Chromosome 11q loss and MYCN amplification demonstrate synthetic lethality with checkpoint kinase 1 inhibition in neuroblastoma

Neuroblastoma is the most common extracranial solid tumor found in children and despite intense multi-modal therapeutic approaches, low overall survival rates of high-risk patients persist. Tumors with heterozygous loss of chromosome 11q and MYCN amplification are two genetically distinct subsets of neuroblastoma that are associated with poor patient outcome. Using an isogenic 11q deleted model system and high-throughput drug screening, we identify checkpoint kinase 1 (CHK1) as a potential therapeutic target for 11q deleted neuroblastoma. Further investigation reveals MYCN amplification as a possible additional biomarker for CHK1 inhibition, independent of 11q loss. Overall, our study highlights the potential power of studying chromosomal aberrations to guide preclinical development of novel drug targets and combinations. Additionally, our study builds on the growing evidence that DNA damage repair and replication stress response pathways offer therapeutic vulnerabilities for the treatment of neuroblastoma.

QOL-07. The importance of an onco-fertility program for pediatric neuro-oncology patients

INTRODUCTION: In the Netherlands pediatric oncology care is centralized in one hospital since 2018. 600 new patients a year are seen with 100-120 new neuro-oncology (NO) patients. Of the NO patients 20-25% classify as high risk for infertility (HR) such as patients with medulloblastoma, ependymoma, ATRT and germinoma . An onco-fertility program was started navigated by a nurse-practitioner. The program runs with intense collaboration between the different specialties. All new patients are identified according to the international guidelines on fertility care. The fertility-risk is based on the CED score (cyclofosfamide equivalent dose) and radiotherapy dose. Since 2018 awareness was created by teaching sessions among colleagues, nursing staff, and parent association organizations. METHODS: All HR children are informed by the nurse-practitioner and can be referred for counseling to gynaecology for OTC (ovarian tissue cryopreservation) or urology for sperm cryopreservation or testicular biopsy. Monthly the onco-fertility working-group members discuss cases and research in the field. RESULTS: In 2019, 19% NO cases and in 2020 18% of cases were HR for infertility. In both years 36% of these cases had fertility preservation performed. In 2021, 22% cases HR were identified and in 55% preservation was performed. Reasons for not preserving fertility were diverse, varying from poor prognosis, or too ill to be included. CONCLUSION: Awareness of the fertility risk in NO patients who are HR is necessary. These patients need to be informed, and stratified for counseling and offered fertility preservation before start of their treatment. An active onco-fertility program helps to offer the best option for future fertility for these patients

Under-reported aspects of diagnosis and treatment addressed in the Dutch-Flemish guideline for comprehensive diagnostics in disorders/differences of sex development

We present key points from the updated Dutch-Flemish guideline on comprehensive diagnostics in disorders/differences of sex development (DSD) that have not been widely addressed in the current (inter)national literature. These points are of interest to physicians working in DSD (expert) centres and to professionals who come across persons with a DSD but have no (or limited) experience in this area. The Dutch-Flemish guideline is based on internationally accepted principles. Recent initiatives striving for uniform high-quality care across Europe, and beyond, such as the completed COST action 1303 and the European Reference Network for rare endocrine conditions (EndoERN), have generated several excellent papers covering nearly all aspects of DSD. The Dutch-Flemish guideline follows these international consensus papers and covers a number of other topics relevant to daily practice. For instance, although next-generation sequencing (NGS)-based molecular diagnostics are becoming the gold standard for genetic evaluation, it can be difficult to prove variant causality or relate the genotype to the clinical presentation. Network formation and centralisation are essential to promote functional studies that assess the effects of genetic variants and to the correct histological assessment of gonadal material from DSD patients, as well as allowing for maximisation of expertise and possible cost reductions. The Dutch-Flemish guidelines uniquely address three aspects of DSD. First, we propose an algorithm for counselling and diagnostic evaluation when a DSD is suspected prenatally, a clinical situation that is becoming more common. Referral to ultrasound sonographers and obstetricians who are part of a DSD team is increasingly important here. Second, we pay special attention to healthcare professionals not working within a DSD centre as they are often the first to diagnose or suspect a DSD, but are not regularly exposed to DSDs and may have limited experience. Their thoughtful communication to patients, carers and colleagues, and the accessibility of protocols for first-line management and efficient referral are essential. Careful communication in the prenatal to neonatal period and the adolescent to adult transition are equally important and relatively under-reported in the literature. Third, we discuss the timing of (NGS-based) molecular diagnostics in the initial workup of new patients and in people with a diagnosis made solely on clinical grounds or those who had earlier genetic testing that is not compatible with current state-of-the-art diagnostics.

Serum miRNA to predict post-chemotherapy viable disease in testicular non-seminomatous germ cell tumor patients

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Background: Retroperitoneal lymph node dissection (RPLND) is recommended for residual masses > 1cm post-chemotherapy (pc) for nonseminomatous germ cell tumors (NSGCT). There is no reliable predictor for pcRPLND histology and up to 50% will harbour necrosis/fibrosis only, thus rendering a potentially morbid surgery to be of limited therapeutic value. Objective: To evaluate the ability of defined serum microRNA (miRNA) using the ampTSmiR test to predict residual viable NSGCT after chemotherapy. Methods: Serum miRNA levels (miR-371a-3p, miR-373-3p and miR-367-3p) were measured in 82 patients (cohort A = 39, cohort B = 43) treated with orchiectomy, chemotherapy and pcRPLND to predict viable GCT post-chemotherapy. Outcomes, measurements and statistical analysis: miRNA levels were compared to clinical characteristics, serum tumor markers and correlated with presence of viable GCT (vs. teratoma; vs. necrosis/fibrosis). miRNA-discriminative capacity was determined by receiver operating characteristic (ROC) analysis. Results: Serum miRNA were associated with stage at the time of chemotherapy and declined significantly post-chemotherapy. Patients with fibrosis/necrosis and teratoma had a significant decline in all three miRNA levels after chemotherapy, while those with viable disease had very little change. Patients with necrosis/fibrosis demonstrated similar miRNA levels as patients with residual teratoma. miR-371a-3p demonstrated the highest discriminative capacity [area under the curve (AUC) 0.874, CI 95% 0.774 - 0.974 p < 0.0001] for viable disease post chemotherapy. If considering a more relaxed cut-point of 3cm before consideration of pcRPLND, miR-371a-3p correctly stratified all patients with residual retroperitoneal lesions ≤ 3 cm ( p= 0.02; 100% sensitivity). Conclusions: Our study is the first to explore a miRNA-based serum test to determine histology in post-chemotherapy residual masses and we demonstrated the value of miR-371a-3p to predict presence of viable GCT. Prospective studies are required to confirm its clinical utility.

Functional characterization of novel NR5A1 variants reveals multiple complex roles in disorders of sex development

Variants in the NR5A1 gene encoding SF1 have been described in a diverse spectrum of disorders of sex development (DSD). Recently, we reported the use of a targeted gene panel for DSD where we identified 15 individuals with a variant in NR5A1, nine of which are novel. Here, we examine the functional effect of these changes in relation to the patient phenotype. All novel variants tested had reduced trans‐activational activity, while several had altered protein level, localization, or conformation. In addition, we found evidence of new roles for SF1 protein domains including a region within the ligand binding domain that appears to contribute to SF1 regulation of Müllerian development. There was little correlation between the severity of the phenotype and the nature of the NR5A1 variant. We report two familial cases of NR5A1 deficiency with evidence of variable expressivity; we also report on individuals with oligogenic inheritance. Finally, we found that the nature of the NR5A1 variant does not inform patient outcomes (including pubertal androgenization and malignancy risk). This study adds nine novel pathogenic NR5A1 variants to the pool of diagnostic variants. It highlights a greater need for understanding the complexity of SF1 function and the additional factors that contribute.

Update on the Pathophysiology and Risk Factors for the Development of Malignant Testicular Germ Cell Tumors in Complete Androgen Insensitivity Syndrome

Prophylactic gonadectomy in young adult women with complete androgen insensitivity syndrome (CAIS) to avoid development of an invasive testicular germ cell tumor (TGCT) is currently advised in most centers. However, women with CAIS increasingly question the need of this procedure. In order to provide optimal counseling and follow-up of these women, insight in the mechanisms underlying TGCT development in androgen insensitivity syndrome (AIS), data regarding the incidence of TGCT in AIS adults specifically, and an overview of existing and novel screening tools for in situ and invasive neoplastic lesions are crucial. The current knowledge regarding these topics is revised in this paper.

Disorders of sex development: insights from targeted gene sequencing of a large international patient cohort

Background

Disorders of sex development (DSD) are congenital conditions in which chromosomal, gonadal, or phenotypic sex is atypical. Clinical management of DSD is often difficult and currently only 13% of patients receive an accurate clinical genetic diagnosis. To address this we have developed a massively parallel sequencing targeted DSD gene panel which allows us to sequence all 64 known diagnostic DSD genes and candidate genes simultaneously.

Results

We analyzed DNA from the largest reported international cohort of patients with DSD (278 patients with 46,XY DSD and 48 with 46,XX DSD). Our targeted gene panel compares favorably with other sequencing platforms. We found a total of 28 diagnostic genes that are implicated in DSD, highlighting the genetic spectrum of this disorder. Sequencing revealed 93 previously unreported DSD gene variants. Overall, we identified a likely genetic diagnosis in 43% of patients with 46,XY DSD. In patients with 46,XY disorders of androgen synthesis and action the genetic diagnosis rate reached 60%. Surprisingly, little difference in diagnostic rate was observed between singletons and trios. In many cases our findings are informative as to the likely cause of the DSD, which will facilitate clinical management.

Conclusions

Our massively parallel sequencing targeted DSD gene panel represents an economical means of improving the genetic diagnostic capability for patients affected by DSD. Implementation of this panel in a large cohort of patients has expanded our understanding of the underlying genetic etiology of DSD. The inclusion of research candidate genes also provides an invaluable resource for future identification of novel genes.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-016-1105-y) contains supplementary material, which is available to authorized users.

Abstract 3561: Whole transcriptome analysis of testicular germ cell tumors

Next generation sequencing of the whole transcriptome enables high resolution measurement of gene expression activity in different tissue and cell types. This methodology provides an in depth study of known transcripts and depending on the data analysis, allows identification of additional transcript types such as transcript variants, fusion transcripts, and small and long ncRNAs. In this study we performed RNA-Seq using the Ion Torrent sequencing platform to compare the expression profile of testicular germ cell tumors (seminoma type, n=3) and normal testis (n=3). Using Partek Flow and Star or TopHat aligners, we aligned the reads to the human genome and mapped sequences to the RefSeq database. We identified a large number of genes that were up and down regulated with high degree of significance p&lt;0.01, &gt;2X FC). These included genes related to testicular tissue type, stem cell pleuripotency (NANOG; POU5F1) and proliferation (KRAS, CCND2). In addition, a number of differentially expressed noncoding RNAs were identified (SNORD12B, XIST). The method was validated on a small set of genes (&gt;20) using qPCR (TaqMan Assays). We used the Open Array platform to quantitatively screen a larger number of differentially expressed genes (224) across a number of different testicular germ cell tumor types (non-seminoma).

Citation Format: Lovorka Degoricija, Kathy Y. Lee, Sunali Patel, Shirley Chu, Ad J.M. Gillis, Martin Rijlaarsdam, Lambert C.J. Dorssers, Leendert Looijenga. Whole transcriptome analysis of testicular germ cell tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3561. doi:10.1158/1538-7445.AM2014-3561

Cancer stem cells, pluripotency, and cellular heterogeneity: a WNTer perspective

Cancer stem cells (CSCs) are thought to represent the "beating heart" of malignant growth as they continuously fuel tumors through their ability to self-renew and differentiate. Moreover, they are also believed to underlie malignant behavior, local invasion, and metastasis in distal organ sites upon reversible epithelial-to-mesenchymal transitions (EMTs). Nevertheless, the CSC concept has been the object of controversy, mainly due to the absence of robust operational definitions and to the lack of consistency in the use of the often incorrect nomenclature employed to refer to these cells. Notwithstanding the controversies, it is now generally accepted that primary cancers are organized in hierarchical fashion with neoplastic stem-like cells able to give rise to new CSCs and to more committed malignant cells. Notably, these hierarchical structures are not unidirectional, but are rather characterized by a more dynamic equilibrium where stem-like and more committed cancer cells transit from one meta-state to the other partly because of cues from the microenvironment (niche), but also because of intrinsic and yet incompletely understood characteristics in the activation/silencing of specific signal transduction pathways. Here, we will focus on the Wnt/β-catenin signaling pathway as one of the major regulator of stemness in homeostasis and cancer, and on germ cell tumors as the type of malignancy that most closely mimics normal embryonic development and as such serve as a unique model to study the role of stem cells in neoplasia.

Identification of lineage-uncommitted, long-lived, label-retaining cells in healthy human esophagus and stomach, and in metaplastic esophagus

BACKGROUND & AIMS

The existence of slowly cycling, adult stem cells has been challenged by the identification of actively cycling cells. We investigated the existence of uncommitted, slowly cycling cells by tracking 5-iodo-2'-deoxyuridine (IdU) label-retaining cells (LRCs) in normal esophagus, Barrett's esophagus (BE), esophageal dysplasia, adenocarcinoma, and healthy stomach tissues from patients.

METHODS

Four patients (3 undergoing esophagectomy, 1 undergoing esophageal endoscopic mucosal resection for dysplasia and an esophagectomy for esophageal adenocarcinoma) received intravenous infusion of IdU (200 mg/m(2) body surface area; maximum dose, 400 mg) over a 30-minute period; the IdU had a circulation half-life of 8 hours. Tissues were collected at 7, 11, 29, and 67 days after infusion, from regions of healthy esophagus, BE, dysplasia, adenocarcinoma, and healthy stomach; they were analyzed by in situ hybridization, flow cytometry, and immunohistochemical analyses.

RESULTS

No LRCs were found in dysplasias or adenocarcinomas, but there were significant numbers of LRCs in the base of glands from BE tissue, in the papillae of the basal layer of the esophageal squamous epithelium, and in the neck/isthmus region of healthy stomach. These cells cycled slowly because IdU was retained for at least 67 days and co-labeling with Ki-67 was infrequent. In glands from BE tissues, most cells did not express defensin-5, Muc-2, or chromogranin A, indicating that they were not lineage committed. Some cells labeled for endocrine markers and IdU at 67 days; these cells represented a small population (<0.1%) of epithelial cells at this time point. The epithelial turnover time of the healthy esophageal mucosa was approximately 11 days (twice that of the intestine).

CONCLUSIONS

LRCs of human esophagus and stomach have many features of stem cells (long lived, slow cycling, uncommitted, and multipotent), and can be found in a recognized stem cell niche. Further analyses of these cells, in healthy and metaplastic epithelia, is required.

Disorders of sex development: summaries of long-term outcome studies

Existing outcomes for DSD individuals are inadequate because reports are based upon information collected retrospectively. This paper is presented to review existing data emphasizing information needed to lead to better future care, is based on presentations and discussions at a multi-disciplinary meeting on DSD held in Annecy in 2012, and is not intended to define the present status of management of each of the various DSD diagnoses. Rather it is intended to provide information needed to do studies regarding outcome data from the treatment of children with DSD by providing a summary of recommendations of 'patient-centered' topics that need investigation. The hope is that by being concerned with what is not known, new protocols will be developed for improving both early management and transition to adult life.

Review of recent outcome data of disorders of sex development (DSD): emphasis on surgical and sexual outcomes

This paper is a review of some of the recent publications regarding outcome of DSD patients, with an emphasis upon surgical and sexual outcomes. Currently available outcome studies of patients with DSDs have limitations because of multiple factors, including lack of representative patient sampling, and lack of adequate information concerning both medical and surgical care, and psychological, social and family support. The most frequent reports involve females with 21-α-hydroxylase deficiency congenital adrenal hyperplasia (CAH). This most common form of DSD, if one excludes hypospadias and cryptorchidism, is an excellent example of a form of DSD in which all aspects of outcome, regarding surgery, sexual functionality and sensitivity, psychological input and endocrine hormonal therapy, carry a major role. The goals of therapy include a surgical outcome with a good cosmetic appearance and functionality with potential for sexual intercourse with sufficient sensitivity for satisfactory responsiveness. Endocrine replacement therapy should provide a normal adrenal hormonal milieu, while sex steroid therapy may be indicated. Psychological care should be provided from birth with gradual transition primarily to the patient, including basic counseling with full disclosure, although adjustment depends upon the patient's personality and parents' abilities and acceptance. Among forms of DSD involving gonadal insufficiency, hormonal replacement therapy should provide physiologic levels. Among females, estrogen therapy enhances healing after feminizing surgery and is required from puberty throughout adult life to maintain femininity, sexual organs and bone health, and enhance gender and sexuality. Among males, appropriate testosterone therapy maintains stamina, muscle tone, bone health, libido, sexual potency and general well-being, while benefit for healing after genital surgery is unclear. Further, outcome is clearly related to predominant cultural factors. Outcome studies should include evaluation of all of these factors.

Requirements for a multicentric multidisciplinary registry on patients with disorders of sex development

Disorders of Sexual Development (DSDs) are a group of rare to very rare congenital anomalies of the genito-urinary tract of genetic and endocrine causes. Recently, an international database I-DSD was successfully implemented to register patients with DSD and to provide the basis for epidemiologic, genetic, and clinical research. This tool needs to be adjusted and supplemented with additional modules in order to better assess the anatomical basis of DSD as well as to monitor risk factors such as gonadal histology. A proposal for the additional information to be obtained is discussed.

Role of DNA methylation and methyl-DNA binding proteins in the repression of 5-lipoxygenase promoter activity

Human 5-lipoxygenase (5-LO) is the key enzyme in the formation of inflammatory leukotrienes. 5-LO gene expression is mainly restricted to B cells and cells of myeloid origin. It is known that basal 5-lipoxygenase promoter activity is regulated by DNA methylation. In this study we investigated the impact of the DNA methylation status of the 5-LO promoter on its activity and the role of methyl DNA binding proteins (MBDs) in transcriptional silencing of the 5-LO promoter. Using ChIP assays, we found that the methyl-DNA binding proteins MBD1, MBD2 and MeCP2 bind to the methylated 5-LO core promoter in U937 cells. Knock down of each of the MBDs upregulates 5-LO mRNA expression in U937 cells indicating that these proteins are involved in silencing of the 5-LO gene. In reporter gene assays with in vitro methylated 5-LO promoter constructs, the extent of 5-LO promoter methylation inversely correlated with its activity. Furthermore, we found that MBD1 overexpression repressed 5-LO promoter activity when the CpG sites at the Sp1 binding site close to the transcriptional start site (GC4) were methylated. Gel shift data indicate that recruitment of Sp1 to this binding site is prevented by methylation.

The distribution and behavior of extragonadal primordial germ cells in Bax mutant mice suggest a novel origin for sacrococcygeal germ cell tumors

In the mouse, germ cells that do not reach the genital ridges rapidly die by a wave of apoptosis that requires the pro-apoptotic protein Bax. In Bax-null embryos, large numbers of ectopic (extragonadal) germ cells fail to die. We have studied the fates of these, in an effort to understand the etiology of human extragonadal germ cell tumors, which are thought to arise from ectopic germ cells. We find that ectopic germ cells in which apoptosis is blocked form a heterogeneous population, which partially differentiates along the gonocyte pathway to different extents in different regions of the embryo, and in the two genders. In particular, a previously undescribed population of ectopic germ cells was identified in the tail. These germ cells retained primitive markers for longer than ectopic germ cells in other regions, and represent a possible origin for sacrococcygeal type I extragonadal germ cell tumors found in neonates and infants. This hypothesis is supported, but not proved, by the finding of cells expressing the germ cell marker Oct4 associated with a coccygeal germ cell tumor in a human infant.

Patterns of somatic mutation in human cancer genomes

Cancers arise owing to mutations in a subset of genes that confer growth advantage. The availability of the human genome sequence led us to propose that systematic resequencing of cancer genomes for mutations would lead to the discovery of many additional cancer genes. Here we report more than 1,000 somatic mutations found in 274 megabases (Mb) of DNA corresponding to the coding exons of 518 protein kinase genes in 210 diverse human cancers. There was substantial variation in the number and pattern of mutations in individual cancers reflecting different exposures, DNA repair defects and cellular origins. Most somatic mutations are likely to be 'passengers' that do not contribute to oncogenesis. However, there was evidence for 'driver' mutations contributing to the development of the cancers studied in approximately 120 genes. Systematic sequencing of cancer genomes therefore reveals the evolutionary diversity of cancers and implicates a larger repertoire of cancer genes than previously anticipated.

Defining minimum genomic regions of imbalance involved in testicular germ cell tumors of adolescents and adults through genome wide microarray analysis of cDNA clones

Identifying changes in DNA copy number can pinpoint genes that may be involved in tumor development. Here we have defined the smallest overlapping regions of imbalance (SORI) in testicular germ cell tumors other than the 12p region, which has been previously investigated. Definition of the regions was achieved through comparative genomic hybridization (CGH) analysis of a 4559 cDNA clone microarray. A total of 14 SORI were identified, which involved at least five of the 11 samples analysed. Many of these refined regions were previously reported using chromosomal or allelic imbalance studies. The SORI included gain of material from the regions 4q12, 17q21.3, 22q11.23 and Xq22, and loss from 5q33, 11q12.1, 16q22.3 and 22q11. Comparison with parallel chromosomal CGH data supported involvement of most regions. The various SORI span between one and 20 genes and highlight potential oncogenes/tumor suppressor genes to be investigated further.

Identification of recurrent chromosomal aberrations in germ cell tumors of neonates and infants using genomewide array-based comparative genomic hybridization

Human germ cell tumors (GCTs) of neonates and infants comprise a heterogeneous group of neoplasms, including teratomas and yolk sac tumors with distinct clinical and epidemiologic features. As yet, little is known about the cytogenetic constitution of these tumors. We applied the recently developed genomewide array-based comparative genomic hybridization (array CGH) technology to 24 GCTs derived from patients under the age of 5 years. In addition, we included seven tumors derived from children and adolescents older than 5 years. In the series from those under the age of 5 years, most teratomas displayed normal profiles, except for some minor recurrent aberrations. In contrast, the yolk sac tumors displayed recurrent losses of 1p35-pter and gains of 3p21-pter and of 20q13. In the GCTs of patients older than 5 years, the main recurrent anomalies included gains of 12p and of whole chromosomes 7 and 8. In addition, gains of the 1q32-qter region and losses of the 6q24-qter and 18q21-qter regions were frequent in GCTs of varied histology, independent of age. We concluded that array CGH is a highly suitable method for identifying recurrent chromosomal anomalies in GCTs of neonates and infants. The recurrent anomalies observed point to chromosomal regions that may harbor novel diagnostic/prognostic identifiers and genes relevant to the development of these neoplasms.

Rectal adenocarcinoma with choriocarcinomatous differentiation: Clinical and genetic aspects

Nongestational choriocarcinomas are rare tumors. In the gastrointestinal tract, they are characterized by a biphasic tumor growth with separated areas of adenocarcinomatous and choriocarcinomatous differentiation. We here report a case of a combined adenocarcinoma-choriocarcinoma of the rectum. The tumor showed an aggressive clinical behavior with metastasis to the liver and lungs. A transient partial remission was achieved after 4 cycles of cisplatinum, etoposide, and ifosfamide chemotherapy, with normalization of serum beta-human chorionic gonadotropin levels. At this time, viable residual choriocarcinoma cells were found in surgically resected lung metastasis. The patient succumbed 8 months after initial diagnosis to a rapid abdominal relapse. We used comparative genomic hybridization (CGH) and fluorescence in situ hybridization to elucidate the genetic relationship of adenocarcinoma and choriocarcinoma in this neoplasm. We found genetic changes characteristic for colorectal adenocarcinomas, a loss of chromosomal regions 8p21-pter as well as 18q21-pter, and a gain of 5p and 20q, in both tumor parts. This provides evidence for the common origin of both components. A differential pattern of additional genetic changes suggests a clonal evolution from a common ancestor cell. In contrast to findings from a comparative study on a choriocarcinoma of the renal pelvis, we did not find an amplification of the germ cell cancer-associated chromosomal region 12p11.2-p12.1 in the areas of choriocarcinoma but found instead a loss of Xp11.3-pter. To our knowledge, this is the first report of a CGH comparison of the adenocarcinomatous and choriocarcinomatous tumor parts in a nongestational choriocarcinoma of the gastrointestinal tract.

A novel case of infantile sacral teratoma and a constitutional t(12;15)(q13;q25) pat

Cytogenetic analysis of peripheral lymphocytes of an infantile patient with a sacral teratoma revealed a constitutional translocation (12;15)(q13;q25) pat. The same translocation was found in four additional relatives. Loss of heterozygosity analysis of the patient's tumor material showed retention of both translocation-derived chromosomes. Since allelic loss in the 12q13 region has been observed in germ cell tumors, we hypothesize that disregulation of genes located at or near the 12q13 breakpoint may be related to the development of this sacral teratoma. As a first step towards the identification of these genes, a 12q13 genomic contig that spans the breakpoint has been constructed.

Reactivity of germ cell maturation stage-specific markers in spermatocytic seminoma: diagnostic and etiological implications

It is generally accepted that testicular seminomas and spermatocytic seminomas have separate pathogeneses, although the origin of these two types of germ cell tumors of the adult testis remains a matter of debate. Although an embryonic germ cell origin seems to be most likely for seminomas, a spermatogonia-spermatocyte origin has been suggested for spermatocytic seminoma. To shed more light on the etiology of spermatocytic seminomas, we undertook an immunohistochemical and molecular approach using SCP1 (synaptonemal complex protein 1), SSX (synovial sarcoma on X chromosome), and XPA (xeroderma pigmentosum type A) as targets. Although a stage-specific expression pattern has been reported for SCP1 and SSX in normal spermatogenesis, we demonstrate here that it also exists for XPA. In fact, immunohistochemistry shows that the proteins of SCP1 and XPA are specifically present in the stage of primary and pachytene spermatocytes. In contrast, SSX was found in spermatogonia and primary spermatocytes, as well as in germ cells, from at least the 17th week of intrauterine development onward. Although no protein encoded by any of these genes was detected in tumor cells of a series of testicular seminomas, all tested spermatocytic seminomas were positive, in agreement with expression analysis. These data support the model that seminomas originate from an embryonic germ cell, and they imply that the cell of origin of spermatocytic seminomas is at least capable of maturing to the stage of spermatogonia-pachytene spermatocyte.

Comparative genomic and in situ hybridization of germ cell tumors of the infantile testis

Chromosomal information on germ cell tumors of the infantile testis, ie, teratomas and yolk sac tumors, is limited and controversial. We studied two teratomas and four yolk sac tumors using comparative genomic hybridization (CGH) and in situ hybridization. No chromosomal anomalies were found in the teratomas by any of the methods, not even after CGH on microdissected tumor cells. All yolk sac tumors showed aneuploidy, loss of parts of 4q and 6q, and gain of parts of 20q. Underrepresentation of parts of 8q and overrepresentation of parts of 3p, 9q, 12p, 17, 19q, and 22 were detected in most cases. In addition, one recurrent yolk sac tumor after a sacral teratoma was studied, showing a highly similar pattern of imbalances. While CGH demonstrated loss of 1p36 in one testicular yolk sac tumor, in situ hybridization revealed loss of this region in all yolk sac tumors. High-level amplification of the 12q13-q14 region was found in one yolk sac tumor. MDM2, of which the encoding gene maps to this chromosomal region, was found in all cases using immunohistochemistry, whereas no p53 could be detected. Accordingly, no mutations within exons 5 to 8 of the p53 gene were observed. These data prove the absence of gross chromosomal aberrations in teratomas of the infantile testis and show a characteristic pattern of gains and losses in the yolk sac tumors. Besides confirmation of previously found anomalies, recurrent losses of 1p21-31 and 4q23-33 and gains of 9q34 and 12p12-13 have not been reported before. While genetic inactivation of p53 seems unimportant in the pathogenesis of these tumors, biochemical inactivation by MDM2 might be involved. These data support the existence of three entities of germ cell tumors of the human testis: teratomas and yolk sac tumors of infants, seminomas and nonseminomas of adolescents and young adults, and spermatocytic seminomas of the elderly, each with its own specific pathogenesis.

Chromosomal gains and losses in testicular germ cell tumors of adolescents and adults investigated by a modified comparative genomic hybridization approach

Testicular germ cell tumors of adolescents and adults, both seminomas (SE) and nonseminomas (NS), are aneuploid, and classical karyotyping demonstrated a specific pattern of gains and losses. More recently, these data have been supported by in situ hybridization and comparative genomic hybridization (CGH) on a limited number of samples. Interpretation of CGH results is complicated by the intermediate ploidy of these tumors (3-4 n for SE and 2-3 n for NS). To circumvent this problem, this particular study was undertaken. CGH was performed on 8 SE and 10 NS, after which two single chromosome normalizations were applied, one for chromosome 4 (found to be associated to the lower ploidy level of the tumor) and one for chromosome 8 (found to be associated with the higher ploidy level of the tumor) Using this modified CGH interpretation method, chromosomal regions with a similar copy number of chromosome 4 and 8 were identified as belonging to the lower and higher ploidy level, and the regions below chromosome 4 and above chromosome 8 were identified as lost or gained outside the ploidy range of the tumor, respectively. Our results are in accordance with earlier findings, however they add novel data, including comparison of SE and NS. This approach reveals relevant information about the chromosomal constitution of testicular germ cell tumors, leading to a better understanding of the pathogenesis of these tumors.

Molecular cytogenetics of human germ cell tumours: i(12p) and related chromosomal anomalies

Human testicular germ cell tumours (TGCTs) comprise a heterogeneous group of solid neoplasms. These tumours are characterized by a highly specific chromosomal anomaly, i.e. an isochromosome of the short arm of chromosome 12. At present, this i(12p) chromosome has been observed in about 80% of TGCTs. Also in dysgerminomas of the ovary and in some extragonadal germ cell tumours i(12p) has been observed. In the remaining so-called i(12p)-negative tumours other cytogenetic abnormalities can be found. In addition, TGCTs are usually highly aneuploid. The exact nature and role of these different anomalies in tumour development are as yet undefined. Here we present a molecular cytogenetic analysis of a diverse group of gonadal and extragonadal germ cell tumours. Our results indicate that all tumours examined exhibit anomalies involving 12p [i(12p) and/or others], resulting in a distinct overrepresentation of short arm sequences. Thus, we argue that the occurrence of 12p abnormalities may be a characteristic of both i(12p)-positive and -negative TGCTs and that these abnormalities may, through similar mechanisms, contribute to the process of TGCT development. This notion is substantiated by our finding that in all cases the supernumerary 12p sequences are of uniparental origin.

Verification of isochromosome 12p and identification of other chromosome 12 aberrations in gonadal and extragonadal human germ cell tumors by bicolor double fluorescence in situ hybridization

A diverse group of gonadal and extragonadal human germ cell tumors (GCT) and GCT-derived cell lines was examined for the presence of an i(12p) marker chromosome and/or other abnormalities involving chromosome 12, especially 12p, by bicolor double fluorescence in situ hybridization (FISH). For this purpose three probes, pBS-12, M28, and p alpha 12H8, were used, allowing specific identification of the entire chromosome 12, its short arm, and its pericentromeric region, respectively. The presence of one or more copies of a genuine i(12p) chromosome could be demonstrated in three GCT of the testis, in one ovarian GCT, in one dysgenetic GCT, and in one extragonadal intracranial GCT. Moreover, additional aberrations involving chromosome 12 were shown to be present not only in i(12p) minus but also in i(12p) positive GCT. These data suggest that the occurrence of such aberrations may be a common, although less clearly perceptible and frequent, phenomenon in human GCT.

Pallister-Killian syndrome: characterization of the isochromosome 12p by fluorescent in situ hybridization

The isochromosome 12p (i(12p)) in fibroblasts of 3 patients with Pallister-Killian syndrome and one decreased prematurely born neonate, was characterized by fluorescent in situ hybridization (FISH) using chromosome 12-specific DNA probes. FISH is a useful technique for rapid and reliable detection and characterization of the i(12p) chromosome in Pallister-Killian patients. Detection was possible also in interphase cells. In addition, the in vitro selection against i(12p) cells at different passages in fibroblast cultures of two patients was monitored.