Expression of human telomerase reverse transcriptase in lymphangioleiomyomatosis

Intracrine steroid production and mammalian target of rapamycin pathways in pulmonary lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare, potentially fatal disease primarily affecting young women. Estrogens enhance cell proliferation and progression of the tumor. Clinical trials using molecularly targeted agents such as endocrine manipulation and mammalian target of rapamycin (mTOR) inhibitors are in progress, but the status of these molecules, including aromatase and mTOR, has not been explored in LAM tissue. We first examined immunoreactivity for sex steroid receptors (estrogen receptor [ER] α, ERβ, progesterone receptor, androgen receptor), sex steroid-synthesizing enzymes (aromatase, steroid sulfatase, 17β-hydroxysteroid dehydrogenase 1, 5α-reductases), apoptotic suppression factor (Bcl-2), and factors involved in the mTOR signaling pathway in 30 pulmonary LAM tissues. Immunoreactivity for ERα, ERβ, progesterone receptor, aromatase, and Bcl-2 was significantly more abundant in epithelioid cells, whereas the status of androgen receptor, 5α-reductases, and phospho-mTOR signaling was not different in epithelioid and spindle-shaped LAM cells. We further examined the correlation among H scores of these markers using hierarchical clustering analysis. The results indicated that LAM tumors can be further classified into "aromatase" and "mTOR" groups on the basis of the patterns of immunoreactivity, and the 2 types could benefit from different modes of therapy.

In silico evaluation of TERT inhibition by anticancer drugs

The activation of telomerase represents an early step in carcinogenesis. Increased telomerase expression in malignant tumors suggests that telomerase inactivation may represent a potential chemotherapeutic target. In this work, existing anticancer drugs were docked against telomerase reverse transcriptase (TERT) using a Lamarckian genetic algorithm (LGA). Autodock's scoring function was applied to each of the molecules in order to identify the inhibitor with the strongest pharmacological action. The structural insights provided by this study regarding binding poses and possible interactions, free energies of binding, and drug scores aided in the identification of potential inhibitory compounds. The ranks of the various ligands investigated were based on the final docked energy values. Among nine selected compounds, vindesine, temsirolimus, and cyclosporine were found to be more potent TERT inhibitors than the standard inhibitor, curcumin.

Telomerase detection in the diagnosis and prognosis of cancer

Telomerase, a critical enzyme responsible 'for cellular immortality, is usually repressed in somatic cells except for lymphocytes and self-renewal cells, but is activated in approximately 85% of human cancer tissues. The human telomerase reverse transcriptase (hTERT) is the catalytic component of human telomerase. In cancers in which telomerase activation occurs at the early stages of the disease, telomerase activity and hTERT expression are useful markers for the detection of cancer cells. In other cancers in which telomerase becomes upregulated upon tumor progression, they are useful as prognostic indicators. However, careful attention should be paid to false-negative results caused by the instability of telomerase and of the hTERT mRNA and the presence of PCR inhibitors, as well as to false-positive results caused by the presence of alternatively spliced hTERT mRNA and normal cells with telomerase activity. Recently, methods for the in situ detection of the hTERT mRNA and protein have been developed. These methods should facilitate the unequivocal detection of cancer cells, even in tissues containing a background of normal telomerase-positive cells.

Telomerase as tumor marker

Telomerase, a critical enzyme responsible for continuous cell growth, is repressed in most somatic cells except proliferating progenitor cells and activated lymphocytes, and activated in approximately 85% of human cancer tissues. Telomerase activity is a useful cancer-cell detecting marker in some types of cancers in which almost all cases show telomerase activation. In other types in which telomerase becomes upregulated according to tumor progression, it is a useful prognostic indicator. Detection of human telomerase reverse transcriptase (hTERT) mRNA or protein in various clinical samples is also applicable. However, careful attention should be paid to the false negative results due to the instability of this enzyme or hTERT mRNA and the existence of polymerase chain reaction inhibitors as well as the false-positive results due to the contamination by normal cells with telomerase activity. If these pitfalls are avoided, in situ detection of hTERT mRNA or protein will facilitate the reliability of telomerase as a tumor marker.