Genotype-phenotype correlations among BRCA1 4153delA and 5382insC mutation carriers from Latvia.

BACKGROUND: Mutations in the high penetrance breast and ovarian cancer susceptibility gene BRCA1 account for a significant percentage of hereditary breast and ovarian cancer cases. Genotype-phenotype correlations of BRCA1 mutations located in different parts of the BRCA1 gene have been described previously; however, phenotypic differences of specific BRCA1 mutations have not yet been fully investigated. In our study, based on the analysis of a population-based series of unselected breast and ovarian cancer cases in Latvia, we show some aspects of the genotype-phenotype correlation among the BRCA1 c.4034delA (4153delA) and c.5266dupC (5382insC) founder mutation carriers. METHODS: We investigated the prevalence of the BRCA1 founder mutations c.4034delA and c.5266dupC in a population-based series of unselected breast (n = 2546) and ovarian (n = 795) cancer cases. Among the BRCA1 mutation carriers identified in this analysis we compared the overall survival, age at diagnosis and family histories of breast and ovarian cancers. RESULTS: We have found that the prevalence of breast and ovarian cancer cases (breast: ovarian cancer ratio) differs significantly among the carriers of the c.5266dupC and c.4034delA founder mutations (OR = 2.98, 95%CI = 1.58 to 5.62, P < 0.001). We have also found a difference in the prevalence of breast and ovarian cancer cases among the 1st and 2nd degree relatives of the c.4034delA and c.5266dupC mutation carriers. In addition, among the breast cancer cases the c.4034delA mutation has been associated with a later age of onset and worse clinical outcomes in comparison with the c.5266dupC mutation. CONCLUSIONS: Our data suggest that the carriers of the c.4034delA and c.5266dupC founder mutations have different risks of breast and ovarian cancer development, different age of onset and prognosis of breast cancer.

Underestimated survival predictions of the prognostic tools Adjuvant! Online and PREDICT in BRCA1-associated breast cancer patients.

BRCA1-associated breast cancer is considered an unique clinical entity with its own specific histopathological characteristics. Several recently published large studies have shown that overall survival of BRCA1 mutation carriers having breast cancer is similar to sporadic breast cancer patients. It was also suggested that better response to chemotherapy is one of the most important factors that improves the clinical outcome of breast cancers with unfavorable histopathological subtypes in BRCA1 mutation carriers. Adjuvant! Online and PREDICT are web-based prognostic tools that estimate the survival benefit of adjuvant chemotherapy in primary breast cancer patients. These tools have been extensively validated in different populations; however, the accuracy of the predictions made by Adjuvant! Online and PREDICT among BRCA1 mutation carriers has not yet been investigated. In this study we have found, that predictions of overall and breast cancer-specific survival obtained from Adjuvant! Online and PREDICT were significantly lower than the observed survival percentages in the study population [predicted--observed difference for 10-year overall survival: -9.75%, P < 0.0001 (Adjuvant! Online); -10.21%, P < 0.0001 (PREDICT)]. Thus this study suggests that Adjuvant! Online and PREDICT should be used with caution in this group of patients. Further updating of adjuvant therapy benefit calculation tools by inclusion of the information about inherited genetic alterations should be considered to improve the performance of the prognostic programs among hereditary breast cancer patients.

Endopolyploidy in irradiated p53-deficient tumour cell lines: persistence of cell division activity in giant cells expressing Aurora-B kinase.

Recent findings including computerised live imaging suggest that polyploidy cells transiently emerging after severe genotoxic stress (and named 'endopolyploid cells') may have a role in tumour regrowth after anti-cancer treatment. Until now, mostly the factors enabling metaphase were studied in them. Here we investigate the mitotic activities and the role of Aurora-B, in view of potential depolyploidisation of these cells, because Aurora-B kinase is responsible for coordination and completion of mitosis. We observed that endopolyploid giant cells are formed via different means in irradiated p53 tumours, by: (1) division/fusion of daughter cells creating early multi-nucleated cells; (2) asynchronous division/fusion of sub-nuclei of these multi-nucleated cells; (3) a series of polyploidising mitoses reverting replicative interphase from aborted metaphase and forming giant cells with a single nucleus; (4) micronucleation of arrested metaphases enclosing genome fragments; or (5) incomplete division in the multi-polar mitoses forming late multi-nucleated giant cells. We also observed that these activities can release para-diploid cells, although infrequently. While apoptosis typically occurs after a substantial delay in these cells, we also found that approximately 2% of the endopolyploid cells evade apoptosis and senescence arrest and continue some form of mitotic activity. We describe here that catalytically active Aurora-B kinase is expressed in the nuclei of many endopolyploid cells in interphase, as well as being present at the centromeres, mitotic spindle and cleavage furrow during their attempted mitotes. The totally micronucleated giant cells (containing sub-genomic fragments in multiple micronuclei) represented only the minor fraction which failed to undergo mitosis, and Aurora-B was absent from it. These observations suggest that most endopolyploid tumour cells are not reproductively inert and that Aurora-B may contribute to the establishment of resistant tumours post-irradiation.