Search

Clinical progress in multiple myeloma (MM), an incurable plasma cell (PC) neoplasia, has been driven by therapies that have limited applications beyond MM/PC neoplasias and do not target specific oncogenic mutations in MM. Instead, these agents target pathways critical for PC biology yet largely dispensable for malignant or normal cells of most other lineages. Here we systematically characterized the lineage-preferential molecular dependencies of MM through genome-scale clustered regularly interspaced short palindromic repeats (CRISPR) studies in 19 MM versus hundreds of non-MM lines and identified 116 genes whose disruption more significantly affects MM cell fitness compared with other malignancies. These genes, some known, others not previously linked to MM, encode transcription factors, chromatin modifiers, endoplasmic reticulum components, metabolic regulators or signaling molecules. Most of these genes are not among the top amplified, overexpressed or mutated in MM. Functional genomics approaches thus define new therapeutic targets in MM not readily identifiable by standard genomic, transcriptional or epigenetic profiling analyses., (© 2023. The Author(s), under exclusive licence to Springer Nature America, Inc.)

mTORC1 and GCN2 are serine/threonine kinases that control how cells adapt to amino acid availability. mTORC1 responds to amino acids to promote translation and cell growth while GCN2 senses limiting amino acids to hinder translation via eIF2α phosphorylation. GCN2 is an appealing target for cancer therapies because malignant cells can harness the GCN2 pathway to temper the rate of translation during rapid amino acid consumption. To isolate new GCN2 inhibitors, we created cell-based, amino acid limitation reporters via genetic manipulation of Ddit3 (encoding the transcription factor CHOP). CHOP is strongly induced by limiting amino acids and in this context, GCN2-dependent. Using leucine starvation as a model for essential amino acid sensing, we unexpectedly discovered ATP-competitive PI3 kinase-related kinase inhibitors, including ATR and mTOR inhibitors like torins, completely reversed GCN2 activation in a time-dependent way. Mechanistically, via inhibiting mTORC1-dependent translation, torins increased intracellular leucine, which was sufficient to reverse GCN2 activation and the downstream integrated stress response including stress-induced transcriptional factor ATF4 expression. Strikingly, we found that general translation inhibitors mirrored the effects of torins. Therefore, we propose that mTOR kinase inhibitors concurrently inhibit different branches of amino acid sensing by a dual mechanism involving direct inhibition of mTOR and indirect suppression of GCN2 that are connected by effects on the translation machinery. Collectively, our results highlight distinct ways of regulating GCN2 activity., Competing Interests: Conflict of interest P. J. M. is on the scientific advisory boards of Palleon Pharmaceuticals and ImCheck Pharma, neither of which have activities or interests related to this article. The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Heterobifunctional proteolysis-targeting chimeric compounds leverage the activity of E3 ligases to induce degradation of target oncoproteins and exhibit potent preclinical antitumor activity. To dissect the mechanisms regulating tumor cell sensitivity to different classes of pharmacological "degraders" of oncoproteins, we performed genome-scale CRISPR-Cas9-based gene editing studies. We observed that myeloma cell resistance to degraders of different targets (BET bromodomain proteins, CDK9) and operating through CRBN (degronimids) or VHL is primarily mediated by prevention of, rather than adaptation to, breakdown of the target oncoprotein; and this involves loss of function of the cognate E3 ligase or interactors/regulators of the respective cullin-RING ligase (CRL) complex. The substantial gene-level differences for resistance mechanisms to CRBN- versus VHL-based degraders explains mechanistically the lack of cross-resistance with sequential administration of these two degrader classes. Development of degraders leveraging more diverse E3 ligases/CRLs may facilitate sequential/alternating versus combined uses of these agents toward potentially delaying or preventing resistance., Competing Interests: Declaration of Interests F.V. receives research funding from Novo Ventures. P.G.R. reports research support from Oncopeptides, Celgene/BMS, and Takeda and is an advisory committee member for Karyopharm, Oncopeptides, Celgene/BMS, Takeda, Janssen, Sanofi, Secura Bio, and GSK. E.S.F. is a founder, science advisory board member, and equity holder in Civetta, Jengu (board member), and Neomorph; an equity holder in C4; and a consultant to Astellas, Novartis, Deerfield, and EcoR1. The Fischer lab receives or has received research funding from Novartis, Astellas, Ajax, and Deerfield. N.P.K. is a consultant to Epiphanes, Inc. W.C.H. is a consultant for Thermo Fisher, Solvasta, MPM Capital, Tyra Biosciences, Jubilant Therapeutics, Frontier Medicines, RAPPTA Therapeutics, and Parexel and is a founder of and advisor to KSQ Therapeutics. L.H.B. receives research funding from AstraZeneca and is a consultant for AstraZeneca and Genentech. B.L.E. has received research funding from Celgene and Deerfield. He has received consulting fees from GRAIL, and he serves on the scientific advisory boards for and holds equity in Skyhawk Therapeutics and Exo Therapeutics. J.E.B. is an author on United States patent applications licensed from the Dana-Farber Cancer Institute to C4 Therapeutics (TPD) and Tensha Therapeutics (now Roche; BRD4 inhibition). He is now an executive of and shareholder in Novartis AG. N.S.G. is a scientific founder, member of the scientific advisory board and equity holder in C4 Therapeutics, Syros Pharmaceuticals, Petra Pharmaceuticals, Ravenna, Inception, Allorion, Jengu, and Soltego (board member) and is the inventor on intellectual property licensed to these entities. R.S., G.M.M., S.G., R.d.M.S., and C.S.M. are authors on a patent application on the use of degraders. C.S.M. also discloses consultant/honoraria from Fate Therapeutics, Ionis Pharmaceuticals and FIMECS; employment of a relative with Takeda; and research funding from Janssen/Johnson & Johnson, TEVA, EMD Serono, Abbvie, Arch Oncology, Karyopharm, Sanofi, and Nurix., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Multinucleated giant cells (MGCs) are implicated in many diseases including schistosomiasis, sarcoidosis and arthritis. MGC generation is energy intensive to enforce membrane fusion and cytoplasmic expansion. Using receptor activator of nuclear factor kappa-Β ligand (RANKL) induced osteoclastogenesis to model MGC formation, here we report RANKL cellular programming requires extracellular arginine. Systemic arginine restriction improves outcome in multiple murine arthritis models and its removal induces preosteoclast metabolic quiescence, associated with impaired tricarboxylic acid (TCA) cycle function and metabolite induction. Effects of arginine deprivation on osteoclastogenesis are independent of mTORC1 activity or global transcriptional and translational inhibition. Arginine scarcity also dampens generation of IL-4 induced MGCs. Strikingly, in extracellular arginine absence, both cell types display flexibility as their formation can be restored with select arginine precursors. These data establish how environmental amino acids control the metabolic fate of polykaryons and suggest metabolic ways to manipulate MGC-associated pathologies and bone remodelling.

Heterologous enzymes and binding proteins were secreted by the moss Physcomitrella patens or anchored extracellularly on its cell membrane in order to functionalize the apoplast as a biochemical reaction compartment. This modular membrane anchoring system utilizes the signal peptide and the transmembrane segment of the somatic embryogenesis receptor-like kinase (SERK), which were identified in a comprehensive bioinformatic analysis of the P. patens genome. By fusing the soluble enzyme NanoLuc luciferase to the signal peptide, its secretion capability was confirmed in vivo. The membrane localization of hybrid proteins comprising the SERK signal peptide, NanoLuc or other functional modules, the SERK transmembrane anchor, and a C-terminal GFP reporter was demonstrated using fluorescence microscopy as well as site-specific proteolytic release of the extracellular enzyme domain. Our membrane anchoring system enables the expression of various functional proteins in the apoplast of P. patens, empowering this photoautotrophic organism for biotechnological applications.