Beckwith-Wiedemann syndrome: growth pattern and tumor risk according to molecular mechanism, and guidelines for tumor surveillance.

BACKGROUND: Beckwith-Wiedemann syndrome (BWS) is an overgrowth syndrome associated with an increased risk of pediatric tumors. The underlying molecular abnormalities may be genetic (CDKN1C mutations or 11p15 paternal uniparental isodisomy, pUPD) or epigenetic (imprinting center region 1, ICR1, gain of methylation, ICR1 GOM, or ICR2 loss of methylation, ICR2 LOM). AIM: We aimed to describe a cohort of 407 BWS patients with molecular defects of the 11p15 domain followed prospectively after molecular diagnosis. RESULTS: Birth weight and length were significantly higher in patients with ICR1 GOM than in the other groups. ICR2 LOM and CDKN1C mutations were associated with a higher prevalence of exomphalos. Mean adult height (regardless of molecular subtype, n = 35) was 1.8 ± 1.2 SDS, with 18 patients having a final height above +2 SDS. The prevalence of tumors was 8.6% in the whole population; 28.6 and 17.3% of the patients with ICR1 GOM (all Wilms tumors) and 11p15 pUPD, respectively, developed a tumor during infancy. Conversely, the prevalence of tumors in patients with ICR2 LOM and CDKN1C mutations were 3.1 and 8.8%, respectively, with no Wilms tumors. CONCLUSION: Based on these results for a large cohort, we formulated guidelines for the follow-up of these patients according to the molecular subtype of BWS.

Epigenetic and genetic disturbance of the imprinted 11p15 region in Beckwith-Wiedemann and Silver-Russell syndromes.

Genomic imprinting is a particularly attractive example of epigenetic regulation leading to the parental-origin-specific expression of genes. In several ways, the 11p15 imprinted region is an exemplary model for regulation of genomic imprinting. The two imprinted domains are controlled by imprinting control regions (ICRs) which carry opposite germ line imprints and they are regulated by two major mechanisms of imprinting control. Dysregulation of 11p15 genomic imprinting results in two fetal growth disorders [Silver-Russell (SRS) and Beckwith-Wiedemann (BWS) syndromes], with opposite growth phenotypes. BWS and SRS result from abnormal imprinting involving either, both domains or only one of them, with ICR1 and ICR2 more often involved in SRS and BWS respectively. DNA methylation defects affecting ICR1 or ICR2 account for approximately 60% of SRS and BWS patients. Recent studies have identified new cis-acting regulatory elements, as well as new trans-acting factors involved in the regulation of 11p15 imprinting, therefore establishing new mechanisms of BWS and SRS. Those studies also showed that, apart of CTCF, other transcription factors, including factors of the pluripotency network, play a crucial role in the regulation of 11p15 genomic imprinting. Those new findings have direct consequences in molecular testing, risk assessment and genetic counseling of BWS and SRS patients.

Epigenetic and genetic mechanisms of abnormal 11p15 genomic imprinting in Silver-Russell and Beckwith-Wiedemann syndromes.

Fetal growth is a complex process depending on the genetics of the fetus, the availability of nutrients to the fetus, maternal nutrition and various growth factors and hormones of maternal, fetal and placental origin. The IGF system, and more particularly IGF2, is one of the most important endocrine and paracrine growth systems regulating fetal and placental growth (reviewed in [1]). The IGF2 gene is regulated by genomic imprinting and is expressed only from the paternally-inherited allele in most tissues during fetal development and after birth. Imprinted genes are tightly regulated and are therefore particularly susceptible to changes, including environmental and nutritional changes. Dysregulation of a cluster of imprinted genes, including the IGF2 gene within the 11p15 region, results in two fetal growth disorders (Silver-Russell and Beckwith-Wiedemann syndromes) with opposite growth phenotypes. Those two syndromes are model imprinting disorders to decipher the regulation of genomic imprinting.

Epigenetics, genomic imprinting and assisted reproductive technology.

Epigenetic mechanisms play a key role in regulating gene expression. One hallmark of these modifications is DNA methylation at cytosine residues of CpG dinucleotides in gene promoters, transposons and imprinting control regions. Genomic imprinting refers to an epigenetic marking of genes that results in monoallelic expression depending on their parental origin. There are two critical time periods in epigenetic reprogramming: gametogenesis and early preimplantation development. Major reprogramming takes place in primordial germ cells in which parental imprints are erased and totipotency is restored [1]. Imprint marks are then and re-established during spermatogenesis or oogenesis, depending on sex [1-3]. Upon fertilization, genome-wide demethylation occurs followed by a wave of de novo methylation, both of which are resisted by imprinted loci [4]. Epigenetic patterns are usually faithfully maintained during development. However, this maintenance sometimes fails, resulting in the disturbance of epigenetic patterns and human disorders. For example, two fetal growth disorders, the Beckwith-Wiedemann (BWS) and the Silver-Russell (SRS) syndromes with opposite phenotypes, are caused by abnormal DNA methylation at the 11p15 imprinted locus [5-7]: respectively loss of methylation at the Imprinting Region Center (ICR2) or gain of methylation at ICR1 in BWS and loss of methylation at ICR1 in SRS. Early embryogenesis is a critical time for epigenetic regulation, and this process is sensitive to environmental factors. The use of assisted reproductive technology (ART) has been shown to induce epigenetic alterations and to affect fetal growth and development [8-11]. In humans, several imprinting disorders, including BWS, occur at significantly higher frequencies in children conceived with the use of ART than in children conceived spontaneously [12,13]. The cause of these epigenetic imprinting disorders (following ART, unfertility causes, hormonal hyperstimulation, in vitro fertilization-IVF, Intracytoplasmic sperm injection-ICSI, micro-manipulation of gametes, exposure to culture medium, in vitro ovocyte maturation, time of transfer) remains unclear. However, recent data have shown that in patients with BWS or SRS, including those born following the use of ART, the DNA methylation defect involves imprinted loci other than 11p15 [14,15] (11p15 region: CTCF binding sites at ICR1, H19 and IGF2 DMRs, KCNQ1OT1 [ICR2], SNRPN [chromosome 15 q11-13], PEG/MEST1 [chromosome 7q31], IGF type2 receptor and ZAC1 [chromosome 6q26 et 6q24 respectively], DLK1/GTL2-IG-DMR [chromosome 14q32] and GNAS locus [chromosome 20q13.3]). This suggests that unfaithful maintenance of DNA methylation marks following fertilization involves the dysregulation of a trans-acting regulatory factor that could be altered by ART.

Folliculogenesis and morphometry of oocyte and follicle growth in the feline ovary.

This study was designed to describe, both quantitatively (morphometry) and qualitatively (histological differentiation), follicle and oocyte growth in the feline ovary. The ovaries of 43 cats were collected and processed for histology. The diameters of 832 follicle/oocyte pairs were measured, with and without zona pellucida (ZP), and a special emphasis was placed on the study of early folliculogenesis. Primordial, primary, secondary, pre-antral and early antral follicles were measured at 44.3, 86.2, 126.0, 155.6 and 223.8 microm in diameter respectively. A biphasic pattern of follicle and oocyte growth was observed. Before antrum formation, follicle (x) and oocyte (y) size were positively and linearly correlated (y = 0.500x + 20.01, r(2) = 0.89). Antrum formation occurred when the follicle reached 160-200 microm in diameter (when oocyte was at 102 microm). After antrum formation, a decoupling was observed, a minimal increase in oocyte size contrasting with a significant follicle development (y = 0.001x + 114.39, r(2) = 0.01). The pre-ovulatory follicle diameter was approximately 3500 microm and the maximal oocyte diameter was 115 microm. The ZP, absent in primordial and primary follicles, appeared at the secondary stage and reached almost 6 microm at the pre-ovulatory stage. These results suggest that (i) in feline ovary, follicle and oocyte growth pattern is similar to that observed in other mammals; (ii) the antrum forms in 160-200 microm follicles, which represents 5% of the pre-ovulatory diameter and (iii) the oocyte had achieved more than 90% of its maximal growth at the stage of antrum formation.

The epigenetic imprinting defect of patients with Beckwith-Wiedemann syndrome born after assisted reproductive technology is not restricted to the 11p15 region.

BACKGROUND: Genomic imprinting refers to an epigenetic marking resulting in monoallelic gene expression and has a critical role in fetal development. Various imprinting diseases have recently been reported in humans and animals born after the use of assisted reproductive technology (ART). All the epimutations implicated involve a loss of methylation of the maternal allele (demethylation of KvDMR1/KCNQ1OT1 in Beckwith-Wiedemann syndrome (BWS), demethylation of SNRPN in Angelman syndrome and demethylation of DMR2/IGF2R in large offspring syndrome), suggesting that ART impairs the acquisition or maintenance of methylation marks on maternal imprinted genes. However, it is unknown whether this epigenetic imprinting error is random or restricted to a specific imprinted domain. AIM: To analyse the methylation status of various imprinted genes (IGF2R gene at 6q26, PEG1/MEST at 7q32, KCNQ1OT1 and H19 at 11p15.5, and SNRPN at 15q11-13) in 40 patients with BWS showing a loss of methylation at KCNQ1OT1 (11 patients with BWS born after the use of ART and 29 patients with BWS conceived naturally). RESULTS: 3 of the 11 (27%) patients conceived using ART and 7 of the 29 (24%) patients conceived normally displayed an abnormal methylation at a locus other than KCNQ1OT1. CONCLUSIONS: Some patients with BWS show abnormal methylation at loci other than the 11p15 region, and the involvement of other loci is not restricted to patients with BWS born after ART was used. Moreover, the mosaic distribution of epimutations suggests that imprinting is lost after fertilisation owing to a failure to maintain methylation marks during pre-implantation development.

Hormonal regulation of fetal growth.

Fetal growth is a complex process depending on the genetics of the fetus, the availability of nutrients and oxygen to the fetus, maternal nutrition and various growth factors and hormones of maternal, fetal and placental origin. Hormones play a central role in regulating fetal growth and development. They act as maturational and nutritional signals in utero and control tissue development and differentiation according to the prevailing environmental conditions in the fetus. The insulin-like growth factor (IGF) system, and IGF-I and IGF-II in particular, plays a critical role in fetal and placental growth throughout gestation. Disruption of the IGF1, IGF2 or IGF1R gene retards fetal growth, whereas disruption of IGF2R or overexpression of IGF2 enhances fetal growth. IGF-I stimulates fetal growth when nutrients are available, thereby ensuring that fetal growth is appropriate for the nutrient supply. The production of IGF-I is particularly sensitive to undernutrition. IGF-II plays a key role in placental growth and nutrient transfer. Several key hormone genes involved in embryonic and fetal growth are imprinted. Disruption of this imprinting causes disorders involving growth defects, such as Beckwith-Wiedemann syndrome, which is associated with fetal overgrowth, or Silver-Russell syndrome, which is associated with intrauterine growth retardation. Optimal fetal growth is essential for perinatal survival and has long-term consequences extending into adulthood. Given the high incidence of intrauterine growth retardation and the high risk of metabolic and cardiovascular complications in later life, further clinical and basic research is needed to develop accurate early diagnosis of aberrant fetal growth and novel therapeutic strategies.

Mutation and methylation analysis of TP53 in adrenal carcinogenesis.

AIM: To investigate the role of coding region mutation and promoter hypermethylation of TP53 in adrenocortical cancer formation. METHODS: Twenty sporadic adrenocortical cancers (ACCs) and five normal adrenal tissue samples were available for analysis. Coding region mutation of TP53 in 20 ACCs was examined by polymerase chain amplification using intronic primers for exons 2-11 and direct sequencing of the product. In 10 ACCs and five normal adrenal tissue specimens, methylation of the 16 CpG sites within the TP53 promoter was examined using bisulphite methylation sequencing. RESULTS: Coding region mutation in TP53 was demonstrated in 5 of 20 ACCs. There were four mis-sense mutations and one frameshift mutation. Four of 5 patients with a TP53 mutation had metastases at diagnosis or detected soon thereafter and 3 of 4 died of disease within 12 months of surgical resection. No methylation was seen in the TP53 promoter in 10 ACC and the five normal adrenal tissues examined. CONCLUSION: Coding region mutation in TP53 occurs in 25% of ACCs with a trend toward a poorer prognosis. Promoter methylation of TP53 is not present in ACC as a mechanism for tumour suppressor gene (TSG) inactivation and, therefore, other genes in the 17p13 region are implicated in adrenal carcinogenesis.

[Air or oxygen for neonatal resuscitation in the delivery room?]. / Air ou oxygène pour le nouveau-né en salle de naissance?

Most of the contemporary guidelines on newborn resuscitation are based on experience but lack scientific evidence. The use of 100% oxygen is one of the more evident. Today, these practices are questioned, particularly for the resuscitation of moderately depressed full term or near term newborns. Results of recent meta-analysis of trials that compared ventilation with air versus pure oxygen at birth suggests current practices should be revisited. On the basis of these data, air can be the initial gas to use for these babies. Large scale trials, including preterm and cause and/or severity of initial asphyxia, must now be undertaken before the publication of new guidelines for these populations. Particularly severely asphyxiated infants might require supplemental oxygen with titration of oxygen delivery and continuous monitoring of oxygen saturation.

Sonographic findings in Beckwith-Wiedemann syndrome related to H19 hypermethylation.

Beckwith-Wiedemann syndrome (BWS) is an overgrowth syndrome associated with congenital malformations and tumour predisposition. BWS results from variable mutations or epigenetic modifications of imprinted genes in the 11p15 chromosomal region. We present a fetus with mild general overgrowth and bilateral enlarged echogenic kidneys with loss of the corticomedullary differentiation in which prenatal diagnosis of BWS was suspected. The rest of the fetal anatomy and the amniotic fluid volume appeared normal. After termination of the pregnancy, molecular analysis confirmed the diagnosis of BWS by showing an isolated hypermethylation of the H19 gene.

Use of a topoisomerase I inhibitor (irinotecan, CPT-11) in metastatic adrenocortical carcinoma.

BACKGROUND: Complete responses are rare after medical treatment of adrenocortical tumors. We performed a single center prospective study of the antitumor effect of irinotecan (CPT-11) in patients with metastatic adrenocortical cancer. PATIENTS AND METHODS: Since 1999, all patients with advanced progressive adrenocortical carcinoma, referred to the Institut Gustave-Roussy, have been enrolled prospectively in this study. CPT-11 (250 mg/m(2)) was administered intravenously on day 1 in a 2-h infusion, every 14 days. World Health Organization (WHO) criteria were used to evaluate tumor response and toxicity. RESULTS: During treatment, no dose or schedule modifications were made. A median of three courses were given (range 1-8), and all but two patients received at least three complete chemotherapy courses. No objective or complete responses were observed. The best response achieved was stabilization in three patients, lasting from 1.5 to 4 months. Significant toxicity occurred in two patients. CONCLUSIONS: Our results do not support a major role of CPT-11 in adrenocortical carcinoma.

Expression of the gene for the alpha-subunit of inhibin in human adrenocortical tumours.

BACKGROUND: To determine whether the pathogenesis of human adrenocortical tumours is associated with variations of inhibin expression, we assayed the mRNA of the alpha-subunit of inhibin in 5 normal adrenals and 48 adrenocortical tumours, including 10 paediatric tumours. RESULTS: mRNA of alpha-subunit of inhibin was detected in all adrenocortical tissues. It was similarly abundant in the three pathological groups of adult tumours (benign, suspect and malignant) and in normal adrenal tissues, irrespective of the hormonal pattern. However, in paediatric tumours, the levels of the mRNA for the alpha-subunit of inhibin were significantly higher than those in adult tumours (p < 0.01). CONCLUSION: Inhibin is more abundant in the foetal than in the adult adrenal cortex and therefore these data suggest that the paediatric tumours may have a foetal pattern.

Molecular markers and long-term recurrences in a large cohort of patients with sporadic adrenocortical tumors.

Genetic alterations, such as loss of heterozygosity (LOH) at the 17p13 and 11p15 loci and overexpression of the insulin-like growth factor (IGF)-II gene, are associated with the malignant phenotype in sporadic adrenocortical tumors. A high risk of recurrence after surgery for adrenocortical tumors is predicted in cases with regional invasion or distant metastases. However, patients with localized tumors also have a high risk of recurrence. Reliable prognostic markers are required to identify subjects at high risk of recurrence. The aim of this study was to assess the prognostic value of three molecular markers (17p13 LOH, 11p15 LOH, and overexpression of the IGF-II gene) by assessing disease-free survival in a large series of adult patients with sporadic adrenocortical tumors. Adult patients (114) were prospectively followed up from diagnosis of the disease to June 1999 or to death. Malignancy was initially diagnosed in 18 patients (McFarlane stage III: n = 1 and stage IV: n = 17). The remaining 96 patients with localized adrenal disease at diagnosis (stage I: n = 60 and stage II: n = 36) were at risk of recurrence. Histological grade was assessed according to Weiss criteria, and tumors were classified into two groups (Weiss score or=4). Tumor samples were analyzed for LOH at the 17p13 and 11p15 loci and for IGF-II gene mRNA content. 17p13 LOH was a strong predictor of shorter disease-free survival in univariate analysis (P = 0.001; relative risk, 27), as were histological grade (Weiss score >or=4; P = 0.00001; relative risk, 15), 11p15 LOH (P = 0.004; relative risk, 9), tumor size (size >5 cm; P = 0.006; relative risk, 18), and overexpression of the IGF-II gene (P = 0.01; relative risk, 5). In a Cox proportional hazards regression model, histological grade (P = 0.04; relative risk, 4.2) and 17p13 LOH (P = 0.009; relative risk, 21.5) were independently associated with recurrence. Molecular markers, particularly 17p13 LOH, are predictive of long-term outcome in patients with sporadic adrenocortical tumors. In patients who have undergone curative surgery, routine assessment of these tumor markers is a useful complement to histological scoring for predicting recurrence and guiding decisions for subsequent follow-up and management.

Altered expression of novH is associated with human adrenocortical tumorigenesis.

NOVH belongs to the CCN (CTGF/CYR61/NOV) family of proteins, some of which have chemotactic, mitogenic, adhesive, and angiogenic properties. Whereas ctgf and cyr61 are growth factor-inducible, immediate-early genes, nov is expressed in growth-arrested or quiescent cells. As nov expression has been shown to be altered in both avian and human nephroblastomas and to be a target of WT1 regulation, NOV may play important roles in normal nephrogenesis and the development of Wilms' tumors. The aim of this study was to determine whether changes in novH expression were associated with tumorigenesis in tissues other than those of the kidney. We showed by Northern blotting and immunohistochemistry that among human adult endocrine tissues, the adrenal gland is a major site of novH expression, and that in adult and fetal adrenal tissue, novH is primarily expressed in the adrenal cortex. Studies with 12 benign and 18 malignant adrenocortical tumors revealed that the levels of novH mRNA and protein decreased significantly (P < 0.004) with progression of adrenocortical tumors from a benign to a malignant state. Although the localization of NOVH did not change, the N-glycosylation profile of benign and malignant tumors differed considerably from that of normal adrenocortical tissue, and these differences may affect the biochemical properties of the molecule. The properties of NOVH here provide the first evidence that this member of the CCN family could be involved in adrenocortical tumor development.

Analysis of the methylation status of the KCNQ1OT and H19 genes in leukocyte DNA for the diagnosis and prognosis of Beckwith-Wiedemann syndrome.

Beckwith-Wiedemann syndrome (BWS) is an overgrowth disorder involving developmental abnormalities, tissue and organ hyperplasia and an increased risk of embryonal tumours (most commonly Wilms tumour). This multigenic disorder is caused by dysregulation of the expression of imprinted genes in the 11p15 chromosomal region. Molecular diagnosis of BWS is currently difficult, mostly due to the large spectrum of genetic and epigenetic abnormalities. The other difficulty in managing BWS is the identification of patients at risk of tumour. An imprinted antisense transcript within KCNQ1, called KCNQ1OT (also known as LIT1), was recently shown to be normally expressed from the paternal allele. A loss of imprinting of the KCNQ1OT gene, associated with the loss of maternal allele-specific methylation of the differentially methylated region KvDMR1 has been described in BWS patients. The principal aim of this study was to evaluate the usefulness of KvDMR1 methylation analysis of leukocyte DNA for the diagnosis of BWS. The allelic status of the 11p15 region and the methylation status of the KCNQ1OT and H19 genes were investigated in leukocyte DNA from 97 patients referred for BWS and classified into two groups according to clinical data: complete BWS (CBWS) (n=61) and incomplete BWS (IBWS) (n=36). Fifty-eight (60%) patients (39/61 CBWS and 19/36 IBWS) displayed abnormal demethylation of KvDMR1. In 11 of the 56 informative cases, demethylation of KvDMR1 was related to 11p15 uniparental disomy (UPD) (nine CBWS and two IBWS). Thirteen of the 39 patients with normal methylation of KvDMR1 displayed hypermethylation of the H19 gene. These 13 patients included two siblings with 11p15 trisomy. These results show that analysis of the methylation status of KvDMR1 and the H19 gene in leukocyte DNA is useful in the diagnosis of 11p15-related overgrowth syndromes, resulting in the diagnosis of BWS in more than 70% of investigated patients. We also evaluated clinical and molecular features as prognostic factors for tumour and showed that mosaicism for 11p15 UPD and hypermethylation of the H19 gene in blood cells were associated with an increased risk of tumour.

[Involvement of the IGF system in the pathogenesis of adrenocortical tumors]. / Anomalies du système des IGFs dans les tumeurs cortico-surrénaliennes.

Adrenocortical carcinoma remains a challenge for the therapeutist; prognosis is ominous. Various abnormalities playing a pathogenetic role have been recently described in adrenocortical tumors. Among them, dysregulation of the IGF system and imprinting mistakes at the 11p15 locus play a determining role in malignant transformation of adrenocortical cells. These markers of the malignant phenotype might markedly improve our diagnosis and prognosis abilities.

Loss of heterozygosity at the mannose 6-phosphate/insulin-like growth factor 2 receptor locus: a frequent but late event in adrenocortical tumorigenesis.

OBJECTIVE: Recent studies have pointed to the role of the IGF system in adrenocortical tumorigenesis. The IGF-II gene is overexpressed in malignant adrenocortical tumors and its proliferative effects are mediated by the type-1 IGF receptor (IGF1R). The mannose 6-phosphate/IGF2 receptor (M6P/IGF2R) plays a key role in regulating cell growth, by ensuring the clearance and inactivation of IGF-II and facilitating activation of the growth inhibitor, transforming growth factor beta (TGFbeta1). The M6P/IGF2R has been implicated as a tumor suppressor gene in various human tumors. METHODS: The purpose of this study was to determine if the M6P/IGF2R is involved in adrenal tumorigenesis. Two polymorphisms in the 3' untranslated region of M6P/IGF2R were used to screen a large series of 76 sporadic adrenocortical tumors for loss of heterozygosity (LOH) by PCR amplification of DNA. Tumors were classified into three groups based on pathological features: benign tumors (n=25), suspect tumors (n=22) and malignant tumors (n=29). RESULTS: LOH at the M6P/IGF2R locus was detected in 15 of 57 (26%) informative tumors and was more frequent in malignant tumors (58%) than in benign and suspect tumors (9 and 13% respectively). CONCLUSION: These findings provide evidence that LOH at the M6P/IGF2R locus is a frequent event in adrenocortical tumors and support the hypothesis that it may function as a tumor suppressor gene in adrenocortical tumorigenesis.