Chromosome 9 deletion mapping reveals interferon alpha and interferon beta-1 gene deletions in human glial tumors.

We have applied restriction fragment length polymorphism analysis to a 30-member panel of primary glioma DNAs, which had been previously examined for loss of genetic information (C. D. James, E. Carlbom, J. P. Dumanski, M. Hansen, M. Nordenskjold, V. P. Collins, and W. K. Cavenee, Cancer Res., 48:5546-5551, 1988), to determine the frequency and sublocalization of loss of genetic information from chromosome 9. We have also utilized scanning densitometry for dosage determination of the 9p-localized interferon alpha and interferon beta-1 genes among these same tumors. Our results reveal the following: (a) for those cases in which loss has occurred, the region of common loss lies on the short (p) arm of the chromosome; (b) loss of genetic information from the short arm of chromosome 9 occurs frequently in glial tumors of intermediate (anaplastic, grade III) and high (glioblastoma, grade IV) histological malignancy (10 of 20 cases) but not in tumors of low (grade II) histological malignancy (0 of 10 cases); (c) tumors with 9p deletions are hemi- or nullizygous for interferon beta-1 and the interferon alpha gene cluster; (d) cases of interferon nullizygosity occur exclusively among tumors of highest histological malignancy (glioblastoma). These data, especially the determination of a region of nullizygosity, suggest proximity to or residence within a gene(s) whose function(s) is (are) critical to the suppression of the malignant evolution of glial tumors.

Clonal genomic alterations in glioma malignancy stages.

Comparison of constitutional and tumor genotypes at chromosomal loci defined by restriction fragment length alleles has proven useful in determining the genomic position and tissue specificity of recessive mutations that predispose to cancer (Hansen, M.F., and Cavenee, W.K. Cancer Res., 47:5518-5527, 1987). Here we have applied this approach to 53 unrelated patients with glial tumors of varying histological malignancy grade. Loss of constitutional heterozygosity for loci on chromosome 10 was observed in 28 of 29 tumors histologically classified as glioblastoma (malignancy grade IV) whereas no similar losses were observed in any of 22 gliomas of lower malignancy grade. Examination of restriction fragment length alleles on other chromosomes revealed that loss of sequences on chromosomes 13, 17, or 22 had occurred at nonrandom frequencies and in at least one instance of each malignancy grade of adult glioma. The tumors in which loss of constitutional heterozygosity was observed were composed of one or a mixture of glial cell subtypes displaying astrocytic, oligodendrocytic, and/or ependymal differentiation. These results demonstrate a close association of the loss of chromosome 10 sequences with the most malignant histological stage of glioma and that glioblastoma arises as the clonal expansion of an earlier staged precursor. Furthermore they suggest that glioblastoma is a common phenotypic and malignancy terminus for glial tumors of various cellular subtypes which is reached through a common molecular pathway. This approach which involves the identification of malignancy stage specific somatic losses of heterozygosity provides a genotypic, rather than phenotypic, analysis of tumor progression.

Mitotic recombination of chromosome 17 in astrocytomas.

Allelic combinations at seven loci on human chromosome 17 defined by restriction fragment length polymorphisms were determined in tumor and normal tissues from 35 patients with gliomas. Loss of constitutional heterozygosity at one or more of these loci was observed in 8 of the 24 tumors displaying astrocytic differentiation and in the single primitive neuroectodermal tumor examined. The astrocytomas showing these losses included examples of each adult malignancy grade of the disease, including glioblastoma (malignancy grade IV), and seven of them demonstrated concurrent maintenance of heterozygosity for at least one chromosome 17 locus. Determination of allele dosage together with the genotypic data indicated that the tumor chromosomes 17 were derived by mitotic recombination in 7 of the 9 cases with shared homozygosity of the region 17p11.2-pter in all cases. In contrast, tumors of oligodendrocytic, ependymal, or mixed cellular differentiation did not exhibit loss of alleles at any of the loci examined. These data suggest that the somatic attainment of homozygosity for loci on chromosome 17p is frequently associated with the oncogenesis of central nervous system tumors, particularly those showing solely astrocytic differentiation, and that mitotic recombination mapping is a useful approach towards the subregional localization of a locus whose rearrangement is involved in this disease.

Deletion mapping of a locus on human chromosome 22 involved in the oncogenesis of meningioma.

The genotypes were analyzed at 11 polymorphic DNA loci (restriction fragment length alleles) on chromosome 22 in tumor and normal tissue from 35 unrelated patients with meningiomas. Sixteen tumors retained the constitutional genotype along chromosome 22, while 14 tumors (40%) showed loss of one constitutional allele at all informative loci, consistent with monosomy 22 in the tumor DNA. The remaining 5 tumors (14%) showed loss of heterozygosity in the tumor DNA at one or more chromosome 22 loci and retained heterozygosity at other loci, consistent with variable terminal deletions of one chromosome 22 in the tumor DNA. The results suggest that a meningioma locus is located distal to the myoglobin locus, within 22q12.3-qter. Multiple loci on other chromosomes also were studied, and 12 of the 19 tumors with losses of chromosome 22 alleles showed additional losses of heterozygosity at loci on one to three other chromosomes. All tumors that retained the constitutional genotype on chromosome 22 also retained heterozygosity at all informative loci on other chromosomes analyzed, suggesting that the rearrangement of chromosome 22 is a primary event in the tumorigenesis of meningioma.

Loss of genetic information in central nervous system tumors common to children and young adults.

The clonal loss of genetic information as revealed by the comparison of normal and tumor DNA restriction fragment length alleles has permitted the determination of the genomic positions of cancer-recessive mutations. Here we have applied this approach to the analysis of 19 central nervous system tumors that constitute four histologic groups and occur most frequently in children and young adults. The detectable loss of genetic information from cases of medulloblastoma (11 examined) indicates that among such tumors, loss occurs most frequently from the short arm of chromosome 17. For the ependymomas examined (four cases), chromosome 22 was the preferred site for detectable loss. Analysis of pilocytic astrocytomas of the cerebellum (three cases) failed to reveal genetic alterations of any type among such tumors, a finding unique to this histologic group. The single choroid plexus papilloma examined demonstrated loss of genetic information from chromosome 3. Among the 19 tumors, multiple cases of loss were observed from chromosomes 10, 11, 13, and 22, and from the short arm of chromosome 17. Therefore, with regard to the chromosomal locations of implied tumor suppressor genes, these results are consistent with those described for intracranial tumors occurring more commonly in adults of middle to advanced age.

Identification of twelve new RFLP-markers on chromosome 22q11-qter.

We have previously identified and regionally localized 195 chromosome-22-specific DNA markers. We now report restriction fragment length polymorphisms detected by 9 phage markers mapped to 22q11-q12, two cosmid clones mapped to 22q12-q13 and one plasmid mapped to 22q13-qter. These markers may be useful tools for mapping disease genes such as the NF2 locus, on chromosome 22.

A map of 22 loci on human chromosome 22.

We constructed a genetic linkage map of the entire long arm of human chromosome 22 with 30 polymorphic markers, defining 22 loci. The map consists of a continuous linkage group 110 cM long, when male and female recombination fractions are combined; average distance between the loci is 5.2 cM. All loci were placed on the map with high support against alternative orders (odds in excess of 1000:1). The order of loci presented in our map is in full agreement with that of the previous linkage maps of chromosome 22 and with the physical assignment of markers. Two markers included in this map, KI-831 (D22S212) and pEFZ31 (D22S32), allowed us to better define the region of the (11;22) translocation breakpoint specific for Ewing sarcoma. Ten additional polymorphic markers were placed on the 22-loci map with odds lower than 1000:1 against alternative locations. In total, we have introduced 29 new markers on the linkage map of chromosome 22.