Flow-cytometric quantification in human gliomas of alpha satellite DNA sequences specific for chromosome 7 using...

Cell suspensions prepared from freshly frozen tissue specimens were used to examine aberrations in the number of chromosome 7 signals in 10 human gliomas. Nuclear DNA was hybridized in vitro with an alpha satellite DNA probe specific for the centromeric regions of chromosome 7, using fluorescence in situ hybridization (FISH). The intensity of the fluorescence signal from the hybridized probe was measured, together with the nuclear DNA content, by flow cytometry. The mean probe fluorescence of all nuclei was compared to the mean copy number per nucleus found with microscopic scoring. Moreover, the mean probe fluorescence ratio of DNA aneuploid nuclei relative to DNA diploid nuclei (FISHa/FISHd) was calculated to determine how the numerical aberration of chromosome 7 signals contributes to the DNA ploidy of the sample. The results from the flow-cytometric analysis and from microscopic evaluation were compatible. One of four tumors with DNA diploidy had a higher average intensity of FISH signal and a broader coefficient of variation in FISH signal than normal brain tissue; this was shown to be due to the gain of chromosome 7 signals. Although FISHa/FISHd correlated with DNA indices (P < 0.01), there were some disparities, probably due to other complex genotypic associations involving several gains or losses of chromosomes. Thus gain of chromosome 7 in gliomas is related to both DNA ploidy change and chromosome specific gain. It is concluded that flow-cytometric quantification of FISH is useful in investigating numerical aberrations of chromosomes and nuclear DNA content simultaneously.