To study the biological role of TLR4 in the progression of human breast cancer cell line MDA-MB-231, we constructed pGenesil-1 plasmid vectors expressing three different siRNAs directed against TLR4 [GenBank: NM_138554.3] to selectively reduce TLR4 gene expression in MDA-MB-231. This evidence concerns the gene TLR4 and breast cancer.