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Mediator complex subunit 16 is down-regulated in papillary thyroid cancer, leading to increased transforming growth factor-β signaling and radioiodine resistance.

ABSTRACT: Mediator complex subunit 16 (MED16) is a component of the mediator complex and functions as a coactivator in transcriptional events at almost all RNA polymerase II-dependent genes. In this study, we report that the expression of MED16 is markedly decreased in papillary thyroid cancer (PTC) tumors compared with normal thyroid tissues. In vitro, MED16 overexpression in PTC cells significantly inhibited cell migration, enhanced sodium/iodide symporter expression and iodine uptake, and decreased resistance to radioactive ¹³¹I (RAI). Conversely, PTC cells in which MED16 had been further knocked down (MED16^KD) exhibited enhanced cell migration, epithelial-mesenchymal transition, and RAI resistance, accompanied by decreased sodium/iodide symporter levels. Moreover, cell signaling through transforming growth factor β (TGF-β) was highly activated after the MED16 knockdown. Similar results were obtained in MED12^KD PTC cells, and a co-immunoprecipitation experiment verified interactions between MED16 and MED12 and between MED16 and TGF-βR2. Of note, the application of LY2157299, a potent inhibitor of TGF-β signaling, significantly attenuated MED16^KD-induced RAI resistance both in vitro and in vivo In conclusion, our findings indicate that MED16 reduction in PTC contributes to tumor progression and RAI resistance via the activation of the TGF-β pathway.

SUBMITTER: Gao H

PROVIDER: S-EPMC7397117 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundPapillary thyroid cancer (PTC) is the most frequent endocrine tumor. Radioiodine (RAI) treatment is highly effective in these tumors, but up to 60% of metastatic cases become RAI-refractory. Scanty data are available on either the molecular pattern of radioiodine refractory papillary thyroid cancers (PTC) or the mechanisms responsible for RAI resistance.MethodsWe analyzed the molecular profile and gene/miRNA expression in primary PTCs, synchronous and RAI-refractory lymph node metastases (LNMs) in correlation to RAI avidity or refractoriness. We classified patients as RAI+/D+ (RAI uptake/disease persistence), RAI-/D+ (absent RAI uptake/disease persistence), and RAI+/D- (RAI uptake/disease remission), and analyzed the molecular and gene/miRNA profiles, and the expression of thyroid differentiation (TD) related genes.ResultsA different molecular profile according to the RAI class was observed: BRAFV600E cases were more frequent in RAI-/D+ (P = 0.032), and fusion genes in RAI+/D+ cases. RAI+/D- patients were less frequently pTERT mutations positive, and more frequently wild type for the tested mutations/fusions. Expression profiles clearly distinguished PTC from normal thyroid. On the other hand, in refractory cases (RAI+/D+ and RAI-/D+) no distinctive PTC expression patterns were associated with either tissue type, or RAI uptake, but with the driving lesion and BRAF-/RAS-like subtype. Primary tumors and RAI-refractory LNMs with BRAFV600E mutation display transcriptome similarity suggesting that RAI minimally affects the expression profiles of RAI-refractory metastases. Molecular profiles associated with the expression of TPO, SLC26A4 and TD genes, that were found more downregulated in BRAFV600E than in gene fusions tumors.ConclusionsThe present data indicate a different molecular profile in RAI-avid and RAI-refractory metastatic PTCs. Moreover, BRAFV600E tumors displayed reduced differentiation and intrinsic RAI refractoriness, while PTCs with fusion oncogenes are RAI-avid but persistent, suggesting different oncogene-driven mechanisms leading to RAI refractoriness.

Project description:Radioactive iodine-refractory metastatic differentiated thyroid cancer (RAIR) is associated with a poor prognosis. Multikinase inhibitors have demonstrated improvement in progression-free but not overall survival in such patients, but usage is limited by significant adverse effects and the development of resistance. Clinical research has demonstrated improvement in progression-free survival with the combined use of the BRAF/MEK inhibitor in patients with metastatic melanoma and anaplastic thyroid cancer with the BRAFV600E mutation and has shown promise in redifferentiation of BRAF-positive RAIR differentiated thyroid cancer. A 58-year-old woman went to her primary care physician for a growing mass on the left side of her neck. CT imaging noted a 6 x 8 x 6 cm mixed cystic and solid mass and lymphadenopathy. Core biopsy subsequently showed metastatic papillary thyroid cancer (Stage III, PT4a/PN1b), and she underwent a total thyroidectomy with left neck dissection. She then received 204mCi 131I post-total thyroidectomy. Unfortunately, her thyroglobulin continued to increase post-radioactive iodine (RAI) treatment, indicating persistent and/or recurrent thyroid cancer. An RAI-131 whole-body scan on the thyrogen protocol showed no significant RAI uptake. A fluorodeoxyglucose (FDG)-positron emission tomography (PET) CT scan was then performed, which showed recurrent metastatic disease with hypermetabolism noted in the left thyroid bed and FDG-avid bilateral cervical lymph nodes and pulmonary nodules. Given these findings, her cancer was classified as radioactive iodine refractory (RAIR). Molecular testing indicated the BRAFV600E mutation. After a discussion with the patient, it was decided to initiate therapy with a BRAF inhibitor (dabrafenib 150 mg twice a day) and MEK inhibitor (trametinib 2 mg once a day) in an attempt to redifferentiate RAIR. Repeat RAI-131 thyrogen whole body scan one month after initiation of therapy demonstrated left level 2 cervical lymphadenopathy radioiodine uptake. The patient subsequently received 216 mCi 131I treatment given evidence of redifferentiation. Her post-treatment scan indicated additional uptake in a left lower lobe pulmonary nodule as well as a left paratracheal mass indicating successful RAI-131 uptake by metastases. Her thyroglobulin level, six months post-RAI, decreased to 4.0 indicating an encouraging response. Further surveillance, including imaging studies, is planned. This case illustrates the re-differential potential for dabrafenib and trametinib treatment in patients with BRAFV600E-mutated RAIR differentiated thyroid cancer. This therapy has been shown to be successful in small series of patients and could potentially be offered to RAIR patients with the BRAFV600E mutation as an alternative to multikinase treatment given its favorable side-effect profile.

Project description:The current recommendation for the use of adjuvant radioactive iodine (RAI) therapy in papillary thyroid cancer (PTC) after radical surgery is based on clinicopathological factors; however, this recommendation remains controversial. Our present study established a new biomarker, RPMB (promotor methylation burden of DNA repair genes (DRGs)), to identify a patient subgroup suitable for adjuvant RAI therapy. We defined RPMB as the ratio of methylated DRGs to the total number of DRGs. Methylation profiles of 498 PTC tumors and their clinical data were retrieved from the Cancer Genome Atlas (TCGA) database. DRGs of PTC subjects were found to be much more hypomethylated than controls across the whole profile (all p < 0.001). PTC patients with higher RPMBs tended to be ≥45 years old and female, and these PTCs were commonly unifocal, with N0 disease, wild-type BRAF, and mutated RAS. The subgroup analysis indicated that high RPMBs were significantly associated with poor disease-free survival (DFS) in male patients with PTC (HR = 4.855, 95% CI: 1.527–15.433, p = 0.007). Moreover, Kaplan–Meier analysis showed that high RPMBs could significantly predict poor DFS in male patients after R0 resection for N1 disease (HR: 5.431, 95% CI: 1.045–28.219, p = 0.024), and the p-value was very close to significance in these patients after adjuvant RAI therapy (HR: 6.269, 95% CI: 0.693–56.714, p = 0.062). Multivariate analysis indicated that both male sex (HR = 14.565, 95%CI: 2.153–98.507, p = 0.006) and high RPMBs (HR = 11.206, 95%CI: 1.622–77.405, p = 0.014) were independent unfavorable factors for DFS after adjuvant RAI therapy. Therefore, RPMB might be a potential predictor for identifying suitable male patients with PTC who can benefit from adjuvant RAI therapy. Highlights • We established a new biomarker named RPMB in an attempt to fulfill this mission.• A high RPMB was significantly associated with poor disease-free survival (DFS) in male PTC patients.• Kaplan-Meier analysis showed that high RPMBs could significantly predict poor DFS in male patients after R0 resection for N1 disease.• Both male sex and high RPMB were proven as independent unfavorable factors for DFS after adjuvant RAI therapy.• RPMB might be a potential predictor to identify suitable male PTC patients who can benefit from adjuvant RAI therapy. Papillary thyroid cancer; Adjuvant RAI therapy; Promotor methylation; Disease-free survival; Lymph node activation.

Project description:IntroductionThe radioiodine-refractory (RAI-R) recurrent papillary thyroid carcinomas (PTCs) are more frequent in elderly patients and have an unfavorable prognosis. Data on the prevalence and characteristics of RAI-R recurrent PTCs in patients of young and middle age with or without a history of radiation exposure in childhood are poorly described. The aim of the current study was: i) to determine the frequency of RAI-R recurrent PTCs among donors of the Chornobyl Tissue Bank (CTB) and analyze the clinicopathological features of primary tumors (PTs), primary metastases (PMTSs), recurrent metastases (RMTSs) and risk factors for RMTS, and ii) to determine the immune checkpoint status (ICS) of the RAI-R recurrent PTCs and to assess the factors associated with ICS positivity.MethodsSixty RAI-R recurrent PTCs (46 exposed to radiation and 14 non-exposed, 2.5% of all cases registered with the CTB) from the Ukrainian patients aged up to 48 years were identified.ResultsThe clinicopathological characteristics of the PTs moderately to weakly resembled those of the PMTS and RMTS from the same patients while the metastatic tissues were highly similar. The multivariate model of RMTS included the dominant solid-trabecular growth pattern of the PT, cystic changes, N1b metastases, and the probability of a causation (POC) of PTC by radiation as risk factors. Among these factors, the lateral PMTS (N1b) had the strongest effect. The longer period of latency (a POC component) was the second statistically significant characteristic. ICS percent agreement between the PT and RAI-R RMTS was 91.5%; 23.7% of PTs and 28.8% of RMTSs had positive ICS (positive PD-L1 tumor epithelial cells (TECs) and positive PD-L1/PD1 tumor-associated immune cells). ICS positivity of PTs was associated with pronounced oncocytic changes and high density of the p16INK4A-positive TECs in the invasive areas of PTs. In RMTSs, ICS positivity was associated with pronounced oncocytic changes and Ki-67 labeling index ≥ 4.5% of PTs, and the dominant solid-trabecular growth pattern, Ki-67 labeling index ≥ 7.6% and p16INK4A-positivity of RMTS.DiscussionThe findings are of clinical relevance and may be useful for developing individual treatment approaches for patients with RAI-R recurrent PTCs possibly involving immunotherapy.

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Mediator complex subunit 16 is down-regulated in papillary thyroid cancer, leading to increased transforming growth factor-β signaling and radioiodine resistance.

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