A HEXAMERIC PHOSPHOROTHIOATE OLIGONUCLEOTIDE TELOMERASE INHIBITOR ARRESTS GROWTH OF BURKITTS-LYMPHOMA CELLS IN-VITRO AND IN-VIVO

A phosphorothioate oligonucleotide (PS-ODN) with sequence identical to the repeat sequence of the mammalian telomere, 5'-d(TTAGGG)-3', was i ncubated with a Burkitt's lymphoma-derived (OMA-BL1) cell line. This h exanucleotide inhibits telomerase activity in cell lysates, lengthens cell doubling time, and induces apoptosis. Concatenated repeats (12-, 18-, and 24-mers) of the 5'-d(TTAGGG)-3' motif induce similar cellular responses. Scrambled sequences do not efficiently inhibit telomerase activity or significantly alter cell growth and viability. The in vivo efficacy of this PS-ODN was evaluated in a xenograft human-nude mouse model. Once tumors were established these animals were administered t he telomere mimic, 5'-d(TTAGGG)-3', a control scrambled sequence 5'-d( TGTGAG)-3', or saline for 14 days via a subcutaneous osmotic pumps in a blinded study monitoring tumor size with dose and time. A significan t decrease in tumor size was observed in animals given 50 mu g/mouse/d ay 5'-d(TTAGGG)-3', but not following 5'-d(TGTGAG)-3', relative to the saline-treated animals. The antitumor activity of the B-mer telomere mimic demonstrated a dose dependency including a reduction in metastat ic nodules in the spleen. No activity was observed with the scrambled controls. In addition to antitumor activity we observed an increase in the mouse hematopoietic progenitor cell populations, BFU-e and CFU-GM . These results demonstrated the effects of a short hexameric oligonuc leotide telomere mimic in vitro and in vivo and the potential utility of short oligonucleotides as telomerase inhibitors. (C) 1997 Academic Press.