Redifferentiation of radioiodine-refractory thyroid cancers

Clinico-pathological factors associated with radioiodine refractory differentiated thyroid carcinoma status

PURPOSE

Risk factors for developing radioiodine refractory thyroid cancer (RAIR-TC) have rarely been analyzed. The purpose of the present study was to find clinical and pathological features associated with the occurrence of RAIR-disease in differentiated thyroid cancers (DTC) and to establish an effective predictive risk score.

METHODS

All cases of RAIR-DTC treated in our center from 1990 to 2020 were retrospectively reviewed. Each case was matched randomly with at least four RAI-avid DTC control patients based on histological and clinical criteria. Conditional logistic regression was used to examine the association between RAIR-disease and variables with univariate and multivariate analyses. A risk score was then developed from the multivariate conditional logistic regression model to predict the risk of refractory disease occurrence. The optimal cut-off value for predicting the occurrence of RAIR-TC was assessed by receiver operating characteristic (ROC) curves and Youden's statistic.

RESULTS

We analyzed 159 RAIR-TC cases for a total of 759 controls and found 7 independent risk factors for predicting RAIR-TC occurrence: age at diagnosis ≥ 55, vascular invasion, synchronous cervical, pulmonary and bone metastases at initial work-up, cervical and pulmonary recurrence during follow-up. The predictive score of RAIR-disease showed a high discrimination power with a cut-off value of 8.9 out of 10 providing 86% sensitivity and 92% specificity with an area under the curve (AUC) of 0.95.

CONCLUSION

Predicting the occurrence of RAIR-disease in DTC patients may allow clinicians to focus on systemic redifferentiating strategies and/or local treatments for metastatic lesions rather than pursuing with ineffective RAI-therapies.

Radioactive Iodine Therapy in Differentiated Thyroid Cancer: An Update on Dose Recommendations and Risk of Secondary Primary Malignancies

Radioactive iodine (RAI) therapy with iodine-131 is performed in select cases of differentiated thyroid cancer (DTC), typically for remnant ablation, adjuvant therapy, or treatment of known persistent disease. Herein, we review updated RAI dose recommendations and associated risks of secondary primary malignancy (SPM). RAI dose is usually chosen empirically based on the risk assessment of tumor recurrence and other factors. Dose recommendations differ slightly among relevant medical societies. As of April 2024, most medical societies, including the American Thyroid Association (ATA), European Thyroid Association (ETA), Society of Nuclear Medicine and Molecular Imaging/European Association of Nuclear Medicine (SNMMI/ EANM), and National Comprehensive Cancer Network (NCCN), recommend a dose of 1.11 GBq (30 mCi) I-131 for remnant ablation. For adjuvant therapy, the recommended RAI dose ranges from 1.11 to 3.7 GBq (30-100) mCi I-131, although doses up to 5.6 GBq (150 mCi) may also be considered. In patients with known or suspected metastatic disease, at least 3.7 GBq (100 mCi) I-131 should be administered, and RAI doses as high as 7.4 GBq (200 mCi) may be justified depending on the suspected tumor burden and extent. Dosimetry has the advantage of tailoring the RAI dose to each patient's pharmacokinetics, resulting in ≥ 7.4 GBq (200 mCi) of I-131 in most cases. There is an ongoing debate about the risk of developing SPM due to RAI therapy, with several multicenter studies and meta-analyses concerning SPM being published in the last 2 years. The incidence of RAI-associated SPM varies according to the study design and detection method. Several studies showed no increased incidence, and there was no specific secondary cancer or cancer group linked to RAI exposures. Some reports indicated that cumulative RAI doses exceeding 5.6-7.4 GBq (150-200 mCi) were found to represent an increased risk for developing SPM. However, a clearly defined dose threshold cannot be provided based on the current literature. Nonetheless, caution should be exercised when considering repeated RAI therapies for persistent metastatic PTC, with a cumulative dose exceeding 37.0 GBq (1,000 mCi), due to the potential risk of developing SPM and other long-term toxicity. Further research is warranted to understand better the relationship between RAI dose and the risk of SPM.

Genomic alterations in thyroid cancer: biological and clinical insights

Tumours can arise from thyroid follicular cells if they acquire driver mutations that constitutively activate the MAPK signalling pathway. In addition, a limited set of additional mutations in key genes drive tumour progression towards more aggressive and less differentiated disease. Unprecedented insights into thyroid tumour biology have come from the breadth of thyroid tumour sequencing data from patients and the wide range of mutation-specific mechanisms identified in experimental models, in combination with the genomic simplicity of thyroid cancers. This knowledge is gradually being translated into refined strategies to stratify, manage and treat patients with thyroid cancer. This Review summarizes the biological underpinnings of the genetic alterations involved in thyroid cancer initiation and progression. We also provide a rationale for and discuss specific examples of how to implement genomic information to inform both recommended and investigational approaches to improve thyroid cancer prognosis, redifferentiation strategies and targeted therapies.

Dual targeting of MAPK and PI3K pathways unlocks redifferentiation of Braf-mutated thyroid cancer organoids

Thyroid cancer is the most common endocrine malignancy and several genetic events have been described to promote the development of thyroid carcinogenesis. Besides the effects of specific mutations on thyroid cancer development, the molecular mechanisms controlling tumorigenesis, tumor behavior, and drug resistance are still largely unknown. Cancer organoids have been proposed as a powerful tool to study aspects related to tumor development and progression and appear promising to test individual responses to therapies. Here, using mESC-derived thyroid organoids, we developed a BrafV637E-inducible model able to recapitulate the features of papillary thyroid cancer in vitro. Overexpression of the murine BrafV637E mutation, equivalent to BrafV600E in humans, rapidly triggers to MAPK activation, cell dedifferentiation, and disruption of follicular organization. BrafV637E-expressing organoids show a transcriptomic signature for p53, focal adhesion, ECM-receptor interactions, EMT, and inflammatory signaling pathways. Finally, PTC-like thyroid organoids were used for drug screening assays. The combination of MAPK and PI3K inhibitors reversed BrafV637E oncogene-promoted cell dedifferentiation while restoring thyroid follicle organization and function in vitro. Our results demonstrate that pluripotent stem cells-derived thyroid cancer organoids can mimic tumor development and features while providing an efficient tool for testing novel targeted therapies.

Primary tumour iodine avidity in relation to uptake in persistent metastatic disease in papillary and poorly differentiated thyroid cancer

PURPOSE

Patients with persistent or recurrent papillary and poorly differentiated thyroid cancer can be effectively treated with radioiodine, if the tumour tissue is iodine-avid. However, iodine-avidity status is often unknown at the time of initial radioiodine treatment, limiting any adaptive approach. This study aimed to clarify the relationship between pre-therapeutic iodine avidity in primary tumour tissue, initial lymph node metastases and iodine uptake in subsequent metastases.

METHODS

Iodine avidity was prospectively assessed pre-therapeutically in 35 patients by injection of tracer amounts of iodine-131 two days prior to surgery. Iodine concentrations in resected tissue samples were measured, enabling accurate and histologically verifiable iodine avidity data for both primary tumour and initial lymph node metastases. Iodine uptake in persistent metastatic disease was assessed by review of radiology, and treatment response was examined through journal studies.

RESULTS

Out of data from 35 patients, 10 had persistent disease at presentation or during follow-up (range 19-46 months). Four patients had non-avid persistent metastatic disease, all with low iodine avidity in their primary tumours and initial lymph node metastases. Patients with low pre-therapeutic iodine avidity did not appear to have greater risk of persistent disease.

CONCLUSION

The results indicate a close link between pre-therapeutically measured iodine concentrations in primary tumours with iodine avidity of any subsequent metastases.

Add-on radioiodine during long-term BRAF/MEK inhibition in patients with RAI-refractory thyroid cancers: a reasonable option?

Dual modulation of the MAPK pathway with BRAF (e.g., dabrafenib) and MEK (e.g., trametinib) inhibitors has the potential to re-establish radioiodine (RAI) sensitivity in BRAF-mutated RAI-refractory (RAI-R)-differentiated thyroid carcinoma (DTC) cells. Here we showed that (1) double BRAF/MEK inhibition may still reach a significant redifferentiation in patients with a long-history RAI-R DTC and multiple previous treatments; (2) the addition of high RAI activities may obtain a significant structural response in such patients; and (3) a divergence between increasing thyroglobulin and structural response may be a reliable biomarker or redifferentiation. Accordingly, the add-on prescription of high activities of 131I should be considered in RAI-R patients under multikinase inhibitors with stable or responding structural disease and divergent increase of Tg levels.

Review article: new treatments for advanced differentiated thyroid cancers and potential mechanisms of drug resistance

The treatment of advanced, radioiodine refractory, differentiated thyroid cancers (RR-DTCs) has undergone major advancements in the last decade, causing a paradigm shift in the management and prognosis of these patients. Better understanding of the molecular drivers of tumorigenesis and access to next generation sequencing of tumors have led to the development and Food and Drug Administration (FDA)-approval of numerous targeted therapies for RR-DTCs, including antiangiogenic multikinase inhibitors, and more recently, fusion-specific kinase inhibitors such as RET inhibitors and NTRK inhibitors. BRAF + MEK inhibitors have also been approved for BRAF-mutated solid tumors and are routinely used in RR-DTCs in many centers. However, none of the currently available treatments are curative, and most patients will ultimately show progression. Current research efforts are therefore focused on identifying resistance mechanisms to tyrosine kinase inhibitors and ways to overcome them. Various novel treatment strategies are under investigation, including immunotherapy, redifferentiation therapy, and second-generation kinase inhibitors. In this review, we will discuss currently available drugs for advanced RR-DTCs, potential mechanisms of drug resistance and future therapeutic avenues.

An Inverse Agonist of Estrogen-Related Receptor Gamma, GSK5182, Enhances Na+/I- Symporter Function in Radioiodine-Refractory Papillary Thyroid Cancer Cells

Previously, we reported that an inverse agonist of estrogen-related receptor gamma (ERRγ), GSK5182, enhances sodium iodide (Na⁺/I^-) symporter (NIS) function through mitogen-activated protein (MAP) kinase signaling in anaplastic thyroid cancer cells. This finding helped us to further investigate the effects of GSK5182 on NIS function in papillary thyroid cancer (PTC) refractory to radioactive iodine (RAI) therapy. Herein, we report the effects of ERRγ on the regulation of NIS function in RAI-resistant PTC cells using GSK5182. RAI-refractory BCPAP cells were treated with GK5182 for 24 h at various concentrations, and radioiodine avidity was determined with or without potassium perchlorate (KClO₄) as an NIS inhibitor. We explored the effects of GSK5182 on ERRγ, the mitogen-activated protein (MAP) kinase pathway, and iodide metabolism-related genes. We examined whether the MAP pathway affected GSK5182-mediated NIS function using U0126, a selective MEK inhibitor. A clonogenic assay was performed to evaluate the cytotoxic effects of I-131. GSK5182 induced an increase in radioiodine avidity in a dose-dependent manner, and the enhanced uptake was completely inhibited by KClO₄ in BCPAP cells. We found that ERRγ was downregulated and phosphorylated extracellular signal-regulated kinase (ERK)1/2 was upregulated in BCPAP cells, with an increase in total and membranous NIS and iodide metabolism-related genes. MEK inhibitors reversed the increase in radioiodine avidity induced by GSK5182. Clonogenic examination revealed the lowest survival in cells treated with a combination of GSK5182 and I-131 compared to those treated with either GSK518 or I-131 alone. We demonstrate that an inverse agonist of ERRγ, GSK5182, enhances the function of NIS protein via the modulation of ERRγ and MAP kinase signaling, thereby leading to increased responsiveness to radioiodine in RAI-refractory papillary thyroid cancer cells.

Case Report: Regaining radioiodine uptake following PRRT in radioiodine-refractory thyroid cancer: A new re-differentiation strategy?

A 61-year-old woman with a history of metastatic follicular thyroid carcinoma became radioiodine-refractory following two doses of radioiodine (RAI) therapy (cumulative = 230 mCi). While no RAI-avid lesion was noticed in the last post-ablation whole-body radioiodine scan (WBIS), she reported sternal pain, which was accompanied by rapidly rising thyroglobulin levels. 18F-FDG and 68Ga-DOTA-TATE PET/CT was performed, showing metastatic pulmonary nodules and a lytic sternal lesion with acceptable avidity (i.e. uptake ≥ liver). Following four cycles of peptide receptor radionuclide therapy (PRRT) with 177Lu-DOTA-TATE, the thyroglobulin levels dropped significantly, and the sternal pain was partially alleviated. Despite only experiencing grade I thrombocytopenia, the treating physician decided to discontinue PRRT and repeat the diagnostic WBIS. Surprisingly, the scan revealed significantly increased tracer uptake in the sternum. The patient received 200 mCi 131I, and WBIS showed increased RAI uptake in all pulmonary nodules as well as bone metastases. We report a case of RAI-refractory thyroid carcinoma with a somatostatin-receptor expression that re-differentiated and gained significant RAI uptake capacity after PRRT.

Effect of recombinant human thyroid stimulating hormone on long-term salivary gland dysfunction in thyroid cancer patients treated with radioactive iodine. A systematic review

Adjuvant radioactive iodine (RAI) is administered to thyroid cancer patients following thyroidectomy for remnant tissue ablation and metastatic disease management. Patients are prepared with thyroid hormone withdrawal (THW) or recombinant human thyroid stimulating hormone (rhTSH). Long-term salivary gland dysfunction (LT-SGD) is a common, dosage-dependent, RAI adverse effect. Although rhTSH preparation seems to reduce LT-SGD, this effect could be due to lower RAI activity generally used in rhTSH-prepared patients. Therefore, this meta-analysis investigated the effect of preparation type on LT-SGD development. Literature search (PubMed, Medline, EmBase, Cochrane, Web of Science, LILACS, Google Scholar) was performed four times (January-November 2022) and studies reporting LT-SGD incidence ≥1 year after RAI in patients prepared with rhTSH/THW were identified. The LT-SGD risk ratio (RR) was estimated with various models considered for sensitivity analysis (fixed-effect, random-effects, study-quality adjusted, publication-bias adjusted, individual-patient-data meta-analysis adjusted for RAI). Subgroup analysis according to RAI activity (<3.7/≥3.7 GBq) also was performed. Literature search resulted in five studies (321 rhTSH, 632 THW patients). The pooled RRs according to various models were 0.65 (95% confidence interval -95CI, 0.49-0.86; fixed-effect); 0.62 (95CI, 0.38-1.02; random-effects); 0.72 (95CI, 0.54-0.96; quality adjusted); 0.76 (95CI, 0.58-0.99; publication-bias adjusted); 0.0.80 (95CI, 0.55-1.14; individual-patient-data meta-analysis). The pooled RRs stratified for RAI activity were 0.26 (95CI, 0.05-1.30) for <3.7 GBq; 0.75 (95CI, 0.57-0.98) for ≥3.7 GBq. The number of patients needed to be prepared with rhTSH to prevent one case of LT-SGD ranged between seven and thirty-seven. There is moderate-quality scientific evidence that rhTSH preparation may consistently protect salivary gland function.

Adherens Junction Integrity Is a Critical Determinant of Sodium Iodide Symporter Residency at the Plasma Membrane of Thyroid Cells

Simple Summary

Most cases of differentiated thyroid carcinoma (DTC) are associated with a good prognosis. However, a significant number progress to advanced disease exhibiting aggressive clinical characteristics. These cases have a poorer prognosis because they become resistant to radioactive iodine (RAI) treatment. One of the causes for this resistance is the reduction of the channel responsible for iodide uptake (NIS—the sodium iodide symporter) at the plasma membrane (PM) of metastatic thyroid cancer cells. Here we describe that cell–cell adhesion is a key determinant for NIS residency at the PM, suggesting that loss of cell–cell adhesion during metastization contributes to RAI treatment resistance in advanced TC. Our findings indicate that successful resensitization therapies might require the use of agents that improve epithelial cell–cell adhesion in refractory TC cells.

Abstract

While most cases of differentiated thyroid carcinoma (DTC) are associated with a good prognosis, a significant number progress to advanced disease exhibiting aggressive clinical characteristics and often becoming refractory to radioactive iodine (RAI) treatment, the current gold-standard therapeutic option for metastatic disease. RAI-refractoriness is caused by defective functional expression of the sodium-iodide symporter (NIS), which is responsible for the active transport of iodide across the plasma membrane (PM) into thyroid follicles. NIS deficiency in these tumors often reflects a transcriptional impairment, but also its defective targeting and retention at the cells’ PM. Using proteomics, we previously characterized an intracellular signaling pathway derived from SRC kinase that acts through the small GTPase RAC1 to recruit and bind the actin-anchoring adaptor EZRIN to NIS, regulating its retention at the PM of both non-transformed and cancer thyroid cells. Here, we describe how by reanalyzing the proteomics data, we identified cell–cell adhesion as the molecular event upstream the pathway involved in the anchoring and retention at the PM. We show that by interacting with NIS at the PM, adherens junction (AJ)-associated P120-catenin recruits and is phosphorylated by SRC, allowing it to recruit RAC1 to the complex. This enables SRC-phosphorylated VAV2 exchange factor to activate RAC1 GTPase, inducing NIS retention at the PM, thus increasing its abundance and function at the surface of thyroid cells. Our findings indicate that the loss of epithelial cell–cell adhesion may contribute to RAI refractoriness, indicating that in addition to stimulating NIS expression, successful resensitization therapies might require the employment of agents that improve cell–cell adhesion and NIS PM retention in refractory TC cells.

CRABP2 Is Associated With Thyroid Cancer Recurrence and Promotes Invasion via the Integrin/FAK/AKT Pathway

Cellular retinoic acid-binding protein 2 (CRABP2) participates in retinoid partitioning between different nuclear receptors. Recently, we identified that CRABP2 is one of the progression-associated genes in thyroid cancer. To explore the prognostic and functional significance of CRABP2, immunohistochemical analysis was performed in thyroid tissues and neoplasms. Overexpression of CRABP2 was observed in malignant thyroid neoplasms but not in benign thyroid lesions. CRABP2 expression was an independent predictive factor for recurrence-free survival in patients with differentiated thyroid cancer. Knockdown of CRABP2 reduced the sensitivity of thyroid cancer cells to retinoic acid. Importantly, CRABP2 expression in thyroid cancer cells was associated with epithelial-mesenchymal transition properties, including anoikis resistance, migration, and invasion capacity. Furthermore, invasion promoted by CRABP2 was mediated at least partly by the integrin/focal adhesion kinase/AKT pathway. In summary, CRABP2 expression is upregulated in thyroid cancer with adverse prognostic implications. The invasion-stimulating effects appear independent of canonical retinoic acid signaling and may serve as a potential therapeutic target.

Enhancing Radioiodine Incorporation into Radioiodine-Refractory Thyroid Cancer with MAPK Inhibition (ERRITI): A Single-Center Prospective Two-Arm Study

PURPOSE

Restoration of iodine incorporation (redifferentiation) by MAPK inhibition was achieved in previously radioiodine-refractory, unresectable thyroid carcinoma (RR-TC). However, results were unsatisfactory in BRAFV600E-mutant (BRAF-MUT) RR-TC. Here we assess safety and efficacy of redifferentiation therapy through genotype-guided MAPK-modulation in patients with BRAF-MUT or wildtype (BRAF-WT) RR-TC.

PATIENTS AND METHODS

In this prospective single-center, two-arm phase II study, patients received trametinib (BRAF-WT) or trametinib + dabrafenib (BRAF-MUT) for 21 ± 3 days. Redifferentiation was assessed by 123I-scintigraphy. In case of restored radioiodine uptake, 124I-guided 131I therapy was performed. Primary endpoint was the redifferentiation rate. Secondary endpoints were treatment response (thyroglobulin, RECIST 1.1) and safety. Parameters predicting successful redifferentiation were assessed using a receiver operating characteristic analysis and Youden J statistic.

RESULTS

Redifferentiation was achieved in 7 of 20 (35%) patients, 2 of 6 (33%) in the BRAF-MUT and 5 of 14 (36%) in the BRAF-WT arm. Patients received a mean (range) activity of 300.0 (273.0-421.6) mCi for 131I therapy. Any thyroglobulin decline was seen in 57% (4/7) of the patients, RECIST 1.1 stable/partial response/progressive disease in 71% (5/7)/14% (1/7)/14% (1/7). Peak standardized uptake value (SUVpeak) < 10 on 2[18F]fluoro-2-deoxy-D-glucose (FDG)-PET was associated with successful redifferentiation (P = 0.01). Transient pyrexia (grade 3) and rash (grade 4) were noted in one patient each.

CONCLUSIONS

Genotype-guided MAPK inhibition was safe and resulted in successful redifferentiation in about one third of patients in each arm. Subsequent 131I therapy led to a thyroglobulin (Tg) decline in more than half of the treated patients. Low tumor glycolytic rate as assessed by FDG-PET is predictive of redifferentiation success. See related commentary by Cabanillas et al., p. 4164.

Sinomenine Hydrochloride Promotes TSHR-Dependent Redifferentiation in Papillary Thyroid Cancer

Radioactive iodine (RAI) plays an important role in the diagnosis and treatment of papillary thyroid cancer (PTC). The curative effects of RAI therapy are not only related to radiosensitivity but also closely related to the accumulation of radionuclides in the lesion in PTC. Sinomenine hydrochloride (SH) can suppress tumor growth and increase radiosensitivity in several tumor cells, including PTC. The aim of this research was to investigate the therapeutic potential of SH on PTC cell redifferentiation. In this study, we treated BCPAP and TPC-1 cells with SH and tested the expression of thyroid differentiation-related genes. RAI uptake caused by SH-pretreatment was also evaluated. The results indicate that 4 mM SH significantly inhibited proliferation and increased the expression of the thyroid iodine-handling gene compared with the control group (p < 0.005), including the sodium/iodide symporter (NIS). Furthermore, SH also upregulated the membrane localization of NIS and RAI uptake. We further verified that upregulation of NIS was associated with the activation of the thyroid-stimulating hormone receptor (TSHR)/cyclic adenosine monophosphate (cAMP) signaling pathway. In conclusion, SH can inhibit proliferation, induce apoptosis, promote redifferentiation, and then increase the efficacy of RAI therapy in PTC cells. Thus, our results suggest that SH could be useful as an adjuvant therapy in combination with RAI therapy in PTC.

Efficacy of Combination Therapy with Lenvatinib and Radioactive Iodine in Thyroid Cancer Preclinical Model

Patients with differentiated thyroid cancer (DTC) usually have good prognosis, while those with advanced disease have poor clinical outcomes. This study aimed to investigate the antitumor effects of combination therapy with lenvatinib and ¹³¹I (CTLI) using three different types of DTC cell lines with different profiling of sodium iodide symporter (NIS) status. The radioiodine accumulation study revealed a significantly increased radioiodine uptake in K1-NIS cells after lenvatinib treatment, while there was almost no uptake in K1 and FTC-133 cells. However, lenvatinib administration before radioiodine treatment decreased radioiodine uptake of K1-NIS xenograft tumor in the in vivo imaging study. CTLI synergistically inhibited colony formation and DTC cell migration, especially in K1-NIS cells. Finally, ¹³¹I treatment followed by lenvatinib administration significantly inhibited tumor growth of the NIS-expressing thyroid cancer xenograft model. These results provide important clinical implications for the combined therapy that lenvatinib should be administered after ¹³¹I treatment to maximize the treatment efficacy. Our synergistic treatment effects by CTLI suggested its effectiveness for RAI-avid thyroid cancer, which retains NIS function. This potential combination therapy suggests a powerful and tolerable new therapeutic strategy for advanced thyroid cancer.

Strategies for Radioiodine Treatment: What’s New

Radioiodine treatment (RAI) represents the most widespread and effective therapy for differentiated thyroid cancer (DTC). RAI goals encompass ablative (destruction of thyroid remnants, to enhance thyroglobulin predictive value), adjuvant (destruction of microscopic disease to reduce recurrences), and therapeutic (in case of macroscopic iodine avid lesions) purposes, but its use has evolved over time. Randomized trial results have enabled the refinement of RAI indications, moving from a standardized practice to a tailored approach. In most cases, low-risk patients may safely avoid RAI, but where necessary, a simplified protocol, based on lower iodine activities and human recombinant TSH preparation, proved to be just as effective, reducing overtreatment or useless impairment of quality of life. In pediatric DTC, RAI treatments may allow tumor healing even at the advanced stages. Finally, new challenges have arisen with the advancement in redifferentiation protocols, through which RAI still represents a leading therapy, even in former iodine refractory cases. RAI therapy is usually well-tolerated at low activities rates, but some concerns exist concerning higher cumulative doses and long-term outcomes. Despite these achievements, several issues still need to be addressed in terms of RAI indications and protocols, heading toward the RAI strategy of the future.

Redox Homeostasis in Thyroid Cancer: Implications in Na+/I- Symporter (NIS) Regulation

Radioiodine therapy (RAI) is a standard and effective therapeutic approach for differentiated thyroid cancers (DTCs) based on the unique capacity for iodide uptake and accumulation of the thyroid gland through the Na⁺/I⁻ symporter (NIS). However, around 5–15% of DTC patients may become refractory to radioiodine, which is associated with a worse prognosis. The loss of RAI avidity due to thyroid cancers is attributed to cell dedifferentiation, resulting in NIS repression by transcriptional and post-transcriptional mechanisms. Targeting the signaling pathways potentially involved in this process to induce de novo iodide uptake in refractory tumors is the rationale of “redifferentiation strategies”. Oxidative stress (OS) results from the imbalance between ROS production and depuration that favors a pro-oxidative environment, resulting from increased ROS production, decreased antioxidant defenses, or both. NIS expression and function are regulated by the cellular redox state in cancer and non-cancer contexts. In addition, OS has been implicated in thyroid tumorigenesis and thyroid cancer cell dedifferentiation. Here, we review the main aspects of redox homeostasis in thyrocytes and discuss potential ROS-dependent mechanisms involved in NIS repression in thyroid cancer.

The Role of the Kinase Inhibitors in Thyroid Cancers

Thyroid cancer is the most common endocrine malignancy, accounting for about 3% of all cancer cases each year worldwide with increasing incidence, but with the mortality remaining stable at low levels. This contradiction is due to overdiagnosis of indolent neoplasms identified by neck ultrasound screening that would remain otherwise asymptomatic. Differentiated thyroid carcinomas (DTCs) are almost curable for 95% with a good prognosis. However, 5% of these tumours worsened toward aggressive forms: large tumours with extravasal invasion, either with regional lymph node or distant metastasis, that represent a serious clinical challenge. The unveiling of the genomic landscape of these tumours shows that the most frequent mutations occur in tyrosine kinase receptors (RET), in components of the MAPK/PI3K signalling pathway (RAS and BRAF) or chromosomal rearrangements (RET/PTC and NTRK hybrids); thus, tyrosine-kinase inhibitor (TKI) treatments arose in the last decade as the most effective therapeutic option for these aggressive tumours to mitigate the MAPK/PI3K activation. In this review, we summarize the variants of malignant thyroid cancers, the molecular mechanisms and factors known to contribute to thyroid cell plasticity and the approved drugs in the clinical trials and those under investigation, providing an overview of available treatments toward a genome-driven oncology, the only opportunity to beat cancer eventually through tailoring the therapy to individual genetic alterations. However, radiotherapeutic and chemotherapeutic resistances to these anticancer treatments are common and, wherever possible, we discuss these issues.

Personalized Diagnosis in Differentiated Thyroid Cancers by Molecular and Functional Imaging Biomarkers: Present and Future

Personalized diagnosis can save unnecessary thyroid surgeries, in cases of indeterminate thyroid nodules, when clinicians tend to aggressively treat all these patients. Personalized diagnosis benefits from a combination of imagery and molecular biomarkers, as well as artificial intelligence algorithms, which are used more and more in our timeline. Functional imaging diagnosis such as SPECT, PET, or fused images (SPECT/CT, PET/CT, PET/MRI), is exploited at maximum in thyroid nodules, with a long history in the past and a bright future with many suitable radiotracers that could properly contribute to diagnosing malignancy in thyroid nodules. In this way, patients will be spared surgery complications, and apparently more expensive diagnostic workouts will financially compensate each patient and also the healthcare system. In this review we will summarize essential available diagnostic tools for malignant and benignant thyroid nodules, beginning with functional imaging, molecular analysis, and combinations of these two and other future strategies, including AI or NIS targeted gene therapy for thyroid carcinoma diagnosis and treatment as well.

Propensity Score-Matched Analysis to Identify Pathways Associated with Loss of Sodium Iodide Symporter in Papillary Thyroid Cancer

Sodium iodide symporter (NIS) expression in thyroid follicular cells plays an important role in normal physiology and radioactive iodine therapy for thyroid cancer. Loss of NIS expression is often seen in thyroid cancers and may lead to radioiodine refractoriness. To explore novel mechanisms of NIS repression beyond oncogenic drivers, clinical and RNA-seq data from the thyroid cancer dataset of The Cancer Genome Atlas were analyzed. Propensity score matching was used to control for various genetic background factors. We found that tumoral NIS expression was negatively correlated with tumor size. Additionally, low NIS expression was the only factor associated with recurrence-free survival in a Cox multivariate regression analysis. After matching for clinicopathologic profiles and driver mutations, the principal component analysis revealed distinct gene expressions between the high and low NIS groups. Gene set enrichment analysis suggested the downregulation of hedgehog signaling, immune networks, and cell adhesions. Positively enriched pathways included DNA replication, nucleotide excision repair, MYC, and Wnt/β-catenin pathways. In summary, we identified several potential targets which could be exploited to rescue the loss of NIS expression and develop redifferentiation strategies to facilitate radioactive iodine therapy for thyroid cancer.

Molecular Imaging and Theragnostics of Thyroid Cancers

Molecular imaging plays an important role in the evaluation and management of different thyroid cancer histotypes. The existing risk stratification models can be refined, by incorporation of tumor-specific molecular markers that have theranostic power, to optimize patient-specific (individualized) treatment decisions. Molecular imaging with varying radioisotopes of iodine (i.e., ¹³¹I, ¹²³I, ¹²⁴I) is an indispensable component of dynamic and theragnostic risk stratification of differentiated carcinoma (DTC) while [¹⁸F]F-fluorodeoxyglucose ([¹⁸F]FDG) positron emission tomography/computed tomography (PET/CT) helps in addressing disease aggressiveness, detects distant metastases, and risk-stratifies patients with radioiodine-refractory DTC, poorly differentiated and anaplastic thyroid cancers. For medullary thyroid cancer (MTC), a neuroendocrine tumor derived from thyroid C-cells, [¹⁸F]F-dihydroxyphenylalanine (6-[¹⁸F]FDOPA) PET/CT and/or [¹⁸F]FDG PET/CT can be used dependent on serum markers levels and kinetics. In addition to radioiodine therapy for DTC, some theragnostic approaches are promising for metastatic MTC as well. Moreover, new redifferentiation strategies are now available to restore uptake in radioiodine-refractory DTC while new theragnostic approaches showed promising preliminary results for advanced and aggressive forms of follicular-cell derived thyroid cancers (i.e., peptide receptor radiotherapy). In order to help clinicians put the role of molecular imaging into perspective, the appropriate role and emerging opportunities for molecular imaging and theragnostics in thyroid cancer are discussed in our present review.

Postoperative external beam radiotherapy for locoregional control in iodine refractory differentiated thyroid cancer

BACKGROUND

The role of postoperative external beam radiotherapy (EBRT) in patients with residual iodine refractory-differentiated thyroid cancer (IR-DTC) is still inconclusive. The aim of this retrospective study was to evaluate locoregional control (LRC) and overall survival (OS), and potential side effects after postoperative EBRT for both microscopic and macroscopic non-radically resected, locally advanced IR-DTC.

METHODS

Between 1990 and 2016, 49 patients with locally advanced IR-DTC received EBRT for microscopic (R1; n = 28) or macroscopic (R2; n = 21) locoregional residual disease. For more insight into the added effect of EBRT, we performed an intrapatient sub-analysis in 32 patients who had undergone more than 1 surgical intervention, comparing LRC after primary, curative-intended surgery with LRC after repeated surgery plus EBRT. To estimate LRC and OS, we used Kaplan-Meier curves. From 2007 onward, we prospectively recorded toxicity data in our head and neck cancer database (n = 10).

RESULTS

LRC rates 5 years after EBRT were higher for R1 (84.3%) than for R2 (44.9%) residual disease (P = 0.016). The 5-year OS rate after EBRT was 72.1% for R1 and 33.1% for R2 disease (P = 0.003). In the intrapatient analysis (n = 32), LRC rates were 6.3% 5 years after only initial surgery and 77.9% after repeated surgery with EBRT (P < 0.001). Acute toxicity was limited to grade I and II xerostomia, mucositis, and hoarseness; only one patient developed late grade III dysphagia.

CONCLUSIONS

Postoperative EBRT is associated with long-lasting LRC and OS with acceptable toxicity in patients with locally advanced IR-DTC, especially in microscopic residual disease.

AhR Antagonist Promotes Differentiation of Papillary Thyroid Cancer via Regulating circSH2B3/miR-4640-5P/IGF2BP2 Axis

Abnormally high expression of aryl hydrocarbon receptor (AhR) has been implicated in dedifferentiation of radioiodine-refractory papillary thyroid cancer (RR-PTC). This study aimed to evaluate the differentiation effect of AhR antagonist in PTC, and to explore the potential mechanism of it. Results showed that AhR antagonists promoted differentiation of PTC, as shown as increase in ¹²⁵I uptake and Na/I symporter (NIS) expression level. CircRNA microarray in K1 cells treated with StemRegenin 1(SR1) revealed that hsa_circ_0006741 (circSH2B3) was down-regulated in SR1 treated K1 cells. Downregulation of circSH2B3 increased ¹²⁵I uptake and NIS expression levels. CircSH2B3 acted as an endogenous sponge of hsa-miR-4640-5p and modulated IGF2BP2 expression. IGF2BP2 overexpression induced dedifferentiation of PTC, while silencing IGF2BP2 accelerated differentiation of PTC cells. Rescue studies showed that the dedifferentiation activity of AhR was modulated by the circSH2B3/miR-4640-5p/IGF2BP2 axis. Our findings confirmed for the first time that AhR antagonists promote differentiation of PTC via inhibiting the circSH2B3/miR-4640-5p/IGF2BP2 axis, offering a novel therapeutic approach and a potential marker for differentiation of PTC.

Dynamic Cancer Cell Heterogeneity: Diagnostic and Therapeutic Implications

Though heterogeneity of cancers is recognized and has been much discussed in recent years, the concept often remains overlooked in different routine examinations. Indeed, in clinical or biological articles, reviews, and textbooks, cancers and cancer cells are generally presented as evolving distinct entities rather than as an independent heterogeneous cooperative cell population with its self-oriented biology. There are, therefore, conceptual gaps which can mislead the interpretations/diagnostic and therapeutic approaches. In this short review, we wish to summarize and discuss various aspects of this dynamic evolving heterogeneity and its biological, pathological, clinical, diagnostic, and therapeutic implications, using thyroid carcinoma as an illustrative example.

Target Therapy in Thyroid Cancer: Current Challenge in Clinical Use of Tyrosine Kinase Inhibitors and Management of Side Effects

Thyroid cancer (TC) is the most common endocrine malignancy. TC is classified as differentiated TC (DTC), which includes papillary and follicular subtypes and Hürthle cell variants, medullary TC (MTC), anaplastic TC (ATC), and poorly differentiated TC (PDTC). The standard of care in DTC consists of surgery together with radioactive iodine (¹³¹I) therapy and thyroid hormone, but patients with MTC do not benefit from ¹³¹I therapy. Patients with advanced TC resistant to ¹³¹I treatment (RAI-R) have no chance of cure, as well as patients affected by ATC and progressive MTC, in which conventional therapy plays only a palliative role, representing, until a few years ago, an urgent unmet need. In the last decade, a better understanding of molecular pathways involved in the tumorigenesis of specific histopathological subtypes of TC has led to develop tyrosine kinase inhibitors (TKIs). TKIs represent a valid treatment in progressive advanced disease and were tested in all subtypes of TC, highlighting the need to improve progression-free survival. However, treatments using these novel therapeutics are often accompanied by side effects that required optimal management to minimize their toxicities and thereby enable patients who show benefit to continue treatment and obtain maximal clinical efficacy. The goal of this overview is to provide an update on the current use of the main drugs recently studied for advanced TC and the management of the adverse events.

Capsaicin restores sodium iodine symporter-mediated radioiodine uptake through bypassing canonical TSH‒TSHR pathway in anaplastic thyroid carcinoma cells

Anaplastic thyroid cancer (ATC) is a rare but highly lethal disease. ATCs are resistant to standard therapies and are extremely difficult to manage. The stepwise cell dedifferentiation results in the impairment of the iodine-metabolizing machinery and the infeasibility of radioiodine treatment in ATC. Hence, re-inducing iodine-metabolizing gene expression to restore radioiodine avidity is considered as a promising strategy to fight against ATC. In the present study, capsaicin (CAP), a natural potent transient receptor potential vanilloid type 1 (TRPV1) agonist, was discovered to re-induce ATC cell differentiation and to increase the expression of thyroid transcription factors (TTFs including TTF-1, TTF-2, and PAX8) and iodine-metabolizing proteins, including thyroid stimulating hormone receptor (TSHR), thyroid peroxidase, and sodium iodine symporter (NIS), in two ATC cell lines, 8505C and FRO. Strikingly, CAP treatment promoted NIS glycosylation and its membrane trafficking, resulting in a significant enhancement of radioiodine uptake of ATC cells in vitro. Mechanistically, CAP activated TRPV1 channel and subsequently triggered Ca2+ influx, cyclic adenosine monophosphate (cAMP) generation, and cAMP responsive element binding protein (CREB) signal activation. Next, CREB recognized and bound to the promoter of SLC5A5 to facilitate its transcription. Moreover, the TRPV1 antagonist CPZ, the calcium chelator BAPTA, and the PKA inhibitor H-89 effectively alleviated the re-differentiation exerted by CAP, demonstrating that CAP might improve radioiodine avidity through the activation of the TRPV1‒Ca2+/cAMP/PKA/CREB signaling pathway. In addition, our study indicated that CAP might trigger a novel cascade to re-differentiate ATC cells and provide unprecedented opportunities for radioiodine therapy in ATC, bypassing canonical TSH‒TSHR pathway.

[Treatment strategy by radioiodine refractory differentiated thyroid cancer]

Traditionally, the multimodal therapy concept for differentiated thyroid carcinomas consists of thyroidectomy with neck dissection (for cN + neck) and adjuvant radioiodine ablation with subsequent risk-adapted TSH suppression. The extent of radioiodine uptake in metastatic thyroid carcinomas plays a significant role is significant in terms of prognosis. Radioiodine refractory lesions are characterized by the lack of radioiodine uptake in combination with the lack of decrease in the tumor marker thyroglobulin as well as signs of progression on imaging. Due to the mostly indolent course over a long period of time, a wait-and-see strategy in combination with local management of distant metastase symptom relief appears to be primarily sufficient. By evidence for change in tumor dynamics, the need for a multi-tyrosine kinase inhibitor (sorafenib, lenvatinib)-based systemic therapy should be thoroughly evaluated. These substances are mostly associated with an unfavorable side-effect profile (diarrhea, rash, arterial hypertension, local wound healing disorders), which leads to a non-negligible rate of treatment-associated morbidity and a high number of treatment interruptions. For this reason, two selective RET inhibitors (selpercatinib, pralsetinib) for differentiated thyroid carcinomas were approved by the FDA in 2020. A new perspective for the future would be the variable re-differentiation strategies, which aim to increase the sensitivity of tumor cells to radioiodine.

Salvage surgery for cervical radioiodine refractory 18F-FDG-PET positive recurrence of papillary thyroid cancer

PURPOSE

Five percent of patients with differentiated thyroid cancer are diagnosed with radioiodine refractory relapse in the course of the disease. For isolated or oligometastatic cervical recurrence, resection or another local treatment is recommended. In this study, the impact of surgical treatment of cervical radioiodine refractory 18F-FDG-PET positive relapse of papillary thyroid cancer (PTC) was evaluated.

METHODS

Patients receiving radioiodine therapy between 2005 and 2015 at the University Hospital of Cologne, Germany, for PTC were screened. The subgroup of patients undergoing surgery during the course of disease after recommendation by a multidisciplinary endocrine team for cervical radioiodine refractory 18F-FDG-PET positive recurrence was identified. Demographics, clinic-pathologic characteristics, oncologic treatment, and outcome were analyzed.

RESULTS

Thirty (3%) of 969 patients with PTC treated with radioiodine therapy at our institution underwent surgery for radioiodine refractory 18F-FDG-PET positive cervical recurrence during the course of the disease. In eight (26.6%) patients, more than one operation was performed. Sixteen (53%) patients received external beam radiation therapy (EBRT) after surgery. Follow-up was on average, 79.2 ± 61.6 months after the last surgical treatment. Biochemical and radiological cure was seen in 12 (40%) patients. Remission was significantly more frequent in younger patients (P = 0.0001) with lymph node rather than soft tissue tumor recurrence (P = 0.004).

CONCLUSIONS

Surgical treatment of radioiodine refractory 18F-FDG-PET positive cervical recurrence led to biochemical and radiological cure in about 40% of patients in this study. Further data are needed concerning risk stratification of potential subgroups benefitting of surgical approach and the possible role of EBRT after repetitive surgery.

Canadian consensus statement on the management of radioactive iodine-resistant differentiated thyroid cancer

Radioactive iodine-resistant differentiated thyroid cancer (RAIRTC) is an aggressive form of thyroid cancer that is uncommon and heterogeneous in its clinical behavior. With the emergence of more effective systemic therapy, the need for guidance in decision-making was recognized and a consensus committee of national experts was assembled. The consensus committee consisted of 13 clinicians involved in treating RAIRTC from across Canada and included endocrinologists, nuclear medicine physicians, surgeons, and radiation and medical oncologists. Domains of interest were identified by consensus, and evidence gathered using systematic reviews. Consensus recommendations for the diagnosis and management of RAIRTC were developed. It was recognized that the rarity of RAIRTC in practice and heterogeneous patterns of thyroid cancer care could limit access to effective therapy for some RAIRTC patients. This document offers guidance to manage RAIRTC patients in a multidisciplinary manner.

A Joint Statement from the American Thyroid Association, the European Association of Nuclear Medicine, the European Thyroid Association, the Society of Nuclear Medicine and Molecular Imaging on Current Diagnostic and Theranostic Approaches in the Management of Thyroid Cancer

Background: The American Thyroid Association (ATA), the European Association of Nuclear Medicine, the European Thyroid Association, and the Society of Nuclear Medicine and Molecular Imaging have established an intersocietal working group to address the current controversies and evolving concepts in thyroid cancer management and therapy. The working group annually identifies topics that may significantly impact clinical practice and publishes expert opinion articles reflecting intersocietal collaboration, consensus, and suggestions for further research to address these important management issues. Summary: In 2019, the intersocietal working group identified the following topics for review and interdisciplinary discussion: (i) perioperative risk stratification, (ii) the role of diagnostic radioactive iodine (RAI) imaging in initial staging, and (iii) indicators of response to RAI therapy. Conclusions: The intersocietal working group agreed that (i) initial patient management decisions should be guided by perioperative risk stratification that should include the eighth edition American Joint Committee on Cancer staging system to predict disease specific mortality, the modified 2009 ATA risk stratification system to estimate structural disease recurrence, with judicious incorporation of molecular theranostics to further refine management recommendations; (ii) diagnostic RAI scanning in ATA intermediate risk patients should be utilized selectively rather than being considered mandatory or not necessary for all patients in this category; and (iii) a consistent semiquantitative reporting system should be used for response evaluations after RAI therapy until a reproducible and clinically practical quantitative system is validated.

Effect of Kinase Inhibitors on the Technetium-99m Uptake into Thyroid Carcinoma Cells In Vitro

BACKGROUND/AIM

We evaluated the potential of the kinase inhibitors sorafenib, lenvatinib and selumetinib on increasing the uptake of technetium-99m into thyroid cancer cells.

MATERIALS AND METHODS

Four established cell lines and three patient's cell cultures were treated with 0.1, 1 and 5 μM of sorafenib, lenvatinib and selumetinib for 72 hours. After incubation with 1 MBq of technetium-99m, the radioactivity uptake was measured.

RESULTS

The experiments showed heterogeneous results. Maximum technetium-99m uptake increases of 312% (sorafenib), 326% (lenvatinib) and 759% (selumetinib) were obtained using the highest applied concentrations. In some tests, an uptake reduction or no effect was observed.

CONCLUSION

Kinase inhibitors have a positive effect on technetium-99m uptake. Due to study limitations, a redifferentiating effect of the drugs could not be definitely proven. Unspecific cytotoxicity might have a confounding effect.

MiR-181a-5p Regulates NIS Expression in Papillary Thyroid Carcinoma

NIS is a potent iodide transporter encoded by the SLC5A5 gene. Its expression is reduced in papillary thyroid carcinoma (PTC). In this study we analyzed the impact of miR-181a-5p on NIS expression in the context of PTC. We used real-time PCR to analyze the expression of SLC5A5 and miR-181a-5p in 49 PTC/normal tissue pairs. Luciferase assays and mutagenesis were performed to confirm direct binding of miR-181a-5p to the 3′UTR of SLC5A5 and identify the binding site. The impact of modulation of miR-181a-5p using appropriate plasmids on endogenous NIS and radioactive iodine accumulation was verified. We confirmed downregulation of SLC5A5 and concomitant upregulation of miR-181a-5p in PTC. Broadly used algorithms did not predict the binding site of miR-181a-5p in 3′UTR of SLC5A5, but we identified and confirmed the binding site through mutagenesis using luciferase assays. In MCF7 and HEK293-flhNIS cell lines, transfection with mir-181a-expressing plasmid decreased endogenous SLC5A5, whereas silencing of miR-181a-5p increased it. We observed similar tendencies in protein expression and radioactive iodine accumulation. This study shows for the first time that miR-181a-5p directly regulates SLC5A5 expression in the context of PTC and may decrease efficacy of radioiodine treatment. Accordingly, miR-181a-5p may serve as an emerging target to enhance the efficacy of radioactive iodine therapy.

BRAF Inhibitors Induce Feedback Activation of RAS Pathway in Thyroid Cancer Cells

BRAF^V600E is the most frequent oncogenic mutation identified in papillary thyroid cancer (PTC). In PTC patients who do not respond to standard treatment, BRAF inhibitors are currently tested as alternative strategies. However, as observed for other targeted therapies, patients eventually develop drug resistance. The mechanisms of BRAF inhibitors response are still poorly understood in a thyroid cancer (TC) context. In this study, we investigated in BRAF^V600E mutated TC cell lines the effects of Vemurafenib and Dabrafenib, two BRAF inhibitors currently used in a clinical setting. We assessed cell proliferation, and the expression and activity of the thyroid function related transporter NIS following the treatment with BRAF inhibitors. In addition, we investigated the global gene expression by microarray, the relevant modulated biological processes by gene set enrichment analysis (GSEA), and TC specific gene signatures related to MAPK pathway activation, thyroid differentiation, and transcriptional profile associated with BRAF^V600E or RAS mutation. We found that both inhibitors induce antiproliferative and redifferentiative effects on TC cells, as well as a rewiring of the MAPK pathway related to RAS signaling. Our results suggest a possible mechanism of drug response to the BRAF inhibitors Vemurafenib or Dabrafenib, supporting very recent findings in TC patients treated with targeted therapies.

Targeting EML4-ALK gene fusion variant 3 in thyroid cancer

Finding targetable gene fusions can expand the limited treatment options in radioactive iodine-refractory (RAI-r) thyroid cancer. To that end, we established a novel cell line 'JVE404' derived from an advanced RAI-r papillary thyroid cancer (PTC) patient, harboring an EML4-ALK gene fusion variant 3 (v3). Different EML4-ALK gene fusions can have different clinical repercussions. JVE404 cells were evaluated for cell viability and cell signaling in response to ALK inhibitors crizotinib, ceritinib and lorlatinib, in parallel to the patient's treatment. He received, after first-line lenvatinib, crizotinib (Drug Rediscovery Protocol (DRUP) trial), and lorlatinib (compassionate use). In vitro treatment with crizotinib or ceritinib decreased viability in JVE404, but most potently and significantly only with lorlatinib. Western blot analysis showed a near total decrease of 99% and 89%, respectively, in pALK and pERK expression levels in JVE404 cells with lorlatinib, in contrast to remaining signal intensities of a half and a third of control, respectively, with crizotinib. The patient had a 6-month lasting stable disease on crizotinib, but progressive disease occurred, including the finding of cerebral metastases, at 8 months. With lorlatinib, partial response, including clinical cerebral activity, was already achieved at 11 weeks' use and ongoing partial response at 7 months. To our best knowledge, this is the first reported case describing a patient-specific targeted treatment with lorlatinib based on an EML4-ALK gene fusion v3 in a thyroid cancer patient, and own cancer cell line. Tumor-agnostic targeted therapy may provide valuable treatment options in personalized medicine.

Molecular mechanisms of radioactive iodine refractoriness in differentiated thyroid cancer: Impaired sodium iodide symporter (NIS) expression owing to altered signaling pathway activity and intracellular localization of NIS

The advanced, metastatic differentiated thyroid cancers (DTCs) have a poor prognosis mainly owing to radioactive iodine (RAI) refractoriness caused by decreased expression of sodium iodide symporter (NIS), diminished targeting of NIS to the cell membrane, or both, thereby decreasing the efficacy of RAI therapy. Genetic aberrations (such as BRAF, RAS, and RET/PTC rearrangements) have been reported to be prominently responsible for the onset, progression, and dedifferentiation of DTCs, mainly through the activation of mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/AKT signaling pathways. Eventually, these alterations result in a lack of NIS and disabling of RAI uptake, leading to the development of resistance to RAI therapy. Over the past decade, promising approaches with various targets have been reported to restore NIS expression and RAI uptake in preclinical studies. In this review, we summarized comprehensive molecular mechanisms underlying the dedifferentiation in RAI-refractory DTCs and reviews strategies for restoring RAI avidity by tackling the mechanisms.

Personalized radioiodine therapy for thyroid cancer patients with known disease

Radioactive iodine (RAI) ¹³¹I is a targeted therapy for patients with RAI-avid follicular cell-derived thyroid cancer. However, the responsiveness to ¹³¹I therapy varies among thyroid cancer patients mainly owing to differential RAI uptake and RAI radiosensitivity among patients’ lesions. A personalized approach to maximize ¹³¹I therapeutic efficacy is proposed based on recent scientific advances and future opportunities.

Radio-Iodide Treatment: From Molecular Aspects to the Clinical View

Simple Summary

This year marks the 80th commemoration of the first time that radio-iodide treatment (RAI) was used. RAI is one of the most effective targeted internal radiation anticancer therapies ever devised and it has been used for many decades, however, a thorough understanding of the underlying molecular mechanisms involved could greatly improve the success of this therapy. This is an in-depth innovative review focusing on the molecular mechanisms underlying radio-iodide therapy in thyroid cancer and how the alteration of these mechanisms affects the results in the clinic.

Abstract

Thyroid radio-iodide therapy (RAI) is one of the oldest known and used targeted therapies. In thyroid cancer, it has been used for more than eight decades and is still being used to improve thyroid tumor treatment to eliminate remnants after thyroid surgery, and tumor metastases. Knowledge at the molecular level of the genes/proteins involved in the process has led to improvements in therapy, both from the point of view of when, how much, and how to use the therapy according to tumor type. The effectiveness of this therapy has spread into other types of targeted therapies, and this has made sodium/iodide symporter (NIS) one of the favorite theragnostic tools. Here we focus on describing the molecular mechanisms involved in radio-iodide therapy and how the alteration of these mechanisms in thyroid tumor progression affects the diagnosis and results of therapy in the clinic. We analyze basic questions when facing treatment, such as: (1) how the incorporation of radioiodine in normal, tumor, and metastatic thyroid cells occurs and how it is regulated; (2) the pros and cons of thyroid hormonal deprivation vs. recombinant human Thyroid Stimulating Hormone (rhTSH) in radioiodine residence time, treatment efficacy, thyroglobulin levels and organification, and its influence on diagnostic imaging tests and metastasis treatment; and (3) the effect of stunning and the possible causes. We discuss the possible incorporation of massive sequencing data into clinical practice, and we conclude with a socioeconomical and clinical vision of the above aspects.

Non-Coding RNAs: Uncharted Mediators of Thyroid Cancer Pathogenesis

Thyroid cancer is the most prevalent malignancy of the endocrine system and the ninth most common cancer globally. Despite the advances in the management of thyroid cancer, there are critical issues with the diagnosis and treatment of thyroid cancer that result in the poor overall survival of undifferentiated and metastatic thyroid cancer patients. Recent studies have revealed the role of different non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) that are dysregulated during thyroid cancer development or the acquisition of resistance to therapeutics, and may play key roles in treatment failure and poor prognosis of the thyroid cancer patients. Here, we systematically review the emerging roles and molecular mechanisms of ncRNAs that regulate thyroid tumorigenesis and drug response. We then propose the potential clinical implications of ncRNAs as novel diagnostic and prognostic biomarkers for thyroid cancer.