Dickkopf 3 Inhibits Invasion and Motility of Saos-2 Osteosarcoma Cells by Modulating the Wnt-β-Catenin Pathway

Abstract

Osteosarcoma (OS) is a primary malignancy of bone with a tendency to metastasize early. Despite intensive chemotherapy and surgical resection, ϳ30% of patients still develop distant metastasis. Our previous work using clinical OS samples suggested that expression of the Wnt receptor LRP5 might be associated with tumor metastasis. In the present study, we used a Dickkopf (Dkk) family member and a dominant-negative LRP5 receptor construct to modulate Wnt signaling in OS cells. Saos-2 cells, which ectopically express Dkk-3, do not undergo apoptosis and exhibit enhanced resistance to serum starvation and chemotherapy-induced cytotoxicity. Transfection of Dkk-3 and dominant-negative LRP5 into Saos-2 cells significantly reduces invasion capacity and cell motility. This blockade is associated with changes in cell morphology consistent with a less invasive phenotype. In addition, Dkk-3 and dominant-negative LRP5 also induce changes in ␤-catenin localization consistent with an increase in cell-cell adhesion. Taken together, these results support a possible role for Wnt signaling in the pathobiology and progression of human OS.

Autonomous regulation of osteosarcoma cell invasiveness by Wnt5a/Ror2 signaling

“…It has been reported that an invasion index, corrected for cell motility, indicates specific contribution of ECM degradation and is of use to evaluate invasiveness of tumor cells (Albini, 1998;Hoang et al, 2004). In fact, significantly decreased invasion index was obtained when SaOS-2 cells were transfected with Ror2 siRNA #1 compared with control siRNA #1 transfection (Figure 2e).…”

“…The cells were incubated for 8 h (migration assay) or 24 h (invasion assay) (U2OS cells were incubated for 12 h (invasion assay)) and then the membranes were fixed in 3.7% formaldehyde. The evaluation of migrating or invasive cells was carried out as previously described (Hoang et al, 2004;Nishita et al, 2006). An invasion index was calculated as follows: (number of invasive cells per number of migrating cells) Â 100 (Albini, 1998;Hoang et al, 2004).…”

DKK3 blocked translocation of β‐catenin/EMT induced by hypoxia and improved gemcitabine therapeutic effect in pancreatic cancer Bxpc‐3 cell

“…As a Wnt antagonists, it is reported that DKK3 overexpression does not affect nuclear/cytoplasmic accumulation of β‐catenin 11. On the other hand, another article has shown that overexpression of DKK3 leads to a reduction in the cytoplasmic level of β‐catenin in SaOS‐2 cells 31. In a previous report, Xiang et al .…”

“…It has been shown that the expression of Wnt antagonists are often down‐regulated in several human cancers and DKK3 was no exception 29. There are reports on DKK3 both enhancing and repressing the Wnt signalling pathway 30, 31. Recently, DKK3 was also reported as playing distinct roles in different human pancreatic cancer cells, but not much is known about the detailed mechanism 20, 32.…”

Function and biological roles of the Dickkopf family of Wnt modulators

“…Hence, DKK3 is also known as 'REIC' (Reduced Expression in Immortalized Cells) . Furthermore, DKK3 overexpression suppresses tumor cell growth (Hoang et al, 2004;Abarzua et al, 2005;Lodygin et al, 2005;Kawano et al, 2006). While hypermethylation of human DKK3 correlates with …”