Abstract 1080: Effect of IGF2 overexpression on the tumorigenicity of human ovarian carcinoma cells

Abstract

Introduction High Insulin-like Growth Factor 2 (IGF2) tumor expression correlates with reduced disease-free survival in epithelial ovarian tumors. IGF2 mRNA is also upregulated after Taxol treatment of ovarian cancer cells. The purpose of this study was to determine the effect of IGF2 overexpression on the tumorigenicity of human ovarian cancer cells. Methods HEY cells were stably transfected using lentiviral particles with IGF2 or no insert (EV) constructs. qPCR and ELISA were performed to measure the IGF2 mRNA and secreted protein expression levels, respectively. Signaling pathways were probed by immunoblotting. Tumorigenicity was evaluated in athymic nude mice by subcutaneous injection of serial cell dilutions with matrigel, followed by monitoring of in vivo tumor growth by caliper measurements. qPCR for IGF2 mRNA and immunohistochemistry for Ki67 were performed on the excised tumors. Results The IGF2 mRNA level was 4679 ±176 fold-change higher in HEY-IGF2 cells relative to HEY-EV cells (P<0.0001). The amount of IGF2 protein secreted in 48 h was 5159 ng/100,000 HEY-IGF2 cells (51.6 pg/cell), and undetectable in the media of HEY-EV cells. Tyrosine phosphorylation of the IGF1-receptor was increased 13-fold in HEY-IGF2 cells. In vitro, dependency on the IGF1-receptor signaling was unaltered, as IGF2 overexpressing cells responded similarly to the IGF1-receptor inhibitor NVP-AEW541 compared to HEY-EV cells. Following an injection of one million cells with matrigel, the mean tumor volume of xenografts after 4 weeks was 1608 ±330 mm3 versus 705 ±95 mm3 for HEY-IGF2 and HEY-EV xenografts, respectively (P=0.04, N=6 per group). Immunohistochemistry for Ki67 showed a significantly higher percentage of stained nuclei in HEY-IGF2 tumors than in HEY-EV tumors (P=0.04, N=3 per group). Discussion Stable overexpression of IGF2 in HEY ovarian cancer cells resulted in an increased xenograft growth rate. Further evaluation is underway to fully characterize the mechanisms by which IGF2 overexpression promotes tumor growth. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1080. doi:1538-7445.AM2012-1080