Evidence has revealed that some microRNAs play a critical role in tumor proliferation. We demonstrated that miR-141-3p appears to be a novel oncogene miRNA, which promotes prostate tumorigenesis and facilitates the sternness of prostate cancer cells via suppressing a key transcription factor kruppel-like factor-9 (KLF9). KLF9 is the core effector protein that might suppress tumor growth. MiR-141-3p is upregulated in prostate cancer cells and tissues compared to non-tumorigenic prostate epithelial cells and prostate tissues. MiR-141-3p positively regulated proliferation, spheroid formation, and expression of the sternness factors OCT-4, Nanog, SOX-9, Bmil, CCND1, and CD44 in PC-3 cells. Restoration of miR-141-3p suppresses the expression of the transcription factor KLF9 in PC-3 and accelerates prostate tumorigenesis via targeted binding with its 3'-UTR. Downregulation of KLF9 enhances spheres formation of prostate cancer cells. Our results suggest that miR-141-3p/KLF9 may play an important role in regulating the growth of prostate cancer and is a potential target of prevention and therapy. (C) 2016 Elsevier Inc. All rights reserved.