Comprehensive molecular cytogenetic investigation of chromosomal abnormalities in human medulloblastoma cell lines and xenograft

Abstract

Cell lines and xenografts derived from medulloblastomas are useful tools to investigate the chromosomal changes in these tumors. Here we used G-banding, fluorescence in situ hybridization (FISH), spectral karyotyping (SKY), and comparative genomic hybridization to study 4 medulloblastoma cell lines and 1 xenograft. Cell line D-425 Med had a relatively simple karyotype, with a terminal deletion of 10q and amplification of MYC in double-minutes (dmins). FISH demonstrated that an apparent isochromosome (17q) by routine karyotyping was actually an unbalanced translocation between 2 copies of chromosome 17. Cell line D-556 Med also had a simple near-diploid stemline with an unbalanced 1;13 translocation resulting in a gain of 1q, an isochromosome (17q), and dmins. These findings were initially described using routine G-banded preparations, and FISH showed that the dmins were an amplification of MYC and the i(17q) was an isodicentric 17q chromosome. The other finding was confirmed by FISH, SKY, and comparative genomic hybridization. Cell lines D-721 Med and D-581 Med had complex karyotypic patterns that could be completely characterized only when FISH and SKY were used. Xenograft D-690 Med also had a complex pattern that FISH and SKY were helpful in completely elucidating. Interestingly, balanced reciprocal translocations were seen as well as complicated unbalanced translocations and marker chromosomes. Comparative genomic hybridization demonstrated only a deletion of 10q22-10q24, supporting the idea that despite the complexity of the chromosomal rearrangements, minimal alterations in the overall chromosomal content had occurred. This study demonstrates that routine cytogenetic preparations are adequate to describe chromosomal abnormalities in occasional medulloblastoma samples, but a broader spectrum of molecular cytogenetic methods is required to completely analyze most of these tumor samples.

Chromosomal heterogeneity and instability characterize pediatric medulloblastoma cell lines and affect neoplastic phenotype

“…Here, we identified many numerical and structural alterations in both cell lines evaluated, mainly chromosomal gain and structural rearrangement of chromosome 1 and 7. Likewise, cytogenetic studies performed in other MB cell lines and short-time cultures also have reported a high frequency of structural rearrangements on chromosomes 1, 7 and 17 (Bayani et al 2000;Aldosari et al 2002).…”

“…Nowadays, cell lines represent an effective tool to study tumor biology, including cytogenetic and molecular heterogeneity, neoplasic behavior, biological pathways of tumor maintenance, chemo-and radiosensitivity, as well as testing new targeted therapies (Keles et al 1995;Aldosari et al 2002). However, there are relatively few pediatric MB cell lines reported in the literature.…”

Molecular cytogenetic analysis in the study of brain tumors: findings and applications

“…Complex translocations involving several chromosomal partners were present, as were double minute chromosomes and unidentifiable marker chromosomes. The SKY studies conducted by our group 13 and others 5,52 have identified the frequent involvement of chromosomes 1, 2, 3, 7, 10, 13, 14, 17, 18, and 22 in simple and complex translocations, contributing to copy number changes in those chromosomes (Fig. 3).…”

“…The CGAP database describes 15 cases 1,22,50,69,71,147,165,175,196,202,203,228 of choroid plexus papilloma or carcinoma. The karyotypes are predominantly near-diploid, hypodiploid, or hypotriploid, and are characterized by whole chromosomal gains and losses; these include gains of chromosomes 5,6,7,8,9,12,15,18, and 20 and losses of chromosomes 1, 3, 10, 16, 17, 21, and 22. In two cases, 50,69 diploid karyotypes were characterized by structural changes, including translocations, deletions, inversions, and the presence of markers, which were present as subclones.…”

“…Of the 53 samples (including 17 nonfunctioning pituitary adenomas, 16 PRL-, nine ACTH-, nine GH-, and two TSH-secreting tumors), only eight had abnormal karyotypes (see CGAP website). Interphase FISH assays for centromeres 5,8,12, and X were performed in 31 cases, resulting in the detection of 17 cases with copy number changes in one or more of the chromosomes tested. Separate or combined trisomy of chromosomes 5, 8, and 12 were found in all 10 prolactinomas and in four of nine nonfunctioning pituitary adenomas, whereas the combined loss of chromosomes 5 and 8 was observed in one of six ACTHand one of six GH-secreting pituitary adenomas.…”