Sonic Hedgehog Protein Expression in Various Thyroid Tissues and Its Clinical Implication / 대한내분비외과학회지

PURPOSE: The Hedgehog (Hh) signaling pathway is important in embryonic development including cell differentiation and proliferation. Recently, activation of this pathway has been implicated in several forms of solid cancers. We investigated sonic hedgehog (Shh) protein expression and its relation to differentiation and clinicopathologic characteristics in thyroid cancer cell lines and tissues. METHODS: FTC-236, FTC-238, and XTC-1. We made tissue microarray slides using 80 thyroid surgical specimen: 40 benign and 40 malignant lesions. Immunohistochemical staining was performed using anti-Shh antibody. mRNA expression of NIS, thyroglobulin, and CD97 were evaluated by RT-PCR. Cyclopamine was used as a Shh signal inhibitor. RESULTS: Shh expression was more prominent in TPC-1, FTC-133, and XTC-1 cell lines than the others. Cyclopamine downregulated CD97 and upregulated thyroglobulin mRNA expression, but did not induce mRNA expression of NIS. Thyroid tissues showed varied expression of Shh in both benign and malignant diseases. Shh expression was detected in 38 of 50 (76%) normal, in 18 of 25 (72%) non-neoplastic benign, in nine of 15 (60%) benign tumors, and in 31 of 40 (77%) malignant tumors. Shh over-expression was significantly less frequent in papillary thyroid carcinomas than in normal or benign thyroid tissues. In addition, Shh protein expression did not relate to clinicopathologic characteristics in papillary thyroid carcinomas. CONCLUSION: Thyroid tissues and cell lines vary in expression of Shh. Cyclopamine can induce redifferentiation in thyroid cancer cell lines. Shh protein expression, however, is unrelated to clinicopathologic characteristics in papillary thyroid carcinomas.

The Antiproliferative and Redifferentiative Effects of Na-4-Phenylbutyrate in Human Thyroid Cancer Cell Lines

PURPOSE: Sodium-4-phenylbutyrate (Na-4-PB) is an analogue of phenylacetate, which is a well-known redifferentiating agent. In vitro and in vivo studies on this agent have been done and the clinical relevance of Na-4-PB has been studied in other malignancies, but not in thyroid cancer. We investigated the effect of Na-4-PB on cell proliferation and differentiation in thyroid cancer cell lines. METHODS: We used 5 thyroid cancer cell lines: TPC-1, FTC-133, FTC-236, FTC-238 and XTC-1. MTT assay and flowcytometry were used to measure the agent's antiproliferative effects and the cell cycle change. We evaluated the PPARgamma expression via western blotting and the mRNA expressions of NIS, Tg and CD 97 were determined by performing RT-PCR. Troglitazone, a potent PPARgamma agonist, was used in combined treatment with Na-4-PB. RESULTS: Na-4-PB inhibited cell proliferation in a dose and time dependent manner in all 5 thyroid cancer cell lines. By performing flowcytometry in the FTC-133 and TPC-1 cell lines, we identified that the antiproliferative effect of Na-4-PB was associated with an increased apoptotic cell population. Treatment with Na-4-PB upregulated the PPARgamma expression, but the combined treatment of Na-4-PB with troglitazone did not seem to be synergistic for the antiproliferative effect. Treatment with Na-4-PB downregulated the CD97 mRNA expression and it upregulated the NIS and Tg mRNA expressions in both the FTC-133 and TPC-1 cell lines. CONCLUSION: Na-4-PB inhibited thyroid cancer cell proliferation by inducing apoptosis in a dose dependent manner. Treatment with Na-4-PB increased the expression of PPARgamma and it upregulated such differentiation markers as NIS and Tg, and it downregulated CD97, a dedifferentiation marker. Na-4-PB should be further evaluated as a new potential therapeutic agent for patients with thyroid cancer.

Cyclopamine Inhibits Cancer Cell Proliferation in Thyroid Cancer Cell Lines / 대한내분비외과학회지

PURPOSE: The Hedgehog (HH) signaling pathway is important in development. Recently,ectopic activation of this pathway has been implicated in several forms of solid cancer including basal cell carcinoma, pancreatic cancer, colon cancer, and prostate cancer. There are three HH proteins involved in the pathway: Sonic HH, Indiana HH, and Desert HH. Cyclopamine disrupts Sonic HH signaling by inhibition of the seven-transmembrane receptor Smoothened (SMO). Whereas cyclopamine is cytotoxic to several human cancer cells, its effect on thyroid cancer cellsis unknown. We therefore investigated the effect of cyclopamine on cell proliferation in human thyroid cancer cell lines. METHODS: We used fivethyroid cancer cell lines: TPC-1 (papillary), FTC-133, FTC-236, FTC-238 (follicular), and XTC-1 (Hurthle cell). The MTT assay and cell cycle analysis were used to evaluate anti-proliferative effects. Tomatidine, a structural analogue of cyclopamine, was used as a control agent. Statistical significance was tested by ANOVA. RESULTS: After 4 days of treatment, the percent inhibition of growth with a concentration of 5, 10, and 20 M cyclopamine in the cell lines were 23.6±4.9%, 66.4±4.7% and 69.3±1.3% in TPC-1 7.5±2.8%, 10.7±3.2% and 49.6±6.4% in FTC-133, 19.2±9.5%, 50.4±4.8% and 60.4±2.0% in FTC- 236 22.8±4.2%, 53.4±5.5% and 63.7±4.8% in FTC- 238 7.6±5.8%, 16.6±2.2%, 24.0±4.3% in XTC-1. Treatment with tomatidine at the same concentrations did not significantly affect cell growth. Exposure to cyclopamine, however, did not affect the cell cycle significantly CONCLUSION: Cyclopamine inhibits cancer cell proliferation in a dose dependent manner in thyroid cancer cell lines. The Hh signaling pathway might be a useful therapeutic target for thyroid cancer.

New Promising Therapeutic Modalities for Thyroid Cancers: Histone Deacetylase Inhibitor, PPAR-gamma Agonist, and Retinoic Acid / 대한내분비외과학회지

Most patients with thyroid cancer have well differentiated tumors that usually respond to conventional therapy including total or near total thyroidectomy, radioiodine ablation and TSH suppression. About 10% of patients, however, have aggressive cancers as a consequence of de-differentiation. During de-differentiation, thyroid cancers not only show more mitosis, fibrosis, and altered cell structure, they also lose thyroid-specific functions (iodine uptake, TSH receptor expression, and thyroglobulin production). These poorly differentiated or undifferentiated tumors mostly fail to take up radioiodine and are responsible for most deaths from thyroid cancer. New therapies need to be developed for patients with these types of tumors. Among the most promising antineoplastic therapies for these poorly differentiated and undifferentiated thyroid cancers are the histone deacetylase inhibitors, the PPAR-gamma agonist and retinoic acids. These drugs have therapeutic effects for thyroid cancers in inhibiting growth and inducing apoptosis and redifferentiation, in vivo and in vitro studies. And, clinical trials in patients with refractory thyroid cancers have been initiated. Further laboratory investigation of these drugs is necessary to understand molecular mechanisms and demonstrate therapeutic efficacy for thyroid cancers.

Regulation of Sodium-iodine Symporter Expression by Retinoic Acid in Thyroid Cancer Cell Lines / 대한내분비외과학회지

PURPOSE: Response to radioiodine therapy for thyroid cancer is related to the loss of sodium-iodine symporter protein caused by dedifferentiation of thyroid cancer cells. So we aimed to study mRNA expression of CD97, dedifferentiation marker, and sodium-iodine symporter after retinoic acid treatment according to retinoids receptor status. METHODS: Thyroid cancer cell lines; ARO, FRO, NPA, TPO, and FTC133 were prepared. 5µM of all trans retinoic acid were administered to each cell lines and then expression of m RNA for retinoids receptors (RARα, RARβ, RARγ, RXRα, RXRβ, RXRγ), CD97, and Sodium-Iodine symporter by RT-PCR. RESULTS: RARs and RXRs were differently expressed in each cell line. After retinoic acid treatment, relative density of retinoic acid receptor mRNA were increased by time dependently in each cell line except TPO cell line. Expression of CD97 also was decreased in every cell lines (P<0.001). Retinoic acid increased expression of sodium-iodine symporter only in FTC133 cell line (P<0.001), and TSH or forskolin did not enhance NIS expression by retinoic acid. RARβ and RXRγ were expressed only in FTC 133cell line before treatment. Induction of sodium-iodine symporter by retinoids disappeared after RARβ specific antagonist LE135 or pan RXR antagonist PA452 administration. CONCLUSION: Retinoic acid reduced expression of CD97 in five thyroid cancer cell lines. However, retinoic acid could restore sodium-iodine symporter expression in only FTC 133 cell line specifically containing RARβ and RXRγ. Restoration of sodium-iodine symporter expression by retinoic acid is related to RARβ and RXRγ expression.

Redifferentiation Effects of Troglitazone in Human Thyroid Cancer Cell Lines

PURPOSE: Troglitazone is a potent agonist for the peroxisome proliferator-activated receptor-gamma (PPARgamma), which is a ligand-activated transcription factor that regulates cell differentiation and growth. Antiproliferative effects of troglitazone have been reported in several human cancers including thyroid cancer. In the present study, we evaluated the redifferentiation effects of troglitazone in human cancers regarding the modulation of CD97 and sodium-iodide symporter (NIS) gene expression. METHODS: We used 3 human thyroid cancer cell lines: TPC-1 (papillary), FTC-133 (follicular), and XTC-1 (H rthle). Surface expression of CD97, a novel dedifferentiation marker, was measured by flow cytometry. mRNA expression of NIS gene was measured by real time quantitative PCR using TaqMan probe. RESULTS: Troglitazone down-regulated the surface expression of CD97 in FTC-133 cells and up-regulated (NIS) mRNA in TPC-1, FTC-133 and XTC-1 cells. CONCLUSION: Our investigations documented that troglitazone, a PPARgammaagonist, induced redifferentiation in thyroid cancer cell lines. In patients who have poorly differentiated thyroid cancer unresponsive to traditional treatments, PPARgammaagonists may therefore reintroduce the effectiveness of traditional treatments.

Troglitazone Increases the Susceptibility to TRAIL-Induced Apoptosis in Thyroid Cancer Cell Lines / 대한내분비외과학회지

PURPOSE: Tumor necrosis factor related apoptosis-inducing ligand (TRAIL) induces apoptosis in many human cancer cells but not in normal cells. Thyroid cancer cells, however, appear to be relatively resistant to TRAIL-induced apoptosis. We investigated the effect of troglitazone, a PPARγ agonist, on TRAIL-induced apoptosis in thyroid cancer cells. METHODS: We used 6 thyroid cancer cell lines: TPC-1, FTC- 133, FTC-236, FTC-238, XTC-1, and ARO82-1. We used flow cytometry to detect apoptosis and used MTT assay to measure anti-proliferation effects. ANOVA was used for statistical analysis. RESULTS: TPC-1 cells were the most sensitive to soluble TRAIL. FTC-133 and ARO82-1 were resistant to TRAIL and growth inhibition was less than 20% at concentration of 800 ng/ml of TRAIL. In both TPC-1 (TRAIL-sensitive) and FTC- 133 (TRAIL-resistant) thyroid cancer cell lines, pretreatment with troglitazone enhanced TRAIL-induced cell death significantly. Bcl-family proteins did not seem to be involved in sensitization of TRAIL-induced apoptosis by troglitazone. CONCLUSION: TRAIL in combination with troglitazone induces apoptosis in thyroid cancer cells at suboptimal concentrations that can not be achieved using TRAIL alone.