KLF5 and prostate cancer: Though it is well known that WWP1 acts as an oncoprotein in breast and prostate cancers, WWP1-mediated ubiquitination and subsequent degradation of KLF5 indicate that WWP1 functions as a tumor suppressor via dampening KLF5’s positive regulation on cell survival and metastasis of these tumors under some circumstances (Chen et al., 2005).