Abstract 2116: Therapeutic potential of T-Oligo and role of tankyrase in its mechanism of action.
Authors: Terrianne Erickson, Audra N. Iness, Neelu Puri
Journal: Cancer Research (2013)

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