The first, when miRNAs perform the conventional negative regulation to confer changes in the expression levels of target genes, e.g., reduced ZO-1 gene expression in endothelial cells and the promotion of lung and brain metastases by exosomal miR-105 released from the breast cancer cell lines MCF-10A and MDA-MB-231 [83]. This evidence concerns the gene TJP1 and breast cancer.