Catching the Silent Culprits: TERT Promoter Mutation Screening of Minimally Invasive Follicular and Oncocytic Thyroid Carcinoma in Clinical Practice.

De-escalation of thyroid cancer treatment is crucial to prevent overtreatment of indolent disease, but it remains important to identify clinically aggressive cases. TERT promoter mutations are molecular events frequently associated with high-risk thyroid tumors with poor outcomes and may identify cases at risk of dissemination. In various international guidelines, small minimally invasive follicular thyroid carcinoma and oncocytic thyroid carcinoma (miFTC/miOTC) are classified as low-risk lesions and are not recommended adjuvant treatment. Our study aimed to explore the association between size-based risk assessment and TERT promoter mutations. Between 2019 and May 2024, 84 miFTCs/miOTCs diagnosed at our department underwent digital droplet PCR analysis targeting TERT promoter mutational hotspots C228T and C250T in clinical routine. TERT promoter mutations were found in 10 out of 84 cases (11.9%). Mutated cases were pT1 (n = 1), pT2 (n = 3), or pT3 (n = 6). Patients with mutated tumors were older compared to patients with wild-type tumors (median age of 71 years vs. 57 years, p = 0.041). There were no significant differences regarding patient sex, tumor size, Ki-67 labeling index, or the presence of distant metastases. Notably, 30% of mutations displayed variant allele frequencies < 10%, possibly suggesting subclonal events. To conclude, TERT promoter mutations in miFTCs and miOTCs were associated with higher patient age and were often suspected to be subclonal. However, they did not affect clinical outcomes, possibly due to short follow-up. Reflex testing for this genetic alteration in miFTCs and miOTCs could be justified regardless of tumor size, though the clinical benefit remains uncertain.

BRAF-induced EHF expression affects TERT in aggressive papillary thyroid cancer.

CONTEXT: BRAFV600E and TERT promoter mutations in papillary thyroid carcinoma (PTC) have a synergistic effect on prognosis. This effect is believed to arise from MAPK activation triggered by BRAFV600E, leading to the upregulation of ETS transcription factors that bind to the mutant TERT promoter. OBJECTIVE: To explore the role of ETS factors in relation to clinical features, BRAFV600E and TERT promoter mutations in PTC. DESIGN: Transcriptomic data for 28 ETS factors were analyzed in the PTC cohort of The Cancer Genome Atlas (TCGA, n=399) and subsequently validated in a local cohort (n=93). In vitro experiments were performed to investigate the regulatory role in relation to BRAFV600E and TERT expression. RESULTS: TCGA identified ETS1, ERG, FLI1, GABPA, EHF, ETV6 and SPDEF as differentially expressed genes between stages I+II and III+IV. In both cohorts, EHF was consistently associated with adverse clinical features, BRAFV600E and TERT promoter mutation/expression. Notably, in BRAFV600E mutated PTC, high EHF expression was associated with shorter disease-free survival. Cases harboring concurrent BRAFV600E, TERT promoter mutations and high EHF expression exhibited the shortest disease-free survival. In cells harboring concurrent BRAFV600E and TERT promoter mutation, over-expression of EHF significantly increased TERT expression while knockdown or pharmacological inhibition of BRAF significantly decreased both EHF and TERT expression. In addition, ChIP-qPCR analysis suggested a potential binding of EHF in TERT promoter mutant cells but not in TERT promoter wild-type cells. CONCLUSION: The ETS transcription factor EHF is associated with poor prognosis in PTC. This is potentially mediated by BRAF-induced upregulation of EHF which in turn increases TERT expression in TERT promoter mutated cells.

Genetic variants and down-regulation of CACNA1H in pheochromocytoma.

Pheochromocytoma (PCC) and abdominal paraganglioma (aPGL) (together abbreviated PPGL) frequently present with an underlying genetic event in a PPGL driver gene, and additional susceptibility genes are anticipated. Here, we re-analyzed whole-exome sequencing data for PCC patients and identified two patients with rare missense variants in the calcium voltage-gated channel subunit 1H gene (CACNA1H). CACNA1H variants were also found in the clinical setting in PCC patients using targeted sequencing and from analysis of The Cancer Genome Atlas database. In total, CACNA1H variants were found in six PCC cases. Three of these were constitutional, and two are known to have functional consequences on hormone production and gene expression in primary aldosteronism and aldosterone-producing adrenocortical adenoma. In general, PPGL exhibited reduced CACNA1H mRNA expression as compared to normal adrenal. Immunohistochemistry showed strong CACNA1H (CaV3.2) staining in adrenal medulla while PPGL typically had weak or negative staining. Reduced CACNA1H gene expression was especially pronounced in PCC compared to aPGL and in PPGL with cluster 2 kinase signaling phenotype. Furthermore, CACNA1H levels correlated with HIF1A and HIF2A. Moreover, TCGA data revealed a correlation between CACNA1H methylation density and gene expression. Expression of rCacna1h in PC12 cells induced differential protein expression profiles, determined by mass spectrometry, as well as a shift in the membrane potential where maximum calcium currents were observed, as determined by electrophysiology. The findings suggest the involvement of CACNA1H/CaV3.2 in pheochromocytoma development and establish a potential link between the etiology of adrenomedullary and adrenocortical tumor development.

Atrophic changes in thyroid tumors are strong indicators of underlying DICER1 mutations: a bi-institutional genotype-phenotype correlation study.

Somatic and biallelic DICER1 mutations are reported in subsets of thyroid tumors, supporting the role of this gene in thyroid tumor development. As recent studies have brought attention to macrofollicular patterns, atrophic changes, and papillary structures as being associated with DICER1 mutations, we sought to explore these observations in a bi-institutional cohort. A total of 61 thyroid lesions (54 tumors and 7 cases of thyroid follicular nodular disease; TFND), including 26 DICER1 mutated and 35 DICER1 wildtype controls were subjected to histological re-investigation and clinical follow-up. DICER1-mutated lesions showed a statistically significant association with younger age at surgery (29.2 ± 12.5 versus 51.3 ± 18.8, p = 0.0001), a predominant macrofollicular growth pattern (20/26 mutated cases versus 18/35 wildtype; p = 0.01) and atrophic changes (20/26 mutated cases versus 2/35 wildtype; p = 0.0001). Similar results were obtained when excluding TFND cases. We also present clinical and histological triaging criteria for DICER1 sequencing of thyroid lesions, which led to the identification of DICER1 variants in 16 out of 26 cases (62%) when followed. Among these, 3 out of 12 cases with available data were found to carry a constitutional DICER1 mutation. This observation suggests that the majority of DICER1 mutations are somatic-however implies that sequencing of constitutional tissues could be clinically motivated. We conclude that DICER1 mutations are amassed in younger patients with macrofollicular-patterned tumors and, most strikingly, atrophic changes. Given the rate of constitutional involvement, our findings could be of clinical value, allowing the pathologist to triage cases for genetic testing based on histological findings.

Ca2+-activated K+ channels modulate membrane potential in the human parathyroid cell: Possible role in exocytosis.

The relationships between parathyroid hormone (PTH) secretion and parathyroid cell membrane potential, including the identities and roles of K+ channels that regulate and/or modulate membrane potential are not well defined. Here we have used Western blot/immunohistochemistry as well as patch-clamp and perifusion techniques to identify and localize specific K+ channels in parathyroid cells and to investigate their roles in the control of membrane potential and PTH secretion. We also re-investigated the relationship between membrane potential and exocytosis. We showed that in single human parathyroid cells K+ current is dependent on at least two types of Ca2+-activated K+ channels: a small-conductance Ca2+-activated K+ channel (KSK) and a large-conductance voltage and Ca2+-activated K+ channel (KBK). These channels were sensitive to specific peptide blocking toxins including apamin, charybdotoxin, and iberiotoxin. These channels confer sensitivity of the membrane potential in single cells to high extracellular K+, TEA, and peptide toxins. Blocking of KBK potently inhibited K+ channel current, and KBK was shown to be expressed in the plasma membrane of parathyroid cells. In addition, when using the capacitance technique as an indicator of exocytosis, clamping the parathyroid cell at -60 mV prevented exocytosis, whereas holding the membrane potential at 0 mV facilitated it. Taken together, the results show that human parathyroid cells have functional KBK and KSK channels but the data presented herein suggest that KBK/KSK channels likely contribute to the maintenance of the membrane potential, and that membrane potential, per se, modulates exocytosis independently of [Ca2+]i.

5hmC Immunohistochemistry: A Predictor of TERT Promoter Mutational Status in Follicular Thyroid Carcinoma?

Telomerase reverse transcriptase (TERT) gene aberrancies correlate to adverse prognosis in follicular thyroid carcinoma (FTC). As loss of 5-hydroxymethylcytosine (5hmC) has been associated with TERT promoter mutations in papillary thyroid carcinoma, this study sought to analyze the levels of 5hmC in a cohort of follicular thyroid tumors with available TERT data. A total of 29 tumors (26 FTCs, 2 follicular thyroid tumors of uncertain malignant potential, and 1 oncocytic thyroid carcinoma) with known TERT promoter mutational status and TERT gene expression were assessed for 5hmC immunoreactivity using two antibodies (clones RM236 and 4D9.) Slides were analyzed using a semiquantitative scoring system. Of the 10 tumor cases with aberrant TERT, only 1 scored negative with both antibodies (1/10; 10%), whereas the remaining 9 cases (9/10; 90%) exhibited some positivity for at least one antibody. Of the 19 TERT wild-type tumors, no case was scored negative using RM236, and 2 cases (2/19; 11%) using 4D9. The differences between TERT promoter mutated and wild-type groups were non-significant. The sensitivity and specificity for 5hmC immunohistochemistry (IHC) to detect mutated cases were 10% and 100% (RM236) and 20% and 89% (4D9). Therefore, 5hmC IHC is not a sensitive marker for detecting TERT promoter mutations in follicular thyroid tumors.

Digital droplet PCR TERT promoter mutational screening in fine needle aspiration cytology of thyroid lesions: A highly specific technique for pre-operative identification of high-risk cases.

BACKGROUND: Despite the advent of comprehensive molecular testing in surgical pathology, most centers still rely on the morphological assessment of fine-needle aspiration cytology (FNAC) to triage patients with thyroid nodules for surgery. Subsets of patients could benefit from the inclusion of molecular testing to increase the diagnostic and/or prognostic properties of the cytology analysis, including the assessment of TERT promoter mutations, an event coupled with thyroid malignancy, and poor prognosis. METHODS: In this prospective study, preoperative FNAC material from 65 cases was assessed for TERT promoter hotspot mutations C228T and C250T using the digital droplet PCR (ddPCR) technique on frozen pellets and re-evaluated postoperatively. RESULTS: Our cohort consisted of 15 B-III (23%), 26 B-IV (40%), 1 B-V (2%), and 23 (35%) B-VI lesions according to the Bethesda System for Reporting Thyroid Cytopathology. TERT promoter mutations were detected in 7 cases; 4 papillary thyroid carcinomas (all with preoperative B-VI status), two follicular thyroid carcinomas (one B-IV and one B-V status), and one poorly differentiated thyroid carcinoma (with B-VI status). All mutated cases were verified by mutational analysis of tumor tissue derived from postoperative formalin-fixed paraffin-embedded tissue, while all cases identified as wild-type on FNAC remained wild-type postoperatively. Moreover, the occurrence of a TERT promoter mutation was significantly associated with malignant disease and higher Ki-67 proliferation indices. CONCLUSION: In the present cohort, we found that ddPCR is a highly specific method for detecting high-risk TERT promoter mutations on thyroid FNAC material that could guide different surgical approaches in subsets of indeterminate lesions if reproduced in larger materials.

Thyroglobulin expression, Ki-67 index, and lymph node ratio in the prognostic assessment of papillary thyroid cancer.

The clinical significance of thyroglobulin (Tg) expression in papillary thyroid cancer (PTC) has not been systematically explored in relation to the Ki-67 index, lymph node ratio (LNR), or other conventional prognostic predictors. In this retrospective study of 327 patients with PTC, we investigated the immunohistochemical expression of Tg in both primary tumors and their matching lymph node metastases in relation to the Ki-67 index, LNR, and clinical data. Tumoral Tg immunoreactivity was inversely correlated to the Ki-67 index and tumor recurrence. The Ki-67 index was higher in lymph node metastases (mean 4%) than in the primary tumors (mean 3%). Reduced Tg expression, estimated as 0-25% Tg positive tumor cells, was more common in lymph node metastases compared to primary tumors. In addition to advanced metastatic burden (defined as N1b stage and LNR ≥ 21%), low Tg expression (0-25% positive tumor cells) in lymph node metastases had a significant prognostic impact with shorter recurrence-free survival. These findings support the potential value of histopathological assessment of Tg expression and Ki-67 index in lymph node metastases as complementary predictors to anticipate the prognosis of PTC patients better.

TOP2A Expression in Pheochromocytoma and Abdominal Paraganglioma: a Marker of Poor Clinical Outcome?

Pheochromocytoma and abdominal paraganglioma (PPGL) are rare neuroendocrine tumors originating from chromaffin cells. Even though only 10-15% of the tumors metastasize, all PPGLs are considered potentially malignant. Topoisomerase 2A (TOP2A) is a protein involved in cell proliferation and has been found to be over-expressed in metastatic PPGL. To provide support whether TOP2A could serve as a prognostic marker, 88 PPGLs (of which 8 metastatic/relapsing) and 10 normal adrenal gland samples were assessed for TOP2A mRNA expression using quantitative real-time PCR (qRT-PCR) and TOP2A immunohistochemistry. Comparisons to clinical parameters connected to metastatic behavior were made, and The Cancer Genome Atlas was used for validation of the results. A significant association between high TOP2A mRNA expression in primary PPGL and subsequent metastatic events (p = 0.008) was found, as well as to specific histological features and clinical parameters connected to metastatic behavior and mutations in SDHB. TOP2A immunoreactivity was calculated as an index of positive nuclei divided by the total amount of nuclei, and this index associated with TOP2A mRNA levels (p = 0.023) as well as the Ki-67 labeling index (p = 0.001). To conclude, TOP2A is a potential prognostic marker as it is frequently elevated in PPGL displaying subsequent metastatic disease, and future studies in larger cohorts are warranted to determine if a TOP2A index as assessed by immunohistochemistry could be a marker of poor outcome. Additionally, elevated levels of TOP2A could indicate a potential actionable event, and future studies with topoisomerase inhibitors would be of interest.

Altered expression of the IGF2­H19 locus and mitochondrial respiratory complexes in adrenocortical carcinoma.

Abnormalities of the insulin­like growth factor 2 (IGF2)­H19 locus with the overexpression of IGF2 are frequent findings in adrenocortical carcinoma (ACC). The present study assessed the expression of RNAs and microRNAs (miRNAs/miRs) from the IGF2­H19 locus using PCR­based methods in ACC and adrenocortical adenoma (ACA). The results were associated with proteomics data. IGF2 was overexpressed in ACC, and its expression correlated with that of miR­483­3p and miR­483­5p hosted by IGF2. The downregulated expression of H19 in ACC compared to ACA correlated with miR­675 expression hosted by H19. Several proteins exhibited an inverse correlation in expression and were predicted as targets of miR­483­3p, miR­483­5p or miR­675. Subsets of these proteins were differentially expressed between ACC and ACA. These included several proteins involved in mitochondrial metabolism. Among the mitochondrial respiratory complexes, complex I and IV were significantly decreased in ACC compared to ACA. The protein expression of NADH:ubiquinone oxidoreductase subunit C1 (NDUFC1), a subunit of mitochondrial respiratory complex I, was further validated as being lower in ACC compared to ACA and normal adrenals. The silencing of miR­483­5p increased NDUFC1 protein expression and reduced both oxygen consumption and glycolysis rates. On the whole, the findings of the present study reveal the dysregulation of the IGF2­H19 locus and mitochondrial respiration in ACC. These findings may provide a basis for the further understanding of the pathogenesis of ACC and may have potential values for diagnostics and treatment.

Presentation, Management, and Outcomes of Urinary Bladder Paraganglioma: Results From a Multicenter Study.

CONTEXT: Urinary bladder paraganglioma (UBPGL) is rare. OBJECTIVE: We aimed to characterize the presentation and outcomes of patients diagnosed with UBPGL. METHODS: We conducted a multicenter study of consecutive patients with pathologically confirmed UBPGL evaluated between 1971 and 2021. Outcomes included repeat bladder surgery, metastases, and disease-specific mortality. RESULTS: Patients (n=110 total; n=56 [51%] women) were diagnosed with UBPGL at a median age of 50 years (interquartile range [IQR], 36-61 years). Median tumor size was 2 cm (IQR, 1-4 cm). UBPGL was diagnosed prior to biopsy in only 37 (34%), and only 69 (63%) patients had evaluation for catecholamine excess. In addition to the initial bladder surgery, 26 (25%) required multiple therapies, including repeat surgery in 10 (9%). Synchronous metastases were present in 9 (8%) patients, and 24 (22%) other patients with UBPGL developed metachronous metastases at a median of 4 years (IQR, 2-10 years) after the initial diagnosis. Development of metachronous metastases was associated with younger age (hazard ratio [HR] 0.97; 95% CI, 0.94-0.99), UBPGL size (HR 1.69; 95% CI, 1.31-2.17), and a higher degree of catecholamine excess (HR 5.48; 95% CI, 1.40-21.39). Disease-specific mortality was higher in patients with synchronous metastases (HR 20.80; 95% CI, 1.30-332.91). Choice of initial surgery, genetic association, sex, or presence of muscular involvement on pathology were not associated with development of metastases or mortality. CONCLUSIONS: Only a minority of patients were diagnosed before biopsy/surgery, reflecting need for better diagnostic strategies. All patients with UBPGL should have lifelong monitoring for development of recurrence and metastases.

Impaired oxygen-sensitive regulation of mitochondrial biogenesis within the von Hippel-Lindau syndrome.

Mitochondria are the main consumers of oxygen within the cell. How mitochondria sense oxygen levels remains unknown. Here we show an oxygen-sensitive regulation of TFAM, an activator of mitochondrial transcription and replication, whose alteration is linked to tumours arising in the von Hippel-Lindau syndrome. TFAM is hydroxylated by EGLN3 and subsequently bound by the von Hippel-Lindau tumour-suppressor protein, which stabilizes TFAM by preventing mitochondrial proteolysis. Cells lacking wild-type VHL or in which EGLN3 is inactivated have reduced mitochondrial mass. Tumorigenic VHL variants leading to different clinical manifestations fail to bind hydroxylated TFAM. In contrast, cells harbouring the Chuvash polycythaemia VHLR200W mutation, involved in hypoxia-sensing disorders without tumour development, are capable of binding hydroxylated TFAM. Accordingly, VHL-related tumours, such as pheochromocytoma and renal cell carcinoma cells, display low mitochondrial content, suggesting that impaired mitochondrial biogenesis is linked to VHL tumorigenesis. Finally, inhibiting proteolysis by targeting LONP1 increases mitochondrial content in VHL-deficient cells and sensitizes therapy-resistant tumours to sorafenib treatment. Our results offer pharmacological avenues to sensitize therapy-resistant VHL tumours by focusing on the mitochondria.

Whole-Exome Sequencing of Germline Variants in Non-BRCA Families with Hereditary Breast Cancer.

Breast cancer is the most prevalent malignancy among women worldwide and hereditary breast cancer (HBC) accounts for about 5−10% of the cases. Today, the most recurrent genes known are BRCA1 and BRCA2, accounting for around 25% of familial cases. Although thousands of loss-of-function variants in more than twenty predisposing genes have been found, the majority of familial cases of HBC remain unexplained. The aim of this study was to identify new predisposing genes for HBC in three non-BRCA families with autosomal dominant inheritance pattern using whole-exome sequencing and functional prediction tools. No pathogenic variants in known hereditary cancer-related genes could explain the breast cancer susceptibility in these families. Among 2122 exonic variants with maximum minor allele frequency (MMAF) < 0.1%, between 17−35 variants with combined annotation-dependent depletion (CADD) > 20 segregated with disease in the three analyzed families. Selected candidate genes, i.e., UBASH3A, MYH13, UTP11L, and PAX7, were further evaluated using protein expression analysis but no alterations of cancer-related pathways were observed. In conclusion, identification of new high-risk cancer genes using whole-exome sequencing has been more challenging than initially anticipated, in spite of selected families with pronounced family history of breast cancer. A combination of low- and intermediate-genetic-risk variants may instead contribute the breast cancer susceptibility in these families.

Downregulation and Hypermethylation of GABPB1 Is Associated with Aggressive Thyroid Cancer Features.

Promoter mutations of the telomerase reverse transcriptase (TERT) gene occur frequently in thyroid carcinoma (TC), including papillary (PTC) and anaplastic subtypes (ATC). Given that the ETS family transcription factors GABPA and GABPB1 activate the mutant TERT promoter and induce TERT expression for telomerase activation, GABPB1 has been proposed as a cancer therapeutic target to inhibit telomerase. Here, we sought to determine the role of GABPB1 in TC pathogenesis. In TC-derived cells carrying the mutated TERT promoter, GABPB1 knockdown led to diminished TERT expression but significantly increased invasive potentials in vitro and metastatic potential in a xenograft zebrafish model and altered expression of markers for epithelial-to-mesenchymal transition. GABPB1 expression was downregulated in aggressive TCs. Low GABPB1 expression correlated with its promoter hypermethylation, which in turn was also associated with shorter disease-free survival. Consistently, DNA methylation inhibitors enhanced GABPB1 expression, as observed upon reduced promoter methylation. Our results suggest that GABPB1 is required for TERT expression and telomerase activation, but itself serves as a tumor suppressor to inhibit TC progression. Furthermore, aberrant DNA methylation leads to GABPB1 silencing, thereby promoting TC aggressiveness. Thus, caution is needed if targeting GABPB1 for cancer therapy is considered.

Prognostic Utility of the Ki-67 Labeling Index in Follicular Thyroid Tumors: a 20-Year Experience from a Tertiary Thyroid Center.

Follicular thyroid tumors pose a diagnostic challenge on the preoperative level, as the discrimination between follicular thyroid carcinoma (FTC) and adenoma (FTA) demands careful histopathological investigation. Moreover, prognostication of FTCs is mostly based on tumor size and extent of invasive properties, while immunohistochemical markers pinpointing high-risk cases are lacking. We have routinely established a Ki-67 labeling index for follicular thyroid tumors since 1999. To assess the potential value of Ki-67 as an adjunct tool to (1) correctly separate FTCs from FTAs and (2) help identify poor-prognosis FTCs, we collected histopathological and clinical data from 818 follicular thyroid tumors with a histological Ki-67 labeling index established in clinical routine practice (516 FTAs, 252 FTCs, and 50 follicular thyroid tumors of uncertain malignant potential (FT-UMPs)). The Ki-67 labeling index was higher in FTCs (mean 5.8%) than in FTAs (mean 2.6%) (P < 0.001), and a receiver operating characteristic curve analysis revealed a cut-off value of 4% to separate FTC from FTA with a sensitivity and specificity of 65% and 83%, respectively. Similarly, a Ki-67 labeling index above 4% was found to identify FTCs that later metastasized from clinically indolent FTCs with a sensitivity and specificity of 80% and 48%, respectively. Ki-67 constituted an independent predictor of future FTC metastases/recurrence and death of disease, and a value > 4% was a reliable prognostic marker within individual pT staging groups. We conclude that Ki-67 is a potentially valuable marker for the prognostication of FTCs, and future implementation in the histopathological assessments of follicular thyroid tumors could be beneficial if reproduced in international series.

Synergistic effects of telomerase reverse transcriptase and regulator of telomere elongation helicase 1 on aggressiveness and outcomes in adrenocortical carcinoma.

Adrenocortical carcinoma (ACC) is one of the deadliest endocrine malignancies and telomere maintenance by activated telomerase is critically required for ACC development and progression. Because telomerase reverse transcriptase (TERT) and regulator of telomere elongation helicase 1 (RTEL1) play key roles in telomere homeostasis, we determined their effect on ACC pathogenesis and outcomes. Analyses of TCGA and GEO datasets showed significantly higher expression of RTEL1 but not TERT in ACC tumors, compared to their benign or normal counterparts. Furthermore, gains/amplifications of both TERT and RTEL1 genes were widespread in ACC tumors and their expression correlated with their gene copy numbers. Higher expression of either TERT or RTEL1 was associated with shorter overall and progression-free survival (OS and PFS) in the TCGA ACC patient cohort, and higher levels of both TERT and RTEL1 mRNA predicted the shortest patient OS and PFS. However, multivariate analyses showed that only RTEL1 independently predicted patient OS and PFS. Gene set enrichment analysis further showed enrichments of wnt/ß-catenin, MYC, glycolysis, MTOR, and DNA repair signaling pathways in ACC tumors expressing high TERT and RTEL1 mRNA levels. Taken together, TERT and RTEL1 promote ACC aggressiveness synergistically and may serve as prognostic factors and therapeutic targets for ACC.

Merkel cell polyomavirus T-antigens regulate DICER1 mRNA stability and translation through HSC70.

Merkel cell carcinoma is an aggressive skin malignancy, mostly caused by Merkel cell polyomavirus (MCPyV). MCPyV T-antigens can induce mature microRNA expressions through the DnaJ domain, but its underlying mechanism is still unknown. Here, we report that the T-antigens induce protein expression and mRNA stability of DICER1, a key factor in microRNA biogenesis, through heat shock cognate 70 (HSC70). HSC70 directly interacts with the AU-rich elements (ARE) of DICER1 mRNA in both coding and 3' untranslated region in the presence of MCPyV T-antigen. The T-antigen/HSC70 interaction could induce luciferase activity of synthetic ARE-containing reporter, as well as the stability of ARE-containing mRNAs, suggesting a broader role of MCPyV T-antigens in regulating multiple mRNAs via HSC70. These findings highlight a new role for the interaction of HSC70 and MCPyV T-antigens in mRNA regulation and an undescribed regulatory mechanism of DICER1 mRNA stability and translation through its direct interaction with HSC70.

Imatinib Regulates miR-483-3p and Mitochondrial Respiratory Complexes in Gastrointestinal Stromal Tumors.

Metabolic adaptation to increased oxidative phosphorylation (OXPHOS) has been found in gastrointestinal stromal tumor (GIST) upon imatinib treatment. However, the underlying mechanism of imatinib-induced OXPHOS is unknown. Discovering molecules that mediate imatinib-induced OXPHOS may lead to the development of therapeutic strategies synergizing the efficacy of imatinib. In this study, we explored the role of microRNAs in regulating OXPHOS in GIST upon imatinib treatment. Using a microarray approach, we found that miR-483-3p was one of the most downregulated miRNAs in imatinib-treated tumors compared to untreated tumors. Using an extended series of GIST samples, we further validated the downregulation of miR-483-3p in imatinib-treated GIST samples by RT-qPCR. Using both gain- and loss-of-function experiments, we showed that miR-483-3p could regulate mitochondrial respiratory Complex II expression, suggesting its role in OXPHOS regulation. Functionally, miR-483-3p overexpression could rescue imatinib-induced cell death. These findings provide the molecular link for imatinib-induced OXPHOS expression and the biological role of miR-483-3p in regulating cell viability upon imatinib treatment.

Association between Predicted Effects of TP53 Missense Variants on Protein Conformation and Their Phenotypic Presentation as Li-Fraumeni Syndrome or Hereditary Breast Cancer.

Rare germline pathogenic TP53 missense variants often predispose to a wide spectrum of tumors characterized by Li-Fraumeni syndrome (LFS) but a subset of variants is also seen in families with exclusively hereditary breast cancer (HBC) outcomes. We have developed a logistic regression model with the aim of predicting LFS and HBC outcomes, based on the predicted effects of individual TP53 variants on aspects of protein conformation. A total of 48 missense variants either unique for LFS (n = 24) or exclusively reported in HBC (n = 24) were included. LFS-variants were over-represented in residues tending to be buried in the core of the tertiary structure of TP53 (p = 0.0014). The favored logistic regression model describes disease outcome in terms of explanatory variables related to the surface or buried status of residues as well as their propensity to contribute to protein compactness or protein-protein interactions. Reduced, internally validated models discriminated well between LFS and HBC (C-statistic = 0.78-0.84; equivalent to the area under the ROC (receiver operating characteristic) curve), had a low risk for over-fitting and were well calibrated in relation to the known outcome risk. In conclusion, this study presents a phenotypic prediction model of LFS and HBC risk for germline TP53 missense variants, in an attempt to provide a complementary tool for future decision making and clinical handling.