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Hyperactive mTOR and MNK1 phosphorylation of eIF4E confer tamoxifen resistance and estrogen independence through selective mRNA translation reprogramming

ABSTRACT: Tamoxifen resistant translational reprogramming is shown to be mediated by increased expression of eIF4E and its increased availability by hyperactive mTOR, and to require phosphorylation of eIF4E at Ser209 by increased MNK activity.

ORGANISM(S): Homo sapiens

PROVIDER: GSE107590 | GEO | 2017/12/21

SECONDARY ACCESSION(S): PRJNA420692

REPOSITORIES: GEO

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Hyperactive mTOR and MNK1 phosphorylation of eIF4E confer tamoxifen resistance and estrogen independence through selective mRNA translation reprogramming.

Project description:The majority of breast cancers expresses the estrogen receptor (ER+) and is treated with anti-estrogen therapies, particularly tamoxifen in premenopausal women. However, tamoxifen resistance is responsible for a large proportion of breast cancer deaths. Using small molecule inhibitors, phospho-mimetic proteins, tamoxifen-sensitive and tamoxifen-resistant breast cancer cells, a tamoxifen-resistant patient-derived xenograft model, patient tumor tissues, and genome-wide transcription and translation studies, we show that tamoxifen resistance involves selective mRNA translational reprogramming to an anti-estrogen state by Runx2 and other mRNAs. Tamoxifen-resistant translational reprogramming is shown to be mediated by increased expression of eIF4E and its increased availability by hyperactive mTOR and to require phosphorylation of eIF4E at Ser209 by increased MNK activity. Resensitization to tamoxifen is restored only by reducing eIF4E expression or mTOR activity and also blocking MNK1 phosphorylation of eIF4E. mRNAs specifically translationally up-regulated with tamoxifen resistance include Runx2, which inhibits ER signaling and estrogen responses and promotes breast cancer metastasis. Silencing Runx2 significantly restores tamoxifen sensitivity. Tamoxifen-resistant but not tamoxifen-sensitive patient ER+ breast cancer specimens also demonstrate strongly increased MNK phosphorylation of eIF4E. eIF4E levels, availability, and phosphorylation therefore promote tamoxifen resistance in ER+ breast cancer through selective mRNA translational reprogramming.

| S-EPMC5769768 | biostudies-literature

Hyperactive mTOR and MNK1 phosphorylation of eIF4E confer tamoxifen resistance and estrogen independence through selective mRNA translation reprogramming

Project description:Hyperactive mTOR and MNK1 phosphorylation of eIF4E confer tamoxifen resistance and estrogen independence through selective mRNA translation reprogramming

| PRJNA420692 | ENA

eIF4E phosphorylation promotes tumorigenesis and is associated with prostate cancer progression

Project description:Translational regulation plays a critical role in cell growth and proliferation, and its dysregulation results in cancer. Aberrant expression of the mRNA 5’cap-binding protein, eIF4E, has been implicated in cancer development and progression. eIF4E activity is promoted by phosphorylation. Here we show that “knock-in” mice in which eIF4E cannot be phosphorylated are resistant to tumorigenesis in a prostate cancer model. We identify multiple candidate genes involved in the resistance to oncogenic transformation. Importantly, phosphorylation of eIF4E is increased in hormone-refractory prostate cancer, the deadliest stage of the disease. Our results highlight eIF4E phosphorylation as a critical event in tumorigenesis. Comaparison of total RNA and polysomal RNA from mouse embryo fibroblasts derived from WT and eIF4E-KI (non phosphorylatable eIF4E) mice

2010-08-17 | E-GEOD-17451 | biostudies-arrayexpress

Adaptive responses to mTOR gene targeting in hematopoietic stem cells reveal a proliferative mechanism evasive to mTOR inhibition

Project description:The mechanistic target of rapamycin (mTOR) is a central regulator of cell growth and an attractive anti-cancer target that integrates diverse signals to control cell proliferation. Previous studies using mTOR inhibitors have shown that mTOR targeting suppresses gene expression and cell proliferation. To date, however, mTOR targeted therapies in cancer have seen very limited efficacy, and one key issue is related to the development of evasive resistance. In this manuscript, through the use of a gene targeting mouse model, we have found that inducible deletion of mTOR in hematopoietic stem cells (HSCs) results in a loss of quiescence and increased proliferation. Adaptive to the mTOR loss, mTOR-/- HSCs increase chromatin accessibility and activate global gene expression, contrary to the effects of short-term inhibition by mTOR inhibitors. Mechanistically, such genomic changes are due to a rewiring and adaptive activation of the ERK/MNK/eIF4E signaling pathway that enhances the protein translation of RNA polymerase II (RNAP II), which in turn leads to increased c-Myc gene expression, allowing the HSCs to thrive despite loss of a functional mTOR pathway. This adaptive mechanism can also be utilized by leukemia cells undergoing long-term mTOR inhibitor treatment to confer resistance to mTOR drug targeting. The resistance can then be counteracted by MNK, CDK9, or c-Myc inhibition. These results provide new insights into the physiological role of mTOR in mammalian stem cell regulation and implicate a novel mechanism of evasive resistance in the context of mTOR targeting.

2020-12-24 | GSE134316 | GEO

eIF4E phosphorylation promotes tumorigenesis and is associated with prostate cancer progression

2010-08-17 | GSE17451 | GEO

Attenuation of EIF4E Translation Initiation Adversely Affects Multiple Myeloma Cells

2011-03-11 | GSE27897 | GEO

Discovery of a novel plant eIF4E-binding protein: Conserved Binding of eIF4E 1 (CBE1)

Project description:Regulation of translation initiation is accomplished in diverse eukaryotes through proteins which bind to the mRNA cap-binding protein, eIF4E, and either prevent its association with eIF4G or form repressive mRNPs which exclude the translation machinery. Such mechanisms in plants, and even the presence of eIF4E-interacting proteins outside of eIF4G (and the plant-specific isoform eIFiso4G, which binds eIFiso4E) which operate in a gene regulatory manner are not known. Here we describe the Conserved Binding of eIF4E 1 (CBE1), a plant-specific protein with an evolutionarily conserved eIF4E binding motif. This protein binds eIF4E or eIFiso4E in vitro to form cap-binding complexes, and is found as a constituent of cap-binding complexes in vivo in an eIF4E-dependent manner. Mutants lacking CBE1 show dysregulation of cell cycle related transcripts, accumulating higher levels relative to wild-type plants of mRNAs encoding proteins involved in mitotic processes. These findings support CBE1 as a plant protein with the capability to form cap-binding complexes with the potential for gene regulatory activity.

2018-09-26 | GSE114363 | GEO

Attenuation of EIF4E Translation Initiation Adversely Affects Multiple Myeloma Cells

Project description:This work explores the therapeutic potential for the translation initiation factor eIF4E in multiple myeloma (MM). We show that targeting eIF4E is deleterious to MM cells and causes reduction of targets with established importance to the disease progression. We demonstrate that eIF4E inhibition may be achieved by treating the MM cells with the already clinically employed anti-viral drug Ribavirin. Results indicate that tetraspanin overexpression in MM cell lines increased global protein synthesis; CD81N1/CD82N1 also caused a decrease in peIF4E, its regulators and targets; direct inhibition of eIF4E (siRNA, Ribavirin) deleteriously affected MM cell lines; and Ribavirin attenuated viability and induced death of primary BM MM cells. Multiple Myeloma cell lines RPMI 8226 and CAG were each transiently transfected with purified plasmids of tetraspanins: pEGFP-N1 (N1, control), CD81N1-eGFP (81N1) or CD82N1-eGFP (82N1) (Clontech). Transfected cells were separated by Sorter Flow Cytometer 24 hours after transfection. Total RNA was extracted from sorted transfected cells with the Qiagen kit. Three separate experiments were analyzed by Whole Genome Affymetrix microarray chips (N1, 81N1, 82N1 in each cell line).

2011-03-11 | E-GEOD-27897 | biostudies-arrayexpress

MDA-MB-231 eIF4E RIP-CHIP

Project description:Cytoplasmic RNA bound to eIF4E was pulled down from MDA-MB-231 cells to determine the influence of radiation on eIF4E mRNA binding 4 samples were analyzed with 3 biological replicates

2012-06-14 | E-GEOD-36179 | biostudies-arrayexpress

MDA-MB-231 eIF4E RIP-CHIP

Project description:Cytoplasmic RNA bound to eIF4E was pulled down from MDA-MB-231 cells to determine the influence of radiation on eIF4E mRNA binding

2012-06-15 | GSE36179 | GEO

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