Telomere length and telomerase subunits as diagnostic and prognostic biomarkers in Barrett carcinoma

Association of leukocyte telomere length with the risk of digestive diseases: A large-scale cohort study

BACKGROUND

Leukocyte telomere length (LTL) shortening, a biomarker of telomere attrition, has been linked to multiple diseases. However, the relationship between LTL and digestive diseases remains uncertain. This study aimed to investigate the association between LTL and the risk of digestive diseases.

METHODS

A cohort analysis of over 500,000 participants from the UK Biobank (UKB) between 2006 and 2021 was conducted to estimate the associations of LTL with more than 90 common digestive diseases. LTL was quantified using multiplex quantitative polymerase chain reaction, and cases of each disease were determined according to inpatient and primary care data. Multivariable Cox proportional hazards regression analysis was used to evaluate the associations of LTL with the risk of digestive diseases. Furthermore, such associations were also evaluated after stratification by sex and ethnicity.

RESULTS

After a mean follow-up time of 11.8 years, over 20 International Classification of Diseases, 10th Revision ( ICD-10 ) codes were showed to be associated with telomere attrition. LTL shortening is associated with an increased risk of several digestive diseases, including gastroesophageal reflux disease (K21: hazard ratio [HR] = 1.30, 95% confidence interval [95% CI]: 1.19-1.42), esophageal ulcer (K221: HR = 1.81, 95% CI: 1.22-2.71), Barrett's esophagus (K227: HR = 1.58, 95% CI: 1.14-2.17), gastritis (K29: HR = 1.39, 95% CI: 1.26-1.52), duodenal ulcer (K26: HR = 1.55, 95% CI: 1.14-2.12), functional dyspepsia (K30X: HR = 1.36, 95% CI: 1.06-1.69), non-alcoholic fatty liver disease (NAFLD) (K760: HR = 1.39, 95% CI: 1.09-1.78), liver cirrhosis (K74: HR = 4.73, 95% CI: 3.27-6.85), cholangitis (K830: HR = 2.55, 95% CI: 1.30-5.00), and hernia (K43: HR = 1.50, 95% CI: 1.17-1.94; K44: HR = 1.29, 95% CI: 1.17-1.42). The risk of rectal polyps (K621: HR = 0.77, 95% CI: 0.63-0.92) decreased per unit shortening of LTL.

CONCLUSIONS

This study suggests that LTL shortening is associated with an increased risk of most digestive diseases except for rectal polyps. These findings may provide some clues for understanding the pathogenesis of digestive diseases.

Distinct telomere length and molecular signatures in seminoma and non-seminoma of testicular germ cell tumor

Testicular germ cell tumors (TGCTs) are classified into two main subtypes, seminoma (SE) and non-seminoma (NSE), but their molecular distinctions remain largely unexplored. Here, we used expression data for mRNAs and microRNAs (miRNAs) from The Cancer Genome Atlas (TCGA) to perform a systematic investigation to explain the different telomere length (TL) features between NSE (n = 48) and SE (n = 55). We found that TL elongation was dominant in NSE, whereas TL shortening prevailed in SE. We further showed that both mRNA and miRNA expression profiles could clearly distinguish these two subtypes. Notably, four telomere-related genes (TelGenes) showed significantly higher expression and positively correlated with telomere elongation in NSE than SE: three telomerase activity-related genes (TERT, WRAP53 and MYC) and an independent telomerase activity gene (ZSCAN4). We also found that the expression of genes encoding Yamanaka factors was positively correlated with telomere lengthening in NSE. Among them, SOX2 and MYC were highly expressed in NSE versus SE, while POU5F1 and KLF4 had the opposite patterns. These results suggested that enhanced expression of both TelGenes (TERT, WRAP53, MYC and ZSCAN4) and Yamanaka factors might induce telomere elongation in NSE. Conversely, the relative lack of telomerase activation and low expression of independent telomerase activity pathway during cell division may be contributed to telomere shortening in SE. Taken together, our results revealed the potential molecular profiles and regulatory roles involving the TL difference between NSE and SE, and provided a better molecular understanding of this complex disease.

Telomere Length of Circulating Cell-Free DNA and Gastric Cancer in a Chinese Population at High-Risk

Background: Telomeres have long been found to be involved in cancer development, while little was known about the dynamic changes of telomere length in carcinogenesis process.

Methods: The present study longitudinally investigated telomere alterations of cell-free DNA (cfDNA) in 86 gastric cancer (GC) subjects recruited through a 16-year prospective cohort with 2–4 serums collected before each GC-diagnosis from baseline and three follow-up time-points (a total of 276 samples). As the control, 86 individual-matched cancer-free subjects were enrolled with 276 serums from the matched calendar year.

Results: In the 73 pairs of baseline serums from GC and control subjects, shortened telomeres showed increased subsequent GC risk [odds ratio (OR) = 9.17, 95% CI: 2.72–31.25 for 1 unit shortening]. In each baseline gastric lesion category, higher risks of GC progression were also found with shortened cfDNA telomeres; ORs per 1 unit shortening were 6.99 (95% CI: 1.63–30.30) for mild gastric lesions, 6.06 (95% CI: 1.89–19.61) for intestinal metaplasia and 15.63 (95% CI: 1.91–125.00) for dysplasia. With all measurements from baseline and follow-up time-points, shortened telomeres also showed significant association with GC risk (OR = 7.37, 95% CI: 2.06–26.32 for 1 unit shortening). In temporal trend analysis, shortened telomeres were found in GC subjects compared to corresponding controls more than 3 years ahead of GC-diagnosis (most P < 0.05), while no significant difference was found between two groups within 3 years approaching to GC-diagnosis.

Conclusion: Our findings suggest that telomere shortening may be associated with gastric carcinogenesis, which supports further etiological study and potential biomarker for risk stratification.

Telomeres and Telomerase During Human Papillomavirus-Induced Carcinogenesis

Human papillomaviruses (HPVs) belong to a small spherical virus family and are transmitted through direct contact, most often through sexual behavior. More than 200 types of HPV are known, a dozen or so of which are classified as high-risk viruses (HR HPV) and may contribute to the development of cervical cancer. HPV is a small virus with a capsid composed of L1 and L2 proteins, which are crucial for entry to the cell. The infection begins at the basal cell layer and progresses to involve cells from higher layers of the cervical epithelium. E6 and E7 viral proteins are involved in the process of carcinogenesis. They interact with suppressors of oncogenesis, including p53 and Rb proteins. This leads to DNA replication and intensive cell divisions. The persistent HR HPV infection leads to the development of dysplasia and these changes may progress to invasive cancer. During the initial stage of carcinogenesis, telomeres shorten until telomerase activates. The activation of telomerase, the enzyme necessary to extend chromosome ends (telomeres) is the key step in cell immortalization. Analyzing the expression level of hTERT and hTERC genes encoding telomerase and telomere length measurement may constitute new markers of the early carcinogenesis.

Telomeropathies: rare disease syndromes

Telomeres are located at the end of the chromosomes. They protect chromosomes from fusion and degradation. Every cell division causes a shortening of the telomeres. A special enzymatic complex called telomerase is responsible for maintaining telomere length in intensively dividing cells, such as epithelial cells and bone marrow cells. The enzymatic complex includes the TERT subunit, which has reverse transcriptase activity, and the TERC subunit, which acts as a template. Other important components of telomerase are the proteins that are responsible for structural stability. Telomerase remains active only in the dividing cells of the body. The rate of telomere shortening depends on many factors including age, sex, and comorbidities. Faster shortening of telomeres is caused by gene defects, which have an impact on telomerase action. Collectively, these are called telomeropathies. Common causes of telomeropathies are mutations in the TERT and TERC telomerase genes. Types of telemeropathies include dyskeratosis congenita, idiopathic pulmonary fibrosis, and aplastic anaemia, among others. Clinical manifestations and prognoses depend on the type and quantity of mutated genes. Diagnosis of telomeropathies is often problematic because they present with the same symptoms as other diseases. So far, no effective therapeutic methods have been developed for telomeropathies. A therapeutic method for patients with bone marrow failure may be the transplantation of hematopoietic stem cells. For patients with idiopathic pulmonary fibrosis, treatments include immunosuppressive therapy, lung transplantation, or palliative care. In the future, gene therapy may be an effective treatment strategy for telomeropathies. Lifestyle changes may also have a positive impact on the person. Physical activity combined with a healthy diet rich in antioxidants and unsaturated fatty acids can decrease the oxidative stress levels in cells and lead to a slower shortening of the telomeres.

Telomeres as a molecular marker of male infertility

In recent years, male infertility has become a growing social problem. Standard diagnostic procedures, based on assessing seminological parameters, are often insufficient to explain the causes of male infertility. Because of this, new markers with better clinical application are being sought. One of the promising markers seems to be an assessment of telomere length of sperm. Sperm telomeres, in contrast to somatic cells, are elongated as men age. The results of some studies suggest that telomere length may be relevant in the case of fertilization and normal embryo development. Literature reports indicate that there is a correlation between telomere length of sperm and abnormal sperm parameters. The measurement of telomere length using the method of quantitative PCR could become a new marker of spermatogenesis, which can be useful for evaluating male reproductive age.

Prognostic role of telomere length in malignancies: A meta-analysis and meta-regression

Telomere length (TL) has been associated with several health conditions including cancer. To quantify the effect of TL on outcomes in malignancies and explore the role of type of TL measurement we conducted a librarian-led systematic search of electronic databases identified publications exploring the prognostic role of TL on cancer outcomes. Overall survival (OS) was the primary outcome measure while other time-to-event endpoints were secondary outcomes. Data from studies reporting a hazard ratio (HR) with 95% confidence interval (CI) and/or p-value were pooled in a meta-analysis. HRs were weighted by generic inverse variance and computed by random effects modeling. All statistical tests were two-sided. Sixty-one studies comprising a total of 14,720 patients were included of which 41 (67%) reported OS outcomes. Overall, the pooled HR for OS was 0.88 (95%CI=0.69-1.11, p=0.28). Long (versus short) telomeres were associated with improved outcomes in chronic lymphatic leukemia (CLL) and urothelial cancer (HR=0.45, 95%CI=0.29-0.71 and HR=0.68, 95%CI=0.46-1.00, respectively), conversely worse OS was seen with hepatocellular carcinoma (HR=1.90, 95%CI=1.51-2.38). Pooled HRs (95% CI) for progression-free survival, relapse/disease-free survival, cancer-specific survival, and treatment-free survival were 0.56 (0.41-0.76), 0.76 (0.53-1.10), 0.72 (0.48-1.10), and 0.48 (0.39-0.60), respectively. There was substantial heterogeneity of tissues and methods used for TL measurement and no clear association between TL and outcome was identified in subgroups. In conclusion, there is inconsistent effect of TL on cancer outcomes possibly due to variable methods of measurement. Standardization of measurement and reporting of TL is warranted before the prognostic value of TL can be accurately assessed.

Long telomere length predicts poor clinical outcome in esophageal cancer patients

BACKGROUND

Abnormal telomere length is widely reported in various human cancers, and it is considered to be an important hallmark of cancer. However, there is remarkably little consensus on the value of telomere length in the prognostic evaluation of esophageal cancers. Here, we attempted to determine the association of variable telomere length with clinical outcome of esophageal cancer patients.

MATERIALS AND METHODS

Using real-time quantitative PCR, we examined relative telomere lengths (RTL) in a cohort of esophageal cancer and normal esophageal tissues, and statistically investigated the association between RTL and clinical outcomes of esophageal cancer patients.

RESULTS

The majority of esophageal cancers in this study had longer RTLs as compared to adjacent non-tumor tissues. Enhanced tumor RTL was associated with smoking habit, poor differentiation, advanced tumor stage, lymph node metastasis and cancer related death. In particular, a close relationship between longer RTL and poor survival was fully demonstrated by using cox regression and Kaplan-Maier survival curves.

CONCLUSIONS

We found frequent telomere elongation in esophageal cancer tissues, and demonstrated longer RTL may be an independent poor prognostic factor for esophageal cancer patients.

Overview of major molecular alterations during progression from Barrett's esophagus to esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) develops in the sequential transformation of normal epithelium into metaplastic epithelium, called Barrett's esophagus (BE), then to dysplasia, and finally cancer. BE is a common condition in which normal stratified squamous epithelium of the esophagus is replaced with an intestine-like columnar epithelium, and it is the most prominent risk factor for EAC. This review aims to impartially systemize the knowledge from a large number of publications that describe the molecular and biochemical alterations occurring over this progression sequence. In order to provide an unbiased extraction of the knowledge from the literature, a text-mining methodology was used to select genes that are involved in the BE progression, with the top candidate genes found to be TP53, CDKN2A, CTNNB1, CDH1, GPX3, and NOX5. In addition, sample frequencies across analyzed patient cohorts at each stage of disease progression are summarized. All six genes are altered in the majority of EAC patients, and accumulation of alterations correlates well with the sequential progression of BE to cancer, indicating that the text-mining method is a valid approach for gene prioritization. This review discusses how, besides being cancer drivers, these genes are functionally interconnected and might collectively be considered a central hub of BE progression.

Association between telomere length and survival in cancer patients: a meta-analysis and review of literature

The relationship between telomere length and cancer survival has been widely studied. To gain a deeper insight, we reviewed the published studies. A total of 29 studies evaluated telomere length in the peripheral blood; 22 studies evaluated telomere length in the tumor tissue. First, in the peripheral blood studies, for solid tumor patients with shortened telomere length, the combined hazard ratios (HRs) for mortality and tumor progression were 1.21 (95%CI, 1.10-1.32) and 1.71 (95%CI, 1.37-2.13), respectively. Meanwhile, in hematology malignancy, the combined HRs for mortality and tumor progression were 2.83 (95%CI, 2.14-3.74) and 2.65 (95%CI, 2.18-3.22), respectively. Second, in the studies that use tumor tissue, for patients with shortened telomeres, the combined HRs for mortality and tumor progression were 1.26 (95%CI, 0.95-1.66) and 1.65 (95%CI, 1.26-2.15), respectively. In the studies that calculate the telomere length ratios of tumor tissue to adjacent normal mucosa, for patients with lower telomere length ratios, the combined HRs were 0.66 (95%CI, 0.53-0.83) and 0.74 (95%CI, 0.41-1.32) for mortality and tumor progression, respectively. In conclusion, shortened telomere in peripheral blood and tumor tissue might indicate poor survival for cancer patients. However, by calculating the telomere length ratios of tumor tissue to adjacent normal mucosa, the lower ratio might indicate better survival.

Preanalytical Conditions and DNA Isolation Methods Affect Telomere Length Quantification in Whole Blood

Telomeres are located at chromosome ends and their length (TL) has been associated with aging and human diseases such as cancer. Whole blood DNA is frequently used for TL measurements but the influence of preanalytical conditions and DNA isolation methods on TL quantification has not been thoroughly investigated. To evaluate potential preanalytical as well as methodological bias on TL, anonymized leftover EDTA-whole blood samples were pooled according to leukocyte counts and were incubated with and without actinomycin D to induce apoptosis as a prototype of sample degradation. DNA was isolated from fresh blood pools and after freezing at -80°C. Commercially available kits using beads (Invitrogen), spin columns (Qiagen, Macherey-Nagel and 5prime) or precipitation (Stratec/Invisorb) and a published isopropanol precipitation protocol (IPP) were used for DNA isolation. TL was assessed by qPCR, and normalized to the single copy reference gene 36B4 using two established single-plex and a new multiplex protocol. We show that the method of DNA isolation significantly affected TL (e.g. 1.86-fold longer TL when comparing IPP vs. Invitrogen). Sample degradation led to an average TL decrease of 22% when using all except for one DNA isolation method (5prime). Preanalytical storage conditions did not affect TL with exception of samples that were isolated with the 5prime kit, where a 27% increase in TL was observed after freezing. Finally, performance of the multiplex qPCR protocol was comparable to the single-plex assays, but showed superior time- and cost-effectiveness and required > 80% less DNA. Findings of the current study highlight the need for standardization of whole blood processing and DNA isolation in clinical study settings to avoid preanalytical bias of TL quantification and show that multiplex assays may improve TL/SCG measurements.

Targeting chemokine pathways in esophageal adenocarcinoma

Esophageal adenocarcinoma (EAC) is one of the fastest growing malignancies in the US and needs newer therapeutic and diagnostic strategies. Chronic inflammation plays a role in the pathogenesis of EAC and contributes to the dysplastic conversion of normal esophageal epithelium to Barrett's esophagus and frank adenocarcinoma. Chemokines play important roles in mediating inflammation and recent evidence implicates these ligands and their receptors in the development and spread of various tumors. We demonstrated that the chemokines IL8, CXCL1 and CXCL3 are significantly overexpressed during esophageal carcinogenesis and accompanied by amplification and demethylation of the chr4q21 gene locus. We also demonstrated that IL8 levels can be detected in serum of patients with EAC and can serve as potential biomarkers. We now demonstrate that inhibition of IL8 receptor, CXCR2, leads to decreased invasiveness of esophageal adenocarcinoma derived cells without affecting cellular proliferation. Taken together, these studies reveal the important roles that chemokines play in development of esophageal cancer and demonstrate that these pathways can serve as potential therapeutic targets.

The Association between Telomere Length and Cancer Prognosis: Evidence from a Meta-Analysis

BACKGROUND

Telomeres are essential for chromosomal integrity and stability. Shortened telomere length (TL) has been associated with risk of cancers and aging-related diseases. Several studies have explored associations between TL and cancer prognosis, but the results are conflicting.

METHODS

Prospective studies on the relationship between TL and cancer survival were identified by a search of PubMed up to May 25, 2015. There were no restrictions on the cancer type or DNA source. The quality of the included studies was assessed using the Newcastle-Ottawa Scale. Meta-analysis approaches were conducted to determine pooled relative risks and 95% confidence intervals.

RESULTS

Thirty-three articles containing forty-five independent studies were ultimately involved in our meta-analysis, of which twenty-seven were about overall cancer survival and eighteen were about cancer progression. Short TL was associated with increased cancer mortality risk (RR = 1.30, 95%CI: 1.06-1.59) and poor cancer progression (RR = 1.44, 95%CI: 1.10-1.88), both with high levels of heterogeneity (I2 = 83.5%, P = 0.012for overall survival and I2 = 75.4%, P = 0.008 for progression). TL was an independent predictor of overall cancer survival and progression in chronic lymphocytic leukemia. Besides, short telomeres were also associated with increased colorectal cancer mortality and decreased overall survival of esophageal cancer, but not in other cancers. Cancer progression was associated with TL in Asian and America populations and short TL predicted poor cancer survival in older populations. Compared with tumor tissue cells, TL in blood lymphocyte cells was better for prediction. In addition, the associations remained significant when restricted to studies with adjustments for age, with larger sample sizes, measuring TL using southern blotting or estimating risk effects by hazard ratios.

CONCLUSION

Short TL demonstrated a significant association with poor cancer survival, suggesting the potential prognostic significance of TL. Additional large well-designed studies are needed to confirm our findings.

Keeping those telomeres short! an innovative intratumoral long-term drug delivery system

BACKGROUND

Telomerase activation and an alternative lengthening of telomeres (ALT) mechanism are two telomere-lengthening cancer cell survival mechanisms elicited by both chemo- and/or radiotherapy. Telomere lengthening interferes with cell lethality and results in the immortalization of cancer cells. To counteract these mechanisms, we developed a drug delivery system (DDS) consisting of a polymeric implant that is inserted directly into tumors. The DDS releases, continuously and gradually, a cationic porphyrin (PdTMPyP4) for >30 days after a single application, and inhibits telomerase activation.

METHODS

The PdTMPyP4 porphyrin is incorporated into a poly(co-glycolic lactic)acid (PLGA) polymer, solidified and cut into small rods. PdTMPyP4 release from the rods was measured spectrophotometrically over time. Uptake of Pd in the DNA of in L428 Hodgkins lymphoma cells was measured by ICP-MS, and telomerase activation by the TRAP assay. The rods were placed into the growth medium of cells whose growth rate was measured for 11 and 19 days. The cylinders were also inserted directly into KHJJ murine mammary tumors borne on the thighs of BALB/c mice and the tumor growth rate measured.

RESULTS

In vitro, >10(9)Pd atoms were measured in the DNA of each L428 cell and telomerase activity was reduced by ~15% within 24 h. A one-time application of the rod in the cell medium induced a factor of >5 greater lethality compared to a blank rod or untreated controls. In vivo, a one-time insertion of the rod into tumors resulted in the retardation of the growth rate by factors of 3-5 compared to untreated controls. Systemic uptake after intratumoral insertion of the rod was negligible.

CONCLUSION

The results suggest that the direct intratumoral insertion of a PdTMPyP4-containing polymeric rod would be of benefit as an adjuvant treatment for patients undergoing chemo- or radiotherapy. By preventing the lengthening of telomeres and therefore the unrestricted growth of cancer cells, our DDS will provide a significant therapeutic advantage to these treatments without affecting normal tissues.

Biomarkers of Barrett's esophagus

Barrett's esophagus is the strongest risk for esophageal adenocarcinoma (EAC). Metaplasia in patients with BE may progress to dysplasia and then invasive carcinoma. Well-defined diagnostic, progressive, predictive, and prognostic biomarkers are needed to identify the presence of the disease, estimate the risk of malignant transformation, and predict the therapeutic outcome and survival of EAC patients. There are many predictive and prognostic markers that lack substantial validation, and do not allow stratification of patients with gastroesophageal reflux disease in clinical practice for outcome and effectiveness of therapy. In this short review we summarize the current knowledge regarding possible biomarkers, focusing on the pathophysiologic mechanisms to improve prognostic and therapeutic approaches.

Bone marrow failure and the telomeropathies

Our understanding of the pathophysiology of aplastic anemia is undergoing significant revision, with implications for diagnosis and treatment. Constitutional and acquired disease is poorly delineated, as lesions in some genetic pathways cause stereotypical childhood syndromes and also act as risk factors for clinical manifestations in adult life. Telomere diseases are a prominent example of this relationship. Accelerated telomere attrition is the result of mutations in telomere repair genes and genes encoding components of the shelterin complex and related proteins. Genotype-phenotype correlations show genes responsible for X-linked (DKC1) and severe recessive childhood dyskeratosis congenita, typically with associated mucocutaneous features, and others (TERC and TERT) for more subtle presentation as telomeropathy in adults, in which multiorgan failure may be prominent. Telomerase mutations also are etiologic in familial pulmonary fibrosis and cryptic liver disease. Detection of a telomere disease requires awareness in the clinic, appropriate laboratory testing of telomere content, and genetic sequencing. In treatment decisions, genetic screening of related donors for hematopoietic stem cell transplantation is critical, and androgen therapy may be helpful. Telomeres shorten normally with aging, as well as under environmental circumstances, with regenerative stress and oxidative damage. Telomere biology is complexly related to oncogenesis: telomere attrition is protective by enforcing senescence or apoptosis in cells with a long mitotic history, but telomere loss also can destabilize the genome by chromosome rearrangement and aneuploidy.

A systematic review and meta-analysis of somatic and germline DNA sequence biomarkers of esophageal cancer survival, therapy response and stage

Recent advances in next generation sequencing reinforce the potential for DNA sequence markers to guide esophageal cancer management. We report the first systematic review and meta-analysis, identifying 94 markers of outcome and 41 of stage. Overall, evidence was poor. Meta-analyses demonstrated outcome associations for 6 tumor and 9 germline variants: priorities for prospective evaluation.

Introduction

There is an urgent need for biomarkers to help predict prognosis and guide management of esophageal cancer. This review identifies, evaluates and meta-analyses the evidence for reported somatic and germline DNA sequence biomarkers of outcome and stage.

Methods

A systematic review was carried out of the PubMed, EMBASE and Cochrane databases (20 August 2014), in conjunction with the ASCO Level of Evidence scale for biomarker research. Meta-analyses were carried out for all reported markers associated with outcome measures by more than one study.

Results

Four thousand and four articles were identified, 762 retrieved and 182 studies included. There were 65 reported markers of survival or recurrence 12 (18.5%) were excluded due to multiple comparisons. Following meta-analysis, significant associations were seen for six tumor variants (mutant TP53 and PIK3CA, copy number gain of ERBB2/HER2, CCND1 and FGF3, and chromosomal instability/ploidy) and seven germline polymorphisms: ERCC1 rs3212986, ERCC2 rs1799793, TP53 rs1042522, MDM2 rs2279744, TYMS rs34743033, ABCB1 rs1045642 and MTHFR rs1801133. Twelve germline markers of treatment complications were reported; 10 were excluded. Two tumor and 15 germline markers (11 excluded) of chemo (radio)therapy response were reported. Following meta-analysis, associations were demonstrated for mutant TP53, ERCC1 rs11615 and XRCC1 rs25487. There were 41 tumor/germline reported markers of stage; 27 (65.9%) were excluded.

Conclusions

Numerous DNA markers of outcome and stage have been reported, yet few are backed by high-quality evidence. Despite this, a small number of variants appear reliable. These merit evaluation in prospective trials, within the context of high-throughput sequencing and gene expression.

Molecular biomarkers in esophageal, gastric, and colorectal adenocarcinoma

Cancers of the esophagus, stomach and colon contribute to a major health burden worldwide and over 20% of all cancer deaths. Biomarkers that should indicate pathogenic process and are measureable in an objective manner for these tumors are rare and not established in the clinical setting. In general biomarkers can be very useful for cancer management as they can improve clinical decision-making regarding diagnosis, surveillance, and therapy. Biomarkers can be different types of molecular entities (such as DNA, RNA or proteins), which can be detected, in different tissues or body fluids. However, more important is the type of biomarker itself, which allows diagnostic, prognostic or predictive analyses for different clinical problems. This review aims to systematically summarize the recent findings of genetic and epigenetic markers for gastrointestinal tumors within the last decade. While many biomarkers seem to be very promising, especially if used as panels, further development is urgently needed to address practical considerations of biomarkers in cancer treatment.

Oxidative DNA damage in Barrett mucosa: correlation with telomeric dysfunction and p53 mutation

BACKGROUND

Barrett esophagus develops in a scenario of chronic inflammation, linked to free radical formation and oxidative DNA damage. Eight-hydroxydeoxyguanosine, the main oxidative DNA adduct, is partially repaired by a glycosylase (OGG1) whose polymorphism is associated to a reduced repair capacity. Telomeres are particularly prone to oxidative damage, which leads to shortening and cell senescence, while elongation, by telomerase activity, is linked to cell immortalization and cancer. Limited data are available on this point with respect to Barrett esophagus. This study aimed to evaluate the link among 8-hydroxydeoxyguanosine, OGG1 polymorphism, telomerase activity, telomere length, and p53 mutation in Barrett progression.

METHODS

Forty consecutive patients with short- and long-segment Barrett esophagus and 20 controls with gastroesophageal reflux disease without Barrett esophagus were recruited. Analysis of biopsy samples was undertaken to study 8-hydroxydeoxyguanosine levels, OGG1 polymorphism, telomerase activity, and telomere length. Serum samples were obtained for p53 mutation.

RESULTS

Controls had significantly lower levels of 8-hydroxydeoxyguanosine and telomerase activity, with normal telomere length and no p53 mutation. In short-segment Barrett esophagus, 8-hydroxydeoxyguanosine levels were higher and telomeres underwent significant shortening, with stimulation of telomerase activity but no p53 mutations. In long-segment Barrett esophagus, 8-hydroxydeoxyguanosine reached maximal levels, with telomere elongation, and 42 % of the patients showed p53 mutation.

CONCLUSIONS

In Barrett patients, with disease progression, oxidative DNA damage accumulates, causing telomere instability, telomerase activation, and, in a late phase, mutations in the p53 gene, thus abrogating its activity as the checkpoint of proliferation and apoptosis, and facilitating progression to cancer.

GERD-Barrett-Adenocarcinoma: Do We Have Suitable Prognostic and Predictive Molecular Markers?

Due to unfavorable lifestyle habits (unhealthy diet and tobacco abuse) the incidence of gastroesophageal reflux disease (GERD) in western countries is increasing. The GERD-Barrett-Adenocarcinoma sequence currently lacks well-defined diagnostic, progressive, predictive, and prognostic biomarkers (i) providing an appropriate screening method identifying the presence of the disease, (ii) estimating the risk of evolving cancer, that is, the progression from Barrett's esophagus (BE) to esophageal adenocarcinoma (EAC), (iii) predicting the response to therapy, and (iv) indicating an overall survival—prognosis for EAC patients. Based on histomorphological findings, detailed screening and therapeutic guidelines have been elaborated, although epidemiological studies could not support the postulated increasing progression rates of GERD to BE and EAC. Additionally, proposed predictive and prognostic markers are rather heterogeneous by nature, lack substantial proofs, and currently do not allow stratification of GERD patients for progression, outcome, and therapeutic effectiveness in clinical practice. The aim of this paper is to discuss the current knowledge regarding the GERD-BE-EAC sequence mainly focusing on the disputable and ambiguous status of proposed biomarkers to identify promising and reliable markers in order to provide more detailed insights into pathophysiological mechanisms and thus to improve prognostic and predictive therapeutic approaches.

Methylation of the hTERT promoter: a novel cancer biomarker for leptomeningeal metastasis detection in cerebrospinal fluids

PURPOSE

The diagnosis of leptomeningeal metastases is usually confirmed by the finding of malignant cells by cytologic examination in the cerebrospinal fluid (CSF). More sensitive and specific cancer biomarkers may improve the detection of tumor cells in the CSF. Promoter methylation of the human telomerase reverse transcriptase (hTERT) gene characterizes most cancer cells. The aim of this study was to develop a sensitive method to detect hTERT methylation and to explore its use as a cancer biomarker in CSF.

EXPERIMENTAL DESIGN

In 77 CSF specimens from 67 patients, hTERT promoter methylation was evaluated using real-time methylation-sensitive high-resolution melting (MS-HRM) and real-time TaqMan PCR and MS-HRM in a single-tube assay.

RESULTS

Real-time MS-HRM assay was able to detect down to 1% hTERT-methylated DNA in a background of unmethylated DNA. PCR products were obtained from 90% (69/77) of CSF samples. No false positive hTERT was detected in the 21 non-neoplastic control cases, given to the method a specificity of 100%. The sensitivity of the real-time MS-HRM compared with the cytologic gold standard analysis was of 92% (11/12). Twenty-six CSFs from 22 patients with an hTERT-methylated primary tumor showed cytologic results suspicious for malignancy; in 17 (65%) of them, a diagnosis of leptomeningeal metastases could be confirmed by the hTERT methylation test.

CONCLUSION

The hTERT real-time MS-HRM approach is fast, specific, sensitive, and could therefore become a valuable tool for diagnosis of leptomeningeal metastases as an adjunct to the traditional examination of CSF.

Prevalence and pathogenesis of Barrett's esophagus in Luoyang, China

BACKGROUND

Prevalence of Barrett's esophagus (BE) in Luoyang, China, has not been reported, and its pathogenesis is controversial. The aim of this study was therefore to investigate the prevalence of BE and its underlying factors in the city of Luoyang.

METHOD

This was a prospective study in one center. Many patients were analyzed using endoscopy who showed upper gastrointestinal symptoms between August 2006 and June 2007. In addition, the effect of apoptosis-related proteins and heat shock proteins upon BE's pathogenesis were also investigated by an immunohistochemical protocol.

RESULTS

Prevalence of BE was at 4.55% and the mean age of those affected was about 10 years older than for esophagitis. Typical reflux symptoms were significantly lower than with esophagitis, whereas signs of caspase-3 and HSP105 elevation were significantly higher. Expression of TERT, HSP70 and HSP90α in BE cases was significantly lower than in esophagitis. However, there was no statistical difference between the two groups in expression of HSP27.

CONCLUSIONS

The prevalence of BE is high in Luoyang, which could result from esophagitis despite typical reflux symptoms being relatively uncommon. Initiation and development of BE might be the result of accelerated proliferation, apoptosis and differentiation of original cells to intestinal epithelium.

Inflammation and Barrett's carcinogenesis

Barrett's esophagus (BE) is one of the most common premalignant lesions in which normal squamous epithelium of the esophagus is replaced by metaplastic columnar epithelium. Esophageal adenocarcinoma (EA) develops through progression from BE to low- and high-grade dysplasia (LGD/HGD) and to adenocarcinoma. It is widely accepted that inflammation can increase cancer risk, promoting tumor progression. Therefore, inflammation is regarded as the seventh hallmark of cancer. In recent years, the inflammation-cancer connection of Barrett's carcinogenesis has been intensively studied, unraveling genetic abnormalities. Besides genetic alterations, inflammation is also epigenetically linked to loss of protein expression through transcriptional silencing via promoter methylation. Key mediators linking inflammation and Barrett's carcinogenesis include reactive oxygen species (ROS), NFκB, inflammatory cytokines, prostaglandins, and specific microRNAs (miRNAs). Therefore, the decipherment of molecular pathways that contain these and novel inflammatory key mediators is of major importance for diagnosis, therapy, and prognosis. The detailed elucidation of the signaling molecules involved in Barrett's carcinogenesis will be important for the development of pharmaceutical inhibitors. We herein give an overview of the current knowledge of the inflammation-mediated genetic and epigenetic alterations involved in Barrett's carcinogenesis. We highlight the role of oxidative stress and deregulated DNA damage checkpoints besides the NFκB pathway.

PinX1: a sought-after major tumor suppressor at human chromosome 8p23

Human chromosome 8p23 is a region that has the most frequent heterozygosity in common human adult epithelial malignancies, but its major tumor suppressor gene(s) remain to be identified. Telomerase is activated in most human cancers and is critical for cancer cell growth. However, little is known about the significance of telomerase activation in chromosome instability and cancer initiation. The gene encoding the potent and highly conserved endogenous telomerase inhibitor PinX1 is located at human chromosome 8p23. However, the role of PinX1 in telomerase regulation and cancer development is not clear. Recent works from our group indicate that PinX1 is critical for maintaining telomere length at the optimal length. Furthermore, PinX1 is reduced in a large subset of human breast cancer tissues and cells. Significantly, PinX1 inhibition activates telomerase, and elongates telomeres, eventually leading to chromosome instability, all of which are abrogated by telomerase knockdown or knockout. Moreover, PinX1 allele loss causes majority of mice to develop a variety of epithelial cancers, which display chromosome instability and recapitulate to 8p23 allele loss in humans. These results indicate that PinX1 is a sought-after major tumor suppressor at human chromosome 8p23 that is essential for regulating telomerase activity and maintaining chromosome stability. These results suggest that inhibition of telomerase using PinX1 especially its telomerase inhibitory fragment or other methods might be used to treat cancers that have telomerase activation.

Telomere length is a prognostic factor for overall survival in colorectal cancer

AIM

The aim of this study was to determine whether telomere length is an independent prognostic factor for the prevention and survival of colorectal cancer.

METHOD

Terminal restriction fragment (TRF) length was determined by Southern blot in tumours and paired normal tissue samples from 147 patients with sporadic colorectal cancer who had undergone surgery. The TRF length ratio (TRFLR) was determined as the ratio between the length of the patient's tumour and normal tissue.The classification and regression tree technique was used to determine optimal cut-off values (≤ 1 or > 1).

RESULTS

Mean TRF length was 6.79 Kbp (1.19-13.99) in tumour tissue and 7.81 Kbp (3.63-15.70) in normal mucosa (P < 0.001). Mean TRFLR was 0.88. Telomere length and telomere length ratio were not correlated with any clinicopathological factors. In univariate analysis, overall survival was related to N stage (lymph node +/-; P = 0.002), TNM classification (P = 0.019) and TRFLR (≤ 1 or > 1; P = 0.014). In multivariate analysis, overall survival was significantly associated with TRFLR and N stage. Colorectal cancer patients with TRFLR ≤ 1 and negative lymph node involvement had a higher overall survival rate.

CONCLUSION

Telomere length ratio is an independent prognostic factor for survival in colorectal cancer patients, and the telomere lengths in the normal and tumour mucosa of the same patient present with parallel behaviour.

Alterations of telomere length in human brain tumors

Telomeres at the ends of human chromosomes consist of tandem hexametric (TTAGGG)n repeats, which protect them from degradation. At each cycle of cell division, most normal somatic cells lose approximately 50-100 bp of the terminal telomeric repeat DNA. Precise prediction of growth and estimation of the malignant potential of brain tumors require additional markers. DNA extraction was performed from the 51 frozen tissues, and a non-radioactive chemiluminescent assay was used for Southern blotting. One sample t-test shows highly significant difference in telomere length in meningioma and astrocytoma with normal range. According to our results, higher grades of meningioma and astrocytoma tumors show more heterogeneity in telomere length, and also it seems shortening process of telomeres is an early event in brain tumors.

The telomerase inhibitor PinX1 is a major haploinsufficient tumor suppressor essential for chromosome stability in mice

Telomerase is activated in most human cancers and is critical for cancer cell growth. However, little is known about the significance of telomerase activation in chromosome instability and cancer initiation. The gene encoding the potent endogenous telomerase inhibitor PinX1 (PIN2/TRF1-interacting, telomerase inhibitor 1) is located at human chromosome 8p23, a region frequently exhibiting heterozygosity in many common human cancers, but the function or functions of PinX1 in development and tumorigenesis are unknown. Here we have shown that PinX1 is a haploinsufficient tumor suppressor essential for chromosome stability in mice. We found that PinX1 expression was reduced in most human breast cancer tissues and cell lines. Furthermore, PinX1 heterozygosity and PinX1 knockdown in mouse embryonic fibroblasts activated telomerase and led to concomitant telomerase-dependent chromosomal instability. Moreover, while PinX1-null mice were embryonic lethal, most PinX1+/- mice spontaneously developed malignant tumors with evidence of chromosome instability. Notably, most PinX1 mutant tumors were carcinomas and shared tissues of origin with human cancer types linked to 8p23. PinX1 knockout also shifted the tumor spectrum of p53 mutant mice from lymphoma toward epithelial carcinomas. Thus, PinX1 is a major haploinsufficient tumor suppressor essential for maintaining telomerase activity and chromosome stability. These findings uncover what we believe to be a novel role for PinX1 and telomerase in chromosome instability and cancer initiation and suggest that telomerase inhibition may be potentially used to treat cancers that overexpress telomerase.

Telomeres and telomerase in normal and malignant B-cells

The telomeric checkpoint is emerging as a critical sensor of cellular damage, playing a major role in human aging and cancer development. In the meantime, telomere biology is rapidly evolving from a basic discipline to a translational branch, capable of providing major hints for biomarker development, risk assessment and targeted treatment of cancer. These advances have a number of implications in the biology of lymphoid tumours. Moreover, there is considerable interest in the potential role of telomeric dysfunction in the wide array of immunological abnormalities, grouped under the definition of 'immunosenescence'. This review will summarize the impact of recent advances in telomere biology on the physiology and pathology of the B lymphocyte, with special interest in immunosenescence and lymphomagenesis.

Biomarkers in Barrett's esophagus and esophageal adenocarcinoma: predictors of progression and prognosis

Barrett's esophagus is a well-known premalignant lesion of the lower esophagus that is characterized by intestinal metaplasia of the squamous epithelium. It is clinically important due to the increased risk (0.5% per annum) of progression to esophageal adenocarcinoma (EA), which has a poor outcome unless diagnosed early. The current clinical management of Barrett's esophagus is hampered by the lack of accurate predictors of progression. In addition, when patients develop EA, the current staging modalities are limited in stratifying patients into different prognostic groups in order to guide the optimal therapy for an individual patient. Biomarkers have the potential to improve radically the clinical management of patients with Barrett's esophagus and EA but have not yet entered mainstream clinical practice. This is in contrast to other cancers like breast and prostate for which biomarkers are utilized routinely to inform clinical decisions. This review aims to highlight the most promising predictive and prognostic biomarkers in Barrett's esophagus and EA and to discuss what is required to move the field forward towards clinical application.

Relationship between the expression of hTERT and EYA4 mRNA in peripheral blood mononuclear cells with the progressive stages of carcinogenesis of the esophagus

Objective

To establish a relationship between esophageal squamous cell diseases and the expression of human telomerase reverse transcriptase (hTERT) and Eyes absent 4 (EYA4) mRNA in peripheral blood mononuclear cells.

Methods

Subjects were 50 patients with esophageal squamous cell carcinoma (ESCC), 50 with dysplasia (ESCD), 50 with basal cell hyperplasia (BCH) and 50 controls. All subjects were residents of Feicheng County, Shandong Province, China , diagnosed by histopathology. Expression of hTERT and EYA4 mRNA in peripheral blood was determined by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR).

Results

The hTERT and EYA4 mRNA positive expression increased according to disease severity. At the cut-off value of ≥ 0.2, the positive expression rates of EYA4 were 14% for controls, 20.0% for BCH, 26% for ESCD and 52% for ESCC, respectively. At the cut-off value of ≥ 0.8, the positive expression rates of hTERT in the four groups were 24%, 30.0%, 52% and 80%, respectively. Using a positive value of 0.47 for EYA4, the testing sensitivities in the ESCD and ESCC groups were 4% and 16%, respectively, and the testing specificity increased to 100%. Using a positive value of 1.0 for hTERT, the testing sensitivities in the ESCD and ESCC groups were 48% and 60%, respectively, and the testing specificity increased to 72%. The testing sensitivities in the predicting ESCD and ESCC in the discriminant model including EYA4 and hTERT and the five traditional risk factors (sex, age, smoking, alcohol drinking, and family history of esophageal cancer) were 70% and 80%, and testing specificities were 76% and 88% respectively. However, the testing sensitivities and specificities in the predicting ESCD and ESCC in the model only including the above five traditional risk factors were lower than that in the former case.

Conclusion

EYA4 and hTERT mRNA expression increased with the severity of esophageal pathological changes and may be useful for identifying high-risk endoscopy candidates or for monitoring changes in premalignant esophageal lesions.

Cell proliferation in the presence of telomerase

Background

Telomerase, which is active early in development and later in stem and germline cells, is also active in the majority of human cancers. One of the known functions of telomerase is to extend the ends of linear chromosomes, countering their gradual shortening at each cell division due to the end replication problem and postreplication processing. Telomerase concentration levels vary between different cell types as well as between different tumors. In addition variable telomerase concentrations will exist in different cells in the same tumor when telomerase inhibitors are used, because of limitations of drug delivery in tissue. Telomerase extends short telomeres more frequently than long telomeres and the relation between the extension frequency and the telomere length is nonlinear.

Methodolgy/Principal Findings

Here, the biological data of the nonlinear telomerase-telomere dynamics is incorporated in a mathematical theory to relate the proliferative potential of a cell to the telomerase concentration in that cell. The main result of the paper is that the proliferative capacity of a cell grows exponentially with the telomerase concentration.

Conclusions/Significance

The theory presented here suggests that long term telomerase inhibition in every cancer progenitor or cancer stem cell is needed for successful telomere targeted cancer treatment. This theory also can be used to plan and asses the results of clinical trials targeting telomerase.

Telomere length as a biological marker in malignancy

Telomere maintenance is important for tumor cell growth and survival. Telomere length (TL) is determined by the balance between positive and negative factors impacting telomere homeostasis. In the last decade, TL has emerged as a promising clinical marker for risk and prognosis prediction in patients with malignant disorders. Tumor TL, as well as TL in healthy tissues such as peripheral blood, may carry valuable information for future treatment strategies. Here we discuss the present status of TL as a biological marker in cancer patients.

Barrett's esophagus: can biomarkers predict progression to malignancy?

Barrett's esophagus (BE) is one of the most common premalignant lesions and can progress to esophageal adenocarcinoma. It is characterized histologically by a specialized intestinal metaplasia that replaces the squamous epithelium of the distal esophagus, and is associated with chronic gastroesophageal reflux disease and obesity. Similar to the adenoma-carcinoma sequence of colorectal carcinomas, esophageal adenocarcinoma develops through progression from BE to low- and high-grade dysplasia, then to adenocarcinoma with accumulation of genetic and epigenetic abnormalities. The exact malignancy potential of BE is uncertain. Dysplasia is the most predictive marker for risk of esophageal adenocarcinoma, whereas endoscopic and histological diagnoses are still the gold standard for surveillance of patients with BE. However, both are limited, either by sampling errors in biopsies or by differences in histological interpretation. Several studies have identified candidate biomarkers that may have predictive value and may serve as additional factors for the risk assessment of esophageal adenocarcinoma. This review discusses the role of biomarkers in the progression from BE to adenocarcinoma, focusing on clinical and molecular markers.