Abstract #4810: The metastasis suppressor RhoGDI2 suppresses expression of Versican,
an invasion associated and macrophage stimulatory molecule

Abstract

Nearly half of bladder cancer patients that present with locally advanced disease have occult distant metastases at presentation and poor 5-year survival rate. In human bladder cancer, reduction of Rho GDP Dissociation Inhibitor 2 (RhoGDI2) has been identified as an independent prognostic marker of tumor metastasis in patients with locally advanced disease and a lung metastasis suppressor gene in animal models of the disease. To determine how this protein affects metastasis, we transfected and stably expressed a RhoGDI2 transgene in the RhoGDI2 negative and metastatic UMUC3 human bladder cancer cell line and carried out expression profiling. The genes differentially expressed among the UMUC3-GFP (control) and UMUC3-RhoGDI2 cells were then evaluated against a panel of genes that were recently found to be associated with bladder cancer migration in vitro and invasion in patients (Wu Y et al, Oncogene. 2008, 27(52):6679). This analysis revealed that chondroitin sulfate proteoglycan 2 (CSPG2), versican, was downregulated by RhoGDI2 as well as positively correlated with bladder cancer stage and in vitro migration of bladder cancer cell lines. Confirmation of gene expression profiling by qPCR and western revealed that RhoGDI2 transfected UMUC3 cells had reduced expression and secretion of versican isoforms V1 and V2 as compared to vector control cells. Silencing versican expression in parental UMUC3 cells by small interfering RNA (siRNA) resulted in significant decrease in UMUC3 cell migration. Since versican has been shown to be a stimulator of macrophage activity which in turn is a promoter of the metastatic tumor growth, we evaluated the effect of versican depletion on bladder cancer macrophage cross talk in vitro. Versican siRNA in UMUC3 resulted in a ~60% inhibition of macrophage-induced UMUC3 cell migration, as well as ~50% decrease in UMUC3-induced macrophage chemotaxis. These effects were similar in magnitude to those observed with RhoGDI2 transfection in UMUC3 cells. Together these findings indicate that metastasis suppressor effect of RhoGDI2 may in part be mediated through downregulation of versican and subsequent attenuation of cancer cell-macrophage cross-talk.

Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 4810.