Formation of undifferentiated mesenteric tumors in transgenic mice expressing human neurotropic polymavirus early protein

The human polyomavirus, JCV, is the established etiologic agent of the human demyelinating disease, progressive multifocal leukoencephalopathy (PML) seen in immunosuppressed individuals. In PML patients, the viral early protein, which is produced exclusively in glial cells is responsible for initiation of the viral lytic cycle. The JCV early protein, T-antigen, has greater than 70% homology to the well characterized SV40 early protein which has established oncogenic properties. To investigate the role of JCV T-antigen in tumorigenesis, transgenic mice containing the viral early genome were produced. Of the four positive transgenic animals, one developed severe neurological abnormalities and succumbed to death at 3 weeks of age. Another animal died with no visible gross pathology and the cause of death was not determined. The remaining two founders developed massive, undifferentiated, solid mesenteric tumors with no obvious neurological symptoms. Results from histologic analysis demonstrated the presence of highly cellular, poorly differentiated neoplastic cells in the tumor tissue. Electron microscopic evaluation of the tumor revealed the presence of a small blue cell-like tumor of epithelial/neuroectodermal origin. Results from RNA analysis by non-quantitative and highly sensitive RT-PCR indicated the presence of the JCV early transcript in various tissues, including kidney, liver, spleen, heart, lung, and brain, as well as in the tumors. However, analysis of the viral early protein by Western blot and immunohistochemistry indicated high level production of JCV early protein in the tumor tissue, but not in any other tissues. These observations present the first evidence for the development of inheritable neuroectodermal tumors induced by the human polyomavirus, JCV, early protein in a whole animal system.

Infrequent alterations of the p15, p16, CDK4 and cyclin D1 genes in non-astrocytic human brain tumors

While several genetic alterations associated with the evolution of the astrocytomas have been identified, the molecular basis of non-astrocytic brain tumors has remained largely unknown. In this study, p15, p16, CDK4 and cyclin D1 genes were analyzed in 69 nonastrocytic human brain tumors, including 17 oligodendrogliomas, 16 medulloblastomas/primitive neuroectodermal tumors (PNETs), 14 ependymomas and 22 meningiomas. Southern blot analysis of DNA from frozen samples showed no homozygous deletions in p15 or p16 genes in any of these tumors. No mobility shift was found by PCR-single-strand conformation polymorphism (PCR-SSCP) analysis in exons 1 and 2 of the p15 gene and exons 1 and 2 of the p16 genes, except for one oligodendroglioma. Direct sequencing of DNA from this tumor showed a G --> A transition at nucleotide 436 (codon 140) in exon 2 of the p16 gene, which is a common polymorphism. Southern blot analyses revealed no amplification of CDK4 and cyclin D1 genes in any of the neoplasms analyzed. In contrast to astrocytic brain tumors, which show frequent loss of the p16 gene and amplification of the CDK4 gene, alteration of these genes appears to be rare in other neoplasms of the human nervous system.

Establishment of a human cell line secreting neuron-specific enolase from a primitive neuroectodermal tumor of the retroperitoneal cavity

Primitive neuroectodermal tumor (PNET) is one of the small round cell malignancies of presumed neural crest origin for which an effective treatment has not yet been established. In the present study, a human cell line, designated KU-9, was established from a 27-year-old male patient with PNET of the retroperitoneal cavity and has been successfully maintained in nude mice and in culture. On histological examination, the primary tumor was composed of poorly differentiated small round cells arranged in clusters showing a variety of mitotic changes, and contained Homer-Wright rosettes. The histopathological appearance of the KU-9 xenografts was similar to that of the primary tumor. Electron microscopy revealed neurosecretory granules and cytoplasmic processes in the xenograft. No significant amplification of N-myc gene was observed in the KU-9 cells. The KU-9 cells showed chromosome numbers ranging from 56 to 61 with consistent structural abnormalities being add(2)(q31), +add(11)(p11.2), +add(13)(p11.1), and +del(22)(q12). Cultured KU-9 cells grew exponentially with a doubling time of about 50 h and a time-dependent increase in medium levels of neuron-specific enolase (NSE) was noted. Serum levels of NSE in KU-9 tumor-bearing nude mice were significantly elevated and a linear relationship between the serum NSE levels and the tumor NSE content or tumor volume was observed, suggesting that serum levels of NSE may reflect the PNET tumor burden and tumor extent. These results indicate that the KU-9 cell line provides a reproducible model system which could be useful in gaining some insight into the histogenesis and oncogenesis of PNET and in establishing an effective treatment for PNET.

Somatic mutations in the neurofibromatosis 1 gene in gliomas and primitive neuroectodermal tumours

The increased frequency of glioma among neurofibromatosis 1 (NF1) patients suggests a general involvement of the NF1 gene in glioma tumourigenesis. Using the methodology of conventional Southern blotting with a complete panel of overlapping partial cDNAs covering the whole NF1 gene, we screened 31 gliomas of several different subtypes and 3 primitive neuroectodermal tumours (PNETs) from non-NF1 patients for aberrant restriction patterns in their tumour DNA samples. Clear evidence for somatic mutation events at the NF1 gene locus was found in 1 astrocytoma, 2 glioblastomas, 1 ependymoma and 1 PNET with an astrocytic component. These results suggest that the NF1 gene is important in suppressing tumours of neuroectodermal origin.

Cytogenetic and DNA analysis of two neuroectodermal tumors without a simple t(11;22)

Cytogenetic analysis was conducted on tumor biopsy material from two pediatric, small, round, blue-cell tumors whose histology failed to give a clearcut diagnosis. The first case showed a complex composite karyotype within which there were two normal chromosomes 11 and one abnormal chromosome 22 present. The composite karyotype in the second case was similarly complex but this time included an abnormal chromosome 11 but no corresponding abnormal chromosome 22. Analysis of tumor mRNA from both cases using a Reverse Transcriptase PCR test with primers derived from a Ewing's sarcoma t(11;22)(q24;q12) breakpoint sequence showed both to have abnormal, chimeric transcribed messengers, each of different lengths. Further analysis of case 2 using chromosome painting and centromeric probing confirmed the abnormal chromosome 11 to be a der(11)t(11;22)(q24;q12) and also revealed two additional minor clones containing a der(22), which may be the karyotypic locations of the t(11;22) fusion sequences. Taken into consideration with clinical and histologic information, the results of these investigations indicated that both were neuroectodermal tumors (Ewing sarcomas of the chest wall/Askin tumors). The comparative values of both cytogenetic and molecular analysis in the diagnosis of neuroectodermal tumors and the detection of covert chromosome rearrangements are discussed.

Heritable formation of neuroectodermal tumor in transgenic mice carrying the combined E1 region gene of adenovirus type 12 with the deregulated human renin promoter

Adenovirus early 1 (E1) region gene products, including E1A and E1B, are required for transcriptional regulation of viral and cellular promoters in infected and transfected culture cells and for transformation of primary rodent cells. Here, we established a line of transgenic mice carrying the E1 region gene of human adenovirus type 12 under the control of the human renin promoter, in which a neuroectodermal tumor derived from retroperitoneal, olfactory, and/or pelvic regions was heritably developed with varying degrees of incidence and the phenotype was successfully passed through six generations. The transgenes were located in the region E2-E3 bands of chromosome 7 with which no genetic linkage to neuroectodermal tumors was previously demonstrated, and expressed only in the tumors but not in another tissue examined. Notably, in addition to the expression of a neural marker gene N-CAM, the three nuclear oncogenes, c-, L-, and N-myc, were coexpressed in the tumors. These results suggest that E1A and E1B are cooperatively involved in the heritable formation of neuroectodermal tumors associated with co-expression of the three sets of myc family genes.

Neuroectodermal tumors expressing c-, L-, and N-myc in transgenic mice that carry the E1A/E1B gene of human adenovirus type 12

Adenovirus early 1 (E1) region gene products, including E1A and E1B, are required for transformation of primary cultured rodent cells. In order to investigate in vivo action of the E1 region, we established a line of transgenic mice carrying the oncogenic E1A and E1B genes of human adenovirus type 12 under control of the human angiotensinogen promoter. Histopathological analyses indicated that transgenic mice heritably develop neuroectodermal tumors arising from the pelvic region with varying degrees of incidence. The transgene was expressed in the neuroectodermal tumors as well as in TNT-1 cells, a cell line established from the tumors, where the human angiotensinogen promoter was constitutively active. The high level expression of c-, L-, and N-myc without gene amplification was notable in the original tumors and TNT-1 cells, but not in another tissue examined. The co-expression of the three sets of myc family genes in both the original tumors and the established cell line provided the possibility that the target cells for transformation may belong to a specific cell type that expresses all these oncogenes during development.

Increased risk of neuroectodermal tumors and stomach cancer in relatives of patients with Ewing's sarcoma family of tumors

BACKGROUND

Previous studies of the genetic epidemiology of Ewing's sarcoma have shown neither an increased incidence nor a distinct pattern of cancers in family members of Ewing's sarcoma patients.

PURPOSE

Because of a new biologic and cytogenetic classification of Ewing's sarcoma family of tumors, we wanted to reinvestigate the incidence and distribution of cancers in relatives of probands with Ewing's sarcoma family of tumors.

METHODS

Patients treated at the Pediatric Branch and the Radiation Oncology Branch of the National Cancer Institute between 1965 and December 1992, or their next of kin, were asked to complete a questionnaire on the history of cancer in all first- and second-degree relatives. The incidence of cancer in family members was compared with Connecticut Tumor Registry rates specific for sex, age, and 5-year calendar-year intervals. Observed/expected (O/E) ratios, 95% confidence intervals (CIs), and tests of homogeneity were calculated.

RESULTS

Four thousand six hundred seventy-eight family members with 196,640 person-years at risk entered the analysis. Overall, there was no increased risk of cancer (observed 472; O/E = 0.9; 95% CI = 0.8-1.0). However, several tumor types were found in significant excess. These tumors included stomach cancer (observed 34; O/E = 2.0; 95% CI = 1.4-2.8), melanoma (observed 23; O/E = 1.9; 95% CI = 1.2-2.8), brain tumor (observed 18; O/E = 1.9; 95% CI = 1.1-3.0), and bone cancer (observed 7; O/E = 4.2; 95% CI = 1.7-8.6). Risks of these cancers were higher among maternal than paternal relatives, but these differences were not statistically significant. There was a significant deficit of bladder cancer (observed 5; O/E = 0.2; 95% CI = 0.1-0.5) and rectal cancer (observed 0; O/E = 0.0; 95% CI = 0.0-0.1). Second-degree relatives had a significant cancer deficit (observed 389; O/E = 0.9; 95% CI = 0.8-0.95). This deficit was accounted for by the observed deficit of bladder and rectal cancer and is probably related to under-reporting or misclassification of cancer in second-degree relatives. Family members of 10 probands with second malignancies did not have an increased risk of all cancers (observed 20; O/E = 1.2; 95% CI = 0.7-1.8) but had an increased risk of both melanoma (observed 3; O/E = 7.3; 95% CI = 1.5-21.0) and breast cancer (observed 8; O/E = 3.2; 95% CI = 1.4-6.3).

CONCLUSION

Finding an increased risk of neuroectodermal tumors and stomach cancer in families of patients with Ewing's sarcoma family of tumors suggests that these tumors might share a common etiology. Further studies should try to confirm this hypothesis and to examine if genetic factors may have a role in these families by assessing the mode of inheritance and examining families with multiple affected members.

EWS-erg and EWS-Fli1 fusion transcripts in Ewing's sarcoma and primitive neuroectodermal tumors with variant translocations

We have determined the frequency of EWS fusion transcripts in a series of primary Ewing's sarcomas and peripheral primitive neuroectodermal tumors and cells lines. Type 1 and 2 EWS-Fli1 fusions were demonstrated in 8 cell lines and 14 patient samples. Five patients with cytogenetically characterized rearrangements of chromosome 22 that did not involve chromosome 11 were included in these studies. A novel EWS-Fli1 in-frame isoform fusing EWS to exon 8 of Fli1 was isolated from a tumor with a variant t(12;22;22)(q14;p1;q12) translocation. Three in-frame isoforms of a novel hybrid transcript derived from the fusion of EWS with the ETS domain of the human erg gene were identified in patient samples and a cell line with cytogenetically unidentified or cryptic translocations involving chromosomes 21 and 22. Interphase analysis by fluorescent in situ suppression hybridization using two overlapping erg yeast artificial chromosome clones demonstrated disruption of the erg gene on chromosome 21 in a patient sample with monosomy 22. Our results provide new information about the involvement of EWS in small round cell tumors involving exchange of its putative RNA-binding domain with DNA-binding domains derived from different members of the ETS family of transcription factors. These studies emphasize the utility of reverse transcriptase PCR analysis and fluorescent in situ hybridization as additional diagnostic tools for differential diagnosis among small round cell tumors.

Rapid and specific diagnosis of t(11;22) translocation in paediatric Ewing's sarcoma and primitive neuroectodermal tumours using RNA-PCR

One case of paediatric Ewing's sarcoma and two peripheral primitive neuroectodermal tumours/extra-osseous Ewing's sarcoma were studied for the characteristic t(11;22) translocation, using a recently described RNA-polymerase chain reaction method (RNA-PCR). PCR products of the expected sizes were obtained from RNA derived from the Ewing's sarcoma and the peripheral primitive neuroectodermal tumours, but not from other paediatric malignancies. Direct sequencing of the RNA-PCR products confirmed the presence of the EWS-FLI-1 fusion transcript. In one case the presence of the translocation was confirmed by cytogenetic analysis. These results highlight the potential use of PCR for the rapid demonstration of diagnostically important tumour specific chromosome rearrangements.

Genomic structure of the EWS gene and its relationship to EWSR1, a site of tumor-associated chromosome translocation

The EWS gene has been identified based on its location at the chromosome 22 breakpoint of the t(11;22)(q24;q12) translocation that characterizes Ewing sarcoma and related neuroectodermal tumors. The EWS gene spans about 40 kb of DNA and is encoded by 17 exons. The nucleotide sequence of the exons is identical to that of the previously described cDNA. The first 7 exons encode the N-terminal domain of EWS, which consists of a repeated degenerated polypeptide of 7 to 12 residues rich in tyrosine, serine, threonine, glycine, and glutamine. Exons 11, 12, and 13 encode the putative RNA binding domain. The three glycine- and arginine-rich motifs of the gene are mainly encoded by exons 8-9, 14, and 16. The DNA sequence in the 5' region of the gene has features of a CpG-rich island and lacks canonical promoter elements, such as TATA and CCAAT consensus sequences. Positions of the chromosome 22 breakpoints were determined for 19 Ewing tumors. They were localized in introns 7 or 8 in 18 cases and in intron 10 in 1 case.

Cytogenetic analysis of 109 pediatric central nervous system tumors

Reports of cytogenetic abnormalities in pediatric central nervous system (CNS) tumors are important for collection and comparison of large numbers of karyotypes of primary CNS neoplasms to produce statistically significant correlations. We report cytogenetic results of 119 samples of pediatric CNS tumors from 109 patients. Tumors included 33 low-grade astrocytomas, 18 high-grade astrocytomas, 14 gangliogliomas, 13 ependymomas, 17 primitive neuroectodermal tumors (PNET), three choroid plexus papillomas and carcinomas, and a miscellaneous group of 20 rare primary CNS tumors and metastases. In each group, cytogenetic results were correlated with histologic subtype and survival. The study indicated specific chromosome abnormalities in different groups of tumors. Low-grade astrocytomas showed mostly numeric abnormalities with gains of chromosome 7, high-grade astrocytomas showed differences from karyotypic changes observed in adults in lacking double minutes (dmin) and monosomy 10. The ependymoma group showed the largest proportion of abnormal karyotypes with frequent involvement of chromosome 6 and 16. Chromosome 6 was the single most common abnormal chromosome in this study, closely followed by chromosomes 1 and 11. Pediatric CNS neoplasms differ from adult tumors cytogenetically as well as histologically and biologically.