Localization of Telomerase hTERT Protein and hTR in Benign Mucosa, Dysplasia, and Squamous Cell Carcinoma of the Cervix

Abstract

Telomerase has been detected by telomerase repeat amplification protocol (TRAP) assay in cervical dysplasia and squamous cell carcinoma but not in most normal cervical tissues. In the present study, the cellular localization of the protein catalytic subunit of telomerase (hTERT) and the RNA component (hTR) were investigated by a sensitive immunohistochemical technique and by in situ hybridization, respectively. hTERT protein was detected in all diagnostic categories of cervical specimens. hTERT was localized predominantly to the lower suprabasal levels of normal squamous mucosa but was detected throughout virtually all levels of the lesional epithelium in low-grade squamous intraepithelial lesions (LSILs), high-grade squamous intraepithelial lesions (HSILs), and squamous cell carcinoma (SCC). Telomerase expression correlated with hTERT detection in SCC and HSIL but was not detected by TRAP assay in most samples of normal mucosa or LSIL. The distribution of hTR correlated with the localization of hTERT in HSIL and SCC but was restricted to the basal and suprabasal cell layers in normal mucosa and LSIL.

Analysis of telomerase as a diagnostic biomarker of cervical dysplasia and carcinoma

“…Less sensitive methods have failed to reveal speci®c localization of telomerase in our hands, although other groups have reported success in some tissues using conventional avidin ± biotin-based immunoperoxidase methods . Studies in our laboratory showed that hTERT protein is predominantly localized to lower portions of the suprabasal squamous cells of normal or benign-reactive cervical mucosa (Frost et al, 2000). By contrast, almost fullthickness distribution of nuclear staining was observed in nearly all cases of moderate and severe dysplasia (Frost et al, 2000).…”

“…In situ hybridization has demonstrated that hTR is largely restricted to the basal and parabasal cell layers of ectocervical mucosa, metaplastic squamous epithelium, or LSIL, although focal expression has also been observed in some histologically normal endocervical glands (Yashima et al, 1998;Frost et al, 2000). By contrast, hTR was detected throughout all layers of the lesional mucosa in moderate dysplasia, severe dysplasia, and in carcinoma in situ (Yashima et al, 1998;Frost et al, 2000;Wisman et al, 2000). Nakano et al (1998) demonstrated that hTR and hTERT mRNA are colocalized in cervical SCCs as well as in benign and dysplastic cervical mucosa biopsy specimens.…”

“…The expression of hTR appears to be heterogeneously distributed in SCCs and is related to the degree of tumor cell di erentiation. In general, terminally di erentiated components of SCCs, including squamous pearls, are negative for hTR (Yashima et al, 1998;Frost et al, 2000) and the distribution of hTERT mRNA has also been shown to have regional variability in some cases (Nakano et al, 1998). Thus, tumor heterogeneity in telomerase expression could in¯uence the analysis of telomerase.…”

“…Recent studies have detected the hTERT protein in archival formalin-®xed cervical mucosal biopsy specimens using a highly sensitive tyramide-based indirect immunoperoxidase method (Frost et al, 2000). Less sensitive methods have failed to reveal speci®c localization of telomerase in our hands, although other groups have reported success in some tissues using conventional avidin ± biotin-based immunoperoxidase methods .…”

Innovations in understanding the biology of cervical cancer

“…17,24,25 Telomerase is a ribonucleoprotein DNA polymerase containing an RNA component, designated hTR, and a single catalytic protein subunit, human telomerase reverse transcriptase (hTERT), which directs the synthesis of telomeric DNA repeats. Telomerase contributes to cellular immortalization as a fundamental component of the processes of malignant transformation and may play a central role in HPV-mediated transformation of the cervical mucosa.…”