An evaluation of the polymorphisms Ins16bp and Arg72Pro in p53 as breast cancer risk modifiers in BRCA1 and BRCA2 mutation carriers.

The close functional relationship between p53 and the breast cancer susceptibility genes BRCA1 and BRCA2 has promoted the investigation of various polymorphisms in the p53 gene as possible risk modifiers in BRCA1/2 mutation carriers. Specifically, two polymorphisms in p53, c.97-147ins16bp and p.Arg72Pro have been analysed as putative breast cancer susceptibility variants, and it has been recently reported that a p53 haplotype combining the absence of the 16-bp insertion and the presence of proline at codon 72 (No Ins-72Pro) was associated with an earlier age at the onset of the first primary tumour in BRCA2 mutation carriers in the Spanish population. In this study, we have evaluated this association in a series of 2932 BRCA1/2 mutation carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2.

Sequence variations of mitochondrial DNA and individual sensitivity to the ototoxic effect of cisplatin.

BACKGROUND: Since mutations in the mitochondrial genome are associated with hearing loss, we analyzed whether sequence variations of mtDNA are associated with individual sensitivity to cisplatin-induced ototoxicity. MATERIALS AND METHODS: The mtDNA of 20 patients with and 19 patients without hearing impairment under therapeutic doses of cisplatin was sequenced for mutations and characterized for haplotype by restriction analysis. RESULTS: Neither the A7445G mutation, nor the 7472insC insertion or the A1555G mutation were identified in any of the patients. Nucleotide variations in the variable D-loop region did not correlate with cisplatin-induced hearing loss. However, these patients clustered more frequently (5 out of 20) in the rare European haplogroup J, than those with normal hearing after therapy (1 out of 19). CONCLUSION: The linkage of cisplatin-induced hearing impairment to the mitochondrial haplogroup J, which is also associated with the mitochondrially-mediated Leber's Hereditary Optic Neuropathy, might act as a predisponsing genetic background for biochemical differences in mitochondria.

Multiple fibroadenomas harbouring carcinoma in situ in a woman with a family history of breast/ovarian cancer.

A 46 year old woman with a family history of breast and ovarian cancer presented with multiple fibroadenomas in both breasts. From three fibroadenomas removed from the left breast carcinoma in situ (CIS) had developed. One fibroadenoma gave rise to ductal CIS, whereas the other two harboured lobular CIS. This is the first report of three fibroadenomas simultaneously giving rise to CIS. In addition, synchronous fibroadenomas harbouring different types of CIS from one fibroadenoma to the other have never been described. Direct sequencing revealed a mutation (5075G-->A) in the BRCA1 gene, but retention of BRCA1 immunohistochemical staining and no loss of heterozygosity at the BRCA1 locus by polymerase chain reaction made a pathogenic mutation in BRCA1 unlikely. Furthermore, in this family no cosegregation of breast cancer with this BRCA1 mutation was seen. Indeed, this mutation is now regarded as a polymorphism. This case stresses the need for histological evaluation of all breast masses in women with a strong positive family history for breast and/or ovarian cancer.

Glutathione S-transferase genetic polymorphisms and individual sensitivity to the ototoxic effect of cisplatin.

One of the side effects of cisplatin therapy in malignant neoplasms is ototoxicity. This effect shows a wide inter-individual range which is more variable than the pharmacokinetic parameters. Oxidative stress has been implicated in cisplatin ototoxicity. The glutathione S-transferase (GST) supergene family encodes isoenzymes that appear to be critical in protection against oxidative stress. Certain GST loci are polymorphic, demonstrating alleles that are null (GSTM1 and GSTT1), encode low-activity variants (GSTP1) or are associated with variable inducibility (GSTM3). The aim of our study was to investigate genetic risk factors involved in the ototoxicity of cisplatin and to determine whether the polymorphisms in five GST genes affect the individual risk of ototoxicity by cisplatin. Two groups of patients were analyzed in this study: group H, 20 patients early and highly sensitive to the ototoxicity of cisplatin; and group N, 19 patients with no hearing impairment under comparable doses of the drug. We found a protective effect for the GSTM3*B allele with a frequency of 0.18 in the group with normal hearing after therapy versus 0.025 in the group with hearing impairment. (chi2=5.37; p=0.02).

Comparison of conformation-sensitive gel electrophoresis and single-strand conformation polymorphism analysis for detection of mutations in the BRCA1 gene using optimized conformation analysis protocols.

In order to develop a selective mutation screening strategy for BRCA1, one of the gene responsible for hereditary predisposition to breast cancer, we analysed by single-strand conformation polymorphism (SSCP) and conformation-sensitive gel electrophoresis (CSGE) a cohort of 20 Bulgarian breast cancer patients, prescreened for nonsense mutations by the protein truncation test. By assaying the complete coding sequence of the gene applying both methods, we were able to detect 12 sequence alterations: 11 nucleotide substitutions and one deletion. Two of the alterations are intronic polymorphisms, the rest are exon sequence variants. Of the 12 polymorphisms identified, 11 are described and one is new. All sequence changes were detected by CSGE and eight of them were also shown by SSCP analysis. There was no sequence alterations which could be detected by SSCP analysis only. We propose that because of the specificity of most sequence variants detected (nucleotide substitutions) and the comparatively high percentage of AT content of the BRCA1 gene (58.4%), CSGE turned out to be the more sensitive technique in our assay. This observation is in agreement with other accepted analysis strategies for BRCA1 and it may prove useful for mutation screening of AT-rich, multi-exon genes.

[Molecular analysis of the heterogeneity of hereditary monosymptomatic sensorineural hearing loss]. / Molekulare Analysen der Heterogenität hereditärer monosymptomatischer Schallempfindungsschwerhörigkeiten.

BACKGROUND: Genetic characterization of hereditary hearing impairment has progressed considerably with the mapping of nine chromosomal loci for monosymptomatic autosomal-inherited hearing loss over the last three years. METHODS: Following thorough clinical evaluation, linkage analysis using microsatellite markers was performed in two large families from Westphalia/West Germany. RESULTS: For all the dominant (DFNA1--4) and three autosomal-recessive loci (DFNB1--3) described to date, linkage was finally excluded. CONCLUSIONS: A high degree of genetic heterogeneity must be assumed. Identification of individual genes for monosymptomatic sensorineural hearing loss by linkage analysis in large pedigrees may help in molecular differentiation of hearing.

Hepatitis B virus infection without immunological markers after open-heart surgery.

Post-transfusion hepatitis is still an important problem, despite the screening of blood donors for hepatitis B (HBV) and C virus infections. We assessed whether HBV DNA might be detected by PCR in prospectively collected serum samples of patients with unexplained post-transfusion hepatitis but no immunological HBV markers. We found HBV DNA in 4 (20%) of 20 patients with unexplained post-transfusion hepatitis and in 5 patients with mildly increased aminotransferases. The clinical course of these HBV infections was usually mild and self-limiting. Thus we found that low-titre, immunologically negative HBV infections do exist and might represent a significant cause of post-transfusion hepatitis.

Sequence analysis of hepatitis B virus DNA in immunologically negative infection.

It was previously demonstrated that the serum of some patients without immunological evidence of HBV infection contains the virus. Here we demonstrated by sequence analysis that the serum of such a patient contained a mixed HBV population. In comparison with HBV genomes of different genotypes twenty-two nucleotide variations were found in all clones sequenced in parallel. One nucleotide variation was identified within the enhancer I. Twelve of the twenty-two nucleotide variations caused altogether fifteen changes of amino acid sequence in known or predicted viral proteins. The proteins of the P open reading frame, which are most important for viral replication, were affected by nine amino acid substitutions. Three amino acid substitutions concerned the product of the X gene, a transcriptional transactivator of various viral and cellular promoters. Three mutations were only observed in some of the clones. One point mutation affected the direct repeats of the enhancer II. It occurred together with an 8 bp-deletion involving the C promoter region and the X gene. The third mutation was a single insertion, causing a fusion of the X and C gene. One or several of the identified mutations could be responsible for the diminished rate of replication and consequently for the low-titred, immunologically negative HBV infection.