Lack of isodisomy for chromosome 22 in disomic meningiomas.

Loss of one copy of chromosome 22 is the most prevalent chromosomal change in meningioma, indicative of a tumor suppressor on chromosome 22. Meningioma retaining both copies of chromosome 22 could be possibly be explained by isodisomy for a meningioma suppressor gene. To investigate whether the chromosomal situation in meningioma is consistent with this hypothesis, we studied 53 cases, using polymorphic probes localized on chromosome 22. loss of one copy of chromosome 22 was found in 14 cases when polymorphic DNA markers were used. Thirty-nine meningiomas studied by karyotyping and molecular probes retained both copies of chromosome 22. The majority of cases (30/39, or 77%) displayed heterozygous banding patterns, indicating the presence of heterologous copies of chromosome 22. Hence, our data provide no evidence for duplication of one parental homolog as a general mechanism in diploid meningioma.