DNA content and chromosomes in permanent cultured cell lines derived from malignant human gliomas

DNA content, as determined by flow cytometry (FCM), and ploidy, as determined planimetrically from chromosomes, were measured for 17 established human glioma-derived cell lines. Values obtained by these methods corresponded well for two of two near-diploid lines, two of two hyperdiploid-hypotriploid lines, four of four hypertriploid-hypotetraploid lines, two of six hypertetraploid-hypopentaploid lines, the one hyperpentaploid line and two of two multiclonal lines. For the remaining four lines, ploidy values obtained by karyotyping were more than 10% lower than those obtained by FCM. Since karyotypic ploidy was determined by planimetric measurements of the chromosomes, which corrects for deviations in chromosome size, the lower values could not be explained by large marker chromosomes. Technical problems, such as random chromosomal loss in karyotypic preparations, adherent bits of cytoplasm in nuclear preparations for FCM or differences in nuclear stainability, are possible reasons for the discrepancies. Alternatively, chromosomes in some glioma cell lines may actually contain an increased amount of DNA. FCM and karyotyping provide complementary information in the initial evaluation of cultured cell lines. For sequential studies, such as are used for monitoring cultured lines, the rapidity of FCM makes it the more practical method.