RESUMO
Cancer cells display metabolic plasticity to survive stresses in the tumor microenvironment. Cellular adaptation to energetic stress is coordinated in part by signaling through the liver kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) pathway. Here, we demonstrate that miRNA-mediated silencing of LKB1 confers sensitivity of lymphoma cells to mitochondrial inhibition by biguanides. Using both classic (phenformin) and newly developed (IM156) biguanides, we demonstrate that elevated miR-17â¼92 expression in Myc+ lymphoma cells promotes increased apoptosis to biguanide treatment in vitro and in vivo. This effect is driven by the miR-17-dependent silencing of LKB1, which reduces AMPK activation in response to complex I inhibition. Mechanistically, biguanide treatment induces metabolic stress in Myc+ lymphoma cells by inhibiting TCA cycle metabolism and mitochondrial respiration, exposing metabolic vulnerability. Finally, we demonstrate a direct correlation between miR-17â¼92 expression and biguanide sensitivity in human cancer cells. Our results identify miR-17â¼92 expression as a potential biomarker for biguanide sensitivity in malignancies.
Assuntos
Quinases Proteína-Quinases Ativadas por AMP/genética , Biguanidas/uso terapêutico , Linfoma/tratamento farmacológico , RNA Longo não Codificante/fisiologia , Quinases Proteína-Quinases Ativadas por AMP/efeitos dos fármacos , Animais , Antineoplásicos/uso terapêutico , Apoptose/efeitos dos fármacos , Apoptose/genética , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/genética , Sinergismo Farmacológico , Células HEK293 , Humanos , Linfoma/genética , Linfoma/patologia , Camundongos , Camundongos Nus , Proteínas Proto-Oncogênicas c-myc/genética , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
The microRNAs encoded by the miR-17â¼92 polycistron are commonly overexpressed in cancer and orchestrate a wide range of oncogenic functions. Here, we identify a mechanism for miR-17â¼92 oncogenic function through the disruption of endogenous microRNA (miRNA) processing. We show that, upon oncogenic overexpression of the miR-17â¼92 primary transcript (pri-miR-17â¼92), the microprocessor complex remains associated with partially processed intermediates that aberrantly accumulate. These intermediates reflect a series of hierarchical and conserved steps in the early processing of the pri-miR-17â¼92 transcript. Encumbrance of the microprocessor by miR-17â¼92 intermediates leads to the broad but selective downregulation of co-expressed polycistronic miRNAs, including miRNAs derived from tumor-suppressive miR-34b/c and from the Dlk1-Dio3 polycistrons. We propose that the identified steps of polycistronic miR-17â¼92 biogenesis contribute to the oncogenic re-wiring of gene regulation networks. Our results reveal previously unappreciated functional paradigms for polycistronic miRNAs in cancer.
Assuntos
Carcinogênese/genética , MicroRNAs/genética , Processamento Pós-Transcricional do RNA/genética , Proteínas de Ligação ao Cálcio/genética , Regulação Neoplásica da Expressão Gênica/genética , Humanos , Iodeto Peroxidase/genética , Proteínas de Membrana/genética , MicroRNAs/biossíntese , Conformação de Ácido NucleicoRESUMO
A central hallmark of cancer cells is the reprogramming of cellular metabolism to meet the bioenergetic and biosynthetic demands of malignant growth. Here, we report that the miR-17â¼92 microRNA (miRNA) cluster is an oncogenic driver of tumor metabolic reprogramming. Loss of miR-17â¼92 in Myc(+) tumor cells leads to a global decrease in tumor cell metabolism, affecting both glycolytic and mitochondrial metabolism, whereas increased miR-17â¼92 expression is sufficient to drive increased nutrient usage by tumor cells. We mapped the metabolic control element of miR-17â¼92 to the miR-17 seed family, which influences cellular metabolism and mammalian target of rapamycin complex 1 (mTORC1) signaling through negative regulation of the LKB1 tumor suppressor. miR-17-dependent tuning of LKB1 levels regulates both the metabolic potential of Myc(+) lymphomas and tumor growth in vivo. Our results establish metabolic reprogramming as a central function of the oncogenic miR-17â¼92 miRNA cluster that drives the progression of MYC-dependent tumors.
Assuntos
Transformação Celular Neoplásica/metabolismo , Regulação Neoplásica da Expressão Gênica , Linfócitos/metabolismo , Linfoma/metabolismo , MicroRNAs/genética , Quinases Proteína-Quinases Ativadas por AMP , Animais , Sequência de Bases , Linhagem Celular Tumoral , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/patologia , Glicólise/genética , Xenoenxertos , Humanos , Transfusão de Linfócitos , Linfócitos/patologia , Linfoma/genética , Linfoma/patologia , Alvo Mecanístico do Complexo 1 de Rapamicina , Camundongos , MicroRNAs/metabolismo , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismo , Fosforilação Oxidativa , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Proto-Oncogênicas c-myc/genética , Proteínas Proto-Oncogênicas c-myc/metabolismo , RNA Longo não Codificante , Transdução de Sinais , Serina-Treonina Quinases TOR/genética , Serina-Treonina Quinases TOR/metabolismoRESUMO
The canonical Gα subunit of the heterotrimeric G protein complex from wheat (Triticum aestivum), GA3, and the calcium-binding protein, Clo3, were revealed to interact both in vivo and in vitro and Clo3 was shown to enhance the GTPase activity of GA3. Clo3 is a member of the caleosin gene family in wheat with a single EF-hand domain and is induced during cold acclimation. Bimolecular Fluorescent Complementation (BiFC) was used to localize the interaction between Clo3 and GA3 to the plasma membrane (PM). Even though heterotrimeric G-protein signaling and Ca²âº signaling have both been shown to play a role in the response to environmental stresses in plants, little is known about the interaction between calcium-binding proteins and Gα. The GAP activity of Clo3 towards GA3 suggests it may play a role in the inactivation of GA3 as part of the stress response in plants. GA3 was also shown to interact with the phosphoinositide-specific phospholipase C, PI-PLC1, not only in the PM but also in the endoplasmic reticulum (ER). Surprisingly, Clo3 was also shown to interact with PI-PLC1 in the PM and ER. In vitro analysis of the protein-protein interaction showed that the interaction of Clo3 with GA3 and PI-PLC1 is enhanced by high Ca²âº levels. Three-way affinity characterizations with GA3, Clo3 and PI-PLC1 showed the interaction with Clo3 to be competitive, which suggests that Clo3 may play a role in the Ca²âº-triggered feedback regulation of both GA3 and PI-PLC1. This hypothesis was further supported by the demonstration that Clo3 has GAP activity with GA3.
