Wnt-5a/Ca²⁺-Induced NFAT Activity Is Counteracted by Wnt-5a/Yes-Cdc42-Casein Kinase 1α Signaling in Human Mammary Epithelial Cells

Abstract

Wnt-5a has been shown to influence the metastatic behavior of human breast cancer cells, and the loss of Wnt-5a expression is associated with metastatic disease. We show here that NFAT1, a transcription factor connected with breast cancer metastasis, is activated by Wnt-5a through a Ca²⁺ signaling pathway in human breast epithelial cells. This activation was simultaneously counteracted by a Wnt-5a-induced Yes/Cdc42 signaling pathway. The observation that inhibition of the Wnt-5a/Yes/Cdc42 signal prolonged the duration of ionomycin-induced NFAT1 activation revealed the general importance of this pathway. The Wnt-5a-induced inhibition of NFAT1 did not require glycogen synthase kinase 3β, JNK, or Pak1 activity or modulation of the cytoskeleton. Instead, we observed that Wnt-5a induced a complex formation of NFAT1/casein kinase 1α, even upon treatment with ionomycin, which was blocked upon inhibition of the Wnt-5a/Yes/Cdc42 signaling pathway. Our results explain why Wnt-5a/Ca²⁺-induced NFAT activity is hard to detect and suggest a novel mechanism by which Wnt-5a can suppress tumor-specific, agonist-induced NFAT activity and thus the metastatic behavior of breast cancer cells.

This study was supported by the Swedish Cancer Foundation (T.A.), the Medical Research Council (T.A.), the U-MAS Research Foundations (T.A. and K.L.), the Crafoord Foundation (K.L.), and the Royal Physiographic Society in Lund (J.D. and K.L.). K.L. was supported by a fellowship from the Swedish Society for Medical Research (SSMF).

We thank Lena Axelsson for help with invasion assays, J. Taylor-Papadimitriou for providing the HB2 cells, T. Leanderson for the NFAT-pGL2 plasmid, M. Sigvardsson for the TATA-pGL3 plasmid, P. Aspenström for the dnCdc42 and dnRac1 plasmids, B. Williams for the hLRP6 plasmid. We also thank Patricia Ödman for linguistic revision of the manuscript and T. Leanderson and Jill Howlin for scientific discussions and linguistic revision of the manuscript.