title: Thyroglobulin may affect telomerase activity in thyroid follicular cells.
abstract: Telomerase (TA) activity is known to be present in malignant tumor cells, but not in most somatic differentiated cells. TA shows relatively high activity in thyroid cancer cells, but reports vary. This fact prompted us to elucidate whether cell component inhibitors of TA in the thyroid follicles can modulate its activity. The activity of TA extracted from Hela cells was inhibited by mixing with the supernatant fraction of human thyroid tissue extract. To examine the effect of iodine, thyroid hormones (l-T3 and l-T4) and human thyroglobulin (hTg) contained in the thyroid follicles, l-T3, l-T4 and hTg were added to the TRAP assay system in vitro, using TA from Hela cells. Iodine, l-T3 and l-T4 did not affect TA activity, but hTg inhibited the TA activity in a dose-dependent manner (IC(50) of hTg: ca 0.45 microM: inhibiting concentration of hTg was from 0.15 microM to 3.0 microM). The hTg inhibition was not evident in the RT-PCR system, suggesting no effect of hTg on Taq DNA polymerase activity. The hTg inhibition of TA activity was attenuated by dNTP but not significantly by TS primer. These data suggest that hTg contained in thyroid follicular cells of various thyroid diseases may affect the TA activity measured in biopsied thyroid specimens, and that the reduction of the TA activity by hTg may induce slow progression and growth, and low grade malignancy of thyroid cancer, particularly differentiated carcinoma.
authors.affiliation: Department of Internal Medicine, Fujita Health University School of Medicine, Toyoake, Aichi, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Nagasaka
authors.forename: Naohisa
authors.initials: N
authors.lastname: Oda
authors.forename: Akira
authors.initials: A
authors.lastname: Nakai
authors.forename: Keiko
authors.initials: K
authors.lastname: Hotta
authors.forename: Mutsuko
authors.initials: M
authors.lastname: Nagata
authors.forename: Taiya
authors.initials: T
authors.lastname: Kato
authors.forename: Atsushi
authors.initials: A
authors.lastname: Suzuki
authors.forename: Mitsuyasu
authors.initials: M
authors.lastname: Itoh
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Miura
authors.forename: Motoo
authors.initials: M
authors.lastname: Hakuta
authors.forename: Shonen
authors.initials: S
authors.lastname: Yoshida
authors.forename: Yatsuka
authors.initials: Y
authors.lastname: Hibi
authors.forename: Katsumi
authors.initials: K
authors.lastname: Iwase
mesh_terms: D018265:Carcinoma, Papillary, Follicular / Q000201:enzymology / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006367:HeLa Cells; D006801:Humans; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019098:Telomerase / Q000378:metabolism*; D013954:Thyroglobulin / Q000494:pharmacology*; D013961:Thyroid Gland / Q000201:enzymology* / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000201:enzymology / Q000378:metabolism; D013997:Time Factors
chemical_list: D013954:Thyroglobulin; D019098:Telomerase