BRIEF REPORT KCNQ1OT1 Hypomethylation: A Novel Disguised Genetic Predisposition in Sporadic Pediatric Adrenocortical Tumors?
Mark Wijnen,1 Marielle Alders, MD, PHD,2 Christian M. Zwaan, MD, PHD,1 Anja Wagner, MD, PHD,3 and Marry M. van den Heuvel-Eibrink, MD, PhD1*
Pediatric adrenal tumors, other than neuroblastoma, are rare and can be associated with a genetic predisposition. In this report we describe two patients with an isolated and apparently sporadic adrenocortical tumor; one girl with a carcinoma, the other girl with an adenoma. In both patients genetic screening revealed hypomethylation of the KCNQ1OT1 gene, well-known
for its association with the Beckwith-Wiedemann syndrome. This represents a likely novel genetic predisposition in patients with adrenocortical tumors without clear phenotypic features of the Beckwith-Wiedemann syndrome. Pediatr Blood Cancer @ 2011 Wiley Periodicals, Inc.
Key words: adrenocortical tumors; Beckwith-Wiedemann syndrome; genetics; pediatric oncology
INTRODUCTION
Aberrant epigenetic regulation, that is, changes in gene tran- scription not due to alterations in DNA sequence, is increasingly recognized as a cause of adult and pediatric tumor development. Epigenetic regulation occurs by DNA-methylation, histone mod- ifications, microRNAs and other, less well-known, epigenetic mechanisms [1]. Some congenital disorders with aberrant epige- netic regulation, like the Beckwith-Wiedemann syndrome, are known to increase the susceptibility for certain childhood tumors.
Beckwith-Wiedemann syndrome is an overgrowth syndrome with an estimated incidence of 1 in 13,700. Affected individuals are at increased risk to develop embryonal tumors like Wilms tumor and hepatoblastoma, predominantly in the first 8-10 years of life. Consequently, tumor surveillance protocols that include abdominal imaging and alpha-fetoprotein (AFP) serum level screening have been developed [2]. A recent study by Scott et al. [3] reported that underlying genetic predispositions of the Beckwith-Wiedemann syndrome involving the H19 gene, might cause Wilms tumor in patients without clear phenotypic features of the overt syndrome. In the current report, we show that another underlying genetic predisposition of the Beckwith-Wiedemann syndrome, that is, hypomethylation of the KCNQ1OT1 gene, contributes to the occurrence of adrenocortical carcinoma and adenoma in patients without clear phenotypic features of the Beckwith-Wiedemann syndrome.
CASE REPORT
Case 1
A 9-year-old female was referred to our pediatric oncology department with Cushing syndrome, virilization, and hyperten- sion. Diagnostic work-up revealed a cortisol-, androgen-, and estradiol-secreting stage IV carcinoma of the left adrenal cortex. Family history was negative for malignancies. She was treated with primary tumor resection and subsequent treatment with cisplatin, etoposide, doxorubicin, and mitotane which resulted in complete response. Unfortunately, 2 years later she relapsed and died. Genetic screening excluded a TP53 gene mutation, but revealed hypomethylation of the KCNQ1OT1 (synonymous with LIT1) gene, which was more pronounced in tumor tissue than in germline material (Fig. 1A), indicating that KCNQ1OT1
hypomethylation contributed to tumorigenesis. The H19 gene methylation was normal, that is, unmethylated on the maternal and methylated on the paternal chromosome. Except for a rather high birth weight (+1.5 SD) and a port-wine stain (1 cm x 2 cm) on the upper lip, which faded with age, no features of the Beckwith-Wiedemann syndrome were found.
Case 2
A 14-year-old female was referred to our department because of virilization and secondary amenorrhea. Diagnostic testing revealed a dehydroepianosterone sulfate (DHEAS) and testoster- one producing adenoma of the left adrenal cortex, which was surgically removed. Family history was negative for malignan- cies. Genetic screening excluded a MEN1 gene mutation. However, KCNQ1OT1 hypomethylation was found, which was more pro- nounced in tumor tissue than in germline material (Fig. 1B). Methylation of the H19 gene was normal. No phenotypic features of the Beckwith-Wiedemann syndrome were present.
DISCUSSION
Pediatric adrenal tumors, other than neuroblastoma, are rare and can be associated with a genetic predisposition. Pheochromo- cytomas are associated with multiple endocrine neoplasia syn- dromes, von Hippel-Lindau syndrome, familial paraganglioma, and neurofibromatosis type 1 [4]. Most adrenocortical carcinomas
1Department of Pediatric Oncology/Hematology, Erasmus MC- Sophia Children’s Hospital, Rotterdam, the Netherlands; 2Clinical Genetics, Academic Medical Center, Amsterdam, the Netherlands;
3Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, the Netherlands
Conflict of interest: Nothing to declare.
Anja Wagner and Marry M. van den Heuvel-Eibrink contributed equally to this work.
*Correspondence to: Marry M. van den Heuvel-Eibrink, MD, PHD, Associate Professor, Department of Pediatric Oncology/Hematology, Erasmus MC-Sophia Children’s Hospital, Dr. Molewaterplein 60, 3015 GJ Rotterdam, the Netherlands.
E-mail: m.vandenheuvel@erasmusmc.nl
Received 21 August 2011; Accepted 23 September 2011
@ 2011 Wiley Periodicals, Inc.
DOI 10.1002/pbc.23398
A
Shifted Melting Curves
1
Temperature Normalized Fluorescence
08
0.6
N
0.4
P1
Blood
P2
02
P3
P4
Tumor
0
81
82
83
84
85
86
87
88
89
90
Temperature ℃
B
Shifted Melting Curves
1
Temperature Normalized Fluorescence
0.8
0.6
N
04
P1
Normal Tissue
P2
0.2
P3
Tumor
P4
0
78
79
80
61
82
83
84
85
86
87
Temperature ”℃
are associated with Li-Fraumeni syndrome and both adrenocorti- cal adenomas and carcinomas can occur within the context of multiple endocrine neoplasia type 1 and Beckwith-Wiedemann syndrome [5].
Beckwith-Wiedemann syndrome is a congenital tumor- predisposition syndrome with variable clinical features. The most characteristic features are macrosomia, macroglossia, and omphalocele. Affected subjects carry an increased tumor risk which depends on the underlying molecular abnormality. The most frequently observed tumors include Wilms tumor and hepatoblastoma, but also other tumors like rhabdomyosarcoma, adrenocortical tumors and neuroblastoma are reported. Beckwith-
Wiedemann syndrome is associated with alterations of imprinted genes at chromosome 11p15, that is, the KCNQ1OT1, KCNQ1, CDKN1C, H19, and IGF2 genes. Chromosome 11p15 harbors two imprinting centers (IC): IC1 and IC2. IC1 controls the imprinted expression of, amongst others, the paternally expressed IGF2 gene and the maternally expressed H19 gene. IC2 controls the paternally expressed KCNQ1OT1 gene and the maternally expressed KCNQ1 and CDKN1C genes, of which the latter enc- odes the tumor suppressor p57KIP2. KCNQ1OT1 is an untranslated transcript regulating the expression of other genes in IC2; hypo- methylation results in reduced CDKN1C expression. KCNQ1OT1 hypomethylation is the most common underlying genetic aberra- tion in the Beckwith-Wiedemann syndrome, accounting for 50% of the sporadic cases [2], and always occurs as mosaicism [6]. Patients with KCNQ1OT1 hypomethylation have a lower tumor risk than patients with Beckwith-Wiedemann syndrome caused by other molecular abnormalities like H19 hypermethylation (5% vs. >25%), and exhibit predominantly non-nephroblastoma tumors [2,7,8]. Up until now, all reported hypomethylated KCNQ1OT1 adrenocortical tumor patients presented with the typical Beckwith-Wiedemann syndrome features.
Our cases illustrate the variable phenotype of KCNQ1OT1 hypomethylation, which may be correlated with the distribution and degree of hypomethylation. One can speculate that the degree of KCNQ1OT1 hypomethylation in a certain tissue is not only relevant for the variability of Beckwith-Wiedemann syndrome features, but is also correlated with the risk to develop a malig- nancy. In several tumors, hypomethylation shows a progressive increase with the grade of malignancy [9]. In addition, also modi- fier genes and environmental factors may influence the resulting phenotype of a genetic predisposition.
We feel that KCNQ1OT1 hypomethylation should not only be considered in cases with a clear Beckwith-Wiedemann syndrome phenotype but in all cases of apparently sporadic and isolated adrenocortical adenoma and carcinoma, as identifying a genetic predisposition in sporadic childhood tumors is very important for counseling and pre-emptive cancer screening. Future studies in cohorts of adrenocortical adenomas and carcinomas are needed to gain insight in the actual prevalence of this genetic predisposition in isolated childhood adrenocortical tumors.
REFERENCES
1. Fruhwald MC, Witt O. The epigenetics of cancer in children. Klin Padiatr 2008;220:333-341.
2. Weksberg R, Shuman C, Beckwith JB. Beckwith-Wiedemann syndrome. Eur J Hum Genet 2010;18: 8-14.
3. Scott RH, Douglas J, Baskcomb L, et al. Constitutional 11p15 abnormalities, including heritable imprinting center mutations, cause nonsyndromic wilms tumor. Nat Genet 2008;40:1329-1334.
4. McHugh K. Renal and adrenal tumours in children. Cancer Imaging 2007;7:41-51.
5. Ribeiro RC, Figueiredo B. Childhood adrenocortical tumours. Eur J Cancer 2004;40:1117-1126.
6. Alders M, Bliek J, vd Lip K, et al. Determination of KCNQ1OT1 and H19 methylation levels in bws and srs patients using methylation-sensitive high-resolution melting analysis. Eur J Hum Genet 2009;17:467-473.
7. Bliek J, Gicquel C, Maas S, et al. Epigenotyping as a tool for the prediction of tumor risk and tumor type in patients with Beckwith-Wiedemann syndrome (bws). J Pediatr 2004;145:796-799.
8. Alsultan A, Lovell MA, Hayes KL, et al. Simultaneous occurrence of right adrenocortical tumor and left adrenal neuroblastoma in an infant with Beckwith-Wiedemann syndrome. Pediatr Blood Cancer 2008;51:695-698.
9. Ehrlich M. DNA methylation in cancer: Too much, but also too little. Oncogene 2002;21:5400-5413.