Ponatinib is a potent inhibitor of wild-type and drug-resistant gatekeeper mutant RET kinase

RET kinase is aberrantly activated in thyroid cancers and in rare cases of lung and colon cancer, and has been validated as a molecular target in these tumors. Vandetanib was recently approved for the treatment of medullary thyroid cancer. However, vandetanib is ineffective in vitro against RET mutants carrying bulky aminoacids at position 804, the gatekeeper residue, similarly to drug-resistant BCR-ABL mutants in chronic myeloid leukemia. Ponatinib is a multi-target kinase inhibitor that was recently approved for treatment-refractory Philadelphia-positive leukemia. We show here potent inhibition of oncogenic RET by ponatinib, including the drug-insensitive V804M/L mutants. Ponatinib inhibited the growth of RET+ and BCR-ABL+ cells with similar potency, while not affecting RET-negative cells. Both in biochemical and in cellular assays ponatinib compared favorably with known RET inhibitors, such as vandetanib, cabozantinib, sorafenib, sunitinib and motesanib, used as reference compounds. We suggest that ponatinib should be considered for the treatment of RET+ tumors, in particular those expressing vandetanib-resistant V804M/L mutations.

The clinical spectrum of RET proto-oncogene mutations in codon 790

OBJECTIVE

Due to a strong genotype-phenotype correlation, the timing of prophylactic thyroidectomy in rearranged during transfection (RET) gene mutation carriers is usually dictated by genetic analysis.

SUBJECTS AND METHODS

We report a nationwide retrospective study of the clinical data of 77 French patients from 19 families with a mutation in codon 790 of the RET proto-oncogene.

RESULTS

The average age at diagnosis was 35.6 years ± 20.5. Thirty-nine patients were women. Fifty-five patients underwent operations for the treatment of medullary thyroid carcinoma (MTC) at the mean age of 38 years (4-82 years). The mean follow-up duration was 89 months. TNM staging was as follows: T0NxMx in 19, TxNxMx in 1, T1NxMx in 22, T1N1Mx in 8, T2N1Mx in 1 and T3N1Mx in four patients. In the T1/x-Nx group, 96% were considered cured after surgery. In the N1 group (n=13), six patients had multifocal disease and five patients were cured. Age and gender were not significant predictors of remission. Twenty-two patients did not undergo an operation (age 1.5-78 years); among them, 11 patients had a mean basal calcitonin (CT) level of 9.8 pg/ml (2-24) after 53 months of follow-up. One patient had been operated on for phaeochromocytoma (PHEO), and their CT level remained normal for 262 months.

CONCLUSIONS

This study confirms that RET 790 mutation is associated with a non-aggressive form of multiple endocrine neoplasia type 2, as 28% of the patients were followed up without thyroidectomy, 25% had been thyroidectomised with no tumour being detected and even patients with MTC had slow-evolving disease. Moreover, only one patient had PHEO, and no-one had primary hyperparathyroidism.

Medullary thyroid cancer secreting carbohydrate antigen 19-9 (Ca 19-9): a fatal case report

BACKGROUND

During follow-up for patients with medullary thyroid cancer (MTC), the levels of serum calcitonin and carcinoembryonic antigen are important, and the doubling time of these biomarkers significantly correlates with disease progression. Other antigens are present in tumor tissue and the sera of patients with MTC, but there are scarce published data on the serum levels of carbohydrate antigen 19-9 (Ca 19-9), a tumor marker primarily used for the diagnosis and follow-up of pancreatic and gastrointestinal neoplasias. Recently, the case of a 56-year-old woman with multiple endocrine neoplasia type 2B with high serum levels of Ca 19-9 was reported; this patient experienced rapid disease progression that led to her death.

CASE PRESENTATION

A 28-year-old man was referred to the Department of Endocrinology of the University Hospital of Pisa with suspected MTC with laterocervical lymph node metastasis, a single liver lesion (10 mm), several bone metastases, and bilateral pheochromocytomas. RET genetic testing revealed a germline Cys634Arg mutation. During the hospitalization, the carcinoembryonic antigen and Ca 19-9 levels increased while the calcitonin concentration remained stable; despite the apparent stability of the lesions, the condition of the patient worsened rapidly and resulted in death.

CONCLUSIONS

High levels of serum Ca 19-9 could be considered a marker of the dedifferentiation of MTC and disease aggressiveness, but additional data on the association between Ca 19-9 and advanced MTC are required to confirm this hypothesis.

Assessing RET/PTC in thyroid nodule fine-needle aspirates: the FISH point of view

RET/PTC rearrangement and BRAF(V600E) mutation are the two prevalent molecular alterations associated with papillary thyroid carcinoma (PTC), and their identification is increasingly being used as an adjunct to cytology in diagnosing PTC. However, there are caveats associated with the use of the molecular approach in fine-needle aspiration (FNA), particularly for RET/PTC, that should be taken into consideration. It has been claimed that a clonal or sporadic presence of this abnormality in follicular cells can distinguish between malignant and benign nodules. Nevertheless, the most commonly used PCR-based techniques lack the capacity to quantify the number of abnormal cells. Because fluorescence in situ hybridization (FISH) is the most sensitive method for detecting gene rearrangement in a single cell, we compared results from FISH and conventional RT-PCR obtained in FNA of a large cohort of consecutive patients with suspicious nodules and investigated the feasibility of setting a FISH-FNA threshold capable of distinguishing non-clonal from clonal molecular events. For this purpose, a home brew break-apart probe, able to recognize the physical breakage of RET, was designed. While a ≥3% FISH signal for broken RET was sufficient to distinguish nodules with abnormal follicular cells, only samples with a ≥6.8% break-apart FISH signal also exhibited positive RT-PCR results. On histological analysis, all nodules meeting the ≥6.8% threshold proved to be malignant. These data corroborate the power of FISH when compared with RT-PCR in quantifying the presence of RET/PTC in FNA and validate the RT-PCR efficiency in detecting clonal RET/PTC alterations.

Thyroid cancer and co-occurring RET mutations in Hirschsprung disease

The objective of this study was to assess the occurrence of thyroid cancer and co-occurring RET mutations in a population-based cohort of adult Hirschsprung disease (HD) patients. All 156 patients operated for HD in a tertiary center during 1950-1986 were followed for thyroid malignancies up to 2010 through the nationwide Finnish Cancer Registry. Ninety-one individuals participated in clinical and genetic screening, which included serum calcitonin and thyroid ultrasound (US) with cytology. Exons 10, 11, 13, and 16 were sequenced in all, and all exons of RET in 43 of the subjects, including those with thyroid cancer, RET mutations, suspicious clinical findings, and familial or long-segment disease. Through the cancer registry, two cases (aged 35 and 37 years) of medullary thyroid cancer (MTC) were observed; the incidence for MTC was 340-fold (95% CI 52-1600) compared with average population. These individuals had C611R and C620R mutations in exon 10. One papillary thyroid cancer without RET mutations was detected by clinical screening. Four subjects (aged 31-50 years) with co-occurring RET mutations in exons 10 (C609R; n=1) and 13 (Y791F, n=3) had sporadic short-segment HD with normal thyroid US and serum calcitonin. Three novel mutations and five single-nucleotide polymorphisms were found outside exons 10 and 13 without associated signs of thyroid cancer. MTC-associated RET mutations were restricted to exons 10 and 13 affecting ∼5% of unselected adults with HD. Clinical thyroid assessment did not improve accuracy of genetic screening, which should not be limited to patients with familial or long-segment disease.

Influence of RET mutations on the expression of tyrosine kinases in medullary thyroid carcinoma

The therapeutic options for patients with metastatic medullary thyroid carcinoma (MTC) have recently increased due to the development of tyrosine kinase inhibitors (TKIs), some of which have achieved remarkable clinical responses in MTC patients. However, the molecular basis for the large variability in TKI responses is unknown. In this exploratory study, we investigated the expression of eight key TKI target proteins (EGFR, KIT, MET, PDGFRB, VEGF (VEGFA), VEGFR1 (FLT1), VEGFR2 (KDR), and VEGFR3 (FLT4)) by immunohistochemistry in 103 molecularly characterized MTC samples and identified the associated clinical and molecular features. A number of MTC samples exhibited a high expression of VEGFR2 and VEGFR3, which were overexpressed in 57 and 43% of the MTC samples respectively. VEGFR1, PDGFRB, VEGF, KIT, and MET were present in 34-20% of the cases, while EGFR was highly expressed in only 10% of the MTC samples. Some proteins exhibited large differences in expression between sporadic and familial cases, suggesting that different RET mutations may be associated with the immunohistochemical profiles. MTC samples with the C634 RET mutation exhibited a higher expression of VEGFR3 and KIT than the M918T RET-mutated and non-mutated RET tumor samples (P=0.005 and P=0.007 respectively) and a lower expression of VEGFR1 (P=0.04). Non-mutated RET MTC cases exhibited a lower expression of PDGFRB (P=0.04). Overall, this is the first study, to our knowledge, to show that multiple TKI targets are highly expressed in a subset of MTCs, suggesting that molecular stratification of patients may have the potential to improve TKI therapies for MTC.

Genes of detoxification are important modulators of hereditary medullary thyroid carcinoma risk

CONTEXT

Different inherited profiles of genes involved in cellular mechanisms of activation and detoxification of carcinogenic products can provide specific protection or determine the risk for cancer. Low-penetrance polymorphic genes related to the biotransformation of environmental toxins have been associated with susceptibility to and the phenotype of, human tumours.

OBJECTIVE

To investigate the role of germline inheritance of polymorphisms in CYP1A2*F, CYP1A1 m1, GSTP1, NAT2 and TP53 genes in hereditary medullary thyroid carcinoma (HMTC) patients.

DESIGN

This study was developed in University of Campinas (Unicamp).

PATIENTS

We studied 132 patients with HMTC, 88 first-degree relatives of HMTC patients and 575 control individuals.

MEASUREMENTS

All patients with MTC and their relatives were sequenced for the RET gene and five genes were genotyped using TaqMan(®) system.

RESULTS

We observed that the inheritance of CYP1A2*F (OR = 2·10; 95% CI = 1·11-3·97; P = 0·022), GSTP1 (OR = 4·41; 95% CI = 2·47-7·88; P < 0·001) and NAT2 (OR = 2·54; 95% CI = 1·16-5·58; P = 0·020) variants increased the risk for HMTC. In addition, multiple regression analysis showed that the inheritance of GSTP1 polymorphisms was associated with the diagnosis in older patients (B = 8·0229; 95% IC = ± 5·5735; P = 0·0054). Concerning the group of HTMC relatives, CYP1A2*F (OR = 2:40; 95% CI = 1·19-4·86; P = 0·015), CYP1A1 m1 (OR = 2·79; 95% CI = 1:04-7·51; P = 0·042), GSTP1 (OR = 2·86; 95% IC = 1·53-5·32; P < 0·001) and NAT2 (OR = 2·25; 95% IC = 1·20-4·22; P = 0·012) were associated with HMTC risk.

CONCLUSIONS

We have demonstrated that the inheritance of specific genes determining the individual response to environmental toxins may contribute to the risk and phenotypic variability that exists in patients with HMTC. Moreover, we identified a group at risk in relatives of HMTC patients.

Multiple endocrine neoplasia type 2 and familial medullary thyroid carcinoma: an update

CONTEXT

Over the last decade, our knowledge of the multiple endocrine neoplasia (MEN) type 2 syndromes MEN2A and MEN2B and familial medullary thyroid carcinoma (FMTC) has expanded greatly. In this manuscript, we summarize how recent discoveries have enhanced our understanding of the molecular basis of these diseases and led to improvements in the diagnosis and management of affected patients.

EVIDENCE ACQUISITION

We reviewed the English literature through PubMed from 2000 to the present, using the search terms medullary thyroid carcinoma, multiple endocrine neoplasia type 2, familial medullary thyroid carcinoma, RET proto-oncogene, and calcitonin.

EVIDENCE SYNTHESIS

Over 70 RET mutations are known to cause MEN2A, MEN2B, or FMTC, and recent findings from studies of large kindreds with these syndromes have clouded the relationship between genotype and phenotype, primarily because of the varied clinical presentation of different families with the same RET mutation. This clinical variability has also confounded decisions about the timing of prophylactic thyroidectomy for MTC, the dominant endocrinopathy associated with these syndromes. A distinct advance has been the demonstration through phase II and phase III clinical trials that molecular targeted therapeutics are effective in the treatment of patients with locally advanced or metastatic MTC.

CONCLUSIONS

The effective management of patients with MEN2A, MEN2A, and FMTC depends on an understanding of the variable behavior of disease expression in patients with a specific RET mutation. Information gained from molecular testing, biochemical analysis, and clinical evaluation is important in providing effective management of patients with either early or advanced-stage MTC.

GDNF family ligand dependent STAT3 activation is mediated by specific alternatively spliced isoforms of GFRα2 and RET

Neurturin (NRTN), a member of the GDNF family of ligands (GFL), is currently investigated in a series of clinical trials for Parkinson's disease. NRTN signals through its cognate receptor GFRα2 and co-receptor RET to induce neurite outgrowth, but the underlying mechanism remains to be better understood. STAT3 was previously shown to be activated by oncogenic RET, independent of ligand and GFRα. In this study, we demonstrated that NRTN induced serine(727) but not tyrosine(705) phosphorylation of STAT3 in primary cortical neuron and neuronal cell lines. Remarkably, STAT3 phosphorylation was found to be mediated specifically by GFRα2c and RET9 isoforms. Furthermore, serine but not tyrosine dominant negative mutant of STAT3 impaired NRTN induced neurite outgrowth, indicative of the role of STAT3 as a downstream mediator of NRTN function. Similar to NGF, the NRTN induced P-Ser-STAT3 was localized to the mitochondria but not to the nucleus. Mitochondrial STAT3 was further found to be intimately involved in NRTN induced neurite outgrowth. Collectively, these findings demonstrated the hitherto unrecognized and novel role of specific GFRα2 and RET isoforms in mediating NRTN activation of STAT3 and the transcription independent mechanism whereby the mitochondria localized P-Ser-STAT3 mediated NRTN induced neurite outgrowth.

A comprehensive next generation sequencing-based genetic testing strategy to improve diagnosis of inherited pheochromocytoma and paraganglioma

CONTEXT

Pheochromocytomas and paragangliomas are notable for a high frequency of inherited cases, many of which present as apparently sporadic tumors.

OBJECTIVE

The objective of this study was to establish a comprehensive next generation sequencing (NGS)-based strategy for the diagnosis of patients with pheochromocytoma and paraganglioma by testing simultaneously for mutations in MAX, RET, SDHA, SDHB, SDHC, SDHD, SDHAF2, TMEM127, and VHL.

DESIGN

After the methodology for the assay was designed and established, it was validated on DNA samples with known genotype and then patients were studied prospectively.

SETTING

The study was performed in a diagnostic genetics laboratory.

PATIENTS

DNA samples from 205 individuals affected with adrenal or extraadrenal pheochromocytoma/head and neck paraganglioma (PPGL/HNPGL) were analyzed. A proof-of-principle study was performed using 85 samples known to contain a variant in 1 or more of the genes to be tested, followed by prospective analysis of an additional 120 samples.

MAIN OUTCOME MEASURES

We assessed the ability to use an NGS-based method to perform comprehensive analysis of genes implicated in inherited PPGL/HNPGL.

RESULTS

The proof-of-principle study showed that the NGS assay and analysis gave a sensitivity of 98.7%. A pathogenic mutation was identified in 16.6% of the prospective analysis cohort of 120 patients.

CONCLUSIONS

A comprehensive NGS-based strategy for the analysis of genes associated with predisposition to PPGL and HNPGL was established, validated, and introduced into diagnostic service. The new assay provides simultaneous analysis of 9 genes and allows more rapid and cost-effective mutation detection than the previously used conventional Sanger sequencing-based methodology.

Novel targets in non-small cell lung cancer: ROS1 and RET fusions

The discovery of chromosomal rearrangements involving the anaplastic lymphoma kinase (ALK) gene in non-small cell lung cancer (NSCLC) has stimulated renewed interest in oncogenic fusions as potential therapeutic targets. Recently, genetic alterations in ROS1 and RET were identified in patients with NSCLC. Like ALK, genetic alterations in ROS1 and RET involve chromosomal rearrangements that result in the formation of chimeric fusion kinases capable of oncogenic transformation. Notably, ROS1 and RET rearrangements are rarely found with other genetic alterations, such as EGFR, KRAS, or ALK. This finding suggests that both ROS1 and RET are independent oncogenic drivers that may be viable therapeutic targets. In initial screening studies, ROS1 and RET rearrangements were identified at similar frequencies (approximately 1%-2%), using a variety of genotyping techniques. Importantly, patients with either ROS1 or RET rearrangements appear to have unique clinical and pathologic features that may facilitate identification and enrichment strategies. These features may in turn expedite enrollment in clinical trials evaluating genotype-directed therapies in these rare patient populations. In this review, we summarize the molecular biology, clinical features, detection, and targeting of ROS1 and RET rearrangements in NSCLC.

The GDNF System Is Altered in Diverticular Disease - Implications for Pathogenesis

Background & Aims

Absence of glial cell line-derived neurotrophic factor (GDNF) leads to intestinal aganglionosis. We recently demonstrated that patients with diverticular disease (DD) exhibit hypoganglionosis suggesting neurotrophic factor deprivation. Thus, we screened mRNA expression pattern of the GDNF system in DD and examined the effects of GDNF on cultured enteric neurons.

Methods

Colonic specimens obtained from patients with DD (n = 21) and controls (n = 20) were assessed for mRNA expression levels of the GDNF system (GDNF, GDNF receptors GFRα1 and RET). To identify the tissue source of GDNF and its receptors, laser-microdissected (LMD) samples of human myenteric ganglia and intestinal muscle layers were analyzed separately by qPCR. Furthermore, the effects of GDNF treatment on cultured enteric neurons (receptor expression, neuronal differentiation and plasticity) were monitored.

Results

mRNA expression of GDNF and its receptors was significantly down-regulated in the muscularis propria of patients with DD. LMD samples revealed high expression of GDNF in circular and longitudinal muscle layers, whereas GDNF receptors were also expressed in myenteric ganglia. GDNF treatment of cultured enteric neurons increased mRNA expression of its receptors and promoted neuronal differentiation and plasticity revealed by synaptophysin mRNA and protein expression.

Conclusions

Our results suggest that the GDNF system is compromised in DD. In vitro studies demonstrate that GDNF enhances expression of its receptors and promotes enteric neuronal differentiation and plasticity. Since patients with DD exhibit hypoganglionosis, we propose that the observed enteric neuronal loss in DD may be due to lacking neurotrophic support mediated by the GDNF system.

Genetics of pheochromocytoma and paraganglioma syndromes: new advances and future treatment options

PURPOSE OF REVIEW

To summarize the recent advances in the genetics of pheochromocytoma and paraganglioma (PHEO/PGL), focusing on the new susceptibility genes and dividing PHEOs/PGLs into two groups based on their transcription profile.

RECENT FINDINGS

Recently, TMEM127, MYC-associated factor X, and hypoxia-inducible factor (HIF) 2α have been described in the pathogenesis of PHEOs/PGLs. Thus, now about 30-40% of these tumors are linked to the germline mutations, which also include mutations in the VHL, RET, NF1, SDHx, and SDHAF2 genes. Furthermore, PHEOs/PGLs have been divided into two groups, cluster 1 (SDHx/VHL) and cluster 2 (RET/NF1), based on the transcription profile revealed by genome-wide expression microarray analysis.

SUMMARY

PHEOs/PGLs are the most inherited tumors among (neuro)endocrine tumors. Future approaches in genetics, including whole-genome sequencing, will allow the discovery of additional PHEO/PGL susceptibility genes. The current division of PHEOs/PGLs into cluster 1 and 2 provides us with additional knowledge related to the pathogenesis of these tumors, including the introduction of new treatment options for patients with metastatic PHEOs/PGLs. New discoveries related to the role of the HIF-1/HIF-2α genes in the pathogenesis of almost all inherited PHEOs/PGLs may call for a new regrouping of these tumors and discoveries of new treatment targets.

Retinoic acid upregulates ret and induces chain migration and population expansion in vagal neural crest cells to colonise the embryonic gut

Vagal neural crest cells (VNCCs) arise in the hindbrain, and at (avian) embryonic day (E) 1.5 commence migration through paraxial tissues to reach the foregut as chains of cells 1–2 days later. They then colonise the rest of the gut in a rostrocaudal wave. The chains of migrating cells later resolve into the ganglia of the enteric nervous system. In organ culture, E4.5 VNCCs resident in the gut (termed enteric or ENCC) which have previously encountered vagal paraxial tissues, rapidly colonised aneural gut tissue in large numbers as chains of cells. Within the same timeframe, E1.5 VNCCs not previously exposed to paraxial tissues provided very few cells that entered the gut mesenchyme, and these never formed chains, despite their ability to migrate in paraxial tissue and in conventional cell culture. Exposing VNCCs in vitro to paraxial tissue normally encountered en route to the foregut conferred enteric migratory ability. VNCC after passage through paraxial tissue developed elements of retinoic acid signalling such as Retinoic Acid Binding Protein 1 expression. The paraxial tissue's ability to promote gut colonisation was reproduced by the addition of retinoic acid, or the synthetic retinoid Am80, to VNCCs (but not to trunk NCCs) in organ culture. The retinoic acid receptor antagonist CD 2665 strongly reduced enteric colonisation by E1.5 VNCC and E4.5 ENCCs, at a concentration suggesting RARα signalling. By FACS analysis, retinoic acid application to vagal neural tube and NCCs in vitro upregulated Ret; a Glial-derived-neurotrophic-factor receptor expressed by ENCCs which is necessary for normal enteric colonisation. This shows that early VNCC, although migratory, are incapable of migrating in appropriate chains in gut mesenchyme, but can be primed for this by retinoic acid. This is the first instance of the characteristic form of NCC migration, chain migration, being attributed to the application of a morphogen.

Ponatinib (AP24534) is a novel potent inhibitor of oncogenic RET mutants associated with thyroid cancer

CONTEXT

The RET tyrosine kinase encoding gene acts as a dominantly transforming oncogene in thyroid carcinoma and other malignancies. Ponatinib (AP24534) is an oral ATP-competitive tyrosine kinase inhibitor that is in advanced clinical experimentation in leukemia.

OBJECTIVE

We tested whether ponatinib inhibited RET kinase and oncogenic activity.

METHODS

Ponatinib activity was studied by an in vitro RET immunocomplex kinase assay and immunoblotting. The effects of ponatinib on proliferation of human TT, MZ-CRC-1, and TPC-1 thyroid carcinoma cells, which harbor endogenous oncogenic RET alleles, and of NIH3T3 fibroblasts transfected with oncogenic RET mutants were determined. Ponatinib activity on TT cell xenografted tumors in athymic mice was measured.

RESULTS

Ponatinib inhibited immunopurified RET kinase at the IC₅₀ of 25.8 nM (95% confidence interval [CI] = 23.15-28.77 nM). It also inhibited (IC₅₀ = 33.9 nM; 95% CI = 26.41-43.58 nM) kinase activity of RET/V804M, a RET mutant displaying resistance to other tyrosine kinase inhibitor. Ponatinib blunted phosphorylation of point-mutant and rearranged RET-derived oncoproteins and inhibited proliferation of RET-transformed fibroblasts and RET mutant thyroid carcinoma cells. Finally, after 3 weeks of treatment with ponatinib (30 mg/kg/d), the volume of TT cell (medullary thyroid carcinoma) xenografts was reduced from 133 mm³ to an unmeasurable size (difference = 133 mm³, 95% CI = -83 to 349 mm³) (P < .001). Ponatinib-treated TT cell tumors displayed a reduction in the mitotic index, RET phosphorylation, and signaling.

CONCLUSIONS

Ponatinib is a potent inhibitor of RET kinase and has promising preclinical activity in models of RET-driven medullary thyroid carcinoma.

Tiron and trolox potentiate the autophagic cell death induced by magnolol analog Ery5 by activation of Bax in HL-60 cells

This study describes the mechanism of trolox and tiron induced potentiation of cytotoxicity caused by Ery5, an analog of magnolol, in human myeloid leukemia HL-60 cells. Ery5 induced cytotoxicity in HL-60 cells by involving activation of bax and cleavage of caspase 3, which contributed towards activation of both apoptotic and autophagic pathways. Trolox and tiron, even at non-toxic concentrations, contributed to the cytotoxicity of Ery5 by activation of autophagic proteins like ATG7, ATG12 and LC3-II. Z-VAD-fmk mediated reduction in the cytotoxicity and expression of autophagic proteins, further suggested that autophagy induced by Ery5 is largely dependent upon caspases. Interestingly, Ery5 induced autophagy was accompanied by the downregulation of PI3K/AKT pathway whereas, trolox and tiron strongly enhanced this effect. In addition to that treatment of cells with Ery5, trolox and tiron individually, displayed a marked upregulation of Bax. The involvement of Bax in trolox and tiron induced enhancement of the cytotoxicity of Ery5 was confirmed, when siRNA induced silencing of Bax led to increased viability of the cells and exerted a strong inhibitory effect on LC3-II accumulation and p62 degradation in case of cells treated by the combination of Ery5 with trolox or tiron. Additionally, an important role of PARP in Ery5 mediated cell death has been suggested by PARP silencing experiments, however, potentiation of autophagic cytotoxicity by trolox and tiron did not seem to be dependent on PARP-1. Therefore, Bax seems to play a vital role in trolox and tiron mediated potentiation of autophagic cell death by Ery5 in HL-60 cells.

High penetrance of pheochromocytoma in multiple endocrine neoplasia 2 caused by germ line RET codon 634 mutation in Japanese patients

OBJECTIVE

The precise penetrance of pheochromocytoma (PHEO) in multiple endocrine neoplasia type 2 (MEN2) has not been reported in a large cohort. In this study, we aimed to clarify the codon-specific penetrance of PHEO in MEN2.

DESIGN

We established a study group designated the 'MEN Consortium of Japan' in 2008 and asked physicians and surgeons to provide clinical and genetic information on patients they had treated up to 2011.

METHODS

Data were collected on patients identified as carriers of the RET mutation or diagnosed with medullary thyroid carcinoma (MTC) and/or PHEO with family history from 52 institutions all over Japan.

RESULTS

Of 493 registered MEN2 patients, RET mutation data were available for 390. Of these, 144 developed PHEOs, while 246 did not. The penetrance of PHEO was 25% by age 30 years, 52% by age 50 years, and 88% by age 77 years in RET mutation carriers with a codon 634 mutation. All patients with a codon 918 mutation (MEN2B) developed PHEO by age 56 years. Less than 32%penetrance of PHEO was seen in patients with mutations at codons other than 634 and 918.

CONCLUSIONS

Most patients with a codon 634 mutation develop PHEOs as well as MTC during their lifetime.

Molecular epidemiology of multiple endocrine neoplasia 2: implications for RET screening in the new millenium

OBJECTIVE

Twenty years ago, the groundbreaking discovery that rearranged during transfection (RET) mutations underlie multiple endocrine neoplasia 2 (MEN2) and familial medullary thyroid cancer (FMTC) ushered in the era of personalized medicine. MEN2-associated signs, taking time to manifest, can be subtle. This study sought to clarify to what extent conventional estimates of 1:200 000-500 000 underestimate the incidence of RET mutations in the population.

DESIGN

Included in this retrospective investigation were 333 RET carriers born between 1951 and 2000 and operated on at the largest German surgical referral center (286 carriers) or elsewhere (47 carriers).

METHODS

To estimate the incidence of RET mutations, the number of RET carriers born in Germany in five decades (1951-1960, 1961-1970, 1971-1980, 1981-1990, and 1991-2000) was divided by the corresponding number of German live births.

RESULTS

Owing to improved diagnosis and capture of FMTC and MEN2 patients, minimum incidence estimates increased over time: overall from 5.0 (1951-1960) to 9.9 (1991-2000) per million live births and year (P=0.008), and by American Thyroid Association/ATA class from 1.7 to 3.7 for ATA class C (P=0.008); from 1.8 to 2.7 for ATA class A (P=0.017); from 1.5 to 2.2 for ATA class B (P=0.20); and from 0 to 1.4 for ATA class D mutations per million live births and year (P=0.008). Based on 1991-2000 incidence estimates the prevalence in Germany is ∼1:80 000 inhabitants.

CONCLUSIONS

The molecular minimum incidence estimate of ≈1:100 000 was two- to fivefold greater than conventional estimates of 1:200 000-500 000.

Measurement of calcitonin and calcitonin gene-related peptide mRNA refines the management of patients with medullary thyroid cancer and may replace calcitonin-stimulation tests

BACKGROUND

Serum calcitonin (sCT) is the main tumor marker for medullary thyroid cancer (MTC), but it has certain limitations. Various sCT assays may have important intra-assay or interassay variation and may yield different and sometimes conflicting results. A pentagastrin- or calcium-stimulation calcitonin (CT) test may be desirable in some situations. Alternatively, or in the absence of the stimulation test, mRNA detection offers the advantages of being more comfortable and less invasive; it only requires blood collection and has no side effects. The objective of this study was to investigate the applicability of measuring calcitonin-related polypeptide alpha (CALCA) gene transcripts (CT-CALCA and calcitonin gene-related peptide [CGRP]-CALCA) in patients with MTC and in relatives diagnosed with a RET mutation and to test mRNA as an alternative diagnostic tool for the calcitonin-stimulation test.

METHODS

Twenty-three healthy controls and 26 individuals evaluated for MTC were selected, including patients with sporadic or hereditary MTC and RET mutation-carrying relatives. For molecular analysis, RNA was extracted from peripheral blood, followed by cDNA synthesis using 3.5 μg of total RNA. Quantitative real-time polymerase chain reaction (RT-qPCR) was performed with SYBR Green and 200 nM of each primer for the two specific mRNA targets (CT-CALCA or CGRP-CALCA) and normalized with the ribosomal protein S8 as the reference gene.

RESULTS

We detected CALCA transcripts in the blood samples and observed a positive correlation between them (r=0.946, p<0.0001). Both mRNAs also correlated with sCT (CT-CALCA, r=0.713, p<0.0001; CGRP-CALCA, r=0.714, p<0.0001). The relative expression of CT-CALCA and CGRP-CALCA presented higher clinical sensitivity (86.67 and 100, respectively), specificity (97.06 and 97.06), positive predictive value (92.86 and 93.75), and negative predictive value (94.29 and 100), than did sCT (73.33, 82.35, 64.71, and 87.50, respectively). In addition, the CALCA transcript measurement mirrored the response to the pentagastrin test.

CONCLUSION

We demonstrate that the measurement of CALCA gene transcripts in the bloodstream is feasible and may refine the management of patients with MTC and RET mutation-carrying relatives. We propose considering the application of this diagnostic tool as an alternative to the calcitonin-stimulation test.

RET codon 618 mutations in Saudi families with multiple endocrine neoplasia Type 2A and familial medullary thyroid carcinoma

BACKGROUND AND OBJECTIVES

Certain diseases such as multiple endocrine neoplasia (MEN) 2A, MEN 2B, familial and sporadic medullary thyroid carcinoma (MTC) and renal dysgenesis are related to abnormalities of the RET protein. Our aim was to evaluate the frequency of RET mutation in 10 Saudi families with MEN type 2A and familial MTC.

DESIGN AND SETTING

A cross-sectional prospective study of patients followed up at King Abdulaziz University Hospital and King Abdulaziz Medical City, Jeddah, between March 2001 and March 2011.

PATIENTS AND METHODS

Genomic DNA was isolated from peripheral blood leukocytes of all subjects by standard procedures. Exons 10, 11, 13, 14 and 16 of the RET proto-oncogene were analyzed by single-strand conformation polymorphism, direct DNA sequencing and/or restriction enzyme analysis.

RESULTS

We screened 79 subjects for the RET mutation. Of which 43 subjects had hereditary MTC were en.rolled in this study. MEN type 2A was identified in 25 subjects; MTC was diagnosed in all 25 subjects (100%), pheochromocytoma in 13 subjects (52%) and hyperparathyroidism in 4 subjects (16%). The most frequent genotype in patients with MEN 2A syndrome was a codon 618 mutation (46.6%), followed by a codon 634 mutation (44.2%). Among the 5 families with MEN 2A, 3 had a mutation at codon 634, whereas 2 had a mutation at codon 618.

CONCLUSION

The most frequent RET proto-oncogene mutation in our series was in codon 618 (exon 10).

[Clinical diagnosis and treatment of familial medullary thyroid carcinoma caused by a p.C618Y RET proto-oncogene mutation in a Chinese pedigree]

OBJECTIVE

To explore the clinical characteristics, therapeutic and clinical significance for RET proto-oncogene screening in a pedigree with familial medullary thyroid carcinoma.

METHODS

Comprehensive medical history was obtained from 19 members in a 4-generate southern Chinese family. Systemic clinical investigations including biochemical testing, imaging examinations and germline RET screening.

RESULTS

RET screening showed heterozygous missense mutations of TGC to TAC at codon 618 on exon 10 in 8 cases (p.C618Y) completely consistent with the clinical manifestations. The clinical data of 7 patients with medullary thyroid carcinoma (MTC) and 2 carriers of asymptomatic RET mutation from were analyzed. Single/bilateral multi-centric MTC with lymph node metastases was confirmed in 6 cases by histopathology and 1 case by clinical examination. There were 1 male and 6 females with an initial mean diagnostic age was 49.6 years (range: 24 - 78). All had palpable neck masses. And the mean maximum diameter of MTC was 2.6 cm (range 1.4 - 4.4). Seven patients underwent thyroidectomy except a 78-year-old female patient: right total and left subtotal thyroidectomy (n = 1), right total thyroidectomy (previous left total thyroidectomy for benign mass) (n = 1) and total thyroidectomy (n = 4) were performed. All procedures were accompanied by at least bilateral level VI lymph node dissection and/or with modified single/bilateral neck dissection. After the first operation, 6 patients still presented a high value of calcitonin: 1 patient died of metastasis 64 months postoperatively; 3 patients underwent reoperation at 6 months after initial operation, the calcitonin levels dropped to normal in 2/3 cases and stayed higher in 1 case; another two cases presented bilateral thyroid gland residua, local lymph node enlargement on imaging examination and elevated levels of calcitonin at 214 and 60 months postoperation respectively. However, 1/2 asymptomatic with elevated pre-operative calcitonin subjects underwent total thyroidectomy and histopathological examination showed bilateral C cell hyperplasia. The other carriers, without surgery, with normal neck images, close monitoring and a 10-month follow-up, still presented undetectable calcitonin.

CONCLUSIONS

Based on family survey, integrated RET screening and serum levels of calcitonin facilitate an early diagnosis and normalize surgery to improve the prognosis. For asymptomatic RET mutation carriers, their levels of calcitonin shall guide the individualized regimen of prophylactic thyroidectomy or strict monitoring and follow-ups.