Therefore, the breast cancer cell lines SK-BR-3, T-47D and MCF7 were selected as Trop-2 high- and CD-49f low-expressing controls and the cell line MDA-MB-231 was used as a model for CD-49f high- and Trop-2 low-expressing tumour cells, shown by flow cytometry. This evidence concerns the gene ITGA6 and breast cancer.