Abstract 2116: Therapeutic potential of T-Oligo and role of tankyrase in its mechanism of action.

Abstract When telomeres are disrupted, exposure of the single stranded 3’ overhang triggers DNA damage pathways resulting in cell senescence and apoptosis. T-oligo, an oligonucleotide homologous to the 3’ overhang, mimics telomere exposure inducing p53 /p73 associated damage responses in malignant cells with negligible effects on normal tissues. To test the ability of T-oligo as a therapeutic agent, subcutaneous NSCLC tumors were established in nude mice which were given daily intratumoral injections (60 nmoles) of T-oligo or a complementary oligonucleotide for 6 weeks. SW1573 and H358 tumors treated with T-oligo exhibited a 5.6 and 4.3 fold reduction in tumor size respectively. Examination of tumor sections for senescence using β-galactosidase revealed that both H358 and SW1573 exhibited strong staining for senescence compared to controls. Staining for angiogenesis and vasculogenesis in H358 and SW1573 displayed 2.2 fold and 3 fold reduction, respectively. These results indicate that T-oligo not only reduced tumor size and vessel density, but also induced senescence suggesting that T-oligo, may be a molecularly targeted cancer therapy. To test the efficacy of T-oligo after IV delivery subcutaneous melanoma tumors were treated with IV T-oligo (78 nmoles) for 4 weeks which resulted in a 3.7 fold reduction in T-oligo treated tumor volume. These tumors are further being evaluated for angiogenesis and vasculogenesis. The role of poly (ADP-ribose) polymerase, tankyrase-1, in T-oligo mediated DNA damage responses was assessed using XAV939, a tankyrase inhibitor. Tankyrase-1 parsylates TRF1, releasing it from the telomere, allowing telomerase to access telomeric DNA thereby increasing telomere length. TRF1, a protein associated with the protective telomere T-loop structure, negatively controls telomere length. Since TRF1 plays a role in the stability of the shelterin complex (a specialized set of proteins responsible for maintaining the DNA T-loop structure), immunoblots were made for AN (melanoma) and H358 (lung cancer) cell lines and probed for TRF1. Preliminary results indicate 1.7 fold downregulation of TRF1 upon treatment with T-oligo and a negligible difference in the presence of a combination of T-oligo and XAV939. T-oligo treatment also induced a 2.6 fold upregulation of TRF-2 and treatment with T-oligo and XAV939 reduced this upregulation to 1 fold suggesting that T-oligo may only stabilizes part of the free shelterin complex and the rest is degraded by the cell. These results suggest that tankyrase-1 maybe involved in T-oligo mediated signaling and maybe associated with the shelterin complex upon parsylation of TRF1. Citation Format: Terrianne Erickson, Audra N. Iness, Neelu Puri. Therapeutic potential of T-Oligo and role of tankyrase in its mechanism of action. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2116. doi:10.1158/1538-7445.AM2013-2116