Exposure of the telomere overhang acts as a DNA damage signal, and exogenous administration of an 11-base oligonucleotide homologous to the 3′-telomere overhang sequence (T-oligo) mimics the effects of overhang exposure by inducing senescence and cell death in non-small cell lung cancer (NSCLC) cells, but not in normal bronchial epithelial cells. T-oligo-induced decrease in cellular proliferation in NSCLC is likely directed through both p53 and its homolog, p73, with subsequent induction of senescence and expression of senescence-associated proteins, p21, p33ING, and p27Kip1 both in vivo and in vitro. Additionally, T-oligo decreases tumor size and inhibits angiogenesis through decreased VEGF signaling and increased TSP-1 expression.
Oligonucleotides homologous to 3′-telomere overhang (T-oligos) trigger inherent telomere-based DNA damage responses mediated by p53 and/or ATM and induce senescence or apoptosis in various cancerous cells. However, T-oligo has limited stability in vivo due to serum and intracellular nucleases. To develop T-oligo as an innovative, effective therapeutic drug and to understand its mechanism of action, we investigated the antitumor effects of T-oligo or T-oligo complexed with a novel cationic alpha helical peptide, PVBLG-8 (PVBLG), in a p53 null melanoma cell line both in vitro and in vivo. The uptake of T-oligo by MM-AN cells was confirmed by immunofluorescence, and fluorescence-activated cell sorting analysis indicated that the T-oligo-PVBLG nanocomplex increased uptake by 15-fold. In vitro results showed a 3-fold increase in MM-AN cell growth inhibition by the T-oligo-PVBLG nanocomplex compared with T-oligo alone. Treatment of preformed tumors in immunodeficient mice with the T-oligo-PVBLG nanocomplex resulted in a 3-fold reduction in tumor volume compared with T-oligo alone. This reduction in tumor volume was associated with decreased vascular endothelial growth factor expression and induction of thrombospondin-1 expression and apoptosis. Moreover, T-oligo treatment downregulated procaspase-3 and procaspase-7 and increased catalytic activity of caspase-3 by 4-fold in MM-AN cells. Furthermore, T-oligo induced a 10-fold increase of senescence and upregulated the melanoma tumor-associated antigens MART-1, tyrosinase, and thrombospondin-1 in MM-AN cells, which are currently being targeted for melanoma immunotherapy. Interestingly, siRNA-mediated knockdown of p73 (4–10-fold) abolished this upregulation of tumor-associated antigens. In summary, we suggest a key role of p73 in mediating the anticancer effects of T-oligo and introduce a novel nanoparticle, the T-oligo-PVBLG nanocomplex, as an effective anticancer therapeutic.
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
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.