Gastroenterology

Gastroenterology

Volume 135, Issue 6, December 2008, Pages 1972-1983.e11
Gastroenterology

Clinical—Liver, Pancreas, and Biliary Tract
Pivotal Role of mTOR Signaling in Hepatocellular Carcinoma

https://doi.org/10.1053/j.gastro.2008.08.008Get rights and content

Background & Aims

The advent of targeted therapies in hepatocellular carcinoma (HCC) has underscored the importance of pathway characterization to identify novel molecular targets for treatment. We evaluated mTOR signaling in human HCC, as well as the antitumoral effect of a dual-level blockade of the mTOR pathway.

Methods

The mTOR pathway was assessed using integrated data from mutation analysis (direct sequencing), DNA copy number changes (SNP-array), messenger RNA levels (quantitative reverse-transcription polymerase chain reaction and gene expression microarray), and protein activation (immunostaining) in 351 human samples [HCC (n = 314) and nontumoral tissue (n = 37)]. Effects of dual blockade of mTOR signaling using a rapamycin analogue (everolimus) and an epidermal/vascular endothelial growth factor receptor inhibitor (AEE788) were evaluated in liver cancer cell lines and in a xenograft model.

Results

Aberrant mTOR signaling (p-RPS6) was present in half of the cases, associated with insulin-like growth factor pathway activation, epidermal growth factor up-regulation, and PTEN dysregulation. PTEN and PI3KCA-B mutations were rare events. Chromosomal gains in RICTOR (25% of patients) and positive p-RPS6 staining correlated with recurrence. RICTOR-specific siRNA down-regulation reduced tumor cell viability in vitro. Blockage of mTOR signaling with everolimus in vitro and in a xenograft model decelerated tumor growth and increased survival. This effect was enhanced in vivo after epidermal growth factor blockade.

Conclusions

MTOR signaling has a critical role in the pathogenesis of HCC, with evidence for the role of RICTOR in hepato-oncogenesis. MTOR blockade with everolimus is effective in vivo. These findings establish a rationale for targeting the mTOR pathway in clinical trials in HCC.

Section snippets

Human Tissue Samples

A total of 351 human liver samples obtained either from liver resection or transplantation were analyzed in different sets (Figure 1). All of the samples were obtained from the HCC Genomic Consortium: Mount Sinai School of Medicine in New York (United States), Hospital Clinic in Barcelona (Spain), and Istituto Nazionale dei Tumori in Milan (Italy). After institutional review board approval and after patient written informed consent was obtained, tissue specimens were collected. First, we used

mTOR pathway gene expression alterations, DNA copy number changes, and mutation analysis of HCV-related HCC

We conducted an expression study using quantitative reverse-transcription PCR in 2 different human cohorts: exploratory (n = 77) and replication (n = 78) sets (Figure 2 and Supplementary Figure 1; see Supplementary material online at www.gastrojournal.org). Dysregulation of key growth regulatory genes including EGF, IGFBP3, and PTEN was evident in overt HCC. EGF was up-regulated, particularly in advanced HCC cases (P = .001), and the tumor suppressor IGFBP3 was down-regulated in early and

Discussion

Recent studies have identified PI3K/AKT/mTOR pathway as a major oncogenic cascade for targeting molecular therapies in cancer.25 MTOR signaling has been implicated in the initiation and progression of multiple tumors, such as leiomyosarcomas and gliomas.26 We show herein that mTOR pathway is activated in a subset of patients with early HCC. Activation of mTOR cascade resulted from ligand-dependent signals from EGF and IGF signaling, rather than from a mutation-dependent mechanism, because no

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    The authors would like to honor the memory of their colleague and friend, Eric R. Lemmer, member of the Mount Sinai Liver Cancer Program and the Division of Liver Diseases. The authors also want to thank Dr Ron Prywes (Columbia University, NY) for providing the c-fos luciferase reporter. The authors thank Novartis Pharma for providing the drugs (AEE788 and RAD001 in the context of an MTA) used in this study.

    The authors disclose the following: Supported by a grant from Fundación Pedro Barrié de la Maza, Asociación Española para el Estudio del Hígado, National Cancer Center, and an European Association for the Study of the Liver-Sheila Sherlock Fellowship (A.V.); by a grant from Instituto de Salud Carlos III (FIS-CM04/00044 to B.M.); by the Italian Association for Cancer Research and the Italian National Ministry of Health (V.M.); by a grant from Instituto Carlos III (ISCIII/FIS PI 05-0150 to J.B.); by Institució Catalana de Recerca i Estudis Avançats and grants from the U.S. National Institute of Diabetes and Digestive and Kidney Diseases (1R01DK076986-01), the Samuel Waxman Cancer Research Foundation, and the Spanish National Health Institute (SAF-2007-61898) (J.L.); and by grants from the National Institutes of Health (1RO1DK37340-23 to S.F.). Philippa Newell is a recipient of an American Liver Foundation Fellowship and Yujin Hoshida is a recipient of a Charlie A. King Trust fellowship. M. Meyerson is a consultant for Novartis.

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