Expression of telomerase reverse transcriptase (TERT) in malignant mesotheliomas

Phosphorylation of hTERT at threonine 249 is a novel tumor biomarker of aggressive cancer with poor prognosis in multiple organs

Recent evidence indicates that RNA‐dependent RNA polymerase (RdRP) activity of human telomerase reverse transcriptase (hTERT) regulates expression of target genes and is directly involved in tumor formation in a telomere‐independent manner. Non‐canonical function of hTERT has been considered as a therapeutic target for cancer therapy. We have previously shown that hTERT phosphorylation at threonine 249 (p‐hTERT), which promotes RdRP activity, is an indicator of an aggressive phenotype and poor prognosis in liver and pancreatic cancers, using two cohorts with small sample sizes with polyclonal p‐hTERT antibody. To clarify the clinical relevance of p‐hTERT, we developed a specific monoclonal antibody and determined the diagnostic and prognostic value of p‐hTERT in cancer specimens using a large cohort. A monoclonal antibody for phosphorylated hTERT (p‐hTERT) at threonine 249 was developed and validated. The antibody was used for the immunohistochemical staining of formalin‐fixed, paraffin‐embedded specimens from 1523 cases of lung, colon, stomach, pancreatic, liver, breast, and kidney cancers. We detected elevated p‐hTERT expression levels in cases with a high mitotic activity, high pathological grade, and high nuclear pleomorphism. Elevated p‐hTERT expression was an independent prognostic factor for lung, pancreatic, and liver cancers. Furthermore, p‐hTERT expression was associated with immature and aggressive features, such as adenosquamous carcinoma (lung and pancreas), invasive type of cancer (lung), high serum alpha‐fetoprotein level (liver), and triple‐negative status (breast). In conclusion, RdRP activity indicated by p‐hTERT expression predicts aggressive cancer phenotypes in various types of cancer. Thus, p‐hTERT is a novel biomarker for the diagnosis of aggressive cancers with a poor prognosis. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

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

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

Large-scale copy number analysis reveals variations in genes not previously associated with malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive tumor that is often causally associated with asbestos exposure. Comparative genomic hybridization techniques and arrays demonstrated a complex set of copy number variations (CNVs) in the MPM-genome. These techniques however have a limited resolution, throughput and flexibility compared to next-generation sequencing platforms.

In this study, the presence of CNVs in the MPM-genome was investigated using an MPM-cohort (N = 85) for which genomic microarray data are available through ‘The Cancer Genome Atlas’ (TCGA). To validate these results, the genomes of MPMs and matched normal samples (N = 21) were analyzed using low-pass whole genome sequencing on an ‘Illumina HiSeq’ platform. CNVs were detected using in-house developed analysis pipelines and frequencies of copy number loss and gain were calculated.

In both datasets, losses on chromosomes 1, 3, 4, 6, 9, 13 and 22 and gains on chromosomes 1, 5, 7 and 17 were found in at least 25% and 15% of MPMs, respectively. Besides the well-known MPM-associated genes, CDKN2A, NF2 and BAP1, other interesting cancer-associated genes were listed as frequently involved in a copy number loss (e.g. EP300, SETD2 and PBRM1). Moreover, four cancer-associated genes showed a high frequency of copy number gain in both datasets (i.e. TERT, FCGR2B, CD79B and PRKAR1A). A statistically significant association between overall survival and the presence of copy number loss in the CDKN2A-containing region was observed in the TCGA-set.

In conclusion, recurrent CNVs were detected in both datasets, occurring in regions harboring known MPM-associated genes and genes not previously linked to MPM.

The diagnostic value of immunohistochemically detected methylthioadenosine phosphorylase deficiency in malignant pleural mesotheliomas

AIMS

  Malignant pleural mesothelioma (MPM) often causes diagnostic difficulties for pathologists. We assessed whether loss of methylthioadenosine phosphorylase (MTAP), a key enzyme in the intracellular recycling of adenosine triphosphate (ATP) often deleted in MPM, could be detected with immunohistochemistry (IHC) and used as a diagnostic marker for MPM.

METHODS AND RESULTS

  We used IHC to detect MTAP in a cohort of 99 MPMs and 39 reactive mesothelial proliferations (RP) (reactive mesothelial hyperplasia n = 33, reactive pleural fibrosis n = 6). MTAP staining was assessed by an H score. The median H score of the RP cohort was set as a reference point. Cases with H scores below this reference point were considered to have decreased MTAP expression. We found that 64 of 99 (65%) of the investigated MPMs had decreased MTAP expression, while this was only true for nine of 39 (23%) of the RPs (P = 0.001). We further evaluated MTAP expression in a cohort of coagulated pleural effusions from 14 patients with MPM and 20 patients with RP by using a double-staining technique with Wilms tumour 1 (WT1) as a mesothelial marker. In these samples, decreased MTAP expression diagnosed MPM with a sensitivity of 71% and a specificity of 90%.

CONCLUSIONS

  Decreased MTAP expression could potentially be useful in combination with other markers in the diagnosis of MPM.

Pathological and molecular biological approaches to early mesothelioma

Malignant mesothelioma is an asbestos-related malignancy that arises primarily from mesothelial cells on the serosal surfaces of the pleural, peritoneal, and pericardial cavities. Malignant pleural mesothelioma (MPM) is most common, and its incidence is dramatically increasing worldwide as a result of widespread use of asbestos. Morphological discrimination between MPM and reactive mesothelial hyperplasia is difficult, and the most reliable pathological criterion for malignancy is mesothelial proliferation invading deeply into subpleural adipose tissues. To establish radical cure of MPM, it is crucial to find early-stage MPM of epithelial type, in which mesothelial proliferation is localized on the serosal surface of parietal pleura or limited within the submesothelial fibrous tissues of parietal pleura. The initial clinical presentation for patients with MPM is frequently dyspnea and/or chest pain due to large pleural effusion, and cytological analysis of pleural effusions is valuable to find patients with early-stage MPM of epithelial type. Recently, cytological features of MPM in pleural effusion, molecular markers for MPM, and genetic alternations of MPM have been reported. In this review, we discuss major issues on pathological and molecular biological approaches for diagnosis of early-stage MPM of epithelial type.

Prevalence of telomerase activity in human cancer

Telomerase activity has been measured in a wide variety of cancerous and non-cancerous tissue types, and the vast majority of clinical studies have shown a direct correlation between it and the presence of cancerous cells. Telomerase plays a key role in cellular immortality and tumorigenesis. Telomerase is activated in 80-90% of human carcinomas, but not in normal somatic cells, therefore, its detection holds promise as a diagnostic marker for cancer. Measurable levels of telomerase have been detected in malignant cells from various samples: tissue from gestational trophoblastic neoplasms; squamous carcinoma cells from oral rinses; lung carcinoma cells from bronchial washings; colorectal carcinoma cells from colonic luminal washings; bladder carcinoma cells from urine or bladder washings; and breast carcinoma or thyroid cancer cells from fine needle aspirations. Such clinical tests for telomerase can be useful as non-invasive and cost-effective methods for early detection and monitoring of cancer. In addition, telomerase activity has been shown to correlate with poor clinical outcome in late-stage diseases such as non-small cell lung cancer, colorectal cancer, and soft tissue sarcomas. In such cases, testing for telomerase activity can be used to identify patients with a poor prognosis and to select those who might benefit from adjuvant treatment. Our review of the latest medical advances in this field reveals that telomerase holds great promise as a biomarker for early cancer detection and monitoring, and has considerable potential as the basis for developing new anticancer therapies.

Syntenic relationships between genomic profiles of fiber-induced murine and human malignant mesothelioma

Malignant mesothelioma (MM) is an aggressive tumor with a poor prognosis mainly linked to past asbestos exposure. Murine models of MM based on fiber exposure have been developed to elucidate the mechanism of mesothelioma formation. Genomic alterations in murine MM have now been partially characterized. To gain insight into the pathophysiology of mesothelioma, 16 murine and 35 human mesotheliomas were characterized by array-comparative genomic hybridization and were screened for common genomic alterations. Alteration of the 9p21 human region, often by biallelic deletion, was the most frequent alteration in both species, in agreement with the CDKN2A/CDKN2B locus deletion in human disease and murine models. Other shared aberrations were losses of 1p36.3-p35 and 13q14-q33 and gains of 5p15.3-p13 regions. However, some differences were noted, such as absence of recurrent alterations in mouse regions corresponding to human chromosome 22. Comparison between altered recurrent regions in asbestos-exposed and non-asbestos-exposed patients showed a significant difference in the 14q11.2-q21 region, which was also lost in fiber-induced murine mesothelioma. A correlation was also demonstrated between genomic instability and tumorigenicity of human mesothelioma xenografts in nude mice. Overall, these data show similarities between murine and human disease, and contribute to the understanding of the influence of fibers in the pathogenesis of mesothelioma and validation of the murine model for preclinical testing.

Problems in mesothelioma diagnosis

Many centres are now seeing increasing numbers of patients with malignant mesothelioma. This presents pathologists involved in making the diagnosis with a number of problems, which can be divided into those encountered in making the distinction between mesothelioma and benign changes and those experienced in separating mesotheliomas from other types of epithelial and connective tissue tumours. Immunohistochemistry plays a major role in helping to make the diagnosis, but it should be interpreted with due regard to the clinical setting and radiological features, and with a knowledge of the wide morphological variations seen in mesothelioma. This review identifies some of these problems and addresses the uses and limitations of immunohistochemistry in different situations. It includes a discussion of some of the less common variants of mesothelioma and other pleural-based tumours that enter into the differential diagnosis.

The diagnostic value of Ki-67 and repp86 in distinguishing between benign and malignant mesothelial proliferations

CONTEXT

The differentiation of benign mesothelial proliferations from malignant mesotheliomas may be difficult, especially when evaluating small specimens from pleural biopsies.

OBJECTIVE

To explore the potential value of 2 proliferative cell markers, Ki-67 and restrictedly expressed proliferation-associated protein 86 kDa (repp86), in distinguishing between malignant mesothelioma (MM) and benign reactive mesothelial hyperplasia (MH).

DESIGN

Thirty-six cases of MM from 26 men and 10 women with a mean age of 62.9 years (range, 36-80 years) and 22 cases of benign reactive MH from 14 male and 8 female patients with a mean age of 51.5 years (range, 15- 88 years) were included in this study. The proliferative status of the lesions was assessed by immunohistochemistry using monoclonal antibodies to Ki-S2 (repp86) and Ki-S5 (Ki-67). The labeling indices were quantified.

RESULTS

The mean labeling indexes for Ki-67 in MM and benign reactive MH were 24.6% (range, 1%-66%) and 6.23% (range, 0%-25%), respectively. The mean labeling indexes for repp86 in MM and benign reactive MH were 26.3% (range, 0%-50%) and 3.26% (range, 0%- 21%), respectively. The average proliferative cell count was significantly higher in MM compared with benign reactive MH (P < .001). Furthermore, both markers showed a significant correlation in their expression in MM and benign reactive MH (r = 77.5, P < .001). Sensitivities of 88% and 92% and specificities of 92% and 94% were obtained at a cutoff point of 9% for Ki-67 and repp86, respectively.

CONCLUSIONS

Used in combination, Ki-67 and repp86 appear to be useful markers in differentiating MM from benign reactive MH.

Methylation profiling of mesothelioma using real-time methylation-specific PCR: a pilot study

We tested whether methylation profiles generated by real-time methylation-specific PCR (MSP) can be useful in differentiating benign, reactive mesothelial cell proliferation (RM) from malignant mesothelioma (MM). Forty-two of the 63 cases (67%) yielded informative results for RARbeta2, GPC3, CDKN2A (p16), TERT, and CCND2 (cyclinD2) gene methylation. DNA methylation of any gene was observed in much higher frequency in MM cases than RM cases (63% vs. 33%, P < 0.05). Individual gene methylation was higher in the MM than the RM cases for most of the genes; however, this was not statistically significant (RARbeta2: 58% vs. 33%, P > 0.05; GPC3: 36% vs. 27%, P > 0.05; CDKN2A: 4% vs. 0%; TERT: 4% vs. 0%), while CCND2 methylation was not detected in any case. Although preliminary, we demonstrate that real-time MSP can be applied to archival specimens and gene methylation profiling may have potential to be a useful ancillary tool to help distinguish MM from RM.

Telomerase expression in lung preneoplasia and neoplasia

Telomeres are specialized structures at eukaryotic chromosomes ends, which role is to prevent them from degradation, end to-end fusion and rearrangement. However, they shorten after each cellular division because of an incomplete DNA replication, acting in normal somatic cells as a mitotic clock for permanent proliferation arrest or senescence entry. Short telomeres are perceived as damaged DNA leading to p53/ATM pathway activation. In tumoral cells, a ribonucleoprotein complex termed telomerase enables telomere elongation. This complex, composed of 2 main components, the telomerase RNA component or hTR, the RNA template for telomere synthesis, and telomerase reverse transcriptase, the catalytic subunit, is reactivated in the majority of cancers, including those of the lung. In this review, we briefly present the main results on telomerase expression in various histological types of lung carcinoma and in bronchial carcinogenesis along with telomere attrition. Inhibition of one of the main components of the enzyme or limitation of telomere access by telomerase represent novel targets for cancer therapies and chemoprevention in high risk patients of lung cancer.

Telomeres rather than telomerase a key target for anti-cancer therapy?

It was in the 1930s that telomeres (from the Greek telos = end and meros = part) were first recognized as essential structures at the ends of the chromosomes and were shown to be important for chromosomal stability (Muller HJ: The remaking of chromosomes. The Collecting Net-Woods Hole 1938: 13: 181-198, McClintock B, The stability of broken ends of chromosomes in Zea mays. Genetics 1041: 26: 234-282). However, it was only in 1978 that the first telomeric sequence was identified -- in the protocoa Tetrahymena, a single cell organism that at a certain stage of development has many identical minichromosomes with twice as many telomeres (Blackburn EH and Gall JG. A tandemly repeated sequence at the termini of the extrachromosomal ribosomal RNA genes in Tetrahymena. J. Mol. Biol. 1978: 120: 33-53.). Today we know that telomeres form specialized, three-dimensional DNA-protein structures and fulfil important capping functions. Besides, telomeric DNA is essential as ''access DNA'' for those cells that are not able to counteract loss of DNA during replication because they do not express telomerase, the enzyme responsible for telomere length maintenance. Since telomerase is mostly found in tumor cells and inhibition correlates with telomere shortening and finally growth inhibition, telomerase and lately also the telomeres themselves have become attractive targets for anti-cancer therapy. This review aims to critically throw light on different therapeutical approaches and comes to the conclusion that telomeres may be the better targets for cancer therapeutics.

Gene expression profiling and gene copy-number changes in malignant mesothelioma cell lines

Malignant mesothelioma (MM) is an asbestos-induced tumor that acquires aneuploid DNA content during the tumorigenic process. We used instable MM cell lines as an in vitro model to study the impact of DNA copy-number changes on gene expression profiling, in the course of their chromosomal redistribution process. Two MM cell lines, PMR-MM2 (early passages of in vitro culture) and PMR-MM7 (both early and late passages of in vitro culture), were cytogenetically characterized. Genomic gains and losses were precisely defined using microarray-based comparative genomic hybridization (array-CGH), and minimal overlapping analysis led to the identification of the common unbalanced genomic regions. Using the U133Plus 2.0 Affymetrix gene chip array, we analyzed PMR-MM7 early and late passages for genome-wide gene expression, and correlated the differentially expressed genes with copy-number changes. The presence of a high number of genetic imbalances occurring from early to late culture steps reflected the tendency of MM cells toward genomic instability. The selection of specific chromosomal abnormalities observed during subsequent cultures demonstrated the spontaneous evolution of the cancer cells in an in vitro environment. MM cell lines were characterized by copy-number changes associated with the TP53 apoptotic pathway already present at the first steps of in vitro culture. Prolonged culture led to acquisition of additional chromosomal copy-number changes associated with dysregulation of genes involved in cell adhesion, regulation of mitotic cell cycle, signal transduction, carbohydrate metabolism, motor activity, glycosaminoglycan biosynthesis, protein binding activity, lipid transport, ATP synthesis, and methyltransferase activity.

The diagnosis of malignancy in effusion cytology: a pattern recognition approach

This review presents a pattern recognition approach for the diagnosis of malignant effusions. The cytomorphologic features of reactive mesothelial proliferation, mesothelioma and metastatic carcinoma are presented. In addition, the role of ancillary studies in challenging cases and the importance of integrating clinical findings are stressed. An algorithmic approach to the workup of serous effusions as well as pitfalls for false-positive diagnosis are discussed.

Praktische Differenzialdiagnose präneoplastischer Veränderungen der Pleura und früher mesothelialer Neoplasien

The morphological diagnosis of small mesothelial lesions in pleural biopsies is gaining importance in view of more aggressive, multimodal therapeutic options and of medicolegal aspects if a malignant mesothelioma is diagnosed. We present a light microscopically and immunohistochemically based morphological classification for the planning of further clinical follow-up procedures. A reactive mesothelial hyperplasia heals without scars. Mesothelial inclusions in pleuritic scars are common in recurrent pleuritis and must not be confused with an epithelioid component of a desmoplastic mesothelioma. In case of atypical mesothelial proliferations, further diagnostic procedures have to be performed to obtain a clear diagnosis of malignancy. Mesothelioma in situ is the first morphological step in neoplastic mesothelial changes, also with regard to medicolegal aspects for the unambiguous diagnosis of a mesothelioma. Early infiltrative growth is characteristic of so called early mesothelioma. A useful immunohistochemical panel for the differential diagnosis consists of anti-cytokeratin, Ck 5/6, calretinin, EMA and MiB-1, whereas the immunohistochemical detection of telomerase is not helpful.

Fluorescence in situ hybridization, comparative genomic hybridization, and other molecular biology techniques in the analysis of effusions

Over the last 20 yr, the introduction of immunocytochemistry as a diagnostic tool has dramatically revolutionized diagnostic pathology. With the introduction of molecular methods as part of the diagnostic armamentarium, the practicing pathologist is facing the new challenge of grasping novel concepts of the molecular cytogenetics era. Herein, we review the diagnostic contribution of ancillary molecular techniques, including fluorescent and chromogenic in situ hybridization, telomerase assays, loss of heterozygosity, comparative genomic hybridization (CGH), and microarray-based CGH, for the practicing cytopathologists and discuss how these techniques will help pathologists in decision-making.

Cell proliferation rate and telomerase activity in the differential diagnosis between benign and malignant mesothelial proliferations

AIMS

The differential diagnosis of malignant mesothelioma (MM) from benign mesothelial lesions (BML) based on histopathological criteria is sometimes not satisfying and causes diagnostic problems for histopathologists. We aimed to investigate whether the immunohistochemically determined cell proliferation rate and telomerase activity, using Ki-67 and human telomerase reverse transcriptase (hTERT) immunohistochemistry, respectively, are useful in the differential diagnosis of MM from BML.

METHODS

Sixty-six cases of MM (33 epithelioid, 30 biphasic and 3 sarcomatoid) and 22 cases of BML (15 reactive mesothelial proliferations and 7 fibrous pleuritis/pericarditis) were included in this study. We evaluated the proliferative activity by Ki-67 and telomerase activity by hTERT immunohistochemistries for each case.

RESULTS

The mean value of the Ki-67 proliferation index (PI) in MMs was significantly higher than that of BMLs. Biphasic MMs have higher a Ki-67 PI than epithelioid and sarcomatoid types. Ki-67 immunohistochemistry has a sensitivity of 74%, specificity of 86% and positive predictive value of 94% in detecting MM. hTERT immunohistochemistry detected MM with sensitivity and specificity of 68%.

CONCLUSION

As a result, being cheap and simple methods, Ki-67 and hTERT immunohistochemistries can be used in differentiating malignant and benign mesothelial lesions in routine formalin-fixed, paraffin-embedded material.

Differential diagnosis of benign and malignant mesothelial proliferations on pleural biopsies

CONTEXT

Although much of the pathology literature focuses on differential diagnosis of diffuse malignant mesothelioma from other types of cancer, the primary diagnostic challenge facing the pathologist is often whether a mesothelial proliferation on a pleural biopsy represents a malignancy or a benign reactive hyperplasia.

DESIGN

Based on previous medical publications, extensive personal consultations, and experience on the United States-Canadian Mesothelioma Reference Panel and the International Mesothelioma Panel, salient information was determined about interpretation of benign versus malignant mesothelial proliferations on pleural biopsies.

RESULTS

Differentiation of benign reactive mesothelial hyperplasia from diffuse malignant mesothelioma is often difficult. Benign reactive mesothelial hyperplasia may mimic many features ordinarily associated with malignancy, and diffuse malignant mesothelioma may be cytologically bland. Entrapment of benign reactive mesothelial cells within organizing pleuritis may mimic tissue invasion.

CONCLUSIONS

Various histologic clues favor a benign over a malignant mesothelial proliferation and vice versa. Invasion is the most reliable criterion for determining that a mesothelial proliferation is malignant. When there is any doubt that a pleural biopsy represents a malignancy, we recommend a diagnosis of atypical mesothelial proliferation.

Telomere repeat amplification protocol (TRAP) in situ reveals telomerase activity in three cell types in effusions: malignant cells, proliferative mesothelial cells, and lymphocytes

Telomerase Repeat Amplification Protocol (TRAP) in situ was performed on cytospin preparations from 65 effusions from the serous cavities (45 pleural and 19 ascitic fluids and one pericardial fluid) submitted for routine diagnosis and the results were correlated to cytological morphology. Three types of cells with nuclear fluorescence were identified: malignant cells, hyperplastic mesothelial cell and lymphocytes. Of 38 cytologically malignant effusions, 12 showed strong reactivity in all malignant cells, three strong reactivity in part of the malignant population, whereas 12 showed moderate reactivity in the whole and five in part of the malignant population, respectively. In five malignant effusions weak reactivity was found in all (one case) and in scattered (four cases) malignant cells. Two effusions contained telomerase-negative malignant cells. Two pleural and two ascitic fluids contained proliferative mesothelial cells with weak or, in one case, moderate reactivity. Lymphocytes usually showed weak telomerase activity. Telomerase was expressed in almost all malignant tumours metastatic to serous cavities. Heterogeneity in tumour populations was demonstrated, which may have diagnostic implications, especially in cytology. Weak or moderate reactivity was found in lymphocytes and in some mesothelial proliferations and may explain the low specificity for malignancy sometimes obtained with the TRAP extract method. The weak reactivity found in lymphocytes may reduce the specificity when the extract method is used but causes no diagnostic problem with the TRAP in situ method.

Expression profiles of p63, p53, survivin, and hTERT in skin tumors

BACKGROUND

p63 is a p53 homolog and a marker expressed in replicating keratinocytes. Survivin is a recently characterized inhibitor of apoptosis protein that is abundantly expressed in most solid and hematologic malignancies. Telomerase reverse transcriptase (TERT) is the major determinant of human telomerase activity, and its expression is indicative of unlimited replication. We herein evaluated the expression profiles of p63, p53, survivin, and hTERT in usual skin cancers, including squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) and putative preneoplastic epidermal lesions, including actinic keratosis (AK), Bowen's disease, and porokeratosis.

METHODS

Immunohistochemistry using antibodies against p63, p53, survivin, and hTERT was performed. Semi-quantitative evaluation (-, +, 2+, 3+) was carried out.

RESULTS

BCCs showed diffuse p63 expression and SCCs heterogeneous p63 expression with negativity in terminally differentiated squamous cells. All preneoplastic epidermal lesions showed p63 expression in all cell layers. p53 was found in seven of 10 cases of BCCs, all 10 cases of SCCs, and nine of 10 cases of Bowen's disease. AK and porokeratosis revealed focal to moderate p53 expression. Survivin was found in eight of 10 cases of SCCs and eight of 10 cases of Bowen's disease. Six of 10 cases of BCCs revealed weak survivin positivity. AK and porokeratosis showed survivin expression confined to the basal layer. hTERT expression was found in most cases of skin cancers and preneoplastic lesions.

CONCLUSIONS

p63 expression may be a marker of basal/progenitor cells and a diagnostic marker in skin tumors. p63 expression is not related to p53 expression in these tumors. This study points to a putative role of survivin and hTERT in the development of certain skin cancers. In addition, our data support the concept of porokeratosis being a premalignant condition.

Expression of human telomerase reverse transcriptase in thyroid follicular neoplasms: an immunohistochemical study

Differential diagnosis of follicular adenoma (FA) and follicular carcinoma (FC) of the thyroid can be difficult in the routine practice of surgical pathology because the diagnosis of FC is strictly defined and determined by the presence of capsular and/or vascular invasion by the tumor. These features may be equivocal in the histologic sections. On the other hand, telomerase is expressed in many human cancers and is thought to contribute to their immortality. Human telomerase reverse transcriptase (hTERT) is the major determinant of human telomerase activity, and its expression is suggestive of capacity for unlimited replication. This case-control study examined the expression of hTERT using immunohistochemistry in 36 thyroid FC and 36 FA from patients who were matched by age and sex. The aim was to investigate the value of immunohistochemical staining for hTERT in the differential diagnosis of follicular neoplasms. The results revealed 23 cases of FC and 14 cases of FA that showed high expression of hTERT, with moderate to strong immunoreactivity. The remaining cases showed weak or negative staining. The difference between FA and FC was statistically significant (p < 0.05). In conclusion, immunohistochemical staining for hTERT can be considered an ancillary marker for differential diagnosis of FA and FC.

Pathological anatomy and molecular pathology

The incidence of malignant mesotheliomas in Germany has increased since about the mid 1980s, and a further increase is expected until about 2020 due to the peak in asbestos processing in Germany between 1965 and 1980. About 90% of the mesotheliomas recorded in the files of the German Mesothelioma Registry in Bochum are asbestos-related and therefore possibly due to an occupational exposure. In 2003, 717 mesotheliomas were newly diagnosed at the German Mesothelioma Registry. Mesotheliomas are very heterogeneous in terms of histological appearances and of prognosis. At present, the diagnostic gold standard is conventional histology in combination with additional immunohistochemical analysis. We were not able to confirm a promising report that described telomerase reverse transcriptase catalytic subunit (TERT) for the differentiation between reactive and neoplastic mesothelial lesions, which can be extremely difficult. DNA cytometric analysis may also help differentiate between reactive and neoplastic mesothelial lesions. There are some characteristic patterns of chromosomal imbalances as detectable by comparative genomic hybridization (CGH), but at present, specific chromosomal or genetic defects that give rise to a mesothelioma are not known. A reliable pathological diagnosis is the basis for therapeutic, prognostic, and medicolegal consequences. In general, it can be achieved by thoracoscopic inspection with specifically directed biopsy. Furthermore, a description of the peculiarities of each mesothelioma by the pathologist might be the key to a more individual therapy in the future.

Gene expression profiles predict survival and progression of pleural mesothelioma

PURPOSE

Clinical outcomes for malignant pleural mesothelioma (MPM) patients having surgery are imprecisely predicted by histopathology and intraoperative staging. We hypothesized that gene expression profiles could predict time to progression and survival in surgically cytoreduced pleural mesothelioma of all stages.

EXPERIMENTAL DESIGN

Gene expression analyses from 21 MPM patients having cytoreductions and identical postoperative adjuvant therapy were performed using the U95 Affymetrix gene chip. Using both dChip and SAM, neural networks constructed a common 27 gene classifier, which was associated with either the high-risk and low-risk group of patients. Data were validated using real-time PCR and immunohistochemical staining. The 27 gene classifier was also used for validation in a separate set of 17 MPM patients from another institution.

RESULTS

The groups predicted by the gene classifier recapitulated the actual time to progression and survival of the test set with 95.2% accuracy using 10-fold cross-validation. Clinical outcomes were independent of histology, and heterogeneity of progression and survival in early stage patients was defined by the classifier. The gene classifier had a 76% accuracy in the separate validation set of MPMs.

CONCLUSIONS

These data suggest that pretherapy gene expression analysis of mesothelioma biopsies may predict which patients may benefit from a surgical approach.

Pathology of malignant mesothelioma

The diagnosis of malignant mesothelioma relies firstly on the identification of the mesothelial nature of the neoplastic cell and secondly on the demonstration of the invasive properties of the proliferation. The latter aspect cannot be achieved by studying cellular material yet, in the right clinical setting, it is often possible to make a presumptive diagnosis of malignant mesothelioma based on exudates. Differentiation between mesothelial hyperplasia and metastatic adenocarcinoma by cytological examination alone is unreliable, so further evidence can be gathered from techniques such as histopathology, histochemistry and electron microscopy. Immunohistochemistry aims to confirm the mesothelial nature of the neoplastic cells while ruling out metastatic lesions. At present there is no single reliable marker for neoplastic mesothelioma, although evidence has been presented on a large variety of gene products. In an attempt to differentiate between hyperplastic mesothelium and malignant mesothelioma, Dhaene has been able to show that over 90% of malignant mesotheliomas show telomerase activity and express telomerase subunits.

Telomeres and telomerase: a dual role in hepatocarcinogenesis

Telomere shortening limits the proliferative capacity of primary human cells and restrains the regenerative capacity of organ systems during chronic diseases and aging. Telomere shortening apparently has a dual role in tumor development and progression. On the one hand, it induces chromosomal instability and the initiation of cancer; on the other hand, tumor progression requires stabilization of telomeres. The predominant mechanism of telomere stabilization in tumor cells is the activation of the telomere-synthesizing enzyme telomerase. The potential use of telomerase activators for the treatment of regenerative disorders will ultimately depend on their effects on tumorigenesis. This review focuses on the role of telomere shortening and telomerase in carcinogenesis with a special focus on hepatocellular carcinoma.

Telomere length, telomerase activity, and expression of human telomerase reverse transcriptase mRNA in growth plate of epiphyseal articular cartilage in femoral head during normal human development and in thanatophoric dysplasia

Telomeres are important in chromosome structure and function, protecting against their degradation. However, few studies have examined telomeres in growth plates within articular cartilage during normal development. We investigated frozen sections that were obtained from 57 reference autopsy cases (aged from 16 weeks of gestation to 91 years) and from 2 patients with thanatophoric dysplasia. In the reference cases, telomere length was significantly longer in growth plates obtained from the 10 cases that were aged from 16 weeks of gestation to 10 years than in those from 47 of the adult cases (aged 20 to 91 years). In fetal, neonatal, and child cases, telomerase activity was significantly higher in the hypertrophied zone (HZ) in growth plates than in the other 3 zones. The hTERT mRNA staining intensity (staining area) was stronger (larger) in HZ and the proliferating zone than in the calcified zone and resting zone. In thanatophoric dysplasia, telomere length and telomerase activity were short and low, respectively, compared with those of normal growth plates at an equivalent age, and expression of hTERT mRNA was negative or weakly positive in all 4 zones within growth plates. These results suggest that telomere length and telomerase activity have significant effects in the growth plates of articular cartilage, particularly at developmental ages from fetus to child. We speculate that short telomere length and low telomerase activity may be important for chondrocyte differentiation in rhizomeric shortening of the limbs in thanatophoric dysplasia.

Well-differentiated papillary mesothelioma of the pleura: a series of 24 cases

Well-differentiated papillary mesothelioma (WDPM) of the pleura represents a distinct mesothelial tumor presenting with unilateral pleural effusion and superficial spreading of stout papillary formations with myxoid cores, lined by bland, flattened, or epithelioid cells, without or with limited invasion of the submesothelial layer. The majority of cases have been reported in the peritoneum in women of reproductive age with no history of asbestos exposure and also in the tunica vaginalis of men. We report 24 cases of pleural WDPM and compared their histologic, epidemiologic, and clinical features with those of classic mesothelioma. Men and women were equally affected, with a mean age of 60 years. Half of the patients had a history of occupational asbestos exposure. In 11 patients with a minimal follow-up period of 24 months, the survival ranged from 36 to 180 months with an average of 74 months as compared with 9.89 months for 1248 paired patients with diffuse malignant mesothelioma. Ten-year survival was 30.8%. We conclude that WDPM is a rare and unusual mesothelial tumor, characterized by a lack of deep invasion and associated with an indolent clinical course and long survival. For these reasons, WDPM is best considered as a specific clinico-pathologic entity distinct from conventional diffuse malignant mesothelioma.

Differential expression of telomerase reverse transcriptase (hTERT) in lung tumours

Human telomerase reverse transcriptase is a ribonucleoprotein that synthesises telomeric sequences, which decrease at each cell division. In cancer cells, its activity is linked to telomere maintenance leading to unlimited cellular proliferation and immortality. To evaluate the prognostic value of the catalytic subunit telomerase reverse transcriptase (hTERT), we analysed its expression by immunohistochemistry in 122 formalin-fixed lung tumours including 42 squamous cell carcinoma (SCC), 43 adenocarcinoma (ADC), 19 basaloid carcinoma (BC) and 18 small-cell lung carcinoma (SCLC) in comparison with detection of hTERT mRNA by in situ hybridisation and relative telomerase activity by TRAP assay in a subset of tumours. We observed a high concordance between hTERT protein expression and detection of hTERT mRNA and telomerase activity. Telomerase expression varied according to histology (P=0.0002) being significantly lower in ADC than in SCC, BC and SCLC (P<0.0001). Adenocarcinoma and SCC exhibited either a nuclear or a nucleolar staining in contrast with a diffuse nuclear staining observed in most BC and all SCLC (P=0.01). In stage I NSCLC telomerase expression was lower than in other stages (P=0.04), and a nucleolar staining was correlated with a short survival (P=0.03). We concluded that telomerase expression and pattern are distinctive among histopathological classes of lung cancer and convey prognostic influence.

Transforming growth factor alpha and epidermal growth factor receptor in reactive and malignant mesothelial proliferations

BACKGROUND

Growth factors such as transforming growth factor alpha (TGF-alpha) and epidermal growth factor receptor (EGFR) play an important role in cell proliferation. The immunohistochemical expression of these factors has been extensively studied in malignant tumors including mesothelioma. However, the comparative expression of these growth factors in mesothelioma and reactive mesothelial proliferations has been less well studied.

OBJECTIVE

To evaluate the possible role of TGF-alpha and EGFR in the clinically important distinction between reactive mesothelial proliferations and malignant mesothelioma.

METHODS

The expression of TGF-alpha and EGFR was studied in 39 cases of mesothelioma and 30 cases of reactive mesothelial proliferations by means of immunohistochemistry.

RESULTS

Fourteen (70%) of 20 reactive mesothelial proliferations tested and 29 (76%) of 38 mesotheliomas tested expressed TGF-alpha. One (3%) of 30 reactive mesothelial proliferations and 17 (45%) of 39 mesotheliomas expressed EGFR.

CONCLUSIONS

These results suggest an up-regulation of EGFR in mesothelioma as compared with reactive mesothelial proliferations. This up-regulation further suggests a possible use of EGFR as an adjunct immunohistochemical test in the differential diagnosis of mesothelioma and reactive mesothelial proliferations.

Correlation between the expression of telomerase reverse transcriptase and proliferative activity in breast cancer cells using an immunocytochemical restaining method

Telomerase activity is thought to contribute to the immortality of cancers. Recently, some investigators described a correlation between the activity of telomerase and the proliferative activity of cancer cells. The aim of this study was to evaluate the correlation between the expression of telomerase-associated protein and proliferative activity. Telomerase reverse transcriptase (TERT) is one of the proteins that correlates with telomerase activity. We investigated TERT protein and its mRNA, and examined the correlation between the TERT protein and Ki-67, which reflects proliferative activity with immunostaining, and its mRNA, which correlates with telomerase activity, using in situ hybridization. Imprint smears from 17 invasive ductal adenocarcinomas were investigated. In most cases positive for TERT mRNA, the percentage of TERT protein-positive cells was also high and was closely related to mRNA (P = 0.024). The positive rates of TERT for the cases with lymph node metastasis were significantly higher than those for the cases without metastasis (P = 0.046). The positivity of TERT protein also correlated significantly with the Ki-67-positive rate (r = 0.82). As the proliferation activity increased, the number of cells positive for both proteins also increased (r = 0.89). In conclusion, it was suggested that the expression of TERT protein is associated with the expression of Ki-67, and is concerned with maintenance of the high proliferative activity in cancer cells with aggressive proliferation.

Telomerase reverse transcriptase subunit immunoreactivity: a marker for high-grade prostate carcinoma

BACKGROUND

Telomerase, a ribonucleoprotein complex that maintains telomeric DNA, has been detected in 67-93% of prostate carcinomas by telomeric repeat-amplification protocol assay (involving polymerase chain reaction). One study used in situ hybridization in nine patients; however, to date, no immunohistochemical results have been published.

METHODS

From two hospitals, the authors compiled data on 62 patients who underwent prostatectomy from January 1996 to May 2001. Representative tissue sections were immunostained with a polyclonal antibody to telomerase reverse transcriptase (TERT), the catalytic subunit of telomerase. Staining was evaluated by two observers and was correlated with grade, stage, and biochemical failure. There were 28 sections from low-grade to intermediate-grade tumors (Gleason score, 3-6), 14 sections with a Gleason score of 3 + 4 = 7, 9 sections with a Gleason score of 4 + 3 = 7, and 11 sections from high-grade tumors (Gleason score, 8-10).

RESULTS

From low-grade to high-grade tumors, the four groups described above disclosed nuclear reactivity in 64%, 100%, 100%, and 100% of sections, respectively. Mean percentages of 5%, 15%, 40%, and 51% of nuclei were reactive in the respective groups (P < 0.0001) with intratumoral heterogeneity. The percent of reactive tumor nuclei was not correlated with pathologic stage (P = 0.32) or margin status (P = 0.35). The basal cell layer in sections of high-grade prostatic intraepithelial neoplasia (HGPIN) and benign/atrophic acini was reactive; secretory cells were reactive in 13 of 34 HGPIN foci (38%) in 1-20% of nuclei and were never reactive in benign acini. Lymphocytes and skeletal muscle were reactive. Weak, nonspecific, cytoplasmic staining was noted in benign and tumor acini.

CONCLUSIONS

Like cytokeratin 34betaE12, nuclear anti-TERT reactivity is a basal cell marker in nonneoplastic prostatic acini. Anti-TERT reactivity is acquired by secretory cells in tumorigenesis, but consistent reactivity is restricted to high-grade carcinoma (Gleason primary pattern >or=4). This histologic evidence suggests that higher grade tumors have maximally activated telomerase and may be most responsive to antitelomerase therapy.

Molecular cytogenetic differences between histological subtypes of malignant mesotheliomas: DNA cytometry and comparative genomic hybridization of 90 cases

It is established that subtypes of human malignant mesotheliomas (MM) are associated with different survival times. Ninety cases of MM were examined using DNA cytometry and comparative genomic hybridization (CGH), with emphasis on the main histological subtypes; epithelioid, sarcomatoid and biphasic. A comparison by DNA cytometry revealed moderate differences, with the rare subgroup of mesodermomas having the highest and the sarcomatoid group the lowest rate of aneuploidy. Using CGH, 6.2 chromosomal imbalances per case on average could be detected. Losses (4.1/case) were more common than gains of chromosomal material (2.1/case). MM show no single, specific defect, but a typical pattern of genomic defects can be attributed to this tumour entity. Common losses are clustered at the chromosomal regions 9p21 (34%), 22q (32%), 4q31-32 (29%), 4p12-13 (25%), 14q12-24 (23%), 1p21 (21%), 13q13-14 (19%), 3p21, 6q22, 10p13-pter and 17p12-pter (16% each). Common gains are located on 8q22-23 (18%), 1q23/1q32 (16%), 7p14-15 and 15q22-25 (14% each). While differences in the frequencies of the defects between epithelioid and sarcomatoid MM are not as pronounced as are seen with the pleomorphic mesodermomas, several chromosomal locations (3p, 7q, 15q, 17p) show significant variations. The most pronounced distinguishing feature of sarcomatoid MM is a more than fourfold higher number of amplicons. These data indicate that MM has a distinctive tumour biology with a broad spectrum of heterogeneity, as reflected in morphology and also, more subtly, in the patterns of chromosomal imbalances of the subtypes.