silvestrol and Adenocarcinoma

Pancreatic adenocarcinoma (PDAC) epitomizes a deadly cancer driven by abnormal KRAS signaling. Here, we show that the eIF4A RNA helicase is required for translation of key KRAS signaling molecules and that pharmacological inhibition of eIF4A has single-agent activity against murine and human PDAC models at safe dose levels. EIF4A was uniquely required for the translation of mRNAs with long and highly structured 5' untranslated regions, including those with multiple G-quadruplex elements. Computational analyses identified these features in mRNAs encoding KRAS and key downstream molecules. Transcriptome-scale ribosome footprinting accurately identified eIF4A-dependent mRNAs in PDAC, including critical KRAS signaling molecules such as PI3K, RALA, RAC2, MET, MYC, and YAP1. These findings contrast with a recent study that relied on an older method, polysome fractionation, and implicated redox-related genes as eIF4A clients. Together, our findings highlight the power of ribosome footprinting in conjunction with deep RNA sequencing in accurately decoding translational control mechanisms and define the therapeutic mechanism of eIF4A inhibitors in PDAC. SIGNIFICANCE: These findings document the coordinate, eIF4A-dependent translation of RAS-related oncogenic signaling molecules and demonstrate therapeutic efficacy of eIF4A blockade in pancreatic adenocarcinoma.

Topics: 5' Untranslated Regions; Adaptor Proteins, Signal Transducing; Adenocarcinoma; Animals; Cell Line, Tumor; Cycloheximide; Eukaryotic Initiation Factor-4A; G-Quadruplexes; Genes, ras; Humans; Mice; Mice, Nude; Mutation; Neoplasm Transplantation; Oxidation-Reduction; Pancreatic Neoplasms; Phosphatidylinositol 3-Kinases; Polyribosomes; Protein Biosynthesis; Protein Synthesis Inhibitors; Proto-Oncogene Proteins c-met; Proto-Oncogene Proteins c-myc; Proto-Oncogene Proteins p21(ras); rac GTP-Binding Proteins; RAC2 GTP-Binding Protein; ral GTP-Binding Proteins; Ribosomes; RNA Helicases; RNA, Messenger; Sequence Analysis, RNA; Transcription Factors; Transcriptome; Triterpenes; YAP-Signaling Proteins