Abstract P4-13-01: Trancriptome sequencing of the hisologicaly normal breast epithelium of BRCA mutation carriers
Authors: Baptiste Dadrie , Choi MiRan , Wang Zhiping , Liu Yunlong , Radovich Milan , Clare Susan E 
Published: May 2015

Background: Meaningful progress in the prevention of breast cancer is unlikely until the risk of the development of breast cancer is translated into specific, quantifiable molecular alterations. Among those women at the greatest risk are BRCA mutations carriers: 55 to 65% of women who inherit a deleterious BRCA1 mutation and approximately 45 % who inherit a deleterious BRCA2 mutation will develop breast cancer by age 70 years. The purpose of this study was to identify the earliest transcriptional alterations present by examining the histologically normal breast epithelia of BRCA mutation carriers.

Methods: Epithelia were microdissected and the RNA isolated from the histologically normal breast of 16 frozen tissue cores from known BRCA mutation carriers, who were donors to the Susan G. Komen for the Cure Tissue Bank at the IU Simon Cancer Center. RNA-sequencing was carried out using the Life Technologies SOLiD XL 5500 Platform. RPKM gene expression values from the BRCA specimens and from Komen normal breast epithelium (controls; Pardo et al, Breast Cancer Research, 2014) were merged, quantile normalized, and batch effect corrected. Normalization and differential gene expression was performed using EdgeR v2.11

Results: 6583 RNAs were differentially expressed with the false discovery rate set at 0.1.

1. DNA damage is signaled by a tripartite system that includes kinases, phosphatases and proteins with modular domains, e.g., the BRCA 1 C-terminal (BRCT), that recognize phosphorylated linear motifs in other proteins. Several BRCT domains recognize motifs phosphorylated by kinases that are activated by DNA damage. To identify the proteins active in DNA damage signaling, Monteiro and colleagues generated a protein-protein interaction map for seven proteins with tandem BRCT (Cell Signaling, 2012). A significant proportion of the genes with decreased expression in our data set encode proteins that have been identified in this network.

2. Two of the top biological processes affected by the BRCA mutations in the histologically normal breast tissue are translation, and cellular protein metabolism.

3. There was significantly less expression of genes associated with other hereditary cancer syndromes inducing the genes responsible for Lynch Syndrome: MHL1, MHS2, MSH6 and PMS2; and the multiple endocrine neoplasia genes RET and MEN1.

4. High grade serous carcinoma of the ovary, the histologic subtype associated with BRCA mutation, may originate in the distal Fallopian tube. The list of differentially expressed genes from microdissected breast epithelia was compared with that derived from gene array profiling of microdissected Fallopian tube epithelium from histologically normal BRCA1 mutation carriers and controls. 795 genes were common to both gene sets, of which 354 were regulated similarly, i.e., increased or decreased. MetaCore data analysis revealed CREB1 and c-Myc as the most important regulatory factors in the similar dataset.

Conclusions: There are significant transcription alterations in the histologically normal breast tissue of BRCA mutation carriers. These data will have to be corroborated at the protein level and functional level. Once substantiated, they have potential to stratify risk and to serve as targets for prevention.

Citation Format: Dadrie Baptiste, MiRan Choi, Zhiping Wang, Yunlong Liu, Milan Radovich, Susan E Clare. Trancriptome sequencing of the hisologicaly normal breast epithelium of BRCA mutation carriers [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-13-01.