BRCA1 and BRCA2 germline mutations in Sardinian breast cancer families and their implications for genetic counseling.

BACKGROUND: The Sardinian population is genetically homogeneous and could be useful in understanding better the genetics of a complex disease like breast cancer (BC). PATIENTS AND METHODS: Using a screening assay based on a combination of single-strand conformation polymorphism, denaturing high-performance liquid chromatography and sequence analysis, 47 Sardinian families with three or more BC cases were screened for germline mutations in BRCA1 and BRCA2 genes. RESULTS: Three BRCA1/2 germline sequence variants were identified. While BRCA2-Ile3412Val is a missense variant with unknown functional significance, BRCA2-8765delAG and BRCA1-Lys505ter are two deleterious mutations (due to their predicted effects on protein truncation), which were found in seven families (15%). BRCA2-8765delAG was found in six of eight (75%) BRCA1/2-positive families and seven of 501 (1.4%) unselected and consecutively collected BC patients. Prevalence of BRCA1/2 mutations in BC families was significantly correlated with the total number of female BCs (P <0.01) and increased by the presence of (i) at least one case of ovarian or male BC, or (ii) three generations affected, or (iii) bilateral BC. CONCLUSIONS: Identification of such features should address BC patients and their families to genetic counseling and BRCA1/2 mutational analysis. In addition, this is the first report of a detailed BRCA1/2 mutation screening in Sardinia, having immediate implications for the clinical management of BC families.

Prevalence and prognostic role of microsatellite instability in patients with rectal carcinoma.

BACKGROUND: Association between microsatellite instability (MSI) and favorable postoperative survival in patients with colorectal cancer receiving adjuvant chemotherapy has been indicated. To evaluate whether an analogous positive prognostic role of MSI could be present in rectal carcinoma (RC; most RC patients receive adjuvant radiotherapy), PCR-based microsatellite analysis of archival RCs and statistical correlation with clinico-pathological parameters were performed. PATIENTS AND METHODS: DNA from paraffin-embedded paired samples of tumors and corresponding normal tissue from 91 RC patients was analyzed for MSI using five microsatellite markers (tumors were classified as MSI(+) when two or more markers were unstable). RESULTS: Seventeen (19%) RC patients exhibited a MSI(+) phenotype. Prevalence of instability was found in patients with earlier RC onset (28% in cases with diagnosis age < or =55 years versus 15% in cases >55 years), whereas similar MSI frequencies were observed in patients with different disease stage or receiving different adjuvant therapies. While MSI was detected in seven (64%) of 11 familial patients, a remarkably lower MSI incidence was observed in sporadic cases (10/80; 12.5%). A significant association with better disease-free survival (DFS) and overall survival (OS) was found for MSI(+) patients (median DFS/OS, 30/32 months) in comparison to MSI(-) ones (median DFS/OS, 18/21 months) (P <0.001). CONCLUSIONS: MSI was demonstrated to be a strong molecular prognostic marker in rectal carcinoma, independent of the administered treatment (radiotherapy, chemotherapy or both).

Identification of a founder BRCA2 mutation in Sardinia.

Sardinian population can be instrumental in defining the molecular basis of cancer, using the identity-by-descent method. We selected seven Sardinian breast cancer families originating from the northern-central part of the island with multiple affected members in different generations. We genotyped 106 members of the seven families and 20 control nuclear families with markers flanking BRCA2 locus at 13q12-q13. The detection of a common haplotype shared by four out of seven families (60%) suggests the presence of a founder BRCA2 mutation. Direct sequencing of BRCA2 coding exons of patients carrying the shared haplotype, allowed the identification of a 'frame-shift' mutation at codon 2867 (8765delAG), causing a premature termination-codon. This mutation was found in breast cancer patients as well as one prostate and one bladder cancer patient with shared haplotype. We then investigated the frequency of 8765delAG in the Sardinian breast cancer population by analysing 270 paraffin-embedded normal tissue samples from breast cancer patients. Five patients (1.7%) were found to be positive for the 8765delAG mutation. Discovery of a founder mutation in Sardinia through the identity-by-descent method demonstrates that this approach can be applied successfully to find mutations either for breast cancer or for other types of tumours.