Global transcriptomic alterations of both coding and non-coding RNA species are a ubiquitous feature associated with human cancers including hepatocellular carcinoma (HCC). Dysregulation of RNA-binding proteins (RBPs), the key regulators of RNA processing, is one mechanism in which cancer cells select to promote tumorigenesis. We analyzed genomic alterations amongst a family of more than 800 mRNA RBPs (mRBPs) in 1,225 clinical specimens from HCC patients and found that RBPs are significantly activated through gene amplification in a subset of tumors with poor prognosis, suggesting their potential oncogenic roles in HCC progression. Amongst the top candidates, RD binding protein (RDBP) was further characterized for its oncogenic role and effects on the HCC transcriptome. While the activation of RDBP induced an oncogenic phenotype, the abrogation of RDBP in HCC cells significantly decreased cancer associated phenotypes such as cell proliferation, migration/invasion and tumorigenicity in vivo. Further analyses revealed that RDBP-dependent genes were tumor-related with a significant enrichment for c-Myc targets, suggesting interplay between RDBP and c-Myc signaling. Similar data were also found in HCC clinical specimens where c-Myc amplification was uncommon. Consistently, the RDBP-dependent c-Myc target gene signature was able to predict HCC patient survival in two independent cohorts of more than 400 patients. Our results demonstrate that oncogenic activation of RDBP is a novel mechanism that contributes to global transcriptome imbalance, which is selective for the activation of c-Myc oncogenic signaling in HCC. Concurrent with the current model that indicates that c-Myc can promote tumorigenesis through transcription dysregulation, our current work suggests that therapies focused on targeting RDBP may be valuable for clinical treatment of many different tumors with activated c-Myc signaling, including HCC.

Citation Format: Dang T. Hien, Atsushi Takai, Marshonna Forgues, Xin Wei Wang. Oncogenic activation of RNA binding proteins and c-Myc signaling 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 1985.