Project description:Despite relevant clinical and/or familial presentations suggesting a hereditary predisposition (early-onset, multiple primary tumors, familial aggregation), targeted genomic analysis based on the phenotype are often non contributive. As somatic cancer genes are limited, the hypothesis is that the targeted next-generation sequencing of 200 genes, selected for their implications in cancers may contribute to the understanding of many selected patients’ presentation by the identification of germline deleterious mutations, and may identified phenotype overlapping and/or mosaicisms. The focus will be put on early-onset breast, ovarian, colorectal cancer or pediatric cancers and multiple primary tumors.
Project description:Amplification of chromosomal region 11q13, containing the cell cycle regulatory gene CCND1, is frequently found in breast cancer and other malignancies. It is associated with the favourable oestrogen receptor (ER) positive breast tumour phenotype, but also with poor prognosis and treatment failure. 11q13 spans almost 14 Mb and contains more than 200 genes and is affected by various patterns of copy number gains, suggesting complex mechanisms and selective pressure during tumour progression. In the present study we used 32k tiling BAC array CGH to analyse 94 CCND1-amplified breast tumours from sporadic, hereditary and familial breast cancers to fine map chromosome 11q13. A set containing 281 CCND1-non-amplified breast tumours was used for comparisons. We used gene expression data to further validate the functional effect of gene amplification. We identified six core regions covering 11q13.1-q14.1 that were amplified in different combinations. The major core contained CCND1, whereas two cores were found proximal of CCND1 and three distal. The majority of the CCND1-amplified tumours were ER-positive and classified as luminal B. Furthermore, we found that CCND1 amplification is associated with a more aggressive phenotype within histological grade 2 tumours and luminal A subtype tumours. Amplification was equally prevalent in familial and sporadic tumours, but strikingly rare in BRCA1- and BRCA2- mutated tumours. We conclude that 11q13 includes many potential target genes in addition to CCND1. Genomic profiling of 94 CCND1-amplified breast tumors using tiling BAC aCGH. A number of cases were hybridized as replicates or replicate as dye-swaps.
Project description:Summary: Considerable heterogeneity of morphology and disease outcome exists within breast cancers (BC), which likely reflects variable molecular pathogeneses within this broad clinical group. Aim: To evaluate the underlying genomic alterations associated with familial, early-onset BC (EOBC) phenotypes, in order to improve the management of this disease. Methods: Using hierarchical clustering of morphological and immunophenotypical parameters, 116 EOBC were stratified into six groups. Conventional and array-based comparative genomic hybridisation was used to analyse the genomic alterations. Results: Specific areas of genomic imbalance were associated with individual phenotypes. The largest phenotypical group was high grade, oestrogen receptor and HER-2 negative. This group contained the majority of BRCA1 germline mutation-associated tumours and commonly showed loss of chromosomal regions 5cent-5q13, 5q14–22 and 4q28–32. High mitotic rate, an important indicator of tumour cell proliferation and poor prognosis, was associated with gain of 19p, mapped within 7 Mb of the telomere. This region contains the candidate oncogene CDC34, the protein product of which is involved in ubiquitin-mediated degradation of the cyclin-dependent kinase inhibitor, p27Kip1. Conclusion: Phenotype-based analysis can be used to determine the genetic changes important in subtypes of BC. Further, the different morphological phenotypes could act as a cost-effective surrogate for genotypical stratification to facilitate optimal management of this disease. Keywords: comparative genomic hybridisation, breast cancer, aCGH
Project description:Loss of function of the tumor suppressor BRCA1 (Breast Cancer 1) protein is responsible for numerous familial and sporadic breast cancers. We previously identified PABP1 as a novel BRCA1 partner and showed that BRCA1 modulates translation through its interaction with PABP1. We showed that the global translation was diminished in BRCA1-depleted cells and increased in BRCA1-overexpressing cells. Our findings raised the question whether BRCA1 affects translation of all cytoplasmic cellular mRNAs or whether it specifically targets a subset of mRNAs. In the present study, we investigated which mRNAs are regulated by BRCA1 using a microarray analysis of polysome-associated RNAs from BRCA1-depleted MCF7 cells, a human breast cancer cell line. We isolated mRNAs from the high-molecular-weight polysomes (fractions 12 to 18) and total cellular cytoplasmic mRNAs from the cytoplasmic fraction of MCF7 cells transiently expressing either siRNA directed against BRCA1 or control siRNA. Since we were interested in identifying the mRNAs that were translationally regulated by BRCA1, we determined the relative translatability of each mRNA. The relative translatability of an mRNA was determined by normalizing the change in abundance in polysomal mRNA to the change in abundance in total cytoplasmic mRNA for each mRNA.
Project description:It is now well understood that epigenetic alterations occur frequently in sporadic breast carcinogenesis, but little is known about the epigenetic alterations associated with familial breast tumors. We performed genome-wide DNA methylation profiling on familial breast cancers (n=33) to identify patterns of methylation specific to the different mutation groups (BRCA1, BRCA2 and BRCAx) or intrinsic subtypes of breast cancer (basal, luminal A, luminal B, HER2 and normal-like). We used methylated DNA immunoprecipitation (meDIP) on Affymetrix human promoter chips to interrogate methylation profiles across 25,500 distinct transcripts.