Refractory thyroid carcinoma: which systemic treatment to use?

Molecular basis and targeted therapies for radioiodine refractory thyroid cancer

Patients diagnosed with radioiodine refractory thyroid cancer (RAIR-TC) are not amenable to novel ¹³¹ I therapy due to the reduced expression of sodium iodide symporter (Na+/I- symporter, NIS) and/or the impairment of NIS trafficking to the plasma membrane. RAIR-TC patients have a relatively poor prognosis with a mean life expectancy of 3-5 years, contributing to the majority of TC-associated mortality. Identifying RAIR-TC patients and selecting proper treatment strategies remain challenging for clinicians. In this review, we demonstrate the updated clinical scenarios or the so-called "definitions" of RAIR-TC suggested by several associations based on ¹³¹ I uptake ability and tumor response post-¹³¹ I therapy. We also discuss current knowledge of the molecular alterations involved in membrane-localized NIS loss, which provides a preclinical basis for the development of targeted therapies, in particular, tyrosine kinase inhibitors (TKIs), redifferentiation approaches, and immune checkpoint inhibitors.

APOBEC SBS13 Mutational Signature-A Novel Predictor of Radioactive Iodine Refractory Papillary Thyroid Carcinoma

Standard surgery followed by radioactive iodine (131I, RAI) therapy are not curative for 5−20% of papillary thyroid carcinoma (PTC) patients with RAI refractory disease. Early predictors indicating therapeutic response to RAI therapy in PTC are yet to be elucidated. Whole-exome sequencing was performed (at median depth 198x) on 66 RAI-refractory and 92 RAI-avid PTCs with patient-matched germline. RAI-refractory tumors were significantly associated with distinct aggressive clinicopathological features, including positive surgical margins (p = 0.016) and the presence of lymph node metastases at primary diagnosis (p = 0.012); higher nonsilent tumor mutation burden (p = 0.011); TERT promoter (TERTp) mutation (p < 0.0001); and the enrichment of the APOBEC-related single-base substitution (SBS) COSMIC mutational signatures 2 (p = 0.030) and 13 (p < 0.001). Notably, SBS13 (odds ratio [OR] 30.4, 95% confidence intervals [CI] 1.43−647.22) and TERTp mutation (OR 41.3, 95% CI 4.35−391.60) were revealed to be independent predictors of RAI refractoriness in PTC (p = 0.029 and 0.001, respectively). Although SBS13 and TERTp mutations alone highly predicted RAI refractoriness, when combined, they significantly increased the likelihood of predicting RAI refractoriness in PTC. This study highlights the APOBEC SBS13 mutational signature as a novel independent predictor of RAI refractoriness in a distinct subgroup of PTC.

Towards an era of precise diagnosis and treatment: Role of novel molecular modification-based imaging and therapy for dedifferentiated thyroid cancer

Dedifferentiated thyroid cancer is the major cause of mortality in thyroid cancer and is difficult to treat. Hence, the essential molecular mechanisms involved in dedifferentiation should be thoroughly investigated. Several studies have explored the biomolecular modifications of dedifferentiated thyroid cancer such as DNA methylation, protein phosphorylation, acetylation, ubiquitination, and glycosylation and the new targets for radiological imaging and therapy in recent years. Novel radionuclide tracers and drugs have shown attractive potential in the early diagnosis and treatment of dedifferentiated thyroid cancer. We summarized the updated molecular mechanisms of dedifferentiation combined with early detection by molecular modification-based imaging to provide more accurate diagnosis and novel therapeutics in the management of dedifferentiated thyroid cancer.

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.

Thyroid Follicular Epithelial Cell-Derived Cancer: New Approaches and Treatment Strategies

Thyroid follicular epithelial cell-derived cancer includes papillary carcinoma, follicular carcinoma, Hürthle cell carcinoma, poorly differentiated thyroid cancer, and anaplastic thyroid carcinoma. Although the incidence of thyroid cancer has increased over the past 30 years, there has not been a significant increase in patient mortality. Use of increasingly sensitive detection methods such as high-resolution imaging has enabled earlier detection and better characterization of the thyroid malignancies. In the past several years, researchers have evaluated genetic mutations promoting thyroid carcinogenesis and oncogenesis. The identification of genetic mutations is important in understanding tumor initiation and progression. Additionally, these identified mutations may also serve as potential diagnostic or prognostic indicators and therapeutic molecular targets.

The Association Between Radioiodine Refractory in Papillary Thyroid Carcinoma, Sodium/Iodide Symporter Expression, and BRAF V600E Mutation

Objective

To study the association between radioiodine refractory papillary thyroid carcinoma, sodium/iodide symporter (NIS) expression, and the BRAF ^V600E mutation.

Methods

A study was conducted on 30 radioiodine refractory papillary thyroid carcinoma patients and 30 radioiodine-avid papillary thyroid carcinoma patients. The expressions of sodium/iodide symporter and BRAF ^V600E mutated protein were determined by immunohistochemistry using formalin-fixed, paraffin-embedded tissue.

Results

The mutated BRAF ^V600E protein was identified in 26 radioiodine refractory papillary thyroid carcinoma subjects (86.7%) and 22 radioiodine-avid papillary thyroid carcinoma subjects (73.3%), with no significant difference between the 2 groups (P = 0.3). Sodium/iodide symporter expression was detected in 4 of 30 cases (13.3%) from the radioiodine-avid papillary thyroid carcinoma group but was negative for all radioiodine refractory cases. There was no association between sodium/iodide symporter expression and radioiodine refractory papillary thyroid carcinoma (P = 0.11). Cases with positive NIS expression were likely negative for BRAF ^V600E mutation (3/4; P = 0.02).

Conclusion

Papillary thyroid carcinomas with BRAF ^V600E mutation were more likely to be negative for NIS expression. BRAF ^V600E mutation and NIS expressions cannot be used to predict radioiodine sensitivity.

Current understanding of nonsurgical interventions for refractory differentiated thyroid cancer: a systematic review

Thyroid cancer incidence and related mortality is increasing year-on-year, and although treatment for early disease with surgery and radioiodine results in a 98% 5-year survival rate, recurrence and treatment refractory disease is evident in an unacceptable number of patients. Alternative treatment regimens have therefore been sought in the form of tyrosine kinase inhibitors, immunotherapy, vaccines, chimeric antigen receptor T-cell therapy and oncolytic viruses. The current review aims to consolidate knowledge and highlight the latest clinical trials using secondary therapies in thyroid cancer treatment, focusing on both in vitro and in vivo studies, which have investigated therapies other than radioiodine.

The rates of thyroid cancer and related deaths are increasing. Differentiated thyroid cancer is the most common type of thyroid cancer. Early disease can be treated with surgery and radioactive iodine with very good outcomes. However, this therapy does not work for a small number of patients making it important to find different (secondary) treatment options. This review summarizes the results of published research about secondary treatment options for differentiated thyroid cancer. Ongoing research including laboratory-based and clinical trials are also highlighted.

The intratumor microbiome predicts prognosis across gender and subtypes in papillary thyroid carcinoma

While the intratumor microbiome has become increasingly implicated in cancer development, the microbial landscape of papillary thyroid carcinoma (PTC) is essentially uninvestigated. PTC is characterized by varied prognosis between gender and cancer subtype, but the cause for gender and subtype-based dissimilarities is unclear. Women are more frequently diagnosed with PTC, while men suffer more advanced-staged PTC. In addition, tall cell variants are more aggressive than classical and follicular variants of PTC. We hypothesized that intratumor microbiome composition distinctly alters the immune landscape and predicts clinical outcome between PTC subtypes and between patient genders. Raw whole-transcriptome RNA-sequencing, Level 3 normalized mRNA expression read counts, and DNA methylation 450 k sequencing data for untreated, nonirradiated tumor, and adjacent normal tissue were downloaded from the Genomic Data Commons (GDC) legacy archive for 563 thyroid carcinoma patients. Microbe counts were extracted using Pathoscope 2.0 software. We correlated microbe abundance to clinical variables and immune-associated gene expression. Gene-set enrichment, mutation, and methylation analyses were conducted to correlate microbe abundance to characterize microbes' roles. Overall, PTC tumor tissue significantly lacked microbes that are populated in adjacent normal tissue, which suggests presence of microbes may be critical in controlling immune cell expression and regulating immune and cancer pathways to mitigate cancer growth. In contrast, we also found that microbes distinctly abundant in tall cell and male patient cohorts were also correlated with higher mutation expression and methylation of tumor suppressors. Microbe dysbiosis in specific PTC types may explain observable differences in PTC progression and pathogenesis. These microbes provide a basis for developing specialized prebiotic and probiotic treatments for varied PTC tumors.

[The role of molecular testing in thyroid tumors]

&sup1;I.M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia; &sup2;Endocrinology Research Centre, Moscow, Russia Thyroid cancer is the most common endocrine gland cancer. In the last few decades, the molecular diagnostics for thyroid tumors have been widely researched. It is one of the few cancers whose incidence has increased in recent years from microcarcinomas to common, large forms, in all age groups, from children to the elder people. Most researches focus on the genetic basis, since our current knowledge of the genetic background of various forms of thyroid cancer is far from being complete. Molecular and genetic research has several main directions: firstly, differential diagnosis of thyroid tumors, secondly, the prognostic value of detected mutations in thyroid cancer, and thirdly, targeted therapy for aggressive or radioactive iodine-resistant forms of thyroid cancer. In this review, we wanted to update our understanding and describe the prevailing advances in molecular genetics of thyroid cancer, focusing on the main genes associated with the pathology and their potential application in clinical practice.

Prophylactic lymph node dissection in clinically N0 differentiated thyroid carcinoma: example of personalized treatment

Considering the 'differentiated thyroid carcinoma (DTC) epidemic', the indolent nature of DTC imposes a treatment paradigm shift toward elimination of recurrence. Lymph node metastases in cervical compartments, encountered in 20-90% of DTC, are the main culprit of recurrent disease, affecting 5-30% of patients. Personalized risk-stratified cervical prophylactic lymph node dissection (PLND) at initial thyroidectomy in DTC with no clinical, sonographic or intraoperative evidence of lymph node metastases (clinically N0) has been advocated, though not unanimously. The present review dissects the controversy over PLND. Weighing the benefit yielded from PLND up against the PLND-related morbidity is so far hampered by the inconsistent profit yielded by PLND and the challenging patient selection. Advances in tailoring PLND are anticipated to empower optimal patient care.

Down-regulation of FOXR2 inhibits hypoxia-driven ROS-induced migration and invasion of thyroid cancer cells via regulation of the hedgehog pathway

Forkhead box R2 (FOXR2), a new member of the FOX family, is involved in a wide range of biological processes such as embryogenesis, differentiation, transformation and metabolic homeostasis. Recently, FOXR2 has been reported to be aberrantly expressed in a variety of cancers and correlated with cancer development. However, the specific role of FOXR2 in thyroid cancer (TC) remains unclear. In this study, we showed that FOXR2 was highly expressed in TC tissues and cell lines. Moreover, down-regulation of FOXR2 inhibited hypoxia-induced reactive oxygen species (ROS) production and migration/invasion of TC cells. We also found that the hedgehog pathway was responsible for the partial mechanisms underlying the inhibitory effect. Taken together, these findings indicated that down-regulation of FOXR2 inhibits hypoxia-driven ROS-induced migration and invasion of TC cells via regulation of the hedgehog pathway. Thus, FOXR2 may hold great potential for TC treatment.

Lesion-Based Evaluation Predicts Treatment Response to Lenvatinib for Radioactive Iodine-Refractory Differentiated Thyroid Cancer: A Korean Multicenter Retrospective Study

Background: Lenvatinib, a tyrosine kinase inhibitor (TKI) recently approved for treating radioactive iodine-refractory differentiated thyroid cancer, has been shown to delay disease progression and provide meaningful benefit for overall survival (OS). However, there is no predictive marker for response to lenvatinib before initiating treatment. We comprehensively analyzed clinical and radiological parameters to predict response to lenvatinib using lesion-based assessments. Methods: Medical records were collected from 67 patients treated with lenvatinib in 11 referral hospitals across Korea from June 2015 to December 2017. Up to 96 measurable lesions, defined as per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, were evaluated serially until progressive disease (PD) occurred, and tumor doubling time (TDT) was calculated based on changes between historical computed tomography (CT) scans and baseline CT scans performed at treatment initiation. Results: Excluding patients with anaplastic thyroid cancer, no thyroidectomy, nontarget lesions only, or treatment periods of <1 month, 57 patients were analyzed, of whom 7 (12.2%) were TKI-naive. The median progression-free survival was 5.1 months (95% confidence interval [CI], 4.4-9.5), the median OS was 19.3 months (95% CI 12.4-not reached), the mean duration of response was 6.0 ± 4.4 months, and the objective response rate was 38%. In lesion-based assessments, 31 lesions (32.2%) with significant tumor shrinkage (complete remission or partial response) were significantly associated with shorter TDT (<12 months; p = 0.02). Patients with rapidly PD with a shorter initial TDT (<6 months) were more likely to respond to lenvatinib (p = 0.03). Patients exposed to lenvatinib at an average of ≥16 mg per day, or who were TKI-naive before treatment with lenvatinib, had a lower risk of progression; however, the risk reduction did not reach statistical significance (daily dosage p = 0.07, TKI exposure p = 0.09). Conclusions: TDT calculations at the beginning of treatment and lesion-based tumor assessment may help identify potential responders to lenvatinib therapy and predict therapeutic responses.

Molecular Alterations in Thyroid Cancer: From Bench to Clinical Practice

Thyroid cancer comprises different clinical and histological entities. Whereas differentiated (DTCs) malignancies are sensitive to radioiodine therapy, anaplastic (ATCs) and medullary (MTCs) tumors do not uptake radioactive iodine and display aggressive features associated with a poor prognosis. Moreover, in a majority of DTCs, disease evolution leads to the progressive loss of iodine sensitivity. Hence, iodine-refractory DTCs, along with ATCs and MTCs, require alternative treatments reflective of their different tumor biology. In the last decade, the molecular mechanisms promoting thyroid cancer development and progression have been extensively studied. This has led to a better understanding of the genomic landscape, displayed by thyroid malignancies, and to the identification of novel therapeutic targets. Indeed, several pharmacological compounds have been developed for iodine-refractory tumors, with four multi-target tyrosine kinase inhibitors already available for DTCs (sorafenib and lenvatinib) and MTCs (cabozantib and vandetanib), and a plethora of drugs currently being evaluated in clinical trials. In this review, we will describe the genomic alterations and biological processes intertwined with thyroid cancer development, also providing a thorough overview of targeted drugs already tested or under investigation for these tumors. Furthermore, given the existing preclinical evidence, we will briefly discuss the potential role of immunotherapy as an additional therapeutic strategy for the treatment of thyroid cancer.

CITED1 contributes to the progression of papillary thyroid carcinoma via the Wnt/β-catenin signaling pathway

Purpose

The incidence rate of thyroid cancer, the most common endocrine malignancy, has increased rapidly over the past 10 years. However, the fundamental molecular mechanisms underlying the malignant progression of thyroid cancer are unclear.

Materials and methods

Firstly, quantitative real-time PCR analysis and Western blot analysis were used to investigate the expression of Cbp/p300 interacting transactivator with Glu/Asp rich carboxy-terminal domain 1 (CITED1) in papillary thyroid carcinoma (PTC) cell lines. Then, we investigated the effects of CITED1 knockdown on cell proliferation, apoptosis, and invasion in in vitro and in vivo models of PTC.

Results

CITED1 was upregulated in PTC cell lines, and CITED1 knockdown significantly suppressed the proliferation, migration, and invasion of K1 cells resulting in a G0/G1 phase block. Furthermore, the silencing of CITED1 significantly promoted cell apoptosis. In the in vivo study, the growth speed and weight of the transplanted tumor were significantly suppressed in nude mice infected with short hairpin RNA targeting CITED1 (CITE1-shRNA) cells. Furthermore, we found that CITED1-shRNA activated Wnt/β-catenin signaling in PTC.

Conclusion

Taken together, our findings suggest that CITED1 knockdown facilitates apoptosis and inhibits proliferation and invasion in K1 cells via the Wnt/β-catenin signaling pathway.

Clinical, pathological and prognostic implications of USP22, SIRT1 and E-cadherin expression in papillary thyroid cancer (PTC) and adjacent non-neoplastic tissue

Introduction

Ubiquitin-specific peptidase 22 (USP22) is described as a stem cell (CSC) marker which is involved in many biological processes, including cancer development, cellular growth and differentiation. Sirtuin 1 (SIRT1) controls a set of biologic processes that range from metabolic homeostasis to cancer. E-cadherin is a calcium-dependent intercellular adhesion molecule. Clinically, USP22, SIRT1 and E-cadherin have been studied to predict prognosis of a variety of cancers but the detailed roles of their expression in papillary thyroid cancer (PTC) and their relation to cancer invasion, metastases and recurrence are still not fully explained.

Aim of the study

To evaluate the expression of USP22, SIRT1 & E-cadherin in PTC tissues and adjacent non-neoplastic thyroid tissue and to correlate their expression with histopathology, clinical, pathological and prognostic parameters of PTC patients.

Methods

We have assessed USP22, SIRT1 & E-cadherin expression using immunohistochemistry in 40 cases with PTC in both malignant tissue and adjacent non-neoplastic tissue, analyzed the relationships between their levels of expression, clinic-pathological parameters, prognosis and survival of patients.

Results

High protein expression levels of both USP22, SIRT1 in addition to low E-cadherin expression in PTC were associated with larger tumors, extra-thyroidal extension, vascular invasion, lymphatic spread (p < 0.001), existence of distant metastases (p = 0.005 & 0.012 respectively), higher stage of the disease (p = 0.012 & 0.042 respectively) and worse five-years overall survival rates (p < 0.001).

Conclusion

Patients having advanced PTC with unfavorable prognosis had high levels of both USP22, SIRT1 in addition to low E-cadherin expression.

Circular RNA EIF6 (Hsa_circ_0060060) sponges miR-144-3p to promote the cisplatin-resistance of human thyroid carcinoma cells by autophagy regulation

Anaplastic thyroid carcinoma (ATC) responds for the majority of death of thyroid carcinoma and often causes chemotherapy resistance. We investigated the influence of circEIF6 (Hsa_circ_0060060) on the cisplatin-sensitivity in papillary thyroid carcinoma (PTC) and ATC cells, and explored its regulation to downstream molecules miR-144-3p and Transforming Growth Factor α (TGF-α). Differentially expressed circRNAs in PTC were analyzed using the GSE93522 data downloaded. Expressions of circEIF6, miR-144-3p, TGF-α, autophagy-related proteins and apoptosis-related proteins were determined using qRT-PCR or western blot. RNA pull-down assay and dual luciferase report assay were applied to reveal the target relationships. Autophagy marker LC3 and cell proliferation marker ki67 were evaluated by immunofluorescence and immunohistochemistry. Cell viability was evaluated with MTT assay and cell apoptosis was assessed by flow cytometric analysis. CircEIF6, could promote autophagy induced by cisplatin, thus inhibiting cell apoptosis and enhancing the resistance of PTC and ATC cells to cisplatin. Has-miR-144-3p was the target of circEIF6 and was regulated by circEIF6. Besides, circEIF6 promoted autophagy by regulating miR-144-3p/TGF-α axis, enhancing the cisplatin-resistance in PTC and ATC cells. CircEIF6 promoted tumor growth by regulating miR-144-3p/TGF-α and circEIF6 knock-down enhanced cisplatin sensitivity in vivo. CircEIF6 could provide a target for therapy of cisplatin-resistance in thyroid carcinoma.

IL6/STAT3 axis mediates resistance to BRAF inhibitors in thyroid carcinoma cells

Thyroid carcinomas (TCs) bearing BRAF mutations represent approximately 26-53% of human thyroid malignancies and, differently from melanomas, are poorly sensitive to BRAF inhibitors (BRAFi), and develop acquired resistance through activation of alternative signaling pathways. A whole-genome gene expression analysis of TC BRAF V600E cells exposed to PLX4032 identified JAK/STAT among the most significantly modulated signaling pathways. Interestingly, both transient exposure and chronic adaptation to PLX4032 resulted in upregulation of IL6/STAT3 axis and this impaired the cytostatic activity of PLX4032. Mechanistically, exposure to PLX4032 enhanced IL6 secretion and this, in turn, was responsible for STAT3 upregulation, activation of ERK signaling and poor sensitivity to BRAF inhibition. Consistently, the dual blockade of STAT3 (by siRNA or pharmacological inhibition) or IL6 signaling (by the humanized anti-human IL6 receptor antibody, tocilizumab) and BRAF (by PLX4032) improved the inhibition of cell cycle progression compared to PLX4032 single agent. These data support the role of IL6/STAT3 signaling pathway in modulating TC cell response to PLX4032 and candidate IL6 targeting as a strategy to improve the activity of PLX4032 in BRAF V600E TC cells.