Although we have shown than p38 MAPK is a significant regulator of DKK-1 in prostate cancer, there are other known regulators of DKK-1 expression in other cancer types such as JNK signaling induced by oxidative stress in multiple myeloma,51 and Wnt signaling, which negatively regulate DKK-1 in a feedback loop involving the beta-catenin/TCF pathway in prostate and liver hepatocellular carcinomas.52 This evidence concerns the gene HNF4A and plasma cell myeloma.