hTERT expression in melanocytic lesions: an immunohistochemical study on paraffin-embedded tissue

An overview of the role of telomeres and telomerase in pre‑neoplastic lesions (Review)

Telomeres are tandem repeats of DNA sequences protecting the end of linear chromosomes. Replicative senescence due to telomere attrition is considered a tumor-preventing mechanism in differentiated somatic cells. However, telomere shortening is associated with genome instability and several disease entities. During carcinogenesis, the development of a telomere maintenance mechanism, predominately through the activation of the telomerase enzyme, represents a hallmark of cancer, since it enables cancer cells to avert senescence and divide indefinitely. Although research of the involvement of telomeres and telomerase in various malignant neoplasms has gained a large amount of interest, the timing and relevance of their role in pre-neoplastic lesions remain to be determined. The present narrative review aims to summarize the evidence regarding the role of telomeres and telomerase in pre-neoplasia across different types of tissues.

Differential Immunoexpression of BRAF/V600E, Senescence Markers, PTEN, and T-type Calcium Channels in Acquired Naevi According to their Histopathological and Dermoscopic Classification

BRAF/V600E mutation and other cell growth/growth-control mechanisms are involved in naevogenesis and melanomagenesis. Immunoexpression of BRAF/V600E and other molecules (p16, phosphatase and tensin homologue (PTEN), Ki67, hTERT and Cav3.1 and 3.2 calcium channels) were investigated in 80 histopathologically and dermoscopically classified acquired naevi. Regarding BRAF/V600E, dysplastic naevi showed lower immunostaining than common naevi, which was significant in comparison with intradermal naevi, which showed the highest BRAF/V600E histoscore. Junctional naevi showed the lowest BRAF/V600E levels. Globular/cobblestone and reticular dermoscopic patterns were consistently associated with high and low BRAF/V600E immunoexpression, respectively, but Zalaudek’s peripheral globule pattern (CR/PG) showed the highest BRAF/V600E immunoexpression. Among global patterns, the previously not investigated multicomponent pattern showed the lowest BRAF/V600E immunoexpression. Regarding the remaining biomarkers, new immunohistochemical features were found, in particular p16 and PTEN low expression in multicomponent pattern; and Ki67, hTERT and Cav.3.1 high expression in CR/PG. In conclusion, histopathology and dermoscopy provide complementary information regarding the biology of melanocytic naevi.

Atypical Spitzoid neoplasms: a review of potential markers of biological behavior including sentinel node biopsy

Atypical cutaneous melanocytic lesions, including those with Spitzoid features, can be difficult to categorize as benign or malignant. This can lead to suboptimal management, with potential adverse patient outcomes. Recent studies have enhanced knowledge of the molecular and genetic biology of these lesions and, combined with clinicopathological findings, is further defining their biological spectrum, classification, and behavior. Sentinel node biopsy provides important prognostic information in patients with cutaneous melanoma, but its role in the management of melanocytic lesions of uncertain malignant potential (MELTUMP) is controversial. This paper examines the role of molecular testing and sentinel node biopsy in MELTUMPs, particularly atypical Spitzoid tumors.

Molecular markers and bladder carcinoma: Schistosomal and non-schistosomal

OBJECTIVES

Detection of telomeric repeat amplification protocol (TRAP) activity, the human telomerase reverse transcriptase (hTERT), tumor suppressor gene (p53) and proliferating marker (MIB-1) in bladder specimens.

DESIGN AND METHODS

Specimens were obtained from 85 patients and 10 controls. TRAP technique and immunohistochemistry (IHC) method were performed.

RESULTS

TRAP activity, hTERT, p53 and MIB1 were detected in 62.4%, 65.9%, 57.6% and 62.4% of all 85 patient cases, respectively. TRAP activity was detected in 75% of schistosomal urothelial carcinoma, 100% in schistosomal squamous cell carcinoma (SQCC) and 71.4% in non-schistosomal urothelial carcinoma. hTERT protein was detected in schistosomal urothelial carcinoma (83.3%), 93.3% in schistosomal SQCC and 75.7% in non-schistosomal urothelial carcinoma.

CONCLUSIONS

TRAP and hTERT are useful for the detection of telomerase with special emphasis on their role in the detection of schistosomal-associated bladder cancer. Correlation of TRAP and hTERT protein with MIB1 and p53 reveals the importance of telomerase as a new marker in cancer bladder.

Immunohistochemistry for human telomerase reverse transcriptase catalytic subunit (hTERT): a study of 143 benign and malignant soft tissue and bone tumours

AIMS

Only a small number of mesenchymal tumours have been previously evaluated for hTERT expression. We hypothesised that hTERT expression would be frequently present in sarcomas, but not in benign tumours.

METHODS

Sections from 143 bone/soft tissue tumours were immunostained for hTERT (44F12, 1:20; Novocastra) using steam heat-induced epitope retrieval and the Dako Envision system. Normal lymphocytes served as positive internal controls. Positive cases showed 'speckled' nuclear/nucleolar staining in >10% of cells, in accordance with previous studies. Fisher's exact test was used for statistical analysis. The result was checked against the G test and Chi-squared test with Yates correction, and was concordant.

RESULTS

hTERT expression was seen in nine of 71 (13%) benign and 33 of 72 (46%) malignant tumours (p > or = 0.001). hTERT was positive in >50% of osteosarcomas, malignant peripheral nerve sheath tumours, liposarcomas, and angiosarcomas. All positive sarcomas were high grade (FNCLCC grade II or III). Among benign tumours, only schwannomas and chondromas were positive in >30% of cases. Positive normal tissues included lymphocytes, multinucleated histiocytes, keratinocytes, adnexal glands, hepatocytes and basal cells of respiratory mucosa.

CONCLUSIONS

hTERT expression is significantly more common in sarcomas as compared with benign tumours. Restriction of hTERT expression to high grade lesions, and its absence in low grade sarcomas (including the well-differentiated component of dedifferentiated liposarcoma), suggests that telomerase activation is a late event in sarcoma progression. Importantly, however, hTERT can be expressed in some benign tumours, notably schwannoma and chondroma, and it is doubtful that hTERT expression alone will allow the discrimination of benign from malignant soft tissue/bone tumours. Importantly, hTERT expression is often only focal and its identification may require careful evaluation of an entire section, suggesting that this technique is best applied to whole sections, rather than tissue microarrays.

Expression of activated Akt in benign nevi, Spitz nevi and melanomas

BACKGROUND

Activated Akt expression (p-Akt) is reportedly increased in many melanomas as compared with benign nevi. The purpose of this study was to evaluate and compare p-Akt immunohistological staining in benign nevi, Spitz nevi and primary melanomas.

METHODS

Immunostaining for phosphorylated Akt was performed in 41 melanocytic lesions previously classified as benign intradermal nevus (14 lesions), Spitz nevus (9 lesions) or melanoma (18 lesions). Lesions were graded for intensity of p-Akt staining by two independent observers (0, no staining; 1, slightly positive; 2, moderately positive; 3, highly positive). Scores were averaged, and statistical analyses were performed.

RESULTS

Benign nevi showed less staining (mean score 1.18) compared with Spitz nevi (mean score 2.11) and melanomas (mean score 2.19). This difference was statistically significant between benign nevi and melanomas (p = 0.0047) and benign nevi and Spitz nevi (p = 0.0271). No statistical difference was detected in staining between Spitz nevi and melanomas (p = 0.8309).

CONCLUSIONS

Activated Akt expression is increased in Spitz nevi and melanomas as compared with benign intradermal nevi, but is unlikely to prove useful in differentiating between the former.

Telomerase expression in sebaceous lesions of the skin

BACKGROUND

Recent studies have demonstrated telomerase expression in ophthalmologic sebaceous carcinoma and have suggested possible diagnostic utility in distinguishing these neoplasms from sebaceous adenomas. The aim of this study was to evaluate telomerase expression via human telomerase reverse transcriptase (hTERT) immunohistochemical staining in a spectrum of sebaceous lesions of the skin.

METHODS

Paraffin-embedded sections from sebaceous hyperplasia (11), nevus sebaceus (22), sebaceous adenoma (19), sebaceoma (11), and sebaceous carcinoma (14) were evaluated for intensity (0 to 3+) and pattern of anti-hTERT staining.

RESULTS

Strong (2 to 3+) hTERT staining was observed in nucleoli of germinative cells and immature sebocytes in all sebaceous lesions, whereas mature sebocytes were negative. The distribution pattern paralleled features seen by routine haematoxylin and eosin-stained sections.

CONCLUSIONS

All hyperplastic and neoplastic sebaceous skin lesions expressed hTERT in this immunohistochemical study. The pattern of staining was predictive of the histologic pattern of the process but does not significantly add to our diagnostic armamentarium of sebaceous lesions.

BRAF and NRAS mutations in spitzoid melanocytic lesions

BRAF mutations are common events in a variety of melanocytic nevi and primary cutaneous melanomas. We have previously found BRAF mutations in 82% of nevi, consisting of congenital, common acquired and dysplastic types, and 33% of primary cutaneous melanomas other than the spitzoid type, similar to other published reports. A small number of studies have evaluated Spitz nevi and have failed to detect any lesions possessing a BRAF mutation. Only one study included categories of atypical Spitz nevus and borderline lesions suspected to be spitzoid melanomas, along with classic Spitz nevi and spitzoid melanomas. We examined a spectrum of spitzoid lesions that included 48 Spitz nevi, some with atypical features, seven atypical (borderline) Spitz tumors, and 13 spitzoid melanomas. BRAF mutations were detected in 12 of 68 spitzoid lesions, of which two were spitzoid melanomas and 10 were Spitz nevi. Five of the 10 Spitz nevi with BRAF mutations were altered by more than usual cytologic atypia and/or architectural atypia overlapping with dysplastic nevi, or irritation/inflammation; one desmoplastic Spitz nevus had a BRAF mutation. These results indicate that a small subset of Spitz nevi, some with atypical histologic features, possess BRAF mutations. Therefore, the BRAF mutational status does not separate all Spitz nevi from spitzoid melanomas and non-Spitz types of melanocytic proliferations, contrary to previous reports.

Telomerase in anti-tumor response

Telomerase is responsible for maintaining the length of telomeres at the end of chromosomes. It protects chromosomes from degradation and aberrant recombination during replication prolonging the life span of the cell. Human telomerase reverse transcriptase (hTERT) is highly expressed in >85% of cancer cells but its expression is repressed in most human somatic cells. It has been shown that expression of human telomerase reverse transcriptase greatly extends the life span of both human CD8+ and CD4+ T cells during activation and proliferation. hTERT-positive tumor cells can induce cytotoxic T lymphocyte response as well as T helper response. On the other hand, it is possible that cytotoxic immune response to hTERT-positive tumor cells can cause autoimmune reaction directed against T cells in a tumor bearing host. This could lead to apoptosis and decreased number of activated T cells and insufficient anti-tumor immunity resulting in tumor progression.

Immunohistochemical detection of hTERT in urothelial lesions: a potential adjunct to urine cytology

BACKGROUND

Urine cytology has a critical role in evaluation for bladder carcinoma. Due to the low sensitivity of this technique, ancillary modalities such as the detection of markers of malignancy by immunochemistry are desirable. Promising factors in this context are components of the human telomerase enzyme complex. Telomerase repairs and extend telomeres, which when eroded beyond a critical limit trigger a senescence checkpoint. Accordingly, while absent in normal somatic cells, telomerase activity has been detected in the great majority of malignant tumor specimens tested, and so has potential value for the recognition of malignant cells in clinical specimens.

METHODS

In this study, we investigated whether the immunohistochemical detection of the catalytic subunit of telomerase (hTERT) can aid cytology in the diagnosis of bladder lesions. Findings from the retrospective evaluation of over 100 cell blocks, including urine sediments from confirmed malignant and benign conditions, were compared with routine urine cytology data.

RESULTS

The presence of hTERT protein was indicative of the transformation of urothelia to a malignant phenotype. Nucleolar hTERT was expressed in 27 (93%) of 29 samples obtained from patients with confirmed primary bladder cancer. Conversely, hTERT was detectable in only 3 (0.8%) of 39 samples from benign conditions. The hTERT assay showed higher diagnostic sensitivity (84.8%) than published urine cytology data (approximately 65%) for confirmed bladder carcinoma, however, the hTERT assay was less specific than cytology (65.2% vs. approximately 95% respectively).

CONCLUSION

As a highly sensitive marker, immunohistochemical hTERT detection in urine sediments represents a reliable adjunct to cytology in the accurate diagnosis of urothelial neoplasms.

Immunodetection of human telomerase reverse-transcriptase (hTERT) re-appraised: nucleolin and telomerase cross paths

The involvement of telomerase in cellular immortalization and senescence has often been assessed by means of telomerase expression at the RNA level and quantification of telomerase activity by the telomeric repeat amplification protocol assay. However, these methods either neglected the existence of various telomerase splice variants, or ignored the nonconventional functions of telomerase independent of its ability to elongate and maintain telomere length. Immunodetection of telomerase is now being recognized as a necessary approach to precisely elucidate its roles in oncogenesis and senescence. A few antibodies directed against the catalytic subunit of the human telomerase (hTERT) are currently used but their specificity is not always demonstrated. A survey of the literature showed inconsistencies and led us to comparatively re-evaluate the most frequently used antibodies. Surprisingly, mass spectrometry, two-dimensional gel analysis and immunofluorescent experiments revealed that the most frequently used hTERT immunoprobe, a mouse monoclonal antibody that was claimed to be directed against an hTERT protein epitope, in fact recognizes nucleolin rather than telomerase. Our findings have interesting implications regarding the biology of nucleolin and telomerase in the context of pathophysiological investigations recently carried out.