These include BRCA1, BRCA2 and TP 53 . Because of the great effect these genes EX 527 nmr have on cancer risk, one hallmark of these genes is the creation of a Mendelian autosomal dominant pattern of cancer. These genes also tend

to predispose to earlier onset, multifocal breast tumors. Second: Variant genotypes at other loci (polygene) may confer a relatively smaller degree of cancer risk, but they carried by a larger proportion of the general population. In the general population, breast cancer usually occurs in the absence of a strong family history, appears unilaterally, and has a relatively late (often postmenopausal) age at diagnosis [5]. The discovery of breast cancer genes, BRCAl and BRCA2, has led to an explosive growth in cancer screening for population at risk. Every one carries these genes as part of the normal genetic makeup. Patients who are at risk for breast cancer NVP-BGJ398 order carry mutations of these genes. Early in the last decades, in 1990, genetic studies provided initial evidence that the risk of breast cancer in some families is Ricolinostat molecular weight linked to position q2i of chromosome 17 which was characterized by autosomal dominant inheritance. In fact, loss of heterozygosity at 17q was found in most familial breast and ovarian tumors, suggesting the involvement of tumor suppressor gene(s) [6, 7]. In 1994, the breast cancer susceptibility gene BRCAl, the most important tumor suppressor gene, was identified by positional cloning.

This gene is expressed in numerous tissues, including breast and ovary. BRCAl gene is a large gene spread over approximately 100 kb of genomic DNA. It is composed of 24 exons, 1

and 4 are non-coding and are not analyzed, and code for a protein of 1863 amino acids producing a nuclear protein of about 220 kd. It contains a protein motif, a Ring Finger domain near the amino acid terminus and a conserved acidic carboxyl terminus that functions in transcriptional co-activation [6, 8]. There is evidence that BRCA1 protein being directly involved in the DNA repair process. The BRCA1 gene product interacts with the RAD51 protein, a key component in homologous recombination and double all strand break repair [9]. In 1995, the BRCA2 gene was identified at chromosome 13qi2-i3. BRCA2 gene is even larger than BRCA1, consists of 27 exons, 1 is non-coding and is not analyzed, and codes for a protein of 3418 amino acids, making a 380 kd nuclear protein. BRCA2 gene has no obvious homology to any known gene and the protein contains no well-defined functional domain [10]. The BRCA2 protein also interacts with RAD51. Perhaps through this mutual association with RAD51, BRCA1 and BRCA2 associate with each other at sites of DNA synthesis after the induction of DNA damage. Nonetheless, BRCA1 and BRCA2 proteins appear to share a number of functional similarities that may suggest why mutations in these genes lead to specific hereditary predisposition to breast and ovarian cancer [11].