Disruption of imprinted genes at chromosome region 11p15.5 in paediatric rhabdomyosarcoma

Fusion of EWSR1 with the DUX4 facioscapulohumeral muscular dystrophy region resulting from t(4;22)(q35;q12) in a case of embryonal rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common pediatric soft tissue sarcoma and rarely occurs in adults. There are six main subtypes, each histologically, clinically, and cytogenetically distinct. Embryonal RMS is characterized by chromosomal gains, usually not associated with any consistent structural anomaly. We describe here a case of embryonal RMS in a 19-year-old female patient. The conventional cytogenetic analysis showed a t(4;22)(q35;q12) translocation as the sole cytogenetic change. Complementary fluorescence in situ hybridization analysis showed that the translocation breakpoints were located in the EWSR1 gene at 22q12 and the region of the DUX4 and FSHMD1A at 4q35. This constitutes a novel example of the high frequency of EWSR1 rearrangements in various types of sarcomas as well as of its ability to fuse with a large variety of partner genes. Because DUX4 is involved in myogenic differentiation and cell-cycle control, the striated muscle differentiation observed in the present case might be a direct consequence of the alteration of the DUX4 region generated by the t(4;22). The involvement of the DUX4 region might represent the genetic hallmark of a novel subclass of small round cell tumors.

Molecular and cellular biology of rhabdomyosarcoma

Rhabdomyosarcoma is a group of soft-tissue sarcomas that share features of skeletal myogenesis, but show extensive heterogeneity in histology, age and site of onset, and prognosis. This review matches recent molecular data with biological features of rhabdomyosarcoma. Alterations in molecular pathways, animal models, cell of origin and potential new therapeutic targets are discussed.

Hypoglycemia from IGF2 overexpression associated with activation of fetal promoters and loss of imprinting in a metastatic hemangiopericytoma

CONTEXT

The mechanism of IGF2 overexpression in non-islet-cell tumor hypoglycemia is not understood.

OBJECTIVE

We investigated the imprinting control and promoter usage for IGF2 expression to identify a mechanism for increased IGF-II production in non-islet-cell tumor hypoglycemia.

PATIENT AND METHODS

A patient with metastatic hemangiopericytoma was studied. Tissue from the original hemangiopericytoma, metastatic tumor, and uninvolved liver was analyzed for IGF-II immunohistochemistry. IGF2, a paternally imprinted gene, shares a control region with maternally imprinted H19, a putative tumor suppressor. IGF-II and H19 mRNA expression was compared in metastatic tumor and uninvolved liver by quantitative RT-PCR. Imprinting of IGF2/H19 genes and IGF2 promoter usage in metastatic tumor was investigated by RT-PCR and sequence analysis, and the methylation pattern in the IGF2/H19 imprinting control region was analyzed.

RESULTS

IGF-II protein expression was increased in metastatic tumor vs. uninvolved liver and original tumor. In the metastatic tumor, IGF-II mRNA was increased 60-fold, but H19 mRNA was comparable to uninvolved liver; loss of imprinting of IGF2, but not H19, was identified; no major change in methylation of the IGF2/H19 imprinting control regions was observed; and transcripts from four different IGF2 promoters were detected, compared to two in uninvolved liver.

CONCLUSIONS

IGF-2 overexpression, newly acquired in the metastatic tumor, was associated with loss of IGF2 gene imprinting and different promoter usage. The imprinting control mechanism governing the IGF2/H19 locus was intact, as evidenced by normal levels of H19, maintenance of H19 imprinting, and no major change in methylation of the imprinting control regions.

Molecular classification of rhabdomyosarcoma--genotypic and phenotypic determinants of diagnosis: a report from the Children's Oncology Group

Rhabdomyosarcoma (RMS) in children occurs as two major histological subtypes, embryonal (ERMS) and alveolar (ARMS). ERMS is associated with an 11p15.5 loss of heterozygosity (LOH) and may be confused with nonmyogenic, non-RMS soft tissue sarcomas. ARMS expresses the product of a genomic translocation that fuses FOXO1 (FKHR) with either PAX3 or PAX7 (P-F); however, at least 25% of cases lack these translocations. Here, we describe a genomic-based classification scheme that is derived from the combined gene expression profiling and LOH analysis of 160 cases of RMS and non-RMS soft tissue sarcomas that is at variance with conventional histopathological schemes. We found that gene expression profiles and patterns of LOH of ARMS cases lacking P-F translocations are indistinguishable from conventional ERMS cases. A subset of tumors that has been histologically classified as RMS lack myogenic gene expression. However, classification based on gene expression is possible using as few as five genes with an estimated error rate of less than 5%. Using immunohistochemistry, we characterized two markers, HMGA2 and TFAP2ss, which facilitate the differential diagnoses of ERMS and P-F RMS, respectively, using clinical material. These objectively derived molecular classes are based solely on genomic analysis at the time of diagnosis and are highly reproducible. Adoption of these molecular criteria may offer a more clinically relevant diagnostic scheme, thus potentially improving patient management and therapeutic RMS outcomes.

Immunohistochemical expression of p57 in placental vascular proliferative disorders of preterm and term placentas

P57 protein is implicated in some human imprinting disorders such as hydatiform mole and Beckwith-Wiedemann syndrome (BWS), both characterized by mesenchymal and vascular placental abnormalities. We investigated p57 immunohistochemical expression in placental vascular proliferative disorders of preterm and term placentas, including chorangiosis (n = 5), chorangiomatosis (n = 2), chorangiomas (n = 7), umbilical cord angioma (n = 1), and placental mesenchymal dysplasia (PMD) (n = 7). P57 was expressed in decidua, cytotrophoblast, intermediate trophoblast and stromal cells of normal terminal, intermediate and stem villi, umbilical cord, chorangiosis, chorangiomatosis, and chorangiomas. In contrast, there was a loss of p57 expression in stromal cells of dysplastic stem villi in all cases of PMD regardless of whether associated with BWS or not. P57 seems to be involved in the pathogenesis of a subset of placental vascular proliferative disorders in preterm and term placentas, such as PMD. The loss of p57 expression in PMD could be of diagnostic value in helping to distinguish this rare placental lesion from its mimickers.

The estrogen receptor pathway in rhabdomyosarcoma: a role for estrogen receptor-beta in proliferation and response to the antiestrogen 4'OH-tamoxifen

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children. Highly malignant, RMS frequently fails to respond to conventional aggressive multimodal radiation, surgery, and chemotherapy treatment protocols that also cause significant sequelae in the growing child. Other tumors of mesenchymal origin, such as locally aggressive fibromatoses and desmoid tumors, have been successfully treated with a selective estrogen receptor (ER) modulator, tamoxifen. In an effort to identify new targets for RMS therapy, our group investigated the previously uncharacterized ER pathway in RMS cell culture and primary tumors. We detected ER isoform beta (ER beta), but not isoform alpha, RNA, and protein in five RMS cell lines. Immunohistochemical staining of primary RMS tumor sections confirmed high levels of ER beta but not ER alpha protein. RMS cell growth was dramatically inhibited in steroid-free conditions, and this growth inhibition was rescued with 17-beta-estradiol (E2) supplementation. Exposure of RMS cells to 4'OH-tamoxifen (4OHT) decreased cell viability and inhibited colony formation as detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and colony-forming assays. 4OHT also induced apoptotic signaling in RMS cells as detected by cleavage of caspase-3 and poly(ADP)ribose polymerase. This effect increased 3- to 8-fold in steroid-deprived conditions but was rescued by supplementation with E2. Immunofluorescence studies detected a change in the subcellular localization of ER beta in response to 4OHT. Together, these data suggest an active ER beta-mediated signal transduction pathway in RMS. The ability of 4OHT to induce apoptotic signaling and disrupt estradiol-mediated proliferation provides a rationale to explore a role for selective ER modulators in the treatment of RMS.

PAX3-FOXO1 controls expression of the p57Kip2 cell-cycle regulator through degradation of EGR1

The chimeric protein PAX3-FOXO1, resulting from a translocation between chromosomes 2 and 13, is the most common genetic aberration in the alveolar subtype of the human skeletal muscle tumor, rhabdomyosarcoma. To understand how PAX3-FOXO1 contributes to tumor development, we isolated and characterized muscle cells from transgenic mice expressing PAX3-FOXO1 under control of the PAX3 promoter. We demonstrate that these myoblasts are unable to complete myogenic differentiation because of an inability to up-regulate p57Kip2 transcription. This defect is caused by reduced levels of the EGR1 transcriptional activator resulting from a direct, destabilizing interaction with PAX3-FOXO1. Neither PAX3 nor FOXO1 share the ability to regulate p57Kip2 transcription. Thus, the breakage and fusion of the genes encoding these transcription factors creates a unique chimeric protein that controls a key cell-cycle and -differentiation regulator.

Rhabdomyosarcoma, Wilms tumor, and deletion of the patched gene in Gorlin syndrome

BACKGROUND

A 5-year-old year girl with a medical history of mental retardation, physical abnormalities and a known interstitial deletion of chromosome 9q22-q32 presented with a palpable suprapubic mass. During ultrasound investigation, a left renal mass was also detected. The patient underwent surgical removal of both neoplasms, which were diagnosed as a rhabdomyosarcoma and a Wilms tumor. Seven years later, she presented with macroglossia and a benign mandibular cyst.

INVESTIGATIONS

Physical examination, karyotyping, abdominal and pelvic ultrasound, brain CT scan, anatomic pathology analysis with immunohistochemistry, and typing of polymorphic markers in the patched (PTCH) gene region.

DIAGNOSIS

Gorlin syndrome with synchronous rhabdomyosarcoma and Wilms tumor.

MANAGEMENT

Left nephrectomy, excision of paravesical tumor, excision of mandibular cysts, chemotherapy, and radiotherapy.

Loss of imprinting and promoter usage of the IGF2 in laryngeal squamous cell carcinoma

The gene for insulin-like growth factor two, IGF2 is maternally imprinted. Fifteen heterozygous samples were analyzed for the IGF2 imprinting status and promoter usage. IGF2 LOI was detected in four non-tumorous tissues and in six laryngeal squamous cell carcinoma (LSCC) tumors. There was no clear pattern of specific promoter activity in LSCC tumors and the adjacent normal tissues. P1 promoter usage was active in eight LSCCs, among them four with LOI. As it was activated in four tumors with maintenance of imprinting (MOI) and four non-tumors, we concluded that P1 promoter is not exclusively connected with IGF2 LOI in LSCC.

p21WAF1 expression induced by MEK/ERK pathway activation or inhibition correlates with growth arrest, myogenic differentiation and onco-phenotype reversal in rhabdomyosarcoma cells

Background

p21^WAF1, implicated in the cell cycle control of both normal and malignant cells, can be induced by p53-dependent and independent mechanisms. In some cells, MEKs/ERKs regulate p21^WAF1 transcriptionally, while in others they also affect the post-transcriptional processes. In myogenic differentiation, p21^WAF1 expression is also controlled by the myogenic transcription factor MyoD. We have previously demonstrated that the embryonal rhabdomyosarcoma cell line undergoes growth arrest and myogenic differentiation following treatments with TPA and the MEK inhibitor U0126, which respectively activate and inhibit the ERK pathway.

In this paper we attempt to clarify the mechanism of ERK-mediated and ERK-independent growth arrest and myogenic differentiation of embryonal and alveolar rhabdomyosarcoma cell lines, particularly as regards the expression of the cell cycle inhibitor p21^WAF1.

Results

p21^WAF1 expression and growth arrest are induced in both embryonal (RD) and alveolar (RH30) rhabdomyosarcoma cell lines following TPA or MEK/ERK inhibitor (U0126) treatments, whereas myogenic differentiation is induced in RD cells alone. Furthermore, the TPA-mediated post-transcriptional mechanism of p21^WAF1-enhanced expression in RD cells is due to activation of the MEK/ERK pathway, as shown by transfections with constitutively active MEK1 or MEK2, which induces p21^WAF1 expression, and with ERK1 and ERK2 siRNA, which prevents p21^WAF1 expression. By contrast, U0126-mediated p21^WAF1 expression is controlled transcriptionally by the p38 pathway. Similarly, myogenin and MyoD expression is induced both by U0126 and TPA and is prevented by p38 inhibition. Although MyoD and myogenin depletion by siRNA prevents U0126-mediated p21^WAF1 expression, the over-expression of these two transcription factors is insufficient to induce p21^WAF1. These data suggest that the transcriptional mechanism of p21^WAF1 expression in RD cells is rescued when MEK/ERK inhibition relieves the functions of myogenic transcription factors. Notably, the forced expression of p21^WAF1 in RD cells causes growth arrest and the reversion of anchorage-independent growth.

Conclusion

Our data provide evidence of the key role played by the MEK/ERK pathway in the growth arrest of Rhabdomyosarcoma cells. The results of this study suggest that the targeting of MEK/ERKs to rescue p21^WAF1 expression and myogenic transcription factor functions leads to the reversal of the Rhabdomyosarcoma phenotype.

Expression Microarray Analysis and Oligo Array Comparative Genomic Hybridization of Acquired Gemcitabine Resistance in Mouse Colon Reveals Selection for Chromosomal Aberrations

Gemcitabine is a commonly used therapy for many solid tumors. Acquired resistance to this nucleoside analogue, however, diminishes the long-term effectiveness in a majority of patients. To better define the molecular background of gemcitabine resistance, a mouse colon tumor was selected during successive rounds of transplantation with continued treatment of gemcitabine. Expression microarray analysis was applied to determine which genes are consistently and highly overexpressed or underexpressed in the resistant versus the nonresistant tumor. For the statistical interpretation of the microarray data, a parametric model was implemented, which returns model-based differential gene expression (log-) ratios and their uncertainties. This defined a set of 13 genes, putatively responsible for the gemcitabine resistance in solid tumors. One of these, RRM1, was previously identified as an important marker for gemcitabine resistance in human cell lines. Five of the 13 genes, including RRM1, are located within a 3 Mb region at chromosome 7E1 of which four are highly overexpressed, suggesting a chromosomal amplification. Therefore, chromosomal copy number changes were measured, using oligo array comparative genomic hybridization. A narrow and high amplification area was identified on 7E1 that encompassed all five genes. In addition, reduced RNA expression of two other genes at 8E1 encoding COX4I1 and RPL13 could be explained by a decrease in chromosomal copy number on chromosome 8. In conclusion, the array comparative genomic hybridization biologically validates our statistical approach and shows that gemcitabine is capable to select for chromosomally aberrant tumor cells, where changed gene expression levels lead to drug resistance.

Upstream CpG island methylation of the PAX3 gene in human rhabdomyosarcomas

BACKGROUND

Adult tumors can be characterized by hypermethylation of CpG islands associated with 5'-upstream and coding regions of specific genes. This hypermethylation can also be part of the aging process. In contrast, much less is known about gene hypermethylation in childhood cancers, where methylation changes are not part of the aging process but likely represent developmental dysregulation. PAX3 is an important gene in muscle development and muscle-producing neoplasms such as rhabdomyosarcomas.

PROCEDURES

We examined the methylation status of a PAX3 5'-CpG island in rhabdomyosarcoma subtypes and in normal fetal skeletal muscle. PAX3 methylation was analyzed in 15 embryonal rhabdomyosarcomas, 12 alveolar rhabdomyosarcomas, and in six normal skeletal muscle samples, using semi-quantitative PCR analysis of DNA digested with methyl-sensitive restriction enzymes.

RESULTS

The CpG island in the upstream region of the human PAX3 gene was hypermethylated in the majority of ERMS examined (13 of 15 tumors, mean of 52% methylation), whereas most ARMS (9 of 12 tumors) and all normal muscle samples showed relative hypomethylation (both 18% mean methylation). Various CpG sites differ in contribution to overall PAX3 CpG island methylation, with methylation at a HaeII site being inversely correlated with PAX3 expression.

CONCLUSIONS

PAX3 CpG island methylation appears to distinguish embryonal subtype of rhabdomyosarcoma from alveolar, and methylation at certain sites within this CpG island is inversely correlated with PAX3 expression. In addition to exemplifying developmental dysregulation, methylation of PAX3 has potential in the development of an epigenetic profile for the diagnosis of rhabdomyosarcoma.

Nephroblastoma Arising in a Germ Cell Tumor of Testicular Origin

We report a nephroblastoma arising in a germ cell tumor of testicular origin occurring in a 22-year-old man. Orchiectomy demonstrated a malignant mixed germ cell tumor composed of mature and immature teratoma with nephroblastoma and rhabdomyosarcoma. Following chemotherapy, the patient developed supraclavicular and retroperitoneal lymphadenopathy. Excision demonstrated metastatic teratoma at both sites. No recurrence was noted with 21 months of additional follow-up. Using tissue microdissection and loss of heterozygosity analysis, we investigated the clonality of the mature teratoma, immature teratoma, nephroblastoma, and rhabdomyosarcoma components of the primary tumor and of the metastatic mature teratoma at the two separate distant sites. Nine microsatellite polymorphic makers were used to examine the pattern of allelic loss in both primary and metastatic tumors. Loss of heterozygosity was found in 4 DNA loci, and the same pattern of allelic loss was demonstrated at all 4 loci in all of the different components of the primary tumor and the metastatic mature teratomas, supporting the germ cell tumor origin of the nephroblastoma component. Loss of heterozygosity on chromosome 17p13 (TP53) was detected in metastatic mature teratoma, but not in the primary tumor. Loss of heterozygosity was observed at 11p13, the locus of WT1 inactivation in patients genetically predisposed to nephroblastoma, and this loss may be an important genetic mechanism in nephroblastomatous differentiation of germ cell tumors. These data support a common clonal origin for nephroblastoma and the other germ cell tumor components.

Genetic imbalances revealed by comparative genomic hybridization in osteosarcomas

Osteosarcomas are the most frequent bone sarcomas. The molecular chromosomal aberrations in osteosarcomas were analyzed by comparative genomic hybridization (CGH). We studied 47 frozen tumors (41 primary samples, 6 relapses) in osteosarcoma patients registered in the Cooperative Osteosarcoma Study (COSS) protocol. Genomic imbalances were detected in 40 of 41 primary tumors and 6 of 6 relapsed tumors. Gains were more frequent than losses (ratio of 1.3:1). The median number of changes was 16 and 12 in primary and relapsed osteosarcomas, respectively. The median number of aberrations in primary high-grade osteosarcomas (17.0) was significantly higher than in low- or intermediate-grade osteosarcoma subtypes (3.0) (p = 0.038). The most frequent gains included 8q, 1p21-p31 and 1q21-q24, and the most frequent losses were 10q, 5q and 13q. High-level gains were observed on 8q23-q24, 17p13 and 1q21-q24. A gain of 19p (p < 0.001) or loss of 9p (p = 0.027) was more frequent in poor responders than in good responders. Univariate analysis revealed that patients with primary metastases (p = 0.002), poor histologic responses (p = 0.005), high-level gains of 19p (p = 0.012) or losses of 13q14 (p = 0.042) had significantly lower event-free survival (EFS), whereas patients with a loss of 5q (p = 0.007) or a loss of 10q21-22 (p = 0.017) had significantly higher EFS than patients without these aberrations. Multivariate analysis demonstrated that primary metastasis, loss of 13q14 and loss of 5q were independent prognostic factors. The findings of our study seem to be useful for evaluating the prognosis of patients and may finally lead to treatment strategies based on genetic background of osteosarcoma.

Identification of a novel gene NCRMS on chromosome 12q21 with differential expression between rhabdomyosarcoma subtypes

Rhabdomyosarcoma (RMS) is a malignant soft tissue tumor showing varying degrees of skeletal muscle differentiation. Two major histologic subtypes exist, alveolar and embryonal, each with associated molecular genetic changes. We have used Representational Difference Analysis (RDA) to compare gene expression between the two RMS subtypes and have identified the novel gene NCRMS (non-coding RNA in RMS) that has increased expression in the alveolar subtype relative to the embryonal subtype. Multiple alternatively spliced forms of NCRMS were identified through library screening, RACE, and comparison to human expressed sequence tags (ESTs). Northern blot analysis indicated the transcript size to be 1.25 kb in alveolar RMS. There was no sequence homology to any of the known genes in GenBank, but extensive homology to ESTs from various species. Comparison to human genomic sequences identified at least 11 exons mapping to chromosomal region 12q21. Differential expression of NCRMS was noted between various tumor types. Since NCRMS RNA possesses limited potential for protein coding, yet with conserved sequences between different species, it is likely that NCRMS is a functional non-coding RNA. Known genes in its proximity include myogenic regulators Myf5 and Myf6, growth factor Igf1, and another potential differentially expressed gene (ATP2B1) in RMS isolated by RDA.

PAX3-FKHR induces morphological change and enhances cellular proliferation and invasion in rhabdomyosarcoma

Alveolar rhabdomyosarcoma (ARMS) is consistently associated with the characteristic translocations t(2;13)(q35;q14) and t(1;13)(p36;q14), which encode for the PAX3-FKHR and PAX7-FKHR fusion oncoproteins respectively. We have investigated the relationship between PAX3-FKHR expression and ARMS histogenesis in primary tumors and cell culture systems. In a blinded histological review of discrepant primary tumors in which there was PAX3-FKHR expression but embryonal histology, we found small areas of alveolar histology in 6 of 11 cases. This suggests that histology alone may under-represent the association between PAX3-FKHR and ARMS, and we investigated this link by examining the effect of ectopic PAX3-FKHR expression on RMS cells. Two cell lines, RD and HX170C, were stably transfected with a PAX3-FKHR expression construct. In cloned transfectants derived from both lines, PAX3-FKHR expression resulted in increased proliferative rate in vitro and promoted cell growth in the absence of added growth factors. Tumors that formed as xenografts in immunodeficient mice were faster growing, more locally invasive, and had a denser, more pleomorphic architecture than untransfected or empty vector transfected tumors. The characteristic clefts and alveolar spaces of ARMS, however, were not seen. In contrast, tumors grown as xenografts from individual clones derived from ARMS cell lines showed all of the classical morphological features of ARMS suggesting divergence in vivo from precursor cells propagated in culture.

Genetic and molecular abnormalities in tumors of the bone and soft tissues

BACKGROUND

Malignant transformation requires the accumulation of multiple genetic alterations such as chromosomal abnormalities, oncogene activation, loss of tumor suppressor genes, or abnormalities in genes that control DNA repair and genomic instability. Sarcomas are a heterogeneous group of malignant mesenchymal tumors of difficult histologic classification and strong genetic predisposition. This article provides a comprehensive review of the cytogenetic abnormalities observed in bone and soft-tissue tumors, emphasizing known downstream molecular changes that may play a role in oncogenesis.

METHODS

The database of the National Library of Medicine was searched for literature relating to genetic and molecular mechanisms in sarcomas in general and in each of the main tumor entities.

RESULTS

Recent techniques in chromosome analysis and molecular cytogenetics have improved our ability to characterize genetic changes in mesenchymal tumors. Some changes are so characteristic as to be virtually pathognomonic of particular histologic types, while others are complex, difficult to characterize, and of unknown relevance to pathogenesis. The implications to the cell of some of these abnormalities are now being recognized.

CONCLUSIONS

The study of sarcomas will benefit from the information derived from genetic studies and translational research. The human genome project and new methodologies, such as computer-based DNA microarray, may help in the histogenetic classification of sarcomas and in the identification of molecular targets for therapy.

Cytogenetic abnormalities in 42 rhabdomyosarcoma: a United Kingdom Cancer Cytogenetics Group Study

BACKGROUND

Rhabdomyosarcomas are the most common type of pediatric soft tissue sarcoma. The cytogenetic literature on RMS is biased towards the less common alveolar subtype (ARMS), which is frequently associated with specific translocations and the PAX3/7-FKHR fusion genes. Relatively few karyotypes are reported for the embryonal subtype (ERMS). The aim of this study was to further cytogenetic knowledge of RMS subtypes.

PROCEDURE

Representative examples of all karyotypes from UKCCG; member laboratories were reexamined and their histopathologies reviewed through the United Kingdom Children's Cancer Study (Group) (UKCCSG). Molecular evidence for the PAX3/7-FKHR fusion genes was available for five ERMS and seven ARMS cases and compiled with the karyotypes.

RESULTS

Clonal chro mosome aberrations were characterized for 25 ERMS and 17 ARMS cases. Thirty-six percent of the ERMS cases involved translocation breakpoints in the 1p11-q11 region. Ten of the seventeen cases of ARMS showed cytogenetic evidence for the t(2;13)(q35;q14), consistent with molecular data available from four of these. Two further ARMS cases revealed a PAX3-FKHR and a variant PAX7-FKHR fusion gene product that were not detected cytogenetically.

CONCLUSIONS

Many of the karyotypes from both subtypes were complex. The frequent involvement of the 1p11-1q11 region and gain of chromosomes 2, 8, 12, and 13 in ERMS may be functionally significant. There was no evidence for involvement of the PAX3/7-FKHR genes in ERMS, and cryptic involvement was found in some ARMS. There were no consistent chromosomal rearrangements associated with apparently translocation negative ARMS cases.