(Cancer Cell 29, 145–158; February 8, 2016) After the publication of this paper, the authors found four small errors in Figure 3. In Figure 3A, the label p38P on the right side of the second blot from the top should be p38, and the label MK2 on the right side of the second blot from the bottom should be MK2P. In addition, the pTAK1 and pMK2 blots in Figure 3C were inadvertently stretched out during figure preparation. These errors have now been corrected here and in the article online. The authors apologize for these errors and any inconvenience that may have resulted.