Molecular and pathological characterization of inherited breast cancer

Breast cancer-associated Abraxas mutation disrupts nuclear localization and DNA damage response functions

Breast cancer is the most common cancer in women in developed countries and has a well-established genetic component. Germline mutations in a network of genes encoding BRCA1, BRCA2, and their interacting partners confer hereditary susceptibility to breast cancer. Abraxas directly interacts with the BRCA1 BRCT (BRCA1 carboxyl-terminal) repeats and contributes to BRCA1-dependent DNA damage responses, making Abraxas a candidate for yet unexplained disease susceptibility. Here, we have screened 125 Northern Finnish breast cancer families for coding region and splice-site Abraxas mutations and genotyped three tagging single-nucleotide polymorphisms within the gene from 991 unselected breast cancer cases and 868 female controls for common cancer-associated variants. A novel heterozygous alteration, c.1082G>A (Arg361Gln), that results in abrogated nuclear localization and DNA response activities was identified in three breast cancer families and in one additional familial case from an unselected breast cancer cohort, but not in healthy controls (P = 0.002). On the basis of its exclusive occurrence in familial cancers, disease cosegregation, evolutionary conservation, and disruption of critical BRCA1 functions, the recurrent Abraxas c.1082G>A mutation connects to cancer predisposition. These findings contribute to the concept of a BRCA-centered tumor suppressor network and provide the identity of Abraxas as a new breast cancer susceptibility gene.

A recurrent mutation in PALB2 in Finnish cancer families

BRCA1, BRCA2 and other known susceptibility genes account for less than half of the detectable hereditary predisposition to breast cancer. Other relevant genes therefore remain to be discovered. Recently a new BRCA2-binding protein, PALB2, was identified. The BRCA2-PALB2 interaction is crucial for certain key BRCA2 DNA damage response functions as well as its tumour suppression activity. Here we show, by screening for PALB2 mutations in Finland that a frameshift mutation, c.1592delT, is present at significantly elevated frequency in familial breast cancer cases compared with ancestry-matched population controls. The truncated PALB2 protein caused by this mutation retained little BRCA2-binding capacity and was deficient in homologous recombination and crosslink repair. Further screening of c.1592delT in unselected breast cancer individuals revealed a roughly fourfold enrichment of this mutation in patients compared with controls. Most of the mutation-positive unselected cases had a familial pattern of disease development. In addition, one multigenerational prostate cancer family that segregated the c.1592delT truncation allele was observed. These results indicate that PALB2 is a breast cancer susceptibility gene that, in a suitably mutant form, may also contribute to familial prostate cancer development.

The ?portrait? of hereditary breast cancer

Five to ten per cent of all breast carcinomas are of hereditary origin. Many of them have been associated to mutations in the BRCA1 and BRCA2 susceptibility genes. No "BRCA3" gene has been found to account for the non-BRCA1/BRCA2 breast cancer (BRCAx) families, and BRCAx tumors are increasingly believed to originate from multiple distinct genetic events. Phenotype studies have questioned the existence of specific "portraits" among hereditary breast carcinomas (HBC). They have shown that most BRCA1 tumors have a "basal (epithelial)-like" aspect, while BRCA2 and BRCAx HBC are more heterogeneous. HBC have also been submitted to genetic analyses, notably with the objective of resolving the heterogeneity of BRCAx lesions. The present review aims to summarize recent data on BRCA1, BRCA2, and BRCAx HBC, including hypotheses on the origin of BRCA1 tumors and their paradoxical relations to estrogen-sensitivity.

Pharmacogenomics

The discovery of the human genome and subsequent expansion of proteomics research combined with emerging technologies such as functional imaging, biosensors and sophisticated computational biology are producing unprecedented changes in today's healthcare. The expanding knowledge of the molecular basis of cancer has shown that significant differences in gene expression patterns can guide therapy not only for neoplastic conditions, but also for a variety of diseases including inflammatory disorders, cardiovascular disease and neurodegenerative processes. As a result, the fields of pharmacogenetics and pharmacogenomics have emerged as potential new testing platforms for the individualized management of patients. An individual's response to a drug is the complex interaction of both genetic and non-genetic factors. Genetic variants in the drug target itself, disease pathway genes, or drug metabolizing enzymes may all be used as predictors of drug efficacy or toxicity. In oncology, the SNP technology has focused on detecting the predisposition for cancer, predicting of toxic responses to drugs and selecting the best individual and combinations of anti-cancer drugs. Pharmacogenomics involves the application of whole genome technologies (e.g., gene and protein expression data) for the prediction of the sensitivity or resistance of an individual's disease to a single or group of drugs. Genomic microarrays and transcriptional profiling have the ability to generate hundreds of thousands of data points requiring sophisticated and complex information systems necessary for accurate and useful data analysis. This technique has generated a wealth of new information in the fields of leukemia/lymphoma, and solid tumor classification and prediction of metastasis, drug and biomarker target discovery and pharmacogenomic drug efficacy testing.

Integration of molecular diagnostics with therapeutics: implications for drug discovery and patient care

The Introduction of targeted therapeutics into clinical practice has created major opportunities for further development of the molecular diagnostics industry. Emerging genomic and proteomic technologies and information are now resulting in the molecular subclassification of disease as the basis for diagnosis, prognosis and therapeutic selection. The ultimate goals of personalized medicine are to take advantage of a molecular understanding of disease, both to optimize drug development and direct preventive resources and therapeutic agents at the right population of people while they are still well. Single nucleotide polymorphisms identification and genotyping have uncovered predisposition markers from cancer and heart disease as well in the prediction of both drug efficacy and toxicity. Pharmacogenomic and pharmacodynamic assays are being developed to enhance the speed and decrease the cost of drug development, as well as reduce side effects and increase response rates in a variety of diseases. The traditional trial and error practice of medicine is progressively eroding in favor of more precise marker-assisted diagnosis and safer and more effective molecularly guided treatment of disease. For the diagnostics industry this represents an unprecedented opportunity for integration, increased value and commercial opportunities for molecularly-derived tests.