RECURRENT GAIN OF CHROMOSOME ARM 7Q IN LOW-GRADE ASTROCYTIC TUMORS STUDIED BY COMPARATIVE GENOMIC HYBRIDIZATION

Consistent tumor-specific chromosomal aberrations have not been descri bed in low-grade astrocytic tumors. The most frequent genetic alterati ons are mutations of the TP53 tumor suppressor gene and/or loss of het erozygosity (LOH) on 17p that occur in about 30% of the cases in adult patients but that are uncommon in childhood tumors. We used comparati ve genomic hybridization (CGH) to map DNA copy number alterations in 1 8 primary low-grade astrocytic tumors (ten adult patients and eight ch ildren). A gain of chromosome arm 79 was the most frequent event detec ted in five of ten astrocytomas (50%) from adult patients, followed by DNA amplification on chromosome arm 8q and gain on 12p (two cases). L oss of chromosomal regions on 1p, 4q, and the X chromosome was observe d in two of ten cases each [including one patient afflicted with Turne r syndrome (45,X)]. In contrast, no consistent changes were observed i n low-grade astrocytomas in children. A loss of the X chromosome was t he sole aberration detected in two of eight cases using DNA extracted from normal brain tissue. The findings suggest that a gain of 79 is an early event in the initiation of astrocytomas in adult patients. The discrepant findings in low-grade astrocytic tumors in adults compared to tumors in children support the hypothesis that there might be diffe rent mechanisms responsible for tumor development. (C) 1996 Wiley-Liss , Inc.