WISP-1 (Wnt-1-inducedsecreted protein) was identified as an oncogene regulated by the Wnt-1–β-catenin pathway. WISP-1 belongs to the CCN family of growth factors, which are cysteine-rich, heparin-binding, secreted proteins associated with the extracellular matrix, and can interact with cellular integrins. Expression of WISP-1 in some cells results in transformation and tumorigenesis. Here it is shown that WISP-1 can activate the antiapoptotic Akt/PKB signaling pathway. It also is demonstrated that WISP-1 can prevent cells from undergoing apoptosis following DNA damage through inhibition of the mitochondrial release of cytochrome c and up-regulation of antiapoptotic Bcl-X_L. Furthermore, the results show that WISP-1 protects cells from p53-dependent cell death, but not Fas-ligand activated cell death, suggesting that there may be cross talk between the tumor suppressor protein p53 and WISP-1 signaling pathways. WISP-1 acts to block cell death at a late stage in the p53-mediated apoptosis pathway.