Numerical aberrations of chromosomes 1, 2, and 7 in astrocytomas studied by interphase cytogenetics

For both juvenile astrocytomas and astrocytomas of adults, numerical and structural aberrations of chromosomes 1 and 7 have been described. To study the frequency of those aberrations in more detail and to exclude in vitro artifacts, we investigated directly prepared material from 18 juvenile and 26 astrocytomas of adults by fluorescence in situ hybridization with DNA probes specific for chromosome regions 1p36, 1q12, 2cen, and 7cen. Chromosome 2 was used as control in the hybridization with chromosome 7. To exclude tissue-specific alterations, we tested cerebral and cerebellar paraffin-embedded material from persons who had died from other diseases. In 13 of the juvenile astrocytomas, we found a loss of 1p36 in relation to 1q12 in 16 astrocytomas of adults, a gain of signals from 1p36 or both probes for chromosome 1 was seen. Gain of chromosome 7 was found in 25 cases. Unexpectedly, gain of chromosome 2 occurred in 32 cases. For both probes, there was no difference between astrocytomas of children and those of adults. Our data suggest that loss of 1p is an early event in the development of juvenile astrocytomas and that trisomy 7 is frequent in malignant tumors and tumors containing a potential of growing malignantly.