High Phosphoglycerate Dehydrogenase Expression Induces Stemness and Aggressiveness in Thyroid Cancer.

Background: We examined the changes in glucose metabolites of papillary thyroid cancer (PTC) and identified phosphoglycerate dehydrogenase (PHGDH) as a potential target. The role of PHGDH in the proliferation and tumorigenesis of thyroid cancer cells and its clinical significance were analyzed. Methods: Glucose metabolites of various thyroid tissues were analyzed via targeted metabolomics analysis. In vitro experiments using shPHGDHs, inhibitor (NCT503), or PHGDH overexpression in thyroid cell lines (BCPAP, 8505C, and Nthy-Ori) were performed. In vivo experiments were performed by using shPHGDH. Human tissue samples and The Cancer Genome Atlas (TCGA) data were used to validate the experimental findings. Results:PHGDH knockdown in BCPAP and 8505c cell lines significantly inhibited cell viability, colony formation, and tumor spheroid formation compared with the control. In addition, treatment with NCT503 showed similar results. PHGDH inhibition by both knockdown and treatment with NCT503 significantly inhibited the expression of embryonic cancer stemness markers (Oct4, Sox2, KLF4, and Nanog). PHGDH overexpression in Nthy-Ori cells significantly increased cell viability and colony formation. The stemness markers were significantly increased after PHGDH overexpression. PHGDH knockdown significantly inhibited tumor growth in an in vivo mouse xenograft study using 8505c cells. The protein expression of Oct4 in tumors was significantly reduced after PHGDH knockdown. The associations between PHGDH expression and stemness markers were confirmed in the TCGA data and human thyroid tissue samples. Positive PHGDH protein expression was associated with metastases of PTC. Conclusions:PHGDH expression is induced in thyroid cancer and is associated with stemness and aggressiveness of PTC.

The role of Slit2 as a tumor suppressor in thyroid cancer.

Slits, representative axon guidance molecules, and their Roundabout (Robo) transmembrane receptors play roles in the progression of many cancers. We investigated the effects of Slit2 on the proliferation, migration, and invasion of thyroid cancer cells, and on the prognosis of papillary thyroid cancer (PTC). Slit2 overexpression inhibited the proliferation, migration and invasion of thyroid cancer cells by inhibiting transcriptional activity of beta-catenin and regulating Rho GTPase activity. Slit2 knockdown activated the migration and invasion of thyroid cancer cells and transcriptional activity of beta-catenin. Fragment Slit2 treatment inhibited thyroid cancer cell proliferation in a dose dependent manner, and also inhibited migration and invasion. When we evaluated the protein expression of Slit2 in PTCs, 24 of 160 PTCs (15%) were negative for Slit2 protein expression and these patients had significantly increased risk of cervical lymph node metastasis (P < 0.001), distant metastasis (P < 0.001) and recurrence of PTC (P < 0.001). Our findings suggest a role for Slit2 as a tumor suppressor, and also as a novel prognostic and potential therapeutic target for thyroid cancer.

Association of KCNJ2 Genetic Variants with Susceptibility to Thyrotoxic Periodic Paralysis in Patients with Graves' Disease.

Objective: Thyrotoxic periodic paralysis (TPP) is characterized by acute onset paralysis and hypokalemia predominantly in male patients with thyrotoxicosis. Recent studies have emphasized the importance of potassium channels, which might explain the underlying mechanism of TPP. The KCNJ2 gene encodes the inward-rectifying potassium channel. In this study, we evaluated the role of KCNJ2 in the development of TPP. Design: Case-control analysis of KCNJ2 genetic association with TPP. Patients: 83 male patients with Graves' disease (GD) were recruited for this study; 43 patients had TPP, whereas 40 patients had no history of TPP. Measurements: We analyzed the genotype and allelic frequency of a single-nucleotide polymorphism (SNP; rs312691) (C>T) adjacent to the KCNJ2 gene that is known to be related to TPP development. Results: The frequency of the CC genotype of the rs312691 SNP was 0.51 in TPP patients and 0.05 in controls (p-value=6.18×10-6). The C allele frequency of the SNP was 0.67 in the TPP group and 0.38 in the control group (odds ratio 3.24; 95% confidence interval 1.65-6.51; p-value, 3.1×10-4). The rs312691 SNP was significantly associated with TPP. Conclusions: We demonstrated that the rs312691 SNP was significantly associated with TPP. These findings suggest that KCNJ2 plays an important role in the pathophysiology of TPP in Korean GD patients with TPP.

Low Prevalence of Somatic TERT Promoter Mutations in Classic Papillary Thyroid Carcinoma.

BACKGROUND: Transcriptional activating mutations of telomerase reverse transcriptase (TERT) are associated with more aggressive thyroid cancer. We evaluated the significance of TERT promoter mutations in Korean patients with classic papillary thyroid cancer (PTC). METHODS: Genomic DNA was isolated from four thyroid cancer cell lines and 35 fresh-frozen PTC tissues. TERT promoter mutations (C228T and C250T) and the BRAF V600E mutation were evaluated by polymerase chain reaction amplification and direct sequencing. RESULTS: The CC228229TT mutation in the TERT promoter was detected in BCPAP cells and the C250T mutation was found in 8505C cells. No TERT promoter mutation was observed in Cal-62 or ML-1 cells. The C228T mutation was found in only 1 of 35 (2.8%) PTCs and no C250T mutations were detected in any of the study subjects. The BRAF V600E mutation was found in 20 of 35 (57.1%) PTCs. One patient with the C228T TERT mutation also harbored the BRAF V600E mutation and developed a recurrence. CONCLUSION: The prevalence of somatic TERT promoter mutations was low in Korean patients with classic PTC. Therefore, the prognostic role of TERT promoter mutations might be limited in this patient cohort.

Thyrotoxic Periodic Paralysis and Polymorphisms of the ADRB2, AR, and GABRA3 Genes in Men with Graves Disease.

BACKGROUND: Thyrotoxic periodic paralysis (TPP) is a rare complication of thyrotoxicosis characterized by acute attacks of muscle weakness and hypokalemia. Recently, variation in several genes was suggested to be associated with TPP. This study evaluated the genetic predisposition to TPP in terms of the ß2-adrenergic receptor (ADRB2), androgen receptor (AR), and γ-aminobutyric acid receptor α3 subunit (GABRA3) genes. METHODS: This study enrolled 48 men with Graves disease (GD) and TPP, and 48 GD patients without TPP. We compared the frequencies of candidate polymorphisms between the two groups. RESULTS: The frequency of the Gly16/Gly16 genotype in ADRB2 was not significantly associated with TPP (P=0.32). More CAG repeats (≥26) in the AR gene were not correlated with TPP (odds ratio [OR], 2.46; 95% confidence interval [CI], 0.81 to 8.09; P=0.08). The allele frequency of the TT genotype in the GABRA3 gene was not associated with TPP (OR, 1.83; 95% CI, 0.54 to 6.74; P=0.41). CONCLUSION: The polymorphisms in the ADRB2, AR, and GABRA3 genes could not explain the genetic susceptibility to TPP in Korean men with GD.

Alpha lipoic acid inhibits proliferation and epithelial mesenchymal transition of thyroid cancer cells.

The naturally occurring short-chain fatty acid, α-lipoic acid (ALA) is a powerful antioxidant which is clinically used for treatment of diabetic neuropathy. Recent studies suggested the possibility of ALA as a potential anti-cancer agent, because it could activate adenosine monophosphate activated protein kinase (AMPK) and inhibit transforming growth factor-ß (TGFß) pathway. In this study, we evaluate the effects of ALA on thyroid cancer cell proliferation, migration and invasion. We performed in vitro cell proliferation analysis using BCPAP, HTH-83, CAL-62 and FTC-133 cells. ALA suppressed thyroid cancer cell proliferation through activation of AMPK and subsequent down-regulation of mammalian target of rapamycin (mTOR)-S6 signaling pathway. Low-dose ALA, which had minimal effects on cell proliferation, also decreased cell migration and invasion of BCPAP, CAL-62 and HTH-83 cells. ALA inhibited epithelial mesenchymal transition (EMT) evidently by increase of E-cadherin and decreases of activated ß-catenin, vimentin, snail, and twist in these cells. ALA suppressed TGFß production and inhibited induction of p-Smad2 and twist by TGFß1 or TGFß2. These findings indicate that ALA reduces cancer cell migration and invasion through suppression of TGFß production and inhibition of TGFß signaling pathways in thyroid cancer cells. ALA also significantly suppressed tumor growth in mouse xenograft model using BCPAP and FTC-133 cells. This is the first study to show anti-cancer effect of ALA on thyroid cancer cells. ALA could be a potential therapeutic agent for treatment of advanced thyroid cancer, possibly as an adjuvant therapy with other systemic therapeutic agents.