Telomerase activity as a prognostic factor in colorectal cancer

Characterization of blood-derived exosomal hTERT mRNA as a biomarker for colon cancer and Lynch syndrome

Background

Human telomerase reverse transcriptase (hTERT)- mRNA was shown to be elevated in exosomes derived from the sera of a variety of hematological and solid cancer patients. We aimed to evaluate its role as a diagnostic marker in patients with newly diagnosed colon cancer and in hereditary syndromes with predisposition to colon cancer.

Methods

hTERT -mRNA levels were determined in serum-derived exosomes from 88 patients with colon cancer, 71 Lynch-syndrome carriers with unknown active malignancies and 50 healthy controls. Data, including demographics, background diseases, clinical data regarding tumor characteristics and genetic data, were retrieved data from medical files.

Results

Patients with colon cancer had both higher exosomal hTERT mRNA levels and a higher proportion of patients with positive exosomal hTERT mRNA than controls (29.5% vs. 4%, respectively, P values < 0.001). Within the cancer group, patients with a metastatic disease had higher levels of telomerase mRNA than non-metastatic disease patients, and these levels correlated with CEA levels. Likewise, Lynch syndrome carriers had a higher proportion of positive exosomal hTERT mRNA than controls (21.1% vs. 4%, respectively, P value 0.008) but only a trend towards higher exosomal hTERT mRNA levels. Higher telomerase mRNA levels were not correlated with the mutated gene.

Conclusions

Exosomal serum hTERT –mRNA levels are associated with metastatic colon cancer and were also demonstrated in a subset of Lynch syndrome carriers. Its significance as a biomarker for developing malignancy should be elucidated.

Investigating the Role of Telomere and Telomerase Associated Genes and Proteins in Endometrial Cancer

Endometrial cancer (EC) is the commonest gynaecological malignancy. Current prognostic markers are inadequate to accurately predict patient survival, necessitating novel prognostic markers, to improve treatment strategies. Telomerase has a unique role within the endometrium, whilst aberrant telomerase activity is a hallmark of many cancers. The aim of the current in silico study is to investigate the role of telomere and telomerase associated genes and proteins (TTAGPs) in EC to identify potential prognostic markers and therapeutic targets. Analysis of RNA-seq data from The Cancer Genome Atlas identified differentially expressed genes (DEGs) in EC (568 TTAGPs out of 3467) and ascertained DEGs associated with histological subtypes, higher grade endometrioid tumours and late stage EC. Functional analysis demonstrated that DEGs were predominantly involved in cell cycle regulation, while the survival analysis identified 69 DEGs associated with prognosis. The protein-protein interaction network constructed facilitated the identification of hub genes, enriched transcription factor binding sites and drugs that may target the network. Thus, our in silico methods distinguished many critical genes associated with telomere maintenance that were previously unknown to contribute to EC carcinogenesis and prognosis, including NOP56, WFS1, ANAPC4 and TUBB4A. Probing the prognostic and therapeutic utility of these novel TTAGP markers will form an exciting basis for future research.

The Relationship between Telomerase Activity and Clinicopathological Parameters in Colorectal Cancer: A Meta-Analysis

BACKGROUND

Recently, accumulated research has found that the expression of telomerase activity (TA) was associated with colorectal cancer (CRC) advancement, whereas the TA prognostic effect in CRC patients is still controversial.

AIMS

To investigate relationships between TA and CRC clinicopathological parameters.

STUDY DESIGN

Meta-analysis study.

METHODS

We searched published studies in databases, such as EMBASE, the Cochrane Library, PubMed, and Ovid databases (last search updated to October 2014) by meeting specified search criteria. The quality of the included studies was usually evaluated and a meta-analysis was implemented by Stata 12.0 software. We used an odds ratio (OR) with a 95% confidence interval (CI) to evaluate relationship strengths between TA and CRC clinicopathological parameters.

RESULTS

In total, 11 studies (715 patients) were included to assess the relation between TA and metastasis-related parameters in CRC patients. The results indicate that a senior TA expression was connected with the existence of lymph node metastasis (180 patients; OR=2.85, 95% CI=1.40-5.81, p=0.004), and tumor site (522 patients; OR=2.93, 95% CI=1.29-6.67, p=0.010). However, a senior TA expression was not connected with tumor size (137 patients; OR=1.57, 95% CI=0.71-3.47, p=0.267), histological differentiation (570 patients; OR=1.28, 95% CI=0.78-2.09, p=0.332), depth of invasion (57 patients; OR=3.76, 95% CI=0.61-23.04, p=0.152), distant metastasis (123 patients; OR=1.76, 95% CI=0.54-5.74, p=0.346), and clinical stage of the cancer (543 patients; OR=1.59, 95% CI=0.74-3.38, p=0.232).

CONCLUSION

This meta-analysis suggests that a positive TA was correlated with lymph node metastasis progression and tumor site of the CRC but did not correlate with other important clinicopathological parameters. TA can play a useful part in the prognosis and treatment of CRC patients, but further studies are required to confirm this.

Toward a molecular classification of colorectal cancer: the role of telomere length

Telomere biology is central to the maintenance of genomic stability and telomeric dysfunction is thought to be an early stage in carcinogenesis. Reports of telomere lengths and their ascribed colorectal cancer (CRC) risks have been discordant, with both very short and very long telomeres implicated. Nevertheless, telomeres appear to play a very central role in cancer initiation. Telomere length changes also appear to impact disease burden, progression, and overall survival. This review covers contemporary views on telomere biology and CRC risk, with a brief overview of analytical methods employed in telomere measurement. We conclude with arguments in favor of including telomere assessment in the molecular profiling of CRCs.

Telomeres, telomerase and colorectal cancer

Colorectal cancer (CRC) is the third most common cancer worldwide and, despite improved treatments, is still an important cause of cancer-related deaths. CRC encompasses a complex of diseases arising from a multi-step process of genetic and epigenetic events. Besides heterogeneity in the molecular and biological features of CRC, chromosomal instability is a hallmark of cancer and cancer cells may also circumvent replicative senescence and acquire the ability to sustain unlimited proliferation. Telomere/telomerase interplay is an important mechanism involved in both genomic stability and cellular replicative potential, and its dysfunction plays a key role in the oncogenetic process. The erosion of telomeres, mainly because of cell proliferation, may be accelerated by specific alterations in the genes involved in CRC, such as APC and MSH2. Although there is general agreement that the shortening of telomeres plays a role in the early steps of CRC carcinogenesis by promoting chromosomal instability, the prognostic role of telomere length in CRC is still under debate. The activation of telomerase reverse transcriptase (TERT), the catalytic component of the telomerase complex, allows cancer cells to grow indefinitely by maintaining the length of the telomeres, thus favouring tumour formation/progression. Several studies indicate that TERT increases with disease progression, and most studies suggest that telomerase is a useful prognostic factor. Plasma TERT mRNA may also be a promising marker for the minimally invasive monitoring of disease progression and response to therapy.

Telomeres and telomere dynamics: relevance to cancers of the GI tract

Aberrations in telomere length and telomere maintenance contribute to cancer development. In this article, we review the basic principles of telomere length in normal and tumor tissue and the presence of the two main telomere maintenance pathways as they pertain to gastrointestinal tract cancer. Peripheral blood telomeres are shorter in patients with many types of gastrointestinal tract cancers. Telomere length in tumor DNA also appears to shorten early in cancer development. Tumor telomere shortening is often accompanied by telomerase activation to protect genetically damaged DNA from normal cell senescence or apoptosis, allowing immortalized but damaged DNA to persist. Alternative lengthening of telomeres is another mechanism used by cancer to maintain telomere length in cancer cells. Telomerase and alternative lengthening of telomeres activators and inhibitors may become important chemopreventive or chemotherapeutic agents as our understanding of telomere biology, specific telomere-related phenotypes and its relationship to carcinogenesis increases.

Telomerase is an independent prognostic marker of overall survival in patients with colorectal cancer

Background:

Colorectal cancer (CRC) is an important cause of cancer-related death. Prediction of recurrence is an important issue in the treatment of disease, particularly for stage II patients. The level of telomere-specific reverse transcriptase (hTERT), the catalytic component of the telomerase complex, increases along with CRC progression, but its prognostic value is still unclear.

Methods:

One hundred and thirty-seven CRC patients were studied for hTERT expression in tumour cells by real-time PCR. hTERT level was evaluated as a prognostic factor of overall survival (OS) in all patients and of disease recurrence in a subgroup of 50 stage II patients.

Results:

The median hTERT level was 93.8 copies (interquartile range 48–254). Patients with high hTERT levels (above the median) showed a significantly worse survival than those with low hTERT levels (below the median; log-rank test P<0.0001; hazard ratio (HR)=3.30 (95% confidence interval (CI) 1.98–5.52); P<0.0001). The negative prognostic value of high hTERT level is independent of the pathological stage and microsatellite instability (HR=2.09 (95% CI 1.20–3.64), P=0.009). Moreover, in stage II CRC, high hTERT levels identified patients with a higher risk of disease recurrence (HR=3.06 (95% CI 1.03–9.04), P=0.043) and death (HR=3.24 (95% CI 1.37–7.71), P=0.008).

Conclusion:

hTERT level is an independent prognostic marker of OS in CRC patients. In addition, assessment of hTERT level could improve stratification of stage II CRC patients for the risk of disease recurrence.

[Expression of hTERT mRNA in Anip973 and Anip973/NVB cell detected by quantitative real-time PCR]

BACKGROUND AND OBJECTIVE

Human telomerase reverse transcriptase is the catalytic subunit of telomerase, and its activity is correlated with cell's sensitivity to chemotherapy. The aim of this study is to investigate the differential expression of human telomerase reverse transcriptase (hTERT) mRNA in human lung adenocarcinoma cell line Anip973 and Anip973/NVB, and to observe the correlation between hTERT mRNA and drug-resistance.

METHODS

The real-time fluorescence quantitative RT-PCR was used to detect the change of hTERT mRNA in human lung adenocarcinoma drug-resistant cell Anip973/NVB and parental cell Anip973 treated by NVB.

RESULTS

In the control group, the expression of hTERT mRNA showed no significant difference between drug-resistant cell Anip973/NVB and parental cell Anip973. After been treated by NVB, the expression of hTERT mRNA in parental cell was significantly decreased (P < 0.01), and drug-resistant cell Anip973/ NVB had no evidently variant (P > 0.05). The down-regulated hTERT mRNA in Anip973 cell was higher than that in Anip973/ NVB cell.

CONCLUSION

Telomerase correlates with the drug-resistant cell A973/NVB, and telomerase may be a new target for multi-drug resistant inversion.

Enabling individualized therapy through nanotechnology

Individualized medicine is the healthcare strategy that rebukes the idiomatic dogma of 'losing sight of the forest for the trees'. We are entering a new era of healthcare where it is no longer acceptable to develop and market a drug that is effective for only 80% of the patient population. The emergence of "-omic" technologies (e.g. genomics, transcriptomics, proteomics, metabolomics) and advances in systems biology are magnifying the deficiencies of standardized therapy, which often provide little treatment latitude for accommodating patient physiologic idiosyncrasies. A personalized approach to medicine is not a novel concept. Ever since the scientific community began unraveling the mysteries of the genome, the promise of discarding generic treatment regimens in favor of patient-specific therapies became more feasible and realistic. One of the major scientific impediments of this movement towards personalized medicine has been the need for technological enablement. Nanotechnology is projected to play a critical role in patient-specific therapy; however, this transition will depend heavily upon the evolutionary development of a systems biology approach to clinical medicine based upon "-omic" technology analysis and integration. This manuscript provides a forward looking assessment of the promise of nanomedicine as it pertains to individualized medicine and establishes a technology "snapshot" of the current state of nano-based products over a vast array of clinical indications and range of patient specificity. Other issues such as market driven hurdles and regulatory compliance reform are anticipated to "self-correct" in accordance to scientific advancement and healthcare demand. These peripheral, non-scientific concerns are not addressed at length in this manuscript; however they do exist, and their impact to the paradigm shifting healthcare transformation towards individualized medicine will be critical for its success.

Telomere function in colorectal cancer

Colorectal cancer is the third most common form of cancer and the second leading cause of cancer-related death in the western world. Tumour cells acquire the hallmarks of cancer during the carcinogenic selection process. Cell immortality is one of the principal features acquired during this process which involves the stabilization of telomere length. It is achieved mainly, by telomerase activation. Thus, the discovery of telomeres and telomerase allowed an understanding of the mechanisms by which cells can become immortalized. Different studies have shown that tumour cells have shorter telomeres than nontumour cells and have detected telomerase activity in the majority of tumours. Survival studies have determined that telomere maintenance and telomerase activity are associated with poor prognosis. Taking into account all the results achieved by different groups, quantification and evaluation of telomerase activity and measurement of telomere length may be useful methods for additional biologic and prognostic staging of colorectal carcinoma.

Detection of peripheral blood human telomerase reverse transcriptase mRNA in colorectal cancer with real-time fluorescent quantitative RT-PCR and its clinical significance

AIM: To establish a real-time fluorescent quantitative reverse transcriptase polymerase chain reaction (RT-PCR) system for determining the expression of human telomerase reverse transcriptase (hTERT) mRNA in colorectal cancer (CRC), and to evaluate their diagnostic value for micrometastasis of CRC.

METHODS: The expression of hTERT mRNA in 53 CRC patients and 21 healthy subjects was determined using real-time fluorescent quantitative RT-PCR. Correlations between their expression and clinical pathological characteristics of CRC were analyzed. Receiver operating characteristic curve (ROC curve) was used to evaluate the diagnostic value for micrometastasis of CRC.

RESULTS: The expression levels of peripheral blood hTERT mRNA were significantly higher in CRC patients than in the normal controls (t′ = 7.953, P < 0.05), and their expressions were correlated with lymph node metastasis, hematogenous metastasis and TNM staging of CRC (t′/t = 2.334, 2.149, 2.460, all P < 0.05). The area under ROC curve of hTERT mRNA in diagnosing CRC was 0.91, and the cutoff value was Ct≤32.

CONCLUSION: Real-time fluorescent quantitative RT-PCR has an advantage of giving the quantitative expression of hTERT mRNA compared with the traditional PCR which was only applied to the qualitative expression. Peripheral blood hTERT mRNA is a novel and excellent marker for micrometastasis of CRC.

Clinical significance of telomerase activity in peritoneal disseminated cells: gastrointestinal cancers

Early detection and accurate staging of gastrointestinal (GI) cancers are difficult. The aim of this study was to evaluate whether telomerase activity (TA) in exfoliated/disseminated epithelial cells could be used as a reliable marker for GI cancers. TA was evaluated with the real-time RTQ-TRAP in immunomagnetically sorted peritoneal epithelial cells from 60 patients undergoing surgical treatment. Thirty-two patients were clinically diagnosed with a variety of GI cancers: 1 had premalignant disease, 2 had history of GI cancers, and 25 patients were clinically negative for cancer. Here we report that all types and all cases of gastrointestinal cancers were telomerase positive, thereby demonstrating 100% sensitivity for cancer. Eighteen of 25 nonmalignant cases had undetectable levels of TA, 2 had low, and 5 of 25 expressed high TA levels. Because normal epithelial cells usually have low TA and a lesser tendency to exfoliate compared with cancer cells, it is of great importance to have close follow-up for these patients to exclude possible malignant disease. We conclude that RTQ-TRAP assessment of TA in immunomagnetically sorted peritoneal epithelial cells has 100% sensitivity and 100% negative predictive value for GI cancers, and therefore, can be considered as a valuable tool and useful addition to current standard diagnostic methods. Clinical significance of unusually high telomerase activity in some clinically negative for cancer cases requires further study.

Telomerase activity in colorectal cancer, prognostic factor and implications in the microsatellite instability pathway

AIM: To determine whether the telomerase activity is related to the Microsatellite instability (MSI) genetic pathway and whether it means a difference in the survival.

METHODS: The population consisted of 97 colorectal cancer patients. MSI determination was performed in accordance with the NCI criteria using PCR and Genescan. Telomerase activity was determined by the TRAP-assay, an ELISA procedure based on the amplification of telomeric repeat sequences.

RESULTS: 6.2% showed high MSI (MSI-H), 10.3% showed low MSI (MSI-L) and 83.5% did not show this alteration (MSS). Positive telomerase activity was detected in 92.8% of the patients. 83.3% of MSI-H tumors showed positive telomerase against 93.8% of MSS tumors. In the overall survival analysis the absence of telomerase activity conferred a better prognosis.

CONCLUSION: Previous works have shown that tumors which develop via the MSI pathway present a better prognosis. No link between telomerase activity and MSI status is observed, although sample sizes are small. Patients with telomerase negative tumors had better overall survival than patients with telomerase positive tumors.

The telomerase activity and expression of hTERT gene can serve as indicators in the anti-cancer treatment of human ovarian cancer

OBJECTIVE

The aim of this study was to evaluate the clinicopathological significance of telomerase activity and expression of hTERT gene in human ovarian cancer. The potential value of them as indicators for chemotherapy in ovarian cancer cells was also studied.

MATERIALS AND METHODS

A total of 73 samples and ovarian cancer cell lines HO-8910 and COC1 were studied. Telomerase activity was detected by PCR-TRAP-ELISA assay and the expression of the hTERT mRNA was analyzed by semi-quantitative RT-PCR. Alteration of the telomerase activity and hTERT mRNA were also analyzed in the ovarian cancer cells treated with different concentration and different time of cisplatin. Cytogenetic analysis was performed to compare the telomere status in the OH-8910 cells pre- and post-cisplatin treatment. The associations between these two markers and cisplatin induced-apoptosis were respectively analyzed in COC1 cells by the flow cytometry.

RESULTS

Telomerase activity are highly increased in malignancy (0.795+/-0.168(A450-655 nm)) than borderline (0.389+/-0.174(A450-655 nm)), benign tumors (0.236+/-0.102(A450-655 nm)) and normal ovary (0.213+/-0.070(A450-655 nm)) (p < 0.05). Twenty samples showed detectable levels of hTERT. The hTERT gene positive lesion showed significantly higher telomerase activity than negative (p = 0.004). There is a significant correlation between the telomerase activity and expression of hTERT (r = 0.921). Both telomerase activity and expression of hTERT can reflect the chemotherapeutic effect of cisplatin in a time-dependent and dose-dependent manner. Treatment with 10 microM cisplatin, the hTERT mRNA decreased after 12h and completely disappeared after 48 h, whereas the telomerase activity did not decrease until 24h. Results from cytogenetic analysis and flow cytometry assay confirmed that the alterations of these two markers are associated with the anti-cancer treatment of cisplatin.

CONCLUSION

Expression of hTERT gene is rate-limiting with the activation of telomerase. Both of they may be useful in the predicting of chemotherapeutic effect in ovarian cancer.

Hypermethylation of tumor suppressor genes BRCA1, p16 and 14-3-3sigma in serum of sporadic breast cancer patients

BACKGROUND

We investigated the hypermethylation status in serum of sporadic breast cancer patients.

MATERIAL AND METHODS

The hypermethylation status of BRCA1, p16 and 14-3-3sigma in cancerous tissues and the paired serum of 38 sporadic breast cancer patients was examined by methylation-specific PCR (MSP) assay. Normal and benign tissue and serum control DNA were also examined to determine the specificity of hypermethylation.

RESULTS

Hypermethylation of 1 or more genes was found in 36/38 (95%) of sporadic breast cancers. BRCA1 was hypermethylated in 14/38 (37%), p16 in 13/38 (34%), and 14- 3-3sigma in 33/38 (87%) of cancerous tissues. 71% of the corresponding serum DNA was positive for hypermethylation, including all histological types, stages and grades. No methylated products of BRCA1, p16 and 14-3-3sigma were observed in serum DNA from healthy women and patients with benign tissue specimens. A gene unmethylated in the tumor DNA was always found to be unmethylated in matched serum DNA.

CONCLUSIONS

Hypermethylation of BRCA1, p16 and 14-3-3sigma is present in all histologic types, stages and grades in sporadic breast cancer and can be detected in serum DNA. It signifies that serum-based hypermethylation screening may enhance early detection of sporadic breast cancer.