Investigating the expression and promoter methylation of RET gene in patients with medullary thyroid cancer with unmutated RET

RET splice site variants in medullary thyroid carcinoma

Introduction: Medullary thyroid carcinoma (MTC) is an aggressive cancer that is often caused by driver mutations in RET. Splice site variants (SSV) reflect changes in mRNA processing, which may alter protein function. RET SSVs have been described in thyroid tumors in general but have not been extensively studied in MTC. Methods: The prevalence of RET SSVs was evaluated in 3,624 cases with next generation sequence reports, including 25 MTCs. Fisher exact analysis was performed to compare RET SSV frequency in cancers with/without a diagnosis of MTC. Results: All 25 MTCs had at least one of the two most common RET SSVs versus 0.3% of 3,599 cancers with other diagnoses (p < 0.00001). The 11 cancers with non-MTC diagnoses that had the common RET SSVs were 4 neuroendocrine cancers, 4 non-small cell lung carcinomas, 2 non-MTC thyroid cancers, and 1 melanoma. All 25 MTCs analyzed had at least one of the two most common RET SSVs, including 4 with no identified mutational driver. Discussion: The identification of RET SSVs in all MTCs, but rarely in other cancer types, demonstrates that these RET SSVs distinguish MTCs from other cancer types. Future studies are needed to investigate whether these RET SSVs play a pathogenic role in MTC.

Comprehensive DNA Methylation Profiling of Medullary Thyroid Carcinoma: Molecular Classification, Potential Therapeutic Target, and Classifier System

PURPOSE

Medullary thyroid carcinoma (MTC) presents a distinct biological context from other thyroid cancers due to its specific cellular origin. This heterogeneous and rare tumor has a high prevalence of advanced diseases, making it crucial to address the limited therapeutic options and enhance complex clinical management. Given the high clinical accessibility of methylation information, we construct the largest MTC methylation cohort to date.

EXPERIMENTAL DESIGN

Seventy-eight fresh-frozen MTC samples constituted our methylation cohort. The comprehensive study process incorporated machine learning, statistical analysis, and in vitro experiments.

RESULTS

Our study pioneered the identification of a three-class clustering system for risk stratification, exhibiting pronounced epigenomic heterogeneity. The elevated overall methylation status in MTC-B, combined with the "mutual exclusivity" of hypomethylated sites displayed by MTC-A and MTC-C, distinctively characterized the MTC-specific methylation pattern. Integrating with the transcriptome, we further depicted the features of these three clusters to scrutinize biological properties. Several MTC-specific aberrant DNA methylation events were emphasized in our study. NNAT expression was found to be notably reduced in poor-prognostic MTC-C, with its promoter region overlapping with an upregulated differentially methylated region. In vitro experiments further affirmed NNAT's therapeutic potential. Moreover, we built an elastic-net logistic regression model with a relatively high AUC encompassing 68 probes, intended for future validation and systematic clinical application.

CONCLUSIONS

Conducting research on diseases with low incidence poses significant challenges, and we provide a robust resource and comprehensive research framework to assist in ongoing MTC case inclusion and facilitate in-depth dissection of its molecular biological features.

Molecular Basis and Natural History of Medullary Thyroid Cancer: It is (Almost) All in the RET

Medullary thyroid cancer (MTC) is a rare disease, which can be either sporadic (roughly 75% of cases) or genetically determined (multiple endocrine neoplasia type 2, due to REarranged during Transfection RET germline mutations, 25% of cases). Interestingly, RET pathogenic variants (mainly M918T) have also been reported in aggressive forms of sporadic MTC, suggesting the importance of RET signalling pathways in the pathogenesis of MTC. The initial theory of RET codon-related MTC aggressiveness has been recently questioned by studies suggesting that this would only define the age at disease onset rather than the aggressiveness of MTC. Other factors might however impact the natural history of the disease, such as RET polymorphisms, epigenetic factors, environmental factors, MET (mesenchymal-epithelial transition) alterations, or even other genetic alterations such as RAS family (HRAS, KRAS, NRAS) genetic alterations. This review will detail the molecular bases of MTC, focusing on RET pathways, and the potential mechanisms that explain the phenotypic intra- and interfamilial heterogeneity.

Exploring the application value of pro-gastrin-releasing peptide in the clinical diagnosis and surgical treatment of medullary thyroid carcinoma

OBJECTIVE

To investigate the relationship between pro-gastrin-releasing peptide (ProGRP) and the clinical characteristics of patients with medullary thyroid carcinoma (MTC) and the value of ProGRP in surgical treatment monitoring.

PATIENTS AND METHODS

A total of 347 patients with MTC and non-MTC malignant and benign thyroid diseases were enrolled. The concentrations of neuron-specific enolase (NSE), carcinoembryonic antigen (CEA), calcitonin (CT), and ProGRP were determined by Elecsys® assays. The NSE, CEA, CT, and ProGRP levels in different thyroid disease groups were compared, and ProGRP levels in different clinicopathological feature groups pre and postoperatively were further compared.

RESULTS

The CT, CEA, NSE, and ProGRP levels were upregulated in the MTC group compared to those in the non-MTC malignant and benign thyroid disease groups. The area under the receiver operating characteristic curve (AUC) of ProGRP for the diagnosis of MTC was 0.832(0.787-0.871), similar to that of CT and CEA. The sensitivity and specificity were 71.4% and 92.7%, respectively, and the optimal cut-off value was 61.8 pg/mL. The AUC of ProGRP combined with CT or CEA for the diagnosis of MTC was 0.933 (0.900-0.958) and 0.922 (0.886-0.949), respectively, which were higher than those of a single index. ProGRP levels were higher in patients with lymph nodes and distant metastases than in patients without metastases. The postoperative level of ProGRP was lower than that before treatment.

CONCLUSION

ProGRP is comparable to CEA and CT as an MTC biomarker with broad prospects. It has potential application value in the progression of MTC assessment and the evaluation of surgical intervention effects.

MANAGEMENT OF ENDOCRINE DISEASE: Medullary thyroid cancer: from molecular biology and therapeutic pitfalls to future targeted treatment perspectives

During the last decades, knowledge of the molecular biology in medullary thyroid carcinoma (MTC) and specifically on the role of rearranged during transfection (RET)-activating mutations in tumorigenesis has led to the evolution of novel targeted therapies, mainly tyrosine kinase inhibitors (TKIs). Vandetanib and cabozantinib have been approved for the management of metastatic progressive MTC. Two novel, highly selective RET inhibitors, selpercatinib and pralsetinib, have recently been approved for the treatment of RET-mutant MTCs and RET-fusion differentiated thyroid cancer. The administration of targeted therapies in MTC patients has changed the therapeutic strategies; however, in the majority of cases, there are no real data showing an improvement of prognosis by TKIs in MTC. Drug resistance remains the main reason for treatment failure. Thus, the understanding of the molecular landscape of tumorigenesis and the mechanisms underlying resistance to targeted therapies is of paramount importance for the further development of more efficient therapies for MTC. The present review focuses on the molecular pathways implicated in MTC tumorigenesis, the approved targeted therapies, the tumoral escape mechanisms, as well as the future perspectives for targeted therapy.

Gas chromatography-mass spectrometry-based untargeted metabolomics reveals metabolic perturbations in medullary thyroid carcinoma

Medullary thyroid cancer (MTC) is a rare tumor that arises from parafollicular cells within the thyroid gland. The molecular mechanism underlying MTC has not yet been fully understood. Here, we aimed to perform plasma metabolomics profiling of MTC patients to explore the perturbation of metabolic pathways contributing to MTC tumorigenesis. Plasma samples from 20 MTC patients and 20 healthy subjects were obtained to carry out an untargeted metabolomics by gas chromatography–mass spectrometry. Multivariate and univariate analyses were employed as diagnostic tools via MetaboAnalyst and SIMCA software. A total of 76 features were structurally annotated; among them, 13 metabolites were selected to be differentially expressed in MTC patients compared to controls (P < 0.05). These metabolites were mainly associated with the biosynthesis of unsaturated fatty acids and amino acid metabolisms, mostly leucine, glutamine, and glutamate, tightly responsible for tumor cells' energy production. Moreover, according to the receiver operating characteristic curve analysis, metabolites with the area under the curve (AUC) value up to 0.90, including linoleic acid (AUC = 0.935), linolenic acid (AUC = 0.92), and leucine (AUC = 0.948) could discriminate MTC from healthy individuals. This preliminary work contributes to existing knowledge of MTC metabolism by providing evidence of a distinctive metabolic profile in MTC patients relying on the metabolomics approach.

The Cross-Talk between Polyphenols and the Target Enzymes Related to Oxidative Stress-Induced Thyroid Cancer

The most serious hallmark step of carcinogenesis is oxidative stress, which induces cell DNA damage. Although in normal conditions ROS are important second messengers, in pathological conditions such as cancer, due to imbalanced redox enzyme expression, oxidative stress can occur. Recent studies with firmly established evidence suggest an interdependence between oxidative stress and thyroid cancer based on thyroid hormone synthesis. Indeed, a reduced antioxidant defense system might play a part in several steps of progression in thyroid cancer. Based on studies that have been conducted previously, future drug designs for targeting enzymatic ROS sources, as a single agent or in combination, have to be tested. Polyphenols represent the potential for modulating biological events in thyroid cancer, including antioxidative activity. Targeting enzymatic ROS sources, without affecting the physiological redox state, might be an important purpose. As regards the underlying chemopreventive mechanisms of natural compounds that have been discussed in other cancer models, the confirmation of the influence of polyphenols on thyroid cancer is inconclusive and rarely available. Therefore, there is a need for further scientific investigations into the features of the antioxidative effects of polyphenols on thyroid cancer. The current review illustrates the association between some polyphenols and the key enzymes that take place in oxidation reactions in developing thyroid cancer cells. This review gives the main points of the enzymatic ROS sources act and redox signaling in normal physiological or pathological contexts and supplies a survey of the currently available modulators of TPO, LOX, NOX, DUOX, Nrf2, and LPO derived from polyphenols.

Higher RET Gene Expression Levels Do Not Represent anAlternative RET Activation Mechanism in Medullary Thyroid Carcinoma

This study was designed to investigate whether RET (rearranged during transfection) mRNA over-expression could be considered an alternative driver event for the development of medullary thyroid carcinoma (MTC), and if different RET isoforms could play a role in MTC tumorigenesis. Eighty-three MTC patients, whose mutational profile was previously identified by next-generation sequencing (NGS) IONS5, were included in this study. Expression analysis was performed by the quantitative reverse transcription-polymerase chain reaction technique. RET expression levels were found to be significantly higher in cases with RET somatic mutations than in cases that were negative for RET somatic mutations (p = 0.003) as well as in cases with a somatic mutation, either in RET or RAS than in cases negative for both these mutations (p = 0.01). All cases were positive for the RET51 isoform expression while only 72/83 (86.7%) were positive for RET9 isoform expression. A statistically significant higher expression of the RET51 isoform was found in cases positive for RET somatic mutation than in cases either positive for RAS mutation (p = 0.0006) or negative for both mutations (p = 0.001). According to our data, RET gene over-expression does not play a role in MTC tumorigenesis, neither as an entire gene or as an isoform. At variance, the RET gene, and in particular the RET51 isoform, is expressed higher in RET mutated cases. On the basis of these results we can hypothesize that the overexpression of RET, and in particular of RET51, could potentiate the transforming activity of mutated RET, making these cases more aggressive.

Hereditary Medullary Thyroid Carcinoma: Genotype, Phenotype and Outcomes in a North Indian Cohort

BACKGROUND

Aggressiveness of hereditary medullary thyroid carcinoma (hMTC) has been conventionally described to correlate with American Thyroid Association (ATA) risk groups based on RET mutations. Recent evidence increasingly contradicts this notion. We studied the RET genotype and its correlation with disease phenotype and survival outcomes in a cohort of hMTC patients.

METHODS

In a retrospective cohort of 55 hMTC patients from 23 families treated at a north Indian tertiary care institute over 15-years, RET genotype was correlated with disease phenotype (clinical, biochemical, and pathological attributes) and outcomes in terms of biochemical cure (normalization of serum calcitonin), structural cure, overall survival (OS) and disease specific survival (DSS).

RESULTS

Forty-nine patients had Multiple Endocrine Neoplasia (MEN)-type 2A syndrome, 02 had MEN-2B, and 4 had familial MTC. Two patients belonged to highest ATA risk, 41 to high-risk, and 12 to moderate risk categories. Age of the patients or stage of disease at presentation did not differ significantly between the ATA risk groups. Though the baseline serum calcitonin was significantly higher in highest risk category, the biochemical cure rates were not significantly different. At a median follow up of 48 months (Inter-quartile range 18-84, range 12-192) structural cure rates in ATA moderate and high risk groups were significantly higher than highest risk group (p = 0.04). No significant difference in OS between the three ATA groups of hMTC among the patients who underwent surgical treatment was observed (p = 0.098).

CONCLUSIONS

The ATA moderate and high risk groups have better structural cure rates compared to ATA highest risk group. The biochemical cure and overall survival rates did not significantly differ between ATA risk-groups, and were impacted by the disease stage at presentation. The current ATA risk-groups do not reliably predict the outcomes in terms of biochemical cure and survival in hMTC patients.

Role of tissue and circulating microRNAs and DNA as biomarkers in medullary thyroid cancer

Medullary thyroid carcinoma (MTC) is a rare neuroendocrine tumor comprising hereditary or sporadic form with frequent mutations in the rearranged during transfection (RET) or RAS genes. Diagnosis is based on the presence of thyroid tumor mass with altered levels of calcitonin (Ctn) and carcinoembryonal antigen (CEA) in the serum and/or in the cytological smears from fine needle aspiration biopsies. Treatment consists of total thyroidectomy, followed by tyrosine kinase inhibitors (TKi) in case of disease persistence. During TKi treatment, Ctn and CEA levels can fluctuate regardless of tumor volume, metastasis or response to therapy. Research for more reliable non-invasive biomarkers in MTC is still underway. In this context, circulating nucleic acids, namely circulating microRNAs (miRNAs) and cell free DNA (cfDNA), have been evaluated by different research groups. Aiming to shed light on whether miRNAs and cfDNA are suitable as MTC biomarkers we searched three different databases, PubMed, Scopus, WOS and reviewed the literature. We classified 83 publications fulfilling our search criteria and summarized the results. We report data on miRNAs and cfDNA that can be evaluated for validation in independent studies and clinical application.