Simultaneous paired analysis of numerical chromosomal aberrations and DNA content in osteosarcoma

Relatively little is known about the biologic relevance of numerical chromo somal changes in relation to DNA content in osteosarcoma In this study, by using a series of human osteosarcoma cell lines, we standardized a method f or the assessment, on the same nuclei specimen, of both specific chromosome copy numbers by fluorescence in situ hybridization (FISH) and the DNA cont ent by static cytofluorometry or image cytometry. On the same cell lines, w e also evaluated the DNA content by using now cytometry and the chromosome number distribution by metaphase analysis. Comparison between these differe nt methods showed that DNA ploidy level as determined by FISH or metaphase analysis is frequently lower than the ploidy pattern as defined by cytometr ic methods. By using comparative genomic hybridization, we were able to dem onstrate that these discrepancies were due to the presence of several unbal anced chromosome aberrations, specifically gains and high-level amplificati ons, which affect the total DNA content with less effect on the total chrom osome number. Thus, evaluation of DNA ploidy in osteosarcoma cells is neede d for a correct interpretation of FISH or cytogenetic data concerning numer ical chromosomal changes. Evaluation of turner ploidy in a series of clinic al samples demonstrated that in high-grade osteosarcoma, flow cytometry som etimes may give false results because of the presence of high proportions o f contaminating, nonneoplastic cells that cannot be excluded from the flow cytometric assessment but that do not interfere with the evaluation of DNA ploidy by static cytofluorometry or image cytometry, in which only tumor ce lls are selected for the analysis. The possibility of using this method to evaluate, on the same nuclei sample, both specific chromosomal aberrations and DNA ploidy may allow a better determination of numerical chromosomal ch anges that may be relevant for the biologic behavior of osteosarcoma.