Clinical implications of antitelomeric drugs with respect to the nontelomeric functions of telomerase in cancer

Telomerase: A prominent oncological target for development of chemotherapeutic agents

Telomerase is a ribonucleoprotein (RNP) responsible for the maintenance of chromosomal integrity by stabilizing telomere length. Telomerase is a widely expressed hallmark responsible for replicative immortality in 80-90% of malignant tumors. Cancer cells produce telomerase which prevents telomere shortening by adding telomeres sequences beyond Hayflick's limit; which enables them to divide uncontrollably. The activity of telomerase is relatively low in somatic cells and absent in normal cells, but the re-activation of this RNP in normal cells suppresses p53 activity which leads to the avoidance of senescence causing malignancy. Here, we have focused explicitly on various anti-telomerase therapies and telomerase-inhibiting molecules for the treatment of cancer. We have covered molecules that are reported in developmental, preclinical, and clinical trial stages as potent telomerase inhibitors. Apart from chemotherapy, we have also included details of immunotherapy, gene therapy, G-quadruplex stabilizers, and HSP-90 inhibitors. The purpose of this work is to discuss the challenges behind the development of novel telomerase inhibitors and to identify various perspectives for designing anti-telomerase compounds.

[Clinical Application and Challenges of Telomere and Telomerase Research in Lung Cancer]

肺癌是世界范围内发病率和死亡率较高的恶性肿瘤之一。端粒和端粒酶与肺癌的发生发展密切相关。虽然端粒酶可能不是导致细胞癌变的直接原因，但在维持端粒长度和肿瘤生长方面起到关键作用。包括肺癌在内的大部分肿瘤端粒长度缩短。端粒长度的变化与肺癌发生风险相关，并可能成为肺癌的治疗靶标和预测指标。针对端粒和端粒酶信号通路的靶向治疗药物正在探索中，以端粒酶抑制剂为代表的小分子药物有希望应用于肺癌的临床治疗中。但是，人们对于端粒和端粒酶的研究还远远不够，端粒长度维持的旁路作用机制可能是下一步需要深入研究的方向。

Development and Clinical Prospects of Techniques to Separate Circulating Tumor Cells from Peripheral Blood

Detection of circulating tumor cells (CTC) is an important liquid biopsy technique that has advanced considerably in recent years. To further advance the development of technology for curing cancer, several CTC technologies have been proposed by various research groups. Despite their potential role in early cancer diagnosis and prognosis, CTC methods are currently used for research purposes only, and very few methods have been accepted for clinical applications because of difficulties, including CTC heterogeneity, CTC separation from the blood, and a lack of thorough clinical validation. Although current CTC technologies have not been truly implemented, they possess high potential as future clinical diagnostic techniques for individualized cancer. Here, we review current developments in CTC separation technology. We also explore new CTC detection methods based on telomerase and nanomaterials, such as in vivo flow cytometry. In addition, we discuss the difficulties that must be overcome before CTC can be applied in clinical settings.

Chimeric bifunctional oligonucleotides as a novel tool to invade telomerase assembly

Telomerase is a key participant in the telomere length maintaining system in eukaryotic cells. Telomerase RNA and protein reverse transcriptase subunits are essential for the appearance of active telomerase in vitro. Telomerase is active in many cancer types and is a potential target for anticancer drug development. Here we report a new approach for impairing telomerase function at the stage of human telomerase assembly. The approach is based on the application of chimeric bifunctional oligonucleotides that contain two oligonucleotide parts complementary to the functional domains of telomerase RNA connected with non-nucleotide linkers in different orientations (5'-3', 5'-5' or 3'-3'). Such chimeras inhibited telomerase in vitro in the nM range, but were effective in vivo in sub-nM concentrations, predominantly due to their effect on telomerase assembly and dimerization.

Extracting extra-telomeric phenotypes from telomerase mouse models

Telomerase reverse transcriptase (TERT) is the protein component of telomerase and combined with an RNA molecule, telomerase RNA component, forms the telomerase enzyme responsible for telomere elongation. Telomerase is essential for maintaining telomere length from replicative attrition and thus contributes to the preservation of genome integrity. Although diverse mouse models have been developed and studied to prove the physiological roles of telomerase as a telomere- elongating enzyme, recent studies have revealed non-canonical TERT activities beyond telomeres. To gain insights into the physiological impact of extra-telomeric roles, this review revisits the strategies and phenotypes of telomerase mouse models in terms of the extra-telomeric functions of telomerase.