Loss of heterozygosity for DNA polymorphisms mapping to chromosomes 10 and 17 and prognosis in patients with gliomas

Genomic organization and mutation analysis of p73 in oligodendrogliomas with chromosome 1 p-arm deletions

p73, a protein having substantial structural and functional similarity to p53, has recently been identified and demonstrated to be a potential tumor suppressor. Its location on human chromosome 1p36.33 implicates p73 as a candidate for neuroblastoma. Like neuroblastoma, oligodendrogliomas also show a high frequency of deletions in chromosome 1p36.3. To determine whether p73 is a potential tumor suppressor gene involved in the development of oligodendrogliomas, we performed mutation analysis of p73 in oligodendrogliomas with chromosome 1 p-arm deletions. We first determined the genomic organization and the intron-exon boundary sequences of the p73 gene by long PCR, vectorette PCR, and Southern hybridization. This gene spans about 65 kb with a large first intron. Primer pairs for the amplification of each of the 13 p73 encoding exons were designed in corresponding introns. The amplicons were then analyzed using the denaturing high-performance liquid chromatography system for mutations in the p73 gene. Twenty oligodendroglioma samples with 1p36.3 deletions were screened, but no mutations were detected except for several polymorphisms. It is thus clear that p73 is not a candidate gene for oligodendroglioma despite its location in the frequently deleted 1p36.3 region.

Loss of heterozygosity in clinical stage IB cervical carcinoma: relationship with clinical and histopathologic features

Loss of heterozygosity (LOH) has been shown to be an important prognostic factor in a variety of malignant neoplasms. The relationship between LOH and established histopathological prognostic factors in cervical carcinoma has not been examined. We studied LOH in 58 FIGO stage IB cervical cancers treated by radical hysterectomy. In a randomly selected subset of 37 of these cases, LOH was examined using markers for all 41 chromosomal arms. Seventy-six percent of the 58 cases and 95% of the extensively studied cases showed LOH at one or more loci. The three most common sites of LOH were 3p21, 6p24-p23, and 11q23.3. In the extensively studied group, LOH on 11q was associated with extensive lymphvascular space invasion (P = .009) and less deeply invasive tumor (P = .042). There was a trend for tumors with LOH on 11q to recur, but this was not statistically significant. No correlation between the presence of LOH on 3p or 6p and lymphvascular space invasion or tumor depth was present. There was no correlation between the number of sites of LOH or between the presence of LOH on 3p, 6p, and 11q and the presence of metastatic tumor in regional lymph nodes, histologic type (squamous v nonsquamous), tumor differentiation, maximum tumor size, degree of inflammation, pattern of invasion, mitotic rate, or clinical recurrence. In summary, tumors with 11q LOH may behave in a more aggressive fashion. Future studies of LOH in cervical carcinoma should include histopathological prognostic information so that the relationship between LOH and these factors can be determined on larger numbers of patients.

Non-isotopic molecular cytogenetics in neuro-oncology

The molecular genetic analysis of brain tumours has been the focus of considerable interest for a number of years. However, these studies have been largely directed towards understanding the fundamental biological processes involved in tumorigenesis and the techniques which have been used require considerable molecular biological skills. Unfortunately, there has not been the impetus to correlate basic biological studies with clinical or neuropathological features. The development of non-isotopic molecular cytogenetic in situ hybridization (ISH) techniques which can be applied to archival tumour material provides an opportunity to address a wide range of neuropathological questions at a genetic level. Identification of specific chromosomes has been made possible by the isolation of probes which recognize the highly repeated sequences present in the centromeric regions of individual chromosomes. Libraries of human chromosome-specific painting probes are also available. A range of probes which bind to the whole or part of specific single copy genes are becoming available. These can be detected with either fluorochromes with different emission colours or with enzymatic detection systems in either interphase nuclei derived from fresh, fixed and embedded tumour samples, touch preparations or smears (so-called 'interphase cytogenetics') as well as conventional metaphase spreads. Comparative genomic hybridization can be used to scan the entire genome for deletions or amplifications without any pre-existing information about the likely locations of these abnormalities or the availability of any specific DNA probes. These techniques can be used to identify aneuploidy or structural alterations in individual chromosomes and are likely to yield important information about the location of genes important in the pathogenesis of brain tumours and may also provide the basis for the refinement of diagnostic or prognostic criteria of these neoplasms.

Current perspectives in gliomas

The annual incidence of primary central nervous system tumors, including gliomas, is increasing, however, the prognosis of these tumors remains poor with a median survival of only 5 years. The imaging of tumors by computerised tomography, magnetic resonance imaging and newer methods such as positron emission tomography and proton magnetic resonance spectroscopy (1H-MRS) is increasing our knowledge of tumor biology and extent of the disease. Advances within the field of neurosurgery have improved operative procedures reducing mortality and morbidity. Furthermore, radiotherapy planning, tumor targeting and repositioning for treatment have all improved initial tumor management. The role of adjuvant chemotherapy remains controversial. Chemotherapy for advanced and recurrent disease has been extensively investigated, and although improvements in quality of life have been recorded, no prolongation of survival has been documented. With new discoveries and increasing knowledge of the physiology and molecular biology of these tumors the potential for targeting therapy at a genetic level is becoming increasingly promising. This review provides an overview of these current perspectives in glioma management.

Frequent loss of heterozygosity for markers on chromosome arm 10q in chondrosarcomas

Many tumors exhibit loss of heterozygosity (LOH) for polymorphic markers in regions of the genome that contain genes whose normal function can suppress tumor growth. Mapping of regions of LOH can help identify putative tumor suppressor loci that play a role in the pathogenesis of a disease. We evaluated 18 chondrosarcomas for LOH at 17 short tandem-repeat polymorphism loci on chromosome 10. Sixty-seven percent of the tumors (12/18) showed LOH for at least one marker and in most of these tumors the region of loss spanned all or large portions of the chromosome. By determining the smallest segment consistently involved, we identified a 7-12 cM critical region for LOH in the proximal long arm. This genomic region contains the RET oncogene, which has been implicated in the pathogenesis of multiple endocrine neoplasia types 2A and 2B, Hirschsprung disease, and medullary and papillary thyroid carcinomas. LOH on chromosome arm 10q was found in early-stage chondrosarcomas and did not correlate with grade or prognosis. Inactivation or alteration of a gene located at this site may be an early event in the development of these tumors.