Project description:The molecular chaperone HSP90 aids the maturation of a diverse but select set of metastable protein clients, many of which are key to a variety of signal transduction pathways. HSP90 function has been best investigated in animal and fungal systems, where inhibition of the chaperone has exceptionally diverse effects, ranging from reversing oncogenic transformation to facilitating the acquisition of drug resistance. Inhibition of HSP90 in the model plant Arabidopsis thaliana uncovers novel morphologies dependent on normally cryptic genetic variation and increases stochastic variation inherent to developmental processes. The biochemical activity of HSP90 is strictly conserved between animals and plants. However, the substrates and pathways dependent on HSP90 in plants are poorly understood. Progress has been impeded by reliance on light-sensitive HSP90 inhibitors due to redundancy in the A. thaliana HSP90 gene family. Here we present phenotypic and genome-wide expression analyses of A. thaliana with constitutively reduced HSP90 levels achieved by RNAi targeting. HSP90 reduction affects a variety of quantitative life-history traits, including flowering time and total seed set, and decreases developmental stability. Further, by quantitative analysis of morphological phenotypes, we demonstrate that HSP90-reduction increases phenotypic diversity in both seedlings and adult plants. Several morphologies are synergistically affected by HSP90 and growth temperature. Genome-wide expression analyses also suggest a central role for HSP90 in the genesis and maintenance of plastic responses. The expression results are substantiated by examination of the response of HSP90-reduced plants to attack by caterpillars of the generalist herbivore Trichoplusia ni. HSP90 reduction potentiates a more robust herbivore defense response. In sum, we propose that HSP90 exerts global effects on the environmental responsiveness of plants to many different stimuli. The comprehensive set of HSP90-reduced lines described here is a vital instrument to further examine the role of HSP90 as a central interface between organism, development, and environment. Experiment Overall Design: Three differerent experiments were performed. One experiment included lines RNAi-A1, RNAi-A3, and Control-2, with two biological replicates and one technical replicate per line. The second included lines RNAi-A2, RNAi-B1, RNAi-C1, Control-1, and Control-3, with three biological replicates per line. The third included the three single-isoform T-DNA insertion lines, along with the Col-0 control, with three biological replicates per line. See Sangster et al. "Phenotypic Diversity and Altered Environmental Plasticity in Arabidopsis thaliana with Reduced HSP90 Levels" for details of construct construction and further experimental rationale.

Project description:The molecular chaperone HSP90 aids the maturation of a diverse but select set of metastable protein clients, many of which are key to a variety of signal transduction pathways. HSP90 function has been best investigated in animal and fungal systems, where inhibition of the chaperone has exceptionally diverse effects, ranging from reversing oncogenic transformation to facilitating the acquisition of drug resistance. Inhibition of HSP90 in the model plant Arabidopsis thaliana uncovers novel morphologies dependent on normally cryptic genetic variation and increases stochastic variation inherent to developmental processes. The biochemical activity of HSP90 is strictly conserved between animals and plants. However, the substrates and pathways dependent on HSP90 in plants are poorly understood. Progress has been impeded by reliance on light-sensitive HSP90 inhibitors due to redundancy in the A. thaliana HSP90 gene family. Here we present phenotypic and genome-wide expression analyses of A. thaliana with constitutively reduced HSP90 levels achieved by RNAi targeting. HSP90 reduction affects a variety of quantitative life-history traits, including flowering time and total seed set, and decreases developmental stability. Further, by quantitative analysis of morphological phenotypes, we demonstrate that HSP90-reduction increases phenotypic diversity in both seedlings and adult plants. Several morphologies are synergistically affected by HSP90 and growth temperature. Genome-wide expression analyses also suggest a central role for HSP90 in the genesis and maintenance of plastic responses. The expression results are substantiated by examination of the response of HSP90-reduced plants to attack by caterpillars of the generalist herbivore Trichoplusia ni. HSP90 reduction potentiates a more robust herbivore defense response. In sum, we propose that HSP90 exerts global effects on the environmental responsiveness of plants to many different stimuli. The comprehensive set of HSP90-reduced lines described here is a vital instrument to further examine the role of HSP90 as a central interface between organism, development, and environment. Keywords: HSP90, mutant comparison

Project description:The crizotinibâresistant ALKF1174L mutation arises de novo in neuroblastoma (NB) and is acquired in ALK translocation-driven cancers, lending impetus to the development of novel ALK inhibitors with different modes of action. The diaminopyrimidine TAE684 and its derivative ceritinib (LDK378), which are structurally distinct from crizotinib, are active against NB cells expressing ALKF1174L. Here we demonstrate acquired resistance to TAE684 and LDK378 in ALKF1174L-driven human NB cells that is linked to overexpression and activation of the AXL tyrosine kinase and epithelial-to-mesenchymal transition (EMT). AXL phosphorylation conferred TAE684 resistance to NB cells through upregulated ERK signaling. Inhibition of AXL partly rescued TAE684 resistance, resensitizing these cells to this compound. AXL activation in resistant cells was mediated through increased expression of the active form of its ligand, GAS6, which also served to stabilize the AXL protein. Although ectopic expression of AXL and TWIST2 individually in TAE684-sensitive parental cells led to the elevated expression of mesenchymal markers and invasive capacity, only AXL overexpression induced resistance to TAE684 as well. TAE684-resistant cells showed greater sensitivity to HSP90 inhibition than did their parental counterparts, with downregulation of AXL and AXL-mediated ERK signaling. Our studies indicate that aberrant AXL signaling and development of an EMT phenotype underlie resistance of ALKF1174L-driven NB cells to TAE684 and its derivatives. We suggest that the combination of ALK and AXL or HSP90 inhibitors be considered to delay the emergence of such resistance. In order to understand the molecular mechanisms driving resistance to ALK inhibition in ALK-mutated neuroblatoma, we established cell line models of resistance to TAE684, an ALK inhibitor, by treating SH-SY5Y cells (bearing the ALKF1174L mutation) with increasing concentration of this compound over time. We then performed an analysis of gene expression changes genome wide using Affymetrix U133 Plus 2 arrays, by comparing the TAE684-sensitive parental SH-SY5Y cells to the TAE684-resistant SH-SY5Y cells (named SY5Y-TR1). For that experiment, we analyzed gene expression variations by comparing the parental SH-SY5Y (control sample) to the resistant SY5Y-TR1 cells. So 2 samples were analyzed, with 3 replicates run for each.

Project description:Aggressive double and triple hit (DH/TH) DLBCL feature activation of Hsp90 stress pathways. Herein, we show that Hsp90 controls post-transcriptional dynamics of key mRNA species including those encoding BCL6, MYC and BCL2. Using a proteomics approach, we found that Hsp90 binds to and maintains activity of eIF4E (eukaryotic translation initiation factor 4E). EIF4E drives nuclear export and translation of BCL6, MYC and BCL2 mRNA. eIF4E RIP-sequencing in DLBCL suggests that nuclear eIF4E controls an extended program that includes BCR signaling, cellular metabolism and epigenetic regulation. Accordingly, eIF4E was required for survival of DLBCL including the most aggressive subtypes DH/TH lymphomas. Indeed, eIF4E inhibition induces tumor regression in cell line and patient-derived tumorgrafts of TH-DLBCL, even in the presence of elevated Hsp90 activity. Targeting Hsp90 is typically limited by counter-regulatory elevation of Hsp70B, which induces resistance to Hsp90 inhibitors. Surprisingly, we identify Hsp70 mRNA as an eIF4E target. In this way, eIF4E inhibition can overcome drug resistance to Hsp90 inhibitors. Accordingly, rational combinatorial inhibition of eIF4E and Hsp90 inhibitors resulted in cooperative anti-lymphoma activity in DH/TH DLBCL in vitro and in vivo. We found that eIF4E activity regulates the nuclear export of BCL6, MYC, and BCL2 in DH/TH DLBCLs. To determine the extent of nuclear eIF4E activity in DH/TH DLBCLs and how these programs can support the oncogenic activity of BCL6, MYC and/or BCL2 transcripts, we conducted eIF4E-RIP of nuclear RNA followed by RNA-sequencing in OCI-Ly1 cells in triplicates. To understand the changes in gene expression after ribavarin in a clinically relevant sample, we generated a patient-derived xenograft (PDX) in NSG mice from a de-identified specimen isolated from a patient prior to treatment harboring a triple-hit ABC-type DLBCL. PDX cells from passage four (PDX-4) were implanted into NSG mice. When tumors were palpable, mice were randomized to receive vehicle or 80 mg/kg/b.i.d. ribavarin intraperitoneally for 10 days. We isolated RNA from tumors treated with vehicle (n=2) or ribavarin (n=2) and performed mRNA-seq.

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HSP90 empowers evolution of resistance to hormonal therapy in human breast cancer models

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