MET receptor tyrosine kinase sequence alterations in differentiated thyroid carcinoma

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.

Molecular Characteristics of Radon Associated Lung Cancer Highlights MET Alterations

Simple Summary

Lung cancer (LC) is the leading cause of cancer death worldwide. After smoking, one of the most prominent risk factors for LC development is radon (Rn) exposure. In our study we analysed and compared the genetic landscape of LC patients from a Rn exposed village with local matched non-exposed patients. Within the concordant genetic landscape, an increase in genetic MET proto-oncogene, receptor tyrosine kinase (MET) alteration in the Rn-exposed cohort was monitored, underlining the importance of routine MET testing and potential to enable a more effective treatment for this specific subgroup.

Abstract

Effective targeted treatment strategies resulted from molecular profiling of lung cancer with distinct prevalent mutation profiles in smokers and non-smokers. Although Rn is the second most important risk factor, data for Rn-dependent driver events are limited. Therefore, a Rn-exposed cohort of lung cancer patients was screened for oncogenic drivers and their survival and genetic profiles were compared with data of the average regional population. Genetic alterations were analysed in 20 Rn-exposed and 22 histologically matched non-Rn exposed LC patients using targeted Next generation sequencing (NGS) and Fluorescence In Situ Hybridization (FISH). Sufficient material and sample quality could be obtained in 14/27 non-exposed versus 17/22 Rn-exposed LC samples. Survival was analysed in comparison to a histologically and stage-matched regional non-exposed lung cancer cohort (n = 51) for hypothesis generating. Median overall survivals were 83.02 months in the Rn-exposed and 38.7 months in the non-exposed lung cancer cohort (p = 0.22). Genetic alterations of both patient cohorts were in high concordance, except for an increase in MET alterations and a decrease in TP53 mutations in the Rn-exposed patients in this small hypothesis generating study.

Development of metastatic poorly differentiated thyroid cancer from a sub-centimeter papillary thyroid carcinoma in a young patient with a germline MET mutation - association or random chance?

Background

Thyroid cancer dedifferentiation is an unusual observation among young patients and is poorly understood, although a recent correlation to DICER1 gene mutations has been proposed.

Case presentation

A 28-year old patient presented with a sub-centimeter cytology-verified primary papillary thyroid carcinoma (PTC) and a synchronous lateral lymph node metastasis. Following surgery, histopathology confirmed a 9 mm oxyphilic PTC and a synchronous metastasis of poorly differentiated thyroid carcinoma (PDTC). Extensive molecular examinations of both lesions revealed wildtype DICER1 sequences, but identified a somatic ETV6-NTRK3 gene fusion and a MET germline variant (c.1076G > A, p.Arg359Gln). MET is an established oncogene known to be overexpressed in thyroid cancer, and this specific alteration was not reported as a single nucleotide polymorphism (SNP), suggestive of a mutation. Both the primary PTC and the metastatic PDTC displayed strong MET immunoreactivity. A validation cohort of 50 PTCs from young patients were analyzed using quantitative real-time PCR, revealing significantly higher MET gene expression in tumors than normal thyroid controls, a finding which was particularly pronounced in BRAF V600E mutated cases. No additional tumors apart from the index case harbored the p.Arg359Gln MET mutation. Transfecting PTC cell lines MDA-T32 and MDA-T41 with a p.Arg359Gln MET plasmid construct revealed no obvious effects on cellular migratory or invasive properties, whereas overexpression of wildtype MET stimulated invasion.

Conclusions

The question of whether the observed MET mutation in any way influenced the dedifferentiation of a primary PTC into a PDTC metastasis remains to be established. Moreover, our data corroborate earlier studies, indicating that MET is aberrantly expressed in PTC and may influence the invasive behavior of these tumors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13044-021-00110-4.

HGF/c-Met Signalling in the Tumor Microenvironment

Recently, it has become clearer that tumor plasticity increases the chance that cancer cells could acquire new mechanisms to escape immune surveillance, become resistant to conventional drugs, and spread to distant sites.Effectively, tumor plasticity drives adaptive response of cancer cells to hypoxia and nutrient deprivation leading to stimulation of neoangionesis or tumor escape. Therefore, tumor plasticity is believed to be a great contributor in recurrence and metastatic dissemination of cancer cells. Importantly, it could be an Achilles' heel of cancer if we could identify molecular mechanisms dictating this phenotype.The reactivation of stem-like signalling pathways is considered a great determinant of tumor plasticity; in addition, a key role has been also attributed to tumor microenvironment (TME). Indeed, it has been proved that cancer cells interact with different cells in the surrounding extracellular matrix (ECM). Interestingly, well-established communication represents a potential allied in maintenance of a plastic phenotype in cancer cells supporting tumor growth and spread. An important signalling pathway mediating cancer cell-TME crosstalk is represented by the HGF/c-Met signalling.Here, we review the role of the HGF/c-Met signalling in tumor-stroma crosstalk focusing on novel findings underlying its role in tumor plasticity, immune escape, and development of adaptive mechanisms.

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.

Macrofollicular Variant of Follicular Thyroid Carcinoma (MV-FTC) with a Somatic DICER1 Gene Mutation: Case Report and Review of the Literature

Benign thyroid lesions such as multinodular goiter and adenomatoid nodules are well-circumscribed lesions displaying a macrofollicular growth pattern and lack of nuclear atypia. The highly unusual macrofollicular variant of follicular thyroid carcinoma (MV-FTC) mirrors these attributes and is thereby misclassified by cytological examination of fine-needle aspiration biopsies. The MV-FTC diagnosis is instead suggested following histological investigation, in which malignant attributes, most commonly capsular invasion, are noted. The bulk of MV-FTCs described in the literature arise in younger female patients and carry an excellent prognosis. A recent coupling to mutations in the DICER1 tumor suppressor gene has been proposed, possibly indicating aberrancies in micro-RNA (miRNA) patterns as responsible of the tumorigenic process. We describe the cytological, histological and molecular phenotype of a 35 mm large MV-FTC arising in the right thyroid lobe of a 33-year-old female with a family history of multinodular goiter. The tumor was encapsulated and strikingly inconspicuous in terms of cellularity and atypia, but nevertheless displayed multiple foci with capsular invasion. A next-generation molecular screening of tumor DNA revealed missense variants in DICER1 (p. D1709N) and MET (p. T1010I), but no established fusion gene events. After sequencing of germline DNA, the DICER1 mutation was confirmed as somatic, while the MET variant was constitutional. The patient is alive and well, currently awaiting radioiodine treatment. This MV-FTC mirrors previous publications, suggesting that these tumors carry a favorable prognosis and predominantly arise in younger females. Moreover, DICER1 mutations should be considered a common driver event in the development of MV-FTCs.

Genetic Landscape of Somatic Mutations in a Large Cohort of Sporadic Medullary Thyroid Carcinomas Studied by Next-Generation Targeted Sequencing

Sporadic Medullary Thyroid Carcinoma (sMTC) is a rare but aggressive thyroid tumor. RET and RAS genes are present in about 50%-80% of cases, but most of the remaining cases are still orphan of a genetic driver. We studied the largest series of sMTC by deep sequencing to define the mutational landscape. With this methodology we greatly reduced the number of RET- or RAS-negative cases and we confirmed the central role of RET and RAS mutations. Moreover, we highlighted the bad prognostic role of RET mutations in sMTC and consolidated the favorable prognostic role of RAS mutations. For the first time, we showed that the variant allele frequency represents an additional prognostic marker inside the group of RET-mutated sMTC.

Hürthle cell lesions on thyroid fine needle aspiration cytology: Molecular and histologic correlation

BACKGROUND

Hürthle cell lesions often pose diagnostic challenges, despite their common occurrence on thyroid fine-needle aspiration cytology (FNAC). The associated molecular alterations are also not well understood. Therefore, our study aimed to delineate the molecular profile of Hürthle cell lesions classified as Bethesda Categories III or IV (atypia of undetermined significance (AUS) or suspicious for follicular neoplasm (SFN)) on FNAC and to correlate this molecular profile with surgical resection findings.

METHODS

This study consisted of 188 Hürthle cell lesions with indeterminate cytology and ThyroSeq® v2/v3 molecular testing results. Surgical follow-up was available for 33 cases.

RESULTS

The majority of indeterminate Hürthle cell lesions had negative ThyroSeq® results (61%) and were benign on available surgical follow-up. The most prevalent mutations involved the RAS gene (21%), which were associated with benign lesions, non-invasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP), and malignancy. The remaining mutations involved less than 18% of the cases, including PAX8/PPARG (3.7%), TSHR (3.7%), EIF1AX (2.7%), MET (2.1%), PTEN (1.6%), clonal copy number alteration (1.6%), TERT (1.1%), and 0.5% each of GNAS, PIK3CA, and TP53 mutations. On follow-up, 45% were benign, 24% were NIFTP, and 30% were malignant. The malignant cases had different molecular alterations.

CONCLUSION

No single molecular alteration defines cytologically indeterminate Hürthle cell lesions; the majority of cases have low-risk or no molecular alterations and are benign on follow-up. These findings suggest that molecular testing may be useful, but is not definitive, in determining which cases may be managed conservatively; additional studies are needed to fully determine the negative predictive value in ruling out malignancy.

MET overexpression and activation favors invasiveness in a model of anaplastic thyroid cancer

In thyroid cancers, MET receptor overexpression has been associated with higher risk of metastatic progression. In this study, it was shown that the anaplastic thyroid cancer (ATC)-derived TTA1 cell line overexpressed MET. By using FISH and relative quantification by qPCR, it was demonstrated that this overexpression resulted from a MET amplification with more than 20 copies. As expected, MET overexpression led to its constitutive activation and upregulated signaling towards the MAPK, PI3K/AKT, STAT3 and NF-κB pathways. Since the usual feature of MET-amplified cell lines is the "MET addiction" for their cell proliferation, the effect of the highly selective ATP competitive MET inhibitor PHA665752 was analyzed. While PHA665752 strongly inhibited the MAPK pathway, it did not reduce cell proliferation in TTA1 cells (IC₅₀ = 4100 nM). This resistance to PHA665752 of the TTA1 cell line was demonstrated to be related to EGFR-MET functional cross-talk and PI3K/AKT and NF-κB signaling. Nevertheless, PHA665752 suppressed the anchorage-independent growth capacity of the TTA1 cell line and reduced cell migration and invasion in a transwell assay. The role of activated MET in these neoplastic properties of the TTA1 cells was also proved with si-MET-RNA targeting. Thus, this work highlights the TTA1 cell line as the first model of MET amplification in an ATC cell line, which leads to MET constitutive activation and underlies its neoplastic properties. Besides being a useful model for MET inhibitors screening, the TTA1 cell line also supports the argument for searching for MET amplification in ATC, as it could have therapeutic implications.

Medullary Thyroid Cancer: Clinical Characteristics and New Insights into Therapeutic Strategies Targeting Tyrosine Kinases

Medullary thyroid carcinoma (MTC) is a hyperplasia of thyroid C-cells, accounting for 5-10% of all thyroid cancers. MTCs may appear as sporadic or hereditary forms, and several molecules and signaling pathways have been found to function defectively in MTC cells. Tyrosine kinases are the most well-studied molecules that have abnormal function in these tumor cells. Due to their limited response, chemotherapeutic agents and radiation therapy are not effective in treating patients with advanced metastatic MTC. In the past decade, significant attention has been given to the utilization of multikinase inhibitors as targeted therapeutic agents for treating MTC patients, with the most promising results arising from the study of tyrosine kinase inhibitors, which generally bind to the ATP binding sites of these kinases. Two drugs-vandetanib and cabozantinib-are approved for the treatment of aggressive advanced MTC; however, the potential for toxicities and adverse effects of these agents on patient quality of life need to be considered against any therapeutic gain. According to recent data, it appears that inhibition of only one receptor or molecule in a pathway is not as effective as simultaneous inhibition of different pathways, indicating the need to use combination therapy. The main purpose of this review is to describe the clinical characteristics, molecular mechanisms, and current molecular and targeted therapeutic strategies active in clinical trials for advanced MTC treatment.

Unexpected cancer-predisposition gene variants in Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome patients without underlying germline PTEN mutations

Patients with heritable cancer syndromes characterized by germline PTEN mutations (termed PTEN hamartoma tumor syndrome, PHTS) benefit from PTEN-enabled cancer risk assessment and clinical management. PTEN-wildtype patients (~50%) remain at increased risk of developing certain cancers. Existence of germline mutations in other known cancer susceptibility genes has not been explored in these patients, with implications for different medical management. We conducted a 4-year multicenter prospective study of incident patients with features of Cowden/Cowden-like (CS/CS-like) and Bannayan-Riley-Ruvalcaba syndromes (BRRS) without PTEN mutations. Exome sequencing and targeted analysis were performed including 59 clinically actionable genes from the American College of Medical Genetics and Genomics (ACMG) and 24 additional genes associated with inherited cancer syndromes. Pathogenic or likely pathogenic cancer susceptibility gene alterations were found in 7 of the 87 (8%) CS/CS-like and BRRS patients and included MUTYH, RET, TSC2, BRCA1, BRCA2, ERCC2 and HRAS. We found classic phenotypes associated with the identified genes in 5 of the 7 (71.4%) patients. Variant positive patients were enriched for the presence of second malignant neoplasms compared to patients without identified variants (OR = 6.101, 95% CI 1.143-35.98, p = 0.035). Germline variant spectrum and frequencies were compared to The Cancer Genome Atlas (TCGA), including 6 apparently sporadic cancers associated with PHTS. With comparable overall prevalence of germline variants, the spectrum of mutated genes was different in our patients compared to TCGA. Intriguingly, we also found notable enrichment of variants of uncertain significance (VUS) in our patients (OR = 2.3, 95% CI 1.5-3.5, p = 0.0002). Our data suggest that only a small subset of PTEN-wildtype CS/CS-like and BRRS patients could be accounted for by germline variants in some of the known cancer-related genes. Thus, the existence of alterations in other and more likely non-classic cancer-associated genes is plausible, reflecting the complexity of these heterogeneous hereditary cancer syndromes.

Selinexor (KPT-330) has antitumor activity against anaplastic thyroid carcinoma in vitro and in vivo and enhances sensitivity to doxorubicin

Anaplastic thyroid carcinoma (ATC) is one of the most lethal malignancies having no effective treatment. Exportin-1 (XPO1) is the key mediator of nuclear export of many tumor suppressor proteins and is overexpressed in human cancers. In this study, we examined the therapeutic potential of selinexor (XPO1 inhibitor) against human ATC cells both in vitro and in vivo. Here, we showed that XPO1 is robustly expressed in primary ATC samples and human ATC cell lines. Silencing of XPO1 by either shRNA or selinexor significantly reduced cellular growth and induced cell cycle arrest, apoptosis of ATC cells by altering the protein expression of cancer-related genes. Moreover, selinexor significantly inhibited tumor growth of ATC xenografts. Microarray analysis showed enrichment of DNA replication, cell cycle, cell cycle checkpoint and TNF pathways in selinexor treated ATC cells. Importantly, selinexor decreased AXL and GAS6 levels in CAL62 and HTH83 cells and suppressed the phosphorylation of downstream targets of AXL signaling such as AKT and P70S6K. Finally, a combination of selinexor with doxorubicin demonstrated a synergistic decrease in the cellular proliferation of several ATC cells. These results provide a rationale for investigating the efficacy of combining selinexor and doxorubicin therapy to improve the outcome of ATC patients.

Single-Center Experience with a Targeted Next Generation Sequencing Assay for Assessment of Relevant Somatic Alterations in Solid Tumors

Companion diagnostics rely on genomic testing of molecular alterations to enable effective cancer treatment. Here we report the clinical application and validation of the Oncomine Focus Assay (OFA), an integrated, commercially available next-generation sequencing (NGS) assay for the rapid and simultaneous detection of single nucleotide variants, short insertions and deletions, copy number variations, and gene rearrangements in 52 cancer genes with therapeutic relevance. Two independent patient cohorts were investigated to define the workflow, turnaround times, feasibility, and reliability of OFA targeted sequencing in clinical application and using archival material. Cohort I consisted of 59 diagnostic clinical samples from the daily routine submitted for molecular testing over a 4-month time period. Cohort II consisted of 39 archival melanoma samples that were up to 15years old. Libraries were prepared from isolated nucleic acids and sequenced on the Ion Torrent PGM sequencer. Sequencing datasets were analyzed using the Ion Reporter software. Genomic alterations were identified and validated by orthogonal conventional assays including pyrosequencing and immunohistochemistry. Sequencing results of both cohorts, including archival formalin-fixed, paraffin-embedded material stored up to 15years, were consistent with published variant frequencies. A concordance of 100% between established assays and OFA targeted NGS was observed. The OFA workflow enabled a turnaround of 3½ days. Taken together, OFA was found to be a convenient tool for fast, reliable, broadly applicable and cost-effective targeted NGS of tumor samples in routine diagnostics. Thus, OFA has strong potential to become an important asset for precision oncology.

A Concise Atlas of Thyroid Cancer Next-Generation Sequencing Panel ThyroSeq v.2

The next-generation sequencing technology allows high out-put genomic analysis. An innovative assay in thyroid cancer, ThyroSeq® was developed for targeted mutation detection by next generation sequencing technology in fine needle aspiration and tissue samples. ThyroSeq v.2 next generation sequencing panel offers simultaneous sequencing and detection in >1000 hotspots of 14 thyroid cancer-related genes and for 42 types of gene fusions known to occur in thyroid cancer. ThyroSeq is being increasingly used to further narrow the indeterminate category defined by cytology for thyroid nodules. From a surgical perspective, genomic profiling also provides prognostic and predictive information and closely relates to determination of surgical strategy. Both the genomic analysis technology and the informatics for the cancer genome data base are rapidly developing. In this paper, we have gathered existing information on the thyroid cancer-related genes involved in the initiation and progression of thyroid cancer. Our goal is to assemble a glossary for the current ThyroSeq genomic panel that can help elucidate the role genomics play in thyroid cancer oncogenesis.

MET exon 14 juxtamembrane splicing mutations: clinical and therapeutical perspectives for cancer therapy

The MET proto-oncogene plays crucial roles in cell growth and proliferation, survival and apoptosis, epithelial-mesenchymal transition (EMT) and invasion, potentially conditioning the development and progression of the carcinogenesis process. The MET-associated aberrant signaling could be triggered by a variety of mechanisms, such as mutations, gene amplification, increased gene copy number and Met/HGF protein expression. Among the various MET alterations, MET exon 14 splicing abnormalities, causing the loss of the Met juxtamembrane (JM) domain, recently emerged as a new potential oncogenic driver and have been identified and validated across different cancer and histology subtypes. Moreover, this aberration was found to be mutually exclusive with other recognized drivers, thus strongly nominating its potential oncogenic role. Recently, the clinical activity of anti-Met-targeted therapy was demonstrated particularly in patients harboring MET exon 14 skipping lung cancer, resulting in a renewed enthusiasm to further test MET precision therapy in prospective trials. In this review, the key preclinical and clinical data regarding MET exon 14 skipping splicing variants as an actionable genomic aberration in cancer are described, and the perspectives deriving from the validation of such alteration as a potential target, which may further allow driving the therapeutic approach in this molecularly selected patients' subgroup, are explored.

Systemic treatment and management approaches for medullary thyroid cancer

Although rare, medullary thyroid cancer (MTC) exemplifies the value that ever-expanding knowledge of molecular pathways and mechanisms brings to managing challenging cancers. Although surgery can be curative for MTC in many patients, a substantial proportion of patients present with locoregional or distant metastatic disease. Once distant disease occurs, treatment options are limited, and conventional cancer treatments such as cytotoxic chemotherapy are of minimal benefit. Biomarkers such as calcitonin and carcinoembryonic antigen are important correlates of disease burden as well as predictors of disease progress, including recurrence and survival. MTC is either sporadic (∼75%) or inherited (∼25%) as an autosomal dominant disease. Regardless, germline and somatic mutations, particularly in the rearranged during transfection (RET) proto-oncogene, are key factors in the neoplastic process. Gain-of-function RET mutations result in overactive proteins that lead to abnormal activation of downstream signal transduction pathways, resulting in ligand-independent growth and resistance to apoptotic stimuli. Specific RET mutation variants have been found to correlate with phenotype and natural history of MTC with some defects portending a more aggressive clinical course. Greater understanding of the consequence of the aberrant signaling pathway has fostered the development of targeted therapies. Two small-molecule tyrosine kinase inhibitors, vandetanib and cabozantinib, are currently available as approved agents for the treatment of advanced or progressive MTC and provide significant increases in progression-free survival. Since there have been no head-to-head comparisons, clinicians often select between these agents on the basis of familiarity, patient characteristics, comorbidities, and toxicity profile.

Second primary malignancies in renal cortical neoplasms: an updated evaluation from a single institution

PURPOSE

To examine the incidence of secondary primary malignancies in patients with renal cortical neoplasms.

METHODS

Between January 1989 and July 2010, 3647 patients underwent surgery at our institution for a renal cortical neoplasm and were followed through 2012. Occurrence of other malignancies was classified as antecedent, synchronous, or subsequent. All patients with antecedent malignancies (n = 498) and a randomly selected half of those with synchronous malignancies (n = 83) were excluded. The expected number of second primaries was calculated by multiplying Surveillance, Epidemiology, and End Results Program incidence rates of renal cortical neoplasms by person-years at risk within categories of age, sex, and year of diagnosis. The standardized incidence ratio (SIR) was calculated as observed cancers divided by expected incidence of the cancer, with approximation to the exact Poisson test used to obtain confidence intervals (CI) and p values.

RESULTS

Of 3066 patients with renal cortical neoplasms, 267 had a second primary cancer; the five most common in men were prostate, colorectal, bladder, lung, and non-Hodgkin's lymphoma; the five most common in women were breast, colorectal, lung, endometrium, and thyroid. Men demonstrated higher than expected thyroid cancer rate (SIR 5.0; 95 % CI 1.83-10.88, p = 0.002), and women had higher than expected rates of stomach cancer (SIR 5.0; 95 % CI 1.61-11.67, p = 0.004) and thyroid cancer (SIR 4.62; 95 % CI 1.69-10.05, p = 0.003).

CONCLUSIONS

The incidence of certain types of second malignancies may be higher in patients after diagnosis of renal cortical neoplasms compared to the general population. These observations can inform clinical follow-up in kidney cancer survivorship and future research studies.

Autism Linked to Increased Oncogene Mutations but Decreased Cancer Rate

Autism spectrum disorder (ASD) is one phenotypic aspect of many monogenic, hereditary cancer syndromes. Pleiotropic effects of cancer genes on the autism phenotype could lead to repurposing of oncology medications to treat this increasingly prevalent neurodevelopmental condition for which there is currently no treatment. To explore this hypothesis we sought to discover whether autistic patients more often have rare coding, single-nucleotide variants within tumor suppressor and oncogenes and whether autistic patients are more often diagnosed with neoplasms. Exome-sequencing data from the ARRA Autism Sequencing Collaboration was compared to that of a control cohort from the Exome Variant Server database revealing that rare, coding variants within oncogenes were enriched for in the ARRA ASD cohort (p<1.0 x 10(-8)). In contrast, variants were not significantly enriched in tumor suppressor genes. Phenotypically, children and adults with ASD exhibited a protective effect against cancer, with a frequency of 1.3% vs. 3.9% (p<0.001), but the protective effect decreased with age. The odds ratio of neoplasm for those with ASD relative to controls was 0.06 (95% CI: 0.02, 0.19; p<0.0001) in the 0 to 14 age group; 0.35 (95% CI: 0.14, 0.87; p = 0.024) in the 15 to 29 age group; 0.41 (95% CI: 0.15, 1.17; p = 0.095) in the 30 to 54 age group; and 0.49 (95% CI: 0.14, 1.74; p = 0.267) in those 55 and older. Both males and females demonstrated the protective effect. These findings suggest that defects in cellular proliferation, and potentially senescence, might influence both autism and neoplasm, and already approved drugs targeting oncogenic pathways might also have therapeutic value for treating autism.

Retrospective Review of MET Gene Mutations

C-MET proto-oncogene is a tyrosine kinase situated on chromosome 7. C-MET and its ligand hepatocyte growth factor/scatter factor (HGF/SF) play a role in proliferation, differentiation and organ development. C-MET genetic aberrations are found associated with driving tumorigenesis. In this retrospective study, we reviewed molecular analysis data gathered from a cancer institute during a two-year period (2010-2012). Upon detection of tumors harboring c-MET mutations, we determined the status of the other mutations tested and evaluated c-MET expression by fluorescent in-situ hybridization (FISH). Our search resulted in identification of 134 c-MET mutations, 44% of which had mutations of at least one of the other genes tested. No c-MET expression aberrancy was detected in this subset by FISH. Survival amongst the patients with surgically resected metastatic colorectal cancers (CRC) was slightly better in those with only a c-MET mutation compared to those with no mutation detected, although the difference was not statistically significant. When c-MET inhibition becomes an integrated part of chemotherapy practice, our observed frequency of co-mutations will be an argument for utilizing c-MET targeted treatment in combination with other targeted drugs and therapeutic strategies. Larger studies can aid to further parse out c-MET prognostic and therapeutic significance.

Association Analysis of MET Gene Polymorphism with Papillary Thyroid Carcinoma in a Chinese Population

To investigate the association of MET SNPs with gender disparity in thyroid tumors, as well as the metastasis and prognosis of patients, 858 patients with papillary thyroid carcinoma (PTC), 556 patients with nodular goiter, and 896 population-based normal controls were recruited. The genotyping of MET SNPs was carried out using the Sequenom MassARRAY system. The distribution of MET SNPs (rs1621 and rs6566) was different among groups. Gender stratification analysis revealed a significant association between the rs1621 genotype and PTC in female patients (P = 0.037), but not in male patients (P > 0.05). For female patients, the rs1621 AG genotype was significantly higher in patients with PTC than in normal controls (P = 0.01) and revealed an increasing risk of PTC (OR: 1.465, 95% CI: 1.118-1.92). However, association analysis of the rs1621 genotype with metastasis and prognosis revealed no significant correlation in both male and female patients. The findings of our study showed that polymorphism of SNP locus rs1621 in MET gene may be associated with gender disparity in PTC. Higher AG genotypes in rs1621 were correlated with PTC in female patients, but not in male patients.

Advanced thyroid cancers: new era of treatment

Since chemotherapy has been shown to be unsuccessful in case of advanced thyroid carcinomas, the research for new therapies is fundamental. Clinical trials of many tyrosine kinase inhibitors as well as anti-angiogenic inhibitors suggest that patients with thyroid cancer could have an advantage with new target therapy. Recently, Food and Drug Administration approved two targeted therapies, vandetanib and cabozantinib for the treatment of metastatic thyroid carcinomas with acceptable outcome. We summarized the results and the toxic effects associated with these treatments reported in clinical trials. Future trials should aim at combinations of targeted agents with or without other treatment modalities to obtain a more effective result in thyroid carcinoma treatment.

Update on medullary thyroid cancer

Medullary thyroid carcinoma (MTC) is a rare type of thyroid cancer, demonstrating variable behavior from indolent disease to highly aggressive, progressive disease. There are distinguishing phenotypic features of sporadic and hereditary MTC. Activation or overexpression of cell surface receptors and up-regulation of intracellular signaling pathways in hereditary and sporadic MTC are involved in the disease pathogenesis. There has been an exponential rise in clinical trials with investigational agents, leading to approval of 2 medications for progressive, advanced MTC. Developments in understanding the pathogenesis of MTC will hopefully lead to more effective and less toxic treatments of this rare but difficult to treat cancer.

Personalization of targeted therapy in advanced thyroid cancer

Although generally the prognosis of differentiated thyroid carcinoma (DTC) is good, approximately 5% of people are likely to develop metastases which fail to respond to radioactive iodine, and other traditional therapies, exhibiting a more aggressive behavior. Nowadays, therapy is chosen and implemented on a watch-and-wait basis for most DTC patients. Which regimen is likely to work best is decided on the basis of an individual's clinical information, but only data referring to outcomes of groups of patients are employed. To predict the best course of therapy, an individual patient's biologic data is rarely employed in a systematic way. Anyway, the use of not expensive individual genomic analysis could lead us to a new era of patient-specific and personalized care. Recently, key targets that are now being evaluated in the clinical setting have been evidenced in the pathogenesis of these diseases. Some of the known genetic alterations playing a crucial role in the development of thyroid cancer include B-Raf gene mutations, rearranged during transfection/ papillary thyroid carcinoma gene rearrangements, and vascular endothelial growth factor receptor-2 angiogenesis pathways. The development of targeted novel compounds able to induce clinical responses and stabilization of disease has overcome the lack of effective therapies for DTC, which are resistant to radioiodine and thyroid stimulating hormone-suppressive therapy. Interestingly, the best responses have been demonstrated in patients treated with anti-angiogenic inhibitors such as vandetanib and XL184 in medullary thyroid cancer, and sorafenib in papillary and follicular DTC.

The risk of second cancers after diagnosis of primary thyroid cancer is elevated in thyroid microcarcinomas

BACKGROUND

Thyroid cancers have increased dramatically over the past few decades. Comorbidities may be important, and previous studies have indicated elevated second cancer risk after initial primary thyroid cancers. This study examined the risk of second cancers after development of a thyroid cancer, primary utilizing the Surveillance, Epidemiology, and End Results (SEER) program database.

METHODS

The cohort consisted of men and women diagnosed with first primary thyroid cancer who were reported to a SEER database in 1973-2008 (n=52,103). Standardized incidence ratios (SIR) were calculated for all secondary cancers. Confidence intervals and p-values are at 0.05 significance alpha level and are two-sided based on Poisson exact methods.

RESULTS

In this cohort, 4457 individuals developed second cancers. The risk of developing second cancers after a primary thyroid cancer varied from 10% to 150% depending on different cancer types. Cancers in all sites, breast, skin, prostate, kidney, brain, salivary gland, second thyroid, lymphoma, myeloma, and leukemia were elevated. The magnitude of the risk varied by histology, tumor size, calendar year of first primary thyroid cancer diagnosis, and the treatment of the primary thyroid cancer. The risk of a second cancer was elevated in patients whose first primary thyroid carcinomas were small, or were diagnosed after 1994, or in whom some form of radiation treatment was administered.

CONCLUSIONS

This large population-based analysis of second cancers among thyroid cancer patients suggests that there was an increase of second cancers in all sites, and the most commonly elevated second cancers were the salivary gland and kidney. Additionally, the increase in second cancers in patients with recently diagnosed thyroid microcarcinomas (<10 mm) suggests that aggressive radiation treatment of the first primary thyroid cancer, the environment, and genetic susceptibility, may increase the risk of a second cancer.

Cellular signaling pathway alterations and potential targeted therapies for medullary thyroid carcinoma

Parafollicular C-cell-derived medullary thyroid cancer (MTC) comprises 3% to 4% of all thyroid cancers. While cytotoxic treatments have been shown to have limited efficacy, targeted molecular therapies that inhibit rearranged during transfection (RET) and other tyrosine kinase receptors that are mainly involved in angiogenesis have shown great promise in the treatment of metastatic or locally advanced MTC. Multi-tyrosine kinase inhibitors such as vandetanib, which is already approved for the treatment of progressive MTC, and cabozantinib have shown distinct advantages with regard to rates of disease response and control. However, these types of tyrosine kinase inhibitor compounds are able to concurrently block several types of targets, which limits the understanding of RET as a specific target. Moreover, important resistances to tyrosine kinase inhibitors can occur, which limit the long-term efficacy of these treatments. Deregulated cellular signaling pathways and genetic alterations in MTC, particularly the activation of the RAS/mammalian target of rapamycin (mTOR) cascades and RET crosstalk signaling, are now emerging as novel and potentially promising therapeutic treatments for aggressive MTC.

MET/HGF Signaling Pathway in Ovarian Carcinoma: Clinical Implications and Future Direction

The HGF/MET signaling pathway is abnormal in numerous cancers including ovarian cancer. MET is expressed in 70% of human cancer and it is overexpressed in 30% of ovarian cases and cancer cell lines. The HGF/MET pathway plays a role in the initiation and progression of ovarian cancer through the most distinctive biologic program known as “invasive growth” which is accomplished through a coordinated activation of cell motility, invasiveness, degradation of extracellular matrix, survival, and proliferation. Because of its ubiquitous role in cancer, the MET axis seems to be an attractive target for cancer therapy. Numerous HGF/MET pathway inhibitor compounds are already in use in clinical trials in various solid tumors. In this paper, we will discuss the HGF/MET pathway in ovarian cancer, its clinical significance, and its potential use as a target therapy in the future.

MET: a promising anticancer therapeutic target

The MET pathway is dysregulated in many human cancers and promotes tumour growth, invasion and dissemination. Abnormalities in MET signalling have been reported to correlate with poor clinical outcomes and drug resistance in patients with cancer. Thus, MET has emerged as an attractive target for cancer therapy. Several MET inhibitors have been introduced into the clinic, and are currently in all phases of clinical trials. In general, initial results from these studies indicate only a modest benefit in unselected populations. In this Review, we discuss current challenges in developing MET inhibitors--including identification of predictive biomarkers--as well as the most-efficient ways to combine these drugs with other targeted agents or with classic chemotherapy or radiotherapy.

Differentiated thyroid cancer: management of patients with radioiodine nonresponsive disease

Differentiated thyroid carcinoma (papillary and follicular) has a favorable prognosis with an 85% 10-year survival. The patients that recur often require surgery and further radioactive iodine to render them disease-free. Five percent of thyroid cancer patients, however, will eventually succumb to their disease. Metastatic thyroid cancer is treated with radioactive iodine if the metastases are radioiodine avid. Cytotoxic chemotherapies for advanced or metastatic noniodine avid thyroid cancers show no prolonged responses and in general have fallen out of favor. Novel targeted therapies have recently been discovered that have given rise to clinical trials for thyroid cancer. Newer aberrations in molecular pathways and oncogenic mutations in thyroid cancer together with the role of angiogenesis in tumor growth have been central to these discoveries. This paper will focus on the management and treatment of metastatic differentiated thyroid cancers that do not take up radioactive iodine.

New treatment modalities in advanced thyroid cancer

BACKGROUND

Thyroid cancer is a heterogeneous disease that is classified into differentiated thyroid carcinoma (DTC), undifferentiated/anaplastic thyroid carcinoma (ATC) and medullary thyroid carcinoma. Results of conventional treatment modalities in advanced thyroid cancer have been disappointing and therefore, new therapies are needed.

METHODS

We searched PubMed, The Cochrane Library, Medline and EMBASE databases and abstracts published in annual proceedings for new treatment modalities in advanced thyroid cancer. We also searched for ongoing trials in www.clinicaltrials.gov.

RESULTS

Six phase I, 17 phase II and 1 phase III trials with tyrosine kinase inhibitors were carried out. We found 2 pilot studies and 11 phase II trials with redifferentiation therapies, mainly in DTC. For antiproliferative approaches, three phase I and four phase II trials were found. Immunomodulatory gene therapy was tested in a pilot study in ATC patients. Two phase II trials were carried out with immunotherapy. One phase I and nine phase II trials were found with radionucleotide therapy in patients with DTC.

CONCLUSION

The developments in the treatment of advanced thyroid cancer are intriguing. Future trials should aim at combinations of targeted agents with or without other treatment modalities, and will hopefully contribute to further improvement of outcomes.

Activating mutation in MET oncogene in familial colorectal cancer

Background

In developed countries, the lifetime risk of developing colorectal cancer (CRC) is 5%, and it is the second leading cause of death from cancer. The presence of family history is a well established risk factor with 25-35% of CRCs attributable to inherited and/or familial factors. The highly penetrant inherited colon cancer syndromes account for approximately 5%, leaving greater than 20% without clear genetic definition. Familial colorectal cancer has been linked to chromosome 7q31 by multiple affected relative pair studies. The MET proto-oncogene which resides in this chromosomal region is considered a candidate for genetic susceptibility.

Methods

MET exons were amplified by PCR from germline DNA of 148 affected sibling pairs with colorectal cancer. Amplicons with altered sequence were detected with high-resolution melt-curve analysis using a LightScanner (Idaho Technologies). Samples demonstrating alternative melt curves were sequenced. A TaqMan assay for the specific c.2975C >T change was used to confirm this mutation in a cohort of 299 colorectal cancer cases and to look for allelic amplification in tumors.

Results

Here we report a germline non-synonymous change in the MET proto-oncogene at amino acid position T992I (also reported as MET p.T1010I) in 5.2% of a cohort of sibling pairs affected with CRC. This genetic variant was then confirmed in a second cohort of individuals diagnosed with CRC and having a first degree relative with CRC at prevalence of 4.1%. This mutation has been reported in cancer cells of multiple origins, including 2.5% of colon cancers, and in <1% in the general population. The threonine at amino acid position 992 lies in the tyrosine kinase domain of MET and a change to isoleucine at this position has been shown to promote metastatic behavior in cell-based models. The average age of CRC diagnosis in patients in this study is 63 years in mutation carriers, which is 8 years earlier than the general population average for CRC.

Conclusions

Although the MET p.T992I genetic mutation is commonly found in somatic colorectal cancer tissues, this is the first report also implicating this MET genetic mutation as a germline inherited risk factor for familial colorectal cancer. Future studies on the cancer risks associated with this mutation and the prevalence in different at-risk populations will be an important extension of this work to define the clinical significance.

Development of c-MET pathway inhibitors

INTRODUCTION

The aberrantly upregulated c-mesenchymal-epithelia transition factor (c-MET) signaling pathway has been considered to be an attractive target for cancer intervention owing to the important roles it plays in tumor formation, progression, metastasis, angiogenesis and drug resistance. Based on the historical preclinical evidence, a number of c-MET pathway targeted agents are being developed in the clinic, and recent clinical data have begun to provide some insight into which tumor types and patient populations a c-MET pathway inhibitor may be beneficial for.

AREAS COVERED

Through reviewing recent publications in the literature and information disclosed in other public forums, we describe the current understanding of c-MET biology in human malignancies and discuss the latest progress in the development of c-MET pathway inhibitors for cancer treatment.

EXPERT OPINION

The c-MET pathway inhibitors currently being evaluated in the clinic have demonstrated compelling evidence of clinical activity in different cancer types and may provide significant therapeutic opportunities. The challenges, however, are to identify the tumor types and patient populations that benefit most, and find the most effective combinations of therapies while minimizing potential toxicity.

Novel molecular targeted therapies for refractory thyroid cancer

The incidence of thyroid cancer continues to increase and this neoplasia remains the most common endocrine malignancy. No effective systemic treatment currently exists for iodine-refractory differentiated or medullary thyroid carcinoma, but recent advances in the pathogenesis of these diseases have revealed key targets that are now being evaluated in the clinical setting. RET (rearranged during transfection)/PTC (papillary thyroid carcinoma) gene rearrangements, B-Raf gene mutations, and vascular endothelial growth factor receptor 2 (VEGFR-2) angiogenesis pathways are some of the known genetic alterations playing a crucial role in the development of thyroid cancer. Several novel agents have demonstrated promising responses. Of the treatments studied, multi-kinase inhibitors such as axitinib, sorafenib, motesanib, and XL-184 have shown to be the most effective by inducing clinical responses and stabilizing the disease process. Randomized clinical trials are currently evaluating these agents, results that may soon change the management of thyroid cancer.

Activated MET is a molecular prognosticator and potential therapeutic target for malignant peripheral nerve sheath tumors

PURPOSE

MET signaling has been suggested a potential role in malignant peripheral nerve sheath tumors (MPNST). Here, MET function and blockade were preclinically assessed.

EXPERIMENTAL DESIGN

Expression levels of MET, its ligand hepatocyte growth factor (HGF), and phosphorylated MET (pMET) were examined in a clinically annotated MPNST tissue microarray (TMA) incorporating univariable and multivariable statistical analyses. Human MPNST cells were studied in vitro and in vivo; Western blot (WB) and ELISA were used to evaluate MET and HGF expression, activation, and downstream signaling. Cell culture assays tested the impact of HGF-induced MET activation and anti-MET-specific siRNA inhibition on cell proliferation, migration, and invasion; in vivo gel-foam assays were used to evaluate angiogenesis. Cells stably transduced with anti-MET short hairpin RNA (shRNA) constructs were tested for growth and metastasis in severe combined immunodeficient (SCID) mice. The effect of the tyrosine kinase inhibitor XL184 (Exelixis) targeting MET/VEGFR2 (vascular endothelial growth factor receptor 2) on local and metastatic MPNST growth was examined in vivo.

RESULTS

All three markers were expressed in MPNST human samples; pMET expression was an independent prognosticator of poor patient outcome. Human MPNST cell lines expressed MET, HGF, and pMET. MET activation increased MPNST cell motility, invasion, angiogenesis, and induced matrix metalloproteinase-2 (MMP2) and VEGF expression; MET knockdown had inverse effects in vitro and markedly decreased local and metastatic growth in vivo. XL184 abrogated human MPNST xenograft growth and metastasis in SCID mice.

CONCLUSIONS

Informative prognosticators and novel therapies are crucially needed to improve MPNST management and outcomes. We show an important role for MET in MPNST, supporting continued investigation of novel anti-MET therapies in this clinical context.

Targeted therapies for thyroid tumors

Systemic chemotherapies for advanced or metastatic thyroid carcinomas have been of only limited effectiveness. For patients with differentiated or medullary carcinomas unresponsive to conventional treatments, novel therapies are needed to improve disease outcomes. Multiple novel therapies primarily targeting angiogenesis have entered clinical trials for metastatic thyroid carcinoma. Partial response rates up to 30% have been reported in single-agent studies, but prolonged disease stabilization is more commonly observed. The most successful agents target the vascular endothelial growth factor receptors, with potential targets including the mutant kinases associated with papillary and medullary oncogenesis. Two drugs approved for other malignancies, sorafenib and sunitinib, have had promising preliminary results reported, and are being used selectively for patients who do not qualify for clinical trials. At least one randomized, placebo-controlled phase III trial has been successfully completed, showing improved progression-free survival in patients with advanced or metastatic medullary thyroid carcinoma treated with vandetanib. Randomized trials for other agents are currently underway. Treatment for patients with metastatic or advanced thyroid carcinoma now emphasizes clinical trial opportunities for novel agents with considerable promise. Alternative options now exist for use of tyrosine kinase inhibitors that are well tolerated and may prove worthy of regulatory approval for this disease.

Analysis of Somatic Mutations in Cancer: Molecular Mechanisms of Activation in the ErbB Family of Receptor Tyrosine Kinases

The ErbB/EGFR/HER family of kinases consists of four homologous receptor tyrosine kinases which are important regulatory elements in many cellular processes, including cell proliferation, differentiation, and migration. Somatic mutations in, or over-expression of, the ErbB family is found in many cancers and is correlated with a poor prognosis; particularly, clinically identified mutations found in non-small-cell lung cancer (NSCLC) of ErbB1 have been shown to increase its basal kinase activity and patients carrying these mutations respond remarkably to the small tyrosine kinase inhibitor gefitinib. Here, we analyze the potential effects of the currently catalogued clinically identified mutations in the ErbB family kinase domains on the molecular mechanisms of kinase activation. Recently, we identified conserved networks of hydrophilic and hydrophobic interactions characteristic to the active and inactive conformation, respectively. Here, we show that the clinically identified mutants influence the kinase activity in distinctive fashion by affecting the characteristic interaction networks.

MET receptor sequence variants R970C and T992I lack transforming capacity

High-throughput sequencing promises to accelerate the discovery of sequence variants, but distinguishing oncogenic mutations from irrelevant "passenger" mutations remains a major challenge. Here we present an analysis of two sequence variants of the MET receptor (hepatocyte growth factor receptor) R970C and T992I (also designated R988C and T1010I). Previous reports indicated that these sequence variants are transforming and contribute to oncogenesis. We screened patients with chronic lymphocytic leukemia (CLL), acute myeloid leukemia (AML), chronic myelomonocytic leukemia (CMML), colorectal cancer, endometrial cancer, thyroid cancer, or melanoma, as well as individuals without cancer, and found these variants at low frequencies in most cohorts, including normal individuals. No evidence of increased phosphorylation or transformative capacity by either sequence variant was found. Because small-molecule inhibitors for MET are currently in development, it will be important to distinguish between oncogenic sequence variants and rare single-nucleotide polymorphisms to avoid the use of unnecessary, and potentially toxic, cancer therapy agents.

Targeted therapy of thyroid cancer

Systemic chemotherapies for advanced or metastatic thyroid carcinomas have been of only limited effectiveness. For patients with differentiated or medullary carcinomas unresponsive to conventional treatments, novel therapies are needed to improve disease outcomes. Multiple novel therapies primarily targeting angiogenesis have entered clinical trials for metastatic thyroid carcinoma. Partial response rates up to 30% have been reported in single agent studies, but prolonged disease stabilization is more commonly seen. The most successful agents target the vascular endothelial growth factor receptors, with potential targets including the mutant kinases associated with papillary and medullary oncogenesis. Two drugs approved for other malignancies, sorafenib and sunitinib, have had promising preliminary results reported, and are being used selectively for patients who do not qualify for clinical trials. Additional agents targeting tumor vasculature, nuclear receptors, epigenetic abnormalities, and the immune response to neoplasia have also been investigated. Randomized trials for several agents are underway that may lead to eventual drug approval for thyroid cancer. Treatment for patients with metastatic or advanced thyroid carcinoma now emphasizes clinical trial opportunities for novel agents with considerable promise. Alternative options now exist for use of tyrosine kinase inhibitors that are well tolerated and may prove worthy of regulatory approval for this disease.

Molecularly targeted therapies for thyroid cancers

OBJECTIVE

To review the emerging evidence that therapies targeting key oncogenic and signaling kinases can be effective in treatment of advanced thyroid carcinomas.

METHODS

With use of PubMed and Google Scholar, a systematic review was performed of publications and scientific presentations summarizing pertinent clinical trials.

RESULTS

Studies of numerous inhibitors of BRAF, vascular endothelial growth factor receptor, and RET kinases indicate that patients with progressive or metastatic thyroid carcinoma can benefit from therapy with these novel agents. Severe toxic effects, however, are associated with these treatments, and caution is recommended in their use.

CONCLUSION

Further trials and identification of improved therapeutic targeting should lead to development of more effective treatments of thyroid carcinomas.

Tyrosine kinase inhibitors and the thyroid

Protein tyrosine kinase inhibitors (TKIs) have emerged as significant targets for novel cancer therapies. For patients with differentiated or medullary carcinomas unresponsive to conventional treatments, multiple novel therapies primarily targeting angiogenesis have entered clinical trials. Partial response rates up to 30% have been reported in single-agent studies, but prolonged disease stabilisation is more commonly seen. The most successful agents target the vascular endothelial growth factor receptors. Sorafenib and sunitinib have had promising preliminary results reported and are being used selectively for patients who do not qualify for clinical trials. Treatment for patients with metastatic or advanced thyroid carcinoma now emphasises clinical trial opportunities for novel agents with considerable promise. Adverse effects on thyroid function and thyroid hormone metabolism have also been seen with several TKIs, necessitating prospective thyroid function testing for all patients starting therapy.

Ethnic differences and functional analysis of MET mutations in lung cancer

PURPOSE

African Americans have higher incidence and poorer response to lung cancer treatment compared with Caucasians. However, the underlying molecular mechanisms for the significant ethnic difference are not known. The present study examines the ethnic differences in the type and frequency of MET proto-oncogene (MET) mutation in lung cancer and correlated them with other frequently mutated genes such as epidermal growth factor receptor (EGFR), KRAS2, and TP53.

EXPERIMENTAL DESIGN

Using tumor tissue genomic DNA from 141 Asian, 76 Caucasian, and 66 African American lung cancer patients, exons coding for MET and EGFR were PCR amplified, and mutations were detected by sequencing. Mutation carriers were further screened for KRAS2 and TP53 mutations. Functional implications of important MET mutations were explored by molecular modeling and hepatocyte growth factor binding studies.

RESULTS

Unlike the frequently encountered somatic mutations in EGFR, MET mutations in lung tumors were germline. MET-N375S, the most frequent mutation of MET, occurred in 13% of East Asians compared with none in African Americans. The frequency of MET mutations was highest among male smokers and squamous cell carcinoma. The MET-N375S mutation seems to confer resistance to MET inhibition based on hepatocyte growth factor ligand binding, molecular modeling, and apoptotic susceptibility to MET inhibitor studies.

CONCLUSIONS

MET in lung cancer tissues contained nonsynonymous mutations in the semaphorin and juxtamembrane domains but not in the tyrosine kinase domain. All the MET mutations were germline. East Asians, African-Americans, and Caucasians had different MET genotypes and haplotypes. MET mutations in the semaphorin domain affected ligand binding.

Beyond RET: potential therapeutic approaches for advanced and metastatic medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) is a rare calcitonin-producing neuroendocrine tumour that originates from the parafollicular C-cells of the thyroid gland. The RET proto-oncogene encodes the RET receptor tyrosine kinase, which has essential roles in cell survival, differentiation and proliferation. Activating mutations of RET are associated with the pathogenesis of MTC and have been demonstrated in nearly all hereditary and in 30-50% of sporadic MTC cases, making this receptor an excellent target for small-molecule inhibitors for this tumour. Clinical trials of small organic inhibitors of tyrosine kinase receptors (TKIs) targeting the RET receptor have shown efficacy for treatment of metastatic MTC with 30-50% of patients responding to these agents. Despite the importance of the RET receptor in MTC, it is clear that other signal transduction pathways, tyrosine kinase receptors, and tumour suppressor genes are involved in MTC tumourigenesis and progression. A better understanding of molecular cross-talk between these signal pathways and the RET receptor may lead to combinatorial therapy that will improve outcomes beyond what is currently possible with RET-directed TKIs. Finally, there is evidence that immunological-based therapy using dendritic cell vaccination strategies have been effective for reducing tumour mass in a small number of patients. The identification of additional MTC-specific tumour antigens and a better understanding of specific epitopes in these tumour antigens may lead to improvement of response rates.

Advances in chemotherapy of differentiated epithelial and medullary thyroid cancers

CONTEXT

Systemic chemotherapies for advanced or metastatic thyroid carcinomas have been of only limited effectiveness. For patients with differentiated or medullary carcinomas unresponsive to conventional treatments, novel therapies are needed to improve disease outcomes.

EVIDENCE ACQUISITION

The PubMed and Google Scholar search engines were used to identify publications and peer-reviewed meeting presentations addressing chemotherapy and targeted therapy for differentiated or medullary carcinoma.

EVIDENCE SYNTHESIS

Multiple novel therapies primarily targeting angiogenesis have entered clinical trials for metastatic thyroid carcinoma. Partial response rates up to 30% have been reported in single agent studies, but prolonged disease stabilization is more commonly seen. The most successful agents target the vascular endothelial growth factor receptors, with potential targets including the mutant kinases associated with papillary and medullary oncogenesis. Two drugs approved for other malignancies, sorafenib and sunitinib, have had promising preliminary results reported, and are being used selectively for patients who do not qualify for clinical trials. Randomized trials for several agents are underway that may lead to eventual drug approval for thyroid cancer.

CONCLUSION

Treatment for patients with metastatic or advanced thyroid carcinoma now emphasizes clinical trial opportunities for novel agents with considerable promise. Alternative options now exist for use of tyrosine kinase inhibitors that are well tolerated and may prove worthy of regulatory approval for this disease.

Receptor tyrosine kinase inhibitors in thyroid cancer

Thyroid cancer is frequently associated with the oncogenic conversion of receptor tyrosine kinases (RTKs) or their downstream signalling molecules. Hence, there is a strong biological rationale for assessing the efficacy of RTK blockade to treat patients who are resistant to or not candidates for treatment with radioactive iodine. The first results of clinical trials based on the use of RTK inhibitors in thyroid cancer patients have recently been published. Here we discuss targeting of specific RTKs as a potential therapeutic strategy for the treatment of thyroid cancer.

Early clinical studies of novel therapies for thyroid cancers

Historically, systemic therapies for advanced, metastatic thyroid carcinomas have been poorly effective. However, as a result of a confluence of increasing knowledge of the biologic basis for thyroid cancer development and progression, identification of therapeutic agents that could target these biologic abnormalities, and enthusiasm for research by both funding agencies as well as patients, multiple clinical trials have been initiated and successfully completed during the past several years. This article focuses on findings from key studies that reflect the new paradigms for treatment.

RET as a diagnostic and therapeutic target in sporadic and hereditary endocrine tumors

The RET gene encodes a receptor tyrosine kinase that is expressed in neural crest-derived cell lineages. The RET receptor plays a crucial role in regulating cell proliferation, migration, differentiation, and survival through embryogenesis. Activating mutations in RET lead to the development of several inherited and noninherited diseases. Germline point mutations are found in the cancer syndromes multiple endocrine neoplasia (MEN) type 2, including MEN 2A and 2B, and familial medullary thyroid carcinoma. These syndromes are autosomal dominantly inherited. The identification of mutations associated with these syndromes has led to genetic testing to identify patients at risk for MEN 2 and familial medullary thyroid carcinoma and subsequent implementation of prophylactic thyroidectomy in mutation carriers. In addition, more than 10 somatic rearrangements of RET have been identified from papillary thyroid carcinomas. These mutations, as those found in MEN 2, induce oncogenic activation of the RET tyrosine kinase domain via different mechanisms, making RET an excellent candidate for the design of molecular targeted therapy. Recently, various kinds of therapeutic approaches, such as tyrosine kinase inhibition, gene therapy with dominant negative RET mutants, monoclonal antibodies against oncogene products, and nuclease-resistant aptamers that recognize and inhibit RET have been developed. The use of these strategies in preclinical models has provided evidence that RET is indeed a potential target for selective cancer therapy. However, a clinically useful therapeutic option for treating patients with RET-associated cancer is still not available.

Pathogenetic mechanisms in thyroid follicular-cell neoplasia

Thyroid cancer is one of the few malignancies that are increasing in incidence. Recent advances have improved our understanding of its pathogenesis; these include the identification of genetic alterations that activate a common effector pathway involving the RET-Ras-BRAF signalling cascade, and other unique chromosomal rearrangements. Some of these have been associated with radiation exposure as a pathogenetic mechanism. Defects in transcriptional and post-transcriptional regulation of adhesion molecules and cell-cycle control elements seem to affect tumour progression. This information can provide powerful ancillary diagnostic tools and can also be used to identify new therapeutic targets.