Role of DKK4 in Tumorigenesis and Tumor Progression.

Tumor is the most public health problem. The Wnt signal pathway extensively participates in diverse progresses containing embryonic development, maintenance of homeostasis and tumor pathogenesis. The Wnt signal pathway consists of canonical signal pathway, noncanonical Wnt/PCP pathway and noncanonical Wnt/Ca2+ pathway. The deletion of the ligand of Wnts results in cytoplasmic β-catenin phosphorylation, stopping entry of β-catenin to nuclear in canonical Wnt signaling. Instead, binding of Wnts to frizzled (FZ/FZD) as well as LRP5/6 causes activation of Wnt signal pathways. This facilitates entry of β-catenin to nuclear. The Dickkopf proteins (DKKs) have been known as the antagonist of Wnt signal pathway. A number of research of DKK1, 2, 3 have been reported, however, the effect of DKK4 on tumor process is still mysterious. A more distinct comprehension about the effect of DKK4 on tumorigenesis and tumor process will shed light on biomedical research of DKK4 and tumor research. This review summarizes the current knowledge of DKK4 in various kinds of tumors.