Diagnostic Value of Serum DKK1 Levels in Cancer Detection: a Case-Control Study and Meta-analysis

Dickkopf-related protein 1 (DKK1) is a member of the Dickkopf gene family, which is comprised of five evolutionarily conserved members, DKK1-4 ,and a unique DKK3-related member, DKKL1 (Dickkopf-like protein 1, Soggy) (Katoh and Katoh, 2005). Dickkopf-1 is a 35kDa secreted protein involved in embryonic development; it plays a critical role in cell patterning, proliferation, and fate determination during embryogenesis as a potent inhibitor of the Wnt signaling pathway (Ogoshi et al., 2011). Unlike in normal development, the role of DKK1 in cancer is not as well characterized. DKK1 is upregulated in certain tumor types, including breast cancer (Forget et al., 2007), hepatoblastomas, and Wilms’ tumor (Wirths et al., 2003). Some studies showed that DKK1 levels have also been associated with cancer progression and poor prognosis. DKK1 is overexpressed in prostate, lung, esophageal, and hepatic cancers, and, in these diseases, it may serve as a serologic and prognostic biomarker (Yamabuki et al., 2007). DKK1 is frequently