Overexpression of multiple epidermal growth factor like domains 11 rescues anoikis survival through tumor cells-platelet interaction in triple negative breast Cancer cells.

AIMS: The aim of this study was to test the hypothesis that overexpression of the Multiple Epidermal Growth Factor Like Domains 11 (MEGF11) gene in TNBC cells increases tumor cell survival against anoikis via interaction with platelets.

MAIN METHODS: The role of MEGF11 was studied in human TNBC MDA-MB-231 and MDA-MB-468 cells by overexpressing MEGF11 (o/e MEGF11) using non-attached culture. Mouse wild type 4 T1 and Δmegf11-4 T1 cells were implanted into the mammary fat pad of BALB/c mice. Circulating tumor cells were isolated and cultured. Plasma platelets were added to these cell lines to carry out a platelet binding assay by confocal microscopy. Anoikis was observed by Live/Dead staining and a quantitative PBMC-specific cytotoxic assay (with/without platelets) was carried out to measure calcein release. The protein levels of MEGF11, Akt, and caspase 3 were assessed by Western blotting.

KEY RESULTS: Reduced number of circulating Δmegf11 4 T1 cells, and 4 T1-platelet clusters and reduced p-Akt expression, accompanied by increased specific calcein release, were observed in the Δmegf11 4T1group compared to the 4 T1 wild type group. There was significant increased cancer-platelet binding using the o/e MEGF11 MDA-MB-231/468 lines. Cell survival, caspase 3 activation and PBMC-specific cytotoxicity in the o/e MEGF11 MDA-MB-468 cells, but not in the MDA-MB-231 cells, could be rescued by platelet binding (+), compared to the platelet (-) group.

SIGNIFICANCE: We conclude that MEGF11 overexpression in TNBC cells rescues tumor cells from anoikis via interaction with platelets in mouse 4 T1 cells and human MDA-MB-468 cells.