Del-1 and MFG-E8 expression to differentially modulate prognosis of patients with triple-negative breast cancer.

Abstract

e13093 Background: Del-1 was previously found to be prognostic biomarker in early breast cancer patients. Del-1 shares both structural and functional homology with Milk fat globule-epidermal growth factor-factor VIII (MFG-E8). To date, the biological functions of Del-1 and MFG-E8 have not been sufficiently compared in side-by-side experiments. MFG-E8 is a secreted glycoprotein from macrophages that promotes clearance of apoptotic cells. In this study, we investigated the function of MFG-E8 and Del-1 and prognosis in a large cohort of EBC patients. Methods: The MFG-E8 levels were measured using a qRT-PCR in breast cancer cells (MDA-MB-231, Hs578T, MCF7, SK-BR3, and T-47D), and tissues from 20 patients with EBC. The effects of MFG-E8 and Del-1 on cell proliferation, migration, and invasion were determined using MTT, wound healing, and Matrigel Transwell assays. The expressions of MFG-E8 and Del-1 protein were detected by immunohistochemical staining in 436 tumor tissues. The relationship between MFG-E8, Del-1 expression levels and clinicopathological features were evaluated. Results: MFG-E8 and Del-1 levels were significantly elevated in MDA-MB-231 and Hs578T cell lines (p < 0.001). Given that MFG-E8 and Del-1 share similar protein structure, we wanted to explore the effect of dual knockdown of MFG-E8 and Del-1 in migration and invasion assay. As expected, knockdown of Del-1 alone decreased cell migration in TNBC cell lines, but dual knockdown of MFG-E8 and Del-1 showed reduction was restored. Dual knockdown of MFG-E8 and Del-1 showed consistent result in invasion assay. Down-regulation of Del-1 inhibited TNBC cells invasion and recovered by the MFG-E8 knockdown. Interestingly, for the 436 patients, Del-1 high- and MFG-E8 low- expression shows correlation with aggressive histologic grade, high Ki-67 (p < 0.001 and p = 0.042, respectively) and shorter survival outcome (distant disease free survival p = 0.028, breast cancer specific survival p = 0.001). Conclusions: Overall, these findings suggest that MFG-E8 and Del-1 protein expression could be a prognostic marker for patients in triple negative breast cancer (TNBC). Thus, MFG-E8 reduction may contributes to tumorigenesis by increasing Del-1. However, functions of Del-1 and MFG-E8 have not yet been thoroughly analyzed, further studies are required.