Inhibition Of Telomerase Activity Research Articles

Synthesis of Tetrahydrocarbazole-Tethered Triazoles as Compounds Targeting Telomerase in Human Breast Cancer Cells

Telomere shortening and the induction of senescence and/or cell death may result from inhibition of telomerase activity in cancer cells. Herein, the properties of carbazole–triazole compounds targeting telomerase in human breast cancer cells are explored. All derivatives were evaluated for loss of viability in MCF-7 breast cancer cells, with compound 5g identified as the most potent within the examined series. Green synthesis was employed using water, a reusable nano-Fe2O3-catalyzed reaction, and an electrochemical method for the synthesis of tetrahydrocarbazole and triazoles. The crystal data of compound 4 is also reported. Furthermore, in silico analysis predicted that compound 5g may target human telomerase. Molecular docking analysis of compound 5g towards hTERT predicted a binding affinity of −6.74 kcal/mol. In flow cytometry assays, compound 5g promoted apoptosis and cell cycle arrest in the G2-M phase. Finally, compound 5g inhibited the enzymatic activity of telomerase in human breast cancer cells. In conclusion, a green synthesized series of carbazole–triazoles that target telomerase in cancer cells is reported.

Preparation and anticancer activity of telomerase inhibitor TAT-LPTS39 polypeptide.

Telomerase is activated in most cancer cells, and thus telomerase is an ideal target for cancer therapy. The human liver-associated candidate tumour suppressor LPTS/PinX1, is the only human protein reported to bind with the telomerase catalytic subunit telomerase reverse transcriptase (TERT) and inhibit telomerase activity. The C-terminal fragment of LPTS/PinX1 (LPTS/PinX1290-328) contains a telomerase inhibitory domain that is needed for inhibition of telomere elongation and induction of apoptosis. This study prepared the TAT-LPTS39 (TAT-LPTS/PinX1290-328) polypeptide and analysed its effect of the tumour growth. LPTS/PinX1290-328 was fused with TAT [11 amino acid (aa) peptide of the HIV transactivator of transcription protein] to generate the recombinant protein GST-TAT-LPTS39 and was transduced into cells. Telomerase activity was identified by the telomeric repeat amplification protocol (TRAP) and the relative telomere length (RTL) was measured by quantitative real-time polymerase chain reaction (qPCR). The effects of the TAT-LPTS39 protein on cell growth and death were evaluated by 3-(4,5-dimethylthiazolyl)-2,5-diphenyltetrazolium bromide (MTT), cell culture doubling time and flow cytometry assays. The cell derived xenograft (CDX) model was used to examine tumour growth inhibition effect of TAT-LPTS39 polypeptide in vivo. We successfully expressed and purified the recombinant protein GST-TAT-LPTS39 in vitro. The GST-TAT-LPTS39 protein was efficiently delivered into cells, inhibited telomerase activity and the growth of the telomerase-positive liver cancer cells BEL-7404 and QGY7701, and induced the senescence and apoptosis in telomerase-positive Hela, BEL-7404 and QGY7701 cells, but was ineffective to telomerase-negative cells in vitro. The TAT-LPTS39 polypeptide without the GST tag similarly inhibited the growth of telomerase-positive cancer cells Hela and PLC-PRF-5 in vitro, BEL-7404 CDX tumour in vivo and shortened telomere length. The TAT-LPTS39 polypeptide has the ability to inhibit telomerase activity and suppress the growth of all tested human telomerase-positive cancer cells in vitro and in vivo, suggesting a potential anticancer drug development.

Synergistic effect of cobalt ferrite-graphene oxide based hyperthermia and capsaicin to induce apoptosis and inhibit telomerase activity in breast cancer cells

Capsaicin is a bioactive phytochemical of red and chili peppers. It has shown therapeutic properties, including anticancer activities. In this study, the potential anti-telomerase effect of capsaicin, as well as synergic inhibitory effect of this compound in combination with cobalt ferrite-graphene oxide nanocomposites was investigated on breast cancer cell line. For this purpose, cobalt ferrite/graphene oxide (CoFe2O4/GO) nanoparticles were synthesized and characterized. Then, the effect of different concentrations of capsaicin and CoFe2O4/GO nanoparticles, and their combination on the breast adenocarcinoma cell lines (MCF-7 and MCF-10A) were analyzed using MTT assay and quantitative real-time PCR for assessing their effect on the cell viability and the expression changes in telomerase reverse transcriptase (tert), Bax and Bcl2 genes, respectively. The results showed a synergistic effect of capsaicin and CoFe2O4/GO NPs on MCF-7 cell lines that reduced the IC50 value from 0.1 and 1 mg/ml for capsaicin and CoFe2O4/GO nanoparticles, to 0.05 and 0.5 mg ml−1, respectively. Moreover, telomerase and bcl2 genes expression decreased after capsaicin and CoFe2O4/GO NPs treatment; while in contrast, bax gene expression significantly increased. Consequently, capsaicin and CoFe2O4/GO NPs treatment could induce apoptosis and inhibit the growth of breast cancer cells. In conclusion, combinational treatment with capsaicin and CoFe2O4/GO NPs could be considered as an efficient therapeutic regimen for breast cancer.

PINX1 loss confers susceptibility to PARP inhibition in pan-cancer cells

PARP1 is crucial in DNA damage repair, chromatin remodeling, and transcriptional regulation. The principle of synthetic lethality has effectively guided the application of PARP inhibitors in treating tumors carrying BRCA1/2 mutations. Meanwhile, PARP inhibitors have exhibited efficacy in BRCA-proficient patients, further highlighting the necessity for a deeper understanding of PARP1 function and its inhibition in cancer therapy. Here, we unveil PIN2/TRF1-interacting telomerase inhibitor 1 (PINX1) as an uncharacterized PARP1-interacting protein that synergizes with PARP inhibitors upon its depletion across various cancer cell lines. Loss of PINX1 compromises DNA damage repair capacity upon etoposide treatment. The vulnerability of PINX1-deficient cells to etoposide and PARP inhibitors could be effectively restored by introducing either a full-length or a mutant form of PINX1 lacking telomerase inhibitory activity. Mechanistically, PINX1 is recruited to DNA lesions through binding to the ZnF3-BRCT domain of PARP1, facilitating the downstream recruitment of the DNA repair factor XRCC1. In the absence of DNA damage, PINX1 constitutively binds to PARP1, promoting PARP1-chromatin association and transcription of specific DNA damage repair proteins, including XRCC1, and transcriptional regulators, including GLIS3. Collectively, our findings identify PINX1 as a multifaceted partner of PARP1, crucial for safeguarding cells against genotoxic stress and emerging as a potential candidate for targeted tumor therapy.

Circ_0000263 improves radiosensitivity of Hela cells by inhibiting the activity of telomerase protein through miR-338-3p/TERT

Objective: To explore the effect and molecular mechanism of circ_0000263 on HeLa cell activity, apoptosis, telomerase activity, and radiosensitivity. Methods: The Hela cells were divided into si-NC, si-circ, vector, circ_0000263, anti-NC, anti-miR-338-3p, miR-NC, miR-338-3p, si-circ+anti-NC, si-circ+ anti-miR-338-3p, si-circ+vector, si-circ+TERT, sh-NC, sh-circ groups. Reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) was used to detect the expressions of circ_0000263 and miR-338-3p. Cell clone formation array was used to detect cell survival; cell counting kit-8 (CCK-8) to detect cell proliferation; flow cytometry to detect apoptosis; western blot method to detect the expressions of proliferating cell nuclear antigen (PCNA), Cleaved-casp3, telomerase reverse transcriptase (TERT) proteins; double luciferase assay to detect the targeting relationships of circ_0000263 and miR-338-3p, miR-338-3p and TERT; telomere repeat amplification enzyme linked immunosorbent assay (TRAR-ELISA) to detect telomerase activity. Results: Circ_0000263 was highly expressed in Hela cells, miR-338-3p was low expressed, and TERT was highly expressed; circ_0000263 was also highly expressed in Hela cells treated with radiation (P＜0.05). Knockdown of circ_0000263 inhibited the clone formation and cell proliferation ability of HeLa cells, and enhanced the radiosensitivity and apoptosis of HeLa cells. In contrast, knockdown of circ_0000263 decreased PCNA protein expression level and enhanced Cleaved-casp3 protein expression level in HeLa cells (P＜0.05). The apoptosis rate in the si-circ group was (13.19±1.12)%, which was higher than (6.80±0.62)% of si-NC group (P＜0.05). The apoptosis rate in the si-circ+4 Gy group was (24.82±1.57)%, which was higher than (17.00±0.96)% of si-NC+4 Gy group (P＜0.05). Circ_0000263 targeted regulated miR-338-3p, and miR-338-3p targeted regulated TERT. MiR-338-3p was lowly expressed in HeLa cells, and knockdown of circ_0000263 elevated miR-338-3p expression level in HeLa cells. Circ_0000263 regulated TERT expression and inhibited telomerase activity through miR-338-3p. MiR-338-3p/TERT can restore the effect of circ_0000263 on the radiosensitivity of Hela cells. The apoptosis rate in the si-circ+anti-NC group was (27.37±0.89)%, which was higher than (18.22±1.18)% of the si-circ+anti-miR-338-3p group (P＜0.05). The apoptosis rate in the si-circ+vector group was (27.55±0.48)%, which was higher than (20.10±0.68)% of si-circ+TERT group (P＜0.05). After 72 hours of radiation by 4 Gy, the cell survival fraction of si-circ+anti-NC group was 0.41±0.02, which was lower than 0.66±0.03 of the si-circ+anti-miR-338-3p group (P＜0.05); the cell survival fraction of si-circ+vector group was 0.42±0.05, which was lower than 0.70±0.03 of si-circ+TERT group (P＜0.05). Conclusion: Inhibiting the expression of circ_0000263 supresses the proliferation of Hela cells by regulating miR-338-3p/TERT, promotes apoptosis, inhibits telomerase activity, increases the radiosensitivity of cancer cells, and provides a theoretical basis for improving the radiosensitivity of Hela cells.

Potential to use of viral reverse transcriptase inhibitors in oncology

In preparing the review, articles on the functioning of the reverse transcriptase enzyme of endogenous repeat sequences LINE1, the mechanisms of action and antitumor activity of viral reverse transcriptase inhibitors. Articles available in the biomedical literature information databases SciVerse Scopus, PubMed, Web of Science, Russian Science CitationIndex (RSCI) were analyzed. The review used information from 140 publications, of which 95 and 39 were published, respectively, over the last ten and three years, 2 articles present the results of clinical studies, and 45 articles refer to results demonstrating the anticancer properties of the studied compounds in various models in vitro and in vivo. Aim. Based on data on the functional properties of the reverse transcriptase enzyme of endogenous repeat sequences LINE1 (long interspersed nuclear elements 1), analyze the potential use of viral reverse transcriptase inhibitors in oncology, presenting their classification and main mechanisms of action. About 98 % of the human genome consists of repetitive sequences, most of which are represented by mobil genetic elements, the activation of which leads to increased genome instability. These include long (LINE) and short (SINE) interspersed nuclear element repeated DNA sequences interspersed nuclear elements, respectively, which occupy about 45 % of the human genome. Increased expression levels of these sequences in the genome have been identified in many forms of malignant neoplasms. Their transposition occurs due to the expression of LINE1-encoded reverse transcriptase, whichis homologous to viral reverse transcriptase. To date, reverse transcriptase inhibitors of viruses of nucleoside and non-nucleoside structure have been developed and are successfully used in the clinic. These drugs demonstrate an inhibitory effect on both LINE1 reverse transcriptase and telomerase, which provides the tumor cell with the ability to overcome replicative senescence. Due to these properties, these compounds are expected to exhibit both their own antitumor activity and increase the sensitivity of tumor cells to the therapy of malignant neoplasms, which is experimentally confirmed in models of malignant tumors in vitro and in vivo. Use of reverse transcriptase inhibitors in combination therapy seems advisable both to prevent further genome rearrangements caused by LINE1 and to suppress the survival of tumor cells by inhibiting telomerase activity.

PinX1 suppresses cancer progression by inhibiting telomerase activity in cervical squamous cell carcinoma and endocervical adenocarcinoma

PinX1 suppresses cancer progression by inhibiting telomerase activity in cervical squamous cell carcinoma and endocervical adenocarcinoma

Fructose-1,6-bisphosphatase 1 dephosphorylates and inhibits TERT for tumor suppression.

Telomere dysfunction is intricately linked to the aging process and stands out as a prominent cancer hallmark. Here we demonstrate that telomerase activity is differentially regulated in cancer and normal cells depending on the expression status of fructose-1,6-bisphosphatase 1 (FBP1). In FBP1-expressing cells, FBP1 directly interacts with and dephosphorylates telomerase reverse transcriptase (TERT) at Ser227. Dephosphorylated TERT fails to translocate into the nucleus, leading to the inhibition of telomerase activity, reduction in telomere lengths, enhanced senescence and suppressed tumor cell proliferation and growth in mice. Lipid nanoparticle-mediated delivery of FBP1 mRNA inhibits liver tumor growth. Additionally, FBP1 expression levels inversely correlate with TERT pSer227 levels in renal and hepatocellular carcinoma specimens and with poor prognosis of the patients. These findings demonstrate that FBP1 governs cell immortality through its protein phosphatase activity and uncover a unique telomerase regulation in tumor cells attributed to the downregulation or deficiency of FBP1 expression.

Abstract 5922: Characterization of the biological effects of a quadruplex-interacting molecule in dedifferentiated liposarcoma cells

Abstract G-rich nucleic acid sequences can assume, under physiologic conditions, non-B secondary structures called G-quadruplexes (G4). The human genome contains thousands of putative quadruplex forming sequences (PQS), of which telomeres are the most extensively studied. PQS are frequently found in the promoters of oncogenes and transcription factors rather than in tumor suppressor or housekeeping genes, indicating an evolutionary selection of these elements based on gene function and suggesting a pivotal role of G4 in the regulation of gene expression. These observations have provided the rationale to explore G4 targeting as a therapeutic approach in cancer. Several small molecules have been indeed designed and characterized as G4-ligands (G4-L), most of them showing a “multiple-target” binding modality. Dedifferentiated liposarcoma (DDLPS) is a non-lipogenic disease characterized by aggressive local growth and multifocal local recurrences and the ability to elicit distant metastases. At the molecular level, DDLPS is marked by the amplification of the 12q13-q15 chromosomal region, leading to the abnormal expression of the MDM2 oncogene. The gene has emerged as an actionable therapeutic target and, recently, PQS within its promoter have been reported to fold into G4 structures. In addition, in our previous study, we observed that pathways related to telomere maintenance are remarkably up-modulated in DDLPS. These findings open a new avenue to explore the therapeutic potential of G4-L in this malignancy. In the present study, the biological activity of a tetra-substituted naphthalene diimide (NDI) G4-L derivative (SOP1812/QN-302) has been characterized in two patient-derived DDLPS cell lines. In particular, the exposure of DDLPS cells to increasing concentrations of SOP1812 resulted in a marked cytotoxic activity in vitro, with IC50 values within the sub-micromolar range (~0.3 μM). Moreover, DDLPS cells treated with equitoxic amounts of the compound were characterized by an 80-90% inhibition of telomerase activity and a remarkable perturbation in the MDM2-p53 feedback loop, leading to a pronounced accumulation of basal and phosphorylated (S15/S46/S392) p53 protein. These effects were paralleled by a 3-4 time increase in the number of γ-H2AX foci, the appearance of the cleaved form of PARP-1 and a pronounced inhibition of cell growth over time. Altogether, our findings indicate that targeting G4 structures by quadruplex-interacting molecules may represent a potential novel and effective therapeutic strategy in DDLPS. Citation Format: Eisa Naghshineh, Beatrice Tosoni, Lorenzo Di Pietro, Sandro Pasquali, Nadia Zaffaroni, Stephen Neidle, Sara N. Richter, Marco Folini. Characterization of the biological effects of a quadruplex-interacting molecule in dedifferentiated liposarcoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5922.

Roles of Interferon Regulatory Factor 1 in Tumor Progression and Regression: Two Sides of a Coin.

IRF1 is a transcription factor well known for its role in IFN signaling. Although IRF1 was initially identified for its involvement in inflammatory processes, there is now evidence that it provides a function in carcinogenesis as well. IRF1 has been shown to affect several important antitumor mechanisms, such as induction of apoptosis, cell cycle arrest, remodeling of tumor immune microenvironment, suppression of telomerase activity, suppression of angiogenesis and others. Nevertheless, the opposite effects of IRF1 on tumor growth have also been demonstrated. In particular, the "immune checkpoint" molecule PD-L1, which is responsible for tumor immune evasion, has IRF1 as a major transcriptional regulator. These and several other properties of IRF1, including its proposed association with response and resistance to immunotherapy and several chemotherapeutic drugs, make it a promising object for further research. Numerous mechanisms of IRF1 regulation in cancer have been identified, including genetic, epigenetic, transcriptional, post-transcriptional, and post-translational mechanisms, although their significance for tumor progression remains to be explored. This review will focus on the established tumor-suppressive and tumor-promoting functions of IRF1, as well as the molecular mechanisms of IRF1 regulation identified in various cancers.

Antiproliferative and Antitelomerase Effects of Silymarin on Human Colorectal and Hepatocellular Carcinoma Cells.

Silymarin, a widely-used hepatoprotective agent, has shown antitumor properties in both in vitro and animal studies. Currently, there is limited knowledge regarding silymarin's antitelomerase effects on human colorectal cancer and hepatocyte carcinoma cells. In this study, we investigated the antiproliferative and antitelomerase effects of silymarin on four human colorectal cancer and HepG2 hepatocyte carcinoma cell lines. The cell viability and telomerase activity were assessed using MTT and the telomerase repeat amplification protocol assay, respectively. We also investigated the effects of silymarin on the expression of human telomerase reverse transcriptase and its promoter methylation in HepG2 cells by real-time RT-PCR and methylation-specific PCR, respectively. Silymarin treatment inhibited cell proliferation and telomerase activity in all cancer cells. After 24 h of treatment, silymarin exhibited IC50 values ranging from 19 - 56.3 µg/mL against these cancer cells. A 30-min treatment with silymarin at the IC50 concentration effectively inhibited telomerase activity in cell-free extracts of both colorectal cancer and hepatocyte carcinoma cells. Treatment of HepG2 cells with 10 and 30 µg/mL of silymarin for 48 h resulted in a decrease in human telomerase reverse transcriptase expression to 75 and 35% of the level observed in the untreated control (p < 0.01), respectively. Treatment with silymarin (10, 30, and 60 µg/mL) for 48 h did not affect human telomerase reverse transcriptase promoter methylation in HepG2 cells. In conclusion, our findings suggest that silymarin inhibits cancer cell growth by directly inhibiting telomerase activity and downregulating its human telomerase reverse transcriptase catalytic subunit. However, silymarin did not affect human telomerase reverse transcriptase promoter methylation at the concentrations of 10 - 60 µg/mL used in this study.

Murine Myoblasts Exposed to SYUIQ-5 Acquire Senescence Phenotype and Differentiate into Sarcopenic-Like Myotubes, an In Vitro Study.

The musculoskeletal system is one of the most affected organs by aging that correlates well with an accumulation of senescent cells as for other multiple age-related pathologies. The molecular mechanisms underpinning muscle impairment because of senescent cells are still elusive. The availability of in vitro model of skeletal muscle senescence is limited and restricted to a small panel of phenotypic features of these senescent cells in vivo. Here, we developed a new in vitro model of senescent C2C12 mouse myoblasts that, when subjected to differentiation, the resulting myotubes showed sarcopenic features. To induce senescence, we used SYUIQ-5, a quindoline derivative molecule inhibitor of telomerase activity, leading to the expression of several senescent hallmarks in treated myoblasts. They had increased levels of p21 protein accordingly with the observed cell cycle arrest. Furthermore, they had enhanced SA-βgalactosidase enzyme activity and phosphorylation of p53 and histone H2AX. SYUIQ-5 senescent myoblasts had impaired differentiation potential and the resulting myotubes showed increased levels of ATROGIN-1 and MURF1, ubiquitin ligases components responsible for protein degradation, and decreased mitochondria content, typical features of sarcopenic muscles. Myotubes differentiated from senescent myoblasts cultures release increased levels of MYOSTATIN that could affect skeletal muscle cell growth. Overall, our data suggest that a greater burden of senescent muscle cells could contribute to sarcopenia. This study presents a well-defined in vitro model of muscle cell senescence useful for deeper investigation in the aging research field to discover new putative therapeutic targets and senescence biomarkers associated with the aged musculoskeletal system.

Terahertz Photons Inhibit Cancer Cells Long Term by Suppressing Nano Telomerase Activity.

Telomeres are nanoscale DNA-protein complexes to protect and stabilize chromosomes. The reexpression of telomerase in cancer cells is a key determinant crucial for the infinite proliferation and long-term survival of most cancer cells. However, the use of telomerase inhibitors for cancer treatment may cause problems such as poor specificity, drug resistance, and cytotoxicity. Here, we discovered a nondrug and noninvasive terahertz modulation strategy capable of the long-term suppression of cancer cells by inhibiting telomerase activity. First, we found that an optimized frequency of 33 THz photon irradiation effectively inhibited the telomerase activity by molecular dynamics simulation and frequency filtering experiments. Moreover, in vitro experiments showed that telomerase activity in 4T1 and MCF-7 cells significantly decreased by 77% and 80% respectively, after 21 days of regular 33 THz irradiation. Furthermore, two kinds of cells were found to undergo aging, apoptosis, and DNA double-strand breaks caused by telomere crisis, which seriously affected the survival of cancer cells. In addition, the tumorigenicity of 4T1 cells irradiated with 33 THz waves for 21 days in in vivo mice decreased by 70%. In summary, this study demonstrates the potential application of THz modulation in nano therapy for cancer.

Lead Optimization of BIBR1591 To Improve Its Telomerase Inhibitory Activity: Design and Synthesis of Novel Four Chemical Series with In Silico, In Vitro, and In Vivo Preclinical Assessments.

Herein, modifications to the previously reported BIBR1591 were conducted to obtain bioisosteric candidates with improved activities. The % inhibition of the newly afforded candidates against the telomerase target was investigated. Notably, 6f achieved superior telomerase inhibition (63.14%) compared to BIBR1532 and BIBR1591 (69.64 and 51.58%, respectively). In addition, 8a and 8b showed comparable promising telomerase inhibition with 58.65 and 55.57%, respectively, which were recorded to be frontier to that of BIBR1591. 6f, 8a, and 8b were tested against five cancer cell lines related to the lung and liver subtypes. Moreover, 6f was examined on both cell cycle progression and apoptosis induction in HuH7 cancer cells. Furthermore, the in vivo antitumor activity of 6f was further assessed in female mice with solid Ehrlich carcinoma. In addition, molecular docking and molecular dynamics simulations were carried out. Collectively, 6f, 8a, and 8b could be considered potential new telomerase inhibitors to be subjected to further investigation and/or optimization.

Mechanisms of Senescence in Cancer: Positive and Negative Aspects of Cancer Cells Senescence.

Cell senescence was considered an attribute of normal dividing cells, which distinguishing them from cancer cells that do not have a division limit. However, recent studies show that senescence could also occur in cancer cells. Cancer cell senescence could occur as a result of chemotherapy, radiation, inhibition of telomerase activity, induction of DNA damage, changes in the tumor microenvironment, regulation of senescence-related proteins, oxidative stress, inflammation, or epigenetic dysregulation. It seems that the induction of senescence in cancer cells could significantly affect the inhibition of tumor progression, but in some types of cancer, it can affect their invasive character. Furthermore, considering the therapeutic implications of this process, it is essential to consider the positive and negative aspects of cancer cell senescence. It is crucial to understand the molecular mechanisms that induce senescence under specific conditions, considering the potential hazards. In the future, the senescence of cancer cells may contribute to using this property in modern cancer treatment strategies.

BIBR1532 inhibits proliferation and enhances apoptosis in multiple myeloma cells by reducing telomerase activity

Background Multiple myeloma (MM) is a rare haematological disorder with few therapeutic options. BIBR1532, a telomerase inhibitor, is widely used in cancer treatment and has promising outcomes. In this study, we investigated the efficacy and mechanism of action of BIBR1532 in MM. Methods K562 and MEG-01 cells were cultured with BIBR1532 at different concentrations. After 24 and 48 h, cell survival was analyzed. Next, these cells were cultured with 25 and 50 µM BIBR1532 for 48 h, then, cell proliferation, apoptosis, and the expression of the telomerase activity related markers were tested by 5-Ethynyl-2′-deoxyuridine (EdU) staining, flow cytometric analysis, western blot and quantitative real-time PCR (qRT-PCR), respectively. Expression of Bcl-xL, Bad, Survivin, phosphorylation of PI3K, AKT, mTOR, ERK1/2, and MAPK were tested via western blotting. Further experiments were conducted to evaluate the synergistic effects of BIBR1532 and doxorubicin (Dox) or bortezomib (Bor). Results BIBR1532 inhibited K562 and MEG-01 cell survival in a dose- and time-dependent manner. In addition, BIBR1532 hindered cell proliferation while promoting apoptosis, and this effect was enhanced by increasing the BIBR1532 concentration. Moreover, BIBR1532 inhibited TERT and c-MYC expression, PI3K, AKT, mTOR phosphorylation, and facilitated ERK1/2 and MAPK phosphorylation. Additionally, BIBR1532 combined with Dox or Bor showed synergistic effects in MM treatment. Conclusion BIBR1532 inhibits proliferation and promotes apoptosis in MM cells by inhibiting telomerase activity. Additionally, BIBR1532 combined with Dox or Bor exhibited synergistic effects, indicating that BIBR1532 may be a novel medicine for the treatment of MM.

Insulin-like growth factor binding protein-3 induces senescence by inhibiting telomerase activity in MCF-7 breast cancer cells

Insulin-like growth factor binding protein-3 (IGFBP-3) has been known to inhibit cell proliferation and exert tumor-suppressing effects depending on the cell type. In this study, we aimed to show that IGFBP-3 induces cellular senescence via suppression of the telomerase activity, thereby inhibiting MCF-7 breast cancer cell proliferation. We found that the induction of IGFBP-3 in MCF-7 cells enhanced the loss of cell viability. Flow cytometry revealed a higher percentage of non-cycling cells among IGFBP-3-expressing cells than among controls. IGFBP-3 induction also resulted in morphological alterations, such as a flattened cytoplasm and increased granularity, suggesting that IGFBP-3 induces a senescence-like phenotype. The percentage of IGFBP-3 expressing cells with senescence-associated β-galactosidase activity was 3.4 times higher than control cells. Telomeric repeat amplification and real-time PCR showed that IGFBP-3 decreased telomerase activity by reducing the levels of the RNA component (hTR) and catalytic protein component with reverse transcriptase activity (hTERT) of telomerase in a dose-dependent manner. These results suggest that IGFBP-3 is a negative regulator of MCF-7 breast cancer cell growth by inducing senescence through telomerase suppression.

P38 MAPK inhibitor SB203580 enhances anticancer activity of PARP inhibitor olaparib in a synergistic way on non-small cell lung carcinoma A549 cells

The Poly (ADP-ribose) polymerase (PARP) inhibitor (PARPi) olaparib gives promising results against various types of cancers in clinical trials. The combination of drugs always increases therapeutic efficacy because of targeting multiple pathways of cancer progression. Our objective was to explore the potential synergistic anticancer activities of olaparib combined with p38 MAPK inhibitor (MAPKi) SB203580 on non-small cell lung carcinoma (NSCLC) A549 cells. The effects of the individual compound and their combination on cell survival, DNA damage as detected by γH2AX foci, expression of key proteins in Homologous Recombination (HR) and Non-Homologous End Joining (NHEJ) repair, caspase 3 activation, nuclear fragmentation and telomerase regulation were studied in A549 cells. The results showed that olaparib and SB203580 individually reduced cell viability in a dose-dependent manner but combined treatment synergistically reduced cell viability. Olaparib combined with SB203580 significantly reduced error-free HR repair via reducing MRE11-RAD50 and promoted error-prone NHEJ repair by increasing Ku70-Ku80 leading to increased DNA damage-induced apoptosis. Notably, the alteration of proteins in HR/NHEJ pathways, DNA damage and induction of apoptosis was significant by combined treatment but not by 1 μM olaparib treatment alone. In addition, combined treatment reduced telomerase activity more than single treatment via reducing telomerase subunits. These data implicated that the anticancer potential of olaparib was significantly increased by combining SB203580 through increasing DNA damage-induced apoptosis and inhibiting telomerase activity.

Interaction between Human Papillomavirus-Encoded E6 Protein and AurB Induces Cell Immortalization and Proliferation-A Potential Target of Intervention.

The human papillomavirus E6 and E7 oncoproteins interact with a different subset of host proteins, leading to dysregulation of the apoptotic, cell cycle, and signaling pathways. In this study, we identified, for the first time, that Aurora kinase B (AurB) is a bona fide interacting partner of E6. We systematically characterized the AurB-E6 complex formation and its consequences in carcinogenesis using a series of in vitro and cell-based assays. We also assessed the efficacy of Aurora kinase inhibitors in halting HPV-mediated carcinogenesis using in vitro and in vivo models. We showed that AurB activity was elevated in HPV-positive cells, and this correlated positively with the E6 protein level. E6 interacted directly with AurB in the nucleus or mitotic cells. A previously unidentified region of E6, located upstream of C-terminal E6-PBM, was important for AurB-E6 complex formation. AurB-E6 complex led to reduced AurB kinase activity. However, the AurB-E6 complex increased the hTERT protein level and its telomerase activity. On the other hand, AurB inhibition led to the inhibition of telomerase activity, cell proliferation, and tumor formation, even though this may occur in an HPV-independent manner. In summary, this study dissected the molecular mechanism of how E6 recruits AurB to induce cell immortalization and proliferation, leading to the eventual cancer development. Our findings revealed that the treatment of AZD1152 exerted a non-specific anti-tumor effect. Hence, a continuous effort to seek a specific and selective inhibitor that can halt HPV-mediated carcinogenesis should be warranted.

The Role of Natural Flavonoids as Telomerase Inhibitors in Suppressing Cancer Growth.

Cancer is a complex and multifaceted group of diseases characterized by the uncontrolled growth and spread of abnormal cells. While cancer can be challenging and life-altering, advances in research and development have led to the identification of new promising anti-cancer targets. Telomerase is one such target that is overexpressed in almost all cancer cells and plays a critical role in maintaining telomere length, which is essential for cell proliferation and survival. Inhibiting telomerase activity can lead to telomere shortening and eventual cell death, thus presenting itself as a potential target for cancer therapy. Naturally occurring flavonoids are a class of compounds that have already been shown to possess different biological properties, including the anti-cancer property. They are present in various everyday food sources and richly present in fruits, nuts, soybeans, vegetables, tea, wine, and berries, to name a few. Thus, these flavonoids could inhibit or deactivate telomerase expression in cancer cells by different mechanisms, which include inhibiting the expression of hTERT, mRNA, protein, and nuclear translocation, inhibiting the binding of transcription factors to hTERT promoters, and even telomere shortening. Numerous cell line studies and in vivo experiments have supported this hypothesis, and this development could serve as a vital and innovative therapeutic option for cancer. In this light, we aim to elucidate the role of telomerase as a potential anti-cancer target. Subsequently, we have illustrated that how commonly found natural flavonoids demonstrate their anti-cancer activity via telomerase inactivation in different cancer types, thus proving the potential of these naturally occurring flavonoids as useful therapeutic agents.