Abstract 3100: The RNA-binding protein insulin-like growth factor 2 mRNA-binding protein 3 is oncogenic in liposarcoma

Abstract

Abstract Introduction: The insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) is an oncofetal mRNA binding protein that controls migration and proliferation through post-transcriptional regulation of target genes. It is aberrantly expressed in various cancers. We sought to determine the alterations in IGF2BP3 expression and copy number in well-differentiated (WD) and dedifferentiated (DD) liposarcoma (LS) and elucidate its role in driving oncogenesis in WD and DD LS cell lines. Methods: U133A microarray analysis was performed on 61 DD and 52 WD LS as well as 17 normal fat (NF) tissue samples. CGH Agilent arrays were used to determine IGF2BP3 amplification status. An shRNA lentiviral system was used to knockdown (KD) IGF2BP3 in DD (DDLS8817, LPS141) and WD (RWD3051) cell lines. Cell proliferation, apoptosis, and mRNA expression were analyzed by Cyquant, annexin V, and qRT-PCR, respectively. Results: CGH analysis showed IGF2BP3 amplification in 19% of DDLS (n=36) and 5% of WDLS (n=36) tumor samples. On U133A analysis IGF2BP3 was 2.5-fold and 1.2-fold upregulated in DDLS and WDLS, respectively, compared to NF. IGF2BP3 was overexpressed in 49% of DDLS and 33% of WDLS tumor samples. Gene expression was increased in DDLS8817 (3-fold), LPS141 (6-fold) and RWD3051 (6-fold) compared to adipose-derived stem cells. IGF2BP3 KD reduced expression >95%(p<0.05) compared to empty vector control for each cell line. IGF2BP3 KD decreased proliferation by 43%, 31%, and 36%(p<0.001) in DDLS8817, LPS141 and RWD3051, respectively, compared to control. Apoptosis was increased by 34%, 55%, and 58%(p<0.0001) compared to control in DDLS8817, LPS141, and RWD3051, respectively, and correlated with level of IGF2BP3 upregulation. p27, a cell cycle inhibitor, was identified as a potential target of IGF2BP3 by photoreactive crosslinking and immunoprecipitation. On Western blot analysis p27 was increased, cyclin D1 was decreased, and p53 was decreased in IGF2BP3 KD compared to control in LPS141, consistent with the functional effects observed. Conclusions: IGF2BP3 overexpression is essential for proliferation and survival of LS cells. The cell cycle regulator, p27 was identified as an IGF2BP3 target mediating these functional effects. Identification of additional IGF2BP3 targets may lead to new therapeutic options for patients with DD and WD liposarcoma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3100.