Abstract 3820: Epigenetic re-expression of fetal IGF2 as therapeutic target in hepatocellular carcinoma

Background and aims Hepatocellular carcinoma (HCC) is a major health problem. Most patients are diagnosed at advanced stages when the only approved therapy is the multi-kinase inhibitor sorafenib. Consequently, there is a great need for the development of new effective treatments. IGF signaling pathway is aberrantly activated in HCC; however, its contribution to HCC pathogenesis is still unclear. Since IGF2 is overexpressed in HCC, we aimed to elucidate the oncogenic potential and mechanism of dis-regulation of this protein and determine the antitumoral efficacy of molecular abrogation of this ligand by targeted therapies. Methods Transcriptomic profiling, miRNAs expression, RNA- and whole exome- sequencing and methylation were analyzed in 228 HCCs with a focus on IGF-pathway. Gene Set Enrichment Analysis and Ingenuity Pathway Analysis were carried out in IGF2-overexpressing tumors. Stable HCC cell lines with knock-down and ectopic overexpression of IGF2 were generated. A chemically-induced mouse model of HCC, and two genetically-engineered mosaic mouse models (GEMM) overexpressing IGF2 specifically in the liver were generated to assess IGF2 oncogenicity in hepatocarcinogenesis. The therapeutic potential of a monoclonal-antibody against IGF-ligands (IGF1/2-mAb) alone or in combination with sorafenib was tested in a xenograft model of HCC. Results Here, IGF2-overexpression occurred in 15% of HCC patients as a result of the epigenetic reactivation of IGF2-fetal promoters, mainly through loss of promoters methylation (53% of cases) and deregulation of miR-216b, miR-483-5p and miR-let7-d (35% of cases). Re-expression of IGF2 was associated with a progenitor cell-like, poorly differentiated and aggressive subtype of HCC, and poor prognosis (p<0.0001). In a GEMM model, IGF2-overexpression accelerated HCC progression and reduced survival (p = 0.02). Conversely, IGF2-blockage using an IGF1/2-monoclonal antibody (mAb) or specific shRNAs against IGF2 reduced viability and proliferation in vitro (p<0.05), and inhibited IGF-Insulin pathway activation without disturbing insulin metabolism. IGF1/2-mAb delayed tumor growth and increased survival in vivo compared to placebo or sorafenib (p<0.0001), through antiproliferative and antiangiogenic mechanisms. Conclusions IGF2 is the first validated epidriver in HCC and has a key role in the hepatocarcinogenic process. These results provide the rationale for testing IGF1/2-mAb in a selected subset of HCC patients. Citation Format: Iris Martinez-Quetglas, Roser Pinyol, Daniel Dauch, Sara Torrecilla, Victoria Tovar, Agrin Moeini, Clara Alsinet, Anna Portela, Augusto Villanueva, Manel Esteller, Lars Zender, Josep M Llovet. Epigenetic re-expression of fetal IGF2 as therapeutic target in hepatocellular carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3820.