Anaplastic thyroid carcinoma (ATC) is a frequently lethal malignancy that is often unresponsive to available therapeutic strategies. The tumorigenesis of ATC and its relationship to the widely prevalent well-differentiated thyroid carcinomas are unclear. We have analyzed 22 cases of ATC as well as 4 established ATC cell lines using whole-exome sequencing. A total of 2674 somatic mutations (121/sample) were detected. Ontology analysis revealed that the majority of variants aggregated in the MAPK, ErbB and RAS signaling pathways. Mutations in genes related to malignancy not previously associated with thyroid tumorigenesis were observed, including mTOR, NF1, NF2, MLH1, MLH3, MSH5, MSH6, ERBB2, EIF1AX and USH2A; some of which were recurrent and were investigated in 24 additional ATC cases and 8 ATC cell lines. Somatic mutations in established thyroid cancer genes were detected in 14 of 22 (64%) tumors and included recurrent mutations in BRAF, TP53 and RAS-family genes (6 cases each), as well as PIK3CA (2 cases) and single cases of CDKN1B, CDKN2C, CTNNB1 and RET mutations. BRAF V600E and RAS mutations were mutually exclusive; all ATC cell lines exhibited a combination of mutations in either BRAF and TP53 or NRAS and TP53. A hypermutator phenotype in two cases with >8 times higher mutational burden than the remaining mean was identified; both cases harbored unique somatic mutations in MLH mismatch-repair genes. This first comprehensive exome-wide analysis of the mutational landscape of ATC identifies novel genes potentially associated with ATC tumorigenesis, some of which may be targets for future therapeutic intervention.
Adrenal tumors autonomously producing cortisol cause Cushing syndrome1–4. Exome sequencing of 25 tumor-normal pairs revealed two groups. Eight tumors (including 3 carcinomas) had many somatic copy number variants (CNV+) with frequent deletion of CDC42 and CDKN2A, amplification of 5q31.2, and protein-altering mutations in TP53 and RB1. Seventeen (all adenomas) had no CNVs (CNV-), TP53 or RB1 mutations. Six of these had known gain of function mutations in CTNNB15,6 (beta-catenin) or GNAS7,8 (Gαs), Six others had somatic p.Leu206Arg mutations in PRKACA (protein kinase A (PKA) catalytic subunit). Further sequencing identified this mutation in 13 of 63 tumors (35% of adenomas with overt CS). PRKACA, GNAS and CTNNB1 mutations were mutually exclusive. Leu206 directly interacts with PKA’s regulatory subunit, PRKAR1A9,10. PRKACAL206R loses PRKAR1A binding, increasing phosphorylation of downstream targets. PKA activity induces cortisol production and cell proliferation11–15, providing a mechanism for tumor development. These findings define distinct mechanisms underlying adrenal cortisol-producing tumors.
These findings highlight the importance of Wnt pathway dysregulation in ACC and corroborate the finding of homozygous deletion of Wnt repressors ZNRF3 and KREMEN1. Overall, mutations in either TP53 or CTNNB1 as well as focal CNAs at the ZNRF3 or TERT loci denote mutually exclusive events, suggesting separate mechanisms underlying the development of these tumors.
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Summary
Aldosterone-producing adenomas (APAs) and bilateral adrenal hyperplasia are important causes of secondary hypertension. Somatic mutations in KCNJ5, CACNA1D, ATP1A1, ATP2B3 and CTNNB1 have been described in APAs.
Objective
To characterize clinical-pathological features in APAs and unilateral adrenal hyperplasia, and correlate them with genotypes.
Design
Retrospective study.
Subjects and Measurements
Clinical and pathological characteristics of 90 APAs and 7 diffusely or focally hyperplastic adrenal glands were reviewed, and samples were examined for mutations in known disease genes by Sanger or exome sequencing.
Results
Mutation frequencies were: KCNJ5, 37.1%; CACNA1D, 10.3%; ATP1A1, 8.2%; ATP2B3, 3.1%; CTNNB1, 2.1%. Previously unidentified mutations included I157K, F154C and 2 insertions (I150_G151insM and I144_E145insAI) in KCNJ5, all close to the selectivity filter, V426G_V427Q_A428_L433del in ATP2B3, and A39Efs*3 in CTNNB1. Mutations in KCNJ5 were associated with female, and other mutations with male gender (p=0.007). On computed tomography, KCNJ5-mutant tumors displayed significantly greater diameter (p=0.023), calculated area (p=0.002) and lower pre-contrast Hounsfield Units (p=0.0002) vs. tumors with mutations in other genes. Accordingly, KCNJ5-mutant tumors were predominantly comprised of lipid-rich fasciculata-like clear cells, whereas other tumors were heterogeneous (p=5×10−6 vs. non-KCNJ5 mutant and p=0.0003 vs. wild type tumors, respectively). CACNA1D mutations were present in two samples with hyperplasia without adenoma.
Conclusions
KCNJ5 mutant tumors appear to be associated with fasciculata-like clear cell predominant histology and tend to be larger with a characteristic imaging phenotype. Novel somatic KCNJ5 variants likely cause adenomas by loss of potassium selectivity, similar to previously described mutations.
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