FOSL1 is frequently overexpressed in multiple types of human
cancers including invasive breast
cancers and implicated in
cancer invasion and
metastasis. However, how FOSL1 is overexpressed in
cancers remains to be elucidated. Several
microRNAs (
miRNAs) have been shown to target FOSL1 and are downregulated in human
cancers. Here, we report that miR-130a is a novel FOSL1 targeting
miRNA. Using gene expression microarray analysis, we found that FOSL1 is among the most up-regulated genes in cells transfected with miR-130a inhibitors. Transient transfection-immunoblot,
RNA-immunoprecipitation, and
luciferase reporter assays revealed that miR-130a directly targets FOSL1
mRNA at its 3'-UTR. Overexpression of miR-130a significantly reduced the levels of FOSL1 in invasive
breast cancer MDA-MB-231 and Hs578T cell lines and suppresses their migration and invasion. This inhibition can be rescued by ectopic expression of miR-130a-resistant FOSL1. Interestingly, we show that overexpression of miR-130a increased the levels of
tight-junction protein ZO-1 while inhibition of miR-130a reduced the levels of ZO-1. We further show that miR-130a expression is significantly reduced in
cancer tissues from
triple-negative breast cancer (TNBC) patients, correlating significantly with the upregulation of FOSL1 expression, compared to non-TNBC tissues. Together, our results reveal that miR-130a directly targets FOSL1 and suppresses the inhibition of ZO-1, thus inhibiting
cancer cell migration and invasion, in TNBCs.