Generation and maintenance of acentric stable double minutes from chromosome arms in inter-species hybrid cells.

BACKGROUND: Extrachromosomal acentric double minutes (DMs) contribute to human malignancy by carrying amplified oncogenes. Recent cancer genomics revealed that the pulverization of defined chromosome arms (chromothripsis) may generate DMs, however, nobody had actually generated DMs from chromosome arm in culture. Human chromosomes are lost in human-rodent hybrid cells. RESULTS: We found that human acentric DMs with amplified c-myc were stable in human-rodent hybrid cells, although the degree of stability depended on the specific rodent cell type. Based on this finding, stable human-rodent hybrids were efficiently generated by tagging human DMs with a plasmid with drug-resistance gene. After cell fusion, human chromosomes were specifically pulverised and lost. Consistent with chromothripsis, pulverization of human chromosome arms was accompanied by the incorporation into micronuclei. Such micronucleus showed different replication timing from the main nucleus. Surprisingly, we found that the hybrid cells retained not only the original DMs, but also new DMs without plasmid-tag and c-myc, but with human Alu. These DMs were devoid of telomeres and centromeres, and were stable in culture for more than 3 months. Microarray analysis showed that the new DMs were generated from several human chromosomal regions containing genes advantageous for cellular growth. Such regions were completely different from the original DMs. CONCLUSIONS: The inter-species hybrid mimics the chromothripsis in culture. This is the first report that experimentally demonstrates the generation of multiple stable acentric DMs from the chromosome arm.

Evaluation of BRCA1/2 mutational status among German and Austrian women with triple-negative breast cancer.

PURPOSE: Testing for BRCA1 and BRCA2 mutations in breast cancer patients is used to identify the risk of second primary cancers and the risk of cancer in the patients' family. Women with triple-negative breast cancer (TNBC) are thought to be more likely to be BRCA1/2 mutation carriers, but most national guidelines for genetic testing, including those used in Germany and Austria, do not consider receptor triple negativity. METHODS: We determined the prevalence of BRCA1 and BRCA2 mutations within a cohort of 100 unselected TNBC cases, including patients from Germany and Austria to identify those BRCA-positive patients with a masked family history and who would have been missed due to respective current national guidelines. Double-stranded Sanger sequencing of all exons of BRCA1 and BRCA2, respectively, was performed. RESULTS: We identified a total of 13 deleterious mutations in BRCA1 and a total of four deleterious mutations in BRCA2. The total rate of deleterious BRCA1/2 mutation carriers was 21 % in our cohort. Six novel mutations, including two deleterious mutations, have been identified, which have not been described in public mutation databases so far. According to current German and Austrian national guidelines for genetic testing, 38.1 and 52.4 %, respectively, of BRCA1/2 mutation carriers would have been overlooked. CONCLUSIONS: We conclude that the prevalence of BRCA1 and BRCA2 mutations is high in TNBC patients and that BRCA1/2 mutations are not restricted to young women or patients with a positive family history. Receptor triple negativity should therefore be considered in BRCA1/2 genetic testing guidelines.

Radiology-pathology conference: primary peritoneal mesothelioma.

Primary peritoneal mesothelioma is a rare neoplasm which carries a dismal prognosis. These highly aggressive tumors arise from mesothelial cells lining the peritoneum and are rapidly fatal. The neoplasm is typically associated with crocidolite asbestos exposure. We present the case of a 75-year-old man with primary peritoneal mesothelioma, with invasion into the right hepatic lobe.