A heterotypic cell fusion assay was set up with the three M13SV1 cell lines (wild type, ASCT2KO, Syn1 overexpression), which were freshly transfected with an miCP vector coding for the iCre recombinase and the three breast cancer cell lines MDA-MB-231_pFDR.2, MDA-MB-435S_pFDR.1 and HS578_pFDR.2. This evidence concerns the gene SYN1 and breast cancer.