Publications by authors named "Jeffrey A Knauf"

52 Publications

Co-inhibition of SMAD and MAPK signaling enhances 124I uptake in BRAF-mutant thyroid cancers.

Endocr Relat Cancer 2021 May 18;28(6):391-402. Epub 2021 May 18.

Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, New York, USA.

Constitutive MAPK activation silences genes required for iodide uptake and thyroid hormone biosynthesis in thyroid follicular cells. Accordingly, most BRAFV600E papillary thyroid cancers (PTC) are refractory to radioiodide (RAI) therapy. MAPK pathway inhibitors rescue thyroid-differentiated properties and RAI responsiveness in mice and patient subsets with BRAFV600E-mutant PTC. TGFB1 also impairs thyroid differentiation and has been proposed to mediate the effects of mutant BRAF. We generated a mouse model of BRAFV600E-PTC with thyroid-specific knockout of the Tgfbr1 gene to investigate the role of TGFB1 on thyroid-differentiated gene expression and RAI uptake in vivo. Despite appropriate loss of Tgfbr1, pSMAD levels remained high, indicating that ligands other than TGFB1 were engaging in this pathway. The activin ligand subunits Inhba and Inhbb were found to be overexpressed in BRAFV600E-mutant thyroid cancers. Treatment with follistatin, a potent inhibitor of activin, or vactosertib, which inhibits both TGFBR1 and the activin type I receptor ALK4, induced a profound inhibition of pSMAD in BRAFV600E-PTCs. Blocking SMAD signaling alone was insufficient to enhance iodide uptake in the setting of constitutive MAPK activation. However, combination treatment with either follistatin or vactosertib and the MEK inhibitor CKI increased 124I uptake compared to CKI alone. In summary, activin family ligands converge to induce pSMAD in Braf-mutant PTCs. Dedifferentiation of BRAFV600E-PTCs cannot be ascribed primarily to activation of SMAD. However, targeting TGFβ/activin-induced pSMAD augmented MAPK inhibitor effects on iodine incorporation into BRAF tumor cells, indicating that these two pathways exert interdependent effects on the differentiation state of thyroid cancer cells.
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http://dx.doi.org/10.1530/ERC-21-0017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8183640PMC
May 2021

SWI/SNF Complex Mutations Promote Thyroid Tumor Progression and Insensitivity to Redifferentiation Therapies.

Cancer Discov 2021 May 14;11(5):1158-1175. Epub 2020 Dec 14.

Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, New York.

Mutations of subunits of the SWI/SNF chromatin remodeling complexes occur commonly in cancers of different lineages, including advanced thyroid cancers. Here we show that thyroid-specific loss of , or in mouse BRAF-mutant tumors promotes disease progression and decreased survival, associated with lesion-specific effects on chromatin accessibility and differentiation. As compared with normal thyrocytes, BRAF-mutant mouse papillary thyroid cancers have decreased lineage transcription factor expression and accessibility to their target DNA binding sites, leading to impairment of thyroid-differentiated gene expression and radioiodine incorporation, which is rescued by MAPK inhibition. Loss of individual SWI/SNF subunits in BRAF tumors leads to a repressive chromatin state that cannot be reversed by MAPK pathway blockade, rendering them insensitive to its redifferentiation effects. Our results show that SWI/SNF complexes are central to the maintenance of differentiated function in thyroid cancers, and their loss confers radioiodine refractoriness and resistance to MAPK inhibitor-based redifferentiation therapies. SIGNIFICANCE: Reprogramming cancer differentiation confers therapeutic benefit in various disease contexts. Oncogenic BRAF silences genes required for radioiodine responsiveness in thyroid cancer. Mutations in SWI/SNF genes result in loss of chromatin accessibility at thyroid lineage specification genes in -mutant thyroid tumors, rendering them insensitive to the redifferentiation effects of MAPK blockade..
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http://dx.doi.org/10.1158/2159-8290.CD-20-0735DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8102308PMC
May 2021

Genetics of Human Thyroid Cancer Cell Lines-Response.

Clin Cancer Res 2019 11;25(22):6883-6884

Division of Endocrinology, Metabolism and Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado.

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http://dx.doi.org/10.1158/1078-0432.CCR-19-2531DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7396876PMC
November 2019

Mouse Models as a Tool for Understanding Progression in Braf-Driven Thyroid Cancers.

Endocrinol Metab (Seoul) 2019 03 15;34(1):11-22. Epub 2019 Feb 15.

Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA.

The development of next generation sequencing (NGS) has led to marked advancement of our understanding of genetic events mediating the initiation and progression of thyroid cancers. The NGS studies have confirmed the previously reported high frequency of mutually-exclusive oncogenic alterations affecting and proto-oncogenes in all stages of thyroid cancer. Initially identified by traditional sequencing approaches, the NGS studies also confirmed the acquisition of alterations that inactivate tumor protein p53 () and activate phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha () in advanced thyroid cancers. Novel alterations, such as those in telomerase reverse transcriptase () promoter and mating-type switching/sucrose non-fermenting (SWI/SNF) complex, are also likely to promote progression of the -driven thyroid cancers. A number of genetically engineered mouse models (GEMM) of -driven thyroid cancer have been developed to investigate thyroid tumorigenesis mediated by oncogenic BRAF and to explore the role of genetic alterations identified in the genomic analyses of advanced thyroid cancer to promote tumor progression. This review will discuss the various GEMMs that have been developed to investigate oncogenic -driven thyroid cancers.
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http://dx.doi.org/10.3803/EnM.2019.34.1.11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6435851PMC
March 2019

Comprehensive Genetic Characterization of Human Thyroid Cancer Cell Lines: A Validated Panel for Preclinical Studies.

Clin Cancer Res 2019 05 8;25(10):3141-3151. Epub 2019 Feb 8.

Division of Endocrinology, Metabolism and Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado.

Purpose: Thyroid cancer cell lines are valuable models but have been neglected in pancancer genomic studies. Moreover, their misidentification has been a significant problem. We aim to provide a validated dataset for thyroid cancer researchers.

Experimental Design: We performed next-generation sequencing (NGS) and analyzed the transcriptome of 60 authenticated thyroid cell lines and compared our findings with the known genomic defects in human thyroid cancers.

Results: Unsupervised transcriptomic analysis showed that 94% of thyroid cell lines clustered distinctly from other lineages. Thyroid cancer cell line mutations recapitulate those found in primary tumors (e.g., , , or gene fusions). Mutations in the promoter (83%) and (71%) were highly prevalent. There were frequent alterations in , , and of members of the SWI/SNF chromatin remodeling complex, mismatch repair, cell-cycle checkpoint, and histone methyl- and acetyltransferase functional groups. Copy number alterations (CNA) were more prevalent in cell lines derived from advanced versus differentiated cancers, as reported in primary tumors, although the precise CNAs were only partially recapitulated. Transcriptomic analysis showed that all cell lines were profoundly dedifferentiated, regardless of their derivation, making them good models for advanced disease. However, they maintained the BRAF versus RAS-dependent consequences on MAPK transcriptional output, which correlated with differential sensitivity to MEK inhibitors. Paired primary tumor-cell line samples showed high concordance of mutations. Complete loss of p53 function in heterozygous tumors was the most prominent event selected during immortalization.

Conclusions: This cell line resource will help inform future preclinical studies exploring tumor-specific dependencies.
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http://dx.doi.org/10.1158/1078-0432.CCR-18-2953DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6522280PMC
May 2019

Establishment and Characterization of Four Novel Thyroid Cancer Cell Lines and PDX Models Expressing the RET/PTC1 Rearrangement, BRAFV600E, or RASQ61R as Drivers.

Mol Cancer Res 2019 05 7;17(5):1036-1048. Epub 2019 Feb 7.

Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Colorado Anschutz Medical Campus, Aurora, Colorado.

Cancer cell lines are critical models to study tumor progression and response to therapy. In 2008, we showed that approximately 50% of thyroid cancer cell lines were redundant or not of thyroid cancer origin. We therefore generated new authenticated thyroid cancer cell lines and patient-derived xenograft (PDX) models using and feeder cell approaches, and characterized these models and . We developed four thyroid cancer cell lines, two derived from 2 different patients with papillary thyroid cancer (PTC) pleural effusions, CUTC5, and CUTC48; one derived from a patient with anaplastic thyroid cancer (ATC), CUTC60; and one derived from a patient with follicular thyroid cancer (FTC), CUTC61. One PDX model (CUTC60-PDX) was also developed. Short tandem repeat (STR) genotyping showed that each cell line and PDX is unique and match the original patient tissue. The CUTC5 and CUTC60 cells harbor the BRAF (V600E) mutation, the CUTC48 cell line expresses the RET/PTC1 rearrangement, and the CUTC61 cells have the HRAS (Q61R) mutation. Moderate to high levels of and variable levels of were detected in each cell line and PDX. The CUTC5 and CUTC60 cell lines form tumors in orthotopic and flank xenograft mouse models. IMPLICATIONS: We have developed the second RET/PTC1-expressing PTC-derived cell line in existence, which is a major advance in studying RET signaling. We have further linked all cell lines to the originating patients, providing a set of novel, authenticated thyroid cancer cell lines and PDX models to study advanced thyroid cancer.
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http://dx.doi.org/10.1158/1541-7786.MCR-18-1026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6711777PMC
May 2019

and Mutations Cooperate to Drive Thyroid Tumorigenesis through ATF4 and c-MYC.

Cancer Discov 2019 02 10;9(2):264-281. Epub 2018 Oct 10.

Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, New York.

Translation initiation is orchestrated by the cap binding and 43S preinitiation complexes (PIC). Eukaryotic initiation factor 1A (EIF1A) is essential for recruitment of the ternary complex and for assembling the 43S PIC. Recurrent mutations in papillary thyroid cancers are mutually exclusive with other drivers, including . mutations are enriched in advanced thyroid cancers, where they display a striking co-occurrence with , which cooperates to induce tumorigenesis in mice and isogenic cell lines. The C-terminal mutation is the most prevalent in advanced thyroid cancer. EIF1AX-A113splice variants stabilize the PIC and induce ATF4, a sensor of cellular stress, which is co-opted to suppress EIF2α phosphorylation, enabling a general increase in protein synthesis. RAS stabilizes c-MYC, an effect augmented by EIF1AX-A113splice. ATF4 and c-MYC induce expression of amino acid transporters and enhance sensitivity of mTOR to amino acid supply. These mutually reinforcing events generate therapeutic vulnerabilities to MEK, BRD4, and mTOR kinase inhibitors. SIGNIFICANCE: Mutations of component of the translation PIC, co-occur with in advanced thyroid cancers and promote tumorigenesis. drives an ATF4-induced dephosphorylation of EIF2α, resulting in increased protein synthesis. ATF4 also cooperates with c-MYC to sensitize mTOR to amino acid supply, thus generating vulnerability to mTOR kinase inhibitors. .
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http://dx.doi.org/10.1158/2159-8290.CD-18-0606DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6373451PMC
February 2019

Vemurafenib Redifferentiation of BRAF Mutant, RAI-Refractory Thyroid Cancers.

J Clin Endocrinol Metab 2019 05;104(5):1417-1428

Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York.

Context: BRAFV600E mutant thyroid cancers are often refractory to radioiodine (RAI).

Objectives: To investigate the utility and molecular underpinnings of enhancing lesional iodide uptake with the BRAF inhibitor vemurafenib in patients with RAI-refractory (RAIR).

Design: This was a pilot trial that enrolled from June 2014 to January 2016.

Setting: Academic cancer center.

Patients: Patients with RAIR, BRAF mutant thyroid cancer.

Intervention: Patients underwent thyrotropin-stimulated iodine-124 (124I) positron emission tomography scans before and after ~4 weeks of vemurafenib. Those with increased RAI concentration exceeding a predefined lesional dosimetry threshold (124I responders) were treated with iodine-131 (131I). Response was evaluated with imaging and serum thyroglobulin. Three patients underwent research biopsies to evaluate the impact of vemurafenib on mitogen-activated protein kinase (MAPK) signaling and thyroid differentiation.

Main Outcome Measure: The proportion of patients in whom vemurafenib increased RAI incorporation to warrant 131I.

Results: Twelve BRAF mutant patients were enrolled; 10 were evaluable. Four patients were 124I responders on vemurafenib and treated with 131I, resulting in tumor regressions at 6 months. Analysis of research tumor biopsies demonstrated that vemurafenib inhibition of the MAPK pathway was associated with increased thyroid gene expression and RAI uptake. The mean pretreatment serum thyroglobulin value was higher among 124I responders than among nonresponders (30.6 vs 1.0 ng/mL; P = 0.0048).

Conclusions: Vemurafenib restores RAI uptake and efficacy in a subset of BRAF mutant RAIR patients, probably by upregulating thyroid-specific gene expression via MAPK pathway inhibition. Higher baseline thyroglobulin values among responders suggest that tumor differentiation status may be a predictor of vemurafenib benefit.
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http://dx.doi.org/10.1210/jc.2018-01478DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6435099PMC
May 2019

Hgf/Met activation mediates resistance to BRAF inhibition in murine anaplastic thyroid cancers.

J Clin Invest 2018 08 20;128(9):4086-4097. Epub 2018 Aug 20.

Human Oncology and Pathogenesis Program.

Anaplastic thyroid carcinomas (ATCs) have a high prevalence of BRAF and TP53 mutations. A trial of vemurafenib in nonmelanoma BRAFV600E-mutant cancers showed significant, although short-lived, responses in ATCs, indicating that these virulent tumors remain addicted to BRAF despite their high mutation burden. To explore the mechanisms mediating acquired resistance to BRAF blockade, we generated mice with thyroid-specific deletion of p53 and dox-dependent expression of BRAFV600E, 50% of which developed ATCs after dox treatment. Upon dox withdrawal there was complete regression in all mice, although recurrences were later detected in 85% of animals. The relapsed tumors had elevated MAPK transcriptional output, and retained responses to the MEK/RAF inhibitor CH5126766 in vivo and in vitro. Whole-exome sequencing identified recurrent focal amplifications of chromosome 6, with a minimal region of overlap that included Met. Met-amplified recurrences overexpressed the receptor as well as its ligand Hgf. Growth, signaling, and viability of Met-amplified tumor cells were suppressed in vitro and in vivo by the Met kinase inhibitors PF-04217903 and crizotinib, whereas primary ATCs and Met-diploid relapses were resistant. Hence, recurrences are the rule after BRAF suppression in murine ATCs, most commonly due to activation of HGF/MET signaling, which generates exquisite dependency to MET kinase inhibitors.
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http://dx.doi.org/10.1172/JCI120966DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6118575PMC
August 2018

Tipifarnib Inhibits HRAS-Driven Dedifferentiated Thyroid Cancers.

Cancer Res 2018 08 14;78(16):4642-4657. Epub 2018 May 14.

Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, New York.

Of the three RAS oncoproteins, only HRAS is delocalized and inactivated by farnesyltransferase inhibitors (FTI), an approach yet to be exploited clinically. In this study, we treat mice bearing Hras-driven poorly differentiated and anaplastic thyroid cancers ( ) with the FTI tipifarnib. Treatment caused sustained tumor regression and increased survival; however, early and late resistance was observed. Adaptive reactivation of RAS-MAPK signaling was abrogated by selective RTK (i.e., EGFR, FGFR) inhibitors, but responses were ineffective , whereas combination of tipifarnib with the MEK inhibitor AZD6244 improved outcomes. A subset of tumor-bearing mice treated with tipifarnib developed acquired resistance. Whole-exome sequencing of resistant tumors identified a nonsense mutation and an activating mutation in at high allelic frequency, supporting the on-target effects of the drug. Cell lines modified with these genetic lesions recapitulated tipifarnib resistance This study demonstrates the feasibility of targeting Ras membrane association in cancers and predicts combination therapies that confer additional benefit. Tipifarnib effectively inhibits oncogenic HRAS-driven tumorigenesis and abrogating adaptive signaling improves responses. NF1 and GNAS mutations drive acquired resistance to Hras inhibition, supporting the on-target effects of the drug. .
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http://dx.doi.org/10.1158/0008-5472.CAN-17-1925DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6095730PMC
August 2018

Oncogene-induced senescence and its evasion in a mouse model of thyroid neoplasia.

Mol Cell Endocrinol 2018 01 23;460:24-35. Epub 2017 Jun 23.

Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Universita' Federico II c/o Istituto di Endocrinologia e Oncologia Sperimentale, CNR, Via S Pansini 5, 80131 Naples, Italy. Electronic address:

Here we describe a conditional doxycycline-dependent mouse model of RET/PTC3 (NCOA4-RET) oncogene-induced thyroid tumorigenesis. In these mice, after 10 days of doxycycline (dox) administration, RET/PTC3 expression induced mitogen activated protein kinase (MAPK) stimulation and a proliferative response which resulted in the formation of hyperplastic thyroid lesions. This was followed, after 2 months, by growth arrest accompanied by typical features of oncogene-induced senescence (OIS), including upregulation of p16INK4A and p21CIP, positivity at the Sudan black B, activation of the DNA damage response (DDR) markers γH2AX and pChk2 T68, and induction of p53 and p19ARF. After 5 months, about half of thyroid lesions escaped OIS and formed tumors that remained dependent on RET/PTC3 expression. This progression was accompanied by activation of AKT-FOXO1/3a pathway and increased serum TSH levels.
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http://dx.doi.org/10.1016/j.mce.2017.06.023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5741508PMC
January 2018

Genomic Alterations in Fatal Forms of Non-Anaplastic Thyroid Cancer: Identification of and as Novel Thyroid Cancer Genes Associated with Tumor Virulence.

Clin Cancer Res 2017 Oct 20;23(19):5970-5980. Epub 2017 Jun 20.

Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, New York.

Patients with anaplastic thyroid cancer (ATC) have a very high death rate. In contrast, deaths from non-anaplastic thyroid (NAT) cancer are much less common. The genetic alterations in fatal NAT cancers have not been reported. We performed next-generation sequencing of 410 cancer genes from 57 fatal NAT primary cancers. Results were compared with The Cancer Genome Atlas study (TCGA study) of papillary thyroid cancers (PTCs) and to the genomic changes reported in ATC. There was a very high prevalence of promoter mutations, comparable with that of ATC, and these co-occurred with and mutations. A high incidence of chromosome 1q gain was seen highlighting its importance in tumor aggressiveness. Two novel fusion genes - and - were identified. There was a high frequency of mutations in and these were mutually exclusive to promoter mutations and also to and mutations. In addition, a high frequency of mutations in was identified and these co-occurred with mutations and mutations. Compared with the PTCs in TCGA, there were higher frequencies of mutations in pathway effectors, subunits, and histone methyltransferases. These data support a model, whereby fatal NAT cancers arise from well-differentiated tumors through the accumulation of key additional genetic abnormalities. The high rate of promoter mutations, mutations, mutations, and chromosome 1q gain highlight their likely association with tumor virulence. .
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http://dx.doi.org/10.1158/1078-0432.CCR-17-1183DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5626586PMC
October 2017

Transposon mutagenesis identifies chromatin modifiers cooperating with in thyroid tumorigenesis and detects as a cancer gene.

Proc Natl Acad Sci U S A 2017 06 5;114(25):E4951-E4960. Epub 2017 Jun 5.

Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065;

Oncogenic mutations are present in 15-30% of thyroid carcinomas. Endogenous expression of mutant Ras is insufficient to initiate thyroid tumorigenesis in murine models, indicating that additional genetic alterations are required. We used Sleeping Beauty (SB) transposon mutagenesis to identify events that cooperate with Hras in thyroid tumor development. Random genomic integration of SB transposons primarily generated loss-of-function events that significantly increased thyroid tumor penetrance in mice. The thyroid tumors closely phenocopied the histological features of human RAS-driven, poorly differentiated thyroid cancers. Characterization of transposon insertion sites in the SB-induced tumors identified 45 recurrently mutated candidate cancer genes. These mutation profiles were remarkably concordant with mutated cancer genes identified in a large series of human poorly differentiated and anaplastic thyroid cancers screened by next-generation sequencing using the MSK-IMPACT panel of cancer genes, which we modified to include all SB candidates. The disrupted genes primarily clustered in chromatin remodeling functional nodes and in the PI3K pathway. , a component of a multiprotein complex with histone acetylase activity, scored as a significant SB hit. It was recurrently mutated in advanced human cancers and significantly co-occurred with or mutations. Expression of mutants cooperated with oncogenic RAS to induce thyroid cell proliferation, pointing to as a previously unrecognized cancer gene.
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http://dx.doi.org/10.1073/pnas.1702723114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5488945PMC
June 2017

Sustained ERK inhibition maximizes responses of BrafV600E thyroid cancers to radioiodine.

J Clin Invest 2016 11 26;126(11):4119-4124. Epub 2016 Sep 26.

Radioiodide (RAI) therapy of thyroid cancer exploits the relatively selective ability of thyroid cells to transport and accumulate iodide. Iodide uptake requires expression of critical genes that are involved in various steps of thyroid hormone biosynthesis. ERK signaling, which is markedly increased in thyroid cancer cells driven by oncogenic BRAF, represses the genetic program that enables iodide transport. Here, we determined that a critical threshold for inhibition of MAPK signaling is required to optimally restore expression of thyroid differentiation genes in thyroid cells and in mice with BrafV600E-induced thyroid cancer. Although the MEK inhibitor selumetinib transiently inhibited ERK signaling, which subsequently rebounded, the MEK inhibitor CKI suppressed ERK signaling in a sustained manner by preventing RAF reactivation. A small increase in ERK inhibition markedly increased the expression of thyroid differentiation genes, increased iodide accumulation in cancer cells, and thereby improved responses to RAI therapy. Only a short exposure to the drug was necessary to obtain a maximal response to RAI. These data suggest that potent inhibition of ERK signaling is required to adequately induce iodide uptake and indicate that this is a promising strategy for the treatment of BRAF-mutant thyroid cancer.
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http://dx.doi.org/10.1172/JCI89067DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5096947PMC
November 2016

NADPH Oxidase NOX4 Is a Critical Mediator of BRAF-Induced Downregulation of the Sodium/Iodide Symporter in Papillary Thyroid Carcinomas.

Antioxid Redox Signal 2017 05 22;26(15):864-877. Epub 2016 Aug 22.

1 UMR 8200 CNRS , Villejuif, France .

Aims: The BRAF oncogene, reported in 40%-60% of papillary thyroid cancer (PTC), has an important role in the pathogenesis of PTC. It is associated with the loss of thyroid iodide-metabolizing genes, such as sodium/iodide symporter (NIS), and therefore with radioiodine refractoriness. Inhibition of mitogen-activated protein kinase (MAPK) pathway, constitutively activated by BRAF, is not always efficient in resistant tumors suggesting that other compensatory mechanisms contribute to a BRAF adaptive resistance. Recent studies pointed to a key role of transforming growth factor β (TGF-β) in BRAF-induced effects. The reactive oxygen species (ROS)-generating NADPH oxidase NOX4, which is increased in PTC, has been identified as a new key effector of TGF-β in cancer, suggestive of a potential role in BRAF-induced thyroid tumors.

Results: Here, using two human BRAF-mutated thyroid cell lines and a rat thyroid cell line expressing BRAF in a conditional manner, we show that NOX4 upregulation is controlled at the transcriptional level by the oncogene via the TGF-β/Smad3 signaling pathway. Importantly, treatment of cells with NOX4-targeted siRNA downregulates BRAF-induced NIS repression. Innovation and Conclusion: Our results establish a link between BRAF and NOX4, which is confirmed by a comparative analysis of NOX4 expression in human (TCGA) and mouse thyroid cancers. Remarkably, analysis of human and murine BRAF-mutated thyroid tumors highlights that the level of NOX4 expression is inversely correlated to thyroid differentiation suggesting that other genes involved in thyroid differentiation in addition to NIS might be silenced by a mechanism controlled by NOX4-derived ROS. This study opens a new opportunity to optimize thyroid cancer therapy. Antioxid. Redox Signal. 26, 864-877.
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http://dx.doi.org/10.1089/ars.2015.6616DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5444494PMC
May 2017

Genomic and transcriptomic hallmarks of poorly differentiated and anaplastic thyroid cancers.

J Clin Invest 2016 Mar 15;126(3):1052-66. Epub 2016 Feb 15.

Background: Poorly differentiated thyroid cancer (PDTC) and anaplastic thyroid cancer (ATC) are rare and frequently lethal tumors that so far have not been subjected to comprehensive genetic characterization.

Methods: We performed next-generation sequencing of 341 cancer genes from 117 patient-derived PDTCs and ATCs and analyzed the transcriptome of a representative subset of 37 tumors. Results were analyzed in the context of The Cancer Genome Atlas study (TCGA study) of papillary thyroid cancers (PTC).

Results: Compared to PDTCs, ATCs had a greater mutation burden, including a higher frequency of mutations in TP53, TERT promoter, PI3K/AKT/mTOR pathway effectors, SWI/SNF subunits, and histone methyltransferases. BRAF and RAS were the predominant drivers and dictated distinct tropism for nodal versus distant metastases in PDTC. RAS and BRAF sharply distinguished between PDTCs defined by the Turin (PDTC-Turin) versus MSKCC (PDTC-MSK) criteria, respectively. Mutations of EIF1AX, a component of the translational preinitiation complex, were markedly enriched in PDTCs and ATCs and had a striking pattern of co-occurrence with RAS mutations. While TERT promoter mutations were rare and subclonal in PTCs, they were clonal and highly prevalent in advanced cancers. Application of the TCGA-derived BRAF-RAS score (a measure of MAPK transcriptional output) revealed a preserved relationship with BRAF/RAS mutation in PDTCs, whereas ATCs were BRAF-like irrespective of driver mutation.

Conclusions: These data support a model of tumorigenesis whereby PDTCs and ATCs arise from well-differentiated tumors through the accumulation of key additional genetic abnormalities, many of which have prognostic and possible therapeutic relevance. The widespread genomic disruptions in ATC compared with PDTC underscore their greater virulence and higher mortality.

Funding: This work was supported in part by NIH grants CA50706, CA72597, P50-CA72012, P30-CA008748, and 5T32-CA160001; the Lefkovsky Family Foundation; the Society of Memorial Sloan Kettering; the Byrne fund; and Cycle for Survival.
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http://dx.doi.org/10.1172/JCI85271DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4767360PMC
March 2016

NF2 Loss Promotes Oncogenic RAS-Induced Thyroid Cancers via YAP-Dependent Transactivation of RAS Proteins and Sensitizes Them to MEK Inhibition.

Cancer Discov 2015 Nov 10;5(11):1178-93. Epub 2015 Sep 10.

Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, New York. Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, New York. Cell Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York. Department of Medicine, Weill Cornell Medical College, New York, New York.

Unlabelled: Ch22q LOH is preferentially associated with RAS mutations in papillary and in poorly differentiated thyroid cancer (PDTC). The 22q tumor suppressor NF2, encoding merlin, is implicated in this interaction because of its frequent loss of function in human thyroid cancer cell lines. Nf2 deletion or Hras mutation is insufficient for transformation, whereas their combined disruption leads to murine PDTC with increased MAPK signaling. Merlin loss induces RAS signaling in part through inactivation of Hippo, which activates a YAP-TEAD transcriptional program. We find that the three RAS genes are themselves YAP-TEAD1 transcriptional targets, providing a novel mechanism of promotion of RAS-induced tumorigenesis. Moreover, pharmacologic disruption of YAP-TEAD with verteporfin blocks RAS transcription and signaling and inhibits cell growth. The increased MAPK output generated by NF2 loss in RAS-mutant cancers may inform therapeutic strategies, as it generates greater dependency on the MAPK pathway for viability.

Significance: Intensification of mutant RAS signaling through copy-number imbalances is commonly associated with transformation. We show that NF2/merlin inactivation augments mutant RAS signaling by promoting YAP/TEAD-driven transcription of oncogenic and wild-type RAS, resulting in greater MAPK output and increased sensitivity to MEK inhibitors.
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http://dx.doi.org/10.1158/2159-8290.CD-15-0330DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4642441PMC
November 2015

Switch in signaling control of mTORC1 activity after oncoprotein expression in thyroid cancer cell lines.

J Clin Endocrinol Metab 2014 Oct 16;99(10):E1976-87. Epub 2014 Jul 16.

Human Oncology and Pathogenesis Program (R.M., K.-Y.C., T.-Y.K., J.M.D., F.V., S.K.V., J.A.K., J.A.F.) and Department of Medicine (J.A.K., J.A.F.), Memorial Sloan-Kettering Cancer Center, New York, New York 10065; and Division of Endocrinology (B.O.), University of Cincinnati College of Medicine, Cincinnati, Ohio 45267.

Context: Thyroid growth is regulated by TSH and requires mammalian target of rapamycin (mTOR). Thyroid cancers frequently exhibit mutations in MAPK and/or phosphoinositol-3-kinase-related kinase effectors.

Objective: The objective of the study was to explore the contribution of RET/PTC, RAS, and BRAF to mTOR regulation and response to mTOR inhibitors.

Methods: PCCL3 cells conditionally expressing RET/PTC3, HRAS(G12V), or BRAF(V600E) and human thyroid cancer cells harboring mutations of these genes were used to test pathways controlling mTOR and its requirement for growth.

Results: TSH/cAMP-induced growth of PCCL3 cells requires mTOR, which is stimulated via protein kinase A in a MAPK kinase (MEK)- and AKT-independent manner. Expression of RET/PTC3, HRAS(G12V), or BRAF(V600E) in PCCL3 cells induces mTOR but does not entirely abrogate the cAMP-mediated control of its activity. Acute oncoprotein-induced mTOR activity is regulated by MEK and AKT, albeit to differing degrees. By contrast, mTOR was not activated by TSH/cAMP in human thyroid cancer cells. Tumor genotype did not predict the effects of rapamycin or the mTOR kinase inhibitor AZD8055 on growth, with the exception of a PTEN-null cell line. Selective blockade of MEK did not influence mTOR activity of BRAF or RAS mutant cells. Combined MEK and mTOR kinase inhibition was synergistic on growth of BRAF- and RAS-mutant thyroid cancer cells in vitro and in vivo.

Conclusion: Thyroid cancer cells lose TSH/cAMP dependency of mTOR signaling and cell growth. mTOR activity is not decreased by the MEK or AKT inhibitors in the RAS or BRAF human thyroid cancer cell lines. This may account for the augmented effects of combining the mTOR inhibitors with selective antagonists of these oncogenic drivers.
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http://dx.doi.org/10.1210/jc.2013-3976DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4184069PMC
October 2014

Identification of kinase fusion oncogenes in post-Chernobyl radiation-induced thyroid cancers.

J Clin Invest 2013 Nov 25;123(11):4935-44. Epub 2013 Oct 25.

Exposure to ionizing radiation during childhood markedly increases the risk of developing papillary thyroid cancer. We examined tissues from 26 Ukrainian patients with thyroid cancer who were younger than 10 years of age and living in contaminated areas during the time of the Chernobyl nuclear reactor accident. We identified nonoverlapping somatic driver mutations in all 26 cases through candidate gene assays and next-generation RNA sequencing. We found that 22 tumors harbored fusion oncogenes that arose primarily through intrachromosomal rearrangements. Altogether, 23 of the oncogenic drivers identified in this cohort aberrantly activate MAPK signaling, including the 2 somatic rearrangements resulting in fusion of transcription factor ETS variant 6 (ETV6) with neurotrophic tyrosine kinase receptor, type 3 (NTRK3) and fusion of acylglycerol kinase (AGK) with BRAF. Two other tumors harbored distinct fusions leading to overexpression of the nuclear receptor PPARγ. Fusion oncogenes were less prevalent in tumors from a cohort of children with pediatric thyroid cancers that had not been exposed to radiation but were from the same geographical regions. Radiation-induced thyroid cancers provide a paradigm of tumorigenesis driven by fusion oncogenes that activate MAPK signaling or, less frequently, a PPARγ-driven transcriptional program.
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http://dx.doi.org/10.1172/JCI69766DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3809792PMC
November 2013

Targeting mTOR in RET mutant medullary and differentiated thyroid cancer cells.

Endocr Relat Cancer 2013 Oct 21;20(5):659-67. Epub 2013 Aug 21.

Human Oncology and Pathogenesis Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA.

Inhibitors of RET, a tyrosine kinase receptor encoded by a gene that is frequently mutated in medullary thyroid cancer, have emerged as promising novel therapies for the disease. Rapalogs and other mammalian target of rapamycin (mTOR) inhibitors are effective agents in patients with gastroenteropancreatic neuroendocrine tumors, which share lineage properties with medullary thyroid carcinomas. The objective of this study was to investigate the contribution of mTOR activity to RET-induced signaling and cell growth and to establish whether growth suppression is enhanced by co-targeting RET and mTOR kinase activities. Treatment of the RET mutant cell lines TT, TPC-1, and MZ-CRC-1 with AST487, a RET kinase inhibitor, suppressed growth and showed profound and sustained inhibition of mTOR signaling, which was recapitulated by siRNA-mediated RET knockdown. Inhibition of mTOR with INK128, a dual mTORC1 and mTORC2 kinase inhibitor, also resulted in marked growth suppression to levels similar to those seen with RET blockade. Moreover, combined treatment with AST487 and INK128 at low concentrations suppressed growth and induced apoptosis. These data establish mTOR as a key mediator of RET-mediated cell growth in thyroid cancer cells and provide a rationale for combinatorial treatments in thyroid cancers with oncogenic RET mutations.
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http://dx.doi.org/10.1530/ERC-13-0085DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4375728PMC
October 2013

Relief of feedback inhibition of HER3 transcription by RAF and MEK inhibitors attenuates their antitumor effects in BRAF-mutant thyroid carcinomas.

Cancer Discov 2013 May 29;3(5):520-33. Epub 2013 Jan 29.

Human Oncology and Pathogenesis Program, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.

The RAF inhibitor vemurafenib (PLX4032) increases survival in patients with BRAF-mutant metastatic melanoma, but has limited efficacy in patients with colorectal cancers. Thyroid cancer cells are also comparatively refractory to RAF inhibitors. In contrast to melanomas, inhibition of mitogen-activated protein kinase (MAPK) signaling by PLX4032 is transient in thyroid and colorectal cancer cells. The rebound in extracellular signal-regulated kinase (ERK) in thyroid cells is accompanied by increased HER3 signaling caused by induction of ERBB3 (HER3) transcription through decreased promoter occupancy by the transcriptional repressors C-terminal binding protein 1 and 2 and by autocrine secretion of neuregulin-1 (NRG1). The HER kinase inhibitor lapatinib prevents MAPK rebound and sensitizes BRAF-mutant thyroid cancer cells to RAF or MAP-ERK kinase inhibitors. This provides a rationale for combining ERK pathway antagonists with inhibitors of feedback-reactivated HER signaling in this disease. The determinants of primary resistance to MAPK inhibitors vary between cancer types, due to preferential upregulation of specific receptor tyrosine kinases, and the abundance of their respective ligands.
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http://dx.doi.org/10.1158/2159-8290.CD-12-0531DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3651738PMC
May 2013

STAT3 negatively regulates thyroid tumorigenesis.

Proc Natl Acad Sci U S A 2012 Aug 13;109(35):E2361-70. Epub 2012 Aug 13.

Department of Cancer Biology, Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), 4200-465 Porto, Portugal.

Although tyrosine-phosphorylated or activated STAT3 (pY-STAT3) is a well-described mediator of tumorigenesis, its role in thyroid cancer has not been investigated. We observed that 63 of 110 (57%) human primary papillary thyroid carcinoma (PTC) cases expressed nuclear pY-STAT3 in tumor cells, preferentially in association with the tumor stroma. An inverse relationship between pY-STAT3 expression with tumor size and the presence of distant metastases was observed. Using human thyroid cancer-derived cell lines [harboring rearranged during transfection (RET)/PTC, v-RAF murine sarcoma viral oncogene homolog B (BRAF), or rat sarcoma virus oncogene (RAS) alterations], we determined that IL-6/gp130/JAK signaling is responsible for STAT3 activation. STAT3 knockdown by shRNA in representative thyroid cancer cell lines that express high levels of pY-STAT3 had no effect on in vitro growth. However, xenografted short hairpin STAT3 cells generated larger tumors than control cells. Similarly, STAT3 deficiency in a murine model of BRAFV600E-induced PTC led to thyroid tumors that were more proliferative and larger than those tumors expressing STAT3wt. Genome expression analysis revealed that STAT3 knockdown resulted in the down-regulation of multiple transcripts, including the tumor suppressor insulin-like growth factor binding protein 7. Furthermore, STAT3 knockdown led to an increase in glucose consumption, lactate production, and expression of Hypoxia-inducible factor 1 (HIF1α) target genes, suggesting that STAT3 is a negative regulator of aerobic glycolysis. Our studies show that, in the context of thyroid cancer, STAT3 is paradoxically a negative regulator of tumor growth. These findings suggest that targeting STAT3 in these cancers could enhance tumor size and highlight the complexities of the role of STAT3 in tumorigenesis.
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http://dx.doi.org/10.1073/pnas.1201232109DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3435219PMC
August 2012

GLP-1 receptor agonists and the thyroid: C-cell effects in mice are mediated via the GLP-1 receptor and not associated with RET activation.

Endocrinology 2012 Mar 10;153(3):1538-47. Epub 2012 Jan 10.

Novo Nordisk A/S, Novo Allé, DK-2880, Bagsvaerd, Denmark.

Liraglutide and exenatide are glucagon-like peptide receptor (GLP-1R) agonists used in the treatment of type 2 diabetes. Both molecules have been associated with the development of thyroid C-cell tumors after lifetime exposure in rodents. Previously, it has been reported that these tumors are preceded by increased plasma calcitonin and C-cell hyperplasia. We can now document that the murine C-cell effects are mediated via GLP-1R. Thus, 13 wk of continuous exposure to GLP-1R agonists was associated with marked increases in plasma calcitonin and in the incidence of C-cell hyperplasia in wild-type mice. In contrast, similar effects were not seen in GLP-1R knockout mice. Human C-cell cancer is often caused by activating mutations in the rearranged-during-transfection (RET) protooncogene. We developed an immunohistochemical method to assess RET activation in tissues. Liraglutide dosing to mice was not found to activate RET. Further evaluation of the signaling pathways demonstrated that liraglutide increased ribosomal S6, but not MAPK kinase, phosphorylation. These observations are consistent with effects of GLP-1R agonists on rodent C cells being mediated via mammalian target of rapamycin activation in a RET- and MAPK-independent manner.
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http://dx.doi.org/10.1210/en.2011-1864DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3281535PMC
March 2012

Small-molecule MAPK inhibitors restore radioiodine incorporation in mouse thyroid cancers with conditional BRAF activation.

J Clin Invest 2011 Dec 21;121(12):4700-11. Epub 2011 Nov 21.

Human Oncology and Pathogenesis Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA.

Advanced human thyroid cancers, particularly those that are refractory to treatment with radioiodine (RAI), have a high prevalence of BRAF (v-raf murine sarcoma viral oncogene homolog B1) mutations. However, the degree to which these cancers are dependent on BRAF expression is still unclear. To address this question, we generated mice expressing one of the most commonly detected BRAF mutations in human papillary thyroid carcinomas (BRAF(V600E)) in thyroid follicular cells in a doxycycline-inducible (dox-inducible) manner. Upon dox induction of BRAF(V600E), the mice developed highly penetrant and poorly differentiated thyroid tumors. Discontinuation of dox extinguished BRAF(V600E) expression and reestablished thyroid follicular architecture and normal thyroid histology. Switching on BRAF(V600E) rapidly induced hypothyroidism and virtually abolished thyroid-specific gene expression and RAI incorporation, all of which were restored to near basal levels upon discontinuation of dox. Treatment of mice with these cancers with small molecule inhibitors of either MEK or mutant BRAF reduced their proliferative index and partially restored thyroid-specific gene expression. Strikingly, treatment with the MAPK pathway inhibitors rendered the tumor cells susceptible to a therapeutic dose of RAI. Our data show that thyroid tumors carrying BRAF(V600E) mutations are exquisitely dependent on the oncoprotein for viability and that genetic or pharmacological inhibition of its expression or activity is associated with tumor regression and restoration of RAI uptake in vivo in mice. These findings have potentially significant clinical ramifications.
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http://dx.doi.org/10.1172/JCI46382DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3225989PMC
December 2011

Proto-oncogene PBF/PTTG1IP regulates thyroid cell growth and represses radioiodide treatment.

Cancer Res 2011 Oct 15;71(19):6153-64. Epub 2011 Aug 15.

School of Clinical and Experimental Medicine, Institute of Biomedical Research, University of Birmingham, United Kingdom.

Pituitary tumor transforming gene (PTTG)-binding factor (PBF or PTTG1IP) is a little characterized proto-oncogene that has been implicated in the etiology of breast and thyroid tumors. In this study, we created a murine transgenic model to target PBF expression to the thyroid gland (PBF-Tg mice) and found that these mice exhibited normal thyroid function, but a striking enlargement of the thyroid gland associated with hyperplastic and macrofollicular lesions. Expression of the sodium iodide symporter (NIS), a gene essential to the radioiodine ablation of thyroid hyperplasia, neoplasia, and metastasis, was also potently inhibited in PBF-Tg mice. Critically, iodide uptake was repressed in primary thyroid cultures from PBF-Tg mice, which could be rescued by PBF depletion. PBF-Tg thyroids exhibited upregulation of Akt and the TSH receptor (TSHR), each known regulators of thyrocyte proliferation, along with upregulation of the downstream proliferative marker cyclin D1. We extended and confirmed findings from the mouse model by examining PBF expression in human multinodular goiters (MNG), a hyperproliferative thyroid disorder, where PBF and TSHR was strongly upregulated relative to normal thyroid tissue. Furthermore, we showed that depleting PBF in human primary thyrocytes was sufficient to increase radioiodine uptake. Together, our findings indicate that overexpression of PBF causes thyroid cell proliferation, macrofollicular lesions, and hyperplasia, as well as repression of the critical therapeutic route for radioiodide uptake.
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http://dx.doi.org/10.1158/0008-5472.CAN-11-0720DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3184940PMC
October 2011

Thyrotrophin receptor signaling dependence of Braf-induced thyroid tumor initiation in mice.

Proc Natl Acad Sci U S A 2011 Jan 10;108(4):1615-20. Epub 2011 Jan 10.

Human Oncology and Pathogenesis Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.

Mutations of BRAF are found in ∼45% of papillary thyroid cancers and are enriched in tumors with more aggressive properties. We developed mice with a thyroid-specific knock-in of oncogenic Braf (LSL-Braf(V600E)/TPO-Cre) to explore the role of endogenous expression of this oncoprotein on tumor initiation and progression. In contrast to other Braf-induced mouse models of tumorigenesis (i.e., melanomas and lung), in which knock-in of Braf(V600E) induces mostly benign lesions, Braf-expressing thyrocytes become transformed and progress to invasive carcinomas with a very short latency, a process that is dampened by treatment with an allosteric MEK inhibitor. These mice also become profoundly hypothyroid due to deregulation of genes involved in thyroid hormone biosynthesis and consequently have high TSH levels. To determine whether TSH signaling cooperates with oncogenic Braf in this process, we first crossed LSL-Braf(V600E)/TPO-Cre with TshR knockout mice. Although oncogenic Braf was appropriately activated in thyroid follicular cells of these mice, they had a lower mitotic index and were not transformed. Thyroid-specific deletion of the Gsα gene in LSL-Braf(V600E)/TPO-Cre/Gnas-E1(fl/fl) mice also resulted in an attenuated cancer phenotype, indicating that the cooperation of TshR with oncogenic Braf is mediated in part by cAMP signaling. Once tumors were established in mice with wild-type TshR, suppression of TSH did not revert the phenotype. These data demonstrate the key role of TSH signaling in Braf-induced papillary thyroid cancer initiation and provide experimental support for recent observations in humans pointing to a strong association between TSH levels and thyroid cancer incidence.
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http://dx.doi.org/10.1073/pnas.1015557108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3029699PMC
January 2011

Mutational profile of advanced primary and metastatic radioactive iodine-refractory thyroid cancers reveals distinct pathogenetic roles for BRAF, PIK3CA, and AKT1.

Cancer Res 2009 Jun;69(11):4885-93

Human Oncology and Pathogenesis Program and Departments of Medicine and Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York 10065, USA.

Patients with poorly differentiated thyroid cancers (PDTC), anaplastic thyroid cancers (ATC), and radioactive iodine-refractory (RAIR) differentiated thyroid cancers have a high mortality, particularly if positive on [(18)F]fluorodeoxyglucose (FDG)-positron emission tomography (PET). To obtain comprehensive genetic information on advanced thyroid cancers, we designed an assay panel for mass spectrometry genotyping encompassing the most significant oncogenes in this disease: 111 mutations in RET, BRAF, NRAS, HRAS, KRAS, PIK3CA, AKT1, and other related genes were surveyed in 31 cell lines, 52 primary tumors (34 PDTC and 18 ATC), and 55 RAIR, FDG-PET-positive recurrences and metastases (nodal and distant) from 42 patients. RAS mutations were more prevalent than BRAF (44 versus 12%; P = 0.002) in primary PDTC, whereas BRAF was more common than RAS (39 versus 13%; P = 0.04) in PET-positive metastatic PDTC. BRAF mutations were highly prevalent in ATC (44%) and in metastatic tumors from RAIR PTC patients (95%). Among patients with multiple metastases, 9 of 10 showed between-sample concordance for BRAF or RAS mutations. By contrast, 5 of 6 patients were discordant for mutations of PIK3CA or AKT1. AKT1_G49A was found in 9 specimens, exclusively in metastases. This is the first documentation of AKT1 mutation in thyroid cancer. Thus, RAIR, FDG-PET-positive metastases are enriched for BRAF mutations. If BRAF is mutated in the primary, it is likely that the metastases will harbor the defect. By contrast, absence of PIK3CA/AKT1 mutations in one specimen may not reflect the status at other sites because these mutations arise during progression, an important consideration for therapies directed at phosphoinositide 3-kinase effectors.
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http://dx.doi.org/10.1158/0008-5472.CAN-09-0727DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2690720PMC
June 2009

Endogenous expression of Hras(G12V) induces developmental defects and neoplasms with copy number imbalances of the oncogene.

Proc Natl Acad Sci U S A 2009 May 29;106(19):7979-84. Epub 2009 Apr 29.

Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.

We developed mice with germline endogenous expression of oncogenic Hras to study effects on development and mechanisms of tumor initiation. They had high perinatal mortality, abnormal cranial dimensions, defective dental ameloblasts, and nasal septal deviation, consistent with some of the features of human Costello syndrome. These mice developed papillomas and angiosarcomas, which were associated with Hras(G12V) allelic imbalance and augmented Hras signaling. Endogenous expression of Hras(G12V) was also associated with a higher mutation rate in vivo. Tumor initiation by Hras(G12V) likely requires augmentation of signal output, which in papillomas and angiosarcomas is achieved via increased Hras-gene copy number, which may be favored by a higher mutation frequency in cells expressing the oncoprotein.
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http://dx.doi.org/10.1073/pnas.0900343106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2674938PMC
May 2009

Role of MAPK pathway oncoproteins in thyroid cancer pathogenesis and as drug targets.

Curr Opin Cell Biol 2009 Apr 21;21(2):296-303. Epub 2009 Feb 21.

Department of Medicine and Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.

Constitutive activation of MAPK in cancer occurs through activating mutations or overexpression of upstream effectors in the pathway, primarily of genes encoding receptor tyrosine kinases, RAS and BRAF. Arguably, the evidence for MAPK activation is most compelling in thyroid cancers and in melanomas. In this review we discuss the mechanisms of tumor development by oncogenic BRAF in these two cancer cell lineages, since this kinase signals preferentially through this pathway. We describe recent information on the mediators of BRAF-induced tumor initiation and escape from senescence. In addition, we review the biochemical events implicated in cellular growth triggered by oncogenic BRAF and the determinants of oncogene addiction. The biology of thyroid cancers induced by oncogenic BRAF is quite distinct, both in humans and in mice. There is great interest in using these insights to design rational new therapies, for which it will become crucial to understand the determinants of sensitivity and resistance to compounds designed to block the pathway. In thyroid cancer, this interest is further heightened by new information on the role of activated BRAF and MAPK pathway activation in disrupting iodine transport and thyroid hormonogenesis.
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http://dx.doi.org/10.1016/j.ceb.2009.01.013DOI Listing
April 2009