RESUMO
ERBB2 is one of the most important oncogenes in breast cancer, and its disordered expression is commonly associated with gene amplification. Amplification of at least one gene near ERBB2, topoisomerase IIalpha (TOP2A), has been shown to be clinically significant, but the prevailing patterns of gene amplification in this region of chromosome arm 17q have not been studied systematically in clinical cases of breast cancer. For characterizing this region, a commercial ERBB2-containing contig probe and 7 probes prepared from single overlapping BAC and P1 clones lying telomeric to ERBB2 and including TOP2A were hybridized to 77 ERBB2-amplified archival breast tumor specimens from 75 patients. The 7 single-clone probes covered a region of approximately 650 kb starting 114 kb telomeric to ERBB2. Amplification of the ERBB2 contig target alone was found in 32% of the tumors, whereas all 8 probe targets were amplified in 12% of the tumors, based on an amplification criterion of there being more than or equal to 2 targets per chromosome 17 centromere. When one of the 7 overlapping probes encompassing TOP2A indicated amplification within a specimen, all probes telomeric to that probe usually showed amplification. Only 5 specimens had regions of normal or deleted targets separating 2 amplified targets. Also, tumors that showed deletion of TOP2A usually showed deletion of one or more contiguous targets. The observed patterns of amplification and deletion are consistent with the break-fusion-bridge model for gene amplification. TOP2A was amplified in 25% of all tumor specimens and was deleted in 24%, based on a deletion criterion of there being fewer than or equal to 0.75 targets per chromosome 17 centromere. Considering the relevance of the TOP2A gene product to anthracycline therapy and the wealth of other cancer-associated genes within the ERBB2/TOP2A region, the pattern of amplification and deletion near ERBB2 and TOP2A may have a dramatic effect on the malignant potential of breast carcinomas and their response to therapy.
Assuntos
Neoplasias da Mama/genética , Mapeamento Cromossômico/métodos , DNA Topoisomerases Tipo II/genética , Dosagem de Genes , Genes erbB-2 , Anáfase/genética , Antígenos de Neoplasias , Neoplasias da Mama/patologia , Centrômero/genética , Deleção Cromossômica , Cromossomos Humanos Par 17/genética , Sondas de DNA/genética , DNA de Neoplasias/genética , Proteínas de Ligação a DNA , Amplificação de Genes/genética , Humanos , Modelos Genéticos , Proteínas de Fusão Oncogênica/genética , Inclusão em Parafina , Proteínas de Ligação a Poli-ADP-Ribose , Receptor ErbB-2/genética , Recombinação Genética/genéticaRESUMO
Cyclin E is a key regulator of the G(1)-S transition. Abnormalities in cyclin E expression have been related to survival in a variety of cancers. This study evaluated the prognostic relevance of cyclin E in human ovarian cancer. Immunohistochemical expression of cyclin E was evaluated in 139 advanced, suboptimally debulked epithelial ovarian cancer specimens from patients treated on Gynecologic Oncology Group protocol 111. High cyclin E protein expression (> or =40% cyclin E positive tumor cells) was seen in 62 (45%) of the advanced, suboptimally debulked ovarian cancer patients. Expression of cyclin E was not associated with age, race, stage, grade, cell type, or amount of residual disease. High verses low cyclin E expression was associated with a shorter median survival (29 +/- 2 versus 35 +/- 3 months) and worse overall survival (P < 0.05). Univariate and multivariate regression analyses revealed that high relative to low cyclin E was associated with a 40-50% increase in the risk of death (hazard rate, P < or = 0.05). Fluorescence in situ hybridization was used in a subset of 20 cases to examine cyclin E gene amplification. Eight of 10 cases with high cyclin E expression exhibited amplification of the cyclin E gene, whereas only 1 of 10 cases with low expression displayed gene amplification (P < 0.006). High cyclin E expression was an independent poor prognostic factor for patients with advanced ovarian cancer, and it was associated with amplification of the cyclin E gene.
