N-myc gene is amplified in alveolar rhabdomyosarcomas (RMS) but not in embryonal RMS

SMARCE1 promotes neuroblastoma tumorigenesis through assisting MYCN-mediated transcriptional activation

SMARCE1 gene, encoding a core subunit of SWI/SNF chromatin remodeling complex, is situated on chromosome 17q21-ter region that is frequently gained in neuroblastoma. However, its role in the tumorigenesis remains unknown. Here, we showed that high expression of SMARCE1 was associated with poor prognosis of patients with neuroblastoma, especially those with MYCN amplification. Knockdown of SMARCE1 reduced proliferation, colony formation, and tumorigenicity of neuroblastoma cells. Mechanistically, SMARCE1 directly interacted with MYCN, which was necessary for MYCN-mediated transcriptional activation of downstream target genes including PLK1, ODC1, and E2F2. Overexpression of PLK1, ODC1 or E2F2 significantly reversed the inhibiting effect of SMARCE1 knockdown on the proliferation, colony formation, and tumorigenicity of MYCN-amplified neuroblastoma cells. Moreover, we revealed that MYCN directly regulated SMARCE1 transcription through binding to a non-canonical E-box of SMARCE1 promoter, thus enhancing SMARCE1-MYCN cooperativity. These findings establish SMARCE1 is a critical oncogenic factor in neuroblastoma and provide a new potential target for treatment of neuroblastoma with 17q21-ter gain and MYCN amplification.

Fusion of the Paired Box 3 (PAX3) and Myocardin (MYOCD) Genes in Pediatric Rhabdomyosarcoma

BACKGROUND/AIM

Fusions of the paired box 3 gene (PAX3 in 2q36) with different partners have been reported in rhabdomyosarcomas and biphenotypic sinonasal sarcomas. We herein report the myocardin (MYOCD on 17p12) gene as a novel PAX3-fusion partner in a pediatric tumor with adverse clinical outcome.

MATERIALS AND METHODS

A rhabdomyo-sarcoma found in a 10-year-old girl was studied using a range of genetic methodologies.

RESULTS

The karyotype of the tumor cells was 48,XX,add(2)(q11),+del(2)(q35),add(3)(q?25),-7, del(8)(p 21),-15, add(17)(p 11), + 20, +der(?) t(?; 15) (?;q15),+mar[8]/46,XX[2]. Fluorescence in situ hybridization detected PAX3 rearrangement whereas array comparative genomic hybridization revealed genomic imbalances affecting hundreds of genes, including MYCN, MYC, FOXO3, and the tumor suppressor gene TP53. A PAX3-MYOCD fusion transcript was found by RNA sequencing and confirmed by Sanger sequencing.

CONCLUSION

The investigated rhabdomyosarcoma carried a novel PAX3-MYOCD fusion gene and extensive additional aberrations affecting the allelic balance of many genes, among them TP53 and members of MYC and FOXO families of transcription factors.

The Bromodomain BET Inhibitor JQ1 Suppresses Tumor Angiogenesis in Models of Childhood Sarcoma

The bromodomain and extra-terminal domain inhibitor JQ1 has marked antitumor activity against several hematologic malignancies as well as solid tumor models. Here, we investigated its activity in vitro and in vivo against models of childhood rhabdomyosarcoma and Ewing sarcoma. In vitro, JQ1 (but not the inactive enantiomer JQ1R) inhibited cell proliferation and increased G1 fraction of cells, although there was no correlation between cell line sensitivity and suppression of c-MYC or MYCN. In vivo, xenografts showed significant inhibition of growth during the period of treatment, and rapid regrowth after treatment was stopped, activity typical of antiangiogenic agents. Furthermore, xenografts derived from cell lines intrinsically resistant or sensitive to JQ1 in vitro had similar sensitivity in vivo as xenografts. Further investigation showed that JQ1 reduced tumor vascularization. This was secondary to both drug-induced downregulation of tumor-derived growth factors and direct effects of JQ1 on vascular elements. JQ1 suppressed VEGF-stimulated vascularization of Matrigel plugs in mice, and in vitro suppressed differentiation, proliferation, and invasion of human umbilical cord vascular endothelial cells (HUVEC). In HUVECs, JQ1 partially suppressed c-MYC levels, but dramatically reduced AP-1 levels and activity through suppression of the AP-1-associated protein FOSL1. Our data suggest that the antitumor activity of JQ1 in these sarcoma models is largely a consequence of its antiangiogenic activity. Mol Cancer Ther; 15(5); 1018-28. ©2016 AACR.

The mTOR pathway negatively controls ATM by up-regulating miRNAs

The ataxia telangiectasia mutated (ATM) checkpoint is the central surveillance system that maintains genome integrity. We found that in the context of childhood sarcoma, mammalian target of rapamycin (mTOR) signaling suppresses ATM by up-regulating miRNAs targeting ATM. Pharmacological inhibition or genetic down-regulation of the mTOR pathway resulted in increase of ATM mRNA and protein both in mouse sarcoma xenografts and cultured cells. mTOR Complex 1 (mTORC1) suppresses ATM via S6K1/2 signaling pathways. microRNA-18a and microRNA-421, both of which target ATM, are positively controlled by mTOR signaling. Our findings have identified a negative feedback loop for the signaling between ATM and mTOR pathways and suggest that oncogenic growth signals may promote tumorigenesis by dampening the ATM checkpoint.

Proof-of-concept rare cancers in drug development: the case for rhabdomyosarcoma

Rare diseases typically affect fewer than 200,000 patients annually, yet because thousands of rare diseases exist, the cumulative impact is millions of patients worldwide. Every form of childhood cancer qualifies as a rare disease-including the childhood muscle cancer, rhabdomyosarcoma (RMS). The next few years promise to be an exceptionally good era of opportunity for public-private collaboration for rare and childhood cancers. Not only do certain governmental regulation advantages exist, but these advantages are being made permanent with special incentives for pediatric orphan drug-product development. Coupled with a growing understanding of sarcoma tumor biology, synergy with pharmaceutical muscle disease drug-development programs, and emerging publically available preclinical and clinical tools, the outlook for academic-community-industry partnerships in RMS drug development looks promising.

Rhabdomyosarcomas: an overview on the experimental animal models

Rhabdomyosarcomas (RMS) are aggressive childhood soft-tissue malignancies deriving from mesenchymal progenitors that are committed to muscle-specific lineages. Despite the histopathological signatures associated with three main histological variants, termed embryonal, alveolar and pleomorphic, a plethora of genetic and molecular changes are recognized in RMS. Over the years, exposure to carcinogens or ionizing radiations and gene-targeting approaches in vivo have greatly contributed to disclose some of the mechanisms underlying RMS onset. In this review, we describe the principal distinct features associated with RMS variants and focus on the current available experimental animal models to point out the molecular determinants cooperating with RMS development and progression.

Advances in pediatric rhabdomyosarcoma characterization and disease model development

Rhabdomyosarcoma (RMS), a form of soft tissue sarcoma, is one of the most common pediatric malignancies. A complex disease with at least three different subtypes, it is characterized by perturbations in a number of signaling pathways and genetic abnormalities. Extensive clinical studies have helped classify these tumors into high and low risk groups to facilitate different treatment regimens. Research into the etiology of the disease has helped uncover numerous potential therapeutic intervention points which can be tested on various animal models of RMS; both genetically modified models and tumor xenograft models. Taken together, there has been a marked increase in the survival rate of RMS patients but the highly invasive, metastatic forms of the disease continue to baffle researchers. This review aims to highlight and summarize some of the most important developments in characterization and in vivo model generation for RMS research, in the last few decades.

Caveolins in rhabdomyosarcoma

Caveolins are scaffolding proteins that play a pivotal role in numerous processes, including caveolae biogenesis, vesicular transport, cholesterol homeostasis and regulation of signal transduction. There are three different isoforms (Cav-1, -2 and -3) that form homo- and hetero-aggregates at the plasma membrane and modulate the activity of a number of intracellular binding proteins. Cav-1 and Cav-3, in particular, are respectively expressed in the reserve elements (e.g. satellite cells) and in mature myofibres of skeletal muscle and their expression interplay characterizes the switch from muscle precursors to differentiated elements. Recent findings have shown that caveolins are also expressed in rhabdomyosarcoma, a group of heterogeneous childhood soft-tissue sarcomas in which the cancer cells seem to derive from progenitors that resemble myogenic cells. In this review, we will focus on the role of caveolins in rhabdomyosarcomas and on their potential use as markers of the degree of differentiation in these paediatric tumours. Given that the function of Cav-1 as tumour conditional gene in cancer has been well-established, we will also discuss the relationship between Cav-1 and the progression of rhabdomyosarcoma.

The MYCN oncogene and differentiation in neuroblastoma

Childhood neuroblastoma exhibits a heterogeneous clinical behavior ranging from low-risk tumors with the ability to spontaneously differentiate and regress, to high-risk tumors causing the highest number of cancer related deaths in infants. Amplification of the MYCN oncogene is one of the few prediction markers for adverse outcome. This gene encodes the MYCN transcriptional regulator predominantly expressed in the developing peripheral neural crest. MYCN is vital for proliferation, migration and stem cell homeostasis while decreased levels are associated with terminal neuronal differentiation. Interestingly, high-risk tumors without MYCN amplification frequently display increased c-MYC expression and/or activation of MYC signaling pathways. On the other hand, downregulation of MYCN leads to decreased proliferation and differentiation, emphasizing the importance of MYC signaling in neuroblastoma biology. Furthermore, expression of the neurotrophin receptor TrkA is associated with good prognosis, the ability to differentiate and spontaneous regression while expression of the related TrkB receptor is correlated with bad prognosis and MYCN amplification. Here we discuss the role of MYCN in neuroblastoma with a special focus on the contribution of elevated MYCN signaling for an aggressive and undifferentiated phenotype as well as the potential of using MYCN as a therapeutic target.

Myogenesis and rhabdomyosarcoma the Jekyll and Hyde of skeletal muscle

Rhabdomyosarcoma, a neoplasm composed of skeletal myoblast-like cells, represents the most common soft tissue sarcoma in children. The application of intensive chemotherapeutics and refined surgical and radiation therapy approaches have improved survival for children with localized disease over the past 3 decades; however, these approaches have not improved the dismal outcome for children with metastatic and recurrent rhabdomyosarcoma. Elegant studies have defined the molecular mechanisms driving skeletal muscle lineage commitment and differentiation, and the machinery that couples differentiation with irreversible cell proliferation arrest. Further, detailed molecular analyses indicate that rhabdomyosarcoma cells have lost the capacity to fully differentiate when challenged to do so in experimental models. We review the intersection of normal skeletal muscle developmental biology and the molecular genetic defects in rhabdomyosarcoma with the underlying premise that understanding how the differentiation process has gone awry will lead to new treatment strategies aimed at promoting myogenic differentiation and concomitant cell cycle arrest.

Differential cooperation of oncogenes with p53 and Bax to induce apoptosis in rhabdomyosarcoma

Background

Deregulated expression of oncogenes such as MYC and PAX3-FKHR often occurs in rhabdomyosarcomas. MYC can enhance cell proliferation and apoptosis under specific conditions, whereas PAX3-FKHR has only been described as anti-apoptotic.

Results

In order to evaluate how MYC and PAX3-FKHR oncogenes influenced p53-mediated apoptosis, rhabdomyosarcoma cells were developed to independently express MYC and PAX3-FKHR cDNAs. Exogenous wild-type p53 expression in MYC transfected cells resulted in apoptosis, whereas there was only a slight effect in those transfected with PAX3-FKHR. Both oncoproteins induced BAX, but BAX induction alone without expression of wild-type p53 was insufficient to induce apoptosis. Data generated from genetically modified MEFs suggested that expression of all three proteins; MYC, BAX and p53, was required for maximal cell death to occur.

Conclusion

We conclude that cooperation between p53 and oncoproteins to induce apoptosis is dependent upon the specific oncoprotein expressed and that oncogene-mediated induction of BAX is necessary but insufficient to enhance p53-mediated apoptosis. These data demonstrate a novel relationship between MYC and p53-dependent apoptosis, independent of the ability of MYC to induce p53 that may be important in transformed cells other than rhabdomyosarcoma.

The Myc oncoprotein as a therapeutic target for human cancer

Myc expression is deregulated in a wide range of human cancers and is often associated with aggressive, poorly differentiated tumors. The Myc protein is a transcription factor that regulates a variety of cellular processes including cell growth and proliferation, cell-cycle progression, transcription, differentiation, apoptosis, and cell motility. Potential strategies that either inhibit the growth promoting effect of Myc and/or activate its pro-apoptotic function are presently being explored. In this review, we give an overview of Myc activation in human tumors and discuss current strategies aimed at targeting Myc for cancer treatment. Such therapies could have potential in combination with mechanistically different cytotoxic drugs to combat and eradicate tumors cells.

MYCN deregulation as a potential target for novel therapies in rhabdomyosarcoma

Rhabdomyosarcoma is the most common soft-tissue sarcoma of childhood. Treatment requires a multimodality approach combining chemotherapy with surgery and radiotherapy. Although overall outcomes have improved considerably, the outlook for patients with high-risk disease, particularly the alveolar subtype, remains bleak and there is a clear need for new chemotherapeutic strategies. This review focuses on the possibilities for interventions targeting myc myelocytomatosis viral related oncogene, neuroblastoma derived (MYCN). The importance of aberrant expression of this oncogene is well established in neuroblastoma and recent data indicate that MYCN deregulation also occurs in up to a quarter of alveolar subtype cases. A range of possible approaches to target MYCN is discussed, including nucleic acid-based and immunotherapy strategies.

Chromosome translocations in sarcomas and the emergence of oncogenic transcription factors

A subset of sarcomas is characterised by recurrent chromosome translocations that generate novel fusion oncoproteins. One or both of the genes involved in these translocations often encode transcription factors, and the resulting fusion proteins have aberrant transcriptional function compared to their wild-type counterparts. These fusion transcription factors disrupt multiple biological pathways by altering expression of target genes, and thereby result in a variety of altered cellular properties that contribute to the tumourigenic process. However, experimental data indicate that the fusion gene alone is not sufficient for transformation in primary cells (EWS-FLI1) or tumourigenesis in the mouse (PAX3-FKHR, FUS-CHOP), suggesting that additional collaborating genetic alterations are required. In addition to improving our understanding of the etiology of these tumours, this accumulating knowledge of the oncogenic properties of these fusion proteins, their downstream targets, and cooperating genetic alterations will permit the development of a variety of novel approaches to improve the therapy of these cancers.

MYCN expression in human rhabdomyosarcoma cell lines and tumour samples

The MYCN oncogene encodes a phosphoprotein that acts as a transcription factor and is involved in the regulation of cell proliferation and differentiation in normal as well as in cancer cells.MYCN amplification and expression have been reported in various tumours, including neuroblastoma and lung cancer, but little is known about its expression in human rhabdomyosarcoma. MYCN expression and amplification were studied in five alveolar and five embryonal rhabdomyosarcoma cell lines and in 19 tumour biopsies. All the cell lines studied expressed MYCN RNA, as demonstrated by northern blot analysis and RT-PCR, but the oncogene was amplified in only one. Similarly, MYCN protein was detected in all cell lines by western blot analysis, with higher levels of expression in alveolar than in embryonal rhabdomyosarcoma cells. RT-PCR analysis of tumour samples demonstrated 18/19 cases positive for MYCN RNA. Although MYCN expression was higher in alveolar than in embryonal rhabdomyosarcoma cell lines, no clear relationship between histology and level of MYCN expression could be established in this tumour series. These data suggest that MYCN expression is a common feature of rhabdomyosarcoma, independent of gene amplification and without a clear relationship with specific histological and clinical features.

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.

Concomitant amplification and expression of PAX7-FKHR and MYCN in a human rhabdomyosarcoma cell line carrying a cryptic t(1;13)(p36;q14)

Alveolar rhabdomyosarcoma (ARMS) is associated with the specific chromosomal translocation (2;13)(q35;q14) or its rarer variant t(1;13)(p36;q14), which produces the fusion gene PAX7-FKHR. Here we describe the human cell line RC2, derived from an ARMS, which harbors a cryptic t(1;13)(p36;q14) and concomitantly shows amplification of the PAX7-FKHR fusion gene and of the MYCN oncogene. The t(1;13) and MYCN oncogene were studied by standard cytogenetic analysis and molecular techniques. The reverse transcriptase polymerase chain reaction demonstrated the expression of PAX7-FKHR mRNA in RC2 cells, although karyotype analysis failed to demonstrate a t(1;13)(p36;q14) chromosomal translocation or a derivative 13 chromosome. Double minute chromosomes were detected in all the metaphases studied. Fluorescence in situ hybridization analysis revealed multiple copies of the PAX7-FKHR fusion gene localized exclusively on a subset of double minutes, whereas multiple copies of MYCN were identified on other double minute chromosomes. Southern-blot analysis demonstrated that RC2 cells contain approximately 20 copies of the MYCN oncogene. So far no continuous RMS cell line carrying the t(1;13)(p36;q14) has been described, and PAX7-FKHR and MYCN amplifications have always been reported to occur separately in rhabdomyosarcoma (RMS). The availability of an ARMS cell line that harbors the t(1;13)(p36;q14) constitutes a useful tool for further understanding the role of the PAX7-FKHR fusion gene in RMS oncogenesis and may improve knowledge of the possible relation between PAX7-FKHR and MYCN amplification.

Genetics of Beckwith-Wiedemann syndrome-associated tumors: common genetic pathways

A specific subset of solid childhood tumors-Wilms' tumor, adrenocortical carcinoma, rhabdomyosarcoma, and hepatoblastoma-is characterized by its association with Beckwith-Wiedemann syndrome. Genetic abnormalities found in these tumors affect the same chromosome region (11p15), which has been implicated in the etiology of Beckwith-Wiedemann syndrome. This suggests that the development of these tumors occurs along a common genetic pathway involving chromosome 11. To search for additional common genetic pathways, this article reviews the genetic data published for these tumors. It was found that, up until now, the only genetic abnormalities detected in all four tumors affect chromosome band 11p15 and the TP53 gene. In addition, there are several aberrations that occur in two or three of the neoplasms. It is concluded that, of the four tumors, the genetic relationship is most evident between Wilms' tumor and rhabdomyosarcoma.

Application of comparative genomic hybridization, spectral karyotyping, and microarray analysis in the identification of subtype-specific patterns of genomic changes in rhabdomyosarcoma

Rhabdomyosarcoma (RMS) in children occurs predominantly as two major histologically defined subtypes called embryonal RMS (RMS-E) and the prognostically less favorable alveolar RMS (RMS-A). Comparative genomic hybridization (CGH) was performed on 21 RMS and identified consistent gains affecting chromosomes 2 (8/10), 5 (5/10), 6 (3/10), 7 (7/10), 8 (9/10), 11 (6/ 10), and 12 (5/10) in RMS-E. Losses/deletions involved chromosomes 19 (2/10) and chromosomes 4, 9, 10, 17, 21 (1/10 each). High copy number amplification, involving the 2p24 region (5/11) and less frequently, the 12q13-21 (2/11), 9p22 (1/11), and 17q22-25 (1/11) regions, was detected in RMS-A. Gene amplification at band 2p24 was present in 6/12 alveolar tumors, and in each case, MYCN was amplified, together with the distally placed DDX1 gene. For these patients there was a shorter disease free interval and a higher mortality than patients with tumors without amplification. Detailed spectral karyotype analysis (SKY) was performed on two RMS cell lines (one of each subtype) and identified a surprisingly high level of structural change. Gene expression studies with the Atlas Human Cancer Array (588 genes) showed that 153 genes generated a signal of similar intensity in both cell lines, and 45 genes appeared to have subtype-specific expression. The chromosomal location of differentially expressed genes was compared to the pattern of genomic alteration in RMS as determined by CGH in this study and the literature.

Prognostic factors in soft tissue sarcoma

The ability to accurately define the prognosis for patients with soft tissue sarcoma is a continuing challenge. Classically, this has been accomplished through assessments of tumor size, histologic grade, location, and the presence of nodal or distant metastases. These criteria are the basis of the currently utilized American Joint Commission on Cancer (AJCC) staging system. However, several other markers have been identified which have prognostic value. These newer markers are useful additions to the AJCC system. Such markers may not only improve our ability to prognosticate at diagnosis, but may also prove useful in selecting high-risk soft tissue sarcoma patients who could benefit from adjuvant therapy. This review will focus upon prognostic factors for patients with soft tissue sarcomas (STS). First, the components of the current AJCC staging system will be discussed; second, a summary of clinical prognostic factors which are not part of the staging system; and third, a discussion of newer and potential prognostic factors for STS patients.

Diagnostic and prognostic implications of the unfolding molecular biology of bone and soft tissue tumours

Sarcomas account for approximately 1-2% of human malignant disease and are relatively uncommon. Histopathological study of these mesenchymal tumours at light microscopic and ultrastructural level may not always provide an unambiguous diagnosis. It has become apparent with the identification of increasing numbers of tumour specific genetic alterations that (cyto) genetic evaluation could become a very helpful adjunct to histopathological assessment in reaching a correct diagnosis. Thus, once the different tumour types can be accurately identified and classified, more meaningful clinical trials can be initiated to evaluate and select optimal methods of management. In addition, an increasing awareness and understanding of the molecular changes associated with, and the genetic variability in, the various tumour groups is beginning to provide important new information about clinical progression and prognosis.

Expression of CD44 by rhabdomyosarcoma: a new prognostic marker?

The expression pattern of CD44 standard and variant isoforms are prognostically significant in a number of malignancies. The aim of this study was to evaluate the role of the standard isoform of CD44 in predicting the clinical behaviour of rhabdomyosarcoma. Immunohistochemical analysis of CD44 was undertaken using a panel of antibodies recognizing the three core domains of the CD44 molecule. Labelling was repeated in triplicate and reported blind with respect to histological type and outcome. Tumours were characterized as positive in more than 60% of tumour cells labelled and negative if less than 40% of tumour cells labelled. Tumours with 40-60% of tumour cells labelling were considered indeterminate. Eleven of 20 favourable histology tumours were positive for CD44 compared with one of seven unfavourable tumours (P = 0.07). Eleven of 12 patients with CD44-positive tumours are alive in first remission compared with five of 15 CD44-negative tumours (P = 0.001). Expression of CD44 correlates directly with prognosis; however, larger studies are required so that multivariate analysis can be undertaken.

Myc oncogene expression and nude mouse tumorigenicity and metastasis formation are higher in alveolar than embryonal rhabdomyosarcoma cell lines

Accumulated clinical evidence suggests that alveolar rhabdomyosarcoma (ARMS) is more aggressive than embryonal rhabdomyosarcoma (ERMS). Here, we study six childhood rhabdomyosarcoma cell lines, three ERMS and three ARMS. We have assayed the ability of the tumor cells to grow in culture and in nude mice as well as their propensity for pulmonary metastasis formation by tail vein injection. We also compared levels of c- and N-myc oncogene expression and DNA copy number. We find no correlation of histologic tumor type (i.e. ERMS versus ARMS) with growth rate in culture, but we do find suggestive correlations of histologic type with tumorigenicity (mean tumor diameter in millimeters at 6 wk: ARMS 30, ERMS 10; p1 = 0.1) and metastasis formation (ARMS 12, ERMS 0; p1 = 0.1). These properties also correlate with uniform greater overexpression of c-myc in ARMS (mean 39.3-fold, range 16-83) compared with ERMS (mean 5.3, range 4-8) (p1 = 0.05, control fibroblasts = 1). Although c-myc was often amplified in vitro (four of six lines), there was no correlation with histologic type (2/3 ARMS, 2/3 ERMS). These data on rhabdomyosarcoma cell lines derived from verified ERMS and ARMS tumors support the impression from previous clinicopathologic observations that ARMS is a more malignant form of rhabdomyosarcoma than ERMS.

Molecular genetics in the diagnosis and prognosis of solid pediatric tumors

The field of molecular genetics continues to see an ever increasing number of applications to pediatric tumor analysis. Studies in pediatric tumors have identified novel genes and other genetic changes, a large number of which reflect one of the following mechanisms: (1) activation of proto-oncogenes; (2) loss of tumor suppressor genes; or (3) creation of novel fusion proteins. At least one of these mechanisms is operational in each of the following pediatric tumors: neuroblastoma, Ewing sarcoma and peripheral primitive neuroectodermal tumor (pPNET), intra-abdominal desmoplastic small-cell tumor, rhabdomyosarcoma, synovial sarcoma, and Wilms tumor. Out of this research has come not only an increased understanding of oncogenesis but also, for each of the tumors listed above, diagnostic and/or prognostic markers that can be used by the pathologist and oncologist to improve overall patient management.

Constitutional balanced translocations in alveolar rhabdomyosarcoma

Chromosomal analysis of tumor tissue from two children with alveolar rhabdomyosarcoma revealed t(1;5)(q32;q31) and t(1;22)(q21;q11.2) in all metaphases examined, respectively. Peripheral blood lymphocytes carried the same cytogenetic abnormality as that of the tumor cells in both patients. Parental lymphocytes were karyotypically normal in the patient with t(1;22), indicating a de novo constitutional translocation, but t(1;5) was paternally inherited in the other patient. The presence of constitutional translocations in these two children might have contributed to the development of alveolar rhabdomyosarcoma.

MYC abrogates p53-mediated cell cycle arrest in N-(phosphonacetyl)-L-aspartate-treated cells, permitting CAD gene amplification

Genomic instability, including the ability to undergo gene amplification, is a hallmark of neoplastic cells. Similar to normal cells, "nonpermissive" REF52 cells do not develop resistance to N-(phosphonacetyl)-L-aspartate (PALA), an inhibitor of the synthesis of pyrimidine nucleotides, through amplification of cad, the target gene, but instead undergo protective, long-term, p53-dependent cell cycle arrest. Expression of exogenous MYC prevents this arrest and allows REF52 cells to proceed to mitosis when pyrimidine nucleotides are limiting. This results in DNA breaks, leading to cell death and, rarely, to cad gene amplification and PALA resistance. Pretreatment of REF52 cells with a low concentration of PALA, which slows DNA replication but does not trigger cell cycle arrest, followed by exposure to a high, selective concentration of PALA, promotes the formation of PALA-resistant cells in which the physically linked cad and endogenous N-myc genes are coamplified. The activated expression of endogenous N-myc in these pretreated PALA-resistant cells allows them to bypass the p53-mediated arrest that is characteristic of untreated REF52 cells. Our data demonstrate that two distinct events are required to form PALA-resistant REF52 cells: amplification of cad, whose product overcomes the action of the drug, and increased expression of N-myc, whose product overcomes the PALA-induced cell cycle block. These paired events occur at a detectable frequency only when the genes are physically linked, as cad and N-myc are. In untreated REF52 cells overexpressing N-MYC, the level of p53 is significantly elevated but there is no induction of p21waf1 expression or growth arrest. However, after DNA is damaged, the activated p53 executes rapid apoptosis in these REF52/N-myc cells instead of the long-term protective arrest seen in REF52 cells. The predominantly cytoplasmic localization of stabilized p53 in REF52/N-myc cells suggests that cytoplasmic retention may help to inactivate the growth-suppressing function of p53.

Rhabdomyosarcoma. Biology and treatment

Rhabdomyosarcoma is the most common soft-tissue sarcoma of childhood. Recognition of specific genetic changes in the two most common subtypes of rhabdomyosarcoma has allowed better understanding of the pathogenesis of this disease. In addition, identification of prognostic factors and the use of risk-directed multimodal therapy have improved the outcome for these patients significantly, with cure rates approaching 70%.

Clinical applications of tumor suppressor genes and oncogenes in cancer

In the search for new ways to better diagnose and monitor cancer, scientists have turned to oncogenes and tumor suppressor genes. These genes are involved in cell differentiation, communication and proliferation and their alteration is frequently associated with cancer. Such alterations include mutations, translocations, amplifications and deletions. In this review, I give examples of using the detection of such alterations for patient diagnosis and monitoring. The practical examples are restricted to a few cancer types, but the identification of new tumor suppressor genes, like BRCA-1 and BRCA-2, is creating new possibilities for determining cancer risk of individual family members. There is no doubt that the cloning of new genes which predispose to sporadic cancer will lead to the introduction of widespread testing to assess risk and to the application of preventive measures.

In vivo amplification of the PAX3-FKHR and PAX7-FKHR fusion genes in alveolar rhabdomyosarcoma

In the pediatric cancer alveolar rhabdomyosarcoma, characteristic t(2;13)(q35;q14) or variant t(1;13)(p36;q14) chromosomal translocations generate PAX3-FKHR or PAX7-FKHR fusion genes. Using fluorescence in situ hybridization, reverse transcriptase-polymerase chain reaction and quantitative Southern blot analyses, we demonstrate that these fusion genes are amplified in 20% of fusion-positive tumors. In particular, we found in vivo amplification of these fusions in one of 22 PAX3-FKHR-positive cases and five of seven PAX7-FKHR-positive cases. These findings indicate that translocation and amplification can occur sequentially in a cancer to alter both the structure and copy number of a gene and thereby activate oncogenic activity by complementary mechanisms.

Classification of rhabdomyosarcomas and related sarcomas. Pathologic aspects and proposal for a new classification--an Intergroup Rhabdomyosarcoma Study

BACKGROUND

There is a need to develop a single prognostically significant classification of rhabdomyosarcomas (RMS) and other related tumors of children, adolescents, and young adults which would be a current guide for their diagnosis, allow valid comparison of outcomes between protocols carried out anywhere in the world, and should enhance recognition of prognostic subsets.

METHOD

Sixteen pathologists from eight pathology groups, representing six countries and several cooperative groups, classified by four histopathologic classification schemes 800 representative tumors of the 999 eligible cases treated on Intergroup Rhabdomyosarcoma Study II. Each tumor was classified according to each of the four systems by each of the pathologists. In addition, two independent subsamples of 200 of the 800 patients were reviewed according to the new system, so that 343 distinct patients were reviewed once, and 57 of these twice.

RESULTS

A study of the survival rates of all subtypes in the sample of 800 patients led to the formation of a new system. This was tested on two independent subsets of 200 of the original cases and found to be reproducible and predictive of outcome by univariate analysis. A multivariate analysis of the 343 patients classified according to the new system indicated that a survival model including pathologic classification and known prognostic factors of primary site, clinical group, and tumor size was significantly better at predicting survival than a model with only the known prognostic factors.

CONCLUSION

This new classification, termed International Classification of Rhabdomyosarcoma (ICR) by the authors, was reproducible and predictive of outcome among patients with differing histologies treated uniformly on the Intergroup Rhabdomyosarcoma II protocols. We believe it should be utilized by all pathologists and cooperative groups to classify rhabdomyosarcomas in order to provide comparability among and within multi-institutional studies.

Detection of the t(2;13)(q35;q14) and PAX3-FKHR fusion in alveolar rhabdomyosarcoma by fluorescence in situ hybridization

Cytogenetic studies of the pediatric solid tumor alveolar rhabdomyosarcoma have demonstrated the presence of a consistent chromosomal translocation, t(2;13)(q35;q14). We recently identified PAX3 and FKHR as the genes on chromosomes 2 and 13, respectively, that are juxtaposed by this translocation. As one means of detecting the t(2;13) translocation in clinical specimens, we have developed a fluorescence in situ hybridization (FISH) assay that may be used for both interphase and metaphase cells. Translocation of the 5' region of the FKHR gene to the derivative chromosome 2, and retention of the 3' region of FKHR on the derivative chromosome 13 [(der(13)], were demonstrated in metaphase cells from a rhabdomyosarcoma cell line with a previously identified t(2;13) translocation. A 5' PAX3 cosmid probe was shown to localize to 2q35 in normal cells, and to translocate to the der(13) in the rhabdomyosarcoma cell line. In order to detect the der(13) in interphase nuclei, we labeled the 3'FKHR and the 5'PAX3 cosmid probes with digoxigenin and biotin, respectively, and used these in a two-color FISH assay. The presence of the der(13) was visualized as juxtaposed or overlapping red and green signals in metaphase and interphase tumor cells. The PAX3-FKHR FISH assay was then applied to a series of cytogenetically characterized pediatric sarcoma cell lines. The presence of the der(13) was demonstrated by FISH in all cases containing a cytogenetically detectable t(2;13). The FISH assay was then applied to a series of 20 embryonal and alveolar rhabdomyosarcoma samples. All 10 of the alveolar rhabdomyosarcoma specimens demonstrated a der(13) with the FISH assay.(ABSTRACT TRUNCATED AT 250 WORDS)

MYCN gene amplification in rhabdomyosarcoma

BACKGROUND

Amplification of the MYCN oncogene, formerly known as N-myc, has been seen in several malignant tumors, particularly neuroblastoma, where its association with a poor clinical outcome is the clearest example of a clinically relevant oncogene mutation in any human cancer.

METHODS

The incidence and clinical significance of MYCN amplification in rhabdomyosarcoma (RMS) was assessed by Southern blot analysis in this retrospective study of seven alveolar RMS and six embryonal RMS.

RESULTS

MYCN amplification (4- to 13-fold) was present in three of seven alveolar RMS (42.9%) but in none of the embryonal RMS. There was no significant difference between the clinical behavior of the MYCN-amplified and unamplified tumors, and no correlation was found with the light microscopic appearances of the tumors or with desmin immunoreactivity.

CONCLUSIONS

The findings are compatible with previous studies that demonstrated cytogenetic evidence of gene amplification in RMS, and help to clarify conflicting reports in the literature about MYCN amplification in alveolar and embryonal RMS. The results raise the possibility of important biologic differences between these subtypes of RMS, differences that warrant further investigation.

Rhabdomyosarcoma of the adult head and neck: a clinicopathological and DNA ploidy study

We investigated the DNA ploidy patterns in thirteen primary and four recurrent rhabdomyosarcomas of the head and neck from thirteen adult patients and correlated the findings with other clinicopathological factors and clinical outcome. Twelve (92.7 per cent) of the primary neoplasms manifested an aneuploid DNA pattern, five had more than one stemline, and one neoplasm displayed a diploid DNA pattern. All recurrent lesions were DNA aneuploid with DNA indices (DIs) corresponding to their primary neoplasms. No correlation between the ploidy pattern and histological subtypes, tumour location, clinical stage and patient's clinical course was found. In this study, only two patients were long-term survivors. Both patients had stage I neoplasms that were located in non-parameningeal sites which manifested an alveolar histological pattern. Our data indicate that adult rhabdomyosarcomas of head and neck are preponderantly DNA aneuploid and are highly aggressive malignant neoplasms. Our results also suggest that tumours which are low stage and in a non-parameningeal location may pursue a less aggressive course.

Rhabdomyosarcomas with primary presentation in the skin

Five primary and two metastatic rhabdomyosarcomas (RMS) with primary presentation in the skin were studied by conventional light microscopy and immunohistochemistry. These cases account for only 0.7% of the 682 cases of RMS collected at two large institutions with a main interest in soft tissue tumors. All but one tumor, which was an embryonal RMS, corresponded to the alveolar subtype. The myogenic nature of the tumor cells was supported by the immunophenotype including positive reactions for vimentin, desmin, and muscle actin. Clinical findings included a male predominance, young age of the patients and the location of all primary cutaneous RMS in the face. One of the two metastatic RMS presented at birth with a clinical picture highly suggestive of congenital metastatic neuroblastoma, notably because of a 100-fold amplification of the N-myc copy number. Thus, this case illustrates again that an amplification of the N-myc oncogene is not restricted to neuroblastoma, but may also occur in other tumor types.

Malignant rhabdoid tumor. A study with two established cell lines

BACKGROUND

Malignant rhabdoid tumor (MRT), originally described as a rare renal sarcoma in childhood, has been known to express phenotypic diversity. In this study, unique characteristics of the MRT cells were investigated by using established cell lines.

METHODS

Immunocytochemical, ultrastructural, cytogenetic, and molecular (by polymerase chain reaction, PCR) analyses were done for two MRT cell lines, one of renal and one of extrarenal origin, before and after differentiation-induction with either 12-O-tetradecanoyl phorbol-13-acetate (TPA) or transretinoic acid (RA).

RESULTS

The proliferating cells in the original tumor tissues as well as in the established cell lines demonstrated neural, epithelial, and mesenchymal markers morphologically. Both cell lines had karyotypic abnormalities including chromosome 22q11.2. The cell line from the extrarenal MRT, Tm87-16, demonstrated distinct morphologic changes with neuroblastic differentiation and produced numerous neuritic processes after treatment with either TPA or RA. The cell line from the renal MRT, STM91-01, suggested schwannian differentiation but did not change morphologically after chemical induction. Both cell lines expressed c-myc, but did not express N-myc, MyoD1, tyrosine hydroxylase, or neural cell adhesion molecule (N-CAM). With PCR and immunocytochemical study, a high level of chromogranin expression was detected by the cells of Tm87-16 only after TPA induced differentiation.

CONCLUSIONS

MRT cells demonstrated diverse phenotype of neuro-ecto-mesenchymal differentiation. The results of this study suggest that MRT may be derived from a primitive pluripotential cell, such as neural crest or equivalent. MRT, therefore, might be categorized as one of the subsets of primitive neuroectodermal tumor.