Telomerase in endocrine and endocrine-dependent tumors

Telomerase and estrogen-sensing activities are essential for continued mammary growth in vivo but dispensable for "reprogramming" neural stem cells

It has been proposed that the erosion of telomere length is a limiting factor in replicative capacity and important in cell senescence. To determine if this activity was essential in the mouse mammary gland in vivo, we serially transplanted mammary fragments from wild type (TER^+/+), heterozygous (TER^+/−), and homozygous (TER^−/−) mammary tissues into the cleared mammary fat pads of immune-compromised nude mice. Individual implants from both homozygous and heterozygous TER null outgrowths showed growth senescence beginning at transplant generation two, earlier than implants from TER^+/+ mammary glands which continued to show growth. This result suggests that either mammary epithelial stem cells maintain their telomere length in order to self renew, or that the absence or reduction of telomerase template results in more frequent death/extinction of stem cells during symmetric divisions. A third possibility is the inability of signaling cells in the niche to replicate resulting in reduction of the maintenance signals necessary for stem cell renewal. Consistent with this, examination of senescent outgrowths revealed the absence of estrogen receptor alpha (ERα⁺) epithelium although progesterone receptor (PR⁺) cells were abundant. Despite their inability to establish mammary growth in vivo, TER^+/− cells were able to direct neural stem cells to mammary cell fates.

Telomerase-dependent and independent telomere maintenance and its clinical implications in medullary thyroid carcinoma

CONTEXT

Telomere maintenance via telomerase activation and the alternative lengthening of telomeres (ALT) mechanism was assessed in medullary thyroid carcinoma.

SETTING AND DESIGN

In total, 42 medullary thyroid carcinomas (MTC) were studied including 24 rearranged during transfection (RET)- mutated cases. Relative telomerase reverse transcriptase (TERT) expression, splice forms, and telomere length were determined by PCR-based methods, and telomerase activity by ELISA. The ALT mechanism was detected by Southern blot analysis and immunofluorescence.

RESULTS

TERT expression and telomerase activity were detected in 21/42 tumors (50%), and was independent of the common somatic M918T RET mutation. Mean telomere length was shorter in MTCs compared with thyroids. Telomerase activation was associated with large tumor size (P = .027), advanced clinical stage (P = .0001), and short survival (P = .0001). Full-length TERT and the α(-) and β(-)-deletion forms were revealed, and the full-length form was associated with short survival (P = .04). A subset of cases without telomerase activation showed involvement of the ALT mechanism, which was associated with a low MIB-1 proliferation index (P = .024).

CONCLUSIONS

Stabilization of telomeres by telomerase activation occurs in half of the MTCs and by the ALT mechanism in a subset of cases. Telomerase activation may be used as an additional prognostic marker in medullary thyroid carcinoma.

Hallmarks of gastrointestinal neuroendocrine tumours: implications for treatment

In the past few years, there have been advances in the treatment of neuroendocrine tumours (NETs) and improvements in our understanding of NET biology. However, the benefits to patients have been relatively modest and much remains yet to be done. The 'Hallmarks of Cancer', as defined by Hanahan and Weinberg, provide a conceptual framework for understanding the aberrations that underlie tumourigenesis and to help identify potential targets for therapy. In this study, our objective is to review the major molecular characteristics of NETs, based on the recently modified 'Hallmarks of Cancer', and highlight areas that require further research.

Molecular diagnosis of parathyroid carcinoma: a reality in the near future

INTRODUCTION

Parathyroid carcinoma (PC) is a rare endocrine malignancy that still suffers from a problem of delayed clinical diagnosis. Consequently, it usually is not recognized preoperatively and often is not conclusively identified during the operation either.

AREAS COVERED

The role played by parafibromin in the development of PC, representing an important advance in understanding the pathogenesis of this malignancy, is discussed. Through a careful search of the international literature, using "parathyroid carcinoma", "molecular genetics of parathyroid carcinoma" and "parathyroid tumorigenesis" as key words, other less mentioned molecular mechanisms are reappraised as potential molecular markers of PC; we also discuss their potential role in 20 parathyroid outgrowths. Finally, both the major efforts and the limitations of reported molecular diagnostic techniques and diagnostic markers are considered.

EXPERT OPINION

Currently, several critical issues still need to be addressed, such as the lack of: i) common criteria for the histopathological diagnosis of parathyroid malignancy and ii) timely appropriated preoperative diagnosis of PC. The latter issue would be of fundamental importance to assist the surgeon in performing a complete resection of all carcinomatous tissue at the time of the initial surgery, allowing for the greatest likelihood of a cure.

Telomerase mRNA detection in serum of patients with prostate cancer

Telomerase functions as a reverse transcriptase enzyme in the process of telomere synthesis and telomerase activity have been detected in a large part of neoplastic tissues, whereas in normal somatic cells they were low or undetectable. The aim of this study was to investigate the telomerase mRNA detection in the serum of patients with a prostate tumor by using real-time reverse transcription PCR. The results were compared with biological samples obtained by age-matched normal donors and by patients with cardiovascular or metabolic diseases. Our data demonstrated that telomerase mRNA is detectable in the serum of patients with prostate cancer whereas it is not amplifiable in normal donors. This marker, assayed with the molecular method of quantitative PCR in serum, may be useful for diagnosing and monitoring prostate cancer patients.

Importance of Hormones and Proteins Determination in the Material Obtained by Fine-Needle Aspiration

More than a half century of experience with aspiration punch of nodal changes in the thyroid gland has confirmed this procedure as a golden standard in the examination of thyroid nodal disease. Although sensitivity, specificity, reliability and reproducibility are incontestably high, this procedure cannot give a simple answer on whether the change examined is benign or malignant. Numerous attempts to improve the procedure resulted in considerably advanced findings. Besides refining the cytopathologic examination techniques, confirmation or determination of hormones, proteins and other substances in the material obtained by fine-needle aspiration are actually the greatest contribution to improvement the of procedure's diagnostic value. These markers are actually followed, in most medical centers, in aspirates of thyroid nodal changes but also surrounding lymph nodes in order to evaluate with greater certainty the type, volume and spread; this is important to establish treatment procedures and to evaluate the residual disease after accomplishing the treatment.

Human telomerase reverse transcriptase expression correlates with vascular endothelial growth factor-promoted tumor cell proliferation in prostate cancer

OBJECTIVE

To investigate the correlation between the expressions of human telomerase reverse transcriptase (hTERT) and vascular endothelial growth factor (VEGF) in prostate cancer (PCa) and benign prostatic hyperplasia (BPH), and to determine if hTERT was correlated with VEGF-promoted tumor cell proliferation in prostate cancer.

MATERIALS AND METHODS

Immunohistochemistry was used to analyze the expressions of hTERT and VEGF in 60 cases of PCa and 60 cases of benign prostatic hyperplasia (BPH). Then their correlation in PCa was analyzed by Spearman correlative analysis.

RESULTS

The expressions of hTERT were detected in 38 cases of PCa and 10 cases of BPH. The expressions of VEGF were detected in 46 cases of PCa and 28 cases of BPH. The expressions of hTERT and VEGF in PCa were significantly higher than those in BPH (P < 0.05). As a result of correlation analysis, it was found that with an increase of the expression of VEGF, the expression of hTERT also increased in PCa. Significant correlation was observed between the expressions of hTERT and VEGF in PCa (r = 0.8333, P < 0.05). But there was no significant correlation between the expressions of hTERT and VEGF in BPH (r = 0.3156, P > 0.05).

CONCLUSIONS

All experiences above indicate that hTERT was one of the important proteins in the proliferation-promoting effect of VEGF on tumor cells in PCa.

Novel molecular markers in well-differentiated thyroid cancers

Conventional cytopathology is an excellent tool for distinguishing benign from malignant thyroid nodules with high sensitivity and specificity. However, significant numbers of cases are indeterminate, resulting in many ultimately unnecessary diagnostic thyroidectomies. Numerous molecular markers have been studied in an attempt to improve the diagnostic accuracy of thyroid fine-needle aspiration cytology. Several markers, such as galectin-3 and thyroid peroxidase, have been extensively assessed and shown not only to differentiate malignant tumors from benign thyroid lesions with high sensitivity and specificity, but also to identify tumors associated with poor outcome. More recently, four other genes (PTTG, PBF, BRAF and MUC1) have been identified that show real promise as potential molecular markers in thyroid cancer, offering discrimination between tumor subtypes and providing valuable prognostic information. However, larger, well-controlled studies are needed before their introduction into routine clinical practice. The search for molecular markers represents one of the most exciting areas in translational thyroid cancer research. We are optimistic that molecular markers will be used in the near future as adjuncts to conventional histological techniques to improve diagnostic accuracy of fine-needle aspiration cytology for thyroid lesions, particularly those that are cytologically indeterminate.

Differential expression of human telomerase catalytic subunit mRNA by in situ hybridization in pheochromocytomas

In pheochromocytomas, it is very difficult to predict malignant potential by conventional histology or immunohistochemical and molecular markers. We investigated the expression of human telomerase catalytic component (hTERT) mRNA, hTERT protein, Ki-67 antigen, and p27kip1 in pheochromocytomas (27 benign, 7 suspected malignant, and 7 malignant), and evaluated the possibility of expressions of these proteins, and hTERT mRNA serve as diagnostic markers for predicting the biological behavior of these tumors. All tumors showed the classical histology and typical immunohistochemical pattern. By in situ hybridization, hTERT mRNA was expressed in 5/7 malignant tumors (defined as the presence of metastasis and/or extensive local invasion) as compared with 3/27 benign tumors. We examined the hTERT by immunohistochemistry to confirm the mRNA. hTERT mRNA expression was correlated with hTERT protein expression. All benign tumors exhibited no immunopositivity or <1% of cells stained for Ki-67 antigen. Six out of seven malignant tumors have shown either hTERT mRNA expression or Ki-67 immunoreactivity. While no statistical difference in p27kip1 expressions was observed among benign, malignant, and suspected malignant tumors, there was a statistical difference between the normal adrenal medulla samples and tumors (p < 0.001). Thus, hTERT mRNA detection by in situ hybridization, hTERT expression, and Ki-67 antigen expression are all useful tools for differentiating malignant from benign pheochromocytomas.

Telomerase activity in “suspicious” thyroid cytology

BACKGROUND

Telomerase activity (TA) has been detected in most malignant neoplasms, including thyroid carcinomas. The authors studied the utility of TA detection as an ancillary tool to thyroid fine-needle aspiration (FNA) for patients with nonconclusive cytologic diagnoses.

METHODS

Material obtained by FNA from palpable thyroid nodules in 167 consecutive patients was processed for conventional cytologic studies and simultaneously for TA study. Another 8 patients were excluded from TA because of the presence of lymphocytes. All patients with negative results cases were followed for > 1 year, and those who had tumors that were suspicious or positive by FNA or TA underwent resection for pathologic study of nodules. TA was analyzed by telomere repeat amplification protocol-polymerase chain reaction analysis.

RESULTS

After excluding 20 patients because of insufficient material for cytologic study, 120 patients had negative results for malignant cells in cytology material, and the remaining 27 patients had results that were either suspicious (n = 21 patients) or positive (n = 6 patients). Histopathologic confirmation was obtained in 23 patients, including 18 with suspicious cytology (1 with scanty material) and 5 with positive FNA. The histopathologic diagnoses were nodular hyperplasia in 5 patients, follicular adenoma in 3 patients, papillary carcinoma in 11 patients, follicular carcinoma in 1 patient, medullary carcinoma in 2 patients, and lymphoma in 1 patient. TA was detected in 6 of 18 histologically confirmed thyroid neoplasms (1 of 3 follicular adenomas, 3 of 11 papillary carcinomas, 0 of 1 follicular carcinoma, 1 of 2 medullary carcinomas, and 1 of 1 lymphoma), including 1 neoplasm with scanty atypical cells.

CONCLUSIONS

The detection of TA helped to confirm neoplasia in 6 of 23 suspicious thyroid nodules. Although it was less sensitive than FNA, TA specificity was 100% for neoplasia and 87.5% for malignancy. The sensitivity of thyroid FNA increased with the use of TA detection when cytology was nonconclusive for malignancy.

Downregulation of metastasis suppressor genes in malignant pheochromocytoma

There is no reliable method currently available to predict malignant potential of pheochromocytoma based on conventional histology or genetic, molecular or immunohistochemical markers. Metastasis suppressor genes affect the spread of several cancers and, therefore, may provide promise as prognostic markers or therapeutic targets for malignant pheochromocytoma. We hypothesized that the downregulation of metastasis suppressor genes in malignant pheochromocytoma may play a role in malignant behavior. We applied quantitative real-time polymerase chain reaction (QRT-PCR) to 11 metastasis suppressor genes. These genes are known to be involved in the regulation of important cancer-related cellular events, such as cell growth regulation and apoptosis (nm23-H1, TIMP-1, TIMP-2, TIMP-3, TIMP-4, TXNIP and CRSP-3), cell-cell communication (BRMS-1), invasion (CRMP-1) and cell adhesion (E-Cad and KiSS1). The study included 15 benign and 10 malignant pheochromocytomas. Six metastasis suppressor genes (nm23-H1, TIMP-4, BRMS-1, TXNIP, CRSP-3 and E-Cad) were downregulated significantly in malignant compared to benign pheochromocytoma (p < 0.05, Mann-Whitney U-test). We applied a non-linear rule using median malignant value (MMV) as a threshold to use metastasis suppressor genes to distinguish malignant from benign samples. After cross-validation, the non-linear rule produced no errors in 10 malignant samples and 3 errors in the 15 benign samples, with an overall error rate of 12%. These results suggest that downregulation of metastasis suppressor genes reflect malignant pheochromocytoma with a high degree of sensitivity. Thus, we conclude that altered function of these metastasis suppressor gene pathways may play an important role in the malignant behavior of pheochromocytoma.

Tankyrase, a positive regulator of telomere elongation, is over expressed in human breast cancer

Tankyrase promotes telomere elongation by interaction with the telomeric protein binding factor TRF1, a negative regulator of telomere extension. We measured tankyrase mRNA by real-time RT-PCR in 66 breast cancers and in paired normal tissues. Results were compared with hTERT mRNA expression. The levels of tankyrase in breast cancers were significantly higher in comparison to normal tissues (P<0.0001) and significantly related to the status of progesterone receptors. No relationship was found between tankyrase and hTERT mRNA expression in breast cancers. According to our results, tankyrase expression appeared up regulated in breast cancers.

RNA expression of human telomerase subunits TR and TERT is differentially affected by melatonin receptor agonists in the MCF-7 tumor cell line

The RNA expression levels of human catalytic subunit (TERT) and the RNA subunit (TR) of telomerase were analysed after treatment with the agonists of the membrane receptor (S 20098) and the nuclear receptor (CGP 52608) for melatonin in the MCF-7 human breast tumor cell line. Neither membrane nor nuclear signalling affected the RNA steady-state levels of the TR subunit of telomerase. On the contrary, we observed a significant decreased in the RNA levels of TERT after treatment with CGP 52608 while S 20098 produced a significant increase in the RNA levels of TERT. These results support a cross-talk between membrane and nuclear melatonin signalling and provide new data on the hormonal regulation of telomerase function.

Combining a targeted radiotherapy and gene therapy approach for adenocarcinoma of prostate

A targeted radiotherapy/gene therapy approach for prostate cancer, using the radiopharmaceutical [(131)I]meta-iodobenzylguanidine ([(131)I]MIBG), would restrict the effects of radiotherapy to malignant cells, thereby increasing efficacy and decreasing morbidity of radiotherapy. Prostate cancer cells were transfected with a transgene encoding the noradrenaline transporter (NAT) under the control of tumour-specific telomerase promoters, enabling them to actively take up [(131)I]MIBG. This led to tumour-specific cell kill. This strategy has the advantage of generating a radiological bystander effect, leading to the destruction of neighbouring tumour cells that have escaped transfection. This targeted approach could be a promising tumour-specific treatment option for prostate cancer.

The clinically inapparent adrenal mass: update in diagnosis and management

Clinically inapparent adrenal masses are incidentally detected after imaging studies conducted for reasons other than the evaluation of the adrenal glands. They have frequently been referred to as adrenal incidentalomas. In preparation for a National Institutes of Health State-of-the-Science Conference on this topic, extensive literature research, including Medline, BIOSIS, and Embase between 1966 and July 2002, as well as references of published metaanalyses and selected review articles identified more than 5400 citations. Based on 699 articles that were retrieved for further examination, we provide a comprehensive update of the diagnostic and therapeutic approaches focusing on endocrine and radiological features as well as surgical options. In addition, we present recent developments in the discovery of tumor markers, endocrine testing for subclinical disease including autonomous glucocorticoid hypersecretion and silent pheochromocytoma, novel imaging techniques, and minimally invasive surgery. Based on the statements of the conference, the available literature, and ongoing studies, our aim is to provide practical recommendations for the management of this common entity and to highlight areas for future studies and research.

Topoisomerase II alpha and telomerase expression in papillary thyroid carcinomas

BACKGROUND

Altered topoisomerase II alpha (Topo II alpha) expression and telomerase activity (TA) reflect tumour cell growth and malignant transformation.

METHODS

We examined TA by using a TRAP assay and expression of Topo II alpha by immunohistochemical analysis in a series of 27 cases of papillary thyroid carcinoma (PTC).

RESULTS

Topo II alpha labelling index (LI) ranged from 0.1 to 4.2% and was significantly associated with patient age (r=-0.42, p=0.003), with higher levels of Topo II alpha in patients under 40 years. There was no relationship between Topo II alpha LI, AGES score or other clinical outcome. TA was detected in 14 PTC, with relative levels ranging from 1.2 to 102 units. A significant positive correlation between the multiplicity of tumoral foci and the TA levels (p<10(-2)) was noted.

CONCLUSION

We concluded that Topo II alpha cannot be used as a marker of tumour aggressiveness. Furthermore, enhanced Topo II alpha expression in PTCs from patients less than 40 years old suggests that this age group might benefit from Topo II inhibitor chemotherapy.

Human prostate cancer precursors and pathobiology

Prostate cancer is among the most common malignancies. It is estimated that 1 in 6 men in the United States will be diagnosed with this disease. Despite the high prevalence and importance of prostate cancer, the molecular mechanisms underlying its development and progression remain poorly understood. This article reviews new information about the roles of oxidants and electrophiles in prostate cancer; the potential importance of chronic inflammation and atrophy in prostate carcinogenesis, and implications for chemoprevention; evidence supporting telomere shortening and genetic instability in the etiology of prostate cancer; and alpha-methylacyl-coenzyme A racemase (AMACR) as a potential marker for prostate carcinogenesis. These new results show that at least some high-grade prostatic intraepithelial neoplasias (PIN) and early adenocarcinomas appear to arise from proliferative inflammatory atrophy (PIA). Inflammation and other environmental factors may lead to the destruction of prostate epithelial cells, and increased proliferation may occur as a response to this cell death. Such proliferation may be mechanistically related to decreased p27(Kip1) observed in PIA. The decreased apoptosis associated with these events may also be related to increased expression of Bcl-2. Increased oxidant and electrophile stress in the setting of increased proliferation associated with these events may lead to elevated glutathione S-transferase P1 (GSTP1) expression as a genomic-protective measure. However, aberrant methylation of the CpG island of the GSTP1 gene promoter silences GSTP1 gene expression and protein levels, setting the stage for additional genetic damage and accelerated progression toward PIN and carcinoma. Additional results show that AMACR may be an important new marker of prostate cancer, and its use in combination with p63 staining may provide the basis for an improved method for identification of prostate cancer.

Polymerase chain reaction in the detection of tumor cells: new approaches in diagnosis and follow-up of patients with thyroid cancer

Thyroid cancers are the most common endocrine malignancies and are being diagnosed with increasing frequency. In addition to other measures, diagnosis is based on fine-needle aspiration cytology examination. Recently, new assays using reverse transcription-polymerase chain reaction (PCR) are being tested to improve sensitivity and specificity of primary diagnosis and detection of recurrent thyroid cancer. In the preoperative diagnosis of thyroid cancer, several tissue- and/or tumor-specific mRNA have been described and in several cases, a higher sensitivity and specificity could be achieved using molecular techniques compared to conventional methods. In the postoperative follow-up of patients with thyroid cancer, conflicting data have been published and the use of PCR techniques revealed several problems of the molecular approach, which are based on some technical as well as biologic limitations. Despite these problems, which are discussed in detail in this review, molecular techniques may nevertheless improve the sensitivity and accuracy of fine-needle aspiration of thyroid nodules, fine-needle aspiration of metastases, and detection of recurrent disease in peripheral blood samples.