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 β-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.

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

Background: BRAF^V600E acts as an ATP-dependent cytosolic kinase. BRAF^V600E 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 BRAF^V600E 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 BRAF^V600E 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 BRAF^WT/V600E PTC-derived cell line with knockdown (sh) of ACC1 or ACC2. Results:ACC2 mRNA expression was significantly downregulated in BRAF^V600E-PTC vs. BRAF^WT-PTC or NT clinical samples. ACC2 protein levels were downregulated in BRAF^V600E-PTC cell lines vs. the BRAF^WT/WT PTC cell line. Vemurafenib increased ACC2 (and to a lesser extent ACC1) mRNA levels in PTC-derived cell lines in a BRAF^V600E allelic dose-dependent manner. BRAF^V600E 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 BRAF^V600E PTC-derived cells vs. controls. BRAF^V600E inhibition synergized with shACC2 to increase intracellular reactive oxygen species production, leading to increased cell proliferation and, ultimately, vemurafenib resistance. Mice implanted with a BRAF^WT/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 BRAF^V600E and lipid metabolism regulation in PTC. BRAF^V600E 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 BRAF^V600E inhibitors in refractory PTC.

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.

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.

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.

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.

Long noncoding RNA LINC00520 accelerates progression of papillary thyroid carcinoma by serving as a competing endogenous RNA of microRNA-577 to increase Sphk2 expression

The long noncoding RNA (lncRNA) LINC00520 is an important modulator of the oncogenicity of multiple human cancers. However, whether LINC00520 is involved in the malignancy of papillary thyroid carcinoma (PTC) has not been extensively studied until recently. Therefore, the present study aimed to detect LINC00520 expression and evaluate its clinical significance in PTC. Functional experiments were conducted to test the biological role(s) and underlying mechanisms of LINC00520 in PTC progression. Reverse transcription quantitative polymerase chain reaction was performed to detect LINC00520 expression in PTC. A series of functional experiments, including Cell Counting Kit-8 assay, flow cytometry, Transwell migration assay, and tumor xenograft assay, was employed to investigate the biological roles of LINC00520 in PTC cells. High LINC00520 expression was verified in PTC tissues and cell lines, and this high expression was associated with the unfavorable clinicopathological parameters and short overall survival of patients. Functionally, LINC00520 interference resulted in a significant decrease in PTC cell proliferation, migration, and in vitro invasion and an increase in cell apoptosis. Further, its downregulation impaired tumor growth in vivo. Mechanistically, LINC00520 functioned as a competing endogenous RNA by sponging microRNA-577 (miR-577) and thereby increasing sphingosine kinase 2 (Sphk2) expression. Rescue experiments revealed that inhibiting miR-577 or restoring Sphk2 could abrogate the effects of LINC00520 silencing on the malignant phenotypes of PTC. LINC00520 functioned as an oncogenic lncRNA in PTC, and it facilitated PTC progression by regulating the miR-577/Sphk2 axis, suggesting that the LINC00520/miR-577/Sphk2 axis is an effective target in anticancer management.

Human telomerase reverse transcriptase in papillary thyroid cancer: gene expression, effects of silencing and regulation by BET inhibitors in thyroid cancer cells

PURPOSE

Mutations in TERT promoter have been detected in the more aggressive papillary thyroid cancers (PTCs). To elucidate the role of TERT as an eligible molecular target in these tumors, the expression of hTERT was analyzed in a series of PTCs and the effects of both pharmacological and RNA-interference-induced hTERT silencing were investigated in two human PTC cell lines (K1 and BCPAP).

METHODS

The expression levels of hTERT mRNA and protein were evaluated by real-time PCR and western blot assays, respectively. Effects of hTERT silencing on PTC cell lines were analyzed by MTT, migration and western blot assays. Pharmacological inhibition of hTERT was performed using two bromodomain and extra-terminal (BET) inhibitors, JQ1 and I-BET762.

RESULTS

hTERT expression results increased in 20 out of 48 PTCs, including tumors either positive or negative for the presence of hTERT promoter and/or BRAF mutations. In K1 and BCPAP cells, hTERT silencing determined a reduction in cell viability (~50% for K1 and ~70%, for BCPAP, vs control) and migration properties that were associated with a decrease of AKT phosphorylation and β-Catenin expression. Moreover, hTERT mRNA levels were down-regulated by two BET inhibitors, JQ1 and I-BET762, which at the same dosage (0.5 and 5 µM) reduced the growth of these thyroid cancer cells.

CONCLUSIONS

These findings demonstrate that hTERT may represent an excellent therapeutic target in subgroups of aggressive PTCs.

Activity of ecto-5'-nucleotidase (NT5E/CD73) is increased in papillary thyroid carcinoma and its expression is associated with metastatic lymph nodes

The incidence of papillary thyroid carcinoma (PTC) has been increasing, which raised the interest in its molecular pathways. Although the high expression of ecto-5'-nucleotidase (NT5E) gene expression and NT5E enzymatic activity in several types of cancer is associated with tumor progression, its role in PTC remains unknown. Here, we investigated the AMP hydrolysis in human normal thyroid cells and PTC cells, in primary culture, and the association of NT5E expression with clinical aspects of PTC patients. AMPase activity was higher in thyroid cells isolated from PTC, as compared to normal thyroid (P = 0.0063). Significant correlation was observed between AMPase activity and NT5E levels in primary thyroid cell cultures (r = 0.655, P = 0.029). NT5E expression was higher in PTC than in the adjacent non-malignant thyroid tissue (P = 0.0065) and were positively associated with metastatic lymph nodes (P = 0.0007), risk of recurrence (P = 0.0033), tumor size (P = 0.049), and nodular hyperplasia in the adjacent thyroid parenchyma, when compared to normal thyroid or lymphocytic thyroiditis (P = 0.0146). After adjusting for potential confounders, the malignant/non-malignant paired expression ratio of NT5E mRNA was independently associated with metastatic lymph nodes (P = 0.0005), and tumor size (P=0.0005). In addition, the analysis of PTC described in the TCGA database also showed an association between higher expression of NT5E and metastatic lymph nodes, and tumor microinvasion. These results support the hypothesis that NT5E have a role in PTC microenvironment and might be a potential target for PTC therapy.

Familial Cancer Variant Prioritization Pipeline version 2 (FCVPPv2) applied to a papillary thyroid cancer family

Whole-genome sequencing methods in familial cancer are useful to unravel rare clinically important cancer predisposing variants. Here, we present improvements in our pedigree-based familial cancer variant prioritization pipeline referred as FCVPPv2, including 12 tools for evaluating deleteriousness and 5 intolerance scores for missense variants. This pipeline is also capable of assessing non-coding regions by combining FANTOM5 data with sets of tools like Bedtools, ChromHMM, Miranda, SNPnexus and Targetscan. We tested this pipeline in a family with history of a papillary thyroid cancer. Only one variant causing an amino acid change G573R (dbSNP ID rs145736623, NM_019609.4:exon11:c.G1717A:p.G573R) in the carboxypeptidase gene CPXM1 survived our pipeline. This variant is located in a highly conserved region across vertebrates in the peptidase_M14 domain (Pfam ID PF00246). The CPXM1 gene may be involved in adipogenesis and extracellular matrix remodelling and it has been suggested to be a tumour suppressor in breast cancer. However, the presence of the variant in the ExAC database suggests it to be a rare polymorphism or a low-penetrance risk allele. Overall, our pipeline is a comprehensive approach for prediction of predisposing variants for high-risk cancer families, for which a functional characterization is a crucial step to confirm their role in cancer predisposition.

Expression of human telomerase reverse transcriptase (hTERT) in thyroid neoplasms

PURPOSE

Distinction of thyroid neoplasms that include papillary carcinoma (PC) and follicular carcinoma (FC) from benign thyroid neoplasms can be performed successfully by histopathologic examination in most of the cases. However, in some cases it may be difficult to distinct PC and FC as well as FC and follicular adenoma (FA) and also FA and the dominant nodule of multinodular goiter (MNG) histopathologically. In this study, we aimed to determine the role of expression of the human telomerase reverse transcriptase (hTERT) in the distinction of thyroid neoplasms and its relation with prognostic factors by immunohistochemical methods.

METHODS

This retrospective study included 138 cases histopathologically diagnosed with benign and malignant thyroid neoplasia. Sections obtained from formalin-fixed paraffin- embedded blocks were stained with hTERT antibody. Cases were divided into hTERT-positive and -negative categories according to hTERT expression score that included percentage and intensity of staining in neoplastic cells.

RESULTS

hTERT expression was negative in 93 (67.4%) and positive in 45 (32.6%) patients. Twenty-three (46.0%) of 50 PC, 12 (36.0%) of 33 FA, 1 (10.0%) of 10 FC, 4 (13.0%) of 31 MNG, 2 (66.0%) of 3 medullary carcinoma (MC) patients were found hTERT (+), showing that the difference between PC and FC was significant (p=0.034). There was also a significant difference between FA and MNG (p=0.030). There was no difference between FA and FC (p=0.117).

CONCLUSION

The high expression of hTERT can be useful for making a differential diagnosis between PC and FC, and between FA and MNG when histopathological findings are equivocal.

Angiogenic and lymphangiogenic profiles in histological variants of papillary thyroid carcinoma

INTRODUCTION

Papillary thyroid carcinoma (PTC) is a well‑differentiated tumor that occurs in several histological variants whose biological behaviors remain unclear. Angiogenesis and lymphangiogenesis are critical processes that enable tumor progression.

OBJECTIVES

The aim of this study was to evaluate the angiogenic and lymphangiogenic phenotypes of PTC, considering the differences between histological variants.

PATIENTS AND METHODS

Angiogenic and lymphangiogenic profiles were analyzed by determining microvascular density (MVD) and lymphatic vessel density (LVD) in 73 cases of PTC, using immunohistochemistry. To assess the biological markers involved in blood and lymph vessel formation, the expression of vascular endothelial growth factor (VEGF), cyclooxygenase 2 (COX‑2), and p27kip1 (p27) was determined.

RESULTS

MVD was significantly higher in patients with high‑risk PTC and in those with local extrathyroidal and vascular invasion. Positive VEGF expression was strongly associated with high MVD and age‑related tumor enlargement. The presence of lymph vessel invasion was associated with the expression of either VEGF or COX‑2. The analysis of angiogenesis and lymphangiogenesis in different histological variants of PTC revealed elevated LVD rather than MVD in the follicular variant of PTC (FV‑PTC).Lower MVD was observed in FV‑PTC relative to the classic variant of PTC (CV‑PTC). The frequency of VEGF‑positive tumors was higher in CV‑PTC than in FV‑PTC. A significant association between COX‑2 and p27 expression was observed in FV‑PTC but not in CV‑PTC.

CONCLUSIONS

These results suggest that VEGF, COX‑2, and p27 may be important biological markers that determine the angiogenic and lymphangiogenic potentials of PTC, particularly between the follicular and classic variants.