Down syndrome is a multiple malformation syndrome due to the trisomy of chromosome 21. There is epidemiological evidence that individuals with Down syndrome are at decreased risk for solid tumors including brain tumors. It has been suggested that some genes expressed on the extra copy of chromosome 21 act as tumor suppressor genes and contribute to the protection against tumorigenesis.
Yamamoto et al. report the first Down syndrome patient, an 8-year-old boy, with a meningioma in the posterior fossa. The diagnosis was based on histological study of the surgically resected tumor. Postoperatively his neurological status improved and there was no tumor regrowth in the next 2 years. Fluorescence in situ hybridization (FISH) for chromosome 22 confirmed high allele loss involving the NF2 gene locus, a finding typical in meningiomas. FISH also revealed chromosome 21 heterogeneity in tumor cells; not only cells with trisomy 21 but also cells with disomy and monosomy 21 were present. All blood cells from the patient manifested trisomy 21.
Our finding suggests that deletion of the chromosome 21 allele may be associated with the tumorigenesis of meningioma in Down syndrome. It supports the hypothesis that some genes whose expression is increased on the extra copy of chromosome 21 function as tumor suppressor genes and that they contribute to the reduced tumor incidence in individuals with Down syndrome 1).