Cystathionine ß-Synthase Regulates the Proliferation, Migration, and Invasion of Thyroid Carcinoma Cells.

Thyroid cancer is considered to be one of the most common endocrine tumors worldwide. Cystathionine ß-synthase (CBS) plays a crucial role in the occurrence of several types of malignancies. And yet, the mechanism of action of CBS in the growth of thyroid carcinoma cells is still unrevealed. We found that CBS level in thyroid carcinoma tissue was higher than that in adjacent normal tissue. The overexpression of CBS enhanced the proliferation, migration, and invasion of thyroid cancer cells, while the downregulation of CBS exerted reverse effects. CBS overexpression reduced the levels of cleaved caspase-3 and cleaved poly ADP-ribose polymerase in thyroid cancer cells, whereas CBS knockdown showed reverse trends. CBS overexpression decreased reactive oxygen species (ROS) levels but increased the levels of Wnt3a and phosphorylations of phosphatidylinositol 3-kinase (PI3K), protein kinase B (PKB/AKT), mammalian target of rapamycin (mTOR), ß-catenin, and glycogen synthase kinase-3 beta, while CBS knockdown exerted opposite effects. In addition, CBS overexpression promoted the growth of xenografted thyroid carcinoma, whereas CBS knockdown decreased the tumor growth by modulating angiogenesis, cell cycle, and apoptosis. Furthermore, aminooxyacetic acid (an inhibitor of CBS) dose-dependently inhibited thyroid carcinoma cell growth. CBS can regulate the proliferation, migration, and invasion of human thyroid cancer cells via ROS-mediated PI3K/AKT/mTOR and Wnt/ß-catenin pathways. CBS can be a potential biomarker for diagnosing or prognosing thyroid carcinoma. Novel donors that inhibit the expression of CBS can be developed in the treatment of thyroid carcinoma.

Thyroid Follicular Cell-derived Carcinomas in a Background of Multiple Adenomatous Nodules Leading to a Diagnosis of PTEN Hamartoma Tumor Syndrome in an Adult Patient With a Novel RECQL4 Mutation.

BACKGROUND: Phosphatase and tensin homolog (PTEN) hamartoma tumor syndrome (PHTS) is a complex disorder. Carriers develop hamartomatous tumors, with an increased risk for developing malignant tumors in multiple organs. Surveillance to facilitate the early detection and treatment of malignancies is extremely important. CASE REPORT: A 31-year-old male presented with a 10 cm left lobe thyroid gland mass. After fine needle aspiration a left hemithyroidectomy was performed, which demonstrated a minimally invasive follicular thyroid carcinoma (FTC, stage pT3a) and microscopic classical papillary thyroid carcinoma (PTC) in the background of about 50 separate adenomatous nodules (0.2-5 mm). Immunostaining showed loss of PTEN protein in the minimally invasive FTC and in all of the nodules tested, with uninvolved parenchyma serving as an internal control. Kaiser Permanente Northern California (KPNC) Hereditary Cancer Panel, testing for 62 genes, was performed and showed germline mutations in PTEN and RecQ like helicase 4 (RECQL4) genes. Completion thyroidectomy subsequently performed demonstrated about 60 follicular cell-derived adenomatous nodules (0.3-10 mm). Genetic counseling and evaluation documented Cowden syndrome (CS) in the family. Thus, PHTS was confirmed. CONCLUSION: This report documents synchronous FTC and PTC in a background of multiple follicular adenomatous nodules with a novel RECQL4 mutation in an adult patient with PHTS. As such, documented the loss of PTEN protein in a thyroid gland affected by multiple adenomatous nodules aided in diagnosing PHTS.

New Indication for Cabozantinib.

Cabozantinib (Cabometyx) is now approved to treat locally advanced or metastatic differentiated thyroid cancer that has progressed following prior vascular endothelial growth factor receptor-targeted therapy.

High Expression of PDE8B and DUOX2 Associated with Ability of Metastasis in Thyroid Carcinoma.

BACKGROUND: Hormone is an independent factor that induces differentiation of thyroid cancer (TC) cells. The thyroid-stimulating hormone (TSH) could promote the progression and invasion in TC cells. However, few genes related to hormone changes are studied in poorly differentiated metastatic TC. This study is aimed at constructing a gene set's coexpression correlation network and verifying the changes of some hub genes involved in regulating hormone levels. METHODS: Microarray datasets of TC samples were obtained from public Gene Expression Omnibus (GEO) databases. R software and bioinformatics packages were utilized to identify the differentially expressed genes (DEGs), important gene module eigengenes, and hub genes. Subsequently, the Gene Ontology (GO) enrichment analysis was constructed to explore important biological processes that are associated with the mechanism of poorly differentiated TC. Finally, some hub gene expressions were validated through real-time PCR and immunoblotting. RESULTS: Gene chip with category number GSE76039 was analyzed, and 1190 DEGs were screened with criteria of P < 0.05 and ∣log2foldchange | >2. Our analysis showed that human dual oxidase 2 (DUOX2) and phosphodiesterase 8B (PDE8B) are the two important hub genes in a coexpression network. In addition, the validated experimental results showed that the expression levels of both DUOX2 and PDE8B were elevated in poorly differentiated metastatic TC tissues. CONCLUSION: This study identified and validated that DUOX2 and PDE8B were significantly associated with the metastasis ability of thyroid carcinoma.

Novel Inhibitor-Based Therapies for Thyroid Cancer-An Update.

Thyroid cancers (TCs) are the most common tumors of the endocrine system and a constant rise in the number of TC cases has been observed for the past few decades. TCs are one of the most frequent tumors in younger adults, especially in women, therefore early diagnosis and effective therapy are especially important. Ultrasonography examination followed by fine needle biopsy have become the gold standard for diagnosis of TCs, as these strategies allow for early-stage detection and aid accurate qualification for further procedures, including surgical treatment. Despite all the advancements in detection and treatment of TCs, constant mortality levels are still observed. Therefore, a novel generation line of targeted treatment strategies is being developed, including personalized therapies with kinase inhibitors. Recent molecular studies on TCs demonstrate that kinase inhibitor-based therapies might be considered as the most promising. In the past decade, new kinase inhibitors with different mechanisms of action have been reported and approved for clinical trials. This review presents an up-to-date picture of new approaches and challenges of inhibitor-based therapies in treatment of TCs, focusing on the latest findings reported over the past two years.

Death-Associated Protein Kinase 1 Inhibits Progression of Thyroid Cancer by Regulating Stem Cell Markers.

The activation of metastatic reprogramming is vital for cancer metastasis, but little is known about its mechanism. This study investigated the potential role of death-associated protein kinase 1 (DAPK1) in thyroid cancer progression. We generated knockdown (KD) DAPK1 using siRNA or shRNA in 8505C and KTC-1 cell lines, which we transiently or stably overexpressed in MDA-T32 and BCPAP cell lines. DAPK1 KD in 8505C and KTC-1 cells significantly increased cell proliferation and colony formation compared with controls. We observed significant inhibition of cancer cell invasion in cells overexpressing DAPK1, but the opposite effect in KD cells. Tumorsphere formation significantly increased after inhibition of DAPK1 expression in 8505C cells and was significantly suppressed in DAPK1-overexpressing MDA-T32 and BCPAP cells. DAPK1 overexpression inhibited mRNA and protein levels of stem markers (OCT4, Sox2, KLF4, and Nanog). Furthermore, the expression of these markers increased after KD of DAPK1 in 8505C cells. Mechanistic studies suggest that DAPK1 may modulate the expression of stem cell markers through the inhibition of ß-catenin pathways. These findings were consistent with the public data and our thyroid tissue analysis, which showed higher DAPK1 expression was associated with advanced-stage papillary thyroid cancer with a higher stemness index and lower disease-free survival.

CircRNA NRIP1 promotes papillary thyroid carcinoma progression by sponging mir-195-5p and modulating the P38 MAPK and JAK/STAT pathways.

BACKGROUND: Circular RNAs (circRNAs) have become a hot topic in the area of tumor biology due to its closed structure and the post-transcriptional regulatory effect. This study aims to clarify the roles of circRNA nuclear receptor-interacting protein 1 (NRIP1; circNRIP1) and the possible mechanisms in papillary thyroid carcinoma (PTC). METHODS: The real-time PCR was used to detect the expression level of CircRNA NRIP1 in PTC specimens and cell lines. The effects of CircRNA NRIP1 and miR-195-5p on the PTC cell functions were detected by MTT, transwell, and flow cytometry assays. Dual-luciferase reporter assays and pull down assays were used to verify the association between circRNA NRIP1 and miR-195-5p. The murine xenograft models were constructed to detect the roles of CircRNA NRIP1 and miR-195-5p. Western blot was applied to detect the effects of CircRNA NRIP1 and miR-195-5p on the P38 MAPK and JAK/STAT singling pathways. RESULTS: CircRNA NRIP1 was over-expressed in PTC tissues and cells and the high levels of CircRNA NRIP1 were correlated with advanced PTC stage. Depletion of CircRNA NRIP1 inhibited PTC cell proliferation, invasion, while accelerated apoptosis. miR-195-5p upregulation repressed proliferation and invasion capabilities, and accelerated apoptosis of PTC cell lines and restraining the growth of tumor xenografts, while the functions were reversed following CircRNA NRIP1 overexpression in PTC cells and tumor xenografts. Besides, the protein levels of p-p38, p-JAK2 and p-STAT1 were remarkably down-regulated in miR-195-5p overexpressed PTC cells and tumor xenografts, whereas CircRNA NRIP1 up-regulation overturned the impacts. CONCLUSIONS: In conclusion, CircRNA NRIP1 promoted PTC progression by accelerating PTC cells proliferation, invasion and tumor growth, while impeding apoptosis by way of sponging miR-195-5p and regulating the P38 MAPK and JAK/STAT pathways.

Increased diagnostic sensitivity of palpation-guided thyroid nodule fine-needle aspiration cytology by BRAF V600E-mutation analysis.

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer and its incidence is increasing. Preoperative diagnosis is warranted in order to avoid 'two-stage' procedures that are associated with additional costs and higher radioactive iodine remnant uptake. In the setting of thyroid cancer, somatic BRAF V600E-mutations are highly specific for PTC and can be analyzed in aspirates from fine-needle aspiration cytology (FNAC). The 'gold standard' to perform FNAC is ultrasound guidance. Here, we analyze whether adding BRAF V600E-mutation analysis could be of value in palpation-guided FNACs. A total of 430 consecutive patients were included. Ultrasound-guided FNACs were performed in 251 patients and 179 patients underwent palpation-guided FNACs. BRAF V600E-mutation analysis was performed using two methods, an allele-specific polymerase chain reaction (PCR) analyzed by capillary gel electrophoresis (PCR/Qiaxcel), and a droplet digital PCR (ddPCR) assay. A total of 80 patients underwent surgery, and histology revealed 25 patients to have PTC. Of the 25 PTCs, 23 (92%) showed a BRAF V600E-mutation. Both mutation analysis methods (PCR/Qiaxcel and ddPCR) produced concordant results. In the ultrasound-guided group, the preoperative diagnostic sensitivity of FNAC using the Bethesda classification alone was very high and additional BRAF V600E-mutation analysis added little to the preoperative diagnostic sensitivity. By contrast, in the palpation-guided group, by adding BRAF V600E-mutation analysis, eight instead of four patients were diagnosed of having PTC. This increase in the diagnostic sensitivity was statistically significant (p < 0.05). The costs per sample were as low as 62 USD (PCR/Qiaxcel and ddPCR) and 35 USD (PCR/Qiaxcel only). Ultrasound-guided FNAC should be aimed for when dealing with thyroid nodules. However, if palpation-guided FNAC cannot be avoided or may be required due to resource utilization, adding BRAF V600E-mutation analysis using the methods described in this study might significantly increase the proportion of preoperatively diagnosed PTCs. The additional costs can be considered very reasonable.

CD73 expression in normal, hyperplastic, and neoplastic thyroid: a systematic evaluation revealing CD73 overexpression as a feature of papillary carcinomas.

CD73 converts AMP to adenosine, an immunosuppressive metabolite that promotes tumorigenesis. This study presents a systematic evaluation of CD73 expression in benign, hyperplastic, and neoplastic thyroid. CD73 expression was assessed by immunohistochemistry in 142 thyroid samples. CD73 was expressed in normal thyroid (3/6) and goiter (5/6), with an apical pattern and mild intensity. Apical and mild CD73 expression was also present in oncocytic cell adenomas/carcinomas (9/10; 5/8) and in follicular adenomas/carcinomas (12/18; 23/27). In contrast, papillary thyroid carcinomas featured extensive and intense CD73 staining (49/50) (vs. normal thyroid/goiter, p < 0.001). Seven of nine anaplastic carcinomas were CD73-positive with heterogeneous extensiveness of staining. Medullary and poorly differentiated carcinomas were mostly CD73-negative (1/6; 2/2). These results were corroborated by NT5E mRNA profiling. Papillary carcinomas feature enhanced CD73 protein and mRNA expression with distinct and intense staining, more pronounced in the invasive fronts of the tumors.

Questions and Controversies in the Clinical Application of Tyrosine Kinase Inhibitors to Treat Patients with Radioiodine-Refractory Differentiated Thyroid Carcinoma: Expert Perspectives.

Notwithstanding regulatory approval of lenvatinib and sorafenib to treat radioiodine-refractory differentiated thyroid carcinoma (RAI-R DTC), important questions and controversies persist regarding this use of these tyrosine kinase inhibitors (TKIs). RAI-R DTC experts from German tertiary referral centers convened to identify and explore such issues; this paper summarizes their discussions. One challenge is determining when to start TKI therapy. Decision-making should be shared between patients and multidisciplinary caregivers, and should consider tumor size/burden, growth rate, and site(s), the key drivers of RAI-R DTC morbidity and mortality, along with current and projected tumor-related symptomatology, co-morbidities, and performance status. Another question involves choice of first-line TKIs. Currently, lenvatinib is generally preferred, due to greater increase in progression-free survival versus placebo treatment and higher response rate in its pivotal trial versus that of sorafenib; additionally, in those studies, lenvatinib but not sorafenib showed overall survival benefit in subgroup analysis. Whether recommended maximum or lower TKI starting doses better balance anti-tumor effects versus tolerability is also unresolved. Exploratory analyses of lenvatinib pivotal study data suggest dose-response effects, possibly favoring higher dosing; however, results are awaited of a prospective comparison of lenvatinib starting regimens. Some controversy surrounds determination of net therapeutic benefit, the key criterion for continuing TKI therapy: if tolerability is acceptable, overall disease control may justify further treatment despite limited but manageable progression. Future research should assess potential guideposts for starting TKIs; fine-tune dosing strategies and further characterize antitumor efficacy; and evaluate interventions to prevent and/or treat TKI toxicity, particularly palmar-plantar erythrodysesthesia and fatigue.

Multikinase inhibitors in thyroid cancer: timing of targeted therapy.

In the 9 years since the publication of our 2011 review of targeted treatment of thyroid cancer with multikinase inhibitors, much has changed in the landscape of this heterogeneous disease. New multikinase and selective inhibitor treatments for medullary thyroid cancer, radioiodine-refractory thyroid cancer and anaplastic thyroid cancer have completed trials and improved progression-free survival. Many physicians are concerned by dose-limiting adverse effects of these drugs and are wary to begin treatment in patients who are systemically well but have marked disease burden, which makes the timing of treatment initiation challenging. Published mechanistic data on tyrosine kinase inhibitors (TKIs) have helped guide our understanding of how to dose effectively with these drugs. A major goal in TKI therapy is to optimize inhibition of oncogenic kinase drivers while maintaining patient quality of life. Real-world data have now been published on how TKIs have fared outside the clinical trial environment. In this Review, we provide a summary of published data on the efficacy of TKIs in clinical practice, to provide clinicians with a more realistic view of how their patients will manage and respond to TKI therapy. Furthermore, we review the data on mechanisms of inhibition, outcomes and adverse effects of TKIs and provide an update on targeted treatment of thyroid cancer, focusing on optimizing the timing of treatment initiation.

Fine-Tuning Lipid Metabolism by Targeting Mitochondria-Associated Acetyl-CoA-Carboxylase 2 in BRAFV600E Papillary Thyroid Carcinoma.

Background: BRAFV600E acts as an ATP-dependent cytosolic kinase. BRAFV600E inhibitors are widely available, but resistance to them is widely reported in the clinic. Lipid metabolism (fatty acids) is fundamental for energy and to control cell stress. Whether and how BRAFV600E impacts lipid metabolism regulation in papillary thyroid carcinoma (PTC) is still unknown. Acetyl-CoA carboxylase (ACC) is a rate-limiting enzyme for de novo lipid synthesis and inhibition of fatty acid oxidation (FAO). ACC1 and ACC2 genes encode distinct isoforms of ACC. The aim of our study was to determine the relationship between BRAFV600E and ACC in PTC. Methods: We performed RNA-seq and DNA copy number analyses in PTC and normal thyroid (NT) in The Cancer Genome Atlas samples. Validations were performed by using assays on PTC-derived cell lines of differing BRAF status and a xenograft mouse model derived from a heterozygous BRAFWT/V600E PTC-derived cell line with knockdown (sh) of ACC1 or ACC2. Results:ACC2 mRNA expression was significantly downregulated in BRAFV600E-PTC vs. BRAFWT-PTC or NT clinical samples. ACC2 protein levels were downregulated in BRAFV600E-PTC cell lines vs. the BRAFWT/WT PTC cell line. Vemurafenib increased ACC2 (and to a lesser extent ACC1) mRNA levels in PTC-derived cell lines in a BRAFV600E allelic dose-dependent manner. BRAFV600E inhibition increased de novo lipid synthesis rates, and decreased FAO due to oxygen consumption rate (OCR), and extracellular acidification rate (ECAR), after addition of palmitate. Only shACC2 significantly increased OCR rates due to FAO, while it decreased ECAR in BRAFV600E PTC-derived cells vs. controls. BRAFV600E inhibition synergized with shACC2 to increase intracellular reactive oxygen species production, leading to increased cell proliferation and, ultimately, vemurafenib resistance. Mice implanted with a BRAFWT/V600E PTC-derived cell line with shACC2 showed significantly increased tumor growth after vemurafenib treatment, while vehicle-treated controls, or shGFP control cells treated with vemurafenib showed stable tumor growth. Conclusions: These findings suggest a potential link between BRAFV600E and lipid metabolism regulation in PTC. BRAFV600E downregulates ACC2 levels, which deregulates de novo lipid synthesis, FAO due to OCR, and ECAR rates. ShACC2 may contribute to vemurafenib resistance and increased tumor growth. ACC2 rescue may represent a novel molecular strategy for overcoming resistance to BRAFV600E inhibitors in refractory PTC.

HIF-1α-Mediated Telomerase Reverse Transcriptase Activation Inducing Autophagy Through Mammalian Target of Rapamycin Promotes Papillary Thyroid Carcinoma Progression During Hypoxia Stress.

Background: It is important to properly understand the molecular mechanisms of aggressive tumors among papillary thyroid carcinomas (PTCs) that are often the most indolent. Hypoxia inducible factor-1α (HIF-1α), induced by hypoxia, plays pivotal roles in the development and metastasis of the many tumors, including PTCs. Upregulation of telomerase reverse transcriptase (TERT) activity is found in highly invasive PTCs. Further, previous studies have reported that autophagy serves as a protective mechanism to facilitate PTC cell survival. We, therefore, hypothesized that there was a link between HIF-1α, TERT, and autophagy in promoting PTC progression. Methods: Immunohistochemistry staining was conducted to evaluate the expressions of HIF-1α, TERT, and autophagy marker, LC3-II, in matched PTC tumors and corresponding nontumor tissues. Two PTC cell lines (TPC-1 and BCPAP) were used in subsequent cytological function studies. Cell viability, proliferation, apoptosis, migration, and invasion were assessed during hypoxia, genetic enhancement and inhibition of TERT, and chemical and genetic inhibition of autophagy. The protein expression levels of the corresponding biomarkers were determined by Western blotting, and autophagy flow was detected. We characterized the molecular mechanism of PTC cell progression. Results: The protein expression levels of HIF-1α, TERT, and LC3-II were upregulated in PTCs and were significantly correlated with high tumor-node-metastasis stage. Further, an in vitro study indicated that HIF-1α induced by hypoxia functioned as a transcriptional activator by binding with sequences potentially located in the TERT promoter and was positively correlated with the malignant behavior of PTC cell lines. Overexpression of TERT inhibited the kinase activity of mammalian target of rapamycin (mTOR), resulting in the activation of autophagy. Functionally, TERT-induced autophagy provided a survival advantage to PTC cells during hypoxia stress. Conclusions: We identified a novel molecular mechanism involving the HIF-1α/TERT axis, which promoted PTC progression by inducing autophagy through mTOR during hypoxia stress. These findings may provide a basis for the new treatment of aggressive PTCs.

Serine 897 Phosphorylation of EPHA2 Is Involved in Signaling of Oncogenic ERK1/2 Drivers in Thyroid Cancer Cells.

Background: Phosphorylation of the intracellular domain of the EPHA2 receptor tyrosine kinase (RTK) on serine 897 (S897) has been demonstrated to mediate EPHA2 oncogenic activity. Here, we show that in thyroid cancer cells harboring driver oncogenes that signal through the extracellular regulated kinase (ERK1/2) signaling pathway [rearranged RET RTK (RET/PTC), KRAS(G12R), or BRAFV600E oncogenes], EPHA2 is robustly phosphorylated on S897. EPHA2 S897 is embedded in a consensus sequence for phosphorylation by the AGC family kinases, including p90RSK (ribosomal protein S6 kinase), a direct ERK1/2 target. Methods: We show that recombinant p90RSK phosphorylates in vitro EPHA2 S897 and that treatment with chemical inhibitors targeting p90RSK or other components of the ERK1/2 pathway blunts S897 phosphorylation. Results: RNA interference-mediated knockdown combined with rescue experiments demonstrated that EPHA2 S897 phosphorylation mediates thyroid cancer cell proliferation and motility. Conclusions: These findings point to EPHA2 S897 as a crucial mediator of the oncogenic activity of the ERK1/2 signaling cascade in thyroid cancer.

Prognostic Significance of COX-2 Overexpression in BRAF-Mutated Middle Eastern Papillary Thyroid Carcinoma.

The cyclooxygenase-2 (COX-2)-prostaglandin E2 (PGE2) pathway has been implicated in carcinogenesis, with BRAF mutation shown to promote PGE2 synthesis. This study was conducted to evaluate COX-2 expression in a large cohort of Middle Eastern papillary thyroid carcinoma (PTC), and further evaluate the prognostic significance of COX-2 expression in strata of BRAF mutation status. BRAF mutation analysis was performed using Sanger sequencing, and COX-2 expression was evaluated immunohistochemically using tissue microarray (TMA). COX-2 overexpression, noted in 43.2% (567/1314) of cases, was significantly associated with poor prognostic markers such as extra-thyroidal extension, lymph-node metastasis, and higher tumor stage. COX-2 was also an independent predictor of poor disease-free survival (DFS). Most notably, the association of COX-2 expression with DFS differed by BRAF mutation status. COX-2 overexpression was associated with poor DFS in BRAF-mutant but not BRAF wild-type PTCs, with a multivariate-adjusted hazard ratio of 2.10 (95% CI = 1.52-2.92; p < 0.0001) for COX-2 overexpressed tumors in BRAF-mutant PTC. In conclusion, the current study shows that COX-2 plays a key role in prognosis of PTC patients, especially in BRAF-mutated tumors. Our data suggest the potential therapeutic role of COX-2 inhibition in patients with BRAF-mutated PTC.

The impact of NOS3 gene polymorphism on papillary thyroid cancer susceptibility in patients undergoing radioiodine therapy.

Thyroid cancer is the most common endocrine cancer in the world. Noting that the NOS3 gene polymorphism interferes with nitric oxide production, this study aims to identify and analyze the NOS3 gene polymorphism in the intron 4 region in patients with papillary thyroid cancer. A case-control study was conducted with 31 papillary thyroid cancer patients of both genders who underwent thyroidectomy and treatment with sodium iodide radiopharmaceutical (131I) compared with 81 control patients. Through papillary thyroid cancer, the results were observed, compiled, and analyzed using SPSS version 25.0. The significance level of 5% was adopted. Genotypic frequencies of healthy subjects were in the Hardy-Weinberg equilibrium (P = 0.503). There was a significant genotypic difference between papillary thyroid cancer and healthy individuals (P <0.001). The BB genotype conferred a protective factor for papillary thyroid cancer (P <0.001, odds ratio (OR) 0.16; 95% confidence interval (CI) 0.06, 0.42), while the presence of the A allele appears to be a risk factor for papillary thyroid cancer (P <0.001, OR 3.54; 95% CI 1.86, 6.73). The intron 4 polymorphism of the NOS3 gene was associated with susceptibility to papillary thyroid cancer. Thus, future research into the effects of this polymorphism is essential.

Heat Shock Protein 90 Inhibitors AUY922, BIIB021 and SNX5422 Induce Bim-mediated Death of Thyroid Carcinoma Cells.

BACKGROUND/AIM: Heat shock protein 90 (HSP90) controls maturation of oncogenic client proteins of cancer cells, and thus we studied the effect of HSP 90 inhibitors on cell survival and survival-related mediators in thyroid carcinoma cells. MATERIALS AND METHODS: Human TPC-1 and SW1736 thyroid carcinoma cells were utilized. Cell viability, cytotoxic activity and apoptosis were estimated using CCK-8 assay, cytotoxicity assay and FACS analysis, respectively. RESULTS: AUY922, BIIB021 and SNX5422 decreased cell viability, and increased cytotoxic activity and the proportion of apoptotic cells. The protein levels of cleaved PARP, cleaved caspase-3, Bax and Bim were elevated, and Bcl2 protein levels were reduced. Knockdown of Bax did not change cell viability, cytotoxic activity, the proportion of apoptotic cells and cleaved caspase-3 protein levels. Meanwhile, knockdown of Bim enhanced cell viability, and diminished cytotoxic activity, the proportion of apoptotic cells and cleaved caspase-3 protein levels. AUY922, BIIB021 and SNX5422 increased the protein levels of phospho-AMPK, and decreased those of phospho-ERK1/2, and total and phospho-AKT. CONCLUSION: AUY922, BIIB021 and SNX5422 induce cytotoxicity by modulating Bim and ERK1/2, AKT and AMPK signaling in thyroid carcinoma cells.

Long non-coding RNA DLEUI promotes papillary thyroid carcinoma progression by sponging miR-421 and increasing ROCK1 expression.

We investigated the role of long non-coding RNA DLEU1 (deleted in lymphocytic leukemia 1) in the progression of papillary thyroid carcinoma (PTC). DLEU1 levels were higher in PTC cell lines (BHP5-16, TPC-1,8505C, and SW1736) and patient tissues (n=54) than in a human thyroid follicular epithelial cell line (Nthy-ori3-1) or adjacent normal thyroid tissues. High DLEU1 expression correlated positively with lymph node metastasis and advanced clinical stages in PTC patients. Bioinformatics, dual luciferase reporter, and RNA pulldown assays confirmed that DLEU1 directly binds to miR-421. Moreover, bioinformatics and dual luciferase reporter assays showed that miR-421 directly binds to the 3'untranslated region of the rho-related coiled-coil kinase 1 (ROCK1) in TPC-1 cells. PTC patient tissues and cell lines showed high ROCK1 mRNA and protein levels as well as low miR-421 levels. CCK-8, flow cytometry, wound healing, and Transwell invasion assays demonstrated that DLEU1 silencing decreases TPC-1 cell proliferation, survival and progression, but they can be rescued by miR-421 knockdown or ROCK1 overexpression. DLEU1 knockdown in TPC-1 cells decreased in vivo xenograft tumor size and weight compared to controls in nude mice. These findings demonstrate that DLEU1 promotes PTC progression by sponging miR-421 and increasing ROCK1 expression.

Telomerase Reverse Transcriptase (TERT) Regulation in Thyroid Cancer: A Review.

Telomerase reverse transcriptase (TERT) is the catalytic subunit of the enzyme telomerase and is essential for telomerase activity. Upregulation of TERT expression and resulting telomerase activity occurs in the large majority of malignancies, including thyroid cancer. This upregulation results in continued cellular proliferation and avoidance of cellular senescence and cell death. In this review we will briefly introduce TERT and telomerase activity as it pertains to thyroid cancer and, highlight the effects of TERT on cancer cells. We will also explore in detail the different TERT regulatory strategies and how TERT is reactivated in thyroid cancer cells, specifically. These regulatory mechanisms include both activating single base pair TERT promoter mutations and epigenetic changes at the promoter, including changes in CpG methylation and histone modifications that affect chromatin structure. Further, regulation includes the allele-specific regulation of the TERT promoter in thyroid cancer cells harboring the TERT promoter mutation. These entail allele-specific transcriptional activator binding, DNA methylation, histone modifications, and mono-allelic expression of TERT. Lastly, TERT copy number alterations and alternative splicing are also implicated. Both amplifications of the TERT locus and increased full-length transcripts and decreased inactive and dominant negative isoforms result in active telomerase. Finally, the clinical significance of TERT in thyroid cancer is also reviewed.