Data from Concurrent Suppression of Integrin α<sub>5</sub>, Radixin, and RhoA Phenocopies the Effects of miR-31 on Metastasis

miR-31 inhibits breast cancer metastasis via the pleiotropic suppression of a cohort of prometastatic target genes that include integrin α₅ (ITGA5), radixin (RDX), and RhoA. We previously showed that the concomitant overexpression of ITGA5, RDX, and RhoA was capable of overriding the antimetastatic effects of ectopically expressed miR-31 in vivo. However, these prior studies failed to investigate whether the combined suppression of the endogenous mRNAs encoding these three proteins recapitulated the in vivo consequences of miR-31 expression on metastasis. We show here that short hairpin RNA–mediated concurrent downregulation of ITGA5, RDX, and RhoA is sufficient to phenocopy the full spectrum of described influences of miR-31 on metastasis in vivo, including the effects of this microRNA (miRNA) on local invasion, early post-intravasation events, and metastatic colonization. These findings provide mechanistic insights into the metastatic process and have implications about the importance of pleiotropy for the biological actions of miRNAs. Cancer Res; 70(12); 5147–54. ©2010 AACR.