Reports indicated that MFG-E8 secreted extracellularly despite its membrane associated nature. MFG-E8 was found to be a major component of secretory membrane vesicles (exosomes) secreted by murine dendric cell line, D1. The glioma cell line (C6) secrets MFG-E8 into the culture media. MFG-E8 is also detected in embryonic gonad extracellularly and in the sera of patients with metastatic tumor.