Somatic overgrowth associated with overexpression of insulin-like growth factor II

Overexpression of the normally imprinted fetal insulin-like growth factor II (IGF2) has been implicated in the pathogenesis of the cancer-predisposing Beckwith-Wiedemann syndrome (BWS). We have detected constitutional relaxation of imprinting of IGF2 in four children with somatic overgrowth who do not show diagnostic features of BWS. Three children showed constitutional abnormalities of H19 methylation. All four children showed nephromegaly and two developed Wilms' tumors. Gene methylation is known to be associated with gene silencing, and three children showed constitutional abnormalities of H19 gene methylation. Disruption of H19 methylation, and concomitant relaxation of IGF2 imprinting, provides another mechanism that can increase IGF2 expression in children with overgrowth. The accumulated data on normal and pathologic IGF2 expression are now sufficient to define an entity, "IGF2 overgrowth disorder," of which BWS may be one extreme manifestation. These findings have broad implications for the characterization of idiopathic overgrowth.

Mesenchyme to epithelium transition during development of the mammalian kidney tubule

Kidney epithelia have two separate origins. Collecting ducts develop in the manner of most glandular organs, by growth and branching of a bud derived from a pre-existing epithelium. Excretory tubules develop by a direct mesenchyme to epithelium transition (MET), which is induced by the tips of the developing collecting duct system as it invades a specialised area of mesenchymal cells. The process by which these metanephrogenic mesenchyme cells achieve MET can be divided into several stages; induction, acquisition of stem cell character, fate determination, condensation, epitheliogenesis, polarisation and maturation. Progress through these stages is regulated by 'checkpoints' at which permission to proceed requires specific signals. The stages of development are characterised by the expression of new combinations of genes that code for transcription factors (Hox genes, Pax genes, zinc finger proteins), signalling effectors (growth factors, Wnts, receptor tyrosine kinases) and morphoregulatory molecules (CAMs, cadherins, extracellular matrix ligands). This review summarises current knowledge about the molecular interactions that control MET in the kidney, and also about how their failure might result in Wilms' tumour, one of the most common cancers of childhood.

Subnuclear localization of WT1 in splicing or transcription factor domains is regulated by alternative splicing

WT1 is a tumor suppressor gene with a key role in urogenital development and the pathogenesis of Wilms' tumor. Two alternative splice sites in the WT1 transcript allow the gene to encode four proteins. These carry four Krüppel-type zinc fingers and to date have primarily been implicated in transcriptional control of genes involved in growth regulation. However, here we demonstrate colocalization of WT1 with splicing factors in the fetal kidney and testis and in expressing cell lines. Using immunoprecipitation, we show that two WT1 isoforms directly associate with one or a limited number of components in the spliceosomes and coiled bodies. Moreover, COS cell expression studies suggest that alternative splicing within the WT1 zinc finger region determines whether the protein localizes mainly with splicing factors or with DNA in transcription factor domains in the nucleus. We propose that WT1 plays roles in posttranscriptional processing of RNA as well as in transcription.

A critical mutation in both WT1 alleles is not sufficient to cause Wilms' tumor

The WT1 gene is a tumor suppressor gene for Wilms' tumor (WT). Inactivation of both alleles has been proposed as the cause of WT. We encountered a patient with Denys-Drash syndrome associated with WT whose WT1 gene had a homozygous point mutation not only in WT but also in renal tissue adjacent to the WT and in the germline. These findings indicate that factor(s) other than the loss of WT1 are required for WT to develop.

Parental exposures to pesticides and risk of Wilms' tumor in Brazil

Wilms' tumor is one of the most common abdominal childhood malignancies. Wilms' tumor rates in Brazil are among the highest in the world. This prompted the Brazilian Wilms' Tumor Study Group to conduct a hospital-based, multicenter, case-control investigation of environmental risk factors for the disease. Between April 1987 and January 1989, the authors collected information on relevant occupational exposures by interviewing the parents of 109 Wilms' tumor cases admitted to hospitals in Sao Paulo, Salvador, Belo Horizonte, and Jau. Also interviewed were the parents of 218 age- and sex-matched control children who had been admitted for treatment of nonneoplastic diseases to the same or nearby hospitals. Odds ratios (ORs) adjusted for income and education were calculated by conditional logistic regression. Consistently elevated risks were seen for farm work involving frequent use of pesticides by both the father (OR = 3.24, 95% confidence interval (CI) 1.2-9.0) and the mother (OR = 128.6, 95% CI 6.4-2,569). These risk elevations were restricted to cases diagnosed after 2 years of age (ORs > 4), for paternal exposure, and after 4 years of age (OR = 14.8, 95% CI 2.2-98.8), for maternal exposure. Risk elevations were also more pronounced among boys (paternal exposure OR = 8.56, 95% CI 2.1-35.1; maternal exposure OR = 4.60, 95% CI 0.8-26.4) than among girls (paternal exposure OR = 1.31, 95% CI 0.4-4.1; maternal exposure OR = 2.03, 95% CI 0.5-8.9).

[Wilm's tumor: review and up-date based on our experience]

Wilms' tumour represents 8% of tumours appearing during childhood, and it is the more frequent malignant tumour of the urinary tract in children. A review of 7 tumours occurring in our Hospital Area over the last 11 years is made, evaluating their incidence, clinical presentation, diagnosis as well as therapeutical approaches and complications. We also conducted a review of the most recent related literature, paying special attention to the new lines of research in the field of the genetics. Likewise, we contribute the latest guidelines and suggestions by the NWTS with regard to diagnosis and treatment of Wilms' tumour.

Etiology of Wilms' tumor

Present knowledge of the pathogenesis of Wilms' tumor can be used to plan further epidemiologic investigations in a logical manner. Table 3 summarizes the epidemiologic evidence presently available that implicates various exposures. The proportion of cases of Wilms' tumor that arise from germline mutations is unknown. Future case-control studies could contribute to providing such information by systematically collecting and preserving constitutional genetic material from cases and their parents and neoplastic genetic material from their tumors. The studies that have demonstrated germline mutations so far have involved small numbers of subjects, being the equivalent of "case reports" (36, 37, 45-47, 50, 53). The techniques of molecular biology will be necessary to distinguish germline mutations or equivalent events that have been transmitted by parents from those that have arisen de novo. (Since it has already been shown that phenotypically unaffected parents can transmit relevant mutations to offspring who become affected (45, 46), the presence or absence of phenotypic abnormalities in the parents cannot be used to infer whether germinal mutations have arisen de novo.) Such studies will be laborious and expensive. The best strategy to minimize cost and labor would be restriction on age; the cases diagnosed relatively early in life (before the age of 2-3 years) are more likely to have arisen from germline mutations than those diagnosed later (34). The existence of de novo germline mutations relevant to the development of Wilms' tumor should prompt epidemiologists to search for causal exposures before conception. Preliminary evidence suggests that males have a higher germinal mutation rate (48). On the basis of the epidemiologic evidence to date, Olshan et al. have suggested the following: "paternal preconceptional exposures may play a more important role in the etiology of Wilm's tumor than maternal factors"(8,p.943). Pathologic and molecular biologic studies have shown that Wilm's tumor arises from nephrogenic rests that represent renal stem cells, the development of which has been arrested before normal differentiation occurs (2,44). Exposures that occur during intrauterine life are likely to be relevant to this process; these can be studied with epidemiologic methods, and clues have emerged (7,86,89). It is important to realize, however, that the fetus may be exposed in utero to substances to which the mother was exposed prior to conception, if these substances are excreted slowly or not at all, such as the persistent organochlorine pesticides (96,98). Study of the determinants of the growth behavior of nephrogenic rests (persistence, regression, generalized growth, or malignant transformation (2)) may be possible only in an animal model of Wilm's tumor, if one can be found in which nephroblastoma arises from nephrogenic rests. Ethylnitrosurea, an alkylating agent, causes renal tumors identical to Wilm's tumor in the opossum when given early in postnatal life (103) and in the rabbit when given transplacentally (104). Nephroblastoma in animals is one of the very few types of tumors that is inducible by chemicals via the transplacental route. This mode of induction should be regarded as as an etiologic possibility in humans as well as animals (105). As Hard, however, has pointed out, "nodular renal blastema [now known as nephrogenic rests] or nephroblastomatosis...have [sic] never been described in conjunction with nephroblastoma of animals" (105,p.184). the renal stem cells that give rise to Wilm's tumor normally disappear 4-6weeks prior to birth (19). If they persist after birth, as nephrogenic rests or otherwise, postnatal exposures could contribute to the development of Wilm's tumor. Cases diagnosed later, especially those presenting with lower stage disease, are more likely to have arisen from mutations occurring after birth. Potential carcinogens in children's diet and the home environment are worthy of close study.

Increased birth weights of National Wilms' Tumor Study patients suggest a growth factor excess

An analysis of over 1800 patients with Wilms' tumor revealed significantly higher birth weights than newborns in the general United States population. The highest birth weights were found not only in patients diagnosed with the Beckwith-Wiedemann syndrome (mean, 3.78 kg), as had been expected, but also in those with hemihypertrophy (3.80 kg) or perilobar nephrogenic rests (3.56 kg) in addition to their Wilms' tumor. The birth weights of Wilms' tumor patients with intralobar nephrogenic rests (3.43 on average kg) and of those without associated anomalies (3.45 kg) were slightly but still significantly higher on average than national birthweights (overall mean, 3.35 kg) adjusted for gender, race, and year of birth in each subgroup. Birth weights of children with aniridia and Wilms' tumor (2.99 kg) were lower than the national mean. Among more than 3000 patients with Wilms' tumor, heights and weights at diagnosis were significantly higher for the subgroups of patients with Beckwith-Wiedemann syndrome or hemihypertrophy, and height was lower for those with aniridia or characteristic genitourinary anomalies, when compared to other patients with Wilms' tumor. These data suggest prenatal effects of growth factors on the development of Wilms' tumors, or vice versa, and provide further epidemiological support for heterogeneity in the pathogenesis of Wilms' tumors associated with perilobar nephrogenic rests versus intralobar nephrogenic rests.

Wilms' tumor arising in a multicystic kidney

We describe a child with Wilms' tumor (WT) which occurred in an unequivocal multicystic dysplastic kidney (MDK). We indicate a current nonsurgical approach to MDK, but stress the probable malignant degeneration of blastemal cells, the need to search carefully for the WT in the MDK, and the necessity on 3-monthly follow-up US studies.

Sequential development of Wilms tumor, T-cell acute lymphoblastic leukemia, medulloblastoma and myeloid leukemia in a child with type 1 neurofibromatosis: a clinical and cytogenetic case report

In her 8 1/2 years of life, a girl with neurofibromatosis type 1 (NF1) developed four sequential primary malignant neoplasms: Wilms tumor, T-cell acute lymphoblastic leukemia, medulloblastoma and acute myeloid leukemia. The last three tumors were characterized by chromosomal abnormalities non-randomly associated with that particular disease. There was no evidence of germline p53 mutation or of mutation of p53 in the last two tumors. We hypothesize that an unusual mutation of the NF1 gene in this child promoted growth in tissues where the normal or mutated NF-1 gene product is usually silent or growth inhibitory.

Embryonic kidney rudiments grown in adult mice fail to mimic the Wilms' phenotype, but show strain-specific morphogenesis

12.5- to 14.5-day mouse embryonic kidney fragments were grown syngeneically under kidney or testis capsules in 3 mouse strains for 5-26 weeks to reproduce the Wilms' tumour (WT) phenotype previously reported. About 65% of the transplants grew, but none showed true WT morphology, invaded local tissue or developed metastases. In Swiss mice, most growths contained disorganized stromal and blast cells, but also had more mature structures. CBA growths had cysts, differentiated nephrons and glomeruli, while 129/SV growths gave both types of morphology. In situ mRNA hybridization using the Wilms' tumour predisposition gene (WT1) showed that, unlike the initial rudiments and WT, expression was limited to the glomeruli. The unexpected absence of expression by the apparent blast cells in the growths implies that the system is not a model for WT.

Wilms' tumour and parental age: a report from the National Wilms' Tumour Study

Age distributions of parents at birth of patients registered in the National Wilms' Tumour Study were compared to those of the general population. An increasing incidence of sporadic Wilms' tumour with increasing paternal age was found, with a relative risk of 2.1 of tumour in children of fathers over 55 compared to children of fathers younger than 20. A similar effect for maternal age was found, with a relative risk of 1.4 in children of mothers over 40 compared to children of mothers younger than 20. The maternal age effect was much weaker among patients registered later in the study; in the later, more completely ascertained cohort, paternal age appears to be the major contributor to the parental age effect. Little difference in paternal age distribution was found between patients with bilateral and unilateral tumour and between male and female patients. In contrast, patients with reported associated congenital anomalies, patients with evidence of nephrogenic rests, and patients with early or late age-of-onset of tumour had parents who were, on average, substantially older than the remainder. These findings lend support to the idea that many Wilms' tumours result from new germline mutations. Further, the histologic composition of such tumours may be sufficiently distinct as to provide a valuable diagnostic indicator of the etiology of these tumours.

The aetiology of cancer in the very young

Epidemiological studies of cancer in young children have implicated a number of environmental factors, which need to be studied in more detail, but it is probably fair to say that the main benefit of these studies has come from the negative findings, which have served to exclude (or at least place an upper limit on the role of) potential risk factors. Our inability to identify environmental causes could mean either that the environment does not substantially affect cancer incidence in young children, or that we are simply not looking in the right places. Most attention has naturally been focused on the known and suspected environmental carcinogens and mutagens. Based on the data summarised in this paper, one possibility is that the most important mutagen is endogenous: 5-methyl-cytosine. If so, factors increasing cancer risk could be those which increase the rate of spontaneous deamination, or impair the efficiency of the excision repair enzymes, or regulate the processes of CpG methylation and demethylation. These factors could still be classed as mutagens in their own right, since they would lead to an increase in uncorrected point mutations, but they would be distinctive in a number of ways. Firstly, since the role of methylation in bacteria is very different from that in eukaryotic cells the Ames mutagenicity assay could not be relied upon to detect methylation-mediated mutagens. Furthermore the risk may be highly age dependent, reflecting changes in methylation patterns with growth and cellular differentiation. Agents which disrupted the imprinting process in the testis would not be detectable by animal carcinogenicity tests unless specifically looked for.(ABSTRACT TRUNCATED AT 250 WORDS)

Maternal and perinatal risk factors for Wilms' tumor: a nationwide nested case-control study in Sweden

This report describes maternal and perinatal risk factors for Wilms' tumor analyzed in a case-control study nested in a nationwide cohort in Sweden. The Swedish National Cancer Registry ascertained 110 cases from among successive birth cohorts from 1973 through 1984, identified by the Swedish Medical Birth Registry, the latter based on medical records. From the Birth Registry, we matched 5 controls without cancer to each case by sex and date of birth. Wilms'-tumor children were more likely to have mothers who had been exposed to penthrane (methoxyflurane) anesthesia during delivery than mothers of controls (odds ratio (OR) = 2.4; 95% confidence interval (CI) 1.1 to 5.1); this excess risk was higher in females than males and increased with age at diagnosis. Wilms'-tumor cases were also more likely to have had physiologic jaundice (OR = 2.3; 95% CI 1.1 to 5.0). Higher parity of the mother decreased the risk of Wilms' tumor among females (OR = 0.7; 95% CI 0.5 to 1.0). We were unable to confirm the reported increased risks of Wilms' tumor for those with high birth weights or with a maternal history of hypertension or fluid retention during pregnancy, nor did we find any association with mother's age at delivery, previous stillbirth, previous live birth, gestational length or height of the child.

Nephrogenesis and the development of renal disease

Over the last few years there has been considerable progress in analysing the cellular basis of nephrogenesis and a start has been made towards elucidating the underlying molecular controls of this process. In this review we begin by describing how the kidney forms and then consider recent work on the mechanisms underlying these events. We review evidence implicating a neural basis for kidney induction and go on to show how the induced metanephric mesenchyme aggregates and forms condensations which themselves polarize to form epithelia and filtering nephrons. We then discuss how changes in the extracellular matrix are implicated in these processes and how the expression of nuclear transcription factors may regulate the final phenotype of the kidney. Finally, we show how the study of nephrogenesis is beginning to shed light on the aetiology of a range of disorders that include renal malformations, renal tumours, and inherited glomerular and polycystic kidney diseases.

Occurrence of testicular cancer in patients operated on for cryptorchidism and inguinal hernia

We studied the incidence of testicular cancer in 2 population-based cohorts comprising 2,918 men who underwent an operation for a cryptorchid testis and 30,199 who underwent surgery for an inguinal hernia. Complete followup during the 19-year period was achieved by record linkage to the National Swedish Cancer Registry. In the cryptorchidism cohort 4 cases of testicular cancer occurred versus 0.54 expected, yielding a relative risk of 7.4 (95% confidence interval 2.0 to 19.0). Of these patients 3 had undergone a bilateral operation due to intra-abdominal testes. There was no evidence of an association between inguinal hernia and risk of testicular cancer (relative risk = 1.1, 95% confidence interval 0.4 to 2.2). The validity of our data was further supported by relative risk estimates close to unity in a comparison group of appendectomy patients. We conclude that patients with a cryptorchid testis experience a substantially increased relative risk of testicular cancer. However, the low absolute risk, 4 cases during 25,360 person-years of observation, does not appear to justify special surveillance after an operation for an undescended testis.

Medullary sponge kidneys and unilateral Wilms tumour in a child with Beckwith-Wiedemann syndrome

The occurrence of a Wilms tumour in a 4-year-old girl with bilateral medullary sponge kidney. Beckwith-Wiedemann syndrome and congenital hemihypertrophy demonstrates the close relationship between these disorders. Another six cases from the literature with congenital hemihypertrophy and with medullary sponge kidney are discussed, two of them also developed intraabdominal neoplasm.

Wilms' tumor and paternal occupation

A case-control study was conducted to examine the relationship between Wilms' tumor and paternal occupational exposures. The case group consisted of 200 children diagnosed as having Wilms' tumor who were registered at selected National Wilms' Tumor Study institutions during the period June 1, 1984, to May 31, 1986. Disease-free controls were matched to each case using a random digit dialing procedure. The parents of cases and controls completed a self-administered questionnaire. There was no consistent pattern of increased risk for paternal occupational exposure to hydrocarbons or lead found in this study. However, certain paternal occupations were found to have an elevated odds ratio (OR) of Wilms' tumor, including vehicle mechanics, auto body repairmen, and welders. Offspring of fathers who were auto mechanics had a 4- to 7-fold increased risk of Wilms' tumor for all 3 time periods. The largest increased odds ratio for auto mechanics was in the preconception period [OR = 7.58; 95% confidence interval (CI) = 0.90-63.9]. Welders had a 4- to 8-fold increased odds ratio, with the strongest association during pregnancy (OR = 8.22; CI = 0.95-71.3). Although chance cannot be excluded as a possible explanation, association of Wilms' tumor with these occupations has been reported in previous studies. Further study is needed to provide data on the specific occupational exposures involved.

Malignant tumors during the first 2 decades of life in the offspring of atomic bomb survivors

The risk of cancer (incidence) prior to age 20 years has been determined for children born to atomic bomb survivors and to a suitable comparison group. Tumor ascertainment was through death certificates and the tumor registries maintained in Hiroshima and Nagasaki. The rationale for the study stemmed from the evidence that a significant proportion of such childhood tumors as retinoblastoma and Wilms tumor arise on the basis of a mutant gene inherited from one parent plus a second somatic cell mutation involving the allele of this gene. Gonadal radiation doses were calculated by the recently established DS86 system, supplemented by an ad hoc system for those children for one or both of whose parents a DS86 dose could not be computed but for whom an ad hoc dose could be developed on the basis of the available information. The total data set consisted of (1) a cohort of 31,150 live-born children one or both of whose parents received greater than 0.01 Sv of radiation at the time of the atomic bombings (average conjoint gonad exposure 0.43 Sv) and (2) two suitable comparison groups totaling 41,066 children. Altogether, 43 malignant tumors were ascertained in the children of exposed parents, and 49 malignant tumors were ascertained in the two control groups. A multiple linear regression analysis revealed no increase in malignancy in the children of exposed parents. However, examination of the data suggested that only 3.0-5.0% of the tumors of childhood that were observed in the comparison groups are associated with an inherited genetic predisposition that would be expected to exhibit an altered frequency if the parental mutation rate were increased. There is thus far no confirmation of the positive findings that Nomura found in a mouse system.

Cystic nephroma: an emerging entity

Cystic nephroma is a rare lesion, but there has been an increased number of cases reported in the recent literature. Most cases have been discovered incidentally either on routine examination or during radiological investigations. There are two peaks of incidence, one in childhood and one in middle age and the condition is often wrongly presumed to be a malignant tumor. Cystic nephroma is a benign neoplasm and it can be confidently diagnosed using modern imaging techniques and tissue analysis. Classically, the treatment of cystic nephroma has been simple nephrectomy, although a few cases have been treated by enucleation. Simple nephrectomy is the treatment of choice in children as the diagnosis in the young is less exact and a cure is assured. In some adult patients it is reasonable to pursue a conservative policy with regular clinical and ultrasound examinations.

Molecular genetic evidence for common pathogenesis of childhood and adult Wilms' tumor

A case of Wilms' tumor in an adult is reported, showing, by restriction fragment length polymorphism analysis of somatic and tumor DNA, the loss of alleles from the short arm of chromosome 11. Loss of alleles in this region has previously been reported in childhood Wilms' tumor. The findings of this study indicate that adult Wilms' tumor and childhood Wilms' tumor may share a common pathogenic pathway. These results may also be useful in differentiating between Wilms' tumor and renal cell carcinoma or sarcoma in adults when the histologic findings are unclear.