RESUMO
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.
Assuntos
Adenocarcinoma/metabolismo , Fator de Iniciação 4A em Eucariotos/metabolismo , Neoplasias Pancreáticas/metabolismo , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , RNA Mensageiro/metabolismo , Ribossomos/metabolismo , Regiões 5' não Traduzidas , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Adenocarcinoma/tratamento farmacológico , Animais , Linhagem Celular Tumoral , Cicloeximida/farmacologia , Fator de Iniciação 4A em Eucariotos/antagonistas & inibidores , Quadruplex G , Genes ras/genética , Humanos , Camundongos , Camundongos Nus , Mutação , Transplante de Neoplasias , Oxirredução , Neoplasias Pancreáticas/tratamento farmacológico , Fosfatidilinositol 3-Quinases/genética , Fosfatidilinositol 3-Quinases/metabolismo , Polirribossomos/metabolismo , Biossíntese de Proteínas , Inibidores da Síntese de Proteínas/farmacologia , Proteínas Proto-Oncogênicas c-met/genética , Proteínas Proto-Oncogênicas c-met/metabolismo , Proteínas Proto-Oncogênicas c-myc/genética , Proteínas Proto-Oncogênicas c-myc/metabolismo , RNA Helicases , Análise de Sequência de RNA , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcriptoma , Triterpenos/farmacologia , Proteínas de Sinalização YAP , Proteínas rac de Ligação ao GTP/genética , Proteínas rac de Ligação ao GTP/metabolismo , Proteínas ral de Ligação ao GTP/genética , Proteínas ral de Ligação ao GTP/metabolismo , Proteína RAC2 de Ligação ao GTPRESUMO
The oncogenic c-MYC (MYC) transcription factor has broad effects on gene expression and cell behavior. We show that MYC alters the efficiency and quality of mRNA translation into functional proteins. Specifically, MYC drives the translation of most protein components of the electron transport chain in lymphoma cells, and many of these effects are independent from proliferation. Specific interactions of MYC-sensitive RNA-binding proteins (e.g., SRSF1/RBM42) with 5'UTR sequence motifs mediate many of these changes. Moreover, we observe a striking shift in translation initiation site usage. For example, in low-MYC conditions, lymphoma cells initiate translation of the CD19 mRNA from a site in exon 5. This results in the truncation of all extracellular CD19 domains and facilitates escape from CD19-directed CAR-T cell therapy. Together, our findings reveal MYC effects on the translation of key metabolic enzymes and immune receptors in lymphoma cells.
