A heterotypic cell fusion assay was set up with the three different M13SV1_DSP8-11 cell lines (wild type, ASCT2KO, Syn1 overexpression) and three breast cancer cell lines (MDA-MB-231, MDA-MB-435S and HS578T) expressing the DSP1-7 vector in a ratio of 1:3 for 72 h with or without the inflammatory cytokine TNFα as stimulus for cell fusion, with subsequent analysis of the cell fusion with flow cytometry and microscopy (Figure 7). The gene discussed is TNF; the disease is breast carcinoma.