LOSS OF CHROMOSOME-22 ALLELES IN HUMAN SPORADIC SPINAL SCHWANNOMAS

Acoustic neuromas occur either as sporadic solitary tumors in the general population or as inherited bilateral tumors typically in patients with neurofibromatosis type 2. Loss of heterozygosity for markers on the long arm of chromosome 22 has been reported in both instances, and neurofibromatosis type 2 has been genetically linked to a marker on the long arm of this autosome, suggesting that a unique locus on chromosome 22 is implicated in tumorigenesis of both sporadic and inherited acoustic neuromas. To determine whether the locus for neurofibromatosis type 2 might also be responsible for tumorigenesis of those schwannomas distinct from acoustic neuromas in people without neurofibromatosis type 2, we studied the DNA content of three sporadic spinal schwannomas. In all three, we found loss of heterozygosity for at least three markers on the long arm of chromosome 22, indicating a partial or total monosomy 22 in the tumor. Our results suggest that a locus on chromosome 22 is responsible for tumorigenesis in schwann cells regardless of their location in the central nervous system, and that some other mechanism (genetic or nongenetic) might account for the relative high proportion of schwannomas developing from the eighth cranial nerve.