Adaptive responses to mTOR targeting sustain hematopoietic and leukemia stem cell proliferation II
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ABSTRACT:
PROVIDER: PRJNA554691 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR9689867.fastq.gz | Fastqsanger.gz | |||
| SRR9689868.fastq.gz | Fastqsanger.gz | |||
| SRR9689869.fastq.gz | Fastqsanger.gz |
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Project description:mTOR is an important anti-cancer target that integrates diverse signals to control protein synthesis and cell growth. Numerous studies by using mTOR inhibitors and/or gene deletion of mTOR negative regulators have implicated mTOR targeting in suppressing gene expression and cell proliferation. However, we found that gene targeting of mTOR in mouse hematopoietic stem cells (HSCs) results in a loss of quiescence and increased proliferation. Adaptive to mTOR loss, mTOR-/- HSCs increase chromatin access and activate global gene expression, in contrast to short-term inhibition by mTOR inhibitors. Such genomic changes are due to a compensatory activation of a MAPK/Mnk/eIF4E signaling pathway that enhances the translation of RNA pol-II and consequent c-myc expression. This adaptive mechanism can also be adopted by leukemia stem cells undergone long-term mTOR inhibitor treatment to confer resistant to mTOR targeting. Our studies provide new insights and a foregone strategy for overcoming drug resistance in mTOR targeted therapy.
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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.
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Project description:Adaptive responses to mTOR gene targeting in hematopoietic stem cells reveal a proliferative mechanism evasive to mTOR inhibition
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Project description:The mTOR (mammalian Target of Rapamycin) pathway is constitutively activated in Diffuse Large B-Cell Lymphoma (DLBCL). mTOR inhibition has been shown to have clinical activity in patients with DLBCL, although overall response rates remain low. We therefore evaluated differences in the transcriptome between DLBCL cell lines with differential sensitivity to the mTOR inhibitor Rapamycin, to (A) identify gene-expression patterns(GEP) capable of identifying sensitivity to Rapamycin, (B) understand the underlying mechanisms of resistance to Rapamycin in DLBCL and (C) identify bioactive molecules likely to synergize with mTOR inhibitors. Using Affymetrix HuGene ST 1.0 microarrays, we were able to identify a gene expression signature capable of accurately predicting sensitivity and resistance to Rapamycin in DLBCL cell lines. Pathway analysis identified the serine/threonine kinase Akt as central to the differentially-expressed gene network. Connectivity mapping of our datasets identified compounds targeting the AKT pathway with a high likelihood of reversing the GEP associated with resistance to Rapamycin. Specifically, we evaluated the HIV protease inhibitor (PI) Nelfinavir, which is known to have anti-cancer and Akt-inhibitory properties, as well as the small molecule Akt inhibitor MK-2206, for their potential to synergize with to Rapamycin in DLBCL. Nelfinavir and MK-2206 caused profound inhibition of cell viability in combination with Rapamycin in DLBCL cell lines. Low nanomolar concentrations of Rapamycin inhibited phosphorylation of Akt and also downstream targets of activated mTOR when used in combination with these Akt inhibitors. These findings have the potential to significantly improve patient selection for mTOR inhibitor therapy, and to improve rates and depths of response. More broadly, they support the use of global RNA expression and connectivity mapping to improve patient selection and identify synergistic drug combinations for cancer therapy. DLBCL cell lines were tested for Rapamycin sensitivity and classified as "sensitive" or "resistant." Genome-wide analysis of all cell lines were performed using the Affymetrix HuGene ST 1.0 Array Platform. Genes with differential expression between sensitive and resistant cell lines were analyzed using Statistical Analysis of Microarrays (SAM) software, and a signature of genes determnined. This signature was found to accurately predict sensitivity or resistance of other DLBCL cell lines, and to identify the protein kinase Akt as central to resistance.
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Project description:The mechanistic target of rapamycin (mTOR) is a central regulator of cell growth and an attractive anticancer 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 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, which in turn leads to increased c-Myc gene expression, allowing the HSCs to thrive despite the 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 be counteracted by MNK, CDK9, or c-Myc inhibition. These results provide insights into the physiological role of mTOR in mammalian stem cell regulation and implicate a mechanism of evasive resistance in the context of mTOR targeting.
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Project description:Therapeutic targeting of BRAFV600E has shown a significant impact on progression-free and overall survival in advanced melanoma, but only a fraction of patients benefit from these treatments, suggesting that additional signaling pathways involved in melanoma growth/survival need to be identified. In fact MAPK and PI3K/mTOR signaling pathways are constituively activated in most cancers, including melanoma, to sustain the melanoma growth/survival. A large panel of melanoma were characterized for resistance/susceptibility to different inhibitors targeting MAPK and PI3K/mTOR signaling pathways and the synergistic effect of combinatorial treatments affecting both pathways. These effects were evaluated in terms of cell viability (MTT), apoptosis (Annexin V-PI), caspase 3/7 activity and subG1 cell fraction, highlighting a hierarchy in the combination effects. Further, a smaller panel of melanoma cell lines, were treated with inhibitors singularly and in combination to test the effects on the expression of principal proteins involved in these two pathways. Gene expression profile was performed to analyse the gene modulation induced by inhibitors to identify new strategies to fight melanoma resistance.
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Project description:Analysis of the effects of a dual specificity PI3K/mTOR inhibitor on two human ovarian cell lines, OV2008 and MCAS. Results provide insight into the adaptive response to PI3K/mTOR inhibition in matrix attached ovarian cancer cells. The PI3K/mTOR-pathway is the most commonly deregulated pathway in epithelial cancers and thus represents an important target for cancer therapeutics. Here we show that dual inhibition of PI3K/mTOR in ovarian cancer 3D-spheroids leads to death of the inner matrix-deprived cells, whereas matrix-attached cells are resistant. Resistance is associated with up-regulation of a cellular survival program that involves both FOXO-regulated transcription and a novel translational resistance mechanism resulting in specific up-regulation of IRES-mediated, cap-independent translation. Inhibition of any of several up-regulated proteins, including Bcl-2, EGFR, or IGF1R, abrogates resistance to dual PI3K/mTOR inhibition. These results demonstrate that acute adaptive response to PI3K/mTOR inhibition resembles well-conserved adaptive response to nutrient and growth factor deprivation and how development of rational drug combinations can bypass resistance mechanisms. Total RNA was isolated 6h and 24h after treatment with 1 M-NM-<M NVP-BEZ235 or DMSO vehicle control from 3D grown structures
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Project description:Tuberous sclerosis complex (TSC) is a rare genetic disease caused by abnormal of TSC1 or TSC2 gene. Our previous data deduced that IQGAP2 can be one of the genes potentially responsible for non-TSC1 or TSC2 mutation TSC patients. To investigate the pathogenesis of IQGAP2 in TSC, we performed global transcriptome, proteome, and phosphoproteome analyses and found the alter of genes related to mTOR signaling pathway in IQGAP2 knockdown cells. In addition, we found that knockdown of IQGAP2 resulted in increased cell proliferation and enhanced the phosphorylation level of AKT and S6K by functional analysis, meanwhile, the AKT and mTOR inhibitors can partially rescue cell abnormal proliferation by decreasing hyperphosphorylation. Our data revealed a potential connection between mTOR signaling pathway and aberrant cell proliferation in IQGAP2 knockdown cells, and provide a new latent therapeutic strategy for non-TSC1 or TSC2 mutation patients.
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