FOS and breast cancer: Overexpression of the miR-200c/141 cluster in breast cancer cells was also observed, with elevated mRNA expression of various transcription factor members, including c-Jun, c-Fos, and FosB mRNAs, nuclear import event of c-Jun, and induction of SerpinB2 promoter-directed chloramphenicol acetyltransferase (CAT) activity.