Telomerase activity correlates with tumor aggressiveness and reflects therapy effect in breast cancer

Impact of khat (Catha edulis) and oral contraceptive use on telomerase levels and tumor suppressor genes p53 and p21 in normal subjects and breast cancer patients

This study aimed to evaluate the effects of oral contraceptive (OC) use, khat chewing, and their combined effect on telomerase level and tumor suppressor genes, p53 and p21 in breast cancer (BC) patients and normal volunteers. 140 Yemeni women aged 25-40 years old enrolled, 60 newly diagnosed pretreated BC patients, and 80 control subjects. Venous blood (5 ml) was collected and the results showed BC patients to have significantly raised levels of telomerase, p53, and p21 compared to the control group. The use of OCs significantly raised telomerase in control group with no effect in BC patients; whereas p53 and p21 were significantly increased in BC patients. On the other hand, khat chewing significantly increased p53 in controls and BC patients, whereas p21 was significantly raised in BC patients. The combined use of OCs and khat chewing significantly increased telomerase and p53 in control group, and significantly increased p53 and p21 in BC patients. Telomerase was shown to be a risk factor (OR 4.4) for BC, and the use of OCs was a high-risk factor for increasing telomerase (OR 27.8) in normal subjects. In contrast, khat chewing was shown to be protective (OR 0.142), and the combined use of OCs and khat chewing decreased the risk factor of telomerase from OR 27.8 to 2.1.

Retrospective Analysis of the Clinical Characteristics of Patients with Breast Cancer Treated with Telomerase Peptide Immunotherapy Combined with Cytotoxic Chemotherapy

Purpose

Telomerase activation, a critical step in cancer progression, occurs in approximately 95% of breast cancer cases. Telomerase is an attractive therapeutic target for breast cancer owing to its unique expression pattern. GV1001, a telomerase-derived peptide, is loaded onto human leukocyte antigen (HLA) class II antigen-presenting cells and binds to CD4+ T cell activating immune responses. This study aimed to evaluate the effectiveness and safety of co-administration of GV1001 and cytotoxic chemotherapy in patients with heavily-treated metastatic breast cancer.

Patients and methods

We analyzed 63 patients with breast cancer who received both GV1001 and cytotoxic chemotherapy. The GV 1001 administration methods involves 0.56 mg intradermal injection three times during the first week, one time at weeks 2, 3, 4, and 6, and then once every 28 days. The primary endpoint of this study was quality of life according to EORTC QLO-C30 and EQ-5D, while the secondary endpoint was the antitumor response according to RECIST 1.1, progression-free survival, overall survival, and toxicity profile.

Results

In 34 patients with HR+ breast cancer evaluable for tumor response, the disease control rate (DCR) and overall response rate (ORR) were 58.8% and 26.4%, respectively. The DCR and ORR were 66.6% and 28.5% in 21 patients with HER-2+ and 50% and 25% in patients with triple-negative breast cancer (TNBC), respectively. The median progression free survival was 10.4, 8.7, and 5.6 months in HR+, HER-2+, TNBC, respectively. The overall survival was 19.7, 13.2, and 9.4 months for patients with HR+, HER-2+, and TNBC, respectively. Most patients had an improved quality of life with statistically significant differences in some variables. The patients in this study experienced no additional toxicities other than the cytotoxic chemotherapy-associated side effects.

Conclusion

GV1001 is a relatively safe anticancer vaccine for patients with heavily-treated breast cancer and can to improve the quality of life.

Exploring breast cancer exosomes for novel biomarkers of potential diagnostic and prognostic importance

The comprehensive bioinformatics analysis of breast cancer exosomes revealed that HSP90AA1, CCT2, and ENO1 were novel hub genes in the giant protein-protein interaction network of 110 exosomal proteins. Exosomes and their cargo such as discrete proteins, nucleic acids, and lipids are having potential role in the pathophysiology of breast cancer (BC). This study showed that the identified hub genes were particularly abundant in GO and KEGG pathways relevant to the positive regulation of telomerase. In addition, these hub genes were found to be considerably overexpressed in breast adenocarcinoma patients compared to healthy controls, and further, this overexpression is linked to the poor prognosis in BC patients. Furthermore, the ROC analysis revealed that CCT2 gene has strong diagnostic and prognostic value for BC. Additionally, this in silico analysis found that the anticancer agents and HSP90 inhibitors such as ganetespib, retaspimycin, and tanespimycin would have considerable potential in the treatment of BC. Overall, this study findings imply that HSP90AA1, a molecular chaperon and CCT2, a chaperonin would serve as diagnostic and prognostic biomarkers, respectively, for BC. However, these findings need to be further confirmed by laboratory and clinical studies for validating their potential applications.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03422-w.

Hormonal regulation of telomerase activity and hTERT expression in steroid-regulated tissues and cancer

Naturally, in somatic cells chromosome ends (telomeres) shorten during each cell division. This process ensures to limit proliferation of somatic cells to avoid malignant proliferation; however, it leads to proliferative senescence. Telomerase contains the reverse transcriptase TERT, which together with the TERC component, is responsible for protection of genome integrity by preventing shortening of telomeres through adding repetitive sequences. In addition, telomerase has non-telomeric function and supports growth factor independent growth. Unlike somatic cells, telomerase is detectable in stem cells, germ line cells, and cancer cells to support self-renewal and expansion. Elevated telomerase activity is reported in almost all of human cancers. Increased expression of hTERT gene or its reactivation is required for limitless cellular proliferation in immortal malignant cells. In hormonally regulated tissues as well as in prostate, breast and endometrial cancers, telomerase activity and hTERT expression are under control of steroid sex hormones and growth factors. Also, a number of hormones and growth factors are known to play a role in the carcinogenesis via regulation of hTERT levels or telomerase activity. Understanding the role of hormones in interaction with telomerase may help finding therapeutical targets for anticancer strategies. In this review, we outline the roles and functions of several steroid hormones and growth factors in telomerase regulation, particularly in hormone regulated cancers such as prostate, breast and endometrial cancer.

Detection of Tetraplex DNA and Detection by Tetraplex DNA

G-quardruplex (G4) DNA forms through the gathering together of G-quartet planes formed with four guanine (G) bases. G4 DNA stabilizes with potassium ions (K+) by coordination with the G-quartet center. Fluorometric G4 DNA carrying the fluorescence resonance energy transfer (FRET) chromophore pair at both termini has been applied for the fluorometric sensing or imaging of K+ under a homogeneous aqueous medium. This system has realized non-conventional K+ selectivity over the sodium ion (Na+). The selectivity of the fluorescence G4 was converted to Na+ from K+ with a modification of its sequence. On the other hand, G4 DNA detection has been achieved in terms of cancer diagnosis because of a strong relationship of G4 DNA and cancer development. Ligands interacting with G4 are expected to have anti-cancer potential. In addition, fluorometric G4 ligands have been developed and tested as tools for the dynamic monitoring of G4 in living cells. Moreover, fluorometric G4 DNA has been utilized to evaluate the G4 ligand performance.

Effect of bisphenols on telomerase expression and activity in breast cancer cell lines

Bisphenol A (BPA), a monomer of polycarbonates and resins, was shown to induce the expression of telomerase enzyme which has been associated with breast cancer development and progression. However, the effects of BPA analogues, bisphenol F (BPF) and bisphenol S (BPS) on telomere-linked pathway have not been evaluated. Herein, MCF-7 (estrogen receptor (ER)-positive) and MDA-MB-231 (ER-negative) cells were treated with BPA, BPF and BPS ± estrogen receptor inhibitor (ERI), for 24 and/or 48 h. RNA expression and enzymatic activity of telomerase were measured using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and telomeric repeat amplification protocol (TRAP); respectively. Relative telomere length (RTL) was also measured using quantitative PCR. After 24 h, the three bisphenols resulted in a 2-3 folds increase in expression and activity of telomerase in MCF-7 but not in MDA-MB-231 cells, and this increase was prevented upon co-treatment with ERI. The observed increase in the expression and activity of telomerase after 24 h of treatment with bisphenols was associated with differential and modest ER-dependent lengthening in RTL at 48 h. Our results show that telomerase potentially mediates the effects of the three bisphenols in ER-positive breast carcinoma. Hence, further investigation is warranted to elucidate the telomerase-linked pathways that could underlie bisphenol-related effects.

Cross-Platform Cancer Cell Identification Using Telomerase-Specific Spherical Nucleic Acids

Distinguishing tumor cells from normal cells holds the key to precision diagnosis and effective intervention of cancers. The fundamental difficulties, however, are the heterogeneity of tumor cells and the lack of truly specific and ideally universal cancer biomarkers. Here, we report a concept of tumor cell detection, bypassing the specific genotypic and phenotypic features of different tumor cell types and directly going toward the hallmark of cancer, uncontrollable growth. Combining spherical nucleic acids (SNAs) with exquisitely engineered molecular beacons (SNA beacons, dubbed SNAB technology) is capable of identifying tumor cells from normal cells based on the molecular phenotype of telomerase activity, largely bypassing the heterogeneity problem of cancers. Owing to the cell-entry capability of SNAs, the SNAB probe readily achieves tumor cell detection across multiple platforms, ranging from solution-based assay, to single cell imaging and in vivo solid tumor imaging (unlike PCR that is restricted to cell lysates). We envision the SNAB technology will impact cancer diagnosis, therapeutic response assessment, and image-guided surgery.

Telomerase Activity in Breast Cancer in Western India (Gujarat)

The purpose of this study was to examine the association of telomerase activity with clinical and histopathological prognostic variables in primary breast cancer (n=64). Telomerase activity in breast cancer was also compared with that in benign (n=10) and non-malignant tissues (n=8; post-lumpectomy tissues histopathologically defined as containing no residual tumor). The parameter was assessed using the Telomerase PCR ELISA kit. Values above OD 0.120 were considered positive. Estrogen and progesterone receptors (ER and PgR) were assayed by the dextran-coated charcoal method and levels >10 fmol/mg cytosol protein were taken as positive. Telomerase activity was detected in 20% and 50% of the patients with benign lesions and primary breast cancer, respectively, and in 50% of post-lumpectomy breast tissues histopathologically defined as containing no residual tumor. Telomerase activity was present in all stages of breast carcinoma and showed a significant inverse correlation with lymph node status (p=0.006), lymphatic invasion (p=0.035) and necrosis (p=0.033). Moreover, when stage II patients were grouped according to nodal involvement, a trend towards significance was observed (p=0.055). No correlation was observed with ER and PgR. The results of our study suggest that telomerase activity might be associated with the presence of cancer cells. Furthermore, telomerase activation may occur early in breast cancer and may be periodically downregulated during subsequent tumor progression.

Exploring the Dynamics of Propeller Loops in Human Telomeric DNA Quadruplexes Using Atomistic Simulations

We have carried out a series of extended unbiased molecular dynamics (MD) simulations (up to 10 μs long, ∼162 μs in total) complemented by replica-exchange with the collective variable tempering (RECT) approach for several human telomeric DNA G-quadruplex (GQ) topologies with TTA propeller loops. We used different AMBER DNA force-field variants and also processed simulations by Markov State Model (MSM) analysis. The slow conformational transitions in the propeller loops took place on a scale of a few μs, emphasizing the need for long simulations in studies of GQ dynamics. The propeller loops sampled similar ensembles for all GQ topologies and for all force-field dihedral-potential variants. The outcomes of standard and RECT simulations were consistent and captured similar spectrum of loop conformations. However, the most common crystallographic loop conformation was very unstable with all force-field versions. Although the loss of canonical γ-trans state of the first propeller loop nucleotide could be related to the indispensable bsc0 α/γ dihedral potential, even supporting this particular dihedral by a bias was insufficient to populate the experimentally dominant loop conformation. In conclusion, while our simulations were capable of providing a reasonable albeit not converged sampling of the TTA propeller loop conformational space, the force-field description still remained far from satisfactory.

Telomerase activity in breast cancer patients: association with poor prognosis and more aggressive phenotype

Telomerase expression is an important mechanism of tumor unlimited replicative potential. The aim of this study was to evaluate prognostic impact of telomerase activity in breast cancer patients and to correlate telomerase activity with established prognostic factors. We analyzed tissue of 102 malignant breast lesions and 20 healthy breast tissues. Telomerase activity was determined by telomeric repeat amplification protocol assay. Telomerase activity was present in 77 (75.49 %) of 102 breast cancers. Telomerase activity in breast cancers was statistically significantly higher in comparison with the activity in normal breast tissue. The levels of telomerase activity were significantly positively correlated with tumor size, axillary nodal status, histological grade, HER-2/neu protein expression in tumor tissue and expression of the nuclear antigen Ki-67. A statistically significant negative correlation was found between the presence of ER and telomerase activity. There was no correlation between telomerase activity and concentration of PR or the age of patients. Kaplan-Meier analysis showed that patients with higher telomerase activity had significantly shorter 10-year disease-free survival (p < 0.0001) and 10-year overall survival (p < 0.0001) than those with lower telomerase activity. These results were confirmed by logistic regression analysis. Our results support the prognostic role of telomerase activity and its relationship with the more aggressive phenotype of breast cancer.

Effect of estradiol and bisphenol A on human hepatoblastoma cell viability and telomerase activity

Sex hormones from environmental and physiological sources might play a major role in the pathogenesis of hepatoblastoma in children. This study investigated the effects of estradiol and bisphenol A on the proliferation and telomerase activity of human hepatoblastoma HepG2 cells. The cells were divided into 6 treatment groups: control, bisphenol A, estradiol, anti-estrogen ICI 182,780 (hereinafter ICI), bisphenol A+ICI, and estradiol+ICI. Cell proliferation was measured based on average absorbance using the Cell Counting-8 assay. The cell cycle distribution and apoptotic index were determined by flow cytometry. Telomerase activity was detected by polymerase chain reaction and a telomeric repeat amplification protocol assay. A higher cell density was observed in bisphenol A (P<0.01) and estradiol (P<0.05) groups compared with the control group. Cell numbers in S and G2/M phases after treatment for 48 h were higher (P<0.05), while the apoptotic index was lower (P<0.05) and telomerase activities at 48 and 72 h (P<0.05) were higher in these groups than in the control group. The cell density was also higher in bisphenol A+ICI (P<0.01) and estradiol+ICI (P<0.05) groups compared with the ICI group. Furthermore, cell numbers were increased in S and G2/M phases (P<0.05), while the apoptotic index was lower (P<0.05) and telomerase activities at 48 and 72 h were higher (P<0.05) in these groups than in the ICI group. Therefore, bisphenol A and estradiol promote HepG2 cell proliferation in vitro by inhibition of apoptosis and stimulation of telomerase activity via an estrogen receptor-dependent pathway.

Telomerase Cajal body protein 1 depletion inhibits telomerase trafficking to telomeres and induces G1 cell cycle arrest in A549 cells

Telomerase Cajal body protein 1 (TCAB1) is a telomerase holoenzyme, which is markedly enriched in Cajal bodies (CBs) and facilitates the recruitment of telomerase to CBs in the S phase of the cell cycle. This recruitment is dependent on TCAB1 binding to a telomerase RNA component. The majority of cancer cells are able to grow indefinitely due to telomerase and its mechanism of trafficking to telomeres. In the present study, a certain level of TCAB1 expression in A549 human lung cells was identified and TCAB1 knockdown exhibited a potent antiproliferative effect on these cells, which was coupled with a decrease in the cell density and activity of the cellular enzymes. In addition, TCAB1-depletion was demonstrated to inhibit telomerase trafficking to telomeres in the A549 cells, leading to subsequent G₁ cell cycle arrest without inducing apoptotic cell death. Overall, these observations indicated that TCAB1 may be essential for A549 cell proliferation and cell cycle regulation, and may be a potential candidate for the development of a therapeutic target for lung adenocarcinomas.

The antiretroviral agent saquinavir enhances hTERT expression and telomerase activity in human T leukaemia cells in vitro

BACKGROUND

Saquinavir, a protease inhibitor utilized in HIV infection, shows antitumor activity in various experimental models. In previous studies performed in our laboratory the drug was found to induce a substantial increase of telomerase activity in normal peripheral blood mononuclear cells. Aim of the present investigation was to test whether saquinavir was able to increase telomerase activity and the expression of the catalytic subunit of telomerase, hTERT, in human malignant hematopoietic cells.

METHODS

Human Jurkat CD4+ T cell leukaemia cell line was used throughout the present study. The antiproliferative effect of saquinavir was tested by the MTT assay. Telomerase activity was determined according to the telomeric repeat amplification protocol. The expression of hTERT mRNA was semi-quantitative evaluated by RT-PCR amplification and quantitative Real Time PCR. The binding of the transcription factor c-Myc to its specific E-Box DNA binding-site of hTERT promoter was analyzed by Electophoretic Mobility Shift Assay (EMSA). The amount of c-Myc in cytoplasm and nucleus of leukemia cells was determined by Western Blot analysis, and c-Myc down-regulation was obtained by siRNA transfection.

RESULTS

Saquinavir produced a substantial increase of telomerase activity in Jurkat cells in vitro without increasing but rather reducing target cell proliferation rate. Telomerase up-regulation appeared to be the result of enhanced expression of hTERT. Saquinavir-mediated up-regulation of hTERT gene was the result of the increased binding of proteins to the E-Box sequence of the promoter. Moreover, saquinavir amplified the expression of c-Myc especially in the nuclear cell fraction. The direct influence of saquinavir on this transcription factor was also demonstrated by the antagonistic effect of the drug on siRNA induced c-Myc suppression. Since c-Myc is the main responsible for hTERT transcription, these findings suggest that the main mechanism underlying saquinavir-induced telomerase activation is mediated by c-Myc up-regulation.

CONCLUSIONS

Saquinavir augments hTERT expression while inhibiting leukemic cell growth. Experimental evidences show that this effect is mediated by saquinavir-influenced increase of c-Myc levels. This could have relevance in terms of enhanced hTERT-dependent tumor cell immunogenicity and suggests new paharmacological approaches interfering with c-Myc dependent pathways.

Expression of telomerase & its significance in the diagnosis of pancreatic cancer

Pancreatic cancer has one of the worst prognoses among all types of cancers. The survival rate is less than 5 per cent; this is due to difficulty in diagnosing at an early stage. Despite the improvements in diagnostic imaging techniques such as computed tomography, magnetic resonance imaging, etc., the early diagnosis of pancreatic cancer is still difficult. Alternative methods of diagnosing pancreatic cancer at an early stage are presently been explored. The detection of telomerase activity has been proposed to be a useful tool in the diagnosis of pancreatic cancer. Telomerase is made up of three major parts namely, human telomerase reverse transcriptase, human telomerase and telomerase -associated protein. Several researchers have shown telomerase activity in tissues and fluids of patients with pancreatic and other types of cancers. About 95 per cent telomerase activity has been detected in pancreatic adenocarcinoma. Since telomerase activity is present in a vast majority of human cancers, it might have a role in the diagnosis and treatment of cancer.

Indole-3-carbinol downregulation of telomerase gene expression requires the inhibition of estrogen receptor-alpha and Sp1 transcription factor interactions within the hTERT promoter and mediates the G1 cell cycle arrest of human breast cancer cells

Indole-3-carbinol (I3C), a naturally occurring hydrolysis product of glucobrassicin from cruciferous vegetables such as broccoli, cabbage and Brussels sprouts, is an anticancer phytochemical that triggers complementary sets of antiproliferative pathways to induce a cell cycle arrest of estrogen-responsive MCF7 breast cancer cells. I3C strongly downregulated transcript expression of the catalytic subunit of the human telomerase (hTERT) gene, which correlated with the dose-dependent indole-mediated G(1) cell cycle arrest without altering the transcript levels of the RNA template (hTR) for telomerase elongation. Exogenous expression of hTERT driven by a constitutive promoter prevented the I3C-induced cell cycle arrest and rescued the I3C inhibition of telomerase enzymatic activity and activation of cellular senescence. Time course studies showed that I3C downregulated expression of estrogen receptor-alpha (ERα) and cyclin-dependent kinase-6 transcripts levels (which is regulated through the Sp1 transcription factor) prior to the downregulation of hTERT suggesting a mechanistic link. Chromatin immunoprecipitation assays demonstrated that I3C disrupted endogenous interactions of both ERα and Sp1 with an estrogen response element-Sp1 composite element within the hTERT promoter. I3C inhibited 17β-estradiol stimulated hTERT expression and stimulated the production of threonine-phosphorylated Sp1, which inhibits Sp1-DNA interactions. Exogenous expression of both ERα and Sp1, but not either alone, in MCF7 cells blocked the I3C-mediated downregulation of hTERT expression. These results demonstrate that I3C disrupts the combined ERα- and Sp1-driven transcription of hTERT gene expression, which plays a significant role in the I3C-induced cell cycle arrest of human breast cancer cells.

MYC amplification and TERT expression in breast tumor progression

The complex roles of genomic instability, MYC oncogene amplification, activation of telomerase, and p53 function still remain to be fully described in breast tumors. MYC stimulates the telomerase catalytic subunit, TERT, which interacts with p53. Oncogene MYC amplification analysis was performed on 27 paraffin-embedded breast tumor samples by fluorescence in situ hybridization, selected on the basis of chromosomal instability. TERT immunostaining was performed on a larger group of breast tumor sections. All tumor samples were analyzed for TP53 mutation, genomic index, S-phase fraction, and pathological stages. Amplification of MYC was detected in 16 of 27 tumors (59%) and found to be associated with TNM stages I and II (P = 0.018), genomic index > 1.5 (P = 0.033), and S-phase fraction > 5% (P = 0.020). No association was found between MYC amplification and TERT immunostaining or TP53 mutations. Analysis of TERT in 103 primary breast tumors showed > 50% nuclei immunostaining in 58% of cases. High TERT immunostaining associated with genomic index > 1.5 (P = 0.017), high S-phase fraction (P = 0.056), and TP53 mutations (P = 0.030). No association was found between TERT staining and TNM stages. This study supports early involvement of MYC amplification in breast tumor progression. Both MYC amplification and TERT expression appear to be associated with high genomic instability and proliferation. TERT association with TP53 mutations indicates that TERT activity is downregulated by functional p53 protein in breast tumors.

A tandem repeat of human telomerase reverse transcriptase (hTERT) and risk of breast cancer development and metastasis in Chinese women

Telomerase reactivation, which prevents telomere shortening and maintains cell viability, is crucial for the continued growth or progression of cancer cells. A minisatellite tandem repeat, MNS16A, located in the downstream of the human telomerase reverse transcriptase (hTERT) gene was recently identified and reported to have an effect on hTERT expression and telomerase activity. The aim of this study was to test the hypothesis that the MNS16A variant is associated with risk of breast cancer development and metastasis. We genotyped MNS16A variant in hTERT in a case-control study of 1029 histologically confirmed breast cancer patients and 1107 cancer-free controls in Chinese women. The variant genotypes (302/271, 302/243 and 243/243) of MNS16A were associated with a significantly increased risk of breast cancer [adjusted odds ratio (OR) = 1.50, 95% confidence interval (CI) = 1.15-1.96], compared with the wild-type 302/302 genotype. In stratified analyses, we found that the 302/271 genotype was associated with a significantly increased risk of axillary lymph nodes metastasis (adjusted OR = 2.13, 95% CI = 1.05-4.33) compared with wild-type 302/302 genotype. These findings indicate that the MNS16A variant in the hTERT gene may contribute to the risk of breast cancer development and metastasis in Chinese women.

Pyk2/ERK 1/2 mediate Sp1- and c-Myc-dependent induction of telomerase activity by epidermal growth factor

Epidermal growth factor (EGF) promotes growth of normal ovarian surface as well as malignant ovarian epithelial cells. Further, EGF receptors are present on both normal and malignant ovarian surface epithelial cells and they are often constitutively activated in many cancers. Since telomerase confers cellular immortalization and survival through increased cellular proliferation, we sought to investigate the potential role of EGF to regulate telomerase activity in normal and ovarian cancer cells. While exogenous EGF failed to activate telomerase in normal ovarian surface epithelial cells, in cancer cells we herein report that: exogenous EGF activates telomerase activity and human telomerase reverse transcriptase gene (hTERT) transcription; EGF-induced telomerase activity is ERK 1/2-dependent; EGF targets Sp1 and c-Myc binding sites within the core region of the hTERT promoter; and proline-rich tyrosine kinase 2 (Pyk2) is a key mediator of EGF-mediated telomerase activity. Together, these data show that dysregulation of EGF signaling may promote cancer cell survival through up-regulation of telomerase activity.

Biosensor Techniques Used for Determination of Telomerase Activity in Cancer Cells

Measuring telomerase activity has proven successful for the determination of cancer in malignant somatic cells. Early conventional methods for the detection of telomerase activity include in vitro analysis via a primer extension assay, and the telomeric repeat amplification protocol (TRAP) assay. TRAP incorporates the polymerase chain reaction (PCR) step to increase the sensitivity of a given sample. However, research suggests that the TRAP technique suffers from false negative results, caused by failure of its PCR step. Other limitations of TRAP include the post-PCR steps involving polyacrylamide gel electrophoresis which are time inefficient. Thus, various efforts have been made to eliminate the PCR step of TRAP by using a variety of biosensor detection devices. This review mainly focuses on these alternatives including: optical, electrochemical, magnetic, and nanowire conductive signaling techniques to measure the telomerase activity produced via label free biosensor assay—via biocatalytic labels involving beacons, DNAzyme, ferrocenyl-naphthalene diimides, avidin-alkaline phosphatase and semiconductor quantum dots (QDs). These biosensor techniques are sensitive and provide precise and rapid results in the detection of telomerase activity.

Prediction of lung cancer using volatile biomarkers in breath

BACKGROUND

Normal metabolism generates several volatile organic compounds (VOCs) that are excreted in the breath (e.g. alkanes). In patients with lung cancer, induction of high-risk cytochrome p450 genotypes may accelerate catabolism of these VOCs, so that their altered abundance in breath may provide biomarkers of lung cancer.

METHODS

VOCs in 1.0 L alveolar breath were analyzed in 193 subjects with primary lung cancer and 211 controls with a negative chest CT. Subjects were randomly assigned to a training set or to a prediction set in a 2:1 split. A fuzzy logic model of breath biomarkers of lung cancer was constructed in the training set and then tested in subjects in the prediction set by generating their typicality scores for lung cancer.

RESULTS

Mean typicality scores employing a 16 VOC model were significantly higher in lung cancer patients than in the control group (p<0.0001 in all TNM stages). The model predicted primary lung cancer with 84.6% sensitivity, 80.0% specificity, and 0.88 area under curve (AUC) of the receiver operating characteristic (ROC) curve. Predictive accuracy was similar in TNM stages 1 through 4, and was not affected by current or former tobacco smoking. The predictive model achieved near-maximal performance with six breath VOCs, and was progressively degraded by random classifiers. Predictions with fuzzy logic were consistently superior to multilinear analysis. If applied to a population with 2% prevalence of lung cancer, a screening breath test would have a negative predictive value of 0.985 and a positive predictive value of 0.163 (true positive rate =0.277, false positive rate =0.029).

CONCLUSIONS

A two-minute breath test predicted lung cancer with accuracy comparable to screening CT of chest. The accuracy of the test was not affected by TNM stage of disease or tobacco smoking. Alterations in breath VOCs in lung cancer were consistent with a non-linear pathophysiologic process, such as an off-on switch controlling high-risk cytochrome p450 activity. Further research is needed to determine if detection of lung cancer with this test will reduce mortality.

Telomerase inhibition enhances the response to anticancer drug treatment in human breast cancer cells

Breast cancer is the most common malignancy among women. Current therapies for breast tumors are based on the use of chemotherapeutic drugs that are quite toxic for the patients and often result in resistance. Telomerase is up-regulated in 95% of breast carcinomas but not in adjacent normal tissues. Therefore, it represents a very promising target for anticancer therapies. Unfortunately, the antiproliferative effects of telomerase inhibition require extensive telomere shortening before they are fully present. Combining telomerase inhibition with common chemotherapeutic drugs can be used to reduce this lag phase and induce tumor cell death more effectively. Few studies have analyzed the effects of telomerase inhibition in combination with anticancer drugs in breast cancer cells. In this study, we inhibited telomerase activity in two breast cancer cell lines using a dominant-negative human telomerase reverse transcriptase and analyzed cell viability after treatment with different anticancer compounds. We found that dominant-negative human telomerase reverse transcriptase efficiently inhibits telomerase activity and causes telomere shortening over time. Moreover, cells in which telomerase was suppressed were more sensitive to anticancer agents independently of their mechanism of action and this sensitization was dependent on the presence of shorter telomeres. Altogether, our data show that blocking telomere length maintenance in combination with anticancer drugs can be used as an effective way to induce death of breast cancer cells.

Elevation of telomerase activity positively correlates to poor prognosis of patients with non-small cell lung cancer

Increased telomerase activity has been found in various types of human malignancies, including lung cancer. However, the correlation between the level of telomerase activity and the clinical characteristics of lung cancer patients remains unclear. The levels of telomerase activity in lung cancer specimens and adjacent non-neoplastic tissues obtained from 68 patients who underwent surgery were measured by using a non-radioactive quantitative method. Clinical and pathologic parameters were evaluated with respect to the level of telomerase activity. Prominent telomerase activity was detected in 58 (85.3%) lung cancer tissues and 21 (30.9%) adjacent non-neoplastic tissues. There was a trend of increase in relative telomerase activity in regard to the advanced pathological stage, and lymph node metastasis. Using Cox regression analysis, we found that every 100 unit of increase in relative telomerase activity was associated with an increase in the hazard ratio of death by 13% after controlling for other variables such as age, gender, and stage (Hazard ratio=1.13; 95% CI: 1.03-1.23, P=0.006). For patients with stage I disease, an increase of every 100unit of relative telomerase activity was associated with an even higher increase of 33% in the hazard ratio of death (Hazard ratio=1.33; 95% CI: 1.07-1.65, P=0.011) and a 16% increase in the hazard of disease recurrence (Hazard ratio=1.16, 95% CI: 1.01-1.33, P=0.032). The level of telomerase activity is positively correlated with the risk of recurrence and mortality of lung cancer. The level of telomerase activity would predict the prognosis of lung cancer patients.

The role of telomeres and telomerase in the pathology of human cancer and aging

Cellular senescence, the state of permanent growth arrest, is the inevitable fate of replicating normal somatic cells. Postulated to underlie this finite replicative span is the physiology of telomeres, which constitute the ends of chromosomes. The repetitive sequences of these DNA-protein complexes progressively shorten with each mitosis. When the critical length is bridged, telomeres trigger DNA repair and cell cycle checkpoint mechanisms that result in chromosomal fusions, cell cycle arrest, senescence and/or apoptosis. Should senescence be bypassed at such time, continued cell divisions in the face of dysfunctional telomeres and activated DNA repair machinery can result in the genomic instability favourable for oncogenesis. The longevity and malignant progression of the thus transformed cell requires coincident telomerase expression or other means to negate the constitutional telomeric loss. Practically then, telomeres and telomerase may represent plausible prognostic and screening cancer markers. Furthermore, if the argument is extended, with assumptions that telomeric attrition is indeed the basis of cellular senescence and that accumulation of the latter equates to aging at the organismal level, then telomeres may well explain the increased incidence of cancer with human aging.

Detection of telomerase activity by the TRAP assay and its variants and alternatives

Telomerase activity is closely connected to problems of cellular immortality, proliferative capacity, differentiation, cancer and aging. Correspondingly, techniques for its detection have been essential for progress in telomere biology and are of still increasing importance in molecular diagnostics and therapy of cancer. This article reviews the development of the telomere repeat amplification protocol (TRAP) and its various modifications as the most widespread assay to detect and measure telomerase activity. Alternative possibilities of telomerase activity detection are also discussed which make it possible to omit the PCR-mediated amplification of telomerase products. These approaches are based on recent advances in highly sensitive detection systems.

Telomerase activity in prognostic histopathologic features of melanoma

BACKGROUND

Telomerase activity (TA) is believed to play a role in the regulation of senescence and to limit the number of cell divisions. The deregulation of telomerase appears to contribute to oncogenesis and the formation of immortal cell lines. As a result, it is believed that it could be used as a prognostic marker in melanoma.

METHODS

TA was assayed by the polymerase chain reaction PCR-ELISA-based telomeric repeat amplification protocol (TRAP assay). One hundred and eight samples were distributed in four histological groups: 30 samples from primary cutaneous melanomas, 24 from peritumoural skin sites, 28 from benign melanocytic lesions, and 26 from normal skin sites as a control.

RESULTS

TA was different among the four tested groups (Kruskall-Wallis test p<0.001), and increasing values of TA were observed progressing from normal skin to benign and then to malignant lesions. Among melanoma samples, there was a significant association between TA and ulceration (p=0.025), TA and vascular invasion (p=0.018) and TA and mitotic rate (p=0.029) (Mann-Whitney test). A linear regression analysis showed significant associations between the increase of TA with Breslow thickness (p=0.004) and the presence of satellites (p=0.002).

CONCLUSIONS

We observed that TA had increased from control skin to peritumoural skin, and then to benign melanocytic lesions and finally to melanoma, suggesting tumour progression. TA showed higher values in the presence of some important histopathologic parameters related to poor prognosis in cutaneous melanoma such as ulceration, vascular invasion, satellites, high rates of mitosis, and in thicker tumours.

Effects of a novel telomerase inhibitor, GRN163L, in human breast cancer

Telomerase activity is undetectable in most normal tissues but the vast majorities of cancers express active telomerase. Therefore, telomerase serves as an attractive target for the treatment of cancers. GRN163L is a lipid-modified oligonucleotide N3'-->P5' thio-phosphoramidate complementary to the RNA template region of human telomerase. The anti-telomerase activity of GRN163L was evaluated using MDA-MB-231 and MDA-MB-435 human breast adenocarcinoma cell lines. Twice weekly administration of GRN163L resulted in the inhibition of telomerase activity and progressive telomere shortening. Cells treated with GRN163L did not demonstrate decreased cell proliferation for up to 2 weeks. However, after additional treatment, cell proliferation gradually decreased in GRN163L-treated cells compared to untreated or mismatch control oligoncleotide treated cells. Furthermore, anti-tumorigenic effects were seen in cells treated with GRN163L, as cells lose their ability to form colonies in soft agar and were unable to form colonies in the clonal efficiency assay upon incubation with GRN163L. Moreover, breast cancer cells that were treated with GRN163L for only 1 week prior to plating in invasion chambers, and when bulk telomere are still long, exhibit significantly diminished invasive potential. These results reveal critical information regarding the effectiveness of GRN163L as a potential therapeutic agent for the treatment of human breast cancer.

Differential Expression of Full-length Telomerase Reverse Transcriptase mRNA and Telomerase Activity between Normal and Malignant Renal Tissues

Activation of telomerase, a key event during immortalization and malignant transformation, requires expression of the telomerase reverse transcriptase (hTERT). Consistently, lack of telomerase activity and hTERT expression occurs in most normal human somatic cells. However, it has been observed that both normal and cancerous renal tissues express hTERT whereas only the latter exhibits telomerase activity. The mechanism underlying the dissociation between hTERT expression and telomerase activity is unclear. In the present study, we examined telomerase activity and alternative splicing of hTERT transcripts in renal cell carcinoma (RCC) specimens and adjacent normal tissues from 33 patients with RCC. Telomerase activity was detectable in 27 of 33 (82%) RCC samples but none in their normal counterparts. Thirty-two of 33 tumors expressed overall hTERT mRNA and 27 of them contained full-length hTERT transcripts, all with telomerase activity. Although 42% (14 of 33) of normal renal samples expressed hTERT mRNA, none of them had full-length hTERT transcripts, coinciding with lack of telomerase activity. The presence of full-length hTERT mRNA and telomerase activity was significantly associated with c-MYC induction. In tumors, absence of full-length hTERT mRNA or telomerase activity defines a subgroup of nonmetastatic, early-stage RCCs. Taken together, telomerase repression in normal renal tissues is attributed to the absence of full-length hTERT transcripts, whereas telomerase activation is achieved via induction of or switch to expression of full-length hTERT mRNA during the oncogenic process of kidneys, and associated with aggressive RCCs.

Telomerase reverse transcriptase subunit expression is associated with chondrosarcoma malignancy

Expression of the telomerase reverse transcriptase subunit telomerase reverse transcriptase gene is associated with most human malignancies. Because telomerase reverse transcriptase is rarely expressed in normal tissue, its presence in pathologic specimens is considered a marker of transformed cells. Moreover, high levels of expression have been correlated with poor prognosis in many cancers. Although telomerase activity has been found in chondrosarcomas, its prognostic significance in these malignant cartilage tumors is unknown. Malignancy in cartilage-derived tumors is assessed routinely by histomorphologic grading, but even well differentiated, low-grade lesions can metastasize. This unpredictable behavior greatly complicates the clinical treatment of cartilage tumors, making better prognostic indicators desirable. To address this issue we used immunohistochemistry to compare telomerase reverse transcriptase expression in a collection of 61 tumors consisting of malignant chondrosarcomas of varying grade and benign enchondromas. Associated case histories were reviewed to test the hypothesis that telomerase reverse transcriptase expression levels correlated with subsequent tumor recurrence. We found that the relative abundance of telomerase reverse transcriptase-expressing cells correlated significantly with grade and recurrence. These findings indicate that telomerase reverse transcriptase immunostaining may be a useful adjunct to the conventional three-level grading system.

Telomerase in breast cancer: a critical evaluation

Human chromosomes have highly specialized structures at their ends termed telomeres, repetitive, non-coding DNA sequences (5'-TTAGGG-3'), ranging in size from 5 to 20 kb in human cells. These highly specialized structures prevent chromosome ends from being recognized as double-strand DNA breaks, and they also provide protection from destabilizing agents. The mechanism for maintaining telomere integrity is controlled by telomerase, a ribonucleoprotein enzyme that specifically restores telomere sequences lost during replication by using an intrinsic RNA component as a template for polymerization. Telomerase has two core functional components required for its activity: the catalytic subunit of human telomerase reverse transcriptase (hTERT) and a telomerase RNA template (hTR). Telomerase is activated in the majority of immortal cell lines in culture and in most malignant tumors. This review outlines our current understanding of telomerase in breast cancer development and critically evaluates potential utilities in diagnosis, prognosis, and therapy.

Telomere shortening occurs early during breast tumorigenesis: a cause of chromosome destabilization underlying malignant transformation?

Chromosomal instability appears early during breast carcinogenesis and is considered a major driving force in malignant transformation. While current evidence suggests that centrosomal and mitotic checkpoint defects may, in large part, account for numerical chromosomal abnormalities, the mechanisms underlying structural chromosomal abnormalities remain largely unknown. Telomeres stabilize and protect chromosomal termini, but shorten due to cell division and oxidative damage. Moderate telomere shortening signals a tumor suppressive growth arrest in normal cells. Critically short telomeres, in the setting of abrogated DNA damage checkpoints, cause chromosomal instability due to end-to-end chromosomal fusions, subsequent breakage, and rearrangement, resulting in an increased cancer incidence in animal models. Recent results from high resolution in situ telomere length assessment in human breast tissues indicate that significant telomere shortening is prevalent in preinvasive breast lesions (DCIS), as well as focal areas of histologically normal epithelium from which breast carcinoma is thought to arise. Telomere shortening is therefore a strong candidate for the cause of structural chromosome defects that contribute to breast cancer development.

Trisubstituted acridine derivatives as potent and selective telomerase inhibitors

The synthesis and evaluation for telomerase-inhibitory and quadruplex DNA binding properties of three related series of rationally designed trisubstituted acridine derivatives are described. These are substituted on the acridine ring at the 2,6,9; 2,7,9; and 3,6,9 positions. The ability of several of the most potent compounds to interact with and stabilize an intramolecular G-quadruplex DNA was evaluated by surface plasmon resonance methods, and affinities were found to correlate with potency in a telomerase assay. The interactions of a number of compounds with a parallel quadruplex DNA structure were simulated by molecular modeling methods. The calculated interaction energies were compared with telomerase activity and showed generally consistent correlations between quadruplex affinity and telomerase inhibition. These data support a model for the action of these compounds that involves the stabilization of intermediate quadruplex structures that inhibit the elongation of telomeric DNA by telomerase in tumor cells.

Telomerase activity and cell apoptosis in colon cancer cell by human telomerase reverse transcriptase gene antisense oligodeoxynucleotide

AIM: To evaluate the effect of human telomerase reverse transcriptase (hTERT) gene antisense oligodeoxynucleotide (As-ODN) on telomerase activity and cell apoptosis in colon cancer cell line SW480.

METHODS: As-ODN was transfected into cells SW480 by liposomal transfection. Cultured cells were divided into three groups: ASODN (5’GGAGCGCGCGGCATCGCGGG-3’), sense oligodeoxynucleotide (5’-CCCGCGATGCCGCGCGCTCC-3’, S-ODN) and control. The concentration of oligodeoxynucleotide and lipsome was 10 μmol/L and 16 mg/L, respectively. The activity of telomerase was examined by telomeric repeat amplification protocol (TRAP)-enzyme-linked immunosorbent assay (ELISA), and cell apoptosis was observed by morphology and flow cytometry in each group.

RESULTS: Telomerase activity began to be down-regulated or inhibited when cells SW480 were treated with As-ODN for 72 h, and cell apoptosis was induced.

CONCLUSION: It is suggested that hTERT As-ODN might specially inhibit the activity of telomerase in colon cancer cells and it is further proved that the hTERT gene has a significant correlation with telomerase activity. Further evidence is needed to prove whether hTERT As-ODN is a potential tool for the treatment of colon cancer.

Telomerase activity in juxtacortical and conventional high-grade osteosarcomas: correlation with grade, proliferative activity and clinical response to chemotherapy

Seven samples from seven patients with juxtacortical osteosarcomas, and 27 samples from 19 patients with conventional high-grade osteosarcomas were investigated for a possible correlation between telomerase activity and clinicopathological features such as age, sex, and response to chemotherapy. Of seven juxtacortical osteosarcomas, telomerase activity was weakly positive in three parosteal osteosarcomas, and highly positive in one parosteal osteosarcoma. In contrast, of 27 conventional high-grade osteosarcomas, telomerase activity was weakly positive in eight tumors and highly positive in three. Of all samples, 44.1% of the osteosarcomas showed telomerase activity (57.1% of juxtacortical and 40.7% of conventional osteosarcomas). The majority of poor responders to chemotherapy showed no telomerase activity (nine of 11), whereas five of seven good responders showed strong or weak telomerase activity. There was a significant correlation between telomerase activity and the response to chemotherapy (P<0.05). Telomerase activity was not correlated with MIB-1 proliferation index, age at the time of surgery, or sex. These findings suggest that telomerase activation occurs early in the oncogenesis of osteoblastic tumors without having an effect on the progression of these tumors. In malignant osteoblastic tumors, the biological significance of telomerase activation is different from that described for most epithelial cancers.

Increased gap junctional intercellular communication is directly related to the anti-tumor effect of all-trans-retinoic acid plus tamoxifen in a human mammary cancer cell line

Additive effects against tumor cells might be achieved by combining anti-neoplastic agents directed against one or more altered mechanisms in cancer. We investigated the participation of gap junctional intercellular communication (GJIC), which is commonly dysfunctional in tumor cells as a possible mediating mechanism of the effect of all-trans-retinoic acid (RA) and tamoxifen (Tx) in MCF-7 human breast cancer cell lines. The combination of RA + Tx stimulated GJIC in approximately 53 +/- 3% of MCF-7 cells as early as after 6 h of treatment remaining communicated through 144 h of culture. The GJIC enhancement occurred along with immunolocalization of Cx26 and 43 at the membrane of contacting cells and correlated with higher protein levels. Cx40 immunoreactive plaques were detected at cell-to-cell contacts during 48 h of RA + Tx treatment that did not involve higher protein expression, to the contrary, a downregulation occurred after 72 h of treatment. Cell proliferation inhibition upon RA + Tx exposure was observed with optimal effects at 96-120 h of culture with an accumulation of cells primarily in G2/M and G0/G1 cell cycle boundaries. An enhancement of the pre-existing E-cadherin levels was observed after drug exposure along with a downregulation of Bcl-2 and C-myc protein levels and a reduction of telomerase activity, suggesting partial tumor phenotype reversion. Blockage of the RA + Tx-induced GJIC with 18-beta-glycyrrhetinic acid (beta-Gly) prevented in 34% the inhibition of MCF-7 proliferation and the E-cadherin increment in 30% at 96 h of culture. GJIC blockage did not alter the downregulation of Bcl-2, c-Myc, or telomerase activity induced by RA + Tx. Our results showed the participation of GJIC as a mediator mechanism of the combined action of RA and Tx in MCF-7 cells. The chemopreventive modulation of GJIC might represent an approachable alternative for the improvement of cancer therapy.

Telomeres, telomerase, and telomerase inhibition: clinical implications for cancer

Telomeres are located at the ends of eukaryotic chromosomes. The enzyme telomerase synthesized them, and they are responsible for maintaining the lengths of chromosomes. Absence of telomerase is associated with telomere shortening and aging of somatic cells, but high telomerase activity is observed in over 90% of human cancer cells. Although the disappearance of telomerase with aging is considered a natural defense against development of cancer, it is not known what triggers the reappearance of telomerase in cancer cells. Telomerase activity is directly correlated with the expression of its active catalytic component, the human telomerase reverse transcriptase (hTERT), which is controlled primarily at the level of transcription. An earlier paper discussed the relationship of telomerase with aging. In this article, the contemporary literature is reviewed to explore the associations between telomerase, telomerase inhibition, and cancer. Because most cancers occur in old age, with the aging of the population, the number of people suffering from cancer is expected to increase in the coming decades. It is not known what roles telomerase and hTERT play in the complex relationship between aging and cancer. Data from experimental studies suggest that telomerase assay could potentially play a role in the diagnosis and prognosis of cancers. There is also evidence that telomerase inhibitors might be used as anticancer agents. As the knowledge of the relationships between telomerase and cancer and between telomerase and aging advances, it is hoped that more about the interacting relationships between telomerase, aging, and cancer will be learned.

Chemopreventive agents induce a senescence-like phenotype in rat mammary tumours

Terminal replicative senescence (TRS) is a physiological process associated with terminal differentiation, shortening of the telomere, and lack of proliferative activity. Immortalised and tumour cells have lost their differentiation potential and the ability to develop a senescence phenotype. Recently, others and we [11] have observed that some antitumour agents and radiation induce a senescence-like phenotype (SLP) in human immortalized and tumour cell lines. The main purpose of this study was to identify senescence-like cells (SLC) in mammary tumours of rats and assess whether chemopreventive agents that have been used for the prevention and/or treatment of breast cancer can induce a SLP in tumour cells. Sprague-Dawley rats with N-methyl-N-nitrosourea (MNU)-induced mammary tumours were randomised and treated with tamoxifen, vorozole, 4-(hydroxyphenyl)retinamide (4-HPR), or 9-cis-retinoic acid (9cRA). The SLC in mammary tumours were identified and characterised by: (a) SA-beta-Gal staining method, which has been considered specific for human cells in TRS (b) staining for lipofuscin, which, although not specific, accumulates in the cytoplasm of cells in senescence; (c) lack of 5-Bromodeoxyuridine (BrdU) labelling after continuous (7 days) infusion of BrdU via osmotic pumps; (d) 90 degrees side light scatter (9OLS) as evaluated by flow cytometry; and (e) decreased telomerase activity. We found that in control tumours, SA-beta-Gal-positive cells were rare (below 1.0%) among the tumour cells, stroma fibroblast, myoepithelial and endothelial cells. SA-beta-Gal-positive cells increased significantly in the tumours treated with chemopreventive agents and this was associated with a lack of proliferative activity, increased cell granularity, lipofuscin accumulation, and decreased telomerase activity. Thus, in this study we provide for the first time evidence that cells in replicative senescence are present in mammary tumours of rats and that chemopreventive agents can suppress tumor growth by a novel cellular mechanism, inducing a SLP in the tumor cells.

Telomerase as a prognostic marker in breast cancer: high-throughput tissue microarray analysis of hTERT and hTR

Telomerase activity (TA) has been shown to correlate with poor clinical outcome in various tumour entities, indicating that tumours expressing this enzyme may be more aggressive and that TA may be a useful prognostic marker. For breast cancer, however, TA is a controversial prognostic marker; whereas some studies suggest an association between TA and disease outcome, others do not find this association. This study used tissue microarrays (breast carcinoma prognosis arrays) containing 611 samples (each 0.6 mm in diameter) from the tumour centre of paraffin-embedded breast carcinomas to analyse the catalytic subunit of telomerase, human telomerase reverse-transcriptase (hTERT), and the internal RNA component (hTR), which are the core components of the telomerase holoenzyme complex. hTERT protein expression was obtained by immunohistochemistry (human anti-telomerase antibody Ab-2, Calbiochem), and hTR RNA was measured by radioactive in situ hybridization. hTERT and hTR expression were determined semi-quantitatively and graded (scores 1-4). Clinical data, such as histological subtype, pT stage, tumour diameter, pN stage, BRE grade, tumour-specific survival (in months), patient's age and others, were available for statistical analysis. A statistically significant correlation was found between tumour-specific survival (overall survival) and hTERT expression (p < 0.0001) or hTR expression (p = 0.00110). Tumours with higher scores (scores 3, 4) for hTR and/or hTERT were associated with a worse prognosis. In multivariate analysis, hTERT expression was an independent prognostic factor. Previous studies, focusing on analysis of TA in smaller numbers of fresh-frozen breast carcinomas by the TRAP assay, gave controversial results with respect to TA as a prognostic marker. Using tissue microarrays from 611 breast carcinomas, this study has demonstrated that increased expression levels of the telomerase core components, hTERT and hTR, are associated with lower overall survival. These findings suggest that TA should be included in future validation studies as a prognostic marker in breast cancer.

Telomerase activity as a marker for malignancy in feline tissues

OBJECTIVE

To establish the diagnostic significance of the telomeric repeat amplification protocol (TRAP) assay in detecting feline malignancies.

SAMPLE POPULATION

Solid tissue specimens collected from 33 client-owned cats undergoing diagnostic or therapeutic procedures at the University of Illinois Veterinary Medical Teaching Hospital between July 1997 and September 1999 and an additional 20 tissue samples were collected from 3 clinically normal control cats euthanatized at the conclusion of an unrelated study.

PROCEDURE

The TRAP assay was used for detection of telomerase activity. Each result was compared to its respective histopathologic diagnosis.

RESULTS

Twenty-nine of 31 malignant and 1 of 22 benign or normal tissue samples had telomerase activity, indicating 94% sensitivity and 95% specificity of the TRAP assay in our laboratory.

CONCLUSIONS AND CLINICAL RELEVANCE

The diagnostic significance of telomerase activity has been demonstrated in humans and recently in dogs by our laboratory. We tested feline samples to determine whether similar patterns of telomerase activity exist. On the basis of our results, the TRAP assay may be clinically useful in providing a rapid diagnosis of malignancy in cats. The telomerase enzyme may also serve as a therapeutic target in feline tumors.

Telomerase activity in periampullary tumors correlates with aggressive malignancy

OBJECTIVE

To determine the presence of telomerase activity in a variety of periampullary malignancies and pancreatic diseases and quantify its activity to establish any association with the stage or aggressiveness of malignancy.

SUMMARY BACKGROUND DATA

Progressive shortening of telomeres, repetitive DNA sequences at the ends of chromosomes, plays a role in cell senescence. Telomerase catalyzes conservation of telomeric repeats and may promote cell immortality and hence malignancy. It is absent in normal tissues but upregulated in more than 80% of cancers.

METHODS

Fresh specimens of 62 periampullary tumors were snap-frozen in liquid nitrogen and adjacent tissue was formalin-fixed for histopathology. The telomerase repeat amplification protocol (TRAP) was used to obtain telomerase DNA products. These were separated with gel electrophoresis, stained with SYBR green, and quantified by densitometry. Findings were confirmed with a fluorometric TRAP assay in which fluorescent primers specific for telomerase were selectively amplified in its presence.

RESULTS

Telomerase activity was upregulated in 26 of 33 periampullary malignancies (79%): 17 of 21 pancreatic adenocarcinomas (81%), 2 of 2 cholangiocarcinomas, 2 of 2 duodenal carcinomas, and 5 of 8 ampullary carcinomas (63%). Poorly differentiated periampullary tumors had significantly higher telomerase activity than well-differentiated tumors, and tumors larger than 2 cm had significantly higher telomerase activity than those 2 cm or smaller. Pancreatic ductal adenocarcinomas with lymph node metastases had significantly greater activity than node-negative cancers. Two of 11 intraductal papillary mucinous tumors were positive for telomerase activity, but only in foci of invasive carcinoma. Chronic pancreatitis (n = 7), serous cystadenomas (n = 5), benign mucinous cystic neoplasms (n = 4), neuroendocrine cancer (n = 1), and acinar cell carcinoma (n = 1) had no detectable telomerase activity.

CONCLUSION

Telomerase activity is common in periampullary carcinomas. The magnitude of activity correlates with aggressiveness in pancreatic adenocarcinoma and may prove useful as a molecular index for biologic staging.

Telomerase in endocrine and endocrine-dependent tumors

Telomerase, the ribonucleoprotein enzyme that elongates chromosomal ends, or telomeres, is repressed in most normal somatic cells but reactivated in transformed cells to compensate for the progressive erosion of the telomeres during cell divisions. In accordance with this hypothesis, the presence of telomerase activity has been reported in more than 90% of human cancers, whereas most normal tissues or benign tumors contain low or undetectable telomerase activity. Reactivation of telomerase has also been widely reported in endocrine neoplasms and in hormone-related cancers. In the present study, we review the most recent publications on telomerase in these types of tumors. The hormonal regulation of telomerase activity and the possible strategies for cancer therapy based on the inhibition of telomerase has also been discussed.

Ultraviolet irradiation- and dimethyl sulfoxide-induced telomerase activity in ovarian epithelial cell lines

Information about telomerase regulation is incomplete, especially since various studies suggest complexity in telomerase regulation. Given the important association between telomerase and cancer, it is imperative to design and develop a model system in which telomerase activity can be regulated and studied. We employed ultraviolet (UV) radiation or dimethyl sulfoxide (DMSO) to transiently induce telomerase activity in a telomerase-positive cell line and, most importantly, in a telomerase-negative cell line. UV- or DMSO-induced telomerase activity was associated with increased hTRT, but not hTR, mRNA transcription in the telomerase-negative cells. However, no changes in hTRT or hTR mRNA transcription were noted with UV- or DMSO-induced telomerase activity in the telomerase-positive cells. Inhibition of protein synthesis or the phosphotidyl inositol 3-kinase (PI3K) pathway suppressed telomerase induction and/or activity in all cell lines examined, suggesting telomerase activity was dependent on protein synthesis and PI3K-mediated phosphorylation. Furthermore, enhanced telomerase activity was limited to UV and DMSO, since a variety of chemotherapeutic agents failed to induce telomerase activity. Therefore, our data provide a useful culture model system to study telomerase regulation in telomerase-negative and -positive cell lines and from which to obtain information about telomerase as a target for cancer intervention.

Presence of telomerase activity in different musculoskeletal tumor histotypes and correlation with aggressiveness

Telomerase is a ribonucleoprotein enzyme that maintains the protective structures at the ends of eukaryotic chromosomes, called telomeres. Telomerase activity was observed and correlated with aggressiveness in different neoplasms such as breast, prostate, blood and brain cancers, among others. To investigate whether telomerase activity is an index of aggressiveness in bone and soft tissue lesions of the extremities, 66 biopsy samples from our tissue bank were studied. These samples included 43 high-grade sarcomas, 9 aggressive benign tumors and 14 totally benign lesions. The samples were collected from patients homogeneously treated at the Rizzoli Orthopaedic Institute with a follow-up ranging from 4 to 11 years (median, 7 years). A non-radioactive polymerase chain reaction-based enzyme-linked immunosorbent assay was used for the study. All tumors investigated were positive for telomerase activity. Among benign lesions, only 2 aneurysmal bone cysts showed higher telomerase activity than the cut-off point, whereas all the other benign lesions had lower activity. Our results indicate that high levels of telomerase activity in bone and soft tissue lesions correlate with more aggressive clinical behavior in patients treated with surgery alone. An interesting inverse correlation between telomerase activity and occurrence of pulmonary metastasis was detected in osteosarcoma patients treated with chemotherapy. A parallel increase of telomerase activity and malignancy was observed in the adipose and cartilagineous tissue lesions. Our data suggest that telomerase activity could be considered a marker of tumor aggressiveness for bone and soft tissue lesions. The results obtained in osteosarcoma samples suggest that low levels of telomerase activity may be predictive of the prognosis and should influence the therapeutic protocol.

Telomerase, immortality and cancer

Replication of eukaryotic linear chromosomes is incomplete and leaves terminal gaps. The evolutionary widely distributed solution to this "end replication" is twofold: chromosome ends are capped with telomeres, bearing multiple copies of redundant telomeric sequences, and the telomerase enzyme can add (lost) telomeric repeats. Telomerase in humans, as in all mammals, is ubiquitous in all embryonic tissues. In adults, telomerase remains active in germs cells, and, although down-regulated in most somatic tissues, telomerase is active in regenerative tissues and notably, in tumor cells. Telomerase activity is linked to cellular proliferation, and its activation seems to be a mandatory step in carcinogenesis. In contrast to mammals, indeterminately growing multicellular organisms, like fish and crustaceae, maintain unlimited growth potential or 'immortality' in all somatic tissues throughout their entire life. Also this cell immortalization is brought about by maintaining telomerase expression. Disease prognosis for human tumors includes evaluation of cell proliferation, based on the detection of proliferation markers with monoclonal antibodies. The significance of the classical marker Ki-67, and of a novel marker repp-86 are compared with semiquantitative telomerase assays. For tumor therapy, telomerase inhibitors are attractive tools. Results with telomerase knock-out mice have revealed promise, but also risk of this approach. On the other side, telomerase stimulation is attractive for expanding the potential of cellular proliferation in vitro, with possible applications for transplantation of in vitro expanded human cells, for immortalizing primary human cells as improved tissue models, and for the isolation of otherwise intractable products, like genuine human monoclonal antibodies.

Telomerase activity in prostate sextant needle cores from radical prostatectomy specimens

Human telomerase acts to maintain functioning telomeres, which are required for cellular immortality and very likely for cancer progression. Telomerase activity is present in about 85% of human cancers tested, but it has not been found in most human somatic cells and tissues. We used the Telomeric Repeat Amplification Protocol to perform telomerase activity assays on sextant needle core samples obtained from 35 freshly excised radical retropubic prostatectomy specimens. Similar assays were done on prostatic tissues obtained by means of other urologic procedures from 8 patients without prostate cancer. Telomerase activity was found in one or more specimens from 32 of 35 prostate cancer patients (91%), but was not detectable in all biopsy specimens from 7 of 8 cancer-free patients (88%). Further analysis showed that cancers more poorly differentiated, with higher Gleason scores, were always associated with a higher rate of telomerase detection and stronger telomerase activity. Moreover, comparison of telomerase activity in needle core samples with the volume of cancer in surrounding tissue as observed on corresponding histologic slides showed that stronger activity was positively correlated with a higher cancer volume. Prognostic indicators of prostate cancer and the expression of telomerase appear to be linked. The presence of telomerase activity in prostate tissue may aid in the detection of prostate cancer and produce additional prognostic information.

Telomerase in relation to clinicopathologic prognostic factors and survival in cervical cancer

We investigated, in cervical cancer, the relation between telomerase activity, telomerase RNA (hTR) and mRNA of the catalytic subunit of telomerase, hTERT, with "classic" clinicopathological factors as well as survival. Frozen specimens were obtained from 107 consecutive patients with cervical cancer, treated with surgery or radiotherapy with or without chemotherapy. Telomerase activity was determined with fluorescence-based TRAP and hTR and hTERT with semi-quantitative RT-PCR. Eight normal cervical specimens served as controls. Analysis of prognostic factors and survival was limited to early-stage patients, treated primarily with radical hysterectomy. Telomerase activity was not detected in normal cervices and was present in 85 of 107 (79%) cervical cancers (p < 0.001). hTR was detected in all normal cervices and cervical cancers, while hTERT mRNA was detected in 1 of 8 (13%) normal cervices and in 83 of 104 (80%) cervical cancers (p < 0.001). In contrast to semi-quantitative hTR expression levels, semi-quantitative hTERT mRNA levels were related to telomerase activity levels (p < 0.01). In all patients, telomerase activity levels were related to differentiation grade (p < 0.05) but not to stage and histotype. In early-stage patients, telomerase activity, hTR and hTERT were not related to tumor volume, vascular invasion or presence of metastatic lymph nodes. Tumor volume, vascular invasion and presence of metastatic lymph nodes were related to (progression-free) survival, while telomerase activity and its subunits were not. Frequent up-regulation of telomerase activity and hTERT mRNA is especially observed in cervical cancers, while hTR is also detected in normal cervices. Telomerase is not applicable as a prognostic factor in early-stage cervical cancer patients.

Telomerase activity of cultured human pancreatic carcinoma cell lines correlates with their potential for migration and invasion

BACKGROUND

Despite the recent clinical finding that high telomerase activity is an unfavorable prognostic marker for various human malignant tumors, there has been no experimental evidence supporting the link between telomerase and tumor aggressiveness. In the current investigation, the authors examined the relation between telomerase activity and potential for biologic aggressiveness in human pancreatic carcinoma cells.

METHODS

Telomerase activity was measured in a poorly metastatic cell line HPC-3 and its highly metastatic variant HPC-3H4, as well as in many pancreatic carcinoma cell lines. Aggressive behavior of cancer cells was assessed by in vitro migration and invasion assay.

RESULTS

Compared with parental HPC-3, HPC-3H4 displayed higher telomerase activity, which was associated with a scattered phenotype and enhanced migration activity. Furthermore, the authors found that relative telomerase levels correlated well with both motility (P = 0.0041) and invasion (P = 0.0114) in 13 pancreatic carcinoma cell lines. There was, however, no significant association between telomerase activity and cell proliferation. When telomerase activity of KP-1N cells was inhibited by transfection with antisense oligonucleotides, their motility and invasion rates were significantly decreased.

CONCLUSIONS

The authors concluded that the magnitude of telomerase activation may reflect the potential for aggressive behavior within cancer cells. These findings support the clinical utility of telomerase activity as a prognostic indicator. Their results also suggest a therapeutic potential for telomerase inhibitors to prevent tumor invasion and possibly metastasis.