Heterotypic cell hybridization, facilitated by apoptosis via the phosphatidylserine receptor-associated PtdSer-BAI1 signaling pathway [70], involves an interaction between the fusogenic retroviral envelope protein “syncytin” (the ligand on cancer cells) and the syncytin receptor (alanine/serine/cysteine transporter-2, ASCT-2) expressed on ECs [71]. This evidence concerns the gene ERVW-1 and cancer.