WIF1 and cancer: SKP2 is frequently upregulated in cancers and is an important regulator of CDK inhibitor p27kip1, critical for the induction of cellular senescence.40, 42, 43 Earlier, Wnt antagonist, WIF1, was shown to repress SKP2 expression in urinary bladder cancer cells,50 and Wnt5a was shown to suppress epithelial ovarian cancer via promoting cellular senescence51 in a β-catenin-dependent manner.