Metastasis

is a development of secondary tumor growths at a distance from the primary site

and closely related to poor prognosis and mortality. However

there is still no effective treatment for metastatic cancer. Therefore

there is an urgent need to find an effective therapy for cancer metastasis. Plenty of evidence indicates that miR-9 can function as a promoter or suppressor in cancer metastasis and coordinate multistep of metastatic process. In this review

we summarize the different roles of miR-9 with the corresponding molecular mechanisms in metastasis of twelve common cancers and the multiple mechanisms underlying miR-9-mediated regulation of metastasis

benefiting the further research of miR-9 and metastasis

and hoping to bridge it with clinical applications.