Project description:Trametinib-treated rhabdomyosarcoma cells undergo transcriptional reprogramming akin to myogenic differentiation. This reprogramming is induced by loss of ERK-mediated inhibition of MYOG expression. Restoration of MYOG allows establishment of super-enhancers at genes expressed by terminally differentiated myotubes. Our findings demonstrate that aberrant MAP kinase activity blocks differentiation in rhabdomyosarcoma and highlight trametinib as a potential therapeutic for RAS-mutated rhabdomyosarcoma.
Project description:Trametinib-treated rhabdomyosarcoma cells undergo transcriptional reprogramming akin to myogenic differentiation. This reprogramming is induced by loss of ERK-mediated inhibition of MYOG expression. Restoration of MYOG allows establishment of super-enhancers at genes expressed by terminally differentiated myotubes. Our findings demonstrate that aberrant MAP kinase activity blocks differentiation in rhabdomyosarcoma and highlight trametinib as a potential therapeutic for RAS-mutated rhabdomyosarcoma.
Project description:Aberrant RAS/MAPK signaling, a common driver of oncogenesis, can be therapeutically targeted with clinically approved MEK inhibitors. Single agent therapy ultimately results in tumor outgrowth in most settings and combination therapies are required to achieve significant clinical benefit in most advanced cancers. Here we focus on identifying MEK inhibitor-based combination therapies in RAS-mutant neuroblastoma. Mutations that activate the RAS/MAPK signaling pathway, while rare at diagnosis, are more frequent in relapsed neuroblastoma. More than 50% of children with high-risk neuroblastoma ultimately relapse and treatment options for relapsed neuroblastoma are limited so most children with relapsed disease do not survive. Here we use a genome-scale CRISPR-Cas9 functional genomic screen to identify genes that, when lost, sensitize RAS-mutant neuroblastoma to MEK inhibition. We discover that loss of either CCNC or CDK8, two members of the mediator kinase module, sensitizes neuroblastoma to MEK inhibition. Furthermore, we demonstrate that small molecule kinase inhibitors of CDK8 improve response to MEK inhibitors in vitro and in vivo in RAS-mutant neuroblastoma and other adult solid tumors, suggesting that the addition of CDK8 inhibitors could improve clinical outcome. Using transcriptional profiling, we unexpectedly find that loss of CDK8 or CCNC antagonizes the transcriptional signature induced by MEK inhibition. When combined, loss of CDK8 or CCNC prevents the compensatory upregulation of pro-growth gene expression induced by MEK inhibition. These findings propose a new therapeutic combination for RAS-mutant neuroblastoma and may have clinical relevance for other RAS-driven malignancies.
Project description:KRAS is the most frequently mutated driver of pancreatic, colorectal, and non-small cell lung cancers. Direct KRAS blockade has proven challenging and inhibition of a key downstream effector pathway, the RAF-MEK-ERK cascade, has shown limited success due to activation of feedback networks that keep the pathway in check. We hypothesized that inhibiting SOS1, a KRAS activator and important feedback node, represents an effective approach to treat KRAS-driven cancers. We report the discovery of a highly potent, selective and orally bioavailable small-molecule SOS1 inhibitor, BI-3406, that binds to the catalytic domain of SOS1 thereby preventing the interaction with KRAS. BI-3406 reduces formation of GTP-loaded RAS and limits cellular proliferation of a broad range of KRAS-driven cancers. Importantly, BI-3406 attenuates feedback reactivation induced by MEK inhibitors and thereby enhances sensitivity of KRAS-dependent cancers to MEK inhibition. Combined SOS1 and MEK inhibition represents a novel and effective therapeutic concept to address KRAS-driven tumors.
Project description:Rhabdomyosarcoma (RMS) is a paediatric cancer driven either by a fusion protein (e.g. PAX3-FOXO1) or by mutations in key signalling molecules (e.g. RAS or FGFR4). Despite the latter giving potential for precision medicine approaches in RMS, there are no such treatments implemented in the clinic yet. In order to identify and test novel precision therapy strategies, appropriate cellular and mouse models are crucial. We have here thoroughly characterized a RMS patient-derived cell line model, RMS559, which harbours a FGFR4 V550L activating mutation with high allelic frequency (0.8). Importantly, we show that RMS559 cells are oncogenically dependent on FGFR4 signalling by treatment with the pan-FGFR inhibitor LY2874455. Phosphoproteomic analysis identified RAS/MAPK and PI3K/AKT as the major druggable signalling pathways downstream of FGFR V550L. Inhibitors against these pathways inhibited cell proliferation. Furthermore, we found that FGFR4 V550L is dependent on HSP90 and inhibitors targeting HSP90 efficiently restrain proliferation. Recently, FGFR4 specific inhibitors have been developed. While two of these, BLU-9931 and H3B-6527, did not efficiently inhibit FGFR4 V550L, probably because of the gatekeeper mutation (V550L), one of them, FGF401 inhibited FGFR4 V550L and cell proliferation at low nanomolar concentrations. Finally, we developed a mouse model using RMS559 cells and tested the in vivo efficacy of LY2874455 and FGF401. While LY2874455 inefficiently inhibited growth, FGF401 completely abrogated tumour growth in vivo.
Project description:Certain oncolytic viruses exploit activated Ras signalling in order to replicate in cancer cells. Constitutive activation of the Ras/MEK pathway is known to suppress the effectiveness of the interferon (IFN) antiviral response, which may contribute to Ras-dependent viral oncolysis. Here, we identified 10 human cancer cell lines (out of 16) with increased sensitivity to the anti-viral effects of IFN-α after treatment with the MEK inhibitor U0126, suggesting that the Ras/MEK pathway underlies their reduced sensitivity to IFN. To determine how Ras/MEK suppresses the IFN response in these cells, we used DNA microarrays to compare IFN-induced transcription in IFN-sensitive SKOV3 cells, moderately resistant HT1080 cells, and HT1080 cells treated with U0126. We found that 267 genes were induced by IFN in SKOV3 cells, while only 98 genes were induced in HT1080 cells at the same time point. Furthermore, the expression of a distinct subset of IFN inducible genes, that included RIGI, GBP2, IFIT2, BTN3A3, MAP2, MMP7 and STAT2, was restored or increased in HT1080 cells when the cells were co-treated with U0126 and IFN. Bioinformatic analysis of the biological processes represented by these genes revealed increased representation of genes involved in the anti-viral response, regulation of apoptosis, cell differentiation and metabolism. Furthermore, introduction of constitutively active Ras into IFN sensitive SKOV3 cells reduced their IFN sensitivity and ability to activate IFN-induced transcription. This work demonstrates for the first time that activated Ras/MEK in human cancer cells induces downregulation of a specific subset of IFN-inducible genes. HT1080 cancer cells treated for 6 hours or 12 hours with interferon-alpha (500U/ml), the MEK inhibitor U0126 (20uM) or both, triplicate biological samples (18 samples). SKOV3 cells treated with interferon-alpha (500U/ml) for 6h, triplicate biological samples (6 samples).
Project description:Anticancer drug development is an inefficient process, with potential therapeutics demonstrating a high attrition rate due to lack of efficacy in Phase II/III testing. In an effort to develop improved pre-clinical predictors of efficacy, we and others have turned to testing in genetically engineered murine models (GEMMs) of cancer, which may offer some advantages to in vitro and xenograft systems. Specifically, we assessed the activity of 16 treatment regimens in a Ras-driven, Ink4a/Arf-deficient melanoma GEMM. Like human RAS-mutant melanoma, this GEMM was refractory to standard chemotherapy and single-agent small molecule therapies. Only one regimen exhibited significant anti-tumor activity in this model: combined treatment with AZD6244 (MEK inhibitor) and BEZ235 (dual PI3K/mTOR inhibitor), which produced marked tumor regression and improved survival. Given the surprising activity of the “AZD/BEZ” combination in a melanoma GEMM, we next tested this regimen in a Ras-driven orthotopic-transplant model of “claudin-low” breast cancer, which shares some gene expression features with melanoma. The AZD/BEZ regimen also exhibited significant activity in this related Ras-driven model, leading us to testing in even more diverse GEMMs of basal-like and luminal breast cancer. The AZD/BEZ combination was highly active in each of these distinct breast models, demonstrating equal or greater efficacy compared to any other regimen tested in studies of over 700 tumor-bearing mice. This regimen even exhibited activity in tumors selected for resistance to another effective chemotherapy agent, lapatinib, in HER2+ models. These results demonstrate the utility of credentialed murine models for large-scale efficacy testing of diverse anti-cancer regimens, and predict combinations of PI3K/mTOR and MEK inhibitors will demonstrate anti-tumor activity in a wide-range of human malignancies. 16 array samples