Telomerase Inhibition Research Articles

A Non-Toxic Concentration of Telomerase Inhibitor BIBR1532 Fails to Reduce TERT Expression in a Feeder-Free Induced Pluripotent Stem Cell Model of Human Motor Neurogenesis.

Several studies have shown that human induced pluripotent stem cell (iPSC)-derivatives are essentially fetal in terms of their maturational status. Inducing ageing in iPSC-motor neuron (MN) models of amyotrophic lateral sclerosis (ALS) has the potential to capture pathology with higher fidelity and consequently improve translational success. We show here that the telomerase inhibitor BIBR1532, hypothesised to recapitulate the telomere attrition hallmark of ageing in iPSC-MNs, was in fact cytotoxic to feeder-free iPSCs when used at doses previously shown to be effective in iPSCs grown on a layer of mouse embryonic fibroblasts. Toxicity in feeder-free cultures was not rescued by co-treatment with Rho Kinase (ROCK) inhibitor (Y-27632). Moreover, the highest concentration of BIBR1532 compatible with continued iPSC culture proved insufficient to induce detectable telomerase inhibition. Our data suggest that direct toxicity by BIBR1532 is the most likely cause of iPSC death observed, and that culture methods may influence enhanced toxicity. Therefore, recapitulation of ageing hallmarks in iPSC-MNs, which might reveal novel and relevant human disease targets in ALS, is not achievable in feeder-free culture through the use of this small molecule telomerase inhibitor.

A novel p53 regulator, C16ORF72/TAPR1, buffers against telomerase inhibition.

Telomere erosion in cells with insufficient levels of the telomerase reverse transcriptase (TERT), contributes to age‐associated tissue dysfunction and senescence, and p53 plays a crucial role in this response. We undertook a genome‐wide CRISPR screen to identify gene deletions that sensitized p53‐positive human cells to telomerase inhibition. We uncovered a previously unannotated gene, C16ORF72, which we term Telomere Attrition and p53 Response 1 (TAPR1), that exhibited a synthetic‐sick relationship with TERT loss. A subsequent genome‐wide CRISPR screen in TAPR1‐disrupted cells reciprocally identified TERT as a sensitizing gene deletion. Cells lacking TAPR1 or TERT possessed elevated p53 levels and transcriptional signatures consistent with p53 upregulation. The elevated p53 response in TERT‐ or TAPR1‐deficient cells was exacerbated by treatment with the MDM2 inhibitor and p53 stabilizer nutlin‐3a and coincided with a further reduction in cell fitness. Importantly, the sensitivity to treatment with nutlin‐3a in TERT‐ or TAPR1‐deficient cells was rescued by loss of p53. These data suggest that TAPR1 buffers against the deleterious consequences of telomere erosion or DNA damage by constraining p53. These findings identify C16ORF72/TAPR1 as new regulator at the nexus of telomere integrity and p53 regulation.

Dual effect of Sapogenins extracted from Spirulina platensis on telomerase activity in two different cell lines

Spirulina platensis is a photosynthetic filamentous, edible cyanobacterium that is known as a superfood. In this study, sapogenins were extracted from the spirulina and the effects of these compounds on telomerase activity were evaluated in MCF7 and HDF cell lines using Telomeric Repeat Amplification Protocol and ELIZA assay. The highest increase in telomerase activity was observed at 0.004 mg/ml of sapogenin by 26% ±20.5 in MCF7 cells, while in HDF cells in the same concentration telomerase activity decreased down to 47%±0.48 and the highest inhibition of telomerase activity was observed at 0.070 mg/ml of sapogenins from Spirulina by 68%±0.43. In conclusion, a compound could play a role as a telomerase activator in one cell line while it could play another role as a telomerase inhibitor in another cell line so introducing compounds as a telomerase inhibitor (anticancer) or as a telomerase activator (anti-aging) should be done with discreet.

A Matter of Life or Death: Productively Infected and Bystander CD4 T Cells in Early HIV Infection.

CD4 T cell death or survival following initial HIV infection is crucial for the development of viral reservoirs and latent infection, making its evaluation critical in devising strategies for HIV cure. Here we infected primary CD4 T cells with a wild-type HIV-1 and investigated the death and survival mechanisms in productively infected and bystander cells during early HIV infection. We found that HIV-infected cells exhibited increased programmed cell death, such as apoptosis, pyroptosis, and ferroptosis, than uninfected cells. However, productively infected (p24+) cells and bystander (p24-) cells displayed different patterns of cell death due to differential expression of pro-/anti-apoptotic proteins and signaling molecules. Cell death was triggered by an aberrant DNA damage response (DDR), as evidenced by increases in γH2AX levels, which inversely correlated with telomere length and telomerase levels during HIV infection. Mechanistically, HIV-infected cells exhibited a gradual shortening of telomeres following infection. Notably, p24+ cells had longer telomeres compared to p24- cells, and telomere length positively correlated with the telomerase, pAKT, and pATM expressions in HIV-infected CD4 T cells. Importantly, blockade of viral entry attenuated the HIV-induced inhibition of telomerase, pAKT, and pATM as well as the associated telomere erosion and cell death. Moreover, ATM inhibition promoted survival of HIV-infected CD4 T cells, especially p24+ cells, and rescued telomerase and AKT activities by inhibiting cell activation, HIV infection, and DDR. These results indicate that productively infected and bystander CD4 T cells employ different mechanisms for their survival and death, suggesting a possible pro-survival, pro-reservoir mechanism during early HIV infection.

Bilateral telomerase-associated impacts of Spirulina platensis extracts: Activation versus inhibition

IntroductionTelomerase is an enzyme responsible for regulating the length of telomeres in eukaryote chromosomes. Activation and inhibition of telomerase results in the extension and shortening of telomeres, respectively. The mentioned phenomena are attributed to anti-aging and anticancer mechanisms. Spirulina platensis extract has attracted a great deal of attention, as an anti-aging factor. MethodsThe regulatory impacts of different extracts of these microalgae on telomerase activity in MCF-7 and HDF cells were investigated using a Telomeric Repeat Amplification Protocol and ELISA, in vitro. ResultsThe methanolic extract of S. platensis increased the telomerase activity by 139% and simultaneously showed high toxicity on the MCF-7 cells (82%) with IC50=0.035 mg/ml. Despite this, the methanolic extract demonstrated an unstable activity of HDF cells. In contrast to the methanolic extract, the aqueous extract of S. platensis toxified the cancer cells at the highest rate of 77% (IC50=0.98 mg/ml); however, it inhibited the telomerase activity of MCF-7 cells up to 52%. Additionally, the aqueous extract acted as an anti-aging factor on the HDF cells through upregulating the telomerase activity by 84% at 0.004 mg/ml. The present research suggests that different extracts of S. platensis behave variously on different cell types. Except the aqueous extract, other extracts of S. platensis are capable of inhibiting MCF-7 cancer cells based on a mechanism different than telomerase inhibition. ConclusionThe aqueous extract of S. platensis seems to be a safe alternative for use as an anti-aging factor as well as an anticancer agent.

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。

The Small Molecule BIBR1532 Exerts Potential Anti-cancer Activities in Preclinical Models of Feline Oral Squamous Cell Carcinoma Through Inhibition of Telomerase Activity and Down-Regulation of TERT.

Expression of telomerase reverse transcriptase (TERT) and telomerase activity (TA) is a main feature of cancer, contributing to cell immortalization by causing telomeres dysfunction. BIBR1532 is a potent telomerase inhibitor that showed potential anti-tumor activities in several types of cancer, by triggering replicative senescence and apoptosis. In a previous work, we detected, for the first time, TERT expression and TA in preclinical models of feline oral squamous cell carcinoma (FOSCC); therefore, we aimed at extending our investigation by testing the effects of treatment with BIBR1532, in order to explore the role of telomerase in this tumor and foreshadow the possibility of it being considered as a future therapeutic target. In the present study, treatment of FOSCC cell lines SCCF1, SCCF2, and SCCF3 with BIBR1532 resulted in successful inhibition of TA, with subsequent cell growth stoppage and decrease in cell viability. Molecular data showed that up-regulation of cell cycle inhibitor p21, unbalancing of Bax/Bcl-2 ratio, and down-regulation of survival gene Survivin were mostly involved in the observed cellular events. Moreover, BIBR1532 diminished the expression of TERT and its transcriptional activator cMyc, resulting in the down-regulation of epidermal growth factor receptor (EGFR), phospho-ERK/ERK ratio, and matrix metalloproteinases (MMPs)-1/-2 and−9, likely as a consequence of an impairment of TERT extra-telomeric functions. Taken together, our data suggest that BIBR1532 exerts multiple anti-cancer activities in FOSCC by inhibiting telomerase pathway and interfering with signaling routes involved in cell proliferation, cell survival, and invasion, paving the way for future translational studies aimed at evaluating its possible employment in the treatment of this severe tumor of cats.

Telomere shortening and DNA damage in culprit cells of different types of progressive fibrosing interstitial lung disease.

Pulmonary fibrosis is strongly associated with telomere shortening and increased DNA damage. Key cells in the pathogenesis involve alveolar type 2 (AT2) cells, club cells and myofibroblasts; however, to what extent these cells are affected by telomere shortening and DNA damage is not yet known. We sought to determine the degree of, and correlation between, telomere shortening and DNA damage in different cell types involved in the pathogenesis of progressive fibrosing interstitial lung disease. Telomere length and DNA damage were quantified, using combined fluorescence in situ hybridisation and immunofluorescence staining techniques, in AT2 cells, club cells and myofibroblasts of controls and patients with pulmonary fibrosis and a telomerase reverse transcriptase mutation (TERT-PF), idiopathic pulmonary fibrosis (IPF) and fibrotic hypersensitivity pneumonitis (fHP). In IPF and TERT-PF lungs, AT2 cells contained shorter telomeres and expressed higher DNA damage signals than club cells and myofibroblasts. In fHP lungs, club cells contained highly elevated levels of DNA damage, while telomeres were not obviously short. In vitro, we found significantly shorter telomeres and higher DNA damage levels only in AT2 surrogate cell lines treated with telomerase inhibitor BIBR1532. Our study demonstrated that in IPF and TERT-PF lungs, telomere shortening and accumulation of DNA damage primarily affects AT2 cells, further supporting the importance of AT2 cells in these diseases, while in fHP the particularly high telomere-independent DNA damage signals in club cells underscores its bronchiolocentric pathogenesis. These findings suggest that cell type-specific telomere shortening and DNA damage may help to discriminate between different drivers of fibrogenesis.

Berberine Inhibits Telomerase Activity and Induces Cell Cycle Arrest and Telomere Erosion in Colorectal Cancer Cell Line, HCT 116.

Colorectal cancer (CRC) is the most common cancer among males and females, which is associated with the increment of telomerase level and activity. Some plant-derived compounds are telomerase inhibitors that have the potential to decrease telomerase activity and/or level in various cancer cell lines. Unfortunately, a deeper understanding of the effects of telomerase inhibitor compound(s) on CRC cells is still lacking. Therefore, in this study, the aspects of telomerase inhibitors on a CRC cell line (HCT 116) were investigated. Screening on HCT 116 at 48 h showed that berberine (10.30 ± 0.89 µg/mL) is the most effective (lowest IC50 value) telomerase inhibitor compared to boldine (37.87 ± 3.12 µg/mL) and silymarin (>200 µg/mL). Further analyses exhibited that berberine treatment caused G0/G1 phase arrest at 48 h due to high cyclin D1 (CCND1) and low cyclin-dependent kinase 4 (CDK4) protein and mRNA levels, simultaneous downregulation of human telomerase reverse transcriptase (TERT) mRNA and human telomerase RNA component (TERC) levels, as well as a decrease in the TERT protein level and telomerase activity. The effect of berberine treatment on the cell cycle was time dependent as it resulted in a delayed cell cycle and doubling time by 2.18-fold. Telomerase activity and level was significantly decreased, and telomere erosion followed suit. In summary, our findings suggested that berberine could decrease telomerase activity and level of HCT 116, which in turn inhibits the proliferative ability of the cells.

Molecular modelling of quinoline derivatives as telomerase inhibitors through 3D-QSAR, molecular dynamics simulation, and molecular docking techniques

Rising mortality due to cancer has led to the development and identification of newer targets and molecules to cure the disease. Telomerase is one of the attractive targets for design of many chemotherapeutic drugs. This research highlights the designing of novel telomerase inhibitors using ligand-based (3D-QSAR) and structure-based (molecular docking and molecular dynamics simulation) approaches. For the development of the 3D-QSAR model, 37 synthetic molecules reported earlier as telomerase inhibitors were selected from diversified literature. Three different alignment methods were explored; among them, distill alignment was found to be the best method with good statistical results and was used for the generation of QSAR model. Statistically significant CoMSIA model with a correlation coefficient (r2ncv) value of 0.974, leave one out (q2) value of 0.662 and predicted correlation coefficient (r2pred) value of 0.560 was used for the analysis of QSAR. For the MDS study, A-chain of telomerase was stabilised for 50 ns with respect to 1-atm pressure, with an average temperature of 299.98 k and with potential energy of 1,145,336 kJ/m converged in 997 steps. Furthermore, the behaviour study of variants towards the target revealed that active variable gave better affinity without affecting amino acid sequences and dimensions of protein which was accomplished through RMSD, RMSF and Rg analysis. Results of molecular docking study supported the outcomes of QSAR contour maps as ligand showed similar interactions with surrounded amino acids which were identified in contour map analysis. The results of the comprehensive study might be proved valuable for the development of potent telomerase inhibitors.

Artemether and imatinib combination therapy against malaria infection

Artemisinin-based combination therapy (ACT) is recommended by the World Health Organization (WHO) as the first and second line of treatment for uncomplicated malaria caused by P. falciparum, as well as for chloroquine-resistant P. vivax malaria. Despite the large number of antimalarial drugs, there is no any ideal drug, since each individual combination of drugs or monotherapy have their own limitations, ranging from their triple (activity) in relation to certain forms of the development of Plasmodium in the human body, side effects, toxicity and resistance. During the course of the study carried out, the most promising compound-candidate was selected – imatinib, which is currently used as targeted therapy for a number of oncological diseases. The objective of this work is to evaluate the efficacy of the combined use of imatinib and artemether in vivo studies on the human malarial model – the rodent malaria parasites Plasmodium berghei. Dut to the optimally selected treatment scheme, it was possible to reduce the dosage of imatinib twice – to 0,25 mg/kg, and that of artemether three times – to 33 mg/kg. The use of this scheme made it possible to considerably reduce the toxic effect of these drugs due to the potentiation of antimalarial effect. Key words: malaria, drug resistance, telomerase inhibitors, imatinib, chemotherapy of malaria

Molecular docking and dynamics simulation study of telomerase inhibitors as potential anti-cancer agents

Normal cells’ genomic identity is protected by telomeres and sometimes chromosomal instability was observed due to shortening of telomerase because of successive cell divisions. Reports indicate that telomerase length is crucial in determining telomerase activity which in turn leads to cancer initiation. It is reported that telomere length regulation has been identified as a plausible strategy for cancer diagnostics and treatment. In the present MS, we explored the telomerase inhibitory activity of catechin analogues and it’s oligomers using computational methods. The structural properties of different ligands discussed in the MS were computed using density functional theory. Conformational effect of different chromene subunit such as 2R, 3R conformations were explored using computational methods. The stereochemical contributions to receptor binding such as intra ligand π-interactions of these ligands were also investigated. We herein propose that these stereochemical aspects of catechins and their oligomers as the most vital factor deciding the effective binding with the N-terminal domain of telomerase which is an efficient strategy in cancer therapy.

Critical Interaction Between Telomerase and Autophagy in Mediating Flow-Induced Human Arteriolar Vasodilation.

Coronary artery disease (CAD) is associated with a compensatory switch in mechanism of flow-mediated dilation (FMD) from nitric oxide (NO) to H2O2. The underlying mechanism responsible for the pathological shift is not well understood, and recent reports directly implicate telomerase and indirectly support a role for autophagy. We hypothesize that autophagy is critical for shear stress-induced release of NO and is a crucial component of for the pathway by which telomerase regulates FMD. Approach and Results: Human left ventricular, atrial, and adipose resistance arterioles were collected for videomicroscopy and immunoblotting. FMD and autophagic flux were measured in arterioles treated with autophagy modulators alone, and in tandem with telomerase-activity modulators. LC3B II/I was higher in left ventricular tissue from patients with CAD compared with non-CAD (2.8±0.2 versus 1.0±0.2-fold change; P<0.05), although p62 was similar between groups. Shear stress increased Lysotracker fluorescence in non-CAD arterioles, with no effect in CAD arterioles. Inhibition of autophagy in non-CAD arterioles induced a switch from NO to H2O2, while activation of autophagy restored NO-mediated vasodilation in CAD arterioles. In the presence of an autophagy activator, telomerase inhibitor prevented the expected switch (Control: 82±4%; NG-Nitro-l-arginine methyl ester: 36±5%; polyethylene glycol catalase: 80±3). Telomerase activation was unable to restore NO-mediated FMD in the presence of autophagy inhibition in CAD arterioles (control: 72±7%; NG-Nitro-l-arginine methyl ester: 79±7%; polyethylene glycol catalase: 38±9%). We provide novel evidence that autophagy is responsible for the pathological switch in dilator mechanism in CAD arterioles, demonstrating that autophagy acts downstream of telomerase as a common denominator in determining the mechanism of FMD.

Superiority of an Asymmetric Perylene Diimide in Terms of Hydrosolubility, G-Quadruplex Binding, Cellular Uptake, and Telomerase Inhibition in Prostate Cancer Cells.

Perylene diimide (PDI) derivatives have been studied as G-quadruplex ligands that suppress telomerase activity by facilitating G-quadruplex formation of telomeric DNA and the hTERT promoter. PIPER, the prototypical PDI, reduces telomerase activity in lung and prostate cancer cells, leading to telomere shortening and cellular senescence of these cells. However, PIPER suffers from poor hydrosolubility and the propensity to aggregate at neutral pH. In this report, we synthesized a new asymmetric PDI, aPDI-PHis, which maintains one N-ethyl piperidine side chain of PIPER and has histidine as another side chain. The results show that aPDI-PHis is superior to its symmetric counterparts, PIPER and PDI-His, in terms of hydrosolubility, G-quadruplex binding, cellular uptake, and telomerase inhibition in prostate cancer cells. These results suggest that one N-ethyl piperidine side chain of PDI is sufficient for G-quadruplex binding, while another side chain can be tuned to elicit desirable properties. These findings might lead to better PDIs for use as anticancer drugs.

Cycloastragenol protects against glucocorticoid-induced osteogenic differentiation inhibition by activating telomerase.

Glucocorticoid-induced osteoporosis (GIOP) that is mainly featured as low bone density and increased risk of fracture is prone to occur with the administration of excessive glucocorticoids. Cycloastragenol (CAG) has been verified to be a small molecule that activates telomerase. Studied showed that up-regulated telomerase was associated with promoting osteogeneic differentiation, so we explored whether CAG could promote osteogenic differentiation to protect against GIOP and telomerase would be the target that CAG exerted its function. Our results demonstrated that CAG prominently increased the ALP activity, mineralization, mRNA of runt-related transcription factor 2, osteocalcin, osteopontin, collagen type I in both MC3T3-E1 cells and dexamethasone (DEX)-treated MC3T3-E1 cells. CAG up-regulated telomerase reverse transcriptase and the protective effect of CAG was blocked by telomerase inhibitor TMPyP4. Moreover, CAG improved bone mineralization in DEX-induced bone damage in a zebrafish larvea model. Therefore, the study showed that CAG could alleviate the osteogenic differentiation inhibition induced by DEX in vitro and in vivo, and CAG might be considered as a candidate drug for the treatment of GIOP.

Treatment with Imetelstat Improves Myelofibrosis-Related Symptoms and Other Patient-Reported Outcomes in Patients with Relapsed or Refractory Higher-Risk Myelofibrosis

Treatment with Imetelstat Improves Myelofibrosis-Related Symptoms and Other Patient-Reported Outcomes in Patients with Relapsed or Refractory Higher-Risk Myelofibrosis

A Randomized Open-Label, Phase 3 Study to Evaluate Imetelstat Versus Best Available Therapy (BAT) in Patients with Intermediate-2 or High-Risk Myelofibrosis (MF) Refractory to Janus Kinase (JAK) Inhibitor

A Randomized Open-Label, Phase 3 Study to Evaluate Imetelstat Versus Best Available Therapy (BAT) in Patients with Intermediate-2 or High-Risk Myelofibrosis (MF) Refractory to Janus Kinase (JAK) Inhibitor

Correlation Analyses of Imetelstat Exposure with Pharmacodynamic Effect, Efficacy and Safety in a Phase 2 Study in Patients with Higher-Risk Myelofibrosis Refractory to Janus Kinase Inhibitor Identified an Optimal Dosing Regimen for Phase 3 Study

Correlation Analyses of Imetelstat Exposure with Pharmacodynamic Effect, Efficacy and Safety in a Phase 2 Study in Patients with Higher-Risk Myelofibrosis Refractory to Janus Kinase Inhibitor Identified an Optimal Dosing Regimen for Phase 3 Study

Imetelstat Inhibits Telomerase and Prevents Propagation of ADAR1-Activated Myeloproliferative Neoplasm and Leukemia Stem Cells

BACKGROUND Clonal stem cell derived myeloproliferative neoplasms (MPNs) have a propensity to evolve to acute myeloid leukemia (AML). Deregulation of the innate immune deaminase associated with RNA1 (ADAR1) has been linked to malignant progression and therapeutic resistance. Increased expression of the stem cell gene, human telomerase reverse transcriptase (hTERT), has also been linked with malignant transformation. However, the combinatorial role of ADAR1 and hTERT in the evolution of MPN stem cells to therapy resistant acute myeloid leukemia stem cells (LSCs) and the capacity of a telomerase inhibitor, imetelstat, to prevent survival and self-renewal of pre-LSC and LSC had not been established. Recent clinical trials show early signs of efficacy of imetelstat in treatment of myelofibrosis (MF). However, its role in selectively inhibiting pre-LSC transformation to self-renewing LSC has not been elucidated. Here we show that targeting telomerase activity prevents pre-LSC and LSC maintenance both in vitro and in vivo, suggesting telomerase inhibition as an effective strategy for preventing MPN progression. METHODS To quantify hTERT level and ADAR1 activity in the setting of normal HSPC and MPN stem cell evolution, whole genome sequencing (WGS) analysis was performed on 76 normal and MPN blood CD34+ cells and matching saliva samples. Results were compared with RNA-seq of 100 FACS purified young, aged, MPN and AML CD34+CD38- stem cells and CD34+CD38+ progenitor cells. Confocal fluorescence microscopic evaluation of stem cell ADAR1 and hTERT localization, telomere length by Flow-FISH and telomerase activity by TRAP assays, lentiviral ADAR1 overexpression and shRNA knockdown were performed. In vitro stromal co-cultures, and humanized immunocompromised mouse models were established to determine the impact of imetelstat (a oligonucleotide inhibitor of telomerase) on normal, MPN stem cell and LSC maintenance. RESULTS Combined hTERT overexpression, ADAR1 activation and a significant reduction in telomere length correlated with accelerated stem cell aging during MPN progression to AML. Increased ADAR1 mediated adenosine to inosine (A-to-I) transcript editing coincided with accelerated telomere shortening in high risk MPN stem cells. Moreover, lentiviral ADAR1 overexpression enhanced pre-LSC engraftment. Treatment with imetelstat reduced MPN stem cell and LSC propagation in stromal co-cultures as well as in humanized mouse models commensurate with reduced hTERT expression levels and telomerase activity and decreased ADAR1 editing activity. Specifically, stromal co-culture assays revealed that combined treatment with dasatinib at 1 nM, and imetelstat at 1 µM or 5 µM significantly inhibited survival and replating of blast crisis (BC) CML progenitors compared with aged bone marrow progenitors (p &amp;lt; 0.001, ANOVA). As a single agent, imetelstat (5 µM) inhibited survival and replating of pre-LSC derived from myelofibrosis compared with normal bone marrow progenitor samples (p &amp;lt; 0.001, ANOVA). In pre-LSC MPN NSG-SGM mouse models established from 4 different MF samples, a significant reduction in proliferation of human CD45+ cells (p &amp;lt; 0.01, t test) was observed in bone marrow and spleen, when compared with vehicle control. Treatment of humanized LSC mouse models, established with 5 different BC CML, with 30 mg/kg of imetelstat, 3 times a week for 4 weeks resulted in a significant reduction in proliferation of malignant progenitors and human CD45+ cells (p &amp;lt; 0.001, ANOVA). As measured by a Flow-FISH assay, abnormal telomere length was reversed by imetelstat treatment compared with mismatch control (p &amp;lt; 0.05, ANOVA). In addition, FACS analysis revealed a significant reduction in activated beta-catenin expression after imetelstat treatment of LSC engrafted mice compared with vehicle control (p &amp;lt; 0.01, ANOVA). Finally, RNA-seq analysis performed on human CD34+ cells from imetelstat treated LSC mouse models revealed a significant reduction in LSC harboring malignant ADAR1-mediated A-to-I editing at doses that spared normal hematopoietic stem cells. CONCLUSIONS Combined WGS and RNA-Seq analyses, lentiviral ADAR1 overexpression, stromal co-culture assays and humanized pre-LSC and LSC mouse model studies reveal that pre-LSC evolution into LSC coincides with both ADAR1 and hTERT activation, which can be prevented with imetelstat. Disclosures Rizo: Geron Corp: Current Employment, Current equity holder in publicly-traded company. Huang:Geron Corp: Current Employment, Current equity holder in publicly-traded company. Jamieson:Forty Seven Inc: Patents &amp; Royalties; Bristol-Myers Squibb: Other.

Inhibition of MUC1 exerts cell-cycle arrest and telomerase suppression in glioblastoma cells

Mucin 1 (MUC1) is a transmembrane glycoprotein involved in tumorigenesis of diverse cancers. However, the role of MUC1 in glioblastoma (GBM) has not yet been fully explored. In this study, the anticancer mechanism of MUC1 suppression in GBM was investigated. The expression level of MUC1 was analyzed in human glioma and paired normal brain tissues. MUC1 was overexpressed in GBM and was negatively associated with overall survival. Moreover, we silenced MUC1 to investigate its effect in GBM cell lines and found that knockdown of MUC1 inhibited cell proliferation and resulted in cell cycle arrest at G1 phase. MUC1 silencing decreased the phosphorylation of RB1 and increased the expression of CDKN1B. Gene set enrichment analysis showed that a series of genes related to cell cycle, telomere maintenance and transforming growth factor Beta (TGF-β) signaling in epithelial mesenchymal transition (EMT) were influenced by MUC1 knockdown. Notably, the reduced TERT expression levels combined with impaired telomerase activity and the switching of telomere maintenance mechanism to alternative lengthening of telomeres (ALT) were observed after MUC1 knockdown. Our results support the role of MUC1 in oncological process in GBM which can be developed as a therapeutic target for cell cycle control and telomere maintenance mechanism.