SYK expression level distinguishes control from BRCA1-mutated lymphocytes

Abstract

Tamar Zahavi,1,2,* Amir Sonnenblick,1,3,* Yael Shimshon,2 Luna Kadouri,1 Tamar Peretz,1 Asher Y Salmon,1,* Mali Salmon-Divon,2,* 1Sharett Institute of Oncology, Hadassah Hebrew University Medical Center, Jerusalem, Israel; 2Genomic Bioinformatics Laboratory, Department of Molecular Biology, Ariel University, Ariel, Israel; 3Sackler Faculty of Medicine, Sourasky Medical Center, Institute of Oncology, Tel Aviv University, Tel Aviv, Israel *These authors contributed equally to this work Background: About 5%–10% of breast cancer and 10%–15% of ovarian cancer are hereditary. BRCA1 and BRCA2 are the most common germline mutations found in both inherited breast and ovarian cancers. Once these mutations are identified and classified, a course of action to reduce the risk of developing either ovarian or breast cancer – including surveillance and surgery – is carried out. Purpose: The purpose of the current research is to characterize the gene expression differences between healthy cells harboring a mutation in BRCA1/2 genes and normal cells. This will allow detection of candidate genes and help identify women who carry functional BRCA1/2 mutations, which cannot always be detected by the available sequencing methods, for example, carriers of mutations found in regulatory sequences of the genes. Materials and methods: Our cohort consisted of 50 healthy women, of whom 24 were individuals with BRCA1 or BRCA2 heterozygous mutations and 26 were non-carrier controls. RNA purified from non-irradiated lymphocytes of nine BRCA1/2 mutation carriers versus four control mutation-negative individuals was utilized for RNA-Seq analysis. The selected RNA-Seq transcripts were validated, and the levels of spleen tyrosine kinase (SYK) mRNA were measured by using real-time quantitative polymerase chain reaction. Results: Differences in gene expression were found when comparing untreated lymphocytes of BRCA1/2 mutation carriers and controls. Among others, the SYK gene was identified as being differently expressed for BRCA1/2 mutation carriers. The expression level of SYK was significantly higher in untreated healthy lymphocytes of BRCA1 heterozygote carriers compared with controls, regardless of irradiation. In contrast to normal tissues, in cancerous breast tissues, the expression levels of the BRCA1 and SYK genes were not intercorrelated. Conclusion: Collectively, our observations demonstrate that SYK may prove to be a good candidate for better diagnosis, treatment, and prevention of BRCA1 mutation-associated breast cancer. Keywords: RNA-Seq, breast cancer susceptibility, peripheral blood

Keywords

• RNA-seq
• breast cancer susceptibility
• peripheral blood