevated with increasing 
population doublings (PDS). After 19-20 PDS 95% cells were apoptotic. To further 
investigate the effect of teloRZ on tumor growth, the eukaryotic expression 
plasmid containing teloRZ was injected into transplanted tumor of nude mouse. 
The teloRZ effectively inhibited the telomerase activity in transplanted tumor, 
promoted apoptosis of the transplanted tumor cells, and decreased the tumor size 
significantly. These results indicate that teloRZ can effectively inhibit 
telomerase activity and growth of tumor cells, and suggest the potential use of 
this ribozyme in anti-cancer therapy.