*Molecular Mechanisms of Breast Cancer Metastasis DOI: http://dx.doi.org/10.5772/intechopen.108424*

receptor CXCR4, and vascular endothelial growth factor receptor (VEGFR) protein expression in BC cells [48]. miR-17-5p has been shown to have a unique antimetastatic action in recent investigations. Suppressing miR-17-5p resulted in increased prometastatic gene expression and increased metastasis to the lungs. On the other hand, intratumoral delivery of miR-17-5p mimics decreased lung metastasis considerably. Moreover, reduced miR-1179 expression in BC was linked to advanced clinical stage and metastases to the lymph node, according to a clinicopathological study [49]. When miR-1179 is upregulated, it suppresses BC cell proliferation and metastasis by regulating the expression of *NOTCH1*, *NOTCH4*, and its downstream modulators, *HES1* [50]. Last but not least, miR-21 overexpression in MDA-MB-231 cells decreases tumor invasive and metastatic characteristics. On the contrary, reduced miR-21 expression enhanced these cells' migration and invasion capabilities [51].
