Abstract 1124: IGFBP-4 activates the Wnt/beta-catenin signaling pathway and induces M-CAM expression in human renal cell carcinoma

Abstract

Abstract Introduction and Objective : The Wnt/beta-catenin signaling pathway is inactivated by Wnt antagonists in most cancers. IGFBP-4 is an antagonist of the Wnt/beta-catenin signaling pathway, however its function is not currently understood in renal cell carcinoma (RCC). Methods : The expression levels of IGFBP-4 protein in kidney tissue microarray were examined by immunostaining using antibody to IGFBP-4. The IGFBP-4 mRNA expression level was analyzed in a normal kidney cell line (HK-2), primary renal cancer cell lines (A498, 769-P) and metastatic renal cancer cell lines (ACHN, Hs891.T). To examine the function of IGFBP4, MTS, matrigel invasion, colony formation and wound healing assays were performed using 769-P mock and stable IGFBP-4 transfected cells. To screen for metastatic related genes in IGFBP-4 stable cells, cDNA PCR array was performed with a Human RT2 Profiler PCR Array. We investigated mRNA expression of the MMP family and measured Tcf transcriptional activity to monitor the Wnt/beta-catenin dependent pathway in 769-P mock and IGFBP-4 stable transfected cells. To analyze the role of IGFBP-4 in metastatic RCC cell lines, IGFBP-4 mRNA was knocked down using a siRNA technique. Results : We found that the expression of IGFBP-4 was significantly lower in primary RCC and higher in metastatic RCC compared to normal human kidney tissues. To assess the function of IGFBP4, we established IGFBP4 transfectants (primary renal cancer cell line) and performed functional analyses including Tcf reporter assays, cell viability, invasive capability, mortality, and in vivo tumor growth. Interestingly IGFBP-4 transfectants promoted cell growth (in vitro and in vivo), invasion, and motility in 769-P cancer cells. Tcf transcriptional activity was significantly increased in IGFBP-4 transfectants compared to mock cells and beta-catenin expression was increased. Also the beta-catenin downstream effector, MT1-MMP showed increased expression in IGFBP4 transfectants. Additionally IGFBP4 induced the expression of M-CAM, a marker of tumor progression. In order to assess the role of IGFBP4 in metastatic renal cancer, IGFBP-4 mRNA in a metastatic renal cancer cell line (ACHN) was knocked-down using a siRNA technique. Cell growth and motility was decreased in si-IGFBP4 transfected ACHN cells compared to cells transfected with control siRNA. Conclusions : This is the first report documenting that IGFBP-4 expression in RCC activates cell growth, metastasis, Wnt/beta-catenin signaling and may be involved in RCC metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1124. doi:10.1158/1538-7445.AM2011-1124