Figure 1.
Ploidy levels of cytogenetically analyzed chondrosarcomas of bone.
To date, 138 chondrosarcomas of bone with an aberrant karyotype (excluding myxoid chondrosarcomas and 45,X,-Y) have been published (Mitelman Database of Chromosome Aberrations and Gene Fusions in Cancer: http://cgap.nci.nih.gov/Chromosomes/Mitelman June 1, 2010). The ploidy levels vary from hyperhaploid to hyperhexaploid. In 39 of the cases rearranged chromosomes in at least two copies and/or a doubled clone were found, supporting polyploidization of chondrosarcoma cells.
Figure 2.
Genomic aberrations detected in 16 chondrosarcomas.
Genomic loss, uniparental disomy (UPD) and gain of one or two copies identified by SNP array analysis are displayed for all autosomes. Loss of heterozygosity resulting from deletion or UPD was frequently found, except for chromosomes 5, 7, 19, 20 and 21. Detailed information on all aberrations affecting each individual case is shown in Figs. S1, S2, S3, S4. The imbalance map was created using the freely available software Genome Wide Viewer (http://www.well.ox.ac.uk/~jcazier/GWA_View.html).
Figure 3.
Inferred polyploidization events of hyperhaploid-hypodiploid chondrosarcoma cells affected by CDKN2A deletions.
Polyploidization of hyperhaploid-hypodiploid chondrosarcoma cells was supported by the combined SNP array and cytogenetic findings. Hyperhaploid-hypodiploid clones were detected in eleven cases. In four of these and in five additional cases chromosome aberrations supporting polyploidization was found. Polyploidization may occur more than one time and the cells may be affected by further rearrangements, gains and losses of genetic material. In case 14, a hypodiploid chromosome number was detected and uniparental disomy was shown for several of the disomic chromosomes. The detected pattern of aberrations in this case suggested a potential developmental step with duplication of some monosomic chromosomes and did not support polyploidization of a hyperhaploid cell. In cases 2 and 16, the detected pattern of preserved heterozygosity for the vast majority of chromosomes indicates that the tumor cells never had been hyperhaploid or hypodiploid and that polyploidization affected diploid cells with both parental alleles retained. In these two cases CDKN2A was not affected by deletion, whereas in the remaining cases the gene was hemi- or homozygously lost. Cases in which clones of two ploidy levels were detected are indicated by asterisks.
Figure 4.
Ploidy levels of mono- and binucleated chondrocytes.
Combined immunofluorescence and fluorescence in situ hybridization analyses were used to detect the ploidy levels of mono- and binucleated chondrocytes. To visualize individual cells a plasma membrane marker was detected by a fluorescently labeled antibody (green). Centromeric probes specific for chromosomes known to be monosomic (pink) and disomic (yellow) in hypodiploid cells and consequently disomic (pink) and tetrasomic (yellow) in hypertriploid cells were used for detection of ploidy levels. (A) Normal diploid nuclei as well as (B) hypodiploid nuclei are shown in binucleated cells (case 17). Mononuclear cells display (C) hypodiploid, (D) normal and hypertriploid nuclei (cases 18 and 15, respectively). The proportion of binucleated chondrocytes was 1–10% of all cells investigated with normal, hypodiploid and hypertriploid nuclei (Table S2). In binucleated cells both nuclei displayed the same ploidy level.