A reduction in lung colony formation index was observed in animals injected with J7-DKK4 and J7-TRα1 cells compared with those injected with J7-control cells. The arrowheads indicate the lung colonies. All lines of SCID mice developed multiple macroscopic tumor nodules in the lung, as shown by H&E staining (Fig. 5C). However, the average

lung colony formation index and tumor size were reduced 75%-95% in animals injected with J7-DKK4 and J7-TRα1 cells compared with those injected with J7-control cells (Fig. 5D). Similar results were observed using HepG2-TRβ1 stable cell lines using an in vitro assay (Fig. 6). Briefly, three HepG2 isogenic cell lines (HepG2-control, HepG2-DKK4, Crizotinib cell line and HepG2-TRβ1) were established. Expression levels of TR and DKK4 proteins in those three cell lines were determined. The DKK4 protein was increased both in the HepG2-DKK4 and HepG2-TRβ1 cell lines (Fig. 6A). We verified the effect of DKK4-overexpression in HepG2-DKK4 and HepG2-TRβ1 cells, showing that invasiveness Sorafenib molecular weight was inhibited by 60%-70% in both cell lines (Fig.

6B,C). Images of cell density for three cell lines are shown (Fig. 6B). An examination of the expression of downstream Wnt signaling molecules in HepG2-DKK4 and HepG2-TRβ1 cell lines showed that β-catenin, cyclin D1, and c-Jun were significantly decreased in HepG2-DKK4 and HepG2-TRβ1 compared with control cell lines (Fig. 6D; Supporting Fig. 3). To examine medchemexpress whether invasion ability can be restored by knocking down DKK4, we established HepG2-TRβ1 knockdown (KD) cell lines expressing short hairpin RNA (shRNA) against DKK4 (TRβ1-DKK4-KD1 and 2) and a control cell line expressing scrambled shRNA (TRβ1-Scr). To verify the expression levels of both DKK4 and TR protein in the three HepG2-TRβ1 cells, we incubated the cell lines with 1 nM T3 for 24 hours to induce DKK4 (Fig. 7A). DKK4 protein level in TRβ1-DKK4-KD1 and TRβ1-DKK4-KD2 cells were decreased to 0.28- and 0.2-fold those in HepG2-TRβ1-Scr cells, respectively (Fig. 7A). The invasivity of HepG2-TRβ1-DKK4-KD cells

was increased by 3- to 3.4-fold compared with HepG2-TRβ1-Scr cells (Fig. 7B; Supporting Fig. 4A). Images of cell density are shown (Fig. 7B). To determine the effect of DKK4 on the Wnt-canonical signaling pathway, we measured the expression of several proteins involved in this pathway in HepG2-TRβ1 cells. β-Catenin was significantly up-regulated (by 1.2- to 2.1-fold) in the two DKK4-KD cell lines compared with control cells. Similarly, cyclin D1 and c-Jun proteins were significantly up-regulated by 1.35- to 1.9-fold in the two DKK4-KD cell lines (Fig. 7C; Supporting Fig. 4B). Zymography assays revealed that these increases were associated with a 1.4- to 1.55-fold increase in MMP2 activity in TRβ1-DKK4-KD cells (Fig. 7D; Supporting Fig. 5C). These results indicate that TRs may act as tumor suppressors in hepatoma cells by inducing the expression of DKK4 and reducing signaling through the Wnt/β-catenin pathway.