DKK1 and prostate carcinoma: In MM cell lines, which all lack detectable levels of DKK1 protein (Figure 1D and Figure S1), the DKK1 transcript was either undetectable (UM-1, RPMI 8226 and OPM-1), or weakly expressed (XG-1, L363 and LME-1) in comparison to the DKK1 expression in the (positive control) prostate cancer cell line PC-3 (Figure 3A) [29].