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

Subcellular localization of hTERT in breast cancer: insights into its tumorigenesis and drug resistance mechanisms in HER2-immunopositive breast cancer

Human telomerase reverse transcriptase (hTERT) is highly expressed in various cancers, including breast cancer. Although telomere elongation is an essential role for hTERT, the nuclear export after oxdative stress has also been shown in several cancer cell lines and is associated with drug-resistance in vitro. As only a few reports focused on the subcellular localization of hTERT in clinical specimens, we performed immunohistochemistry (IHC) and analyzed the correlation between intracellular hTERT expression and the clinicopathological characteristics to identify the clinical significance of hTERT subcellular expression in breast cancers. 144 invasive breast cancers classified by IHC subtype without primary systemic therapy (PST), were selected from a surgical resection cohort and were immunostained for hTERT, p-STAT3, p-AKT and p-ERK. The nuclear and/or cytoplasmic staining intensity and proportion of hTERT were scored and compared with clinicopathological parameters. The nuclear hTERT expression was significantly correlated with HER2 expression (p = 0.00156), and the scores were significantly correlated with p-STAT3 and p-AKT expression scores (r = 0.532, p = 0.000587 and r = 0.345, p = 0.0339, respectively) in the HER2-immunopositive breast cancer including luminal-HER2 and HER2 subtypes. Furthermore, hTERT was expressed more in cytoplasm in the specimens after PST than those before PST, and the score tended to be negatively correlated with tumor shrinkage rate in HER2 subtype (r = -0.593, p = 0.0705). These results suggest that nuclear and/or cytoplasmic hTERT may play a different role before and after PST including the tumorigenesis and drug-resistance in breast cancer. Suppression of cytoplasmic hTERT expression may lead to more effective strategy for drug-resistant HER2 subtype in breast cancer.

THOR is a targetable epigenetic biomarker with clinical implications in breast cancer

BACKGROUND

Breast cancer (BC) is the most frequently diagnosed cancer and a leading cause of death among women worldwide. Early BC is potentially curable, but the mortality rates still observed among BC patients demonstrate the urgent need of novel and more effective diagnostic and therapeutic options. Limitless self-renewal is a hallmark of cancer, governed by telomere maintenance. In around 95% of BC cases, this process is achieved by telomerase reactivation through upregulation of the human telomerase reverse transcriptase (hTERT). The hypermethylation of a specific region within the hTERT promoter, termed TERT hypermethylated oncological region (THOR) has been associated with increased hTERT expression in cancer. However, its biological role and clinical potential in BC have never been studied to the best of our knowledge. Therefore, we aimed to investigate the role of THOR as a biomarker and explore the functional impact of THOR methylation status in hTERT upregulation in BC.

RESULTS

THOR methylation status in BC was assessed by pyrosequencing on discovery and validation cohorts. We found that THOR is significantly hypermethylated in malignant breast tissue when compared to benign tissue (40.23% vs. 12.81%, P < 0.0001), differentiating malignant tumor from normal tissue from the earliest stage of disease. Using a reporter assay, the addition of unmethylated THOR significantly reduced luciferase activity by an average 1.8-fold when compared to the hTERT core promoter alone (P < 0.01). To further investigate its biological impact on hTERT transcription, targeted THOR demethylation was performed using novel technology based on CRISPR-dCas9 system and significant THOR demethylation was achieved. Cells previously demethylated on THOR region did not develop a histologic cancer phenotype in in vivo assays. Additional studies are required to validate these observations and to unravel the causality between THOR hypermethylation and hTERT upregulation in BC.

CONCLUSIONS

THOR hypermethylation is an important epigenetic mark in breast tumorigenesis, representing a promising biomarker and therapeutic target in BC. We revealed that THOR acts as a repressive regulatory element of hTERT and that its hypermethylation is a relevant mechanism for hTERT upregulation in BC.

Ratiometric fluorescence resonance energy transfer for reliable and sensitive detection of intracellular telomerase RNA via strand displacement reaction amplification

Human telomerase RNA (hTR) is one essential component of telomerase and is overexpressed in tumor cells. Therefore, the reliable and sensitive detection of hTR is essential for the early cancer diagnosis. Herein, to avoid the false positive signals caused by co-existing components in the cell, a ratiometric fluorescence resonance energy transfer (FRET) strategy was developed to achieve reliable detection of intracellular hTR. Manganese dioxide nanosheets (MnO₂NS) with good biocompatibility carry two fluorophore-labelled hairpin DNA probes into the cancer cell and then release the probes via decomposition of MnO₂NS by intracellular L-glutathione reduced (GSH). Then, hTR triggered the cyclic strand displacement reaction (SDR) between two hairpin DNA probes to continuously form DNA duplexes, which made two fluorophores close to each other and led to an effective FRET. Fluorescence imaging demonstrated a higher expression level of hTR in HeLa cells than that in normal HL-7702 cells. The high specificity of hairpin DNA probes and SDR make it easy to discriminate the single-base mutation. Therefore, it provides a highly sensitive, simple and reliable method for the extracellular and intracellular detection of hTR.

Telomere maintenance mechanism dysregulation serves as an early predictor of adjuvant therapy response and a potential therapeutic target in human cancers

Telomere maintenance mechanisms (TMMs) rescue cells from telomere crisis, endow cells immortal property, stabilize genomic integrity. However, TMM-associated molecular profiles and their clinical outcomes in cancer remain elusive. Here, we performed a pan-cancer and integrated analysis of TMM gene expression profiles from 10,107 unique samples with clinicopathological, molecular and outcome features across 7 malignancies from the same microarray platform (Affymetrix GPL570 platform). This resource was divided into Case-Control datasets for obtaining dysregulated TMM genes and Survival datasets for evaluating clinical outcomes. Multidimensional data from The Cancer Genome Atlas (TCGA) were used to elucidate associations between TMM dysregulation and survival, genomic instability. Our results demonstrated that TMMs had a consistent dysregulation spectrum across cancers, based on which we developed the TMM-dysregulation signature TMScore that was positively associated with various tumor adverse features. Two opposite prognostic patterns of TMScore independent of clinicopathological and molecular characteristics were identified, which might be explained by genomic instability: breast and lung cancer patients with elevated TMScore had inferior outcomes, suggesting TMScore-related genes as potential therapeutic targets, on the contrary, colon and stomach cancer patients had superior outcomes. Most important, the prognostic value of TMScore was still significant regardless of whether patients had received adjuvant therapy, which was valuable for discriminating non-responders from responders, and could predict the effectiveness of adjuvant therapy. In summary, our resources delineate TMMs dysregulated landscape across cancers, shed light on the impact of TMMs dysregulation on patient outcomes and adjuvant therapy, and provide novel therapeutic opportunities for cancer treatment.

hTERT DNA Methylation Analysis Identifies a Biomarker for Retinoic Acid-Induced hTERT Repression in Breast Cancer Cell Lines

Telomerase reactivation is responsible for telomere preservation in about 90% of cancers, providing cancer cells an indefinite proliferating potential. Telomerase consists of at least two main subunits: a catalytic reverse transcriptase protein (hTERT) and an RNA template subunit. Strategies to inhibit hTERT expression seem promising for cancer treatment. Previous works showed that all-trans retinoic acid (ATRA) induces hTERT repression in acute promyelocytic leukemia cells, resulting in their death. Here, we investigated the effects of ATRA in a subset of breast cancer cell lines. The mutational status of hTERT promoter and the methylation patterns at a single CpG resolution were assessed. We observed an inverse relationship between hTERT expression after ATRA treatment and the methylation level of a specific CpG at chr5: 1,300,438 in a region of hTERT gene at −5 kb of the transcription initiation site. This observation highlighted the significance of this region, whose methylation profile could represent a promising biomarker to predict the sensitivity to ATRA-induced hTERT repression in specific breast cancer subtypes. As hTERT repression promotes drug-induced cell death, checking the methylation status of this unique region and the specific CpG included can help in decision-making to include ATRA in combination therapy and contributes to a better clinical outcome.

Prominent Prognostic Factors in Aggressive Breast Cancer: A Review

Context: Breast cancer (BC) is the most common cancer in women worldwide. Hereditary susceptibility created by mutations in autosomal dominant genes is responsible for 5 to 10% of all BC cases in women. Recent studies have identified genes associated with increased risk for aggressive BC, providing the basis for better risk management. Evidence Acquisition: The latest information in National Center for Biotechnology Information (NCBI), Google Scholar, ScienceDirect, and Scopus were the main databases for finding articles. A combination of keywords of ‘metastasis’, ‘invasion’, ‘aggressive breast cancer’, ‘prognostic factor’, ‘mutation’, and ‘cancer treatment’ was searched in the databases to identify related articles. Titles and abstracts of the articles were studied to choose the right articles. Results: Mutations in breast cancer type 1 susceptibility protein (BRCA1) and breast cancer type 2 susceptibility protein (BRCA2) genes are two central players related to the high risk of BC. Mutation in tumor protein p53 (TP53) is another important mutation that leads to triple-negative BC. Although the majority of BC types are not associated with high-throughput mutant genes such as BRCA1, BRCA2, and TP53, they are associated with low-throughput genes, including DNA repair protein Rad50 (RAD50), Nijmegen breakage syndrome gene (NBS1), checkpoint kinase 2 (CHEK2), BRCA1-interacting protein 1 (BRIP1), E-cadherin gene (CDH1) and PALB2, UCHL1, aldehydedehydrogenase1A3 (ALDH1A3), androgen receptor (AR), 5-bisphosphate 3-kinase (PIK3CA), phosphatidylinositol-4, and luminal gene expression that are generally mutated in the global population. High tumor mutational burden (TMB) was associated with improved progression-free survival. Conclusions: The lymph node status, early tumor size, ER, PR, human epidermal growth factor receptor-2 (HER2), and Ki-67 are conventional prognostic factors for BC. However, these factors cannot exactly predict the aggressive behavior of BC. Hence, in this review, we discussed new prognostic factors of aggressive BCs that are useful for the treatment of patients with BC.

Alternative Splicing of Human Telomerase Reverse Transcriptase (hTERT) and Its Implications in Physiological and Pathological Processes

Alternative splicing (AS) of human telomerase catalytic subunit (hTERT, human telomerase reverse transcriptase) pre-mRNA strongly regulates telomerase activity. Several proteins can regulate AS in a cell type-specific manner and determine the functions of cells. In addition to being involved in telomerase activity regulation, AS provides cells with different splice variants that may have alternative biological activities. The modulation of telomerase activity through the induction of hTERT AS is involved in the development of different cancer types and embryos, and the differentiation of stem cells. Regulatory T cells may suppress the proliferation of target human and murine T and B lymphocytes and NK cells in a contact-independent manner involving activation of TERT AS. This review focuses on the mechanism of regulation of hTERT pre-mRNA AS and the involvement of splice variants in physiological and pathological processes.

Pan-Cancer Analysis of Alternative Lengthening of Telomere Activity

Alternative lengthening of telomeres (ALT) is a telomerase-independent mechanism that extends telomeres in cancer cells. It influences tumorigenesis and patient survival. Despite the clinical significance of ALT in tumors, the manner in which ALT is activated and influences prognostic outcomes in distinct cancer types is unclear. In this work, we profiled distinct telomere maintenance mechanisms (TMMs) using 8953 transcriptomes of 31 different cancer types from The Cancer Genome Atlas (TCGA). Our results demonstrated that approximately 29% of cancer types display high ALT activity with low telomerase activity in the telomere-lengthening group. Among the distinct ALT mechanisms, homologous recombination was frequently observed in sarcoma, adrenocortical carcinoma, and kidney chromophobe. Five cancer types showed a significant difference in survival in the presence of high ALT activity. Sarcoma patients with elevated ALT had unfavorable risks (p < 0.038) coupled with a high expression of TOP2A, suggesting this as a potential drug target. On the contrary, glioblastoma patients had favorable risks (p < 0.02), and showed low levels of antigen-presenting cells. Together, our analyses highlight cancer type-dependent TMM activities and ALT-associated genes as potential therapeutic targets.

Telomerase and CD4 T Cell Immunity in Cancer

Telomerase reverse transcriptase (TERT) is a conserved self-tumor antigen which is overexpressed in most tumors and plays a critical role in tumor formation and progression. As such, TERT is an antigen of great relevance to develop widely applicable immunotherapies. CD4 T cells play a major role in the anti-cancer response alone or with other effector cells such as CD8 T cells and NK cells. To date, efforts have been made to identify TERT peptides capable of stimulating CD4 T cells that are also able to bind diverse MHC-II alleles to ease immune status monitoring and immunotherapies. Here, we review the current status of TERT biology, TERT/MHC-II immunobiology, and past and current vaccine clinical trials. We propose that monitoring CD4 T cell immunity against TERT is a simple and direct way to assess immune surveillance in cancer patients and a new way to predict the response to immune checkpoint inhibitors (ICPi). Finally, we present the initial results of a systematic discovery of TERT peptides able to bind the most common HLA Class II alleles worldwide and show that the repertoire of MHC-II TERT peptides is wider than currently appreciated.

A facile DNA/RNA nanoflower for sensitive imaging of telomerase RNA in living cells based on "zipper lock-and-key" strategy

The sensitive imaging of telomerase RNA (TR) in living cells is crucial for improved guidance in cancer clinical diagnosis because its expression level is closely related to malignant diseases. The efficient delivery of multiple nucleic acid probes to target cells is critical for nucleic acid-based methods to successfully image low-abundance TR in living cells. While novel nanomaterials enhance delivery efficiency, uncontrolled loading and slow intracellular release remain major challenges for multiple-probe delivery. Here, we designed a facile DNA/RNA nanoflower (NF) to perform the controlled loading of multiple probes and rapid intracellular release based on the "zipper lock-and-key" strategy. First, a long RNA generated by rolling circle transcription acts as both the "smart zipper lock" and the delivery carrier to alternately lock multiple functional DNAs through DNA-RNA base pairing, and the resulting RNA/DNA hybrids self-assemble into packed NFs. The functional DNAs include the fluorescence molecular beacon H₁ for TR recognition, H₂ for hybrid chain reaction (HCR) and DNA-cholesterol for size control. After NF internalization by the cells, the intracellular RNase H acts as the "key" to specifically open the DNA/RNA NFs by cleaving the RNA in the DNA/RNA hybrid, releasing high amounts of H₁ and H₂ in a confined space and thereby facilitating the HCR amplification analysis of cytoplasmic TR. With the addition of a DNA-nuclear localization peptide component in the same NF, nuclear TR can also be sensitively detected. Compared with the regular H₁/H₂ mixture, the DNA/RNA NFs produced a higher-contrast fluorescence signal. This indicated that the proposed strategy allowed the side arms of H₁/H₂ to be sealed into the RNA sequence-programmed "zipper lock" by controlled loading, avoiding mutual nonspecific H₁/H₂ hybridization. In addition, due to the fast kinetics of the RNase endonuclease reaction, the loaded H₁/H₂ was quickly released. Furthermore, the strategy was successfully used to assay the expression levels of TR in HeLa, HepG2 and HL-7702 cells, demonstrating that this approach holds the potential for the sensitive detection of low-abundance biomarkers in living cells.

Multi-code magnetic beads based on DNAzyme-mediated double-cycling amplification for a point-of-care assay of telomerase activity

Development of a reliable and facile telomerase activity assay with high specificity and sensitivity is a central challenge to make telomerase testing a routine part of medical care with respect to cancer.

Human telomerase reverse transcriptase protein expression predicts tumour aggressiveness and survival in patients with clear cell renal cell carcinoma

Human telomerase reverse transcriptase (hTERT) is an active component of telomerase and responsible for its catalytic activity, associated with cell proliferation and differentiation. For the first time, the present study was conducted to evaluate the expression and prognostic significance of hTERT in different histological subtypes of renal cell carcinoma (RCC). Expression of hTERT was examined in 176 well-defined renal tumour samples including clear cell RCCs (ccRCCs), papillary and chromophobe RCCs using immunohistochemistry on tissue microarrays. The association between hTERT expression and clinicopathological parameters as well as survival outcomes were then analysed. There was a statistically significant difference in terms of hTERT expression among various RCC subtypes. In ccRCC, increased expression of hTERT was significantly associated with advanced stage, higher grade, presence of microvascular invasion, lymph node invasion, and metastasis. Moreover, in the multivariate analysis, tumour stage and tumour size were independent predictors of the disease-specific survival (DSS). Additionally, expression of hTERT was found to be a significant predictor of worse DSS (p = 0.012) in the univariate analysis. In papillary carcinoma samples (type I and II), significant association was detected between hTERT expression and the tumour stage (p = 0.010, p = 0.050), respectively. In chromophobe RCC, no significant association was detected between expression of hTERT and clinicopathological parameters and survival data. We showed that hTERT protein expression was associated with more aggressive tumour behaviour and more advanced disease in ccRCC patients. Also, hTERT may be a novel poor prognostic indicator of DSS, if the patients are followed for more prolonged time periods.

Sticky-flares for in situ monitoring of human telomerase RNA in living cells

Human telomerase RNA (hTR), a template of telomerase for telomeric repeat synthesis, was used to reflect the telomerase activity and act as a potential target of antitumor therapy. Here, we report a novel DNA-conjugated AuNP probe termed sticky-flares for the in situ detection of intracellular human telomerase RNA. The sticky-flares probe is capable of entering living cells directly without any auxiliary and recognizing the binding domain of human telomerase RNA. On recognition, the fluorophore-modified recognition flares can specifically bind to the target, separate from the sticky-flares and act as a fluorescent reporter to quantify and dynamically profile human telomerase RNA in living cells. We envision that the sticky-flares probe would be a valuable platform to investigate the function and regulation of hTR in antitumor therapy and hTR-related drug invention.

The Differential Regulation of Human Telomerase Reverse Transcriptase and Vascular Endothelial Growth Factor May Contribute to the Clinically More Aggressive Behavior of P63-Positive Breast Carcinomas

p63, a p53 homologue, is a myoepithelial cell marker in the normal mammary gland but p63-positive neoplastic cells may be found in up to 11% of invasive breast carcinomas. This study aims to verify the relationship between p63 expression and several clinicopathological features and tumor markers of clinical significance in breast pathology including key regulators of the cell cycle, oncogenes, apoptosis-related proteins, metalloproteinases and their inhibitors. Immunohistochemistry with 27 primary antibodies was performed in 100 formalin-fixed paraffin-embedded samples of invasive ductal carcinomas. p63-positive cells were found in 16% of carcinomas. p63-positive carcinomas were poorly differentiated, hormone receptor-negative neoplasms with a high proliferation rate. p63 also correlated with advanced pathological stage, tumor size, and the expression of human telomerase reverse transcriptase (hTERT), tissue inhibitor of matrix metalloproteinase 1 (TIMP1) and vascular endothelial growth factor (VEGF). The expression of TIMP1 suggests that the anti-proteolytic stimuli may be preponderant in p63-positive carcinomas. hTERT activity is associated with nodal metastases and cellular proliferation. VEGF regulates angiogenesis, which is also a fundamental event in the process of tumor growth and metastatic dissemination. Thus, the differential regulation of hTERT and VEGF in p63-positive breast carcinomas may contribute to the clinically more aggressive behavior of these neoplasms.

Epigenetic silencing of miR-296 and miR-512 ensures hTERT dependent apoptosis protection and telomere maintenance in basal-type breast cancer cells

The catalytic subunit of the telomerase complex, hTERT, ensures unlimited proliferative potential of cancer cells by maintaining telomere function and protecting from apoptosis. Using a miRNA screening approach we identified miR-296-5p and miR-512-5p as miRNAs that target hTERT in breast cancer cells. Ectopic miR-296-5p and miR-512-5p reduce telomerase activity, drive telomere shortening and cause proliferation defects by enhancing senescence and apoptosis in breast cancer cells. In line with the relevance of hTERT expression for human cancer we found that miR-296-5p and miR-512-5p expression is reduced in human breast cancer. Accordingly, high expression of miR-296-5p and miR-512-5p target genes including hTERT is linked with significantly reduced distant metastasis free survival and relapse free survival of basal type breast cancer patients. This suggests relevance of the identified miRNAs in basal type breast cancer. Epigenetic silencing of miR-296 and miR-512 encoding genes is responsible for low levels of miR-296-5p and miR-512-5p expression in basal type breast cancer cells. Disrupting gene silencing results in a dramatic upregulation of miR-296-5p and miR-512-5p levels leading to reduced hTERT expression and increased sensitivity to the induction of apoptosis. Altogether, our data suggest that epigenetic regulatory circuits in basal type breast cancer may contribute to high hTERT levels by silencing miR-296-5p and miR-512-5p expression, thereby contributing to the aggressiveness of basal type breast cancer.

Novel plasma telomerase detection method to improve cancer diagnostic assessment

Background

The activity levels of telomerase and its mRNA have been found to be more diagnostically sensitive than cytological results in many cancerous tissues and correlate well with the clinical disease stage. Currently, there are several methods of detecting telomerase in tissues and in blood. The most commonly used method is a conventional quantitative real-time polymerase chain reaction (PCR) which is time and labor exhausting.

Methods

We have developed a simple and innovative blood test method that allows us to diagnose cancer and relapsed cancer in a cost- and time -effective manner. We had evaluated our novel method in two populations: 1) in vivo in three mice with pancreatic ductal adenocarcinoma (PDAC) versus one control mouse and 2) clinically in 30 cancer patients versus 10 individuals without cancer. We compared our novel method with the old conventional method. At least one sample was obtained from each patient included in the study.

Results

The novel method substantially increased the sensitivity (from 37% to 77%, p<0.001) and negative predictive value (from 32% to 56%, p = 0.005) of the telomerase test for all cancer patients (those who were substantially treated and those who were not). There was no significant difference in telomerase activity between cancer patients and healthy volunteers using the conventional method (p = 0.13), whereas there was a significant difference using the novel method (p = 0.001).

Conclusion

Conventional method shows no significant difference in telomerase activity between cancer patients and healthy volunteers (p = 0.13), whereas there was a significant difference using the novel method (p = 0.001).

Alternative Splicing of hTERT Pre-mRNA: A Potential Strategy for the Regulation of Telomerase Activity

The activation of telomerase is one of the key events in the malignant transition of cells, and the expression of human telomerase reverse transcriptase (hTERT) is indispensable in the process of activating telomerase. The pre-mRNA alternative splicing of hTERT at the post-transcriptional level is one of the mechanisms for the regulation of telomerase activity. Shifts in splicing patterns occur in the development, tumorigenesis, and response to diverse stimuli in a tissue-specific and cell type–specific manner. Despite the regulation of telomerase activity, the alternative splicing of hTERT pre-mRNA may play a role in other cellular functions. Modulating the mode of hTERT pre-mRNA splicing is providing a new precept of therapy for cancer and aging-related diseases. This review focuses on the patterns of hTERT pre-mRNA alternative splicing and their biological functions, describes the potential association between the alternative splicing of hTERT pre-mRNA and telomerase activity, and discusses the possible significance of the alternative splicing of the hTERT pre-mRNA in the diagnosis, therapy, and prognosis of cancer and aging-related diseases.

Telomeres and telomerase in head and neck squamous cell carcinoma: from pathogenesis to clinical implications

Strongly associated with tobacco use, heavy alcohol consumption, and with high-risk human papillomavirus (HPV) infection, head and neck squamous cell carcinoma (HNSCC) is a frequently lethal, heterogeneous disease whose pathogenesis is a multistep and multifactorial process involving genetic and epigenetic events. The majority of HNSCC patients present with locoregional advanced stage disease and are treated with combined modality strategies that can markedly impair quality of life and elicit unpredictable results. A large fraction of those who undergo locoregional treatment and achieve a complete response later develop locoregional recurrences or second field tumors. Biomarkers that are thus able to stratify risk and enable clinicians to tailor treatment plans and to personalize post-therapeutic surveillance strategies are highly desirable. To date, only HPV status is considered a reliable independent predictor of treatment response and survival in patients with HNSCC arising from the oropharyngeal site. Recent studies suggest that telomere attrition, which may be an early event in human carcinogenesis, and telomerase activation, which is detected in up to 90 % of malignancies, could be potential markers of cancer risk and disease outcome. This review examines the current state of knowledge on and discusses the implications linked to telomere dysfunction and telomerase activation in the development and clinical outcome of HNSCC.

A dual-colored ratiometric-fluorescent oligonucleotide probe for the detection of human telomerase RNA in cell extracts

A dual-colored ratiometric-fluorescent oligonucleotide probe is designed for the detection of human telomerase RNA (hTR) in cell extracts.

Evaluation of Telomerase in Canine Mammary Tissues by Immunohistochemical Analysis and a Polymerase Chain Reaction-Based Enzyme-Linked Immunosorbent Assay

The enzyme telomerase is considered a potential marker for neoplastic tissue and is used as a diagnostic and prognostic tool in clinical medicine and therapeutics. For this reason, the possible role of telomerase activation in the process of malignant transformation is currently the subject of intense research efforts. The focus of the study reported here was to detect telomerase in 37 canine mammary samples, by comparing two methods: immunohistochemical (IHC) analysis for detecting the catalytic subunit of the enzyme, telomerase reverse transcriptase (TERT), and the telomeric repeat amplification protocol–enzyme-linked immunosorbent assay (TRAP-ELISA), a polymerase chain reaction (PCR)-based technique that uses a colorimetric detection method. Using the TRAP-ELISA, samples were considered positive when they yielded a difference of at least 0.2 absorbance units between the readings at 450 nm versus 690 nm wavelength. On the basis of this criterion, 18 negative and 19 positive cases were obtained. Specific immunohistochemical staining was observed mainly in the nucleoli, to a lesser extent in the nuclei, and rarely in the cytoplasm of epithelial cells. A sample was considered positive when at least 10% of the epithelial cells had specific staining. The Pearson correlation between the TRAP-ELISA and IHC results was significant only when IHC nucleolar ( r = 0.53, P < 0.01) or nuclear ( r = 0.36, P < 0.05) staining or their combination ( r = 0.58, P < 0.01) was considered. Thus, IHC staining of nucleoli and nuclei can be considered as an alternative method to the TRAP-ELISA. The detection of telomerase in normal mammary gland and fibrocystic mastopathy using both methods does not support the idea that telomerase may be used as a specific marker of mammary neoplasia in dogs.

Dyskerin and TERC expression may condition survival in lung cancer patients

Dyskerin mediates both the modification of uridine on ribosomal and small nuclear RNAs and the stabilization of the telomerase RNA component (TERC). In human tumors dyskerin expression was found to be associated with both rRNA modification and TERC levels. Moreover, dyskerin overexpression has been linked to unfavorable prognosis in a variety of tumor types, however an explanation for the latter association is not available. To clarify this point, we analyzed the connection between dyskerin expression, TERC levels and clinical outcome in two series of primary lung cancers, differing for the presence of TERC gene amplification, a genetic alteration inducing strong TERC overexpression. TERC levels were significantly higher in tumors bearing TERC gene amplification (P = 0.017). In addition, the well-established association between dyskerin expression and TERC levels was observed only in the series without TERC gene amplification (P = 0.003), while it was not present in TERC amplified tumors (P = 0.929). Similarly, the association between dyskerin expression and survival was found in cases not bearing TERC gene amplification (P = 0.009) and was not observed in TERC amplified tumors (P = 0.584). These results indicate that the influence of dyskerin expression on tumor clinical outcome is linked to its role on the maintenance of high levels of TERC.

Telomere and Telomerase Therapeutics in Cancer

Telomerase is a reverse transcriptase capable of utilizing an integrated RNA component as a template to add protective tandem telomeric single strand DNA repeats, TTAGGG, to the ends of chromosomes. Telomere dysfunction and telomerase reactivation are observed in approximately 90% of human cancers; hence, telomerase activation plays a unique role as a nearly universal step on the path to malignancy. In the past two decades, multiple telomerase targeting therapeutic strategies have been pursued, including direct telomerase inhibition, telomerase interference, hTERT or hTERC promoter driven therapy, telomere-based approaches, and telomerase vaccines. Many of these strategies have entered clinical development, and some have now advanced to phase III clinical trials. In the coming years, one or more of these new telomerase-targeting drugs may be expected to enter the pharmacopeia of standard care. Here, we briefly review the molecular functions of telomerase in cancer and provide an update about the preclinical and clinical development of telomerase targeting therapeutics.

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.

Telomere maintenance mechanisms in cancer: clinical implications

The presence of immortal cell populations with an up-regulated telomere maintenance mechanism (TMM) is an almost universal characteristic of cancers, whereas normal somatic cells are unable to prevent proliferation-associated telomere shortening and have a limited proliferative potential. TMMs and related aspects of telomere structure and function therefore appear to be ideal targets for the development of anticancer therapeutics. Such treatments would be targeted to a specific cancer-related molecular abnormality, and also be broad-spectrum in that they would be expected to be potentially applicable to most cancers. However, the telomere biology of normal and malignant human cells is a relatively young research field with large numbers of unanswered questions, so the optimal design of TMM-targeted therapeutic approaches remains unclear. This review outlines the opportunities and challenges presented by telomeres and TMMs for clinical management of cancer.

UBE2D3 is a positive prognostic factor and is negatively correlated with hTERT expression in esophageal cancer

Human telomerase reverse transcriptase (hTERT) is a critical factor in unlimited cell proliferation and immortalization, with numerous studies demonstrating that high expression of hTERT is a poor prognostic factor in various types of cancer. Ubiquitin-conjugating enzyme E2D 3 (UBE2D3) is a member of the E2 family, and participates in the ubiquitin proteasome pathway to regulate basic cellular activities, such as cell cycle control, the DNA damage response, apoptosis, and tumorigenesis. Our previous study initially determined that downregulation of UBE2D3 expression increases hTERT expression and cell proliferation, however, the association between the expression of these two proteins and their functions in cancer tissues remains unknown. Therefore, the protein expression levels of hTERT and UBE2D3 were evaluated in 150 esophageal cancer and 30 adjacent healthy tissue samples by performing immunohistochemical analysis. Concurrently, the clinicopathological data of the enrolled patients were obtained to allow correlation analysis. It was identified that the expression of hTERT in the esophageal cancer tissues was significantly higher compared with that of the adjacent tissues (P=0.015), however, the expression of UBE2D3 was significantly lower in esophageal cancer tissues than the adjacent tissues (P=0.001). Additionally, the study demonstrated that hTERT was significantly upregulated in poorly-differentiated, advanced tumor-node-metastasis (TNM) stage cancer tissues (P<0.05 for all), however, UBE2D3 expression was downregulated in poorly-differentiated, lymph node invaded cancer tissues and recurrent cases. It was also identified that traditional factors, including tumor location, T stage, lymph node status, TNM stage, and molecular factors of hTERT and UBE2D3, were significantly associated with overall survival time (P<0.05 for all). Furthermore, UBE2D3, lymph node status and tumor location were independent prognostic factors for esophageal cancer in multivariate analysis. Most notably, hTERT and UBE2D3 expression were negatively correlated with each other. In conclusion, the findings of the present study indicated that hTERT and UBE2D3 proteins appear to be involved in the development of esophageal cancer, that UBE2D3 may a positive prognostic factor for esophageal cancer, and that UBE2D3 and hTERT expression levels are inversely correlated.

Expression distribution of cancer stem cells, epithelial to mesenchymal transition, and telomerase activity in breast cancer and their association with clinicopathologic characteristics

A total of 167 surgically resected primary invasive breast carcinomas and 63 metastatic lymph node lesions were analyzed for immunohistochemical (IHC) localization of the CD44⁺CD24^−low breast cancer stem cell (CSC) markers, epithelial to mesenchymal transition (EMT) markers, and telomerase activity by double-staining IHC technique, in formalin-fixed, paraffin-embedded tissue, the results were validated by double-staining immunofluorescent and flow cytometry techniques. The results showed that CSCs with CD44⁺CD24^−low phenotype were significantly increased in node-positive tumors, high-grade tumors, and ductal carcinoma in situ (DCIS). There was a high incidence of telomerase expression in metastatic lymph node lesion. There were considerably high number of tumor cells with EMT expression in metastatic lymph node lesion, and triple-negative tumor. The occurrence of EMT phenomena was usually accompanied by the co-existence of CSCs of CD44⁺CD24^−low phenotype. There was no association between the existence of CSCs and detection of telomerase activity in tumor cells. Increased numbers of both CSCs of CD44⁺CD24^−low phenotype and cells underwent EMT in DCIS lesion might be an initial step in the stromal invasion and propagation of breast cancer, and occurrence of EMT in the breast tumor associated with high prevalence of CSCs, promoting tumor invasiveness and metastasis.

Breast cancer biomarkers and molecular medicine: part II

In this second part of the two-part review of breast cancer biomarkers and molecular medicine, the first section will consider additional breast cancer prognostic factors, including oncogenes, tumor suppressor genes, cell adhesion molecules, invasion-associated proteins and proteases, hormone receptor proteins, drug resistance proteins, apoptosis regulators, transcription factors, telomerase, DNA repair and methylation and transcriptional profiling using high-density genomic microarrays. The second section will consider the prediction of therapy response using the techniques of pharmacogenetics and pharmacogenomics.

CEBP factors regulate telomerase reverse transcriptase promoter activity in whey acidic protein-T mice during mammary carcinogenesis

Telomerase is activated in the majority of invasive breast cancers, but the time point of telomerase activation during mammary carcinogenesis is not clear. We have recently presented a transgenic mouse model to study human telomerase reverse transcriptase (TERT) gene expression in vivo (hTERTp-lacZ). In the present study, hTERTp-lacZxWAP-T bitransgenic mice were generated to analyze the mechanisms responsible for human and mouse TERT upregulation during tumor progression in vivo. We found that telomerase activity and TERT expression were consistently upregulated in SV40-induced invasive mammary tumors compared to normal and hyperplastic tissues and ductal carcinoma in situ (DCIS). Human and mouse TERT genes are regulated similarly in the breast tissue, involving the CEBP transcription factors. Loss of CEBP-α and induction of CEBP-β expression correlated well with the activation of TERT expression in mouse mammary tumors. Transfection of CEBP-α into human or murine cells resulted in TERT repression, whereas knockdown of CEBP-α in primary human mammary epithelial cells resulted in reactivation of endogenous TERT expression and telomerase activity. Conversely, ectopic expression of CEBP-β activated endogenous TERT gene expression. Moreover, ChIP and EMSA experiments revealed binding of CEBP-α and CEBP-β to human TERT-promoter. This is the first evidence indicating that CEBP-α and CEBP-β are involved in TERT gene regulation during carcinogenesis.

Differential control of growth, apoptotic activity, and gene expression in human breast cancer cells by extracts derived from medicinal herbs Zingiber officinale

The present study aimed to examine the antiproliferative potentiality of an extract derived from the medicinal plant ginger (Zingiber officinale) on growth of breast cancer cells. Ginger treatment suppressed the proliferation and colony formation in breast cancer cell lines, MCF-7 and MDA-MB-231. Meanwhile, it did not significantly affect viability of nontumorigenic normal mammary epithelial cell line (MCF-10A). Treatment of MCF-7 and MDA-MB-231 with ginger resulted in sequences of events marked by apoptosis, accompanied by loss of cell viability, chromatin condensation, DNA fragmentation, activation of caspase 3, and cleavage of poly(ADP-ribose) polymerase. At the molecular level, the apoptotic cell death mediated by ginger could be attributed in part to upregulation of Bax and downregulation of Bcl-2 proteins. Ginger treatment downregulated expression of prosurvival genes, such as NF-κB, Bcl-X, Mcl-1, and Survivin, and cell cycle-regulating proteins, including cyclin D1 and cyclin-dependent kinase-4 (CDK-4). On the other hand, it increased expression of CDK inhibitor, p21. It also inhibited the expression of the two prominent molecular targets of cancer, c-Myc and the human telomerase reverse transcriptase (hTERT). These findings suggested that the ginger may be a promising candidate for the treatment of breast carcinomas.

Prognostic role of telomerase activity in gastric adenocarcinoma: A meta-analysis

Activation of telomerase is involved in carcinogenesis in most types of cancers. However, the prognostic value of telomerase activity (TA) in patients with gastric carcinoma (GC) remains controversial. We conducted a meta-analysis to assess the relationship between TA and the clinical outcome of GC. A meta-analysis of 18 studies (886 patients) was performed to evaluate the association between TA and metastasis-related parameters in GC patients by searching databases, including PubMed, MEDLINE, EMBASE, Web of Science databases, Cochrane Library and the Chinese Biomedical Literature database (CBM) (last search updated in October 2011). We used the odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the association between TA and metastasis of GC. Our analysis results indicated that high telomerase activity expression tended to be associated with the presence of lymph node metastasis (866 patients) (OR=2.03, 95% CI 1.21-3.39, p=0.007), the depth of invasion (886 patients) (OR=1.87, 95% CI 1.30-2.70, p=0.0007), distant metastasis (407 patients) (OR=2.71, 95% CI 1.59-4.63, p=0.0002), tumor size (466 patients) (OR=2.14, 95% CI 1.31-3.50, p=0.002) and TNM stage (711 patients) (OR=2.39, 95% CI 1.30-4.41, p=0.005). However, high TA expression was not associated with the presence of histologic differentiation (791 patients) (OR=1.51, 95% CI 0.73-3.11, p=0.26). In conclusion, telomerase overexpression not only plays a key role in primary initiation, but also promotes invasion and metastatic progression of GC. These findings raise the possibility of using TA to screen for the prognosis of gastric cancer.

Dysfunctional telomeres promote genomic instability and metastasis in the absence of telomerase activity in oncogene induced mammary cancer

Telomerase is a ribonucleoprotein that maintains the ends of chromosomes (telomeres). In normal cells lacking telomerase activity, telomeres shorten with each cell division because of the inability to completely synthesize the lagging strand. Critically shortened telomeres elicit DNA damage responses and limit cellular division and lifespan, providing an important tumor suppressor function. Most human cancer cells express telomerase which contributes significantly to the tumor phenotype. In human breast cancer, telomerase expression is predictive of clinical outcomes such as lymph node metastasis and survival. In mouse models of mammary cancer, telomerase expression is also upregulated. Telomerase overexpression resulted in spontaneous mammary tumor development in aged female mice. Increased mammary cancer also was observed when telomerase deficient mice were crossed with p53 null mutant animals. However, the effects of telomerase and telomere length on oncogene driven mammary cancer have not been completely characterized. To address these issues we characterized neu proto-oncogene driven mammary tumor formation in G1 Terc-/- (telomerase deficient with long telomeres), G3 Terc-/- (telomerase deficient with short telomeres), and Terc+/+ mice. Telomerase deficiency reduced the number of mammary tumors and increased tumor latency regardless of telomere length. Decreased tumor formation correlated with increased apoptosis in Terc deficient tumors. Short telomeres dramatically increased lung metastasis which correlated with increased genomic instability, and specific alterations in DNA copy number and gene expression. We concluded that short telomeres promote metastasis in the absence of telomerase activity in neu oncogene driven mammary tumors.

Telomerase expression and telomere length in breast cancer and their associations with adjuvant treatment and disease outcome

Introduction

Telomere length plays important roles in maintaining genome stability and regulating cell replication and death. Telomerase has functions not only to extend telomere length but also to repair DNA damage. Studies have shown that telomerase may increase cancer cell resistance to DNA-damaging anticancer agents; tamoxifen may suppress telomerase expression in breast cancer cells. This study aimed to investigate the role of telomere length and telomerase activity in breast cancer prognosis.

Methods

qPCR and qRT-PCR were used to analyze telomere length and telomerase expression, respectively, in tumor samples of 348 breast cancer patients. Cox regression analysis was performed to examine telomere length and telomerase expression in association with disease-free survival and cause-specific mortality.

Results

Telomere length had no relation to tumor features or disease outcomes. Telomerase expression was detected in 53% of tumors. Larger tumors or aggressive disease were more likely to have telomerase expression. Among patients treated with chemotherapy, high telomerase was found to be associated with increased risk of death (hazard ratio (HR) = 3.15; 95% CI: 1.34 to 7.40) and disease recurrence (HR = 2.04; 95% CI: 0.96 to 4.30) regardless of patient age, disease stage, tumor grade, histological type or hormone receptor status. Patients treated with endocrine therapy had different results regarding telomerase: high telomerase appeared to be associated with better survival outcomes. Telomerase expression made no survival difference in patients who received both chemotherapy and endocrine therapy.

Conclusions

Overall, telomerase expression was not associated with disease outcome, but this finding may be masked by adjuvant treatment. Patients with high telomerase expression responded poorly to chemotherapy in terms of disease-free and overall survival, but fared better if treated with endocrine therapy.

Dyskerin and cancer: more than telomerase. The defect in mRNA translation helps in explaining how a proliferative defect leads to cancer

Point mutations in the DKC1 gene that encodes dyskerin cause the rare inherited syndrome called X-linked dyskeratosis congenita, characterized by a failure of proliferating tissues and increased susceptibility to cancer. Dyskerin is a nucleolar protein with different functions, all fundamental to basic cellular events such as protein expression, growth, and proliferation. The two best-characterized dyskerin activities are the stabilization of the telomerase RNA component, allowing the proper function telomerase enzymatic complex, and the modification of specific uridine residues of ribosomal RNA by converting them to pseudouridine, thus allowing proper ribosome processing and function. In light of the recent findings, this review focuses on the molecular pathogenesis of dyskeratosis congenita, discussing how a defect in ribosomal function might impact on the translation of a subset of mRNAs encoding for tumour suppressors, thus providing an explanation for the apparent paradox of dyskeratosis congenita in which reduced cell proliferation is associated with cancer susceptibility. In addition, the current evidence pointing to a role played by dyskerin in tumours in the general population is also discussed.

Microenvironment and pathogenesis of epithelial ovarian cancer

Multiple genetic alterations play a role in the pathogenesis of ovarian cancer. Although many key proteins and pathways involved in ovarian carcinogenesis and metastasis have been discovered, knowledge of the early steps leading to malignancy remains poorly understood. This poor understanding stems from lack of data from early-stage cancers and absence of a well-established premalignant state universal to all ovarian cancer subtypes. Existing evidence suggests that ovarian cancers develop either through a stepwise mutation process (low-grade pathway), through genetic instability resulting in hastened metastasis (high-grade pathway), or more recently through what has been described as the "'fimbrial-ovarian' serous neoplasia theory." In this latter model, ovarian serous cancers evolve from premalignant lesions in the distal fallopian tube called tubal intraepithelial carcinoma. In this manuscript, we review key genetic and molecular changes that occur in cancer cell progression and suggest a model of ovarian cancer pathogenesis involving both tumor cell mutations and microenvironmental factors.

Clinical proteomics of breast cancer

Despite the lifetimes that increased in breast cancers due to the the early screening programs and new therapeutic strategies, many cases still are being lost due to the metastatic relapses. For this reason, new approaches such as the proteomic techniques have currently become the prime objectives of breast cancer researches. Various omic-based techniques have been applied with increasing success to the molecular characterisation of breast tumours, which have resulted in a more detailed classification scheme and have produced clinical diagnostic tests that have been applied to both the prognosis and the prediction of outcome to the treatment. Implementation of the proteomics-based techniques is also seen as crucial if we are to develop a systems biology approach in the discovery of biomarkers of the early diagnosis, prognosis and prediction of the outcome of the breast cancer therapies. In this review, we discuss the studies that have been conducted thus far, for the discovery of diagnostic, prognostic and predictive biomarkers, and evaluate the potential of the discriminating proteins identified in this research for clinical use as breast cancer biomarkers.

Association of telomerase activity with radio- and chemosensitivity of neuroblastomas

BACKGROUND

Telomerase activity compensates shortening of telomeres during cell division and enables cancer cells to escape senescent processes. It is also supposed, that telomerase is associated with radio- and chemoresistance. In the here described study we systematically investigated the influence of telomerase activity (TA) and telomere length on the outcome of radio- and chemotherapy in neuroblastoma.

METHODS

We studied the effects on dominant negative (DN) mutant, wild type (WT) of the telomerase catalytic unit (hTERT) using neuroblastoma cell lines. The cells were irradiated with 60Co and treated with doxorubicin, etoposide, cisplatin and ifosfamide, respectively. Viability was determined by MTS/MTT-test and the GI50 was calculated. Telomere length was measured by southernblot analysis and TA by Trap-Assay.

RESULTS

Compared to the hTERT expressing cells the dominant negative cells showed increased radiosensitivity with decreased telomere length. Independent of telomere length, telomerase negative cells are significantly more sensitive to irradiation. The effect of TA knock-down or overexpression on chemosensitivity were dependent on TA, the anticancer drug, and the chemosensitivity of the maternal cell line.

CONCLUSIONS

Our results supported the concept of telomerase inhibition as an antiproliferative treatment approach in neuroblastomas. Telomerase inhibition increases the outcome of radiotherapy while in combination with chemotherapy the outcome depends on drug- and cell line and can be additive/synergistic or antagonistic. High telomerase activity is one distinct cancer stem cell feature and the here described cellular constructs in combination with stem cell markers like CD133, Aldehyddehydrogenase-1 (ALDH-1) or Side population (SP) may help to investigate the impact of telomerase activity on cancer stem cell survival under therapy.

Applications of tissue microarray technology

Tissue microarrays (TMAs) have become a standard tool for tissue-based research during the last decade. In cancer research, depending on the available data attached to the arrayed tissue, three main types of arrays are commonly manufactured. Prevalence TMAs have no further data available and are suited to estimate the frequency of the occurrence of a particular alteration. Progression arrays include tissues of different stages of disease, and are instrumental to study the role of a marker protein for tumor initiation, progression, or metastatic growth. Prognosis TMAs contain tissues with patient follow-up data. These TMAs are the key to uncover the clinical impact of molecular markers. In combination with normal tissue arrays representing healthy tissues, prevalence, progression, and prognosis TMAs allow for a rapid and comprehensive analysis of molecular markers in human cancers. TMAs are also successfully used for many noncancer applications, such as Alzheimer's or inflammatory disease research.

The alternative lengthening of telomeres phenotype in breast carcinoma is associated with HER-2 overexpression

Approximately 10-15% of human cancers do not show evidence of telomerase activity, and a subset of these maintain telomere lengths by a recombination-based mechanism termed alternative lengthening of telomeres (ALT). The ALT phenotype, relatively common in certain sarcomas and germ cell tumors, is very rare in carcinomas. In this study we describe evidence for the ALT phenotype in molecular subclasses of breast carcinoma, specifically a subset of cancers with HER-2 overexpression. Tissue microarrays were created from 71 invasive ductal carcinomas of the breast categorized into subclasses, and telomere lengths were directly assessed using fluorescence in situ hybridization with combined promyelocytic leukemia (PML) protein immunofluorescence. The ALT phenotype was identified in 3 of 21 HER-2-positive cases, but in none of the other 50 cases (P=0.023). This is the first direct observation of this mechanism of telomere maintenance in breast carcinoma unrelated to Li-Fraumeni syndrome. The correlation of the ALT phenotype with HER-2 positivity, both of which involve abnormal DNA amplification, suggests a possible common underlying mechanism. This telomere phenotype confers a poor prognosis in some cancers; two of the three cases in our study showed rapid tumor progression, possibly suggesting that it may adversely affect outcome in breast carcinoma as well. As cancers using the ALT pathway are predicted to be resistant to therapies based on telomerase inhibition, these results may have therapeutic consequences.

The promise of telomere length, telomerase activity and its regulation in the translocation-dependent cancer ESFT; clinical challenges and utility

The Ewing's sarcoma family of tumours (ESFT) are diagnosed by EWS-ETS gene translocations. The resulting fusion proteins play a role in both the initiation and maintenance of these solid aggressive malignant tumours, suppressing cellular senescence and increasing cell proliferation and survival. EWS-ETS fusion proteins have altered transcriptional activity, inducing expression of a number of different target genes including telomerase. Up-regulation of hTERT is most likely responsible for the high levels of telomerase activity in primary ESFT, although telomerase activity and expression of hTERT are not predictive of outcome. However levels of telomerase activity in peripheral blood may be useful to monitor response to some therapeutics. Despite high levels of telomerase activity, telomeres in ESFT are frequently shorter than those of matched normal cells. Uncertainty about the role that telomerase and regulators of its activity play in the maintenance of telomere length in normal and cancer cells, and lack of studies examining the relationship between telomerase activity, regulators of its activity and their clinical significance in patient samples have limited their introduction into clinical practice. Studies in clinical samples using standardised assays are critical to establish how telomerase and regulators of its activity might best be exploited for patient benefit.

Interaction of current cancer treatments and the immune system: implications for breast cancer therapeutics

Early diagnosis and treatment of breast cancer may account for the current improvement in the mortality of breast cancer. However, achieving a complete 'cure' is the holy grail of cancer medicine and, in many cases, cancer patients still succumb to their ultimate fate. There is therefore a need to devise innovative therapies to overcome this problem. To this end, many emerging therapies utilizing the immune system to eradicate the residues of disease have been described in the preclinical and clinical arenas. However, there is very little work examining the impact of immunotherapy on the existing natural immunity. The relationship between antitumor immunity, in the form of immunotherapy (either passive or active), and current strategies of treatment also needs to be explored. If we are to improve the success of cancer treatment, we must understand how current therapies interact with the immune system and with the emerging immunotherapies. For breast-cancer treatment to be successful, therapeutics should be tailored towards antitumor immunity; they should also avoid tumor-specific tolerance. The sources of information used to prepare this paper were obtained through published work on Pubmed/Medline and materials published on the US/UK governmental agencies' websites.

Cytoplasmic expression of human telomerase catalytic protein (hTERT) in neutrophils: an immunoelectron microscopy study

Human telomerase comprises a catalytic protein subunit (hTERT) and an RNA subunit (hTR). Telomerase extends chromosome ends in compensation for the attrition of the telomeres during replication. In this work, the authors explore the expression of hTERT and hTR in neutrophils, respectively by immunochemistry techniques and in situ hybridization. hTERT was strongly expressed in neutrophils cytoplasm. The ultrastructural study showed that the gold particles were not associated with specific organelles but scattered in the cytosol. hTR was not expressed. hTERT is expressed in the cytoplasm of neutrophils, but its roles-eventually extratelomeric effects-remain to be elucidated.

Breast tumor metastasis: analysis via proteomic profiling

The ability to predict the metastatic behavior of a patient's cancer, as well as to detect and eradicate such recurrences, remain major clinical challenges in oncology. While many potential molecular biomarkers have been identified and tested previously, none have greatly improved the accuracy of specimen evaluation over routine histopathological criteria and, to date, they predict individual outcomes poorly. The ongoing development of high-throughput proteomic profiling technologies is opening new avenues for the investigation of cancer and, through application in tissue-based studies and animal models, will facilitate the identification of molecular signatures that are associated with breast tumor cell phenotype. The appropriate use of these approaches has the potential to provide efficient biomarkers, and to improve our knowledge of tumor biology. This, in turn, will enable the development of targeted therapeutics aimed at ameliorating the lethal dissemination of breast cancer. In this review, we focus on the accumulating proteomic signatures of breast tumor progression, particularly those that correlate with the occurrence of distant metastases, and discuss some of the expected future developments in the field.

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.

Clinical proteomics and breast cancer: strategies for diagnostic and therapeutic biomarker discovery

A major challenge of breast cancer research is the identification of accurate biomarkers that improve screening, early diagnosis, prediction of aggressiveness, and prediction of therapeutic response or toxicity, as well as the identification of new molecular therapeutic targets. The new proteomic techniques promise to be valuable for identifying such tissue and serum markers. The different techniques currently applied to clinical samples of breast cancer and the most important results obtained are summarized in this review.

Early Events in the Pathogenesis of Epithelial Ovarian Cancer

Ovarian carcinogenesis, as in most cancers, involves multiple genetic alterations. A great deal has been learned about proteins and pathways important in the early stages of malignant transformation and metastasis, as derived from studies of individual tumors, microarray data, animal models, and inherited disorders that confer susceptibility. However, a full understanding of the earliest recognizable events in epithelial ovarian carcinogenesis is limited by the lack of a well-defined premalignant state common to all ovarian subtypes and by the paucity of data from early-stage cancers. Evidence suggests that ovarian cancers can progress both through a stepwise mutation process (low-grade pathway) and through greater genetic instability that leads to rapid metastasis without an identifiable precursor lesion (high-grade pathway). In this review, we discuss many of the genetic and molecular disorders in each key process that is altered in cancer cells, and we present a model of ovarian pathogenesis that incorporates the role of tumor cell mutations and factors in the host microenvironment important to tumor initiation and progression.

The expression of gene transcripts of telomere-associated genes in human breast cancer: correlation with clinico-pathological parameters and clinical outcome

BACKGROUND

Telomerase is a ribonucleoprotein enzyme that synthesises telomeres in human germ cells, embryogenesis and in cancer, maintaining chromosomal length, stability and cellular immortality. The hTERT gene is the rate-limiting determinant of telomerase reactivation during immortalization and malignant transformation. Telomeric DNA-binding proteins have been attracting increasing interest due to their essential role in the regulation of telomeric DNA length and in protecting against chromosomal end-to-end fusion. These proteins include hTR, TRF1, TRF2, TANK1, TANK2, POT1, TIN2, EST1, and TEP. This study represents the first comprehensive investigation of the mRNA expression of key telomere-related genes in human breast cancer.

METHODS

One hundred and twenty seven tumour tissues and 33 normal tissues were analyzed. Levels of transcription of hTERT, hTR, TRF1, TRF2, TANK1, TANK2, POT1, TIN2, EST1, and TEP1 were determined using real-time quantitative PCR. The mRNA expression of these genes was normalized against CK19 and was then analyzed against the pathological parameters and clinical outcome over a 10 year follow up period.

RESULTS

The mRNA expressions of hTERT, hTR, TANK1, EST1, and TEP1 were higher in tumour samples compared with normal breast tissue. This reached statistical significance for EST1 when comparing good prognosis tumours with normal breast tissue (means=11013 vs 1160, P=0.05). Both hTERT and TEP1 levels significantly predicted overall survival (P=0.012 and 0.005 respectively) and disease-free survival (P=0.0011 and 0.01 respectively). The mRNA levels of TANK2 and POT1 were lower in malignant tissues compared with non-malignant breast tissues and this difference reached statistical significance when comparing the levels in normal tissues with those in advanced tumours (P=0.0008 and P=0.038 respectively). Their levels fell further with increasing tumour's stage and were higher in tumours from patients who remained disease free compared with those who developed local recurrence or distant metastasis or died from breast cancer.TRF2 showed a trend similar to that of TANK2 and POT1. Furthermore, there was a highly significant correlation between TANK1 expression and that of hTERT, hTR, TRF1, TRF2 and EST1, (r=0.533, 0.586, 0.608, 0.644 and 0.551 respectively, P<0.001).

CONCLUSIONS

Genes encoding telomere-associated proteins display different patterns of mRNA expression in human breast cancer, and in normal breast tissue, suggesting different and sometimes opposing roles in mammary carcinogenesis. hTERT, hTR, TANK1, EST1 and TEP1 seem to be up-regulated, with hTERT and TEP1 correlating with clinical outcome. Conversely, TANK2 and POT1 transcription levels demonstrate a compelling trend to be lower in malignant tissues and lower still in those patients who develop recurrent disease suggesting that TANK2 and POT1 may act as tumour suppressor genes possibly by negatively regulating telomerase activity.

Telomere biology of pediatric cancer

One of the hallmarks of cancer is limitless proliferative capacity, which is tightly associated with the ability to maintain telomeres. Over the last decade, the telomere biology of pediatric cancers has begun to be elucidated. Most pediatric leukemias and embryonal solid tumors activate the enzyme telomerase, a specialized reverse transcriptase that adds nucleotide repeats to telomeres. In general, high levels of tumor telomerase expression are associated with unfavorable outcome, although results vary according to tumor type. Some pediatric tumors, including osteosarcoma and glioblastoma multiforme, lack telomerase activity and maintain telomeres via a recombination-based mechanism called ALT (alternative lengthening of telomeres). Telomerase is a highly attractive therapeutic target for pediatric cancer because the enzyme plays a key role in conferring cellular immortality, is present in most tumors, and is relatively specific for cancer cells. Telomerase inhibitors have been evaluated in preclinical models of adult cancers, but few studies have been conducted on pediatric cancers. Further research is required to define how telomere biology can be used to clinical advantage in malignancies of childhood.