ASCERTAINMENT OF CHROMOSOME-7 GAINS IN MALIGNANT GLIOMAS BY CYTOGENETIC AND RFLP ANALYSES

The incidence of gains involving chromosome 7 was determined independe ntly using cytogenetic and molecular genetic analyses in a series of 5 7 malignant gliomas. Coincidental results were observed in the group o f tumors in which trisomy 7 was identified on the same cells their als o displayed other clonal abnormalities (i.e., losses of chromosome 10, and structural rearrangements of 1p, 9p, etc., and the presence of dm in). On the other hand, molecular detection of gain of material from t his chromosome was obtained in only one of nine cases in which trisomy 7 had been identified os a solitary anomaly at the cytogenetic level. Thus, although trisomy 7 has been identified as a clonal abnormality in about 60% of gliomas analyzed cytogenetically so far, our findings suggest that the anomaly may be representative of tumor parenchyma in half of them, while in the remaining cases (mainly those in which tris omy 7 is observed at the cytogenetic level as the sole chromosomal dev iation) our data agree with those suggesting that the anomaly is the r esult of an in vitro non-disjunction, or represent in vivo mosaicism o f the non-tumoral cells.