Down-regulation Of Telomerase Activity Research Articles

Chemoproteomics Reveals That Quaternary Protoberberine Alkaloids Inhibit Telomerase Activity Oncologically by Binding to PES1.

Natural QPAs have anti-cancer property. The prodrugs of QPAs synthesized in our work with significantly improved solubility showed significantly stronger activity in animal experiments. Nevertheless, the mechanism of action of QPAs for treating cancers remains poorly understood. Here, a chemoproteomic study reveals that QPAs non-covalently and multivalently bind to PES1 in CRC cells, which impinges on the direct interaction between hTERT and hTR in the assembly of the telomerase complex, downregulates telomerase activity, and so promotes the aging process of CRC cells. This study is beneficial for us to conduct extensively the pharmaceutical chemistry research of QPAs.

Melatonin Alleviates Age-Associated Endothelial Injury of Atherosclerosis via Regulating Telomere Function.

BackgroundAtherosclerosis is an aging-related disease, partly attributed to telomerase dysfunction. This study aims to investigate whether telomere dysfunction-related vascular aging is involved in the protection mechanism of melatonin (MLT) in atherosclerosis.MethodsYoung and aged ApoE−/− mice were used to establish atherosclerotic mice model. H&E staining and immunofluorescence assay were performed to detect endothelial cell injury and apoptosis. Inflammatory cytokines and oxidative stress-related factors were determined using corresponding commercial assay kits. Telomerase activity was detected by TRAP assay, and SA-β-gal staining was conducted to evaluate cellular senescence. HUVECs were treated with H2O2 for 1 h to induce senescence. Western blot was performed to measure protein expression.ResultsAn obvious vascular endothelial injury, reflected by excessive production of inflammatory cytokines, elevated ROS, MDA and SOD levels, and more apoptotic endothelial cells, was found in atherosclerotic mice, especially in aged mice, which were then greatly suppressed by MLT. In addition, telomere dysfunction and senescence occurred in atherosclerosis, especially in aged mice, while MLT significantly alleviated the conditions. CYP1A1, one of the targeted genes of MLT, was verified to be upregulated in atherosclerotic mice but downregulated by MLT. Furthermore, H2O2 induced a senescence model in HUVECs, which was accompanied with a remarkably increased cell viability loss and apoptosis rate, and a downregulated telomerase activity of HUVECs, and this phenomenon was strengthened by RHPS4, an inhibitor of telomerase activity. However, MLT could partly abolish these changes in H2O2- and RHPS4-treated HUVECs, demonstrating that MLT alleviated vascular endothelial injury by regulating senescence and telomerase activity.ConclusionsCollectively, this study provided evidence for the protective role of MLT in atherosclerosis through regulating telomere dysfunction-related vascular aging.

Reciprocal impacts of telomerase activity and ADRN/MES differentiation state in neuroblastoma tumor biology

Telomere maintenance and tumor cell differentiation have been separately implicated in neuroblastoma malignancy. Their mechanistic connection is unclear. We analyzed neuroblastoma cell lines and morphologic subclones representing the adrenergic (ADRN) and mesenchymal (MES) differentiation states and uncovered sharp differences in their telomere protein and telomerase activity levels. Pharmacologic conversion of ADRN into MES cells elicited consistent and robust changes in the expression of telomere-related proteins. Conversely, stringent down-regulation of telomerase activity triggers the differentiation of ADRN into MES cells, which was reversible upon telomerase up-regulation. Interestingly, the MES differentiation state is associated with elevated levels of innate immunity factors, including key components of the DNA-sensing pathway. Accordingly, MES but not ADRN cells can mount a robust response to viral infections in vitro. A gene expression signature based on telomere and cell lineage-related factors can cluster neuroblastoma tumor samples into predominantly ADRN or MES-like groups, with distinct clinical outcomes. Our findings establish a strong mechanistic connection between telomere and differentiation and suggest that manipulating telomeres may suppress malignancy not only by limiting the tumor growth potential but also by inducing tumor cell differentiation and altering its immunogenicity.

Terminal differentiation into adipocyte and growth inhibition by PPARγ activation in human A549 lung adenocarcinoma cells

ABSTRACT The present study investigated the terminal differentiation capacity into adipocytes and subsequent growth inhibition in A549 cancer cells treated with pioglitazone (PGZ), a PPARγ activator. The rate of cell growth in A549 cells was significantly (P < .05) inhibited in concentrations above 10 μM PGZ while maintaining less cytotoxic effects in MRC-5 fibroblasts. Following 50 μM PGZ treatment, population doubling time (PDT) was significantly (P < .05) increased by inhibition of cell growth, as per increasing PGZ exposure time by up to 4 weeks. The adiposome-like vesicles were commonly observed in the PGZ-treated A549 cells, and the vesicles were highly stained with Oil-Red O solution. In addition, the cell size and expression of GLUT4 and PPARγ were significantly (P < .05) increased, as per increasing PGZ exposure time by up to 4 weeks. The significant (P < .05) down-regulation of telomerase activity and up-regulation of senescence-associated β-galactosidase (SA β-GAL) activity was displayed in the PGZ-treated A549 cells, as per increasing PGZ exposure time by up to 4 weeks. The G1 phase of the cell cycle was also significantly (P < .05) increased in the PGZ-treated A549 cells compared with untreated A549 cells. The present results have demonstrated that activation of PPARγ using PGZ induces cellular differentiation into adipocytes and inhibits cell growth in the A549 cancer cells. The terminal differentiation into adipocytes could offer potent chemotherapy in the cancer cells showing high glucose metabolism.

The Effects of Proteasome Inhibitors on Telomerase Activity and Regulation in Multiple Myeloma Cells.

The importance of telomerase, the enzyme that maintains telomere length, has been reported in many malignancies in general and in multiple myeloma (MM) in particular. Proteasome inhibitors are clinically used to combat effectively MM. Since the mechanism of action of proteasome inhibitors has not been fully described we sought to clarify its potential effect on telomerase activity (TA) in MM cells. Previously we showed that the first generation proteasome inhibitor bortezomib (Brt) inhibits TA in MM cells by both transcriptional and post-translational mechanisms and has a potential clinical significance. In the current study we focused around the anti- telomerase activity of the new generation of proteasome inhibitors, epoxomicin (EP) and MG-132 in order to clarify whether telomerase inhibition represents a class effect. We have exposed MM cell lines, ARP-1, CAG, RPMI 8226 and U266 to EP or MG and the following parameters were assessed: viability; TA, hTERT expression, the binding of hTERT (human telomerase reverse transcriptase) transcription factors and post-translational modifications. Epoxomicin and MG-132 differentially downregulated the proliferation and TA in all MM cell lines. The downregulation of TA and the expression of hTERT were faster in CAG than in ARP-1 cells. Epoxomicin was more potent than MG-132 and therefore further mechanistic studies were performed using this compound. The inhibition of TA was mainly transcriptionally regulated. The binding of three positive regulator transcription factors: SP1, c-Myc and NF-κB to the hTERT promoter was decreased by EP in CAG cells as well as their total cellular expression. In ARP-1 cells the SP1 and c-MYC binding and protein levels were similarly affected by EP while NF-κB was not affected. Interestingly, the transcription factor WT-1 (Wilms’ tumor-1) exhibited an increased binding to the hTERT promoter while its total cellular amount remained unchanged. Our results combined with our previous study of bortezomib define telomerase as a general target for proteasome inhibitors. The inhibitory effect of TA is exerted by several regulatory levels, transcriptional and post translational. SP1, C-Myc and NF-κB were involved in mediating these effects. A novel finding of this study is the role of WT-1 in the regulation of telomerase which appears as a negative regulator of hTERT expression. The results of this study may contribute to future development of telomerase inhibition as a therapeutic modality in MM.

Nonradioactive and Radioactive Telomerase Assays for Detecting Diminished Telomerase Activity in Cancer Cells after Treatment with Retinoid.

Detection of any decrease in telomerase activity in cancer cells and tumor tissues is an important part in assessing overall therapeutic outcomes of a treatment agent in the laboratory and clinical settings. Almost 85% of cancers have activation of telomerase activity that promotes cell proliferation and discourages differentiation to sustain growth of the cancers. Retinoids are highly regarded as the anti-proliferation and pro-differentiation agents that cause down regulation of telomerase activity in the cancer cells. Two (nonradioactive and radioactive) telomeric repeat amplification protocol (TRAP) assays are optimized and fully described for detection of the diminished or abolished telomerase activity in a very low amount of protein extracts from cancer cells after treatment with a natural retinoid or a synthetic retinoid. These highly optimized and improved nonradioactive and radioactive TRAP assays can also be used for determining the presence or absence of telomerase activity in a small amount of any tumor tissue. The results from these TRAP assays can also help decide appropriate therapeutic options for the cancers with or without telomerase activity.

Novel combination of tanshinone I and lenalidomide induces chemo-sensitivity in myeloma cells by modulating telomerase activity and expression of shelterin complex and its associated molecules

Shelterin complex and its associated molecules are imperative for proper functioning and maintenance of human telomeres. These molecules in association with human telomerase have been found altered in most cancers including multiple myeloma thereby proposed them as suitable therapeutic targets. Further, due to aggressive and recurring behavior of myeloma novel, efficacious and safe therapeutic agents for disease prevention are primary requirements for treatment of this disease. This maiden attempt evaluated the anti-proliferative properties of tanshinone I (TanI) alone or in combination with lenalidomide (Len) on myeloma cancer cell lines (RPMI8226 and U226). Further, after drug treatment levels of telomerase activity (TA) and molecular expression (mRNA & protein) of shelterin complex and its associated molecules have also been investigated. Results demonstrated that, TanI significantly inhibited proliferation of myeloma cells in dose and time dependent manner as observed through cytotoxicity assay. Additionally, induction of apoptosis by TanI and in combination with Len was observed in myeloma cells through propidium iodide (PI) staining, annexin V-FITC/PI staining, TUNEL and caspase-3/7 activity assays. Further, drug treatment significantly decreased (p < 0.01) TA and molecular expression of ACD, TERF2IP and TANK1 in comparison to vehicle control (0.1% DMSO) myeloma cells. Thus, this maiden in-vitro study provided initial evidences of therapeutic potential of TanI alone or in combination with chemotherapeutic agent Len as novel anticancer agents in myeloma cells which need further evaluation in future. Lastly, down-regulation of TA and decreased expression of these molecules underscores their potential as plausible therapeutic targets.

Involvement of telomerase activity inhibition and telomere dysfunction in silver nanoparticles anticancer effects.

To investigate the possible mechanisms of telomerase and telomere underlying the anticancer effects of silver nanoparticles (AgNPs). 25nm polyvinylpyrrolidone-coated AgNPs were used. The telomerase activity and telomere function were evaluated. The anticancer effects of AgNPs were gauged with cell viability assay under different statement of telomerase and telomere. AgNPs could inhibit telomerase activity and lead to telomere shortening and dysfunction. Overexpression of telomerase attenuated the anticancer activity of AgNPs, whereas downregulation of telomerase activity or dysfunction of the telomere enhanced the cytotoxicity of AgNPs in HeLa cells. Our findings provided strong evidence that the anticancer effects of AgNPs were mediated via interference with the telomerase/telomere.

Down regulation of human telomerase reverse transcriptase (hTERT) expression by BIBR1532 in human glioblastoma LN18 cells.

Increased telomerase activity can be blocked by targeting the hTERT activity at both RNA and catalytic subunits. Various inhibitors had been used to regulate hTERT activity in glioblastoma cell lines and showed promising results. The present study hypothesized that the telomerase specific inhibitor BIBR1532 can effectively down-regulate the telomerase activity in LN18 glioblastoma cell line. LN18 glioblastoma cell line was treated with various concentrations of BIBR1532 at different time intervals. MTT assay was performed to determine cell viability after BIBR1532 treatment. hTERT mRNA and protein expression were determined by qRT-PCR and western blotting, respectively. Flow cytometry and TRAP assay was performed to detect the rate of apoptosis and telomerase activity in treated and control samples. One-way ANOVA was performed to compare the mean values of variables in control and BIBR1532 treated groups. LN18 cells showed a significant dose dependent cytotoxic effect after treatment with BIBR1532. hTERT mRNA expression in cells treated with 25, 100 and 200μM BIBR1532 treated groups was decreased ~21, ~61.2, and ~77%, respectively (p<0.05). We also observed that, BIBR1532 treatment reduced the expression of hTERT protein in LN18 cells in a dose dependent manner. The Flow cytometry data showed that, the drug induced significant increase in the total percentage of apoptotic cells with 200μM concentration of BIBR1532 at all time points. BIBR1532 exhibited potent inhibition of telomerase activity in a dose-dependent manner in LN18 cells. BIBR1532 could induce apoptosis in LN18 cells through the downregulation of telomerase activity at transcriptional and translational level. We conclude that BIBR1532 may be a therapeutic agent to suppress telomerase activity, however, further efforts are necessary in order to explore this therapeutic strategy.

APIGENIN INCREASES CISPLATIN INHIBITORY EFFECTS ON THE TELOMERASE ACTIVITY OF TRIPLE NEGATIVE BREAST CANCER CELLS

Inhibition of telomerase activity has emerged as a promising strategy to combat cancer cells, especially ones with no specific molecular targets such as triple negative breast cancer (TNBC). Cisplatin, a chemotherapeutic drug, is causing DNA damage while apigenin, a plant-derived antioxidant, induces apoptosis in various cancer cell types. Little is known about their combined ability to inhibit telomerase activity in TNBC cells. In the current study, the effect of cisplatin in combination with apigenin was investigated with regards to telomerase activity and expression of the telomerase catalytic subunit hTERT as well as Heat Shock Protein 90 (Hsp90) and p23 in two types of TNBC (MDA-MB-231; HCC1806) and one non-tumorigenic (MCF10A) epithelial cell line. The results showed that the combined treatment of cisplatin and apigenin significantly down-regulated telomerase activity. The inhibition of telomerase activity was accompanied by a down-regulation of hTERT, Hsp90 and p23 at transcriptional and translational level in both TNBC cells, as compared to control cells. The results of the current study suggest that apigenin and cisplatin synergistically inhibit telomerase activity by downregulating the enzyme’s catalytic subunit. However, the exact roles of Hsp90 and p23 in the regulation of telomerase activity requires further investigation as they seem to be TNBC subtype-specific.

Alternative splicing of telomerase catalytic subunit hTERT generated by apoptotic endonuclease EndoG induces human CD4+ T cell death

Telomerase activity is regulated by alternative splicing of its catalytic subunit human Telomerase Reverse Transcriptase (hTERT) mRNA. Induction of a non-active spliced hTERT leads to inhibition of telomerase activity. However, very little is known about the mechanism of hTERT mRNA alternative splicing. The aim of this study was to determine the role of the apoptotic endonuclease EndoG in alternative splicing of hTERT and telomerase activity. A strong correlation was identified between EndoG expression levels and hTERT splice variants in human CD4+ and CD8+ T lymphocytes. Overexpression of EndoG in CD4+ T cells down-regulated the expression of the active full-length hTERT variant and up-regulated expression of the non-active spliced variant. A reduction in full-length hTERT transcripts down-regulated telomerase activity. Long-term in vitro cultivation of EndoG-overexpressing CD4+ T cells led to dramatically shortened telomeres, conversion of cells into a replicative senescence state, and activation of the BCL2/BAX-associated apoptotic pathway finally leading to cell death. These data indicated the participation of EndoG in alternative mRNA splicing of the telomerase catalytic subunit hTERT, regulation of telomerase activity and determination of cell fate.

Rhodospirillum rubruml-asparaginase targets tumor growth by a dual mechanism involving telomerase inhibition

Rhodospirillum rubruml-asparaginase mutant RrA E149R, V150P, F151T (RrA) was previously identified to down-regulate telomerase activity along with catalyzing the hydrolysis of l-asparagine. The aim of this study was to define the effect of prolonged RrA exposure on telomerase activity, maintenance of telomeres and proliferation of cancer cells in vitro and in vivo. RrA could inhibit telomerase activity in SCOV-3, SkBr-3 and A549 human cancer cell lines due to its ability to down-regulate the expression of telomerase catalytic subunit hTERT. Telomerase activity in treated cells did not exceeded 29.63 ± 12.3% of control cells. Continuous RrA exposure of these cells resulted in shortening of telomeres followed by cell death in vitro. Using real time PCR we showed that length of telomeres in SCOV-3 cells has been gradually decreasing from 10105 ± 2530 b.p. to 1233 ± 636 b.p. after 35 days of cultivation. RrA treatment of xenograft models in vivo showed slight inhibition of tumor growth accompanied with 49.5–53.3% of decrease in hTERT expression in the all tumors. However down-regulation of hTERT expression, inhibition of telomerase activity and the loss of telomeres was significant in response to RrA administration in xenograft models. These results should facilitate further investigations of RrA as a potent therapeutic protein.

Cisplatin-induced apoptotic endonuclease EndoG inhibits telomerase activity and causes malignant transformation of human CD4+ T lymphocytes

Alternative splicing of telomerase catalytic subunit hTERT pre-mRNA (human Telomerase Reverse Transcriptase) regulates telomerase activity. Increased expression of non-active splice variant hTERT results in inhibition of telomerase. Apoptotic endonuclease EndoG is known to participate in hTERT alternative splicing. Expression of EndoG can be induced in response to DNA damages. The aim of this study was to determine the ability of a DNA-damaging compound, cisplatin, to induce EndoG and its influence on alternative splicing of hTERT and telomerase activity in human CD4+ Т lymphocytes. Overexpression of EndoG in CD4+ T cells downregulated the expression of active full-length hTERT variant and upregulated its non-active spliced variant. Reduction of full-length hTERT caused downregulation of telomerase activity, shortening of telomeres length during cell divisions, converting cells to the replicative senescence state, activation of apoptosis and finally cell death. Few cells survived and underwent malignant transformation. Transformed cells have increased telomerase activity and proliferative potential compare to initial CD4+ T cells. These cells have phenotype of T lymphoblastic leukemic cells and are able to form tumors and cause death in experimental mice.

Cisplatin-induced apoptotic endonuclease EndoG inhibits telomerase activity and causes malignant transformation of human CD4+ T lymphocytes

Alternative splicing of telomerase catalytic subunit hTERT pre-mRNA (human Telomerase Reverse Transcriptase) regulates telomerase activity. Increased expression of non-active splice variant hTERT results in inhibition of telomerase. Apoptotic endonuclease EndoG is known to participate in hTERT alternative splicing. Expression of EndoG can be induced in response to DNA damages. The aim of this study was to determine the ability of a DNA-damaging compound, cisplatin, to induce EndoG and its influence on alternative splicing of hTERT and telomerase activity in human CD4+ Т lymphocytes. Overexpression of EndoG in CD4+ T cells downregulated the expression of active full-length hTERT variant and upregulated its non-active spliced variant. Reduction of full-length hTERT caused downregulation of telomerase activity, shortening of telomeres length during cell divisions, converting cells to the replicative senescence state, activation of apoptosis and finally cell death. Few cells survived and underwent malignant transformation. Transformed cells have increased telomerase activity and proliferative potential compare to initial CD4+ T cells. These cells have phenotype of T lymphoblastic leukemic cells and are able to form tumors and cause death in experimental mice.

DHA-enriched fish oil upregulates cyclin-dependent kinase inhibitor 2A (P16INK) expression and downregulates telomerase activity without modulating effects of PPARγ Pro12Ala polymorphism in type 2 diabetic patients: A randomized, double-blind, placebo-controlled clinical trial

The present study investigated the effects of docosahexaenoic acid (DHA)-enriched fish oil supplement on telomerase activity, mRNA expression of P16INK, IL-6, and TNF-α considering Pro12Ala polymorphism in the PPARγ gene. In this double-blind randomized controlled trial, 72 PPARγ Pro12Ala polymorphism genotyped type 2 diabetic patients aged 30-70 years were randomly assigned to receive 2.4 gr of DHA-enriched fish oil or a placebo for 8 weeks. Genotyping of the Pro12Ala polymorphism in the PPARγ gene was assessed using polymerase chain reaction-restriction length polymorphism (PCR-RFLP), telomerase activity in the peripheral blood mononuclear cell (PBMC) was measured using PCR-ELISA based on the telomeric repeat amplification protocol (TRAP), and changes in the mRNA expression of P16, IL-6, and TNF-α were measured using real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). In the DHA group, telomerase activity was decreased (p=0.001) during the intervention. In addition, between-group comparisons showed significant differences in the changes in telomerase activity (p=0.003) and P16 mRNA expression (p=0.028) and non-significant differences in TNF-α and IL-6 mRNA expression. The gene*DHA interaction could not affect changes in P16, IL-6, or TNF-α mRNA expression or in telomerase activity in PBMC. Short-time DHA-enriched fish oil supplementation caused increased levels of P16 expression and a decline in telomerase activity compared with the control group without modulating the effects of Pro12Ala polymorphism on the PPARγ gene. Because of the positive correlation between P16 activity and cellular senescence, the possibility of senescence stimulation by DHA is proposed.

Magnesium Deficiency Results in Oxidation and Fragmentation of DNA, Down Regulation of Telomerase Activity, and Ceramide Release in Cardiovascular Tissues and Cells: Potential Relationship to Atherogenesis, Cardiovascular Diseases and Aging

Magnesium Deficiency Results in Oxidation and Fragmentation of DNA, Down Regulation of Telomerase Activity, and Ceramide Release in Cardiovascular Tissues and Cells: Potential Relationship to Atherogenesis, Cardiovascular Diseases and Aging

Apoptotic endonuclease EndoG induces alternative splicing of telomerase catalytic subunit hTERT and death of tumor cells

Telomerase activity is known to be regulated by alternative splicing of its catalytic subunit hTERT (human Telomerase Reverse Transcriptase) mRNA. Induction of non-active spliced hTERT leads to inhibition of telomerase activity. However, very little is known about the mechanism of hTERT mRNA alternative splicing. The aim of this study was to determine the role of apoptotic endonuclease EndoG in alternative splicing of hTERT and telomerase activity. Strong correlation was found between expression of EndoG and hTERT splice-variants in 12 colon cancer cell lines. Overexpression of EndoG in СаСо-2 cells downregulated the expression of active full-length hTERT variant and upregulated non-active spliced variant. Reduction of full-length hTERT caused downregulation of telomerase activity, dramatically shortening of telomeres length during cell divisions, converting cells to the replicative senescence state, activation of apoptosis and finally cell death. These data indicated the participation of EndoG in alternative splicing of mRNA of telomerase catalytic subunit, regulation of telomerase activity and cell fate.

Inhibition of cell growth and down-regulation of telomerase activity by amygdalin in human cancer cell lines

The purpose of this study was to examine the effect of amygdalin on cell growth and telomerase activity in human cancer and MRC-5 fibroblast cell lines. The level of β-glucosidase activity for releasing cyanide was significantly (P < .05) higher in cancer cell lines (A-549, MDA-MB-231, MCF-7 and U87-MG) than in MRC-5 fibroblasts. Growth rate of cancer cells was apparently inhibited in concentrations above 10 mg/ml amygdalin with senescent-like abnormal morphology. Whereas the effects were absent or marginally detected in MRC-5 fibroblasts. High incidence of β-galactosidase activity was observed in amygdalin-treated cancer cells, compared with that of untreated control while no difference was observed between the control and amygdalin-treated MRC-5 fibroblasts. Furthermore, level of telomerase activity was significantly (P < .05) higher (∼8–13 fold) in cancer cell lines along with high expression of telomerase reverse transcriptase (TERT) and telomerase RNA component (TERC) than in MRC-5 fibroblasts which did not expressed TERT and TERC. However, telomerase activity was significantly (P < .05) down-regulated in amygdalin-treated cancer cells with the decreased expression of TERT and TERC compared with control cancer cells. There were no difference in the telomerase activity between control and amygdalin-treated MRC-5 fibroblasts. Based on these observations, we concluded that amygdalin treatment offers a valuable option for the cancer treatment, causing inhibition of cell growth and down-regulation of telomerase activity in human cancer cell lines by increasing β-glucosidase activity.

Influence and mechanism of PinX1 gene on the chemotherapy sensitivity of nasopharyngeal carcinoma cells in response to Cisplatin

To explore the influence and mechanism of PinX1 gene on the chemotherapy sensitivity of nasopharyngeal carcinoma cells in response to Cisplatin. Transfected nasopharyngeal carcinoma 5-8F cell lines with pCDH-CMV-PinX1-copGFP vector constructed by lentivirus to generate Lenti-PinX1-5-8F cells containing PinX1 gene, using Lenti-Ctrl-5-8F cell (blank vector without PinX1 gene was used to transfect 5-8F cell lines) and 5-8F cell as controls. Expression of PinX1 gene, telomerase activity, the inhibition of cancer cells proliferation, combined anticancer effect with Cisplatin and the expression of lung resistance protein (LRP) and Bcl-2 were detected with fluorescent quantitation polymerase chain reaction (PCR), flow cytometry, thiazolyl blue (MTT) method, areole test, Western blot and drug sensitivity test, respectively, in four groups (Lenti-PinX1-5-8F cell + Cisplatin, Lenti-PinX1-5-8F cell, Cisplatin and 5-8F cell) so as to explore the influence and mechanism of PinX1 gene on the chemotherapy sensitivity of nasopharyngeal carcinoma cells in response to Cisplatin. The telomerase activity in Lenti-PinX1-5-8F cell (0.146 ± 0.004) was lower than those in the other two control cells (Lenti-Ctrl-5-8F cell: 0.967 ± 0.016, 5-8F cell: 1.000 ± 0.034, both P < 0.01). The cancer cell biological activity could be intensively inhibited by 16 µg/ml Cisplatin after lower level telomerase activity induced by PinX1 gene. Proliferation index (PI) (%) in Lenti-PinX1-5-8F cell + Cisplatin (14.39 ± 3.66) was also less than the other groups (Lenti-PinX1-5-8F cell, Cisplatin and 5-8F cell groups, 32.97 ± 3.00, 31.18 ± 4.24 and 47.19 ± 4.19, all P < 0.01). And same time, the expressions of LRP (0.64 ± 0.14) and Bcl-2 (0.57 ± 0.12) protein in Lenti-PinX1-5-8F cells were obviously reduced than those in other two group cells (Lenti-Ctrl-5-8F cell: 0.84 ± 0.19 and 0.81 ± 0.16; 5-8F cell: 0.83 ± 0.35 and 0.78 ± 0.27; all P < 0.01). PinX1 gene can enhance the chemotherapy sensitivity of nasopharyngeal carcinoma cells in response to Cisplatin, which may be mediated by the down-regulation of telomerase activity and the inhibition of LRP and Bcl-2 gene in nasopharyngeal carcinoma cells.

Pro-apoptotic and anti-proliferative effects of 3,3'-diindolylmethane in nasopharyngeal carcinoma cells via downregulation of telomerase activity.

The pro-apoptotic and anti-proliferative effects of 3,3'-diindolylmethane (DIM) in various tumor cell types have been widely investigated. The underlying mechanisms were suggested to include cell cycle arrest, cell signaling inhibition and downregulation of the androgen receptor. The present study demonstrated that DIM induced apoptosis and inhibited proliferation in nasopharyngeal carcinoma cells by downregulating the activity of telomerase. The nasopharyngeal carcinoma cell line 5‑8F was selected for this purpose. A cell counting kit‑8 assay and flow cytometry were performed to detect apoptosis and proliferation of 5‑8F cells, respectively, which revealed the pro‑apoptotic and anti‑proliferative effects of DIM. Telomerase activity was detected using a telomeric repeat amplification protocol assay, which revealed that the telomerase activity was inhibited by DIM in a dose‑dependent manner. Reverse transcription polymerase chain reaction was used to detect the mRNA expression levels of human telomerase reverse transcriptase (hTERT) and human telomerase RNA (hTR), and western blot analysis was used to detect the protein expression of hTERT. The results showed that the mRNA and protein expression of hTERT were downregulated in 5‑8F cells following treatment with DIM; however, the mRNA expression of hTR remained unchanged, suggesting that hTERT was the target of DIM. To further identify the target, the length of telomeres was continually measured using a telomere length detection kit, revealing that the telomeres were shortened by DIM in an concentration‑dependent manner. The present study confirmed that DIM had pro‑apoptotic and anti‑proliferative effects in nasopharyngeal carcinoma cells by regulating telomerase.