Comparative analysis of RAF depletion vs. MAPK inhibition
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ABSTRACT:
PROVIDER: EGAS00001005743 | EGA |
REPOSITORIES: EGA
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Project description:KRAS, mutated in ~30% of all cancers, activates the RAF-MEK-ERK signaling cascade. It has previously been shown that CRAF is required for growth of KRAS mutant lung tumors but the requirement for CRAF kinase activity is unknown. Here, we show that subsets of KRAS mutant tumors are dependent on CRAF for growth. Kinase-dead but not dimer-defective CRAF rescued growth inhibition suggesting that dimerization but not kinase activity is required. Quantitative proteomics demonstrated enrichment of CRAF:ARAF dimers in KRAS mutant cells and depletion of both CRAF and ARAF rescued the CRAF loss phenotype. Mechanistically, CRAF depletion caused sustained ERK activation and induction of cell cycle arrest. Treatment with low dose MEK or ERK inhibitor rescued the CRAF loss phenotype. Our studies highlight the role of CRAF in regulating MAPK signal intensity to promote tumorigenesis downstream of mutant KRAS and suggest that disrupting dimerization or degrading CRAF may have therapeutic benefit.
2021-10-29 | MSV000088285 | MassIVE
Project description:Oncogenic KRAS drives cancer growth by activating diverse signaling networks, not all of which have been fully delineated. We set out to establish a system-wide profile of the KRAS-regulated kinase signaling network (kinome) in KRAS-mutant pancreatic ductal adenocarcinoma (PDAC). We knocked down KRAS expression in a panel of six cell lines, and then applied Multiplexed Inhibitor Bead/Mass Spectrometry (MIB/MS) chemical proteomics to monitor changes in kinase activity and/or expression. We hypothesized that depletion of KRAS would result in downregulation of kinases required for KRAS-mediated transforming activities, and in upregulation of other kinases that could potentially compensate for the deleterious consequences of the loss of KRAS. We identified 15 upregulated and 13 downregulated kinases in common across the panel. In agreement with our hypothesis, all 15 of the upregulated kinases have established roles as cancer drivers (e.g., SRC, TGFBR1, ILK), and pharmacologic inhibition of the upregulated kinase, DDR1, suppressed PDAC growth. Interestingly, 11 of the 13 downregulated kinases have established driver roles in cell cycle progression, particularly in mitosis (e.g., WEE1, Aurora A, PLK1). Consistent with a crucial role for the downregulated kinases in promoting KRAS-driven proliferation, we found that pharmacologic inhibition of WEE1 also suppressed PDAC growth. The unexpected paradoxical activation of ERK upon WEE1 inhibition led us to inhibit both WEE1 and ERK concurrently, which caused further potent growth suppression and enhanced apoptotic death than WEE1 inhibition alone. We conclude that system-wide delineation of the KRAS-regulated kinome can identify potential therapeutic targets for KRAS-mutant pancreatic cancer.
2022-02-17 | PXD025819 | Pride
Project description:Mutations activating the KRAS GTPase or the BRAF kinase are frequent in colorectal cancer and are thought to constitutively activate the terminal mitogen-activated protein kinase, ERK. Using mass cytometry, we found graded phosphorylation of ERK anti-correlated with cell differentiation in patient-derived colorectal cancer organoids, and unexpectedly this gradient was observed independently of KRAS mutational status. We therefore investigated differentiation-dependent signal transduction elicited by oncogenic KRAS or BRAF in transgenic mouse organoid models. Reporter, single cell transcriptome and mass cytometry analyses showed that transgenic expression of KRASG12V activated ERK in a cell type-specific pattern. Furthermore, expression of oncogenic KRAS induced the formation of RAS-ERK-responsive cells. In contrast, transgenic expression of BRAFV600E triggered high ERK activity and downstream gene expression in all intestinal cell types, followed by epithelial disorganisation. We analysed signal transduction to ERK using single cell-resolved network perturbation data in transgenic organoids. Network reconstruction followed by quantitative modelling revealed that activation of ERK is shaped by cell type-specific MEK to ERK feed forward and negative feedback signalling. We identify dual-specificity phosphatases as candidate modulators of MEK to ERK signal transduction. Our experiments highlight key differences between ERK activity elicited by the BRAF or KRAS oncogenes in colorectal cancer and find unexpected functional heterogeneity in a signalling pathway with fundamental relevance for cancer therapy.
2019-03-31 | GSE115242 | GEO
Project description:The oncogenic proteins expressed in human cancer cells are exceedingly difficult targets for drug discovery due to intrinsic properties of the Ras GTPase switch. As a result, recent efforts have largely focused on inhibiting Ras-regulated kinase effector cascades, particularly the Raf/MEK/ERK and PI3 kinase/Akt/mTOR pathways. We constructed murine stem cell leukemia virus (MSCV) vectors encoding oncogenic K-RasD12 with additional “second site” amino acid substitutions that that impair PI3 kinase/Akt or Raf/MEK/ERK activation and performed bone marrow transduction/transplantation experiments in mice. In spite of attenuated signaling properties, defective K-Ras oncoproteins induced aggressive clonal T lineage acute lymphoblastic leukemia (T-ALL). These leukemias exhibited a high frequency of somatic Notch1 mutations, which is also true of human T-ALL. Multiple independent T-ALLs restored full oncogenic Ras activity by acquiring “third site” mutations within the viral KrasD12 transgenes. Other leukemias with undetectable PTEN and elevated phosphoryated Akt levels showed a similar gene expression profile to human early T progenitor (ETP) T-ALL. Expressing oncoproteins that are defective for specific functions is a general strategy for assessing requirements for tumor maintenance and uncovering potential mechanisms of drug resistance in vivo. In addition, our observation that defective Kras oncogenes regain potent cancer initiating activity strongly supports simultaneously targeting distinct components of Ras signaling networks in the substantial fraction of cancers with RAS mutations. WT Balb/c mice were lethally irradiated and transplanted with WT Balb/c bone marrow cells transduced with MSCV-IRES-Kras mutant-GFP vectors. Mice developed T-cell lymphoproliferative disease.
2011-09-30 | E-GEOD-28687 | biostudies-arrayexpress
Project description:Objective Oncogenic Kras-activated robust Mek/Erk signals phosphorylate to the tuberous sclerosis complex (Tsc) and deactivates mammalian target of rapamycin (mTOR) suppression in pancreatic ductal adenocarcinoma (PDAC); however, Mek and mTOR inhibitors alone have demonstrated minimal clinical antitumor activity. Design We generated transgenic mouse models in which mTOR was hyperactivated either through the Kras/Mek/Erk cascade, by loss of Pten or through Tsc1 haploinsufficiency. Primary cancer cells were isolated from mouse tumours. Oncogenic signalling was assessed in vitro and in vivo, with and without single or multiple targeted molecule inhibition. Transcriptional profiling was used to identify biomarkers predictive of the underlying pathway alterations and of therapeutic response. Results from the preclinical models were confirmed on human material. Results Reduction of Tsc1 function facilitated activation of Kras/Mek/Erk-mediated mTOR signalling, which promoted the development of metastatic PDACs. Single inhibition of mTOR or Mek elicited strong feedback activation of Erk or Akt, respectively. Only dual inhibition of Mek and PI3K reduced mTOR activity and effectively induced cancer cell apoptosis. Analysis of downstream targets demonstrated that oncogenic activity of the Mek/Erk/Tsc/mTOR axis relied on Aldh1a3 function. Moreover, in clinical PDAC samples, ALDH1A3 specifically labelled an aggressive subtype. Conclusions These results advance our understanding of Mek/Erk-driven mTOR activation and its downstream targets in PDAC, and provide a mechanistic rationale for effective therapeutic matching for Aldh1a3-positive PDACs.
2015-10-05 | GSE48643 | GEO
Project description:Since gastric cancer (GC) is characterized by amplifications of receptor tyrosine kinases (RTK) and KRAS, targeting the RTK/KRAS downstream pathways could contribute to broader applicability of molecular targeted therapy in GC. Here, we assembled a panel of 49 GC cell lines and screened predictors for responsiveness to RAF/MEK/ERK pathway inhibition by comparing their sensitivity to MEK inhibition with alteration status of RTK/KRAS and phosphorylation status of RTK/KRAS downstream molecules. We found that GC cells with MET amplification or KRAS mutation tend to be sensitive to MEK inhibition. Furthermore, lower phosphorylation levels of mTORC1 targets, p70S6K and 4EBP1, was also significantly associated with sensitivity to MEK inhibition. Interestingly, the sensitive cells showed reduced mTORC1 activity accompanied by decreased rate of protein synthesis after MEK inhibition, suggesting that antiproliferative effect of MEK inhibition may be exerted through inhibition of protein synthesis, which was caused by reduced mTORC1 activity. Mechanistically, expression of some mTORC1 negative regulators, such as DDIT4, FOXO3, SESN1 and TSC1, were induced by MEK inhibition in highly-sensitive cell lines and knockdown of these negative regulators partially alleviated the suppression of mTORC1 activity and antiproliferative effect of MEK inhibition. Our data suggest that a subset of GCs, which would be distinguishable according to the predictive markers we identified, may be sensitive to MEK inhibition and have implications for the strategy in clinical trial of MEK inhibitors for GC.
2016-12-31 | GSE74842 | GEO
Project description:Though mitogen activated protein kinase kinases (MKK or MEK) 1 and 2 are widely assumed to be functionally redundant some reports indicate they possess distinct biologic activities. To test the hypothesis that MEK1 and MEK2 signaling pathways are interchangeable we used two complementary approaches to determine the necessity and sufficiency of individual MEK1 and MEK2 signaling pathways for human melanoma SK-MEL-28 cell proliferation. To test the necessity we targeted MEK1 and/or MEK2 using specific siRNAs. An effect on proliferation was observed only when both MEK1 and MEK2 were knocked down indicating that neither of the individual MEK isoforms is necessary for SK-MEL-28 cell proliferation. To test the sufficiency we inhibited multiple MEK and MKK signaling pathways in SK-MEL-28 cells with anthrax lethal toxin (LeTx) a MEK/MKK-specific protease and rescued individual MEK signaling pathways by expressing a cleavage-resistant form of MEK (MEKcr). In this fashion ERK activation was retained only in MEK2cr-expressing cells but not in MEK1cr-expressing cells following LeTx treatment. Microarray analysis revealed groups of non-overlapping downstream transcriptional targets of MEK1 and MEK2 and indicated a substantial rescue effect of MEK2cr on proliferation pathways. Furthermore LeTx efficiently inhibited the cell proliferation and anchorage-independent growth of SK-MEL-28 cells expressing MKK1cr but not MEK2cr. These results not only indicate that in this cellular context MEK2 signaling pathway alone is sufficient for ERK activation melanoma cell proliferation and anchorage-independent growth but MEK1 is not but also demonstrate that MEK1 and MEK2 signaling pathways are not redundant and interchangeable for melanoma cell proliferation. We conclude that while MEK2 alone is sufficient for SK-MEL-28 cell proliferation MEK1 can conditionally compensate for loss of MEK2. SK-MEL-28 melanoma cells +/- cleavage resistant MKK1/MKK2
2011-06-24 | E-GEOD-23930 | biostudies-arrayexpress
Project description:There are currently no effective targeted therapies for KRAS mutant cancers. Therapeutic strategies that combine MEK inhibitors with agents that target apoptotic pathways may be a promising therapeutic approach. We investigated combining MEK and MDM2 inhibitors as a potential treatment strategy for KRAS mutant non-small cell lung cancers and colorectal carcinomas that harbor wild-type TP53. The combination of pimasertib (MEK inhibitor) + SAR405838 (MDM2 inhibitor) was synergistic and induced the expression of PUMA and BIM, led to apoptosis and growth inhibition in vitro, and tumor regression in vivo. Acquired resistance to the combination commonly resulted from the acquisition of TP53 mutations, conferring complete resistance to MDM2 inhibition. In contrast, resistant clones exhibited marked variability in sensitivity to MEK inhibition, which significantly impacted sensitivity to subsequent treatment with alternative MEK inhibitor-based combination therapies. These results highlight both the potential promise and limitations of combining MEK and MDM2 inhibitors for treatment of KRAS mutant NSCLC and CRC.
2017-08-01 | GSE99015 | GEO
Project description:In the present work we propose a new therapy for NRAS mutant melanoma. Simultaneous inhibition of MEK and ROCK caused induction of BimEL , PARP, and Puma, and hence apoptosis. In vivo, MEK and ROCK inhibition suppressed growth of established tumors. Our findings warrant clinical investigation of the effectiveness of combinatorial targeting of MAPK/ERK and ROCK in NRAS mutant melanoma.
2015-03-11 | PXD000528 | Pride
Project description:Hairy cell leukemia (HCL) shows unique clinico-pathological and biological features. HCL responds well to purine analogues but relapses are frequent and novel therapies are required. BRAF-V600E is the key driver mutation in HCL and distinguishes it from other B-cell lymphomas, including HCL-like leukemias/lymphomas (HCL-variant and splenic marginal zone lymphoma). The kinase-activating BRAF-V600E mutation also represents an ideal therapeutic target in HCL. Here, we investigated the biological and therapeutic importance of the activated BRAF-MEK-ERK pathway in HCL by exposing in vitro primary leukemic cells purified from 26 patients to clinically available BRAF (Vemurafenib; Dabrafenib) or MEK (Trametinib) inhibitors. Results were validated in vivo in samples from Vemurafenib-treated HCL patients within a phase-2 clinical trial. BRAF and MEK inhibitors caused, specifically in HCL (but not HCL-like) cells, marked MEK/ERK dephosphorylation, silencing of the BRAF-MEK-ERK pathway transcriptional output, loss of the HCL-specific gene expression signature, downregulation of the HCL markers CD25, TRAP and cyclin-D1, smoothening of leukemic cells' hairy surface, and, eventually, apoptosis. Apoptosis was partially blunted by co-culture with bone marrow stromal cells antagonizing MEK-ERK dephosphorylation. This protective effect could be counteracted by combined BRAF and MEK inhibition. Our results strongly support and inform the clinical use of BRAF and MEK inhibitors in HCL. Analysis of differential gene expression in primary leukemic cells purified from peripheral blood of 6 HCL patients (from A to F), treated with Vemurafenib 1000 nM, in comparison with vehicle-treated (DMSO) HCL cells, for 48 hours or/and 72 hours. 24 gene expression profiles were analysed.
2014-12-12 | E-GEOD-63790 | biostudies-arrayexpress