Detection of the t(2;13) chromosomal translocation in alveolar rhabdomyosarcoma using the reverse transcriptase-polymerase chain reaction

Minimal Infiltrative Disease Identification in Cryopreserved Ovarian Tissue of Girls with Cancer for Future Use: A Systematic Review

BACKGROUND

Ovarian tissue cryopreservation and transplantation are the only available fertility techniques for prepubertal girls with cancer. Though autotransplantation carries a risk of reintroducing malignant cells, it can be avoided by identifying minimal infiltrative disease (MID) within ovarian tissue.

METHODS

A broad search for peer-reviewed articles in the PubMed database was conducted in accordance with PRISMA guidelines up to March 2023. Search terms included 'minimal residual disease', 'cryopreservation', 'ovarian', 'cancer' and synonyms.

RESULTS

Out of 542 identified records, 17 were included. Ovarian tissues of at least 115 girls were evaluated and categorized as: hematological malignancies (n = 56; 48.7%), solid tumors (n = 42; 36.5%) and tumors of the central nervous system (n = 17; 14.8%). In ovarian tissue of 25 patients (21.7%), MID was detected using RT-qPCR, FISH or multicolor flow cytometry: 16 of them (64%) being ALL (IgH rearrangements with/without TRG, BCL-ABL1, EA2-PBX1, TEL-AML1 fusion transcripts), 3 (12%) Ewing sarcoma (EWS-FLI1 fusion transcript, EWSR1 rearrangements), 3 (12%) CML (BCR-ABL1 fusion transcript, FLT3) and 3 (12%) AML (leukemia-associated immunophenotypes, BCR-ABL1 fusion transcript) patients.

CONCLUSION

While the majority of malignancies were found to have a low risk of containing malignant cells in ovarian tissue, further studies are needed to ensure safe implementation of future fertility restoration in clinical practice.

Mechanism of Action of the Sesquiterpene Compound Helenalin in Rhabdomyosarcoma Cells

Rhabdomyosarcoma (RMS) is the most frequent soft tissue sarcoma in paediatric patients. Relapsed or refractory RMS shows very low 5-year survival rates, which urgently necessitates new chemotherapy agents. Herein, the sesquiterpene lactone, helenalin, was investigated as a new potential therapeutic agent against the embryonal RMS (eRMS) and alveolar RMS (aRMS) cells. We have evaluated in vitro antiproliferative efficacy of helenalin on RMS cells by the MTT and wound healing assay, and estimated several cell death pathways by flow cytometry, confocal microscopy and immunoblotting. It was shown that helenalin was able to increase reactive oxygen species levels, decrease mitochondrial membrane potential, trigger endoplasmic reticulum stress and deactivate the NF-κB pathway. Confirmation was obtained through the use of antagonistic compounds which alleviated the effects of helenalin in the corresponding pathways. Our findings demonstrate that oxidative stress is the pivotal mechanism of action of helenalin in promoting RMS cell death in vitro.

Molecular strategies for detecting chromosomal translocations in soft tissue tumors (review)

Approximately one third of soft tissue tumors are characterized by chromosomal aberrations, in particular, translocations and amplifications, which appear to be highly specific. The identification of fusion transcripts not only supports the diagnosis, but provides the basis for the development of novel therapeutic strategies aimed at blocking the aberrant activity of chimeric proteins. Molecular biology, and in particular, cytogenetic and qualitative and quantitative polymerase chain reaction technologies, allow with high efficiency and specificity, the determination of specific fusion transcripts resulting from chromosomal translocations, as well as the analysis of gene amplifications. In this review, various molecular techniques that allow the identification of translocations and consequent fusion transcripts generated are discussed in the broad spectrum of soft tissue tumors.

Utilization of fluorescence in situ hybridization in the diagnosis of 230 mesenchymal neoplasms: an institutional experience

CONTEXT

Mesenchymal neoplasms harbor characteristic translocations and amplification of gene regions amenable to evaluation by fluorescence in situ hybridization (FISH).

OBJECTIVE

To determine the utility of FISH in the diagnosis of mesenchymal neoplasms.

DESIGN

Two hundred thirty soft tissue cases analyzed by FISH were reviewed retrospectively.

RESULTS

Morphologic patterns where FISH was used included high-grade round cell sarcomas (n  =  67), nonmyogenic spindle cell sarcomas (n  =  40), low-grade myxoid neoplasms (n  =  34), adipocytic neoplasms (n  =  20), and melanocytic neoplasms (n  =  19). Fifty cases did not fit into the previously mentioned categories. SYT FISH (96% of monophasic synovial sarcomas were positive; 0% of malignant peripheral nerve sheath tumor were positive) and DDIT3 FISH (100% of myxoid/round cell liposarcomas; no other neoplasm positive) were very sensitive and specific. EWSR1 FISH was very sensitive and specific in the differential diagnosis of melanocytic neoplasms (88% of clear cell sarcomas were positive; all melanomas were negative). EWSR1 FISH was sensitive among high-grade round cell sarcomas (positive in 100% of desmoplastic small round cell tumors and 96% of Ewing sarcoma/primitive neuroectodermal tumors) but not specific because clear cell sarcoma, extraskeletal myxoid chondrosarcoma, and a subset of round cell liposarcomas also harbor rearrangements of EWSR1. FUS FISH was very sensitive in detecting low-grade fibromyxoid sarcomas (91% positive) but not specific because most myxoid/round cell liposarcomas also contain rearrangements of FUS. All atypical lipomatous tumors were positive for amplification of MDM2, whereas all lipomas were negative. FOXO1A FISH was positive in ∼70% of cases of alveolar rhabdomyosarcoma.

CONCLUSION

FISH is a useful adjunct in the diagnosis of mesenchymal neoplasms.

Fluorescence in situ hybridization in the diagnosis of soft tissue neoplasms: a review

This paper presents an overview of the role of fluorescence in situ hybridization (FISH) in the diagnosis of soft tissue neoplasms. Many soft tissue neoplasms harbor characteristic translocations or amplification of gene regions, which can be assessed by FISH, and can be used to assist in their diagnosis. We discuss the major morphologic categories in which FISH has come to be used including high-grade round cell sarcomas, spindle cell sarcomas, low-grade myxoid neoplasms, adipocytic neoplasms, and malignant melanocytic neoplasms on the basis of a recent review of soft tissue neoplasms which were analyzed by FISH. We also review the molecular alterations (translocations and amplification of gene regions), which have come to define many of these diagnostic entities and the most effective way to evaluate them with FISH with attention to potential pitfalls. Finally, we discuss the advantages and disadvantages of FISH as a technique when appraising soft tissue neoplasms.

Transgenic mice expressing PAX3-FKHR have multiple defects in muscle development, including ectopic skeletal myogenesis in the developing neural tube

The t(2;13) chromosomal translocation is found in the majority of human alveolar rhabdomyosarcomas (RMS). The resulting PAX3-FKHR fusion protein contains PAX3 DNA-binding domains fused to the potent transactivation domain of FKHR, suggesting that PAX3-FKHR functions to deregulate PAX3-specific target genes and signaling pathways. We previously developed transgenic mice expressing PAX3-FKHR under the control of mouse Pax3 regulatory sequences to test this hypothesis. We reported that PAX3-FKHR interferes with normal Pax3 developmental functions, with mice exhibiting neural tube and neural crest abnormalities that mimic those found in Pax3-deficient Splotch mice. Here we expanded those studies to show that developmental expression of PAX3-FKHR results in aberrant myogenesis in the developing somites and neural tube, leading to ectopic skeletal muscle formation in the mature spinal cord. Gene expression profiling indicated that PAX3-FKHR expression in the developing neural tube induces a myogenic pattern of gene expression at the expense of the normal neurogenic program. Somite defects in PAX3-FKHR transgenic animals resulted in skeletal malformations that included rib fusions and mis-attachments. As opposed to the neural tube defects, the severity of the rib phenotype was rescued by reducing Pax3 levels through mating with Splotch mice. Embryos from the transgenic line expressing the highest levels of PAX3-FKHR had severe neural tube defects, including exencephaly, and almost half of the embryos died between gestational ages E13.5-E15.5. Nearly all of the embryos that survived to term died after birth due to severe spina bifida, rather than the absence of a muscular diaphragm. These studies reveal a prominent role for PAX3-FKHR in disrupting Pax3 functions and in deregulating skeletal muscle development, suggesting that this fusion protein plays a critical role in the pathogenesis of alveolar RMS by influencing the commitment and differentiation of the myogenic cell lineage.

Use of a novel FISH assay on paraffin-embedded tissues as an adjunct to diagnosis of alveolar rhabdomyosarcoma

A valuable diagnostic adjunct and important prognostic parameter in alveolar rhabdomyosarcoma (ARMS) is the identification of translocations t(2;13)(q35;q14) and t(1;13)(p36;q14), and the associated PAX3-FKHR and PAX7-FKHR fusion transcripts, respectively. Most RMS fusion gene type studies have been based on reverse transcriptase-polymerase chain reaction (RT-PCR) detection of the fusion transcript, a technique limited by RNA quality and failure of devised primer sets to detect unusual variants. As an alternative approach, we developed a fluorescence in situ hybridization (FISH) assay that can: (1) distinguish between the two most common ARMS-associated fusion genes; (2) identify potential unusual variant translocations; (3) assess histologic components in mixed alveolar/embryonal RMS; and (4) be performed on paraffinized tissue. FISH analyses of 75 specimens (40 ARMS, 16 ERMS, 8 mixed ARMS/ERMS, and 11 non-RMS tumors) using selected cosmid clone, bacterial, P1-derived, and yeast artificial chromosome probe sets were successful in all but two cases. Among specimens with informative results for both FISH and RT-PCR or standard karyotyping, PAX/FKHR classification results were concordant in 94.6% (53/56). The three discordant cases included one exhibiting a t(2;13) by FISH that was subsequently confirmed by repeat RT-PCR, a second showing a rearrangement of the PAX3 locus only (consistent with the presence of a PAX3 variant translocation), and a third revealing a t(2;13) by FISH that lacked this translocation cytogenetically. Both alveolar and embryonal components of the mixed ARMS/ERMS subtype were negative for PAX3, PAX7, and FKHR rearrangements, a surprising finding confirmed by RT-PCR and/or conventional karyotyping. These data demonstrate that FISH with newly designed probe sets is a reliable and highly specific method of detecting t(1;13) and t(2;13) in routinely processed tissue and may be useful in differentiating ARMS from other small round cell tumors. The findings also suggest that FISH may be a more sensitive assay than RT-PCR in some settings, capable of revealing variant translocations.

Rhabdomyosarcoma: value of myogenin expression analysis and molecular testing in diagnosing the alveolar subtype: an analysis of 109 paraffin-embedded specimens

BACKGROUND

Identification of the alveolar subtype of rhabdomyosarcoma (ARMS) is important, because the poor prognosis associated with this subtype necessitates a modified therapeutic regimen. At present, ARMS diagnoses are made on the basis of histologic findings and the extent of myogenin immunopositivity. Nonetheless, the absence of an alveolar pattern in the solid variant, the low degree of differentiation in certain embryonal rhabdomyosarcomas (ERMS), and the increasing use of microbiopsy samples make the diagnosis of ARMS somewhat difficult. Two specific translocations have been found in ARMS, and fusion transcripts can be detected by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of paraffin-embedded tissue (PET).

METHODS

To assess the value of myogenin staining and molecular testing in the diagnosis of rhabdomyosarcoma, the authors examined 109 rhabdomyosarcoma samples (45 ARMS samples and 64 ERMS samples). Real-time RT-PCR analysis of PET was performed in all 109 rhabdomyosarcomas, and RT-PCR analysis of frozen material was performed in 24 cases.

RESULTS

PAX fusion transcripts were present in 44 cases (39 ARMS and 5 ERMS) and absent in 52 cases (2 ARMS and 50 ERMS). In 13 cases (4 ARMS and 9 ERMS), the results were not interpretable. Results were concordant between paired frozen and fixed tumor samples. All 35 interpretable ERMS samples that contained < 50% myogenin-positive cells failed to yield detectable PAX fusion transcripts. Of the 61 interpretable tumor samples (41 ARMS and 20 ERMS) that contained > 50% myogenin-positive cells, 44 (39 ARMS and 5 ERMS) yielded detectable PAX fusion transcripts.

CONCLUSIONS

The current study demonstrates that molecular detection of PAX fusion transcripts via real-time RT-PCR analysis of PET is a sensitive and specific method for the diagnosis of ARMS and that immunohistochemical analysis of myogenin expression can be used to select cases for such molecular testing. Although RT-PCR analysis appears not to possess diagnostic value in tumors with < 50% tumor cell immunopositivity, it is strongly recommended for the diagnosis of tumors containing > 50% myogenin-positive cells.

Immunohistochemistry in the diagnosis of soft tissue tumours

Immunohistochemistry is particularly important in the field of soft tissue tumours because of their variety and the frequent difficulty of diagnosis. The first part of this paper discusses useful or new antibodies, together with others that are no longer of use. The second part is devoted to the role of immunohistochemistry in the diagnosis of soft tissue tumours: identification of some rare or atypical benign lesions, identification of non-mesenchymal malignant tumours, and classification of sarcomas. The respective roles of immunohistochemistry and molecular biology are underlined.

Myogenin and MyoD1 expression in paediatric rhabdomyosarcomas

The diagnosis of paediatric solid tumours is often based on small tissue needle biopsies in which many different entities demonstrate a "small round cell tumour" phenotype and in which there may be insufficient tissue to allow the interpretation of diagnostic architectural features, which may be present in larger specimens. Therefore, the extensive use of a panel of immunohistochemical markers is part of the routine handling and investigation of such biopsies to reach a definite diagnosis. However, in some cases the morphological and routine immunohistochemical findings may be insufficient for a precise diagnosis or they may be difficult to interpret in the given clinical context. Although many paediatric tumours exhibit characteristic chromosomal translocations with resultant specific fusion transcripts, these require molecular methods for their detection, usually on fresh tissue samples, which may not always be available. As more immunohistochemical markers become available, more precise diagnosis on such small biopsies may be possible. This review examines the use of the immunohistochemical markers, MyoD1 and myogenin, in the diagnosis of paediatric rhabdomyosarcoma, including its subtypes.

Estrogen regulation of Pak1 and FKHR pathways in breast cancer cells

Stimulation of p21-activated kinase-1 (Pak1) and estradiol-estrogen receptor-alpha in mammary cancer cells promotes cell survival. We sought to determine whether estrogen stimulates the Pak1 pathway. We found that estrogen rapidly activated Pak1 kinase activity in a phosphatidylinositol 3-kinase-insensitive manner. Furthermore, estrogen induced phosphorylation and perinuclear localization of the cell survival forkhead transcription factor FKHR in the cytoplasm in a Pak1-dependent manner. In addition, Pak1 directly interacted with FKHR and phosphorylated it. The noticed phosphorylation-dependent exclusion of FKHR from the nucleus impaired the ability of FKHR to activate its target Fas ligand promoter containing the FKHR binding motif (FRE) in cells treated with estrogen or expressing catalytically active Pak1. In contrast, expression of the dominant-negative auto-inhibitory domain of Pak1 (Pak amino acids 83-149) promoted the ability of FKHR to activate transcription from FRE. Together, these results identify a novel signaling pathway linking estrogen action to Pak1 signaling, and Pak1 to FKHR, suggesting that Pak1 is an important mediator of estrogen's cell survival functions.

Performance characteristics of a reverse transcriptase-polymerase chain reaction assay for the detection of tumor-specific fusion transcripts from archival tissue

Pediatric small round cell tumors still pose tremendous diagnostic problems. In difficult cases, the ability to detect tumor-specific gene fusion transcripts for several of these neoplasms, including Ewing sarcoma/peripheral primitive neuroectodermal tumor (ES/PNET), synovial sarcoma (SS), alveolar rhabdomyosarcoma (ARMS), and desmoplastic small round cell tumor (DSRCT) using reverse transcriptase-polymerase chain reaction (RT-PCR), can be extremely helpful. Few studies to date, however, have systematically examined several different tumor types for the presence of multiple different fusion transcripts in order to determine the specificity and sensitivity of the RT-PCR method, and no study has addressed this issue for formalin-fixed material. The objectives of this study were to address the specificity, sensitivity, and practicality of such an assay applied strictly to formalin-fixed tissue blocks. Our results demonstrate that, for these tumors, the overall sensitivity for detecting each fusion transcript is similar to that reported in the literature for RT-PCR on fresh or formalin-fixed tissues. The specificity of the assay is very high, being essentially 100% for each primer pair when interpreting the results from visual inspection of agarose gels. However, when these same agarose gels were examined using Southern blotting, a small number of tumors also yielded reproducibly detectable weak signals for unexpected fusion products, in addition to a strong signal for the expected fusion product. Fluorescence in situ hybridization (FISH) studies in one such case indicated that a rearrangement that would account for the unexpected fusion was not present, while another case was equivocal. The overall specificity for each primer pair used in this assay ranged from 94 to 100%. Therefore, RT-PCR using formalin-fixed paraffin-embedded tissue sections can be used to detect chimeric transcripts as a reliable, highly sensitive, and highly specific diagnostic assay. However, we strongly suggest that the final interpretation of the results from this assay be viewed in light of the other features of the case, including clinical history, histology, and immunohistochemistry, by the diagnostic pathologist. Additional studies such as FISH may be useful in clarifying the nature of equivocal or unexpected results.

Practical application of molecular genetic testing as an aid to the surgical pathologic diagnosis of sarcomas: a prospective study

The strong correlation of specific reciprocal translocations with individual tumor types and the demonstration that polymerase chain reaction (PCR)-based methods can detect translocations in tissue samples have stimulated interest in the role of molecular genetic testing in diagnostic surgical pathology. To evaluate the clinical utility of PCR-based molecular analysis of soft tissue neoplasms in routine surgical pathology, 131 consecutive soft tissue tumors submitted for molecular genetic testing at a tertiary care teaching hospital were prospectively analyzed over a 36-month period. RT-PCR was used to test tumor RNA for fusion transcripts characteristic of malignant round cell tumors (including Ewing sarcoma/primitive neuroectodermal tumor, desmoplastic small round cell tumor, and alveolar rhabdomyosarcoma), spindle cell tumors (including synovial sarcoma and congenital fibrosarcoma), and fatty tumors (myxoid liposarcoma). DNA sequence analysis was used to confirm the identity of all PCR products, and the PCR results were compared with the histopathologic diagnosis. We found that sufficient RNA for RT-PCR-based testing was recovered from 96% of the 131 cases and the percentage of tumors that tested positive for the associated characteristic fusion transcript was in general agreement with those reported in the literature. DNA sequence analysis of PCR products identified both variant transcripts and spurious PCR products, underscoring the value of product confirmation steps when testing formalin-fixed, paraffin-embedded tissue. Only in rare cases did testing yield a genetic result that was discordant with the histopathologic diagnosis. We conclude that PCR-based testing is a useful adjunct for the diagnosis of malignant small round cell tumors, spindle cell tumors, and other miscellaneous neoplasms in routine surgical pathology practice.

Gene fusions involving PAX and FOX family members in alveolar rhabdomyosarcoma

The chromosomal translocations t(2;13)(q35;q14) and t(1;13)(p36;q14) are characteristic of alveolar rhabdomyosarcoma, a pediatric soft tissue cancer related to the striated muscle lineage. These translocations rearrange PAX3 and PAX7, members of the paired box transcription factor family, and juxtapose these genes with FKHR, a member of the fork head transcription factor family. This juxtaposition generates PAX3-FKHR and PAX7-FKHR chimeric genes that are expressed as chimeric transcripts that encode chimeric proteins. The fusion proteins, which contain the PAX3/PAX7 DNA binding domain and the FKHR transcriptional activation domain, activate transcription from PAX-binding sites with higher potency than the corresponding wild-type PAX proteins. This increased function results from the insensitivity of the FKHR activation domain to inhibitory effects of N-terminal PAX3/PAX7 domains. In addition to altered function, the fusion products are expressed in ARMS tumors at higher levels than the corresponding wild-type PAX products due to two distinct mechanisms. The PAX7-FKHR fusion is overexpressed as a result of in vivo amplification while the PAX3-FKHR fusion is overexpressed due to a copy number-independent increase in transcriptional rate. Finally, though FKHR subcellular localization is regulated by an AKT-dependent pathway, the fusion proteins are resistant to these signals and show exclusively nuclear localization. Therefore, these translocations alter biological activity at the levels of protein function, gene expression, and subcellular localization with the cumulative outcome postulated to be aberrant regulation of PAX3/PAX7 target genes. This aberrant gene expression program is then hypothesized to contribute to tumorigenic behavior by impacting on the control of growth, apoptosis, differentiation and motility.

Histology-specific expression of a DNA repair protein in pediatric rhabdomyosarcomas

PURPOSE

DNA repair enzymes have a critical role in cellular maintenance and survival. The enzyme apurinic/apyrimidinic endonuclease/redox factor 1 (APE/ref1), a key protein in the base excision repair pathway, displays both repair and redox control. We examined the role of APE/ref1 in pediatric embryonal and alveolar rhabdomyosarcomas (ARMS).

MATERIALS AND METHODS

Using an immunohistochemical method, fixed tissue from 31 newly diagnosed pediatric rhabdomyosarcomas were evaluated for expression of APE/ref1. Tissue was obtained from Indiana University and the Cooperative Human Tissue Network.

RESULTS

We demonstrated high levels of expression within the localized and metastatic embryonal rhabdomyosarcomas. This contrasted with both localized and metastatic ARMS, which had low levels of APE/ref1 expression. This histology-specific difference proved to be significant (P = 0.003). Furthermore, the expression within all tumors examined was localized to the nucleus and did not differ between localized and metastatic tumors.

CONCLUSIONS

We propose several hypotheses to explain this histology-specific expression of APE/ref1 in pediatric rhabdomyosarcomas. Because the majority of ARMS expressed either the PAX3/FKHR or PAX7/FKHR fusion transcript, the low level of expression may be related to the redox activity of APE/ref1. The low levels may also be related to the bioreductive activity of APE/ref 1.

Embryonic expression of the tumor-associated PAX3-FKHR fusion protein interferes with the developmental functions of Pax3

A unique chromosomal translocation involving the genes PAX3 and FKHR is characteristic of most human alveolar rhabdomyosarcomas. The resultant chimeric protein fuses the PAX3 DNA-binding domains to the transactivation domain of FKHR, suggesting that PAX3-FKHR exerts its role in alveolar rhabdomyosarcomas through dysregulation of PAX3-specific target genes. Here, we have produced transgenic mice in which PAX3-FKHR expression was driven by mouse Pax3 promoter/enhancer sequences. Five independent lines expressed PAX3-FKHR in the dorsal neural tube and lateral dermomyotome. Each line exhibited phenotypes that correlated with PAX3-FKHR expression levels and predominantly involved pigmentary disturbances of the abdomen, hindpaws, and tail, with additional neurological related alterations. Phenotypic severity could be increased by reducing Pax3 levels through matings with Pax3-defective Splotch mice, and interference between PAX3 and PAX3-FKHR was apparent in transcription reporter assays. These data suggest that the tumor-associated PAX3-FKHR fusion protein interferes with normal Pax3 developmental functions as a prelude to transformation.

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.

[What is new in pediatric oncology?]

The significant progress made in pediatric oncology during recent years has been due to a major breakthrough in the field of molecular biology and the introduction of new therapeutic strategies that take into account both the quality and the duration of life. Molecular biology has already been instrumental in more fully categorizing the 'small round-cell tumor' group, and in reclassifying the 'Ewing family' tumors. It also provides a valuable tool for the prognostic evaluation of neuroblastomas through the analysis of the N-myc oncogene. In addition, it has permitted the identification of the Li-Fraumeni syndrome of predisposition to cancer in the child, thereby raising the problematical ethical issue of communicating relevant information to subjects at risk. Two examples illustrate innovative strategic concepts: 1) Burkitt's lymphoma, or an example of the successful de-intensification of treatment; and 2) brain tumors in young children, regarding which the desire to improve the quality of life has led to innovative attempts to replace radiotherapy by chemotherapy. Considerable progress has been made in the field of neuropsychology, thereby permitting an improved assessment of disorders and a better management of rehabilitation programs. New anti-cancer agents and also chemo- and radiotherapy that spare healthy tissue are also being developed. Gene therapy and molecular biology will play a major role in future therapeutic strategies; and are now at the preclinical trial stage. This significant overall progress leads to a reconsideration of the organizational approach toward treatment of the pediatric patient population suffering from cancer, and a critical assessment of disease management, which should take into account not only the technical aspects of the disease but also familial and social considerations.

Childhood tumors

Pediatric solid tumors represent a distinct set of malignancies of embryonal origin whose incidence peaks in the first years of life. Specific genetic anomalies with pathogenic significance, which have helped to define the diagnosis better and to improve the prognosis of children with these tumors, recently have been discovered. Survival of children with solid tumors also has improved significantly because of effective multidisciplinary care, which, in this case, always involves chemotherapy and surgery. These favorable results require that children with these diseases are referred and treated at institutions that have multidisciplinary teams and the infrastructure and expertise for caring for these children. Diagnostic and therapeutic principles for the most common childhood solid tumors are discussed in this article, with an emphasis on surgical procedures.

Use of tumor-specific gene expression for the differential diagnosis of neuroblastoma from other pediatric small round-cell malignancies

The differential diagnosis of neuroblastoma from other small round-cell tumors of childhood, although clinically of great importance, is sometimes difficult due to the almost indistinguishable appearance of such tumors by conventional microscopy. Because neuroblastomas are characterized by the synthesis of catecholamines, we investigated the possibility that expression of genes involved in this pathway could serve as a molecular marker for this disease. A reverse transcriptase polymerase chain reaction assay was used to analyze expression of tyrosine hydroxylase and dopa decarboxylase in 84 pediatric malignancies including 55 neuroblastomas, 6 Ewing's sarcomas/primitive neuroectodermal tumors, 7 lymphomas, 6 leukemias, 2 rhabdomyosarcomas, 6 osteosarcomas, and 2 phaeochromocytomas. Of the 55 neuroblastoma samples analyzed, 54 expressed clearly detectable levels of both genes. The one sample that did not express either of the genes was rediagnosed both clinically and by molecular genetic analysis as a Ewing's sarcoma. Of the 29 non-neuroblastoma tumor samples examined, the only tumor samples that expressed clearly detectable levels of both tyrosine hydroxylase and dopa decarboxylase were phaeochromocytomas. Like neuroblastomas, these tumors are characterized by high levels of catecholamines. These findings suggest that expression of genes involved in catecholamine biosynthesis may be useful for differentiating neuroblastoma from other small round-cell tumors of childhood.

Protein kinase B/Akt-mediated phosphorylation promotes nuclear exclusion of the winged helix transcription factor FKHR1

Although genetic analysis has demonstrated that members of the winged helix, or forkhead, family of transcription factors play pivotal roles in the regulation of cellular differentiation and proliferation, both during development and in the adult, little is known of the mechanisms underlying their regulation. Here we show that the activation of phosphatidylinositol 3 (PI3) kinase by extracellular growth factors induces phosphorylation, nuclear export, and transcriptional inactivation of FKHR1, a member of the FKHR subclass of the forkhead family of transcription factors. Protein kinase B (PKB)/Akt, a key mediator of PI3 kinase signal transduction, phosphorylated recombinant FKHR1 in vitro at threonine-24 and serine-253. Mutants FKHR1(T24A), FKHR1(S253A), and FKHR1(T24A/S253A) were resistant to both PKB/Akt-mediated phosphorylation and PI3 kinase-stimulated nuclear export. These results indicate that phosphorylation by PKB/Akt negatively regulates FKHR1 by promoting export from the nucleus.

Cloning and characterization of three human forkhead genes that comprise an FKHR-like gene subfamily

Alveolar rhabdomyosarcomas are associated with unique chromosomal translocations t(2;13) and t(1;13), which arise from fusion of the genes for the paired box proteins PAX3 and PAX7, respectively, to the FKHR (forkhead in rhabdomyosarcoma) gene on chromosome 13q14. Here we report the identification and characterization of three novel human forkhead genes with similarity to FKHR. The three genes (HGMW-approved symbols FKHRP1, FKHRL1, and FKHRL1P1) map to chromosomal regions 5q35.2-q35.3, 6q21, and 17p11, respectively. Based on amino acid sequence comparisons of their forkhead domains, FKHRL1, FKHRL1P1, and FKHRP1 share 86, 84, and 68% identity, respectively, with FKHR. While FKHR and FKHRL1 are expressed in every human adult tissue examined, FKHRP1 mRNA expression could not be detected, and FKHRL1P1 expression was present only at low levels. FKHR and FKHRL1 share a similar genomic organization, each having a very large intron 1 (FKHR approximately 130 kb and FKHRL1 > 90 kb), which bisects their respective forkhead domains at identical positions, as well as a second intron just downstream of each stop codon. FKHRP1 and FKHRL1P1 lack introns and contain stop codons that prevent them from yielding full-length proteins. Thus, while FKHR and FKHRL1 represent functional genes, FKHRP1 and FKHRL1P1 probably are processed pseudogenes. These results suggest that these four genes represent an FKHR-like gene subfamily within the larger human forkhead gene family.

Chromosomal translocations involving paired box transcription factors in human cancer

The PAX genes encode a family of transcription factors that control development within the neural, myogenic, lymphoid, and a variety of other lineages. These proteins are postulated to regulate expression of gene products that function in the control of cellular processes are fundamental to the development of cancer, and thus genetic alterations of these genes may contribute to neoplastic development within these lineages. In support of this premise, several PAX genes have been shown to be targets of consistent chromosomal translocations associated with specific tumor types. The t(2;13) and t(1;13) translocations associated with the myogenic soft tissue cancer alveolar rhabdomyosarcoma fuse portions of the PAX3 or PAX7 gene with a portion of the FKHR gene to generate novel fusion proteins. The t(9;14) translocation associated with the B cell tumor lymphoplasmacytoid lymphoma juxtaposes the PAX5 gene into the vicinity of the IGH locus to deregulate PAX5 expression. This review will examine the molecular basis of these translocations and the role of altered function or expression of paired box transcription factors in the process of tumorigenesis.