Loss of heterozygosity for loci on chromosome 17p in human malignant astrocytoma.

Loss of constitutional heterozygosity for specific chromosomal loci, when found consistently in a particular tumor type, suggests that a recessive oncogene important in the genesis of that tumor may be present within the involved chromosomal loci. DNA markers that detect restriction fragment length polymorphisms are powerful tools that have been used to detect loss of chromosomal loci in a growing number of human malignancies. The human brain tumor astrocytoma is usually malignant and virtually incurable. Two types of malignant astrocytomas are recognized histopathologically:anaplastic astrocytoma and glioblastoma multiforme. We carried out a restriction fragment length polymorphism analysis of tumors from 15 patients with anaplastic astrocytoma and 20 patients with glioblastoma using polymorphic DNA markers for loci on chromosome 17. Loss of constitutional heterozygosity for loci on chromosome 17 was found in both anaplastic astrocytoma and glioblastoma patients with equal frequency (40% of cases). Our mapping data revealed a region of loss on chromosome 17p between physical loci p11.2 and pter that was common to both patient groups. Taken together with the previously reported finding of loss of heterozygosity for loci on chromosome 10 in glioblastoma, these results indicate that tumorigenesis in the astrocyte lineage may involve recessive oncogenes on two different chromosomes.