Recurrent ZFX mutations in human sporadic parathyroid adenomas

Abstract

ABSTRACT:The molecular abnormalities leading to sporadic parathyroid adenomas, a common type of human endocrine neoplasm, are heterogeneous and incompletely understood. Using whole exome and direct sequencing of parathyroid adenoma DNA samples, we identified recurrent somatic mutations in the ZFX gene. ZFX is a member of Krueppel C2H2 type zinc finger protein family, was initially described as a homolog of ZFY, and has been implicated as a transcription factor regulating embryonic stem cell renewal. The ZFX mutations we identified were strikingly specific, focused in each tumor on one encoded residue in a hotspot of two consecutive highly conserved arginine residues (R786/787; arginine to glutamine, threonine or leucine) in a zinc finger domain near the C-terminus of the protein. The intragenic specificity of these recurrently selected mutations, their confirmed expression within the tumors, the absence of loss of heterozygosity, and the absence of these mutations among over 4000 ZFX alleles in the dbSNP137 database, strongly suggest a novel role for ZFX as a human proto-oncogene. Further, these observations highlight the mutated zincfinger domain as a new focal point for understanding ZFX's normal and tumorigenic functions, and for development of molecularly-targeted therapeutics.

PIK3CA Mutational Analysis of Parathyroid Adenomas

“…First, in sequencing chromatograms, the relative heights of the mutant peaks were much lower than that of the WT peak at that position. In contrast, despite the semiquantitative nature of Sanger methodology, in our experience sequencing parathyroid adenomas the observed peak height ratio for heterozygous variants is typically very close to 1:1, reflecting the exceedingly high tumor cell purity characteristic of parathyroid adenomas. Next, the proportion of mutation‐containing clones (15.4% to 28.6%) obtained by sequencing of subcloned PCR products was consistent with the relative peak heights observed in Sanger sequencing of the original tumor sample.…”

“…Because of histologic similarities, it can be difficult to distinguish parathyroid carcinoma from its malignant counterpart, and a diagnosis of carcinoma can only be made when there is clear evidence of invasive growth into adjacent structures and/or distant metastasis . The MEN1 tumor suppressor gene and the CCND1 oncogene (encoding cyclin D1) are well‐established drivers of parathyroid adenoma and lower frequency mutations have been described in other candidate driver genes, such as EZH2 , ZFX , and several cyclin‐dependent kinase inhibitors in parathyroid adenomas . The CDC73/HRPT2 tumor suppressor gene is the most frequently altered driver gene in parathyroid carcinoma; amplifications of CCND1 have also been observed .…”

Molecular genetics in primary hyperparathyroidism: the role of genetic tests in differential diagnosis, disease prevention strategy, and therapeutic planning. A 2017 update

“…In two of 132 tumours has been identified the R304Q germline mutation, and heterozygous AIP locus large deletions have been detected in 29 cases, including one of the two mutated adenomas. Sanger DNA sequencing on large cohorts of sporadic parathyroid adenomas or whole exome next generation sequencing analysis identified low-frequency germline and somatic mutations of other and novel genes, such as inactivating mutations in the CDKI genes (i.e two CDKN1B mutations in a total of 86 cases) (36), stabilizing mutations of the beta catenin (CTNNB1) gene (37)(38)(39), an activating mutation (Y641N) in the histone 3 lysine 27 methyltransferase (EZH2) gene (found in two of 193 analysed adenomas) (40), and somatic mutations (at codons 786 and 787) in the zinc finger Xlinked (ZFX) gene (41). However, a recent work on an Italian cohort of 12 atypical parathyroid adenomas, 45 typical parathyroid adenomas and 23 sporadic parathyroid carcinomas failed to confirm these results and to detect any mutation of EZH2 and ZFX genes (42).…”

New role for ZFX in oncogenesis

“…5 Starting with a cohort of parathyroid adenomas subjected to whole exome sequencing, ZFX mutations were identified in nearly 5% of tumors (6/130), one of the more fruitful outcomes of unbiased sequencing approaches in this disease. ZFX, best known for its role in regulating stem cell renewal and differentiation, belongs to the Krueppel C2H2-type zinc finger protein family and contains 13 zinc finger subdomains.…”

“…Furthermore, the narrow spectrum of affected codons, and the presence in females of heterozygous mutation of this X-linked but non-X-inactivated gene, suggests that mutant ZFX is functioning as a direct-acting dominant oncogene, conferring a gain-of-function which might involve accentuation of normal transcriptional activities or a qualitative change in target genes. 5 Regarding these questions of how ZFX mutation may drive neoplasia, other intriguing links between ZFX and tumorigenesis have been reported. In addition to its required role in self-renewal of haematopoietic and embryonic stem cells, ZFX contributes to MYC or NOTCH-induced leukemia induction in mice, and ZFX was also identified as a crucial regulator of specific Hedgehog-induced malignancies in vivo.…”