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Although the t(2;13)(q35;q14) translocation has been found in most cases of the pediatric cancer alveolar rhabdomyosarcoma, several cases have been reported with a variant t(1;13)(p36;q14) translocation. Our findings indicate that this t(1;13) rearranges PAX7 on chromosome 1 and fuses it to FKHR on chromosome 13. This fusion results in a chimeric transcript consisting of 5' PAX7 and 3' FKHR regions, which is similar to the 5' PAX3-3' FKHR transcript formed by the t(2;13). The 5' PAX3 and PAX7 regions encode related DNA binding domains, and therefore we postulate that these translocations create similar chimeric transcription factors that alter expression of a common group of target genes.

Cytogenetic studies of eight meningiomas in young children or adolescents were performed. Two tumors exhibited normal karyotypes. Two tumors from patients with bilateral acoustic neurofibromatosis demonstrated monosomy 22 as the only abnormality. Four patients had more complicated karyotypes in which one or both of the chromosomes 22 were missing or structurally altered. The most common secondary changes in these four tumors involved monosomy or structural abnormalities of chromosome 6. These findings confirm that the primary cytogenetic changes in meningioma are similar in children and adults. Molecular analyses of pediatric meningiomas with deletions or translocations of chromosome 22 will be useful for identifying the role of chromosome 22 tumor suppressor genes in this disease.

We have established two cell lines, PER-452 and PER-453, from an 8-month-old girl with an extensive pineoblastoma. Characterization of these lines revealed that the proto-oncogenes MYC and MYCN were not amplified, but both cell lines showed MYCN expression comparable to a cell line with 200-fold MYCN amplification. Both cell lines contained an i(17q). These results support the concept that pineoblastomas belong to a larger group of primitive neuroectodermal tumors of the central nervous system. These two cell lines provide a unique opportunity to investigate the molecular genetic mechanisms underlying these neoplasms further.

A polymorphism at codon 36 in exon 4 of the p53 gene was identified by single strand conformation polymorphism (SSCP) analysis and direct sequencing of genomic DNA PCR products. The polymorphic allele, present in the heterozygous state in genomic DNAs of four of 100 individuals (4%), changes the codon 36 CCG to CCA, eliminates a FinI restriction site and creates a BccI site. Including this polymorphism there are four known polymorphisms in the p53 coding sequence.

Congenital conotruncal cardiac defects occur with increased frequency in patients with DiGeorge syndrome (DGS). Previous studies have shown that the majority of patients with DGS or velocardiofacial syndrome (VCFS) have a microdeletion within chromosomal region 22q11. We hypothesised that patients with conotruncal defects who were not diagnosed with DGS or VCFS would also have 22q11 deletions. Seventeen non-syndromic patients with one of three types of conotruncal defects most commonly seen in DGS or VCFS were evaluated for a 22q11 deletion. DNA probes from within the DiGeorge critical region were used. Heterozygosity at a locus was assessed using restriction fragment length polymorphisms. Copy number was determined by dosage analysis using Southern blot analysis of fluorescence in situ hybridisation of metaphase spreads. Five of 17 patients were shown to have a 22q11 deletion when evaluated by dosage analysis. This study shows a genetic contribution to the development of some conotruncal cardiac malformations and alters knowledge regarding the risk of heritability of these defects in certain cases.

We present the cytogenetic findings in a case of a newly described tumor of childhood, intra-abdominal desmoplastic small round cell tumor (IADSRCT). The karyotype demonstrated a single chromosomal translocation, (11;22)(p13;q12).

We report on a patient with a complex heart defect, short webbed neck, multiple other minor features, and a 46,XX,15p+ de novo karyotype. The enlarged short arm of the chromosome 15 was Distamycin-DAPI and C-band negative. Fluorescence in situ hybridization (FISH) using an alpha satellite probe from chromosome 15 demonstrated hybridization only to the normal 15. In situ hybridization using a set of probes that bind to the short arm (17p13) and centromere of chromosome 17 demonstrated that the extra material on chromosome 15, including the centromere, was derived from chromosome 17. Therefore, this patient has a duplication of the centromere and short arm of chromosome 17. Clinical manifestations in this patient were consistent with those in previously described patients with dup (17p).

We have determined that PAX3 (found previously to be mutated in Waardenburg syndrome) is the chromosome 2 locus rearranged by the t(2;13)(q35;q14) translocation of the paediatric solid tumour alveolar rhabdomyosarcoma. The rearrangement breakpoints occur within an intron downstream of the paired box and homeodomain-encoding regions. Upstream PAX3 sequences hybridize to a novel transcript in t(2;13)-containing lines. Cloning and characterization of this novel transcript indicate that the translocation juxtaposes the PAX3 DNA binding elements with chromosome 13 sequences, suggesting formation of a hybrid transcription factor. Therefore, PAX3 gene alterations are associated with two completely unrelated human diseases.

We describe a child with dysmorphic features, as well as developmental and growth delay, who developed neuroblastoma at 5 mo of age. Cytogenetic analysis of blood lymphocytes revealed an interstitial deletion of 1p36.1-->1p36.2, which was apparent only with high-resolution banding. Molecular analysis with a collection of polymorphic DNA probes for 1p confirmed an interstitial deletion involving subbands of 1p36. Deletions of this region are a common finding in neuroblastoma cells from patients with advanced stages of disease. Therefore, these results (a) suggest that constitutional deletion of this region predisposed the patient to the development of neuroblastoma and (b) support the localization of a neuroblastoma tumor-suppressor locus to 1p36.

Among the small round cell tumors differential diagnosis is particularly difficult for their undifferentiated or primitive character. In this mixed group of tumors, only the primitive neuroectodermal tumors, which include Ewing's sarcoma (ES), show the unique and consistent feature of the (11;22)(q24;q12) translocation, which can therefore be considered a hallmark of these neoplasias. We analyzed four primitive neuroectodermal tumor cell lines, one osteosarcoma cell line, and 11 patients by fluorescent in situ hybridization with cosmid clones 23.2 and 5.8, bracketing the t(11;22) at 11q24. Metaphase spreads from tumor cell lines, and from biopsy specimens of three patients with ES were analyzed. In the remaining eight patients comprising five ES, two small cell osteosarcomas and one chronic osteomyelitis, only nuclei preparations were available for analysis. We detected the t(11;22) in interphase nuclei of the four primitive neuroectodermal tumor cell lines, of three patients in which the karyotype demonstrated the translocation and in five cases of ES in which cytogenetic analysis had not been possible. Two cases of small cell osteosarcoma and one chronic osteomyelitis were also analyzed and were both normal with respect to the t(11;22). By analyzing cell lines and small round cell tumor samples by fluorescent in situ hybridization, we established that interphase cytogenetics is a rapid alternative to chromosomal analysis for the detection of the t(11;22) and represents an invaluable tool for the differential diagnosis of small round cell tumors.

We report an unusual large, multicystic, posterior fossa neuroepithelial neoplasm involving the cerebellum, brain-stem, and quadrigeminal cistern of a 9-month-old girl. The neoplasm consisted of variably sized, sharply demarcated nests of small cells with a high nuclear-cytoplasmic ratio and moderately basophilic nuclei, embedded in a desmoplastic, immature-appearing, mesenchymal stroma. The nests contained mitoses but none were seen in the stroma. Glial fibrillary acidic protein (GFAP), neurofilament protein, synaptophysin, and cytokeratin (AE-1) were expressed in the nests. Mesenchymal cells were negative for neural markers but positive for vimentin and desmin. The neoplasm was interpreted as a mixed mesenchymal and primitive neuroectodermal tumor (PNET) with histologic features reminiscent of a recently described intraabdominal desmoplastic small cell tumor. The tumor responded poorly to chemotherapy and a second operation was performed 1 year later. The second specimen bore no resemblance to the original and consisted of epithelial-like nests and clusters of neoplastic cells frequently interrupted by sinusoidal vessels. Tumor cells had medium-sized vesicular nuclei with small nucleoli, and a granular cytoplasm. Occasional less cellular islands of neuropil-like tissue contained larger cells having eccentric, vesicular nuclei with prominent nucleoli and abundant pink cytoplasm. Mitoses were not conspicuous. Many cells expressed synaptophysin, neurofilament protein, and GFAP. Neurofilament protein was strongly positive in the larger, neuron-like cells and synaptophysin stained the neuropil-like areas strongly but was less prominent in the neuronal perikarya. Unexpectedly, the neuropil-like areas expressed epithelial membrane antigen, whereas the neuronal cells were negative for chromogranin A. The peculiar histologic picture, combination of phenotypic markers, and remarkable biologic behavior of this unusual tumor defies classification according to existing nomenclature and exemplifies the broad range of phenotypes expressed by primitive neuro-epithelial neoplasms.

We previously reported the non-random occurrence of monosomy 22 in rhabdoid or atypical teratoid tumors of the brain in three young children. We now present cytogenetic and molecular studies of an additional rhabdoid tumor with the karyotype 46,XX,-9,-22,+i(1q),+der(22)t(9;22)(p13;q11)/45,XX,-9,-10,- 22,+i(1q),+der(22)t(9;22)(p13;q11). These studies further demonstrate the involvement of chromosome 22, and they begin to define the critical region containing a gene or genes involved in the development or progression of rhabdoid tumors of the brain.

A characteristic translocation t(2;13)(q35;q14) has been previously identified in the pediatric soft tissue tumor alveolar rhabdomyosarcoma. We have assembled a panel of lymphoblast, fibroblast, and somatic cell hybrid cell lines with deletions and unbalanced translocations involving chromosome 2 to develop a physical map of the distal 2q region. Twenty-two probes were localized on this physical map by Southern blot analysis of the mapping panel. The position of these probes with respect to the t(2;13) rhabdomyosarcoma breakpoint was then determined by quantitative Southern blot analysis of an alveolar rhabdomyosarcoma cell line with two copies of the derivative chromosome 13 and one copy of the derivative chromosome 2 and by analysis of somatic cell hybrid clones derived from an alveolar rhabdomyosarcoma cell line. We demonstrate that the t(2;13) breakpoint is situated within a map interval delimited by the distal deletion breakpoint in fibroblast line GM09892 and the t(X;2) breakpoint in somatic cell hybrid GM11022. Furthermore, from a comparison of our data with the linkage map of the syntenic region on mouse chromosome 1, we conclude that the t(2;13) breakpoint is most closely flanked by loci INHA and ALPI within this map interval.

Primitive neuroectodermal tumors of the central nervous system are the most common malignant brain tumors in children. Cytogenetic analysis of these tumors has demonstrated alterations of chromosome 17, in particular isochromosome 17q, as the most frequent chromosomal abnormality detected. Since the consistent loss of a specific chromosomal region in a given tumor type most likely indicates the presence of a tumor related gene in that region, we undertook a combined molecular and cytogenetic approach to examine alterations of chromosome 17 in primitive neuroectodermal tumors. Seven of 14 tumors analyzed demonstrated loss of alleles for loci on 17p. In three of the seven tumors tested, a loss in copy number was observed for only the most telomeric locus on 17p13.3, D17S34. Limited sequence analysis of the same seven tumors did not reveal mutations in four highly conserved coding regions of the p53 gene. These data suggest a new tumor associated locus on 17p distinct from and distal to TP53, which is involved in the initiation or progression of at least a subset of primitive neuroectodermal tumors.

We have prepared karyotypes from a malignant fibrous histiocytoma (MFH) of the brain of a 6-year-old girl. Sporadic cases of MFH in the central nervous system have been reported. However, to our knowledge, this is the first central nervous system tumor to be subjected to cytogenetic analysis. The tumor demonstrated a complex karyotype, with a variety of numerical and structural abnormalities. Although no specific cytogenetic abnormality was observed, the karyotype of this case was similar to those reported for adult MFH of soft tissues.

Twenty children with meningiomas (ages 18 months to 17 years) received initial therapy at the Children's Hospital of Philadelphia between January 1975 and June 1991, accounting for 2% of children with primary brain tumors seen during that time interval. All were verified histopathologically, and none had had prior irradiation. Fifteen were male and 5 female. Fifteen tumors were intracranial, all located supratentorially. Two of these also had a component within the optic canal. One tumor was entirely within the orbit. Four meningiomas arose within the spinal canal. Associated conditions were neurofibromatosis (NF) type I (1 patient), NF type II (2 patients), and a facial alveolar rhabdomyosarcoma (1 patient). A gross total resection as documented by postoperative scan and operative note was accomplished in 12 patients. Four of these relapsed, at a mean of 3.5 years from initial surgery. In 4 patients a near-total resection (> 90%) was performed. Of these, 2 progressed at 9 months and 1.5 years. One of these died of complications associated with reoperation. In 4 patients a partial resection (50-90%) was performed. Two of these progressed at 4 months and 1 year, and the other 2 have been followed for less than 2 years. Five patients received radiation therapy (RT). One patient received RT as adjunctive therapy after primary surgery because of papillary histology. The other 4 had RT following reoperation for recurrence at a mean of 1.5 years from diagnosis (range, 7 months to 2 years). These 4 patients remain alive and with stable disease at a mean of 6 years from diagnosis (range 2-8.8 years).(ABSTRACT TRUNCATED AT 250 WORDS)

Cytogenetic studies of a rhabdomyosarcoma of mixed embryonal and alveolar histology in an 11-month-old male revealed a single structural abnormality, t(1;13)(p36;q14). This abnormality may define a subset of patients with a variant of the t(2;13)(q35;q14) translocation frequently seen in alveolar rhabdomyosarcoma.

We present cytogenetic and molecular genetic analyses of two cases of alveolar rhabdomyosarcoma. The characteristic translocation between chromosomes 2 and 13, t(2;13)(q35;q14), has been identified in both cases. Using cell lines derived from these tumor specimens, we have performed Southern blot analysis to investigate the possibility of rearrangement of 14 candidate genes mapping to the relevant regions of 2q and 13q. These candidate genes can be divided into 5 groups: signal transduction proteins (RB1, inhibin alpha, FLT1, and HOX4B), muscle-specific products [myosin light chain, desmin, and nicotinic cholinergic receptor subunits gamma and delta (CHRNG and CHRND)], extracellular matrix proteins (collagen type VI alpha 3 chain, elastin, and fibronectin), transformation-associated products (intestinal alkaline phosphatase and L-plastin), and other genes (esterase D). Conventional gel electrophoresis followed by Southern blot analysis indicated no evidence of rearrangement within or near these genes except for a rearrangement in the CHRNG-CHRND locus, which occurred only in a subpopulation of the late recurrence tumor cells of one patient. In addition, we employed pulsed-field gel electrophoresis-Southern blot analysis to demonstrate the absence of detectable rearrangements within a larger region around each of these genes.

Cytogenetic studies of three rare childhood brain tumors were performed. Two children presented with pure rhabdoid tumors. The third child had a tumor composed of a mixture of rhabdoid elements with neuroepithelial, epithelial, and mesenchymal tissue - an atypical teratoid tumor. All three tumors demonstrated monosomy 22 as the only cytogenetic abnormality. The cytogenetic findings suggest that loss of a gene or genes on chromosome 22 may be involved in the initiation or progression of these malignant tumors. Further studies on additional fresh tumor specimens are warranted; however, it is possible that cytogenetic studies may be used as an additional means of diagnosing rhabdoid or atypical teratoid tumors of the brain.

A primitive neuroectodermal tumor (PNET) presented as a cerebral hemispheric mass in a 33-year-old man. Bone marrow metastases were discovered 11 months later. A cell line (CHP707m) was derived from these metastases. In culture, the cells showed features of neuronal differentiation, forming short neurites and synthesizing low-molecular-weight neurofilament protein. Northern blotting showed the tumor cells express nerve growth factor (NGF) receptor messenger RNA, and fluorescence-activated cell-sorting demonstrated NGF receptors on the cell surface. Western blotting showed CHP707m NGF receptors are truncated. The receptors are functional; they bind iodine 125-labeled mouse NGF with an affinity of 1.6 x 10(-9) M, and short-term treatment with NGF induces expression by the tumor cells of the proto-oncogene, c-fos. Although CHP707m is the first central nervous system PNET cell line proven to express NGF receptors, immunohistological survey of tissue sections prepared from human central nervous system PNETs showed that 13 of 35 contained NGF receptor-positive tumor cells. Thus, more than one-third of such tumors might be responsive to the effects of NGF.

A path probability model is described for evaluation of sister-chromatid exchanges (SCEs) induced by alkylating agents following treatment of G1 cells at the beginning of the first or second cycles of BrdUrd incorporation, or during G1 corresponding to an exact cell-cycle interval preceding BrdUrd incorporation. Algebraic expressions are derived for calculations of expected induced SCE frequencies (over baseline levels) in second and third (reciprocal and nonreciprocal SCEs) division cells for the described treatment protocols. The derivations take into consideration: p, the probability of a specific lesion inducing an SCE; rn, the extent of repair within the nth post-treatment cycle; and X, the number of lesions induced. Expressions are also derived for expected ratios of single: twin exchanges in endoreduplicated or tetraploid cells.

The existence of an AKR subline, AKR(Rb6.15)1A1d, with a chromosome marker provided a means to differentiate between proliferating lymphoma and normal cell populations within a single animal. An AKR(Rb6.15)1A1d lymphoma cell line has been maintained for 6 yr by serial passage in AKR/J recipients. The mice die in 7 +/- 2.0 days with evidence of extensive infiltration of the tissues by lymphoma cells. Cytogenetic analysis showed that approx. 1% of the metaphase cells in the bone marrow of mice at day 1 of the lymphoma passage were of the AKR(Rb6.15)1A1d donor-type. This increased to 54% by day 4 and 96% by day 6. The number of donor-type metaphase cells per humerus increased from 3.4 +/- 0.29 (X 10(3] at day 1 to 2.0 +/- 0.49 (X 10(5] at day 4 with a concomitant decrease in the number of non-lymphoma host-type metaphase cells. The population doubling time of donor-type metaphase cells per humerus was 12 +/- 1.4 h. At day 4, there was a significant decrease in the percentage of donor-type metaphase cells in mice that had been treated with BCNU (19.0 +/- 5.85%) or spirogermanium (38.6 +/- 5.85%) 24 h earlier. For BCNU treated animals, this also represented a decrease to 4.4 +/- 1.1 (X 10(4] donor-type metaphase cells per humerus.

The recent development of an AKR(Rb6.15)1Ald lymphoma model in our laboratory presents a unique means of comparing sister chromatid exchange (SCE) frequencies and cellular replication kinetics of normal and lymphoma cells in the same host environment. Lymphoma cells, distinguished from normal cells by the presence of two metacentric chromosomes, had an average cell cycle time of 8 hr compared to 11 hr for normal cells. Normal bone marrow cells from nonleukemic AKR/J, nonleukemic AKR(Rb6.15) Ald, and tumor passage recipients had similar baseline and 1,3-bis(2-chloroethyl)-1-nitrosourea-induced SCE frequencies following exposure to 4.4 mg 1,3-bis(2-chloroethyl)-1-nitrosourea per kg and 19 hr 5-bromo-2-deoxyuridine. While baseline SCE frequencies were only slightly higher, 1,3-bis(2-chloroethyl)-1-introsourea-induced lymphoma cell SCE frequencies were 3 times higher than normal induced SCE frequencies [34.06 +/- 6.6 (S.E.) versus 11.0 +/- 0.6 SCEs/cell].

The four permanent human glioma-derived cell lines reported here are the first such lines for which the karyotypes have been followed from the original biopsies through the establishment of the lines in culture. Although ploidy changes were seen, each line retained either distinctive marker chromosomes or the overall original chromosomal distribution allowing the origin of each line to be established with certainty. D-263 MG expresses glial fibrillary acidic protein, all lines except D-245 MG are tumorigenic in athymic mice, and each line displays a unique pattern with respect to in vitro growth parameters and expression of biochemically defined markers, oncofetal antigens and lymphoid-associated markers. D-245 MG and D-259 MG are able to grow in the absence of supplemental glutamine; glutamine synthetase was detected in these cell lines both by immunocytochemistry and by direct assay. Thus, the four permanent human glioma-derived cell lines described here are representative of glioma lines in their general characteristics. D-259 MG retains numerous double minute chromosomes (DMs), D-263 MG contains two marker chromosomes with breaks in 9p, and D-247 MG and D-245 MG with stemlines containing 96 and 89 chromosomes contain eight and six normal copies (respectively) of chromosome No. 7. The retention in these four cell lines of the most common chromosomal abnormalities seen in biopsies of malignant human gliomas provides the opportunity to investigate the meaning of these specific chromosomal changes.

Cytogenetic analysis was performed on eight osteosarcomas, including six primary untreated biopsies, one second primary in a patient with a history of undifferentiated sarcoma, and one recurrent lung metastasis. Two primary tumors and the peripheral blood lymphocytes from all eight patients had normal karyotypes. Six of the tumors demonstrated extremely complex karyotypes, with modal numbers in the hypodiploid, triploid, and hypertetraploid ranges. The predominant types of structural abnormalities observed were nonreciprocal translocations and deletions, which differed between cases. A consistent loss of normal chromosome 13 homologs was evident in the six cases with abnormal tumor karyotypes; however, chromosomal loss was not restricted to #13. Molecular studies of osteosarcoma, especially with regard to the retinoblastoma locus on chromosome 13, should take into consideration the complex cytogenetic changes seen in this tumor.

We report here the clinical and cytogenetic findings in a 3-year-old girl with pre-B-cell acute lymphoblastic leukemia presenting as a primary tumor of bone. A unique translocation t(7;15)(q22;q14-15) is described.

The effect of spirogermanium (SG) on hematopoietic stem cells, tumor burden, and survival times was investigated in C3H mice with transplanted mammary carcinoma. Compared to normal mice, the number of hematopoietic stem cells, or colony-forming units per spleen (CFU-S), was lower in the marrow of tumor-bearing mice. Spirogermanium at 15 and 30 mg/kg was not toxic to the normal hematopoietic cells in the marrow of either normal or tumor-bearing mice. In contrast to animals treated with cyclophosphamide, SG did not decrease the tumor growth rate or prolong the survival times of tumor-bearing C3H mice. Doses of 35-40 mg/kg SG did not prolong the survival times or decrease the tumor burden of AKR/J mice with a long-passaged lymphoma. These studies demonstrate that SG has minimal inhibitory effects to the marrow of normal mice and may promote the maintenance of normal marrow cells in tumor-bearing animals. However, in two different transplanted tumor cell lines, SG did not inhibit tumor growth or prolong host survival time.

The present studies were designed to evaluate the role of cell cycle time and time of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) administration on the persistence of sister chromatid exchange (SCE)-inducing lesions in normal and lymphoma second- and third-division AKR bone marrow cells. Normal second-division cells harvested from mice given injections of BCNU at the start of an 18-, 24-, or 28-hr 5-bromo-2-deoxyuridine (BrdUrd) infusion exhibited similar linear dose-dependent increases in SCE frequencies (p greater than 0.05). The faster-cycling lymphoma cells, harvested after 18-hr BrdUrd infusion, had significantly higher baseline (p less than 0.05) and BCNU-induced increases (p less than 0.001) in SCE frequencies than did normal cells. Dose-dependent increases in SCE frequencies were demonstrated in third-division normal and lymphoma cells from mice infused with BrdUrd for 24 or 28 hr. Whereas lymphoma cells from mice treated with 3.3 mg BCNU per kg exhibited 31.2 +/- 3.9 (S.E.) SCEs in second-division cells and 4.7 +/- 0.4 reciprocal and 22.9 +/- 2.0 nonreciprocal SCEs in third-division cells, a 5 times higher dose of BCNU was required to induce similar levels of 30.0 +/- 0.8 SCEs in second-division cells and 4.4 +/- 0.6 reciprocal and 22.6 +/- 1.2 nonreciprocal SCEs in third-division normal cells. BCNU dose-dependent increases in SCE frequencies were also observed following injection of BCNU 8 hr after the start of BrdUrd infusion. The unexpectedly higher levels of SCEs for both normal and lymphoma cells by this treatment protocol may be due to SCEs occurring at the same site in successive divisions in BrdUrd. Regardless of the protocol used, lower nonreciprocal SCE frequencies were observed in third-division cells relative to SCE frequencies in second-division cells; a possible consequence of the cytotoxicity of BCNU. Injection of BCNU produced significant changes in the proportions of normal and lymphoma cells completing one, two, and three or more divisions in BrdUrd. Lymphoma cells were consistently more sensitive to the specific type(s) of BCNU-induced damage leading to SCEs and cell death than were normal cells. These studies indicated that differences in SCE response were not due to cell cycle time, time of drug administration, or potential for repair. It is therefore suggested that increased sensitivity of lymphoma versus normal cells may be due to increased cellular uptake of BCNU.

Karyotypic studies of human gliomas are often limited by a low mitotic index and the appearance of contracted chromosomes that do not exhibit clear banding patterns. The purpose of this study was to investigate the use of hydroxyurea (HU) as a synchronizing agent using established human glioma cell lines as a model system. HU was shown to reversibly inhibit cellular replication in glioma cell lines U-251MG, D-245MG, D-247MG and D-263MG by flow cytometry on the basis of DNA content. Two-to sixfold increases were demonstrated in the mitotic index of HU-treated cultures exhibiting the greatest percentage of cells in the G2/M phases of the cell cycle. HU, therefore, promises to be an effective agent for use in short term cultures from biopsied human tumors to increase the quality of chromosome preparations in these tumors.

Seven human medulloblastomas (four primary cerebellar, three recurrent or metastatic) were karyotyped in direct preparation and/or short-term or early culture. One tumor had a 46,XX stem line. Four of the six remaining tumors contained one or more i(17q), and three of these six tumors had deletions of extra copies of chromosome #1, resulting in trisomy of 1p, 1q, or both. Two tumors had near-centromeric breaks of chromosome #3, two tumors contained unbalanced translocations with breakpoints at 20q13, and two tumors contained double minutes. These findings suggest that the primary karyotypic deviations of human medulloblastomas are gains of whole chromosomes, which are then either deleted or involved in unbalanced translocations, resulting in partial trisomies.

We have prepared karyotypes from 22 primitive neuroectodermal tumors (PNETs) from pediatric patients ranging in age from 10 months to 16 years. Twenty-one cases were newly diagnosed, primary, posterior fossa tumors. One case was a recurrent tumor in a patient previously treated with radiation. Cytogenetic results were obtained from direct preparations and/or short-term (1-10 day) culture. Three tumors had apparently normal karyotypes. Nineteen tumors demonstrated numerical and/or structural abnormalities. The most frequent structural chromosomal changes were deletions and nonreciprocal translocations. Four tumors contained double minutes. Several chromosomes appear to be nonrandomly involved in PNETs. These include chromosomes 5, 6, 11, 16, 17, and a sex chromosome. The most consistent change, however, was an i(17q), present in one-third (8/22) of the cases. Strikingly, in three of these eight tumors, the i(17q) was the only structural abnormality observed. An i(17q) is not specific for pediatric PNETs, as it is also seen in leukemias and other solid tumors. However, in PNETs it may be a primary change related to tumor development and/or progression. Clinically, there was no correlation of the cytogenetic findings with histologic features of the tumors, size of the tumor, extent of metastasis, or surgical resection.