Secreted WNT antagonists as tumor suppressors: pro and con.

1. Abstract2. Wnt signaling and cancer3. Secreted Wnt antagonists4. Secreted Wnt antagonists as tumor suppressors4.1. sFRPs4.2. WIF-14.3. Dkks5. Secreted Wnt antagonists as promoters of tumor growth6. Possible mechanisms to account for disparate activities of Wnt antagonists7. Perspective8. Acknowledgements9. References