Vandetanib: opening a new treatment practice in advanced medullary thyroid carcinoma

Precision oncology for RET-related tumors

Aberrant activation of the RET proto-oncogene is implicated in a plethora of cancers. RET gain-of-function point mutations are driver events in multiple endocrine neoplasia 2 (MEN2) syndrome and in sporadic medullary thyroid cancer, while RET rearrangements are driver events in several non-medullary thyroid cancers. Drugs able to inhibit RET have been used to treat RET-mutated cancers. Multikinase inhibitors were initially used, though they showed modest efficacy and significant toxicity. However, new RET selective inhibitors, such as selpercatinib and pralsetinib, have recently been tested and have shown good efficacy and tolerability, even if no direct comparison is yet available between multikinase and selective inhibitors. The advent of high-throughput technology has identified cancers with rare RET alterations beyond point mutations and fusions, including RET deletions, raising questions about whether these alterations have a functional effect and can be targeted by RET inhibitors. In this mini review, we focus on tumors with RET deletions, including deletions/insertions (indels), and their response to RET inhibitors.

Medullary thyroid carcinoma treated with percutaneous ultrasound-guided radiofrequency ablation

PURPOSE

Minimally invasive image-guided thermal ablation has been proposed as alternative to surgery for treatment of benign thyroid nodules and recurrent differentiated thyroid carcinoma. Here, we report for the first time the use of radiofrequency ablation (RFA) in a patient with non-metastatic medullary thyroid carcinoma (MTC) who did not undergo surgery due to high anesthesiological risk.

METHODS AND RESULTS

A 64-year-old woman was referred to our institution for a routine endocrinological visit. No thyroid-related symptoms were present. She had a history of metabolic, cardiovascular and neurological diseases. On clinical examination, a nodular lesion of about 10 mm was palpable in the right thyroid lobe; ultrasonography (US) confirmed the presence of a 13 mm thyroid nodule in the lower pole of the right lobe, that was hypoechoic and with regular margins. Serum calcitonin (Ctn) level was significantly high (647 pg/mL). Fine-needle aspiration (FNA) of the thyroid nodule was negative for malignant cells, but the marked increase of Ctn level in the FNA wash-out fluid confirmed the diagnostic suspicion of MTC. Since patient refused surgery due to high anesthesiological risk, percutaneous US-guided RFA in single session was performed. At 6-months follow-up the serum Ctn level decreased from the initial value of 647 pg/mL, reaching near-normal range (15 pg/mL), and neck ultrasound showed a complete necrosis of the tumour. Afterward, serum Ctn slowly increased to 49 pg/mL at 15-month follow-up. The US performed at 6 and 12 months of follow-up revealed fibrotic tissue in place of the thyroid nodule, without evidence of cervical lymph-node metastases.

CONCLUSIONS

This clinical case suggests that RFA may be effective and safe for treatment of MTC when surgery cannot be performed.

Environmental Enrichment Reverses Tyrosine Kinase Inhibitor-Mediated Impairment Through BDNF-TrkB Pathway

Exposure to an enriched environment (EE) has neuroprotective benefits and improves recovery from brain injury due to, among other, increased neurotrophic factor expression. Through these neurotrophins, important cortical and hippocampal changes occur. Vandetanib acts as a tyrosine kinase inhibitor of cell receptors, among others, the vascular endothelial growth factor receptor (VEGFR). Our aim was to investigate the effectiveness of EE counteracting cognitive and cellular effects after tyrosine kinase receptor blockade. Animals were reared under standard laboratory condition or EE; both groups received vandetanib or vehicle. Visuospatial learning was tested with Morris water maze. Neuronal, interneuronal, and vascular densities were measured by inmunohistochemistry and histochemistry techniques. Quantifications were performed in the hippocampus and in the visual cortex. Brain-derived neurotrophic factor (BDNF), tyrosine kinase B receptor (TrkB), Akt, and Erk were measured by Western blot technique. Vandetanib produces a significant decrease in vascular and neuronal densities and reduction in the expression of molecules involved in survival and proliferation processes such as phospho-Akt/Akt and phospho-Erk/Erk. These results correlated to a cognitive impairment in visuospatial test. On the other hand, animals reared in an EE are able to reverse the negative effects, activating PI3K-AKT and MAP kinase pathways mediated by BDNF-TrkB binding. Present results provide novel and consistent evidences about the usefulness of living in EE as a strategy to improve deleterious effects of blocking neurotrophic pathways by vandetanib and the notable role of the BDNF-TrkB pathway to balance the neurovascular unit and cognitive effects.

A synonymous RET substitution enhances the oncogenic effect of an in-cis missense mutation by increasing constitutive splicing efficiency

Synonymous mutations continue to be filtered out from most large-scale cancer genome studies, but several lines of evidence suggest they can play driver roles in neoplastic disease. We investigated a case of an aggressive, apparently sporadic medullary thyroid carcinoma (MTC) harboring a somatic RET p.Cys634Arg mutation (a known MTC driver). A germ-line RET substitution (p.Cys630=) had also been found but was considered clinically irrelevant because of its synonymous nature. Next generation sequencing (NGS) of the tumor tissues revealed that the RET mutations were in cis. There was no evidence of gene amplification. Expression analysis found an increase of RET transcript in p.Cys630=;p.Cys634Arg patient compared with that found in 7 MTCs harboring p.Cys634 mutations. Minigene expression assays demonstrated that the presence of the synonymous RET mutation was sufficient to explain the increased RET mRNA level. In silico analyses and RNA immunoprecipitation experiments showed that the p.Cys630 = variant created new exonic splicing enhancer motifs that enhanced SRp55 recruitment to the mutant allele, leading to more efficient maturation of its pre-mRNA and an increased abundance of mature mRNA encoding a constitutively active RET receptor. These findings document a novel mechanism by which synonymous mutations can contribute to cancer progression.

Characterization of neuroendocrine tumors in heterozygous mutant MENX rats: a novel model of invasive medullary thyroid carcinoma

Rats affected by the MENX syndrome spontaneously develop multiple neuroendocrine tumors (NETs) including adrenal, pituitary and thyroid gland neoplasms. MENX was initially reported to be inherited as a recessive trait and affected rats were found to be homozygous for the predisposing Cdkn1b mutation encoding p27. We here report that heterozygous MENX-mutant rats (p27+/mut) develop the same spectrum of NETs seen in the homozygous (p27mut/mut) animals but with slower progression. Consequently, p27+/mut rats have a significantly shorter lifespan compared with their wild-type (p27+/+) littermates. In the tumors of p27+/mut rats, the wild-type Cdkn1b allele is neither lost nor silenced, implying that p27 is haploinsufficient for tumor suppression in this model. Transcriptome profiling of rat adrenal (pheochromocytoma) and pituitary tumors having different p27 dosages revealed a tissue-specific, dose-dependent effect of p27 on gene expression. In p27+/mut rats, thyroid neoplasms progress to invasive and metastatic medullary thyroid carcinomas (MTCs) accompanied by increased calcitonin levels, as in humans. Comparison of expression signatures of late-stage vs early-stage MTCs from p27+/mut rats identified genes potentially involved in tumor aggressiveness. The expression of a subset of these genes was evaluated in human MTCs and found to be associated with aggressive RET-M918T-positive tumors. Altogether, p27 haploinsufficiency in MENX rats uncovered a novel, representative model of invasive and metastatic MTC exploitable for translational studies of this often aggressive and incurable cancer.

Novel therapeutic clues in thyroid carcinomas: The role of targeting cancer stem cells

Thyroid carcinomas (TCs), the most common endocrine tumors, represent the eighth most common cancer diagnosed worldwide in both women and men. To treat these malignancies, several drugs are now available and a number of novel ones have been enrolling in clinical trials, addressing both oncogenic pathways in cancer cells and angiogenic pathways in tumor endothelial cells. However, their use is not devoid of serious toxicities and their efficacy is limited, being dependent on carcinoma typology and the occurrence of acquired resistance. Accordingly, it is time to recast therapeutic strategies against these types of tumors to get to newer and fully effective drugs. In this perspective, latest findings demonstrate that cancer stem cells (CSCs) represent a challenging target to strike. They possess core traits of self-renewal and differentiation, being resistant to the effects of chemotherapy and radiation and playing a key role in mediating metastasis. Therefore, basic molecular elements sustaining both development of thyroid cancer stem cells and their residence in the stemness condition represent a set of innovative and still unexplored targets to address. In this review, a thorough literature survey has been accomplished, to take stock of mechanisms governing thyroid carcinomas and to point out both their currently available treatments and the novel forthcoming ones. Pubmed, Scifinder and ClinicalTrials.gov were exploited as research applications and registry database, respectively. Original articles, reviews, and editorials published within the last ten years, as well as open clinical investigations in the field, were analyzed to suggest new exciting therapeutic opportunities for people affected by TCs.

Vandetanib induces a marked anti-tumor effect and amelioration of ectopic Cushing's syndrome in a medullary thyroid carcinoma patient

A 55-year-old woman diagnosed with sporadic MTC underwent total thyroidectomy 20 years ago. After the first surgery, elevated calcitonin levels in parallel with local disease persistence were noted and therefore she underwent repeated neck dissections. During follow-up, multiple foci of metastatic disease were noted in the neck and mediastinal lymph nodes, lungs and bones; however, the disease had an indolent course for a number of years, in parallel with a calcitonin doubling time of more than two years and without significant symptoms. During a routine follow-up visit 2 years ago, findings suggestive of Cushing’s syndrome were observed on physical examination. The biochemical evaluation demonstrated markedly elevated serum calcitonin level, in parallel with lack of cortisol suppression after an overnight 1 mg dexamethasone suppression test, lack of cortisol and ACTH suppression after high-dose IV dexamethasone 8 mg, elevated plasma ACTH up to 79 pg/mL (normal <46 pg/mL) and elevated 24-h urinary free cortisol up to 501 µg/24 h (normal 9–90 µg/24 h). After a negative pituitary MRI, she underwent IPSS, which was compatible with EAS. Whole-body CT demonstrated progressive disease at most of the tumor sites. Treatment with vandetanib at a dosage of 200 mg/day was commenced. The patient showed a significant, rapid and consistent clinical improvement already after two months of treatment, in parallel with biochemical improvement, whereas a decrease in tumor size was demonstrated on follow-up CT.

Ret function in muscle stem cells points to tyrosine kinase inhibitor therapy for facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) involves sporadic expression of DUX4, which inhibits myogenesis and is pro-apoptotic. To identify target genes, we over-expressed DUX4 in myoblasts and found that the receptor tyrosine kinase Ret was significantly up-regulated, suggesting a role in FSHD. RET is dynamically expressed during myogenic progression in mouse and human myoblasts. Constitutive expression of either RET9 or RET51 increased myoblast proliferation, whereas siRNA-mediated knockdown of Ret induced myogenic differentiation. Suppressing RET activity using Sunitinib, a clinically-approved tyrosine kinase inhibitor, rescued differentiation in both DUX4-expressing murine myoblasts and in FSHD patient-derived myoblasts. Importantly, Sunitinib also increased engraftment and differentiation of FSHD myoblasts in regenerating mouse muscle. Thus, DUX4-mediated activation of Ret prevents myogenic differentiation and could contribute to FSHD pathology by preventing satellite cell-mediated repair. Rescue of DUX4-induced pathology by Sunitinib highlights the therapeutic potential of tyrosine kinase inhibitors for treatment of FSHD.

DOI:http://dx.doi.org/10.7554/eLife.11405.001

Multilayer OMIC Data in Medullary Thyroid Carcinoma Identifies the STAT3 Pathway as a Potential Therapeutic Target in RETM918T Tumors

Purpose: Medullary thyroid carcinoma (MTC) is a rare disease with few genetic drivers, and the etiology specific to each known susceptibility mutation remains unknown. Exploiting multilayer genomic data, we focused our interest on the role of aberrant DNA methylation in MTC development.Experimental Design: We performed genome-wide DNA methylation profiling assessing more than 27,000 CpGs in the largest MTC series reported to date, comprising 48 molecularly characterized tumors. mRNA and miRNA expression data were available for 33 and 31 tumors, respectively. Two human MTC cell lines and 101 paraffin-embedded MTCs were used for validation.Results: The most distinctive methylome was observed for RET^M918T-related tumors. Integration of methylation data with mRNA and miRNA expression data identified genes negatively regulated by promoter methylation. These in silico findings were confirmed in vitro for PLCB2, DKK4, MMP20, and miR-10a, -30a, and -200c. The mutation-specific aberrant methylation of PLCB2, DKK4, and MMP20 was validated in 25 independent MTCs by bisulfite pyrosequencing. The methylome and transcriptome data underscored JAK/Stat pathway involvement in RET^M918T MTCs. Immunostaining [immunohistochemistry (IHC)] for the active form of signaling effector STAT3 was performed in a series of 101 MTCs. As expected, positive IHC was associated with RET^M918T-bearing tumors (P < 0.02). Pharmacologic inhibition of STAT3 activity increased the sensitivity to vandetanib of the RET^M918T-positive MTC cell line, MZ-CRC-1.Conclusions: Multilayer OMIC data analysis uncovered methylation hallmarks in genetically defined MTCs and revealed JAK/Stat signaling effector STAT3 as a potential therapeutic target for the treatment of RET^M918T MTCs. Clin Cancer Res; 23(5); 1334-45. ©2016 AACR.

Management of hereditary medullary thyroid carcinoma

Hereditary medullary thyroid carcinoma (MTC) represents up to one-third of MTC cases and includes multiple endocrine neoplasia syndrome type 2A (and its variant familial MTC) and 2B. The aim of this paper is to provide an overview of the disease focusing on the management of hereditary MTC patients, who have already developed tumor, as well as discuss the recommended approach for asymptomatic family members carrying the same mutation. A PubMed search was performed to review recent literature on diagnosis, genetic testing, and surgical and medical management of hereditary MTC. The wide use of genetic testing for RET mutations has markedly influenced the course of hereditary MTC. Prophylactic thyroidectomy of RET carriers at an early age eliminates the risk of developing MTC later in life. Pre-operative staging is a strong prognostic factor in patients, who have developed MTC. The use of recently approved tyrosine kinase inhibitors (vandetanib, cabozantinib) holds promising results for the treatment of unresectable, locally advanced, and progressive metastatic MTC. Genetic testing of the RET gene is a powerful tool in the diagnosis and prognosis of MTC. Ongoing research is expected to add novel treatment options for patients with advanced, progressive disease.

The molecular classification of hereditary endocrine diseases

Hereditary endocrine diseases are an important group of diseases with great heterogeneity. The current classification for hereditary endocrine disease is mostly based upon anatomy, which is helpful for pathophysiological interpretation, but does not address the pathogenic variability associated with different underlying genetic causes. Identification of an endocrinopathy-associated genetic alteration provides evidence for differential diagnosis, discovery of non-classical disease, and the potential for earlier diagnosis and targeted therapy. Molecular diagnosis should be routinely applied when managing patients with suspicion of hereditary disease. To enhance the accurate diagnosis and treatment of patients with hereditary endocrine diseases, we propose categorization of endocrine diseases into three groups based upon the function of the mutant gene: cell differentiation, hormone synthesis and action, and tumorigenesis. Each category was further grouped according to the specific gene function. We believe that this format would facilitate practice of precision medicine in the field of hereditary endocrine diseases.

PI3K/Akt/mTOR signaling in medullary thyroid cancer: a promising molecular target for cancer therapy

The phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is a central hub for the regulation of cell proliferation, apoptosis, cell cycle, metabolism, and angiogenesis. Several studies have recently suggested that the PI3K/Akt/mTOR signaling pathway is implicated in the pathogenesis and progression of neuroendocrine tumors. Medullary thyroid cancer (MTC) is a neuroendocrine tumor developing from the C cells of the thyroid. Mutations in the RET proto-oncogene are involved in the pathogenesis of several forms of MTC. The deregulation of the PI3K/Akt/mTOR pathway seems to contribute to the tumorigenic activity of RET proto-oncogene mutations. Targeting this pathway through specific inhibitors at simple or multiple sites may represent an attractive potential therapeutic approach for patients with advanced MTCs. The aim of this review is to examine the role of the PI3K/Akt/mTOR pathway in the development and progression of MTC and the new therapeutic options that target this signaling pathway.

Overexpression of genes involved in miRNA biogenesis in medullary thyroid carcinomas with RET mutation

Abnormal expression of non-coding micro RNA (miRNA) has been described in medullary thyroid carcinoma (MTC). Expression of genes encoding factors involved in miRNA biogenesis results often deregulated in human cancer and correlates with aggressive clinical behavior. In this study, expression of four genes involved in miRNA biogenesis (DICER, DROSHA, DCGR8, and XPO5) was investigated in 54 specimens of MTC. Among them, 33 and 13 harbored RET and RAS mutations, respectively. DICER, DGCR8, and XPO5 mRNA levels were significantly overexpressed in MTC harboring RET mutations, in particular, in the presence of RET634 mutation. When MTCs with RET and RAS mutations were compared, only DGCR8 displayed a significant difference, while MTCs with RAS mutations did not show significant differences with respect to non-mutated tumors. We then attempted to correlate expression of miRNA biogenesis genes with tumor aggressiveness. According to the TNM status, MTCs were divided in two groups and compared (N0 M0 vs. N1 and/or M1): for all four genes no significant difference was detected. Cell line experiments, in which expression of a RET mutation is silenced by siRNA, suggest the existence of a causal relationship between RET mutation and overexpression of DICER, DGCR8, and XPO5 genes. These findings demonstrate that RET- but not RAS-driven tumorigenic alterations include abnormalities in the expression of some important genes involved in miRNA biogenesis that could represent new potential markers for targeted therapies in the treatment of RET-mutated MTCs aimed to restore the normal miRNA expression profile.

VEGF, VEGFR3, and PDGFRB protein expression is influenced by RAS mutations in medullary thyroid carcinoma

BACKGROUND

Tyrosine kinase inhibitors (TKIs) have achieved remarkable clinical results in medullary thyroid carcinoma (MTC) patients. However, the considerable variability in patient response to treatment with TKIs remains largely unexplained. There is evidence that it could be due, at least in part, to alterations in genes associated with the disease via their effect on the expression of TKI targets. The objective of this study was to evaluate the influence of RAS mutations on the expression levels in MTC tumors of eight key TKI target proteins.

METHODS

We assessed by immunohistochemistry the expression of EGFR, KIT, MET, PDGFRB, VEGF, VEGFR1, VEGFR2, and VEGFR3 in a series of 84 primary MTC tumors that had previously been molecularly characterized, including 14 RAS-positive, 18 RET(M918T)-positive, and 24 RET(C634)-positive tumors, as well as 15 wild-type tumors with no mutations in the RET or RAS genes.

RESULTS

In contrast to RET-positive tumors, RAS-positive tumors expressed neither PDGFRB nor MET (p=0.0060 and 0.047, respectively). Similarly, fewer RAS-positive than RET-related tumors expressed VEGFR3 (p=0.00062). Finally, wild-type tumors expressed VEGF more often than both RAS- and RET-positive tumors (p=0.0082 and 0.011, respectively).

CONCLUSIONS

This is the first study identifying that the expression of TKI targets differs according to the presence of RAS mutations in MTC. This information could potentially be used to select the most beneficial TKI treatment for these patients.

Epigenetic-related gene expression profile in medullary thyroid cancer revealed the overexpression of the histone methyltransferases EZH2 and SMYD3 in aggressive tumours

Epigenetic control of gene expression plays a major influence in the development and progression of many cancer types. Aim of the present study was to investigate the expression of epigenetic regulators in a large cohort of medullary thyroid carcinomas (MTC), correlating the data with the clinical outcome and mutational status of the patients. Taqman Low Density Arrays (TLDAs) were used to analyze expression levels of several genes involved in the epigenetic control of transcription in a series of 54 MTCs. The patients cohort included 13 familial MTCs and 41 sporadic forms; 33 hosted a RET mutation and 13 a RAS somatic mutation. The expression profiling revealed in the more aggressive diseases (i.e. occurrence of metastases; persistent disease; disease-related death) a significant increase of EZH2 and SMYD3 gene expression. The increased levels of EZH2 and SMYD3 did not correlate significantly with mutational status of RET or RAS genes. Thus, the histone methyltransferases EZH2 and SMYD3 mRNA expression may represent useful prognostic biomarkers tailoring the most appropriate follow-up and timing of therapeutic approaches.