Targeted therapy of human malignant glioma in a mouse model by 2-5A antisense directed against telomerase RNA

Telomerase is the RNA-protein complex which elongates telomeric DNA (TTAGGG)(n) and appears to play an important role in cellular immortalization. The almost exclusive expression of telomerase in tumor cells, and not in most normal cells, offers an exciting opportunity for therapy by inhibiting its function. Here, we have investigated the effect of inhibition of telomerase on the growth and survival of human malignant glioma cells in vitro and in vivo by using a 19-mer antisense oligonucleotide against human telomerase RNA linked to a 2',5'-oligoadenylate (2-5A). 2-5A antisense functions by activating the endoribonuclease, RNase L, resulting in the degradation of single stranded, targeted RNA. We have shown that the 2-5A antisense treatment effectively suppressed tumor cell growth and survival in vitro. Furthermore, treatment of tumors grown in nude mice with the antisense oligonucleotide inhibited survival of the tumor cells. TUNEL assays suggest that this effect is mediated through the induction of apoptosis. Targeting telomerase RNA with 2-5A antisense, therefore, may represent an effective and novel approach for treatment of a broad range of cancers.