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Introduction. Breast papillary lesions represent a heterogeneous group of tumors ranging from benign to malignant, including several intermediate forms. Malignant papillary tumors are rare and their molecular characterization is still limited. A few studies pointed to the presence of specific genetic alterations that could be relevant both for diagnostic purposes and to elucidate tumour development and progression. In order to look into the issue, we compared LOH relative frequencies of four microsatellite markers located on chromosome 16 in a set of morphologically different papillary breast lesions. LOH at TP53 locus was also analyzed throughout lesions. Materials and methods. Fifteen cases were analyzed. Sections including a malignant papillary lesion, a benign lesion (when available), and normal breast tissue were selected. Fifteen malignant and twelve benign areas were microdissected using the Leica laser microdissection system (AS LMD). After DNA extraction samples were tested for the following markers: TP53, D16S423, D16S310, DS163210 and D16S476, and analyzed on ABI PRISM 3100 (Applied Biosystems, Foster city CA). Results. Fourteen malignant lesions and twelve paired benign areas appeared to be informative for at least one of the four markers on chromosome 16. In particular, LOH at loci 16p13 and 16q21 was detected in both benign and malignant lesions, whereas LOH at locus 16q23 was limited to malignant lesions. Nine malignant and seven benign lesions were informative for LOH at TP53 locus, that was found to be significantly associated (p=0.01) with the malignant phenotype. Conclusions. Our data suggest an involvement of chromosome 16 mutations in the early steps of breast papillary tumorigenesis. TP53 deletion and possibly LOH at 16q23 appear to play a role as progression factors, being they significantly associated with malignant transformation of breast papilloma.

Mutations in BRCA1 and BRCA2 show different expressivity with respect to cancer risk, and allelic heterogeneity may be present in both genes. We collected 179 pedigrees with identified germline mutation (104 BRCA1 and 75 BRCA2), ascertained in six collaborating centers of the Italian Consortium for Hereditary Breast and Ovarian Cancer. Significant heterogeneity was detected for several variables, and a logistic regression model including age of diagnosis in the proband, presence of ovarian cancer in the family, presence of prostate or pancreatic cancer in the family, and presence of male breast cancer in the family proved to be effective in predicting the presence of a mutation in a gene rather than the other. Excess of familial aggregation of both breast and ovarian cancer was observed in both genes. Proportion of ovarian cancer was increased in the 5' portion of BRCA1, and presence of prostate or pancreatic cancer in a family was correlated with presence of ovarian cancer in BRCA2.

M1775R and A1789T are two missense variants located within the BRCT domains of BRCA1 gene. The M1775R is a known deleterious variant, while the A1789T is an unclassified variant that has been analyzed and classified as probably deleterious for the first time by our group. In a previous study, we described the expression profile of HeLa G1 cells transfected with the two variants and we found that they altered molecular mechanisms critical for cell proliferation and genome integrity. Considering that the mutations in the BRCA1 C terminus (BRCT) domains are associated to a phenotype with an altered ability in the DNA double-strand break repair, we chose three of the genes previously identified, EEF1E1, MRE11A, and OBFC2B, to be tested for an homologous recombination (HR) in vitro assay. For our purpose, we performed a gene expression knockdown by siRNA transfection in HeLa cells, containing an integrated recombination substrate (hprtDRGFP), for each of the target genes included BRCA1. The knockdown of BRCA1, OBFC2B, MRE11A, and EEF1E1 reduces the HR rate, respectively, of 97.6, 28.6, 41.8, and 42.3 % compared to cells transfected with a scrambled negative control duplex and all these differences are statistically significant (P