Abstract P6-02-02: mRNA expression of death associated protein 3 (DAP3) and human breast cancer: Clinical correlations and in vitro evidence

Abstract

Abstract BACKGROUND: To our knowledge, this study is the first to focus on the potential role for death-associated protein 3 (DAP3) in human breast cancer. MATERIAL AND METHODS: mRNA expression of DAP3 in breast cancer tissues (n = 127) and normal background tissues (n = 33) were determined using quantitative polymerase chain reaction (qPCR) and were correlated with clinico-pathological data accumulated over a 10-year follow-up period. Furthermore the effects of DAP3 knock down in breast cancer cell lines (MCF-7 and MDA-MB-231) were investigated. The cells were subjected to conventional growth, adhesion and invasion assays. In addition to the above, electric cell-substrate impedance sensing (ECIS) assay and annexin V/propidium iodide binding apoptosis assay were performed. For the apoptosis assay, the cells were subjected to 48 to 72 hours of serum hunger (depending on cell line) before being analyzed using a flow cytometer. RESULTS: The expression of DAP3 mRNA was demonstrated to decrease with increasing Nottingham Prognostic Index (NPI2 vs. NPI3, p = 0.036), TNM stage (TNM1 vs. 3, p = 0.07), and tumour grade (grade 1 vs. 3, p = 0.08). Lower DAP3 expression levels were significantly associated with local recurrence (p = 0.013), distant metastasis (p = 0.0057) and mortality (p = 0.019). Kaplan-Meier plot analysis suggests that patient with higher levels of DAP3 expression had better overall survival compared to patients with lower levels of DAP3 expression (p = 0.075). DAP3 knock down strains in both cell lines demonstrated increased growth and migration compared to controls during ECIS. In addition, DAP3 knock down strains of MCF-7 appeared more resistant to serum hunger when compared to controls during the apoptosis assay. CONCLUSIONS: This study demonstrates an inverse association between DAP3 mRNA levels and tumour stage and clinical stage in breast cancer. This is in keeping with the role of DAP3 as a pro-apoptotic protein. The in vitro evidence lends further credence to this hypothesis. The role of DAP3 may require further investigation to better understand the role of apoptosis in breast carcinogenesis, and may potentially serve as a prognostic marker for human breast cancer. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-02-02.