The age- and shorter telomere-dependent TERT promoter mutation in follicular thyroid cell-derived carcinomas

Co-existence of BRAFV600E and TERT promoter mutations in papillary thyroid carcinoma is associated with tumor aggressiveness, but not with lymph node metastasis

BACKGROUND

Mutations of BRAF^V600E and TERT promoters are associated with thyroid cancer development. This study further investigated association of these mutations with clinicopathological characteristics from patients with papillary thyroid carcinoma (PTC).

METHODS

Tumor tissues from 342 PTC patients were obtained for DNA extraction and polymerase chain reaction amplification to detect the BRAF^V600E mutation using amplification-refractory mutation system-polymerase chain reaction. TERT promoter mutations were assessed using Sanger DNA sequencing. The association of these gene mutations with clinicopathological characteristics was then statistically analyzed.

RESULTS

Two hundred and seventy of 342 (78.9%) PTC patients harbored the BRAF^V600E mutation, which was associated with older age male patients. Moreover, TERT promoter mutations occurred in 12 of 342 (3.5 %) PTC patients, all of whom also had the BRAF mutation. One hundred thirty-three patients with papillary thyroid microcarcinoma (PTMC) had no TERT mutations. Statistically, the coexistence of BRAF and TERT promoter mutations were significantly associated with older age, larger tumor size, extrathyroidal extension, and advanced tumor stage, but not with central lymph node metastasis, lateral lymph node metastasis, numbers of lymph node metastasis >5, and numbers of involved/harvested lymph nodes (No. of LNs involved or harvested). The multivariate analyses showed older age (odds ratio [OR], 2.194; 95% CI: 1.117-4.311; p=0.023), larger tumor size (OR, 4.100; 95% CI: 2.257-7.450; p<0.001), and multiplicity (OR, 2.240; 95% CI: 1.309-3.831; p=0.003) were all independent predictors for high prevalence of extrathyroidal extension. However, there was no statistical association with any clinicopathological characteristics except for Hashimoto thyroiditis in PTMC.

CONCLUSION

The current study demonstrated that the coexistence of BRAF and TERT promoter mutations were associated with the PTC aggressiveness, although these mutations were not associated with PTC lymph node metastasis or with PTMC.

Telomerase reverse transcriptase mutations are independent predictor of disease-free survival in Middle Eastern papillary thyroid cancer

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer. Tumor recurrence occurs in ∼20% of PTCs and some reach advanced stages. Promoter mutation in the telomerase reverse transcriptase (TERT) gene is identified to be a prognostic marker in PTC. However, the contribution of TERT promoter mutation to cancer progression in PTC patients is still not fully understood. In this study, we investigated the incidence of TERT promoter mutations and TERT protein expression and their association with clinicopathological outcomes in a large cohort of PTC samples using direct sequencing technology and immunohistochemistry. Furthermore, two PTC cell lines were utilized to investigate role of TERT mutations in mediating metastasis. Two promoter hotspot mutations C228T and C250T were identified in 18.0% (167/927) of our cohort and were significantly associated with poor 5 years disease-free survival and distant metastasis of PTC. TERT protein overexpression was noted in 20.1% of our PTC cohort and was significantly associated with poor prognostic markers such as older age, extrathyroidal extension and Stage IV tumors. A significant association was also found between TERT overexpression and epithelial-mesenchymal transition (EMT) markers. Functional analysis showed that TERT inhibition reduced cell growth, invasion, migration and angiogenesis in PTC via suppression of EMT in PTC cells. Our results suggest that TERT promoter mutation is an independent predictor of disease-free survival and might drive the metastasis, and downregulation of TERT could potentiate antitumor and antimetastatic activities in PTC.

Genetic landscape of papillary thyroid carcinoma in the Chinese population

Improvement in the clinical outcome of human cancers requires characterization of the genetic alterations underlying their pathogenesis. Large-scale genomic and transcriptomic characterization of papillary thyroid carcinomas (PTCs) in Western populations has revealed multiple oncogenic drivers which are essential for understanding pathogenic mechanisms of this disease, while, so far, the genetic landscape in Chinese patients with PTC remains uncharacterized. Here, we conducted a large-scale genetic analysis of PTCs from patients in China to determine the mutational landscape of this cancer. By performing targeted DNA amplicon and targeted RNA deep-sequencing, we elucidated the landscape of somatic genetic alterations in 355 Chinese patients with PTC. A total of 88.7% of PTCs were found to harbor at least one candidate oncogenic driver genetic alteration. Among them, around 72.4% of the cases carried BRAF mutations; 2.8% of cases harbored RAS mutations; and 13.8% of cases were characterized with in-frame gene fusions, including seven newly identified kinase gene fusions. TERT promoter mutations were likely to occur in a sub-clonal manner in our PTC cohort. The prevalence of somatic genetic alterations in PTC was significantly different between our Chinese cohort and TCGA datasets for American patients. Additionally, combined analyses of genetic alterations and clinicopathologic features demonstrated that kinase gene fusion was associated with younger age at diagnosis, larger tumor size, and lymph node metastasis in PTC. With the analyses of DNA rearrangement sites of RET gene fusions in PTC, signatures of chromosome translocations related to RET fusion events were also depicted. Collectively, our results provide fundamental insight into the pathogenesis of PTC in the Chinese population. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The association between the TERT rs2736100 AC genotype and reduced risk of upper tract urothelial carcinomas in a Han Chinese population

Upper tract urothelial carcinomas (UTUCs) are originated from urothelium, and consist of renal pelvic carcinomas (RPCs) and ureter carcinomas (UCs). Most UTUCs have already become invasive when diagnosed and there is thus a need to identify high-risk populations for preventive intervention. Recent evidence has accumulated supporting common single nucleotide polymorphisms (SNPs) to be associated with increased risk of various malignancies. However, little is known about susceptibility loci in relation to UTUC development. We genotyped telomerase reverse transcriptase (TERT) rs2736100 variants, the SNP associated with a risk of multiple-types of cancer, in patients with UTUC (n = 212) and evaluated the relationship between the rs2736100 and UTUC risk by comparing to 289 healthy controls. Neither AA nor CC genotypes differed significantly between cases and controls, while the AC-carriers were associated with a reduced risk of UTUC compared to the homozygous AA (OR = 0.583; 95% CI: 0.388 − 0.875; P = 0.012) or AA + CC genotypes (0.613; 95% CI: 0.428 − 0.879; P = 0.010). Further analyses showed that the AC variant conferred a lower risk for early stage UTUCs or those with a wt TERT promoter. When UTUCs were sub-grouped into UCs and RPCs, the AC genotype still predicts a significantly lower risk for UC (P = 0.045, OR = 0.597, 95% CI: 0.370 − 0.963), while at a border line significance for RPC (P = 0.055, OR = 0.597, 95% CI: 0.324 − 0.976). Collectively, the rs2736100 AC variant predicts a reduced risk to develop UTUC.

Telomerase reverse transcriptase promoter mutations in hepatitis B virus-associated hepatocellular carcinoma

Telomerase reverse transcriptase (TERT) promoter mutations are among the most frequent noncoding somatic mutations in multiple cancers, including hepatocellular carcinoma (HCC). The clinical and pathological implications of TERT promoter mutations in hepatitis B virus (HBV)-associated HCC have not been resolved. To investigate TERT promoter mutations, protein expression, and their clinical-pathological implications, we sequenced the TERT promoter region for hotspot mutations in HCC tissues and performed immunostaining for TERT protein expression from HBV-associated HCC in Chinese patients. Of 276 HCC tumor DNA samples sequenced, 85 (31%) carried TERT promoter mutations. TERT promoter mutations were more frequent in those with low α-fetoprotein (AFP) serum levels (p = 0.03), advanced age (p = 0.04), and in those lacking HCC family history (p = 0.02), but were not correlated with HCC stages and grades. TERT protein levels were higher in HCC (n = 28) compared to normal liver tissues (n = 8) (p =0.001), but did not differ between mutated and non-mutated tumor tissues. In conclusion, TERT promoter mutations are common somatic mutations in HCC of Han Chinese with HBV infection. Detection of TERT promoter mutations in those with low levels of AFP may aid diagnosis of HCC with atypical presentation.

The genetic difference between Western and Chinese urothelial cell carcinomas: infrequent FGFR3 mutation in Han Chinese patients

Urothelial cell carcinoma (UCC) includes urothelial bladder carcinoma (UBC), renal pelvic carcinoma (RPC) and ureter carcinoma (UC), and its incidence varies dependent on geographical areas and tumor locations, which indicates different oncogenic mechanisms and/or different genetic susceptibility/environment exposure. The activating mutations of the fibroblast growth factor receptor 3 (FGFR3) gene and telomerase reverse transcriptase (TERT) promoter are the most frequent genetic events in UCCs. These mutations have clinical utilities in UCC initial diagnostics, prognosis, recurrence monitoring and management. However, the vast majority of the results are obtained from studies of UCC patients in Western countries, and little has been known about these in Han Chinese patients. In the present study, we screened the FGFR3 gene and TERT promoter for mutations in 116 UBC, 91 RPC and 115 UC tumors from Han Chinese patients by using Sanger Sequencing. TERT promoter mutations occurred at a high frequency in these UCC patients, comparable with that seen in Western patients, however, the FGFR3 mutation was surprisingly lower, only 9.4% for UBCs, 8.8% for RPCs and 2.6% for UCs, respectively. Taken together, the FGFR3 gene is an infrequent target in the pathogenesis of Han Chinese UCCs, and its mutation detection and targeted therapy have limited clinical utility in these patients. Our results underscore the need for extensive characterization of cancer genomes from diverse patient populations, thereby contributing to precision medicine for cancer treatment and prevention.

Ultrasound and clinicopathological features of papillary thyroid carcinomas with BRAF and TERT promoter mutations

This study is to investigate if any relationship exists between the telomerase reverse transcriptase (TERT) promoter or proto-oncogene BRAF mutation and ultrasound (US) and clinicopathological features of papillary thyroid carcinomas (PTCs). The study included 150 patients with surgically confirmed PTC from October 1994 to December 2004. According to the existence of TERT promoter or BRAF mutations, we categorized patients into three groups (no mutation, BRAF mutation alone, or TERT+BRAF mutations) and analyzed the relationships between TERT promoter or BRAF mutation and US and clinicopathological features. The rate of recurrence or death according to mutation analysis was estimated. There were 35 (23.3%) cases with no mutation, 104 (69.3%) with BRAF mutation alone, and 11 (7.3%) with TERT+BRAF mutations. As the number of genetic mutations increased from no mutation to BRAF mutation alone to both BRAF and TERT mutations, the proportions of hypoechogenicity, non-parallel orientation, spiculated/microlobulated margin, microcalcifications, and high suspicion category increased. PTCs with TERT+BRAF mutations recurred more frequently than other groups (odd ratio = 17.921 and 31.468). The intervals to recurrence and overall survival were significantly shorter in the TERT+BRAF mutation group than in the other groups (Ps <.0001). PTCs with no mutation, with BRAF mutation alone, and with both TERT and BRAF mutations linearly increase in the probability of displaying malignant US features. In PTCs, the coexistence of BRAF with TERT mutations is more strongly correlated with recurrence and mortality than BRAF mutation alone.

Molecular alterations of coexisting thyroid papillary carcinoma and anaplastic carcinoma: identification of TERT mutation as an independent risk factor for transformation

Thyroid papillary carcinoma is the most common endocrine neoplasm and generally carries a favorable prognosis. However, a small subset of papillary carcinomas transforms into anaplastic carcinoma, an undifferentiated cancer with a dismal prognosis. Recent studies using next-generation sequencing revealed the genomic landscape of papillary carcinoma and anaplastic carcinoma. However, risk factors for anaplastic transformation in papillary carcinoma remain obscure. In the present study, we investigated molecular alterations of papillary carcinoma and anaplastic carcinoma components in 27 tumors in which anaplastic carcinoma coexisted with antecedent papillary carcinoma. We conducted direct sequencing for BRAF, TERT promoter and PIK3CA, and immunohistochemistry for p53, TTF-1 and subunits of the SWI/SNF complex (ARID1A, ARID1B, ATRX, SMARCA2, SMARCA4, SMARCB1, and PBRM1). BRAF^V600E and TERT promoter mutated at the rate of 90% and 95%, respectively, and these mutational statuses were almost identical between the papillary carcinoma and anaplastic carcinoma components. PIK3CA mutation was positive in 33% of our samples with a heterogeneous mutation pattern of the papillary carcinoma and anaplastic carcinoma components. Aberrant expression of p53 and loss of TTF-1 were present in 63 and 59%, respectively, and these two alterations were confined to the anaplastic carcinoma components. There was a loss of the SWI/SNF complex in a subset of the tumors with a heterogeneous pattern of the papillary carcinoma and anaplastic carcinoma components: SMARCA4 in 4% and PBRM1 in 4%. In a multivariate comparison between the antecedent papillary carcinoma components and control papillary carcinomas without anaplastic transformation, TERT promoter mutation was independently associated with anaplastic transformation. Collectively, papillary carcinoma-derived anaplastic carcinomas are characterized by BRAF and TERT promoter mutations, and these mutations occur prior to anaplastic transformation. Alterations of PIK3CA and the SWI/SNF complex are relatively rare and temporally heterogeneous. Of note, a papillary carcinoma harboring TERT promoter mutation is at higher risk for anaplastic transformation.

Genomic Hallmarks of Thyroid Neoplasia

The genomic landscape of thyroid cancers that are derived from follicular cells has been substantially elucidated through the coordinated application of high-throughput genomic technologies. Here, I review the common genetic alterations across the spectrum of thyroid neoplasia and present the resulting model of thyroid cancer initiation and progression. This model illustrates the striking correlation between tumor differentiation and overall somatic mutational burden, which also likely explains the highly variable clinical behavior and outcome of patients with thyroid cancers. These advances are yielding critical insights into thyroid cancer pathogenesis, which are being leveraged for the development of new diagnostic tools, prognostic and predictive biomarkers, and novel therapeutic approaches.

Preclinical and clinical implications of TERT promoter mutation in glioblastoma multiforme

The promoter region of the telomerase reverse transcriptase gene (TERT) is mutated in a subpopulation of patients with glioblastoma multiforme (GBM). In the present study, preclinical and clinical implications of the mutation were analyzed in 25 GBMs to evaluate its utility as a therapeutic target. Associations between the TERT promoter mutation and a number of preclinical/clinical characteristics were analyzed. Notably, the TERT promoter mutation was identified in 92.3% of GBMs where dissociated cells revealed in vitro sphere formation capacity; while the TERT promoter mutation was identified in 33.3% of GBMs without in vitro sphere formation capacity (P=0.004). In addition, this significantly increased mutation rate was observed in GBMs with in vivo tumorigenic potential (80% vs. 0%; P=0.004). Furthermore, patients with GBM exhibiting the TERT promoter mutation demonstrated significantly decreased overall survival rate compared with patients lacking this mutation (81.7 vs. 152.6 weeks; P=0.026). The results of the present study indicated that the TERT promoter mutation is associated with the self-renewal capacity of GBM cells and clinical aggressiveness of GBMs, which may be translated to a targeting therapy against TERT to inhibit the self-renewal of GBM cells.

Sensitive droplet digital PCR method for detection of TERT promoter mutations in cell free DNA from patients with metastatic melanoma

BACKGROUND

Currently mainly BRAF mutant circulating tumor DNA (ctDNA) is utilized to monitor patients with melanoma. TERT promoter mutations are common in various cancers and found in up to 70% of melanomas, including half of BRAF wild-type cases. Therefore, a sensitive method for detection of TERT promoter mutations would increase the number of patients that could be monitored through ctDNA analysis.

METHODS

A droplet digital PCR (ddPCR) assay was designed for the concurrent detection of chr5:1,295,228 C>T and chr5:1,295,250 C>T TERT promoter mutations. The assay was validated using 39 melanoma cell lines and 22 matched plasma and tumor samples. In addition, plasma samples from 56 metastatic melanoma patients and 56 healthy controls were tested for TERT promoter mutations.

RESULTS

The established ddPCR assay detected TERT promoter mutations with a lower limit of detection (LOD) of 0.17%. Total concordance was demonstrated between ddPCR and Sanger sequencing in all cell lines except one, which carried a second mutation within the probe binding-site. Concordance between matched plasma and tumor tissue was 68% (15/22), with a sensitivity of 53% (95% CI, 27%-79%) and a specificity of 100% (95% CI, 59%-100%). A significantly longer PFS (p=0.028) was evident in ctDNA negative patients. Importantly, our TERT promoter mutations ddPCR assay allowed detection of ctDNA in 11 BRAF wild-type cases.

CONCLUSIONS

The TERT promoter mutation ddPCR assay offers a sensitive test for molecular analysis of melanoma tumors and ctDNA, with the potential to be applied to other cancers.

Low frequency of TERT promoter mutations in a series of well-differentiated follicular-patterned thyroid neoplasms

The diagnostic and clinical approaches to follicular-patterned thyroid neoplasms often create dilemmas for pathologist and clinicians. The molecular analysis of these tumors could be a useful tool to overcome diagnostic limitations. The most frequent molecular alterations are point mutations of RAS family genes. Nevertheless, other molecular markers should be taken into account for their prognostic role, as BRAF mutations and the recently described telomerase reverse transcriptase (TERT) promoter mutation. We investigated the prevalence and the possible role of TERT promoter, BRAF, and RAS mutations in a series of low-risk well-differentiated follicular-patterned thyroid neoplasms. We evaluated 60 follicular adenomas (FA), 29 minimally invasive follicular carcinomas (MIFTC), 82 papillary carcinomas, follicular variant (FVPTC), and 16 noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFT-P) for the molecular status of BRAF, H-, N-, K-RAS, and TERT and correlated it with clinic-pathological parameters of tumors. Fifty-seven (30.5%) follicular neoplasms were mutated. In particular, we found 44 RAS mutated neoplasms (23.5%), specifically three FAs, 29 FVPTCs, five NIFT-Ps, and seven FTCs. BRAF mutations were found in ten FVPTCs. Finally, TERT promoter mutations were observed in three FVPTCs and three FTCs; three of them harbored also N-RAS mutations. We confirmed the absence of TERT promoter mutations in benign follicular neoplasms and found a low frequency of TERT promoter mutations in our selected cohort of low-risk follicular-patterned malignancies, speculating their role in the progression and de-differentiation of thyroid cancer.

TERT Promoter Hypermethylation in Gastrointestinal Cancer: A Potential Stool Biomarker

BACKGROUND

There is a high demand for noninvasive screening tools for gastrointestinal cancer (GIC) detection, and GIC-specific markers are required for such purposes. It is established that induction of the telomerase reverse transcriptase gene (TERT) coupled with telomerase activation is essential for cancer development/progression and aberrant TERT promoter methylation of specific 5'-C-phosphate-G-3' (CpGs) has been linked to TERT induction in oncogenesis. Here we analyzed TERT promoter methylation in fecal samples from GIC patients and healthy adults and determined its value as a stool biomarker for GIC detection.

MATERIALS AND METHODS

Sixty-nine GIC patients (34 colorectal carcinoma and 35 gastric cancer) and 62 healthy adults were recruited and fecal samples were collected. Paired tumors and adjacent non-cancerous tissues from 34 patients and normal mucosa tissues from 12 healthy individuals were collected. TERT promoter methylation density was determined using pyrosequencing.

RESULTS

We identified two GIC-specific methylation sites at -218 (CpG site 1) and -210 (CpG site 2) in the TERT promoter in tumor tissues. Methylated TERT promoter CpG sites 1 and 2 were also detectable in patient stool, while only background levels were observed in healthy individuals. The overall sensitivity reached 52.2% (95% confidence interval [CI]: 48.3-56.0) for fecal methylated TERT promoter assays at 90% specificity, which was comparable to other known stool methylation markers for GIC detection. The combined assays of fecal TERT promoter methylation and occult blood (OB) significantly improved sensitivity and specificity in colorectal cancer (area under curves for methylation alone: 0.798, 95% CI: 0.707-0.889 vs. methylation + OB: 0.920, 95% CI: 0.859-0.981; p = .028), but not in gastric cancer.

CONCLUSION

This proof-of-concept study suggests the feasibility of stool TERT promoter methylation analyses as an additional tool in noninvasive GIC screening.

IMPLICATIONS FOR PRACTICE

Induction of telomerase reverse transcriptase (TERT) expression coupled with telomerase activation is essential for cancer development/progression, while aberrant TERT promoter methylation has been linked to TERT induction in oncogenesis. We identified two cancer-specific methylation sites (CpG1 and 2) in the TERT promoter in tumors from GIC patients. Methylated TERT promoter CpG sites 1 and 2 were detectable in patient stool, while only background levels were observed in healthy individuals. The sensitivity and specificity was comparable to other known stool methylation markers for GIC detection. This proof-of-concept study suggests the feasibility of stool TERT promoter methylation analyses for noninvasive screening of GIC.

[Molecular Pathogenesis of Thyroid Nodules: Relevance for Clinical Care]

Thyroid nodules represent heterogeneous tumors with distinct molecular signatures. While benign thyroid nodules correspond to poly- or monoclonal tumors, thyroid carcinomas are monoclonal and thus "real" neoplasms. These are caused by somatic mutations that lead to the constitutive activation of specific signaling cascades and determine the corresponding histology and also partly the functional phenotype of the thyroid tumor. Dedifferentiation of thyroid carcinomas is accompanied by the occurrence of additional mutations in the tumors. The mutation load of thyroid carcinomas correlates with their biological behavior. In clinical practice, detection of somatic mutations can help in the cytological differential diagnosis. In the prognostic assessment of thyroid tumors, proof of classical oncogene mutations (BRAF, RAS) has little relevance. Other genetic alterations, especially TERT promoter mutations that occur with increasing frequency in advanced thyroid carcinomas, probably have a prognostic significance. The molecular signature, however, is of great relevance for the development and application of targeted therapies in advanced carcinomas (radioactive iodine-refractory DTC, PDTC and ATC, metastatic medullary carcinoma). For this, there is increasing evidence from clinical studies and case reports that underline the concept of "oncogene addiction" as a pathogenetically relevant mechanism of thyroid tumorigenesis and carcinogenesis.

Risk prediction in children and adults less than 45 years old with papillary thyroid cancer

The incidence of papillary thyroid cancer is increasing faster than any other cancer in young patients. The purpose of this review is to discuss the most recent determinants of risk of recurrence and compromised outcomes in this population. Areas covered: This review discusses the most updated data on patient age, including children and young adults, extent of disease and subsequent dynamic staging over time, molecular markers for disease aggressiveness, adequacy of surgical resection and surgeon volume, and novel therapies for advanced non-resectable disease as predictors of patient outcomes. Expert commentary: Young patients enjoy excellent outcomes, with long-term survivorship, but face higher risks of short-term complications and disease recurrence. Thoughtful evaluation of the extent of disease, tumor features associated with more aggressive behavior, the presence of locoregional or distant metastases, and an understanding of molecular changes in their tumors are important areas of consideration. High-volume surgeons should work collaboratively with endocrinologists, radiologists, and pathologists specializing in thyroid cancer to help patients achieve excellent outcomes. Emerging data challenging the status quo regarding the relative importance of patient age, tumor features, and dynamic risk-adjustment for overall prognosis of these patients will likely impact future care and staging systems.

GABRB2 plays an important role in the lymph node metastasis of papillary thyroid cancer

BACKGROUND

Thyroid cancer is a common malignant tumor of the endocrine system. Its incidence has increased continuously worldwide for the past three decades. With advanced sequencing technology, we discovered that GABRB2 gene is overexpressed in tumor tissues and closely associated with vertebrate nervous systems. However, its role in cancer remains unclear.

METHODS

We conducted a massively parallel whole transcriptome resequencing and a comprehensive analysis of matched papillary thyroid carcinoma (PTC) tumors and normal tissues in 19 patients. Results showed that GABRB2 expression was significantly upregulated in thyroid cancer. Forty-five pairs of tumors and normal tissues were subjected to reverse transcription polymerase chain reaction to validate previous findings. The specific functions of GABRB2 in PTC cell lines (BCPAP, TPC1, and KTC-1) transfected with small interfering RNA were determined through cell colony formation, Cell Counting Kit-8, Transwell migration, Transwell invasion, and apoptosis assays. The effect of DNA demethylation on this gene was also examined.

RESULTS

GABRB2 was remarkably overexpressed in primarily sequenced PTC tumors and validation cohort (T: N = 4.94 ± 3.43:0.83 ± 1.71, P < 0.001), and this observation was consistent with that in the TCGA cohort (T: N = 38.92 ± 35.53:0.30 ± 0.55, P < 0.001). GABRB2 overexpression was correlated with lymph node metastasis in both cohorts (P < 0.01). In vitro experiments revealed that GABRB2 downregulation significantly inhibited the colony formation, migration, and invasion of the three PTC cell lines.

CONCLUSION

GABRB2 plays important tumorigenic functions and acts as a novel oncogene in PTC.

Thyrospheres from B-CPAP Cell Line with BRAF and TERT Promoter Mutations have Different Functional and Molecular Features than Parental Cells

Human thyroid cancer derived cell lines are widely used to study the mechanisms involved in thyroid carcinogenesis. However, there is limited availability of non-cross-contaminated cancer cell lines derived from papillary thyroid carcinoma (PTC), and the B-CPAP cell line is one of the few such lines. B-CPAP cells have been genetically and cytogenetically well-characterized, but details of their stemness features remain uncertain. Considering that this cell line is extensively used for in vitro studies on thyroid tumorigenesis, we broaden its functional and molecular profiles as well as the tumorigenic capacity. We used functional assays (sphere-forming capacity and efficiency), assessed self-renewal and propagation efficiency and tested in vivo tumorigenicity in Hsd:Athymic Nude-Foxn1^nu mice. Expression of markers of stemness, differentiation, and epithelial-mesenchymal transition were estimated at RNA and protein levels in adherent parental cells and sphere-forming cells. Functional aspects and stemness features were compared with normal thyrocytes. Protein expression of xenograft tumors was evaluated by immunohistochemistry. B-CPAP sphere-forming cells were able to form thyrospheres theoretically indefinitely in an appropriate serum-free medium, reverting to the adherent parental cell phenotype when cultured in differentiation medium. Different expression of ALDH1-A1 and CD44 stemness markers and TTF-1 and CK19 differentiation markers allowed discrimination between isolated sphere-forming cells and adherent parental cells, indicating that sphere-forming cells retained stem-like features. In keeping with these observations, tumorigenicity assays confirmed that, relative to parental adherent cells, thyrospheres had enhanced capacity to initiate xenograft tumors. Thyrospheres from normal cell line retained very low functional capacity, as well as different stemness markers expression compared to tumor thyrospheres. Our findings may constitute a useful background to develop an in vitro model for assessing the origin and progression of papillary thyroid carcinoma bearing BRAF^V600E and TERT promoter mutations.

TERT, BRAF, and NRAS in Primary Thyroid Cancer and Metastatic Disease

CONTEXT

Little is known about the frequency of key mutations in thyroid cancer metastases and its relationship with the primary tumor genotype.

OBJECTIVES

To evaluate the frequency of TERT promoter (TERTp), BRAF, and NRAS mutations in metastatic thyroid carcinomas, analyzing primary thyroid tumors, lymph node metastases (LNMs), and distant metastases.

DESIGN AND PATIENTS

Mutation analysis was performed in 437 tissue samples from 204 patients, mainly with papillary thyroid carcinomas (PTCs; n = 180), including 196 LNMs and 56 distant metastases. All the distant metastases included corresponded to radioiodine-refractory metastatic tissue.

RESULTS

We found the following mutation frequency in primary PTCs, LNMs, and distant metastases, respectively: TERTp: 12.9%, 10.5%, and 52.4%; BRAF: 44.6%, 41.7%, and 23.8%; and NRAS: 1.2%, 1.3%, and 14.3%. There was a significant concordance between the primary tumor genotype and the corresponding LNM for all the genes, in particular BRAF-mutated PTC. The overall concordance between primary tumors and respective distant metastases was low. In the group of patients with PTCs, we found a high frequency of TERTp mutations and a low frequency of BRAF mutations in distant metastases, in comparison with the paired primary tumors. When present in distant metastases, BRAF mutations frequently coexisted with TERTp mutations.

CONCLUSIONS

When the genotype of primary tumors is compared with the genotype of LNMs, the concordance is high for all the genes studied. On the other hand, distant metastases show an enrichment in TERTp mutations and a decrease in BRAF mutations. TERTp mutations may play a role in distant metastases.

Frequent BRAF V600E and Absence of TERT Promoter Mutations Characterize Sporadic Pediatric Papillary Thyroid Carcinomas in Japan

Pediatric papillary thyroid carcinoma (PTC) has unique features but requires further genetic investigation. Moreover, there has been increasing concern about the risk for pediatric PTC in Japan after the Fukushima accident. This study aims to evaluate the frequencies of BRAF and TERT promoter mutations and to examine their significance in non-radiation-associated pediatric PTCs in Japan. We enrolled 81 pediatric PTC patients aged ≤20 years. The control group included 91 adult PTCs from patients >20 years old. BRAF and TERT mutations were analyzed by allele-specific-PCR and/or Sanger sequencing. Compared with adult PTCs, pediatric PTCs exhibited larger tumor size, more frequent lymph node metastasis, and less classical histology. The prevalence of BRAF ^V600E in pediatric PTCs was 54% and significantly lower than that in adults of 85%. In the pediatric PTCs, BRAF ^V600E was positively associated with older age, classical histology, and the lymph node metastasis but independent from other clinicopathological factors. TERT mutations were identified in 13% of adults and in none of the pediatric PTCs. In conclusion, pediatric PTCs are characterized by more advanced clinicopathological features, lower BRAF ^V600E frequency, and absence of TERT mutation. The BRAF ^V600E frequency in this study is similar to the reported BRAF ^V600E frequency in the ultrasonographically screened pediatric PTCs in Fukushima.

Mutation of the TERT promoter leads to poor prognosis of patients with non-small cell lung cancer

Mutations in the promoter region of telomerase reverse transcriptase (TERT) and alterations in telomere length (TL) have been the focus of research in various types of cancer. In the present study, the frequency and clinical characteristics of TERT promoter mutations and TL were studied in non-small cell lung cancers (NSCLC). TERT promoter mutations and TL were analyzed in 188 patients using DNA sequencing and the reverse transcription-quantitative polymerase chain reaction, respectively. The TERT promoter mutation rate was observed to be 2.2% (4/188 NSCLC cases), and it was significantly associated with regional lymph node invasion (P<0.001). No significant difference in TL was observed between the patients with and without TERT promoter mutations. TL was decreased in males (P=0.058 vs. females) and smokers (P=0.008 vs. non-smokers). Survival analyses demonstrated poor prognoses for patients with NSCLC with TERT promoter mutations (P<0.001). Multivariate survival analyses demonstrated that TERT promoter mutations were an independent prognostic marker for poor overall survival (P=0.045). The results of the present study demonstrated that TERT promoter mutation was not frequent in NSCLC; however, it may have value as a prognostic marker in NSCLC.

Effects of Coexistent BRAFV600E and TERT Promoter Mutations on Poor Clinical Outcomes in Papillary Thyroid Cancer: A Meta-Analysis

BACKGROUND

The presence of a telomerase reverse transcriptase (TERT) promoter mutation has been suggested as a potential prognostic marker for thyroid cancer, and a synergistic association with the BRAF^V600E mutation has been demonstrated. The aim of this study was to verify the role of this genetic duet in papillary thyroid cancer (PTC).

METHODS

Studies of the association of BRAF^V600E and TERT promoter mutations with clinicopathologic features, recurrence, or PTC-related mortality were included from PubMed and Embase databases (inception to September 2016).

RESULTS

Thirteen eligible studies incorporating 4347 patients with PTC were included, and 283 (median 8.3%) of these patients had coexistent BRAF^V600E and TERT promoter mutations. The coexistence of the two mutations was far more strongly associated with high-risk clinicopathologic features than either mutation alone was, including advanced TNM stage (vs. BRAF^V600E: odds ratio [OR] = 4.19 [confidence interval (CI) 3.07-5.71]; vs. TERT: OR = 4.66 [CI 2.67-8.13]), extrathyroidal extension (vs. BRAF^V600E: OR = 3.1 [CI 2.2-4.37]; vs. TERT: OR = 5.66 [CI 3.02-10.6]), lymph node metastasis (vs. BRAF^V600E: OR = 1.59 [CI 1.16-2.17]; vs. TERT: OR = 2.03 [CI 1.22-3.38]), and distant metastasis (vs. BRAF^V600E: OR = 11.76 [CI 5.63-24.58]). The coexistence of the mutations showed the highest risk of recurrence (coexistence vs. no mutations: hazard ratio [HR] = 6.60 [CI 3.82-11.40]; BRAF^V600E vs. no mutations: HR = 1.31 [CI 0.49-3.46]; TERT vs. no mutations: HR = 3.38 [CI 0.85-13.35]). Moreover, PTC-related mortality was significantly higher with coexistent mutations than in the presence of BRAF^V600E alone (HR = 20.07 [CI 8.37-48.09]).

CONCLUSIONS

Coexistent BRAF^V600E and TERT promoter mutations have a synergistic effect on clinical outcomes in PTC, whereas each mutation alone has a modest effect. Therefore, molecular testing of BRAF^V600E and TERT promoter mutations together is useful in assessing risk stratification of PTC.

Oncogenesis of Thyroid Cancer

Thyroid neoplasms encompass a variety of lesions that range from benign adenomas to malignancies. These latter can be well-differentiated, poorly differentiated or undifferentiated (anaplastic) carcinomas. More than 95% of thyroid cancers are derived from thyroid follicular cells, while 2-3% (medullary thyroid cancers, MTC) originate from calcitonin producing C-cells. Over the last decade, investigators have developed a clearer understanding of genetic alterations underlying thyroid carcinogenesis. A number of point mutations and translocations are involved, not only in its tumorigenesis, but also as have potential use as diagnostic and prognostic indicators and therapeutic targets. Many occur in genes for several important signaling pathways, in particular the mitogen-activated protein kinase (MAPK) pathway. Sporadic (isolated) lesions account for 75% of MTC cases, while inherited MTC, often in association with multiple endocrine neoplasia (MEN) type 2A and 2B syndromes, constitute the remainder. However, non-MEN familial MTC may also occur. Advances in genetic testing have revolutionized the management of MTC, with prospects of genetic screening, testing and early prophylactic thyroidectomy. Ethical concerns of these advances are addressed.

Altered TERT promoter and other genomic regulatory elements: occurrence and impact

Study of genetic alterations, inherited or acquired, that increase the risk or drive cancers and many other diseases had remained mostly confined to coding sequences of the human genome. Data from genome wide associations studies, development of the Encyclopedia of DNA Elements (ENCODE), and a spurt in detection of driver somatic mutations have shifted focus towards noncoding regions of the human genome. The majority of genetic variants robustly associated with cancers and other syndromes identified through genome wide studies are located within noncoding regulatory regions of the genome. Genome wide techniques have put an emphasis on the role of three-dimensional chromosomal structures and cis-acting elements in regulations of different genes. The variants within noncoding genomic regions can potentially alter a number of regulatory elements including promoters, enhancers, insulators, noncoding long RNAs and others that affect cancers and various diseases through altered expression of critical genes. With effect of genetic alterations within regulatory elements dependent on other partner molecules like transcription factors and histone marks, an understanding of such modifications can potentially identify extended therapeutic targets. That concept has been augmented by the detection of driver somatic noncoding mutations within the promoter region of the telomerase reverse transcriptase (TERT) gene in different cancers. The acquired somatic noncoding mutations within different regulatory elements are now being reported in different cancers with an increased regularity. In this review we discuss the occurrence and impact of germline and somatic alterations within the TERT promoter and other genomic regulatory elements.

Hobnail variant of papillary thyroid carcinoma: molecular profiling and comparison to classical papillary thyroid carcinoma, poorly differentiated thyroid carcinoma and anaplastic thyroid carcinoma

BACKGROUND

As a rare but aggressive papillary thyroid carcinoma (PTC) variant, the genetic changes of hobnail variant of PTC (HVPTC) are still unclear.

RESULTS

The prevalence of HVPTC was 1.69% (18/1062) of all PTC diagnosed in our cohort. 73 samples from 55 patients (17 HVPTC, 26 CPTC, 7 PDTC and 5 ATC) were successfully analyzed using targeted NGS with an 18-gene panel. Thirty-seven mutation variant types were identified among 11 genes. BRAF V600E mutation was the most common mutation, which is present in almost all HVPTC samples (16/17, 94%), most CPTC samples (20/26, 77%), and none of the ATC and PDTC samples. TERT promoter mutation (C228T) was identified in 2 ATC and one HVPTC patient. RAS and TP53 mutation are almost exclusively present among ATC and PDTC samples although TP53 mutation was also observed in 3 HVPTC patients. Six different GNAS mutations were identified among 8 CPTC patients (31%) and none of the HVPTC patients. The only patient who died of disease progression harbored concomitant TERT C228T mutation, BRAF V600E mutation and TP53 mutation.

METHODS

HVPTC cases were identified from a group of 1062 consecutive surgical specimens diagnosed as PTC between 2000 and 2010. Targeted next-generation sequencing (NGS) was applied to investigate the mutation spectrum of HVPTC, compared to classical PTC (CPTC), poorly differentiated thyroid carcinoma (PDTC) and anaplastic thyroid carcinoma (ATC).

CONCLUSION

As an aggressive variant of PTC, HVPTC has relatively specific molecular features, which is somewhat different from both CPTC and ATC/PDTC and may underlie its relatively aggressive behavior.

BRAF and TERT promoter mutations in the aggressiveness of papillary thyroid carcinoma: a study of 653 patients

The role of telomerase reverse transcriptase (TERT) gene promoter mutations in the aggressiveness of papillary thyroid cancer (PTC) remains to be further investigated. Here we examined the relationship of TERT promoter mutations and BRAF V600E with the clinicopathological features of PTC in 653 patients. Sanger sequencing of genomic DNA from primary PTC tumors was performed for mutation detection and genotype-clinicopathological correlation of the tumor was analyzed. BRAF V600E and TERT promoter mutations were found in 63.7% (416 of 653) and 4.1% (27 of 653) of patients, respectively; the latter became 9.8% when only tumors ≥ 1.5 cm were analyzed. TERT promoter mutations occurred more frequently in BRAF mutation-positive cases compared to wild-type cases, being 5.3% in the former versus 2.1% in the latter (P = 0.050). BRAF and TERT promoter mutations were each significantly associated with high-risk clinicopathological features of PTC, such as old patient age, large tumor size, extrathyroidal invasion, capsular invasion, and advanced disease stages. Coexistence of BRAF V600E and TERT promoter mutations was particularly associated with high-risk clinicopathological features, as exemplified by extrathyroidal invasion seen in 54.5% (12/22) of patients harboring both mutations versus 9.9% (23/232) of patients harboring neither mutation (P < 0.001). Thus, this study, the largest on TERT mutation so far, demonstrates a significant role of BRAF V600E and TERT promoter mutations in the aggressiveness of PTC, which is particularly robust and cooperative when the two mutations coexist. These results, together with previous studies, establish a significant role of these mutations in the aggressiveness of PTC.

Clinicopathological characteristics of TERT promoter mutation and telomere length in hepatocellular carcinoma

Promoter mutations in telomerase reverse transcriptase (TERT) and telomere length have been studied in various tumors. In the present study, the frequency and clinical characteristics of TERT promoter mutation and telomere length were studied in hepatocellular carcinoma (HCC). TERT promoter mutation and telomere length were analyzed in 162 tumor samples of the patients with HCC by sequencing and real-time PCR, respectively. The TERT promoter mutation rate was 28.8% (46/160) in HCC and was associated with males (P = 0.027). The telomere length was not significantly different in the presence of a TERT promoter mutation but was shorter in high-grade tumor stages (P = 0.048). Survival analyses showed that poor overall survival was associated with longer telomere length (P = 0.013). However, the TERT promoter mutation did not have a prognostic value for HCC. Multivariate survival analyses demonstrated that the telomere length was an independent prognostic marker for poor overall survival (hazard ratio = 1.75, 95% confidence interval: 1.046-2.913, P = 0.033). These data demonstrated that TERT promoter mutation is a frequent event in HCC; however, telomere length, but not the presence of a TERT promoter mutation, might have potential value as a prognostic indicator of HCC.

TERT biology and function in cancer: beyond immortalisation

Evasion of replicative senescence and proliferation without restriction, sometimes designated as immortalisation, is one of the hallmarks of cancer that may be attained through reactivation of telomerase in somatic cells. In contrast to most normal cells in which there is lack of telomerase activity, upregulation of TERT transcription/activity is detected in 80-90% of malignant tumours. In several types of cancer, there is a relationship between the presence of TERT promoter mutations, TERT mRNA expression and clinicopathological features, but the biological bridge between the occurrence of TERT promoter mutations and the aggressive/invasive features displayed by the tumours remains unidentified. We and others have associated the presence of TERT promoter mutations with metastisation/survival in several types of cancer. In follicular cell-derived thyroid cancer, such mutations are associated with worse prognostic features (age of patients, tumour size and tumour stage) as well as with distant metastases, worse response to treatment and poorer survival. In this review, we analyse the data reported in several studies that imply TERT transcription reactivation/activity with cell proliferation, tumour invasion and metastisation. A particular attention is given to the putative connections between TERT transcriptional reactivation and signalling pathways frequently altered in cancer, such as c-MYC, NF-κB and B-Catenin.

TERT promoter mutations in telomere biology

Telomere repeats at chromosomal ends, critical to genome integrity, are maintained through an elaborate network of proteins and pathways. Shelterin complex proteins shield telomeres from induction of DNA damage response to overcome end protection problem. A specialized ribonucleic protein, telomerase, maintains telomere homeostasis through repeat addition to counter intrinsic shortcomings of DNA replication that leads to gradual sequence shortening in successive mitoses. The biogenesis and recruitment of telomerase composed of telomerase reverse transcriptase (TERT) subunit and an RNA component, takes place through the intricate machinery that involves an elaborate number of molecules. The synthesis of telomeres remains a controlled and limited process. Inherited mutations in the molecules involved in the process directly or indirectly cause telomeropathies. Telomerase, while present in stem cells, is deactivated due to epigenetic silencing of the rate-limiting TERT upon differentiation in most of somatic cells with a few exceptions. However, in most of the cancer cells telomerase reactivation remains a ubiquitous process and constitutes one of the major hallmarks. Discovery of mutations within the core promoter of the TERT gene that create de novo binding sites for E-twenty-six (ETS) transcription factors provided a mechanism for cancer-specific telomerase reactivation. The TERT promoter mutations occur mainly in tumors from tissues with low rates of self-renewal. In melanoma, glioma, hepatocellular carcinoma, urothelial carcinoma and others, the promoter mutations have been shown to define subsets of patients with adverse disease outcomes, associate with increased transcription of TERT, telomerase reactivation and affect telomere length; in stem cells the mutations inhibit TERT silencing following differentiation into adult cells. The TERT promoter mutations cause an epigenetic switch on the mutant allele along with recruitment of pol II following the binding of GABPA/B1 complex that leads to mono-allelic expression. Thus, the TERT promoter mutations hold potential as biomarkers as well as future therapeutic targets.

TERT promoter Mutation and Its Association with Clinicopathological Features and Prognosis of Papillary Thyroid Cancer: A Meta-analysis

We performed a meta-analysis to elucidate the associations of the clinicopathological characteristics and prognostic factors of papillary thyroid cancer (PTC) with TERT promoter mutations. A literature search was performed of the PubMed and EMBASE databases using Medical Subject Headings and keywords. Individual study-specific odds ratios (ORs) and confidence intervals (CIs) were calculated. The average prevalence rate of TERT promoter mutations was 10.1%. TERT promoter mutations occurred more frequently in patients with larger tumors (p = 0.003). TERT promoter mutations were associated with advanced stage (OR = 3.11, 95% CI = 2.22–4.36), lymph node metastasis (OR = 1.82, 95% CI = 1.12–2.96), distant metastasis (OR = 4.18, 95% CI = 1.61–10.81), BRAF mutation positivity (OR = 2.71, 95% CI = 1.45–3.24), recurrence (OR = 3.91, 95% CI = 1.83–8.34), and mortality (OR = 8.13, 95% CI = 3.77–17.53). The associations of TERT promoter mutations with extrathyroidal invasion (OR = 1.98, 95% CI = 0.96–4.07), unifocality (OR = 1.36, 95% CI = 0.90–2.07), and vascular invasion (OR = 1.45, 95% CI = 0.92–2.30) were not significant. TERT promoter mutations are closely associated with aggressive clinicopathological characteristics and poorer prognosis in PTC.

Association of telomerase reverse transcriptase promoter mutations with clinicopathological features and prognosis of thyroid cancer: a meta-analysis

The clinicopathological and prognostic significance of telomerase reverse transcriptase (TERT) promoter mutations have been widely investigated in thyroid cancer; however, the results are still discrepant. Systematic searches were performed in PubMed, Web of Science, Scopus, Ovid, and the Cochran Library databases for relevant articles prior to April 2016. Mutation rates were synthesized by R statistical software. The odds ratio or standardized mean difference with 95% confidence interval was pooled by Stata. A total of 22 studies with 4,907 cases were included in this meta-analysis. TERT promoter mutations tended to present in aggressive histological types including poorly differentiated thyroid cancer (33.37%), anaplastic thyroid cancer (38.69%), and tall-cell variant papillary thyroid cancer (30.23%). These promoter mutations were likely to exist in older patients and males and were well associated with larger tumor size, extrathyroidal extension, vascular invasion, lymph node metastasis, distant metastasis, advanced tumor stage, disease recurrence/persistence, and mortality. In addition, TERT promoter mutations (especially C228T) tended to coexist with BRAF^V600E mutation, which indicated more aggressive tumor behavior. Therefore, TERT promoter mutations may be promising biomarkers for early diagnosis, risk stratification, prognostic prediction, and management of thyroid cancer.

Application of molecular biology of differentiated thyroid cancer for clinical prognostication

Although cancer outcome results from the interplay between genetics and environment, researchers are making a great effort for applying molecular biology in the prognostication of differentiated thyroid cancer (DTC). Nevertheless, role of molecular characterisation in the prognostic setting of DTC is still nebulous. Among the most common and well-characterised genetic alterations related to DTC, including mutations of BRAF and RAS and RET rearrangements, BRAF^V600E is the only mutation showing unequivocal association with clinical outcome. Unfortunately, its accuracy is strongly limited by low specificity. Recently, the introduction of next-generation sequencing techniques led to the identification of TERT promoter and TP53 mutations in DTC. These genetic abnormalities may identify a small subgroup of tumours with highly aggressive behaviour, thus improving specificity of molecular prognostication. Although knowledge of prognostic significance of TP53 mutations is still anecdotal, mutations of the TERT promoter have showed clear association with clinical outcome. Nevertheless, this genetic marker needs to be analysed according to a multigenetic model, as its prognostic effect becomes negligible when present in isolation. Given that any genetic alteration has demonstrated, taken alone, enough specificity, the co-occurrence of driving mutations is emerging as an independent genetic signature of aggressiveness, with possible future application in clinical practice. DTC prognostication may be empowered in the near future by non-tissue molecular prognosticators, including circulating BRAF^V600E and miRNAs. Although promising, use of these markers needs to be refined by the technical sight, and the actual prognostic value is still yet to be validated.

TERT promoter mutations and long-term survival in patients with thyroid cancer

TERT promoter mutations are emerging prognostic biomarkers in multiple cancers and are found in highly aggressive thyroid cancer. Our aim is to investigate the prognostic value of these mutations for the outcome of thyroid cancer-related mortality in a large cohort of thyroid cancer patients. This was a retrospective study of 409 patients (393 with differentiated thyroid cancer) with a median age of 44 years (range 16-81 years) and median follow-up of 13 years (interquartile range 11-16 years). Analyses of associations between mutational status and various clinicopathological variables were performed. TERT promoter mutations were identified in 32 (9.8%) papillary, 11 (16.7%) follicular and seven (43.8%) poorly differentiated/anaplastic thyroid cancer patients. The presence of TERT promoter mutations was associated with factors such as increased age (P < 0.001), extrathyroidal invasion (P = 0.01), increased stage at diagnosis (P < 0.001) and dedifferentiated histological type (P = 0.001). A TERT promoter mutation was independently associated with poorer overall survival in patients with differentiated thyroid cancer (10-year survival rate, 66.2% vs 98.3% for wild type; adjusted HR, 7.18; 95% CI: 2.77-18.59) and in patients with papillary cancer (74.2% vs 99.3%; 14.20; 3.03-66.68). Concomitant TERT and BRAF mutations worsened the survival rate of patients with papillary cancer (82.6% vs 99.4% for exclusively BRAF mutation alone; 5.62; 1.85-17.09). In conclusion, the presence of TERT promoter mutations is independently associated with increased mortality in patients with differentiated thyroid cancer. The results suggest that inclusion of TERT promoter mutation analysis with conventional clinicopathological evaluation can lead to better prognostication and management for individual patients.

Transcription Regulation of the Human Telomerase Reverse Transcriptase (hTERT) Gene

Embryonic stem cells and induced pluripotent stem cells have the ability to maintain their telomere length via expression of an enzymatic complex called telomerase. Similarly, more than 85%–90% of cancer cells are found to upregulate the expression of telomerase, conferring them with the potential to proliferate indefinitely. Telomerase Reverse Transcriptase (TERT), the catalytic subunit of telomerase holoenzyme, is the rate-limiting factor in reconstituting telomerase activity in vivo. To date, the expression and function of the human Telomerase Reverse Transcriptase (hTERT) gene are known to be regulated at various molecular levels (including genetic, mRNA, protein and subcellular localization) by a number of diverse factors. Among these means of regulation, transcription modulation is the most important, as evident in its tight regulation in cancer cell survival as well as pluripotent stem cell maintenance and differentiation. Here, we discuss how hTERT gene transcription is regulated, mainly focusing on the contribution of trans-acting factors such as transcription factors and epigenetic modifiers, as well as genetic alterations in hTERT proximal promoter.

TERT Promoter Mutation Predicts Radioiodine-Refractory Character in Distant Metastatic Differentiated Thyroid Cancer

Telomerase reverse transcriptase (TERT) promoter mutation has been reported to be associated with aggressive characteristics in differentiated thyroid cancer (DTC). This study examined the status of TERT mutation in distant metastatic DTC and evaluated the correlation between TERT mutation and radioiodine uptake, as well as that between TERT mutation and therapy response.

METHODS

TERT promoter and B-Raf proto-oncogene (BRAF) V600E mutation were retrospectively examined in primary tumors of 66 patients with distant metastatic DTC. Stimulated thyroglobulin (sTg) changes, radioiodine uptake status (avid or nonavid), and other imaging evidence were analyzed to evaluate therapy response. After a median follow-up of 46.5 mo (interquartile range, 29.0-70.5 mo), therapy response was classified as either disease control or refractory.

RESULTS

The prevalence of TERT mutations was 22.73% (15/66), of which C228T mutation was more prevalent (13/15) than C250T mutation (2/15). Rising sTg was noticed in 93.33% (14/15) of the TERT mutation group. Of cases negative for both mutations, 78.12% (25/32) presented with decreased sTg. TERT mutation closely correlated with a poor response to radioiodine therapy (P < 0.001), and all 15 patients were classified as refractory to radioiodine therapy, with a positive predictive value of 100% at the endpoint of follow-up. TERT mutation was associated with older mean age at diagnosis (P < 0.001), larger mean tumor diameter (P = 0.013), and greater likelihood of both BRAF mutation coexistence (P = 0.044) and radioiodine-refractory character (P < 0.001). In the 36 cases whose imaging results underwent semiquantitative analysis, TERT mutation significantly correlated with non-radioiodine avidity, with a much lower mean tumor-to-background ratio (obtained from postradioiodine whole-body scanning) than in TERT wild-type cases (P < 0.001). In addition, patients with distant metastatic DTC with TERT mutation were more likely to lose radioiodine avidity at the initial radioiodine therapy than were those with only BRAF mutation (8/8 vs. 5/11; Fisher exact test, P = 0.018).

CONCLUSION

TERT mutation closely associates with non-radioiodine avidity in distant metastatic DTC, and when compared with BRAF mutation, TERT mutation manifested a greater negative influence on radioiodine uptake. TERT mutation could also be used as an early predictor of radioiodine-refractory cases.

Clinicopathological significance of TERT promoter mutation in papillary thyroid carcinomas: a systematic review and meta-analysis

BACKGROUND

The prognostic value of the telomerase reverse transcriptase (TERT) promoter mutation, resulting in poor clinical outcomes of papillary thyroid carcinoma (PTC), has been generally confirmed. To data, there is no high-level evidence approving the association of TERT promoter mutation and aggressive clinical behaviours in PTC. To systematically evaluate it, a systematic review and meta-analysis of the published literatures were carried out.

METHODS

We conducted a systematic search in PubMed, EMBASE, OVID and Web of Science databases for relevant studies. We selected all the studies that reported clinicopathological features of PTC patients with information available on TERT promoter mutation status. Individual study-specific odds ratios (ORs) and 95% confidence intervals (CIs) were calculated, as were Mantel-Haenszel pooled odds ratios for the combined studies.

RESULTS

Eight eligible trials involved 2035 patients were included in the analysis. The average prevalence of the TERT promoter mutation was 10·32%. Compared with the wild-type TERT promoter gene, the TERT promoter mutation was associated with male gender, lymph node metastasis, extrathyroidal extension, distant metastasis, advanced TNM stage III/IV, poor clinical outcome (persistence or recurrence) and mortality. The associations were generally consistent across the different study populations.

CONCLUSIONS

Thus, our findings from this large meta-analysis definitively demonstrate that TERT promoter mutation-positive PTC is more likely to manifest with aggressive clinicopathological characteristics. In appropriate clinical settings, testing for the TERT promoter mutation is likely to be useful in assisting the risk stratification and management of PTC.

Cancer-Specific Telomerase Reverse Transcriptase (TERT) Promoter Mutations: Biological and Clinical Implications

The accumulated evidence has pointed to a key role of telomerase in carcinogenesis. As a RNA-dependent DNA polymerase, telomerase synthesizes telomeric DNA at the end of linear chromosomes, and attenuates or prevents telomere erosion associated with cell divisions. By lengthening telomeres, telomerase extends cellular life-span or even induces immortalization. Consistent with its functional activity, telomerase is silent in most human normal somatic cells while active only in germ-line, stem and other highly proliferative cells. In contrast, telomerase activation widely occurs in human cancer and the enzymatic activity is detectable in up to 90% of malignancies. Recently, hotspot point mutations in the regulatory region of the telomerase reverse transcriptase (TERT) gene, encoding the core catalytic component of telomerase, was identified as a novel mechanism to activate telomerase in cancer. This review discusses the cancer-specific TERT promoter mutations and potential biological and clinical significances.

Prognostic Significance of TERT Promoter Mutations in Papillary Thyroid Carcinomas in a BRAF(V600E) Mutation-Prevalent Population

BACKGROUND

The role of telomerase reverse transcriptase (TERT) promoter mutations in differentiated thyroid cancer has been well established. These mutations have a significantly higher prevalence in aggressive thyroid tumors, including widely invasive oncocytic carcinomas, poorly differentiated carcinomas, and anaplastic thyroid carcinomas. Interestingly, in some studies, TERT mutations were found to be more common in tumors with a BRAF(V600E) mutation. However, mutational analysis of TERT promoter mutations in thyroid tumors has not been previously performed for patients in Korea, where the BRAF(V600E) mutation in papillary thyroid carcinoma (PTC) is particularly prevalent. This study analyzed TERT promoter mutations in various thyroid tumors and examined their relationship with clinicopathologic factors and the BRAF(V600E) mutation in PTC cases.

METHODS

Using 242 preoperative fine-needle aspiration biopsy specimens (including 207 PTCs) with confirmed histopathological diagnosis of the biopsied thyroid nodules, the TERT promoter status (C228T and C250T) was analyzed, and the relationship with clinicopathologic factors and the BRAF(V600E) mutation in PTC cases was examined.

RESULTS

Of 242 patients, 14.5% (30/207), 26.7% (4/15), 50% (1/2), and 60% (2/5) of PTCs, follicular thyroid carcinomas, poorly differentiated carcinomas, and anaplastic thyroid carcinomas harbored a TERT(C228T) mutation, respectively. The TERT(C228T) mutation was associated with recurrence (p = 0.03). However, no association with other clinicopathologic factors in PTC was found. Coexistence of TERT(C228T) and BRAF(V600E) mutations was found in 13.0% of PTCs and was significantly associated with older age and advanced stage compared with the group negative for either mutation. The TERT(C228T) mutation status was an independent prognostic factor for recurrence-free survival (hazard ratio = 3.08 [confidence interval 1.042-9.079]; p = 0.042) in patients with PTC in multivariate analysis.

CONCLUSIONS

Identification of TERT promoter mutations in preoperative fine-needle aspiration biopsy specimens may help in better characterizing the prognosis and triaging thyroid cancer patients for appropriate treatment.

Classic Architecture with Multicentricity and Local Recurrence, and Absence of TERT Promoter Mutations are Correlates of BRAF (V600E) Harboring Pediatric Papillary Thyroid Carcinomas

This study is aimed to investigate the BRAF (V600E) and TERT promoter mutation profile of 50 pediatric papillary thyroid carcinomas (PTCs) to refine their clinicopathological correlates. The median age at the time of surgery was 16 years (range, 6-18). No TERT promoter mutations were identified in this series. The BRAF (V600E) mutation was present in 15 (30 %) tumors. From genotype-histologic variant correlation perspective, 13 of 24 classic variant PTCs and 2 of 7 diffuse sclerosing variant PTCs were found to harbor BRAF (V600E) mutation. One cribriform-morular variant, 3 solid variant, and 15 follicular variant PTCs were BRAF wild type. While tumors with distant metastasis were BRAF wild type, two of five tumors with extrathyroidal extension (ETE) harbored BRAF (V600E) mutation. Nine of 15 BRAF (V600E) harboring tumors had central lymph node metastases. There was no significant correlation with BRAF (V600E) mutation and age, gender, tumor size, ETE, central lymph node metastasis, the status of pT, pN1a-b, and distant metastasis. An adverse correlation between BRAF (V600E) mutation and disease-free survival (DFS) was noted in the entire cohort; however, the predictive value of BRAF (V600E) mutation disappeared within the group of tumors displaying classic architecture as well as classic variant PTCs. The present cohort identifies that the classic architecture with multicentricity and local recurrence are correlates of BRAF (V600E) harboring pediatric PTCs. While the small size of this cohort is one of the limitations, neither the BRAF mutation status nor the classic tumor architecture does seem to be an independent prognosticator of DFS in this series. Evidence also suggests that TERT promoter mutations do not seem to play a major role in the pathogenesis of pediatric PTCs.

TERT Core Promotor Mutations in Early-Onset Bladder Cancer

Activating mutations in the core promoter of the TERT gene have been described in many different tumor entities. In vitro models showed a two- to fourfold increase in transcriptional activity of the TERT promoter through creation of a consensus binding motif for Ets/TCF transcription factors caused by these mutations. TERT core promoter mutations are the most common mutations in bladder cancer with a frequency between 55.6% and 82.8% described so far, and are independent of stage and grade. Since limited data on molecular alterations of early-onset bladder tumors exists, we assessed the frequency of TERT core promoter mutations in early-onset bladder cancer. Two cohorts of bladder tumors (early-onset patient group; n=144 (age of onset of disease ≤45 years); unselected, consecutive group; n=125) were examined for TERT core promoter mutations. After microdissection and extraction of DNA the corresponding hotspot regions in the TERT core promoter were examined by Sanger-sequencing or a SNaPshot approach. A significantly lower frequency of TERT core promoter mutations was found in tumors from the early-onset cohort compared to the consecutive cohort (57.6% vs. 84.8%, p<0.001). Among the early-onset cohort cases younger than the cohort's median age of 39 years at disease onset showed a significantly reduced number of TERT promoter mutations (31/67, 46,3%) than cases aged between 39 and 45 years (52/77, 67.5%; p=0.012). This association was not found in the consecutive cases. Mutation status was independent of tumor stage and grade. We conclude that in tumors from early-onset bladder cancer patients TERT core promoter mutations are not as frequent as in bladder tumors from consecutive cases, but seem to play an important role there as well. In patients below 39 years of age TERT core promoter mutations are a more infrequent event, suggesting different mechanisms of tumorigenesis in these young patients.

[Telomerase reverse transcriptase (TERT) promoter mutations in the tumors of human endocrine organs: Biological and prognostic value]

The analysis of the data available in the literature has shown that telomerase reverse transcriptase TERT promoter may serve as promising markers of malignancy, aggressive disease course, and poor prognosis for malignant tumors of endocrine organs. Considering the established association of mutations with tumors having a poor prognosis (high-grade and anaplastic carcinoma of the thyroid), it is reasonable to perform prognostic-value investigations in a group of low-grade thyroid carcinomas that may occasionally recur and may be resistant to radioactive iodine therapy, i.e. can demonstrate a poor course and prognosis. TERT promoter mutations may be a specific marker of the clinically aggressive forms of adrenocortical carcinoma, but the determination of its diagnostic value calls for additional investigations that will have the larger number cases and establish the association with clinical features and survival rates.

ENDOCRINE TUMOURS: Genetic predictors of thyroid cancer outcome

Genetic predictors of outcome are reviewed in the context of a disease--cancer--that can be (too) simplistically described as a 'successful, invasive clone of our own tissues'. Context has many faces that determine a thyroid cancer patient's outcome beyond the influence of genetic markers. There is also plenty of evidence on the prognostic meaning of the interplay between genetics and context/microenvironment factors (encapsulation, degree of invasion, staging, etc.). This review addresses only genetic alterations detected by molecular methods in surgically resected specimens, thus ruling out immunohistochemistry and (F)ISH, despite their crucial relevance as topographically oriented methods. For the sake of the discussion, well-differentiated carcinomas were divided into two main morphologic types: papillary carcinoma (classic and most variants) displaying BRAFV600E mutations and RET/papillary thyroid carcinoma rearrangements and the group of follicular patterned carcinomas that encompasses follicular carcinoma and the encapsulated form of follicular variant of papillary carcinoma, displaying RAS mutations and PAX8/PPARγ rearrangement. TERT promoter mutations have been recently described (and associated with distant metastases and reduced survival) in papillary and follicular carcinomas, as well as in poorly differentiated and undifferentiated carcinoma. TP53 mutations, previously thought to be restricted to less differentiated carcinomas, were also detected in papillary and follicular carcinoma and found to carry a guarded prognosis. Besides their putative importance for targeted therapies, the prognostic meaning of such mutations is discussed per se and in the setting of concurrent BRAF mutation.

Understanding TERT Promoter Mutations: A Common Path to Immortality

Telomerase (TERT) activation is a fundamental step in tumorigenesis. By maintaining telomere length, telomerase relieves a main barrier on cellular lifespan, enabling limitless proliferation driven by oncogenes. The recently discovered, highly recurrent mutations in the promoter of TERT are found in over 50 cancer types, and are the most common mutation in many cancers. Transcriptional activation of TERT, via promoter mutation or other mechanisms, is the rate-limiting step in production of active telomerase. Although TERT is expressed in stem cells, it is naturally silenced upon differentiation. Thus, the presence of TERT promoter mutations may shed light on whether a particular tumor arose from a stem cell or more differentiated cell type. It is becoming clear that TERT mutations occur early during cellular transformation, and activate the TERT promoter by recruiting transcription factors that do not normally regulate TERT gene expression. This review highlights the fundamental and widespread role of TERT promoter mutations in tumorigenesis, including recent progress on their mechanism of transcriptional activation. These somatic promoter mutations, along with germline variation in the TERT locus also appear to have significant value as biomarkers of patient outcome. Understanding the precise molecular mechanism of TERT activation by promoter mutation and germline variation may inspire novel cancer cell-specific targeted therapies for a large number of cancer patients.

Prognostic effects of TERT promoter mutations are enhanced by coexistence with BRAF or RAS mutations and strengthen the risk prediction by the ATA or TNM staging system in differentiated thyroid cancer patients

BACKGROUND

Recent reports suggest that mutations in the promoter of the gene encoding telomerase reverse transcriptase (TERT) affect thyroid cancer outcomes.

METHODS

In all, 551 patients with differentiated thyroid cancer (DTC) enrolled in this study. The median follow-up duration was 4.8 years (interquartile range, 3.4-10.6 years).

RESULTS

TERT promoter mutations were detected in 25 DTCs (4.5%): 2.8% in neither BRAF-mutated nor RAS-mutated tumors, 4.8% in BRAF-mutated tumors, and 11.3% in RAS-mutated tumors. Moreover, they were frequently observed in American Thyroid Association (ATA) high-risk and TNM stage III/IV groups (9.1% and 12.9%, respectively). The coexistence of BRAF or RAS with TERT promoter mutations increased aggressive clinicopathologic features, recurrence (hazard ratio [HR] for BRAF, 4.64; 95% confidence interval [CI], 1.42-15.18; HR for RAS, 5.36; 95% CI, 1.20-24.02), and mortality (HR for BRAF, 15.13; 95% CI, 1.55-148.23; HR for RAS, 14.75; 95% CI, 1.30-167.00), even after adjustments for the age at diagnosis and sex, although the significance was lost after additional adjustments for pathologic characteristics. Furthermore, TERT promoter mutations significantly increased the risk of both recurrence and mortality in the ATA high-risk (HR for recurrence, 5.79; 95% CI, 2.07-16.18; HR for mortality, 16.16; 95% CI, 2.10-124.15) and TNM stage III/IV groups (HR for recurrence, 3.60; 95% CI, 1.19-10.85; HR for mortality, 9.06; 95% CI, 2.09-39.26).

CONCLUSIONS

The coexistence of BRAF or RAS mutations enhanced the prognostic effects of TERT promoter mutations. Furthermore, TERT promoter mutations strengthened the predictions of mortality and recurrence by the ATA and TNM staging systems, particularly for high-risk patients with DTC. Cancer 2016;122:1370-1379. © 2016 American Cancer Society.

TERT promoter mutations in thyroid cancer

The 2013 discovery of Telomerase reverse transcriptase (TERT) promoter mutations chr5, 1,295,228 C>T (C228T) and 1,295,250 C>T (C250T) in thyroid cancer represents an important event in the thyroid cancer field and much progress has occurred since then. This article provides a comprehensive review of this exciting new thyroid cancer field. The oncogenic role of TERT promoter mutations involves their creation of consensus binding sites for E-twenty-six transcriptional factors. TERT C228T is far more common than TERT C250T and their collective prevalence is, on average, 0, 11.3, 17.1, 43.2 and 40.1% in benign thyroid tumors, papillary thyroid cancer (PTC), follicular thyroid cancer, poorly differentiated thyroid cancer and anaplastic thyroid cancer, respectively, displaying an association with aggressive types of thyroid cancer. TERT promoter mutations are associated with aggressive thyroid tumor characteristics, tumor recurrence and patient mortality as well as BRAF V600E mutation. Coexisting BRAF V600E and TERT promoter mutations have a robust synergistic impact on the aggressiveness of PTC, including a sharply increased tumor recurrence and patient mortality, while either mutation alone has a modest impact. Thus, TERT with promoter mutations represents a prominent new oncogene in thyroid cancer and the mutations are promising new diagnostic and prognostic genetic markers for thyroid cancer, which, in combination with BRAF V600E mutation or other genetic markers (e.g. RAS mutations), are proving to be clinically useful for the management of thyroid cancer. Future studies will specifically define such clinical utilities, elucidate the biological mechanisms and explore the potential as therapeutic targets of TERT promoter mutations in thyroid cancer.

TERT Promoter Mutations in Thyroid Cancer

Two mutations (C228T and C250T) in the promoter region of the telomerase reverse transcriptase (TERT) have recently been described in different types of cancer including follicular cell-derived thyroid cancer (TC). In this paper, we reviewed the rates of these mutations in different types and subtypes of TC, their association with a number of clinical and histopathological features and outcome of TC, and their potential diagnostic and prognostic roles in TC. The overall rate of these mutations in TC is about 14 % with least prevalence in the well-differentiated subtypes of papillary thyroid cancer (10-13 %). Their rates increase significantly with increasing aggressiveness of TC reaching about 40 % in the undifferentiated and anaplastic thyroid cancers. There is also clear association with increasing age of patients at the time of diagnosis of TC. The evidence is compelling but with some conflicting results for associations between TERT promoter mutations and tumor size, extrathyroidal invasion, distant metastases, high tumor TNM stage, BRAF (V600E) mutation, recurrence, and mortality. A couple of studies reported a potential diagnostic role for TERT promoter mutations in thyroid nodules with indeterminate cytology of fine needle aspiration biopsy. These studies showed 100 % specificity but very low sensitivity of 7-10 %. The sensitivity increases significantly when TERT promoter mutation testing is combined with other gene mutations, particularly BRAF (V600E) and RAS mutations. Although TERT promoter mutations seem to play significant roles in the pathogenesis of TC, the mechanisms by which they contribute to carcinogenesis remain elusive and future work is needed to fully assess the roles, interactions, and impact of these mutations on the pathogenesis, diagnosis, prognosis, and therapeutics of TC.

Genomic and transcriptomic hallmarks of poorly differentiated and anaplastic thyroid cancers

BACKGROUND

Poorly differentiated thyroid cancer (PDTC) and anaplastic thyroid cancer (ATC) are rare and frequently lethal tumors that so far have not been subjected to comprehensive genetic characterization.

METHODS

We performed next-generation sequencing of 341 cancer genes from 117 patient-derived PDTCs and ATCs and analyzed the transcriptome of a representative subset of 37 tumors. Results were analyzed in the context of The Cancer Genome Atlas study (TCGA study) of papillary thyroid cancers (PTC).

RESULTS

Compared to PDTCs, ATCs had a greater mutation burden, including a higher frequency of mutations in TP53, TERT promoter, PI3K/AKT/mTOR pathway effectors, SWI/SNF subunits, and histone methyltransferases. BRAF and RAS were the predominant drivers and dictated distinct tropism for nodal versus distant metastases in PDTC. RAS and BRAF sharply distinguished between PDTCs defined by the Turin (PDTC-Turin) versus MSKCC (PDTC-MSK) criteria, respectively. Mutations of EIF1AX, a component of the translational preinitiation complex, were markedly enriched in PDTCs and ATCs and had a striking pattern of co-occurrence with RAS mutations. While TERT promoter mutations were rare and subclonal in PTCs, they were clonal and highly prevalent in advanced cancers. Application of the TCGA-derived BRAF-RAS score (a measure of MAPK transcriptional output) revealed a preserved relationship with BRAF/RAS mutation in PDTCs, whereas ATCs were BRAF-like irrespective of driver mutation.

CONCLUSIONS

These data support a model of tumorigenesis whereby PDTCs and ATCs arise from well-differentiated tumors through the accumulation of key additional genetic abnormalities, many of which have prognostic and possible therapeutic relevance. The widespread genomic disruptions in ATC compared with PDTC underscore their greater virulence and higher mortality.

FUNDING

This work was supported in part by NIH grants CA50706, CA72597, P50-CA72012, P30-CA008748, and 5T32-CA160001; the Lefkovsky Family Foundation; the Society of Memorial Sloan Kettering; the Byrne fund; and Cycle for Survival.