Expression of Telomeric Repeat Binding Factor-1 in Astroglial Brain Tumors

Prognostic significance of dysregulation of shelterin complex and its correlation with telomere length and cytogenetics in multiple myeloma

BACKGROUND

MM (multiple myeloma) is a bone marrow disease with the accumulation of malignant plasma cells characterized by the neoplastic transformation of differentiated B cells. The onset and progression of cancer are greatly influenced by telomere dysfunction. We aimed to study the biomarker potential and prognostic significance of shelterin complex and hTERT. Telomere length and gene expression were measured using real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR), and these results were further correlated with clinical parameters.

RESULTS

Our study showed increased expression of all genes in complex, hTERT, and TL in MM (n = 72) in comparison with controls (n = 31). TRF2 (P = 0.025) and hTERT (P = 0.0002) displayed significant association among cytogenetic analysis. The receiver operative curve showed POT1 and RAP1 with a greater area under the curve (AUC). RAP1 (P = 0.020) and hTERT (P = 0.037) displayed to be independent prognostic markers for overall survival. Clinical parameters and genes were observed to be significantly correlated.

CONCLUSION

Our study findings showed variation in telomere-associated genes and suggest the participation of these genes as prognostic markers in MM. These results all together highlight the evaluation and role of genes involved in telomeric alteration and TL, providing the opportunity to study new therapeutic approaches in patients with MM.

The effects of histone deacetylase inhibitors on glioblastoma-derived stem cells

Glioblastoma multiforme (GBM) is the most malignant brain tumor with limited effective treatment options. Cancer stem cells (CSCs), a subpopulation of cancer cells with stem cell properties found in GBMs, have been shown to be extremely resistant to radiation and chemotherapeutic agents and have the ability to readily reform tumors. Therefore, the development of therapeutic agents targeting CSCs is extremely important. In this study, we isolated glioblastoma-derived stem cells (GDSCs) from GBM tissue removed from patients during surgery and analyzed their gene expression using quantitative real-time PCR and immunocytochemistry. We examined the effects of histone deacetylase inhibitors trichostatin A (TSA) and valproic acid (VPA) on the proliferation and gene expression profiles of GDSCs. The GDSCs expressed significantly higher levels of both neural and embryonic stem cell markers compared to GBM cells expanded in conventional monolayer cultures. Treatment of GDSCs with histone deacetylase inhibitors, TSA and VPA, significantly reduced proliferation rates of the cells and expression of the stem cell markers, indicating differentiation of the cells. Since differentiation into GBM makes them susceptible to the conventional cancer treatments, we posit that use of histone deacetylase inhibitors may increase efficacy of the conventional cancer treatments for eliminating GDSCs.

Telomere length modulation in human astroglial brain tumors

Background

Telomeres alteration during carcinogenesis and tumor progression has been described in several cancer types. Telomeres length is stabilized by telomerase (h-TERT) and controlled by several proteins that protect telomere integrity, such as the Telomere Repeat-binding Factor (TRF) 1 and 2 and the tankyrase-poli-ADP-ribose polymerase (TANKs-PARP) complex.

Objective

To investigate telomere dysfunction in astroglial brain tumors we analyzed telomeres length, telomerase activity and the expression of a panel of genes controlling the length and structure of telomeres in tissue samples obtained in vivo from astroglial brain tumors with different grade of malignancy.

Materials and Methods

Eight Low Grade Astrocytomas (LGA), 11 Anaplastic Astrocytomas (AA) and 11 Glioblastoma Multiforme (GBM) samples were analyzed. Three samples of normal brain tissue (NBT) were used as controls. Telomeres length was assessed through Southern Blotting. Telomerase activity was evaluated by a telomere repeat amplification protocol (TRAP) assay. The expression levels of TRF1, TRF2, h-TERT and TANKs-PARP complex were determined through Immunoblotting and RT-PCR.

Results

LGA were featured by an up-regulation of TRF1 and 2 and by shorter telomeres. Conversely, AA and GBM were featured by a down-regulation of TRF1 and 2 and an up-regulation of both telomerase and TANKs-PARP complex.

Conclusions

In human astroglial brain tumours, up-regulation of TRF1 and TRF2 occurs in the early stages of carcinogenesis determining telomeres shortening and genomic instability. In a later stage, up-regulation of PARP-TANKs and telomerase activation may occur together with an ADP-ribosylation of TRF1, causing a reduced ability to bind telomeric DNA, telomeres elongation and tumor malignant progression.

Reduced expression of TRF1 is associated with tumor progression and poor prognosis in oral squamous cell carcinoma

The functions of telomeric repeat-binding factor 1 (TRF1) and 2 (TRF2) in oral carcinogenesis are largely unexplored. This study examined the relationship between the expression of TRF1 and TRF2 and clinicopathological variables and survival in oral cavity squamous cell carcinoma (OCSCC). Western blotting and immunohistochemistry were used to evaluate the protein expression of TRF1 and TRF2 in paired OCSCC patient specimens. Expression of TRF1 and TRF2 was assessed by immunohistochemistry in 256 OCSCC patients who underwent tumor resection without previous radiotherapy. The results were analyzed using Fisher's exact test. Protein expression of TRF1 and TRF2 was significantly lower in the OCSCC than in the adjacent non-tumor tissue. Reduced TRF1 and TRF2 levels in 256 patients, as revealed by immunohistochemistry, were significantly associated with aggressive clinicopathological features, such as advanced tumor stage (p<0.001) and advanced tumor node metastasis stage (p<0.001). According to Kaplan-Meier analysis, reduced TRF1 expression was significantly correlated with an unfavorable cumulative 5-year overall survival rate (p<0.001). In conclusion, decreased expression of TRF1 was significantly associated with tumor progression and poor prognosis in OCSCC patients.

Prognostic molecular markers with no impact on decision-making: the paradox of gliomas based on a prospective study

This study assessed the prognostic value of several markers involved in gliomagenesis, and compared it with that of other clinical and imaging markers already used. Four-hundred and sixteen adult patients with newly diagnosed glioma were included over a 3-year period and tumour suppressor genes, oncogenes, MGMT and hTERT expressions, losses of heterozygosity, as well as relevant clinical and imaging information were recorded. This prospective study was based on all adult gliomas. Analyses were performed on patient groups selected according to World Health Organization histoprognostic criteria and on the entire cohort. The endpoint was overall survival, estimated by the Kaplan–Meier method. Univariate analysis was followed by multivariate analysis according to a Cox model. p14^ARF, p16^INK4A and PTEN expressions, and 10p 10q23, 10q26 and 13q LOH for the entire cohort, hTERT expression for high-grade tumours, EGFR for glioblastomas, 10q26 LOH for grade III tumours and anaplastic oligodendrogliomas were found to be correlated with overall survival on univariate analysis and age and grade on multivariate analysis only. This study confirms the prognostic value of several markers. However, the scattering of the values explained by tumour heterogeneity prevents their use in individual decision-making.

Telomerase: is it the future diagnostic and prognostic tool in human cancer?

A number of methods exist to detect levels of telomerase activity and the presence of telomerase subunits in a variety of tissues. As telomerase activation seems to be an important step in tumorigenesis, accurate detection of the presence and activity of the enzyme and its subunits is vital. The original method of detecting telomerase activity was developed by Kim and coworkers in 1994, and was termed the telomeric repeat amplification protocol. This assay led to a staggering increase in the number of telomerase-associated publications in scientific journals (85 publications from 1974-1994, 5063 publications from 1994-2004). A number of methods have been described to detect telomeres and to measure their length, with the standard measurement of telomere length performed using a modification of the Southern blot protocol. RNA in situ hybridization can be performed to detect levels of the RNA component of telomerase, and standard in situ hybridization and immunohistochemistry can be applied to examine expression levels and localization of the catalytic subunit of the enzyme. Reverse transcriptase PCR has also been applied to assess expression levels of the telomerase components in various tissues. This review provides a synopsis of telomeres, telomerase, telomerase and cancer, and finally, methods for the detection of telomerase in cancer.

Expression of telomere-associated genes as prognostic markers for overall survival in patients with non-small cell lung cancer

PURPOSE

Human telomeres, which are composed of long, repetitive sequences of TTAGGG and a variety of proteins, function as a protective structure capping the ends of chromosomes. Telomere dysfunction plays important roles in cancer initiation and progression. TRF1, TRF2, POT1, and RAP1 are four major telomere proteins that regulate telomere stability and telomere length. We hypothesized that the expression of these genes would have significant predictive value for cancer development and prognosis.

EXPERIMENTAL DESIGN

We compared the mRNA expression level of TRF1, TRF2, POT1, and RAP1 between tumor and adjacent normal tissues from 148 patients with non-small cell lung cancer using real-time quantitative PCR. We then estimated the prognostic value of the mRNA expression of these genes in tumors.

RESULTS

The expression level of TRF1 was significantly lower in tumor tissues than in adjacent normal tissues (P < 0.0001); no significant difference was found for TRF2, POT1, and RAP1. The expression of RAP1 gene in tumors was highly predictive of overall survival. In the Cox proportional hazards model, patients with higher RAP1 expression were associated with a significantly better survival [hazard ratio (HR), 0.47; 95% confidence interval (95% CI), 0.24-0.91]. This improved survival was more prominent in men (HR, 0.45; 95% CI, 0.22-0.996) and in ever smokers (HR, 0.50; 95% CI, 0.24-1.02). Kaplan-Meier survival curves showed that patients with higher RAP1 expression had significantly longer median survival than patients with lower expression (median = 51.21 versus 15.34 months, P < 0.0009). The expressions of TRF2 in tumor tissues were significantly correlated with tumor grades (P = 0.0114).

CONCLUSIONS

RAP1 expression may be a useful biomarker of tumor progression and survival.

A study of the relationship between expression level of TRF1 protein and telomerase activity in human acute leukemia

OBJECTIVE

To study the expression level of TRF1 (telomeric repeat binding factor 1) protein in human acute leukemia and relationship between expression level of TRF1 protein and telomerase.

METHODS

A quantitative Western-Blot technique was developed using anti-TRF1(33-277) monoclonal antibody and GST-TRF1 purity protein as a standard to further determine the expression level of TRF1 protein in total proteins extracted from clinical specimens.

RESULTS

Bone marrow tissues of 20 acute leukemia patients were studied, 11 healthy donors' bone marrows were taken as a control. The expression level of TRF1 protein was significantly higher (P<0.01) in normal bone marrow ((2.217+/-0.462) microg/microl) than that of acute leukemia patients ((0.754+/-0.343) microg/microl). But there was no remarkable difference between ALL and ANLL patients ((0.618+/-0.285) microg/microl vs (0.845+/-0.359) microg/microl, P>0.05). After chemotherapy, TRF1 expression level of patients with complete remission elevated ((0.772+/-0.307) microg/microl vs (1.683+/-0.344) microg/microl, P<0.01), but lower than that of normal ((2.217+/-0.462) microg/microl, P<0.01). There was no significantly difference after chemotherapy ((0.726+/-0.411) microg/microl vs (0.895+/-0.339) microg/microl, P>0.05). TRF1 expression level of patients with complete remission is higher than that of patients without complete remission ((1.683+/-0.344) microg/microl vs (0.895+/-0.339) microg/microl, P<0.01). All samples were determined for telomerase activity. It was confirmed that the activity of telomerase in normal bone marrow was lower than that of acute leukemia patients ((0.125+/-0.078) microg/microl vs (0.765+/-0.284) microg/microl, P<0.01). There was no significant difference of expression level of TRF1 protein between ALL and ANLL patients ((0.897+/-0.290) microg/microl vs (0.677+/-0.268) microg/microl, P>0.05). After chemotherapy, telomerase activity of patients with complete remission decreased ((0.393+/-0.125) microg/microl), but was still higher than that of normal ((0.125+/-0.078) microg/microl, P<0.01).

CONCLUSION

The expression level of TRF1 protein has correlativity to the activity of telomerase (P<0.001).

Expression of telomeric repeat binding factor 1 in non-small cell lung cancer

BACKGROUND AND OBJECTIVES

Telomeric repeat binding factor 1 (TRF1) is crucial for forming and maintaining the protective telomeric structure. However, the relationship between TRF1 and non-small cell lung cancer(NSCLC) is not well understood. With this background, we investigated the expressions of the mRNA encoded by the TRF1 gene in cancer tissue and the paired non-cancerous tissue. We also examined whether TRF1 expression is correlated with histopathological features.

METHODS

From October 2004 to August 2005, 40 patients with NSCLCs had undergone curative operations, including 29 males and 11 females. There were 20 cases of squamous cell carcinoma and 20 cases of adenocarcinoma. We measured the expression of TRF1 mRNA using RT-PCR on 40 surgically resected specimens and the paired non-cancerous tissues.

RESULTS

TRF1 mRNA was significantly downregulated in cancer tissue compared with the paired non-cancerous tissue. Additionally, the expression of TRF1 mRNA was significantly associated with the grade of tumor differentiation. No significant difference of TRF1 mRNA level was found between sexes, or among different T-status, clinical stages, pathological subtypes, and lymph node metastasis.

CONCLUSIONS

Downregulation of TRF1 mRNA expression appeared in lung cancer tissue. TRF1 may play a significant role in cell differentiation in NSCLC.