Monosomy 12p in a radiation-induced germ cell tumor

Cytogenetic study of six cases of radiation-induced meningiomas

It is known that, following radiotherapy, secondary cancer may occur after a long latent period. Few cytogenetic studies have been reported on tumors of the central nervous system occurring after radiotherapy. We report the cytogenetic study of six cases of radiation-induced meningiomas. In all cases, we observed the same chromosome abnormality, der(1)(1qter-->1p11::22q12-->22pter). SKY and CGH techniques allowed us to identify the chromosomal abnormalities. We suggest that a gene localized on 1p13 is involved in radiation-induced meningiomas.

Radiation-induced meningioma: a distinct molecular genetic pattern?

Radiation-induced meningiomas arise after low-dose irradiation treatment of certain medical conditions and are recognized as clinically separate from sporadic meningioma. These tumors are often aggressive or malignant, they are likely to be multiple, and they have a high recurrence rate following treatment compared with sporadic meningiomas. To understand the molecular mechanism by which radiation-induced meningioma (RIM) arise, we compared genetic changes in 7 RIM and 8 sporadic meningioma (SM) samples. The presence of mutations in the 17 exons of the neurofibromatosis type 2 (NF2) gene, which has been shown to be inactivated in sporadic meningiomas, was analyzed in RIM and SM using single-strand conformation polymorphism (SSCP) and DNA sequencing. In contrast to SM, which showed NF2 mutations in 50% of specimens, no mutations were found in RIM. In addition, Western blot analysis of schwannomin/merlin protein, the NF2 gene product, demonstrated protein levels comparable to normal brain in 4/4 RIM tumor samples analyzed. Loss of heterozygosity (LOH) of genomic regions, which were reported for SM, was also analyzed in all cases of RIM using 22 polymorphic DNA markers. Allele losses were found on chromosomes 1p (4/7), 9p (2/7), 19q (2/7), 22q (2/7), and 18q (1/7). From these observations we conclude that unlike sporadic meningiomas, NF2 gene inactivation and chromosome 22q deletions are far less frequent in RIM, and their role in meningioma development following low dose irradiation is less significant. Other chromosomal lesions, especially loss of 1p, possibly induced by irradiation, may be more important in the development of these tumors.

Cytogenetic study of eight new cases of radiation-induced solid tumors

Radiation-induced tumors were selected according to the criteria defined by Cahan (1948) for sarcomas. Cell cultures and/or xenografts in nude mice were performed with biopsies obtained from second primary tumors. Karyotypes of eight tumors were established after R-banding. After comparison with literature data on 15 other cases, two distinct cytogenetic patterns could be distinguished. One was characterized by polyclonal karyotypes, of which a large proportion were simple and carriers of balanced translocations. Another one was characterized by monoclonal chromosome alterations observed in highly aneuploid and complex karyotypes, in which many deletions were observed. These two different patterns could be related to the modality of metaphase harvesting. Polyclonal karyotypes were preferentially observed after long-term cultures, and monoclonal karyotypes after short-term cultures or xenografts. The following scheme of radiation oncogenesis is proposed: a) induction of recessive gene mutations including that of tumor suppressor genes; b) accumulation of genomic alterations in the irradiated tissue with aging, including deletions or mutations of normal alleles from mutated tumor suppressor genes; and c) loss of tumor suppressor gene function and initiation of a multistage tumor development and progression. Polyclonal abnormalities are assumed to exist in noncancerous cells which acquired radiation-induced chromosome aberrations.

Dosimetric and cytogenetic studies of multiple radiation-induced meningiomas for a single patient

No criteria are currently available to determine the spontaneous or radiation-induced origin of a malignant tumor occurring in a previously irradiated area. This study presents the dosimetric and cytogenetic analysis of meningiomas diagnosed in irradiated brain areas from a single patient and a discussion of the karyotypes of spontaneous meningiomas and radiation-induced tumors published in the literature.

Interphase cytogenetics on paraffin sections of paediatric extragonadal yolk sac tumours

Germ cell tumours in children are more often extragonadal than in adults and the most frequent type is the yolk sac tumour. Limited cytogenetic data exist on extragonadal yolk sac tumours in children. We applied in situ hybridization (ISH) to interphase cell nuclei of four paediatric extragonadal pure yolk sac tumours and one yolk sac tumour component of a mixed germ cell tumour using paraffin-embedded tissue sections. The panel of chromosome-specific DNA probes was selected on the basis of their relevance in adult germ cell tumours and consisted of five DNA probes specific for the (peri)centromeric regions of chromosomes 1, 8, 12, and/or 17, X and/or one DNA probe specific for the subtelomeric region of chromosome 1 (p36.3). Only one tumour failed to show numerical and structural chromosome aberrations with the DNA probes used. The other four had an increased incidence of numerical chromosome aberrations with an over-representation of at least one chromosome. The DNA indices determined in the paraffin-embedded tumour material correlated well with the in situ hybridization findings. In only a few cases were chromosomes over-represented, when compared with the corresponding DNA indices. Recently, we have shown that the short arm of chromosome 1 is a non-random site of deletion in paediatric gonadal pure yolk sac tumours. The occurrence of similar deletions in one extragonadal pure yolk sac tumour and in one yolk sac tumour component, in conjunction with two further ISH reports, suggests that the loss of gene(s) in this region is an important event in the pathogenesis of paediatric malignant germ cell tumours of nearly all sites.

Verification of isochromosome 12p and identification of other chromosome 12 aberrations in gonadal and extragonadal human germ cell tumors by bicolor double fluorescence in situ hybridization

A diverse group of gonadal and extragonadal human germ cell tumors (GCT) and GCT-derived cell lines was examined for the presence of an i(12p) marker chromosome and/or other abnormalities involving chromosome 12, especially 12p, by bicolor double fluorescence in situ hybridization (FISH). For this purpose three probes, pBS-12, M28, and p alpha 12H8, were used, allowing specific identification of the entire chromosome 12, its short arm, and its pericentromeric region, respectively. The presence of one or more copies of a genuine i(12p) chromosome could be demonstrated in three GCT of the testis, in one ovarian GCT, in one dysgenetic GCT, and in one extragonadal intracranial GCT. Moreover, additional aberrations involving chromosome 12 were shown to be present not only in i(12p) minus but also in i(12p) positive GCT. These data suggest that the occurrence of such aberrations may be a common, although less clearly perceptible and frequent, phenomenon in human GCT.

Cytogenetic abnormalities in an ossifying fibroma from a patient with bilateral retinoblastoma

Cytogenetic analysis of a cemento-ossifying fibroma from a patient with nonfamilial bilateral multicentric retinoblastoma revealed three reciprocal translocations with the karyotype 46,XY,t(1;18)(q21;q21.3),t(3;10)(p13;q22),t(6;11)(p22;p15). Routine and high-resolution cytogenetic analysis of peripheral blood leukocytes showed an apparently normal, 46,XY chromosome pattern with no deletion of chromosome 13. Molecular analysis demonstrated no gross differences in the retinoblastoma gene or the TP53 gene between constitutional and tumor DNA. This is the first cytogenetic analysis of a cemento-ossifying fibroma and the first report of this tumor in a retinoblastoma patient. The data may be added to the small, but growing literature on cytogenetic aberrations in benign tumors and may lend insight into genes involved in cell proliferation and neoplastic transformation.