Cytogenetic finding of breast cancer cases and in their first-degree relatives

Micronucleus, nucleoplasmic bridge and nuclear bud frequencies in patients with laryngeal carcinoma

The aim of the study is to determine and compare micronucleus (MN), nucleoplasmic bridge (NPB) and nuclear bud (NBUD) frequencies in patients with laryngeal carcinoma and healthy controls. The study was conducted in the School of Medicine of Onsekiz Mart University. A total of 102 volunteers, 51 of whom had laryngeal carcinoma and 51 of whom were healthy control subjects, participated in this study. The Cytokinesis-Block Micronucleus Assay (CBMN) was applied to peripheral blood lymphocytes taken from patients and controls. We evaluated MN, NPBs and NBUDs frequencies in patients with laryngeal carcinoma and compared the results with those in the control group. The frequencies of MN, NPBs and NBUDs of patients with laryngeal carcinoma were found significantly higher than those in the control group (P = 0.01, P = 0.004, P = 0.01, respectively). MN, NPB and NBUD frequencies were also compared in the patients with and without pesticide exposure, and the means of all frequencies was higher in patients with pesticide exposure (P = 0.001, P = 0.02 respectively). The MN, NPBs and NBUDs frequencies of the patients with laryngeal cancer were significantly higher than those of the control group, and pesticide exposure might be a risk factor that increases genomic instability and risk of laryngeal cancer.

Micronuclei and upper body cancers (head, neck, breast cancers) a systematic review and meta-analysis

A systematic review and a meta-analysis were performed on 19 studies on head and neck cancer (HNC) and 21 studies on breast cancer (BC) to evaluate the application of micronucleus (MN) assay as a predictive and prognostic test for cancer risk. In these studies the MN test was applied in peripheral lymphocytes and buccal cells of patients and healthy subjects with family history of cancer. The meta-analysis on MN applied in buccal cells of HNC patients was performed on two subgroups of studies. A significant increase of MN frequency in patients compared to healthy controls was observed for the subgroup on oral cancer (243 cases/370 controls, meta-MR = 4.71 95 %CI:2.75-8.06) and HNC (204 patients/163 controls metaMR=2.28 95 %CI:2.02-2.58). A metaMR = 3.27 (95 %CI:1.41-7.59) was obtained for MN applied in peripheral lymphocytes on HNC (160 cases/160 controls). For BC, the analysis of MN in peripheral lymphocytes showed significantly higher values in patients (n = 761) than in controls (n = 788) (meta-MR1.90 95 % CI:1.44-2.49). No statistically significant increase of baseline MN was detected in studies on groups of healthy subjects with BC family history (n = 224) or with BRCA1/2 mutations (n = 101) with respect to the controls. After ex-vivo challenge with ionizing radiation, the meta-analysis revealed a slightly statistically significant increase in MN only in BC patients (n = 614) compared to controls (n = 622)(meta-MR = 1.11 95 %CI:1.02-1.21); no increase was observed in healthy subjects with BC family history carrying or not BRCA1/2 mutations. Significant difference between BC patients (n = 183) and controls (n = 165) was observed by the meta-analysis of data on MN in buccal cells (MR = 3.89 95 %CI:1.54-9.78). The MN assay in buccal cells has some perspective of clinical application in HNC.

Penalized negative binomial models for modeling an overdispersed count outcome with a high-dimensional predictor space: Application predicting micronuclei frequency

Chromosomal aberrations, such as micronuclei (MN), have served as biomarkers of genotoxic exposure and cancer risk. Guidelines for the process of scoring MN have been presented by the HUman MicroNucleus (HUMN) project. However, these guidelines were developed for assay performance but do not address how to statistically analyze the data generated by the assay. This has led to the application of various statistical methods that may render different interpretations and conclusions. By combining MN with data from other high-throughput genomic technologies such as gene expression microarray data, we may elucidate molecular features involved in micronucleation. Traditional methods that can model discrete (synonymously, count) data, such as MN frequency, require that the number of explanatory variables (P) is less than the number of samples (N). Due to this limitation, penalized models have been developed to enable model fitting for such over-parameterized datasets. Because penalized models in the discrete response setting are lacking, particularly when the count outcome is over-dispersed, herein we present our penalized negative binomial regression model that can be fit when P > N. Using simulation studies we demonstrate the performance of our method in comparison to commonly used penalized Poisson models when the outcome is over-dispersed and applied it to MN frequency and gene expression data collected as part of the Norwegian Mother and Child Cohort Study. Our countgmifs R package is available for download from the Comprehensive R Archive Network and can be applied to datasets having a discrete outcome that is either Poisson or negative binomial distributed and a high-dimensional covariate space.

Aurora B-mediated localized delays in nuclear envelope formation facilitate inclusion of late-segregating chromosome fragments

Acentric chromosomes exhibit delayed segregation during mitosis. How these delays affect nuclear envelope reassembly is not fully understood. Lagging acentrics coated with Aurora B induce a highly localized gap in the nuclear envelope to allow acentric entry into daughter nuclei. Gap formation is decreased upon reduction of Aurora B.

To determine how chromosome segregation is coordinated with nuclear envelope formation (NEF), we examined the dynamics of NEF in the presence of lagging acentric chromosomes in Drosophila neuroblasts. Acentric chromosomes often exhibit delayed but ultimately successful segregation and incorporation into daughter nuclei. However, it is unknown whether these late-segregating acentric fragments influence NEF to ensure their inclusion in daughter nuclei. Through live analysis, we show that acentric chromosomes induce highly localized delays in the reassembly of the nuclear envelope. These delays result in a gap in the nuclear envelope that facilitates the inclusion of lagging acentrics into telophase daughter nuclei. Localized delays of nuclear envelope reassembly require Aurora B kinase activity. In cells with reduced Aurora B activity, there is a decrease in the frequency of local nuclear envelope reassembly delays, resulting in an increase in the frequency of acentric-bearing, lamin-coated micronuclei. These studies reveal a novel role of Aurora B in maintaining genomic integrity by promoting the formation of a passageway in the nuclear envelope through which late-segregating acentric chromosomes enter the telophase daughter nucleus.

Sister chromatid exchange: A possible approach to characterize familial breast cancer patients

Sister chromatid exchange (SCE) frequency is widely used as an indicator of spontaneous chromosome instability. We investigated SCE frequency in the peripheral blood lymphocytes of familial and sporadic breast cancer (BC) patients from the Apulian Caucasian Population. Eighty-one patients were enrolled: 22 with familial history and 59 sporadic patients. Eleven familial patients had an 'increased risk' of BRCA gene mutation (BRCAPro ≥ 10%) and were candidates for BRCA1 and BRCA2 mutation analysis. For these reasons, we stratified the 22 familial BC patients in two group: 'low-risk' (n=11) and 'high-risk' (n=11) patients for BRCA gene mutations. Two of these 11 'high-risk' patients (18%) had pathogenic mutations in the BRCA2 gene. The subjects were not cigarette smokers or alcohol or drug users, and had no genetic disorders or chronic diseases affecting the family. Our results showed a significant increase in SCE frequency in the familial (5.305 ± 1.088/metaphase) (P<0.0001) and the sporadic patients (3.943 ± 0.552) (P<0.0001) compared to the controls (3.197 ± 0.649). We found that the SCE frequency was always significantly higher in familial than in sporadic patients, regardless of their clinicopathological characteristics. Moreover, we observed that the frequency of SCE in BRCA2 mutation carrier patients was higher compared to patients without mutations in BRCA1/2 genes. These findings highlight an intrinsic genomic instability in familial patients, and we suggest that SCE frequency may be used as a biomarker to better characterize familial BC.