This article (1) is being retracted at the request of the authors. The images used in the second and third panels of CXCR4 siRNA in Fig. 1B were duplicated from the first and second panels of PC3-control cells in Fig. 1B of a previously published article that has since been retracted (2). The authors apologize to the scientific community and deeply regret any inconveniences or challenges resulting from the publication and subsequent retraction of this article. A copy of this retraction notice was sent to the last known email addresses for 13 of the 13 authors. Ten authors (Jinlu Dai, Younghun Jung, Yu Wang, Aaron M. Havens, Phillip J. Hogg, Evan T. Keller, Kenneth J. Pienta, Jacques E. Nor, Cun-Wu Wang, Russell Taichman) agreed to the retraction; three authors (Jianhua Wang, Jincheng Wang, and Chuen-Long Wei) did not respond.