Novel delivery system for T-oligo using a nanocomplex formed with an alpha helical peptide for melanoma therapy

Functional Nanoparticles for Enhanced Cancer Therapy

Cancer is the leading cause of death in people worldwide. The conventional therapeutic approach is mainly based on chemotherapy, which has a series of side effects. Compared with traditional chemotherapy drugs, nanoparticle-based delivery of anti-cancer drugs possesses a few attractive features. The application of nanotechnology in an interdisciplinary manner in the biomedical field has led to functional nanoparticles achieving much progress in cancer therapy. Nanoparticles have been involved in the diagnosis and targeted and personalized treatment of cancer. For example, different nano-drug strategies, including endogenous and exogenous stimuli-responsive, surface conjugation, and macromolecular encapsulation for nano-drug systems, have successfully prevented tumor procession. The future for functional nanoparticles is bright and promising due to the fast development of nanotechnology. However, there are still some challenges and limitations that need to be considered. Based on the above contents, the present article analyzes the progress in developing functional nanoparticles in cancer therapy. Research gaps and promising strategies for the clinical application are discussed.

Effect of therapies-mediated modulation of telomere and/or telomerase on cancer cells radiosensitivity

Cancer is one of the leading causes of death in the world. Many strategies of cancer treatment such as radiotherapy which plays a key role in cancer treatment are developed and used nowadays. However, the side effects post-cancer radiotherapy and cancer radioresistance are two major causes of the limitation of cancer radiotherapy effectiveness in the cancer patients. Moreover, reduction of the limitation of cancer radiotherapy effectiveness by reducing the side effects post-cancer radiotherapy and cancer radioresistance is the aim of several radiotherapy-oncologic teams. Otherwise, Telomere and telomerase are two cells components which play an important role in cancer initiation, cancer progression and cancer therapy resistance such as radiotherapy resistance. For resolving the problems of the limitation of cancer radiotherapy effectiveness especially the cancer radio-resistance problems, the radio-gene-therapy strategy which is the use of gene-therapy via modulation of gene expression combined with radiotherapy was developed and used as a new strategy to treat the patients with cancer. In this review, we summarized the information concerning the implication of telomere and telomerase modulation in cancer radiosensitivity.

Oligonucleotides Targeting Telomeres and Telomerase in Cancer

Telomeres and telomerase have become attractive targets for the development of anticancer therapeutics due to their involvement in cancer cell immortality. Currently, several therapeutics have been developed that directly target telomerase and telomeres, such as telomerase inhibitors and G-quadruplex stabilizing ligands. Telomere-specific oligonucleotides that reduce telomerase activity and disrupt telomere architecture are also in development as novel anticancer therapeutics. Specifically, GRN163L and T-oligos have demonstrated promising anticancer activity in multiple cancers types via induction of potent DNA damage responses. Currently, several miRNAs have been implicated in the regulation of telomerase activity and may prove to be valuable targets in the development of novel therapies by reducing expression of telomerase subunits. Targeting miRNAs that are known to increase expression of telomerase subunits may be another strategy to reduce carcinogenesis. This review aims to provide a comprehensive understanding of current oligonucleotide-based anticancer therapies that target telomeres and telomerase. These studies may help design novel therapeutic approaches to overcome the challenges of oligonucleotide therapy in a clinical setting.

Treating Cancer by Targeting Telomeres and Telomerase

Telomerase is expressed in more than 85% of cancer cells. Tumor cells with metastatic potential may have a high telomerase activity, allowing cells to escape from the inhibition of cell proliferation due to shortened telomeres. Human telomerase primarily consists of two main components: hTERT, a catalytic subunit, and hTR, an RNA template whose sequence is complimentary to the telomeric 5′-dTTAGGG-3′ repeat. In humans, telomerase activity is typically restricted to renewing tissues, such as germ cells and stem cells, and is generally absent in normal cells. While hTR is constitutively expressed in most tissue types, hTERT expression levels are low enough that telomere length cannot be maintained, which sets a proliferative lifespan on normal cells. However, in the majority of cancers, telomerase maintains stable telomere length, thereby conferring cell immortality. Levels of hTERT mRNA are directly related to telomerase activity, thereby making it a more suitable therapeutic target than hTR. Recent data suggests that stabilization of telomeric G-quadruplexes may act to indirectly inhibit telomerase action by blocking hTR binding. Telomeric DNA has the propensity to spontaneously form intramolecular G-quadruplexes, four-stranded DNA secondary structures that are stabilized by the stacking of guanine residues in a planar arrangement. The functional roles of telomeric G-quadruplexes are not completely understood, but recent evidence suggests that they can stall the replication fork during DNA synthesis and inhibit telomere replication by preventing telomerase and related proteins from binding to the telomere. Long-term treatment with G-quadruplex stabilizers induces a gradual reduction in the length of the G-rich 3’ end of the telomere without a reduction of the total telomere length, suggesting that telomerase activity is inhibited. However, inhibition of telomerase, either directly or indirectly, has shown only moderate success in cancer patients. Another promising approach of targeting the telomere is the use of guanine-rich oligonucleotides (GROs) homologous to the 3’ telomere overhang sequence (T-oligos). T-oligos, particularly a specific 11-base oligonucleotide (5’-dGTTAGGGTTAG-3’) called T11, have been shown to induce DNA damage responses (DDRs) such as senescence, apoptosis, and cell cycle arrest in numerous cancer cell types with minimal or no cytostatic effects in normal, non-transformed cells. As a result, T-oligos and other GROs are being investigated as prospective anticancer therapeutics. Interestingly, the DDRs induced by T-oligos in cancer cells are similar to the effects seen after progressive telomere degradation in normal cells. The loss of telomeres is an important tumor suppressor mechanism that is commonly absent in transformed malignant cells, and hence, T-oligos have garnered significant interest as a novel strategy to combat cancer. However, little is known about their mechanism of action. In this review, we discuss the current understanding of how T-oligos exert their antiproliferative effects in cancer cells and their role in inhibition of telomerase. We also discuss the current understanding of telomerase in cancer and various therapeutic targets related to the telomeres and telomerase.

A balancing act: orchestrating amino-truncated and full-length p73 variants as decisive factors in cancer progression

p73 is the older sibling of p53 and mimics most of its tumor-suppressor functions. Through alternative promoter usage and splicing, the TP73 gene generates more than two dozen isoforms of which N-terminal truncated DNp73 variants have a decisive role in cancer pathogenesis as they outweigh the positive effects of full-length TAp73 and p53 in acting as a barrier to tumor development. Beyond the prevailing view that DNp73 predominantly counteract cell cycle arrest and apoptosis, latest progress indicates that these isoforms acquire novel functions in epithelial-to-mesenchymal transition, metastasis and therapy resistance. New insight into the mechanisms underlying this behavior reinforced the expectation that DNp73 variants contribute to aggressive cellular traits through both loss of wild-type tumor-suppressor activity and gain-of-function, suggesting an equally important role in cancer progression as mutant p53. In this review, we describe the novel properties of DNp73 in the invasion metastasis cascade and outline the comprehensive p73 regulatome with an emphasis on molecular processes putting TAp73 out of action in advanced tumors. These intriguing insights provoke a new understanding of the acquisition of aggressive traits by cancer cells and may help to set novel therapies for a broad range of metastatic tumors.

T-oligo as an anticancer agent in colorectal cancer

In the United States, there will be an estimated 96,830 new cases of colorectal cancer (CRC) and 50,310 deaths in 2014. CRC is often detected at late stages of the disease, at which point there is no effective chemotherapy. Thus, there is an urgent need for effective novel therapies that have minimal effects on normal cells. T-oligo, an oligonucleotide homologous to the 3'-telomere overhang, induces potent DNA damage responses in multiple malignant cell types, however, its efficacy in CRC has not been studied. This is the first investigation demonstrating T-oligo-induced anticancer effects in two CRC cell lines, HT-29 and LoVo, which are highly resistant to conventional chemotherapies. In this investigation, we show that T-oligo may mediate its DNA damage responses through the p53/p73 pathway, thereby inhibiting cellular proliferation and inducing apoptosis or senescence. Additionally, upregulation of downstream DNA damage response proteins, including E2F1, p53 or p73, was observed. In LoVo cells, T-oligo induced senescence, decreased clonogenicity, and increased expression of senescence associated proteins p21, p27, and p53. In addition, downregulation of POT1 and TRF2, two components of the shelterin protein complex which protects telomeric ends, was observed. Moreover, we studied the antiproliferative effects of T-oligo in combination with an EGFR tyrosine kinase inhibitor, Gefitinib, which resulted in an additive inhibitory effect on cellular proliferation. Collectively, these data provide evidence that T-oligo alone, or in combination with other molecularly targeted therapies, has potential as an anti-cancer agent in CRC.