Project description:MAPK scaffolds, such as IQGAP1, assemble pathway kinases together to effect signal transmission and disrupting scaffold function therefore offers a potentially orthogonal approach to MAPK cascade inhibition. Consistent with this possibility, we observed an IQGAP1 requirement in Ras-driven tumorigenesis in mouse and human tissue. Delivery of the IQGAP1 WW peptide sequence that mediates Erk1/4 binding, moreover, disrupted IQGAP1-Erk1/2 interactions, abolished Ras/Raf-driven tumorigenesis, bypassed acquired resistance to the B-Raf inhibitor vemurafinib (PLX- 4032), and acts as a systemically deliverable therapeutic to significantly increase lifespan of tumor bearing mice. Scaffold-kinase interaction blockade (SKIB) acts by a mechanism distinct from direct kinase inhibition and represents a strategy to target over-active oncogenic kinase cascades in cancer. Gene expression profiling: Fragmented cRNA was hybridized to the Mouse Gene 1.0 ST Array (Affymetrix). Iqgap1 wild-type and Iqgap1 knockout mouse treated with topical 4OHT for 0 days and 6 days days are compared.
Project description:MAPK scaffolds, such as IQGAP1, assemble pathway kinases together to effect signal transmission and disrupting scaffold function therefore offers a potentially orthogonal approach to MAPK cascade inhibition. Consistent with this possibility, we observed an IQGAP1 requirement in Ras-driven tumorigenesis in mouse and human tissue. Delivery of the IQGAP1 WW peptide sequence that mediates Erk1/4 binding, moreover, disrupted IQGAP1-Erk1/2 interactions, abolished Ras/Raf-driven tumorigenesis, bypassed acquired resistance to the B-Raf inhibitor vemurafinib (PLX- 4032), and acts as a systemically deliverable therapeutic to significantly increase lifespan of tumor bearing mice. Scaffold-kinase interaction blockade (SKIB) acts by a mechanism distinct from direct kinase inhibition and represents a strategy to target over-active oncogenic kinase cascades in cancer.
Project description:RAS signalling through Phosphoinositide 3-kinase (PI3-Kinase) has been shown to have an essential role in tumour initiation and maintenance. RAS also regulates cell motility and tumor invasiveness, but the role of direct RAS binding to PI3-Kinase in this remains uncertain. Here, we provide evidence that disruption of RAS interaction with PI3-Kinase p110adecreases cell motility and prevents activation of Rac GTPase. Analysis of gene expression in cells lacking RAS interaction with p110areveals increased levels of the extracellular matrix glycoprotein Reelin and activation of its downstream pathway resulting in upregulation of E-Cadherin expression. Induction of the Reelin / E-Cadherin axis is also observed in Kras mutant lung tumours that are regressing due to blockade of RAS interaction with PI3-Kinase. Furthermore, loss of Reelin correlates with decreased survival of lung and breast cancer patients. Reelin thus plays a role in restraining RAS and PI3-kinase promotion of cell motility and potentially tumour metastasis.
Project description:RAS signalling through Phosphoinositide 3-kinase (PI3-Kinase) has been shown to have an essential role in tumour initiation and maintenance. RAS also regulates cell motility and tumor invasiveness, but the role of direct RAS binding to PI3-Kinase in this remains uncertain. Here, we provide evidence that disruption of RAS interaction with PI3-Kinase p110adecreases cell motility and prevents activation of Rac GTPase. Analysis of gene expression in cells lacking RAS interaction with p110areveals increased levels of the extracellular matrix glycoprotein Reelin and activation of its downstream pathway resulting in upregulation of E-Cadherin expression. Induction of the Reelin / E-Cadherin axis is also observed in Kras mutant lung tumours that are regressing due to blockade of RAS interaction with PI3-Kinase. Furthermore, loss of Reelin correlates with decreased survival of lung and breast cancer patients. Reelin thus plays a role in restraining RAS and PI3-kinase promotion of cell motility and potentially tumour metastasis. MEFs with or without RAS binding to p110a were seeded in a 10cm dish and left to attach during 24 hours. Full serum media was then removed and media with no FBS was added to the plates. Starvation was carried out during a period of 16 hours (over night starvation). Assay was performed in triplicates: for each genotype two diferent fibroblasts clones (and a mix of both of the clones) were used on the analysis. After starvation RNA was extracted using RNAsy kit (Quiagen). RNA was quantified and sent to Oxford Gene Technology microarray facility.
Project description:Heterogeneous nuclear ribonucleoproteins (hnRNPs) play a decisive role in alternative splicing, regulating the cell proteome and contributing to human diseases. hnRNPs are nuclear proteins but it is still an open question where they localize in the nucleus and what determines their tethering to nuclear assemblies in response to signals. Here we report that IQGAP1, a cytosolic scaffold protein, localizes in the nucleus of gastric cancer cells acting as a tethering module for hnRNPM as well as other spliceosome components. The IQGAP1-hnRNPM interaction alters, among others, the alternative splicing of ANAPC10 and is required for the response of hnRNPM to heat-induced stress signals. Together, IQGAP1 and hnRNPM promote gastric cancer cell growth while their depletion leads to cell cycle arrest and halts tumour progression. We propose that IQGAP1 localizes in the nucleus and coordinates gastric tumour growth by recruiting, in response to stress-signals, spliceosome components that drive cell cycle progression.
Project description:Genetic alterations that activate protein kinase A (PKA) signaling are found across many tumor types, but their downstream oncogenic mechanisms are poorly understood. We used global phosphoproteomics and kinome activity profiling to map the conserved signaling outputs driven by diverse genetic changes that activate PKA in cancer. We define two consensus networks of effectors downstream of PKA in cancer models including melanoma and fibrolamellar carcinoma [FLC]. One is centered on RAS/MAPK components and a second involves Aurora Kinase A (AURKA). We find that AURKA stabilizes c-MYC and n-MYC protein levels and expression programs in PKA-dependent tumor models, in part via a positive feedback loop mediated by the oncogenic kinase PIM2. This process can be suppressed by conformation-disrupting AURKA inhibitors such as CD-532. Our findings elucidate two independent mechanisms of PKA-driven tumor cell growth and designate drug targets for study in FLC and other PKA-dependent malignancies.
Project description:Activating mutations in RAS GTPases drive one fifth of cancers, but poor understandings of many RAS effectors and regulators, and of the roles of their different paralogs, continue to impede drug development. We developed a multi-stage discovery and screening process to understand RAS function and identify RAS-related susceptibilities in lung adenocarcinoma. Using affinity purification mass spectrometry (AP/MS), we generated a protein-protein interaction map of the RAS pathway containing thousands of interactions. From this network we constructed a CRISPR dual knockout library targeting 119 RAS-related genes that we screened for genetic interactions (GIs). We found important new effectors of RAS-driven cellular functions, RADIL and the GEF RIN1, and over 250 synthetic lethal GIs, including a potent KRAS-dependent interaction between RAP1GDS1 and RHOA. Many GIs link specific paralogs within and between gene families. These findings illustrate the power of the multiomic approach to identify synthetic lethal combinations for hitherto undruggable cancers.
Project description:Acute myeloid leukemia (AML) is fatal in majority of adults. Identification of new therapeutic targets and their pharmacologic modulators are needed to improve outcomes. Previous studies had shown that immunization of rabbits with normal peripheral WBCs that had been incubated with fluorodinitrobenzene elicited high titer antibodies that bound to a spectrum of human leukemias. We report that proteomic analyses of immunoaffinity-purified lysates of primary AML cells showed enrichment of scaffolding protein IQGAP1. Immunohistochemistry and gene-expression analyses confirmed IQGAP1 mRNA overexpression in various cytogenetic subtypes of primary human AML compared to normal hematopoietic cells. shRNA knockdown of IQGAP1 blocked proliferation and clonogenicity of human leukemia cell-lines. To develop small molecules targeting IQGAP1 we performed in-silico screening of 212,966 compounds, selected 4 hits targeting IQGAP1-GRD domain, and conducted SAR of ‘fittest hit’ to identify UR778Br, a prototypical agent targeting IQGAP1. UR778Br inhibited proliferation, induced apotosis, G2/M arrest, and colony formation by leukemia cell-lines and primary-AML while sparing normal marrow cells. IQGAP1/F-actin showed co-localization and UR778Br induced filopodia formation in U937 cells. UR778Br exhibited favorable ADME/T profiles and drug-likeness to treat AML. In summary, AML shows dependency on IQGAP1 and UR778Br, identified through in-silico studies, selectively targeted AML cells while sparing normal marrow.
Project description:PROTACs (Proteolysis-Targeting Chimeras) represent a revolutionary new class of drugs that selectively degrade proteins of interest from cells. PROTACs targeting oncogenes are avidly being explored for cancer therapies, with several currently in clinical trials. Drug resistance represents a significant challenge in cancer therapies, and the mechanism by which cancer cells acquire resistance to protein degraders remains poorly understood. Here, we applied proteomics approaches to elucidate resistance mechanisms to protein degrader therapies in cancer cells. Our studies revealed acquired resistance to degrader therapies in cancer cells can be mediated by upregulation of the ATP-dependent drug efflux pump MDR1. Degrader-resistant cells could be re-sensitized to PROTACs through co-administering MDR1 inhibitors. Notably, MDR1 is frequently overexpressed in cancer, and cancer cell lines overexpressing MDR1 exhibited intrinsic resistance to protein degraders, requiring co-treatment with MDR1 inhibitors to achieve protein degradation and therapeutic response. Notably, co-treatment of MDR1-overexpressing K-ras mutant colorectal cancer cells with MEK1/2 or K-ras degraders and the dual ErbB receptor/MDR1 inhibitor lapatinib exhibited potent drug synergy due to simultaneous blockade of MDR1 activity and ErbB receptor-driven resistance. Together, our findings showed overexpression of MDR1 can promote both intrinsic and acquired resistance to protein degraders in cancer cells and that concurrent blockade of MDR1 will likely be required to achieve durable protein degradation and therapeutic response.
Project description:Oncogenic ras activates several signaling pathways that cooperate in cell transformation. They include the ERK/MAP kinase pathway, the PI3K pathway and the Ral pathway among others. Surprisingly, in primary human fibroblasts, oncogenic ras expression induces senescence not transformation, but upon knockdown of ERK2 senescence is bypassed and transformation is stimulated. We used microarrays to characterize the gene expression programme of cells transformed by oncogenic ras, telomerase and knockdown of the ERK2 kinase.