Background: Secreted frizzled-related proteins (sFRP4) inhibits Wnt signaling and thus cellular proliferation in androgen-independent prostate cancer cells in vitro. However, increased expression of membranous sFRP4 is associated with a good prognosis in human localized androgen-dependent prostate cancer, suggesting a role for sFRP4 in early stage disease. Here, we investigated the phenotype of sFRP4 overexpression in an androgen-dependent prostate cancer model.
Methods: An sFRP4-overexpressing androgen-dependent (LNCaP) prostate cancer model was established to assess changes in cellular proliferation, the expression, and subcellular localization of adhesion molecules and cellular invasiveness, and compared with the findings in sFRP4-overexpressing androgen-independent cells (PC3).
Results: sFRP4 overexpression in both cell line models resulted in a morphologic change to a more epithelioid cell type with increased localization of beta-catenin and cadherins (E-cadherin in LNCaP, N-cadherin in PC3) to the cell membrane. Functionally, sFRP4 overexpression was associated with a decreased rate of proliferation (P = 0.0005), decreased anchorage-independent growth (P < 0.001), and decreased invasiveness in PC3 cells (P < 0.0001). Furthermore, increased membranous sFRP4 expression was associated with increased membranous beta-catenin expression (P = 0.02) in a cohort of 224 localized human androgen-dependent prostate cancers.
Conclusions: These data suggest that sFRP4 is an inhibitor of prostate cancer growth and invasion in vitro independent of androgen receptor (AR) signaling with correlative evidence in human androgen-dependent disease suggesting similar changes in the clinical setting. Consequently, potential therapeutic strategies to modulate Wnt signaling by sFRP4 will be relevant to both localized androgen-dependent prostate cancer and advanced metastatic disease.