Abstract #444: Molecular and clinical characterization of RICTOR (MTORC2) as a candidate oncogene in hepatocellular carcinoma

Introduction: Recent data implicate mTOR signaling in human hepatocellular carcinoma (HCC). However, the specific contribution of mTOR complex components as either potential oncogenes or targets for therapies is unknown. Aims: (1) To evaluate the role of mTOR complex 2 (RICTOR) in human hepatocarcinogenesis and (2) to assess the impact of selective RICTOR blockade in cellular models of HCC. Methods: DNA copy number changes (Affymetrix 238K Sty-arrays) and mRNA levels of RICTOR (Affymetrix U133 Plus 2.0 arrays and qRTPCR using Taqman Probes) were analyzed in 102 human HCV-related HCC (fresh frozen samples). RICTOR over-expression was correlated with both signaling pathway activation (Wnt-sCatenin, IGF/AKT/MTOR and RAS/MAPK), and with the existing molecular classification of HCC (Chiang et al. Cancer Res 2008). Data were validated in a separate cohort of 164 HCC patients (paraffin-embedded samples), profiled using DASL (Illumina). Molecular data were correlated with clinico-pathological features and patient prognosis using Kaplan-Meier and Cox Proportional Hazard Test. For in vitro studies, Huh-7 cells were transfected with siRNA-RICTOR, and western blots done to evaluate downstream signals (p-AKT, p-RPS6 and p-ERK). Cell viability and proliferation were assessed by MTT and [H3]-Thymidine incorporation assay respectively, whereas FACS was used to evaluate cell cycle. Results: 25% (25/100) of HCV-related HCC samples had DNA gains in the RICTOR locus. Among them, 12% (11/87) had high mRNA levels of RICTOR (P=0.03). These patients had significantly worse survival (P=0.001) and higher rates of early recurrence (P Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 444.