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IRE1α RNase-dependent lipid homeostasis promotes survival in Myc-transformed cancers

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Abstract

Myc activation is a primary oncogenic event in many human cancers; however, these transcription factors are difficult to inhibit pharmacologically, suggesting that Myc-dependent downstream effectors may be more tractable therapeutic targets. Here we show that Myc overexpression induces endoplasmic reticulum (ER) stress and engages the IRE1α-XBP1 pathway through multiple molecular mechanisms in a variety of c-Myc- and N-Myc-dependent cancers. In particular, Myc-overexpressing cells require IRE1α-XBP1 signaling for sustained growth and survival in vitro and in vivo, dependent on elevated stearoyl-CoA-desaturase 1 (SCD1) activity. Pharmacological and genetic XBP1 inhibition induces Myc-dependent apoptosis, which is alleviated by exogenous unsaturated fatty acids. Of note, SCD1 inhibition phenocopies IRE1α RNase activity suppression in vivo. Furthermore, IRE1α inhibition enhances the cytotoxic effects of standard chemotherapy drugs used to treat c-Myc-overexpressing Burkitt’s lymphoma, suggesting that inhibiting the IRE1α-XBP1 pathway is a useful general strategy for treatment of Myc-driven cancers.

Authors

Hong Xie, Chih-Hang Anthony Tang, Jun H. Song, Anthony Mancuso, Juan R. Del Valle, Jin Cao, Yan Xiang, Chi V. Dang, Roy Lan, Danielle J. Sanchez, Brian Keith, Chih-Chi Andrew Hu, M. Celeste Simon

iRhom2 promotes lupus nephritis through TNF-α and EGFR signaling

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Abstract

Lupus nephritis (LN) often results in progressive renal dysfunction. The inactive Rhomboid 2 (iRhom2) is a newly identified key regulator of A disintegrin and metalloprotease 17 (ADAM17), whose substrates, such as TNF-α and heparin-binding EGF (HB-EGF), have been implicated in the pathogenesis of chronic kidney disease. Here we demonstrate that deficiency of iRhom2 protects the lupus-prone Fcgr2b–/– mice from developing severe kidney damage without altering anti-double stranded (ds) DNA Ab production, by simultaneously blocking the HB-EGF/EGFR and the TNF-α signaling in the kidney tissues. Unbiased transcriptome profiling of kidneys and kidney macrophages revealed that TNF-α and HB-EGF/EGFR signaling pathways are highly upregulated in Fcgr2b–/– mice; alterations that were diminished in the absence of iRhom2. Pharmacological blockade of either TNF-α or EGFR signaling protected Fcgr2b–/– mice from severe renal damage. Finally, kidneys from LN patients showed increased iRhom2 and HB-EGF expression, with interstitial HB-EGF expression significantly associated with chronicity indices. Our data suggest that activation of iRhom2/ADAM17-dependent TNF-α and EGFR signaling plays a crucial role in mediating irreversible kidney damage in LN, thereby uncovering a novel target for selective and simultaneous dual inhibition of two major pathological pathways in the effector arm of the disease.

Authors

Xiaoping Qing, Yurii Chinenov, Patricia Redecha, Michael Madaio, Joris J.T.H. Roelofs, Gregory Farber, Priya D. Issuree, Laura Donlin, David R. McIlwain, Tak W. Mak, Carl P. Blobel, Jane E. Salmon

Tumor infiltrating BRAF^V600E-specific CD4 T cells correlated with complete clinical response in melanoma

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Abstract

T cells specific for neoantigens encoded by mutated genes in cancers are increasingly recognized as mediators of tumor destruction after immune checkpoint inhibitor therapy or adoptive cell transfer. Unfortunately, most neoantigens result from random mutations and are patient specific, and some cancers contain few mutations to serve as potential antigens. We describe a patient with stage IV acral melanoma who obtained a complete response following adoptive transfer of tumor infiltrating lymphocytes (TIL). Tumor exome sequencing surprisingly revealed less than 30 somatic mutations, including oncogenic BRAF V600E. Analysis of the specificity of TIL identified rare CD4 T cells specific for BRAFV600E and diverse CD8 T cells reactive to non-mutated self-antigens. These specificities increased in blood after TIL transfer and persisted long term suggesting they contributed to the effective antitumor immune response. Gene transfer of the BRAFV600E-specific T cell receptor (TCR) conferred recognition of class II MHC positive cells expressing the BRAF mutation. Therapy with TCR engineered BRAFV600E-specific CD4+ T cells may have direct antitumor effects and augment CD8+ T cell responses to self and/or mutated tumor antigens in patients with BRAF mutated cancers.

Authors

Joshua R. Veatch, Sylvia M. Lee, Matthew Fitzgibbon, I-Ting Chow, Brenda Jesernig, Thomas Schmitt, Ying Ying Kong, Julia Kargl, A. McGarry Houghton, John A. Thompson, Martin McIntosh, William W. Kwok, Stanley R. Riddell

COP1-DET1-ETS axis regulates ERK transcriptome and sensitivity to MAPK inhibitors

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Abstract

Aberrant activation of MAPK signaling leads to activation of oncogenic transcriptomes. How MAPK signaling is coupled with transcriptional response in cancer is not fully understood. In gastrointestinal stromal tumor and melanoma, both with oncogenic MAPK activation, we find that ETV1 and other Pea3-ETS transcription factors are critical nuclear effectors of MAPK signaling that are regulated through protein stability. Expression of stabilized Pea3-ETS factors can partially rescue the MAPK transcriptome and cell viability after MAPK inhibition. To identify players involved in this process, we performed a pooled genome-wide RNAi screen using a novel fluorescence-based ETV1 protein stability sensor, and identified COP1, DET1, DDB1, UBE3C, PSMD4, and COP9 signalosome members. COP1 and DET1 loss led to decoupling between MAPK signaling and downstream transcriptional response, where MAPK inhibition failed to destabilize Pea3 factors and fully inhibit the MAPK transcriptome, thus resulting in decreased sensitivity to MAPK pathway inhibitors. We identified multiple COP1 and DET1 mutations in human tumors that were defective in degradation of Pea3-ETS factors. Two melanoma patients had de novo DET1 mutations arising after vemurafenib treatment. These observations indicate that MAPK signaling-dependent regulation of Pea3-ETS protein stability is a key signaling node in oncogenesis and therapeutic resistance to MAPK pathway inhibition.

Authors

Yuanyuan Xie, Zhen Cao, Elissa W.P. Wong, Youxin Guan, Wenfu Ma, Jenny Q. Zhang, Edward G. Walczak, Devan Murphy, Leili Ran, Inna Sirota, Shangqian Wang, Shipra Shukla, Dong Gao, Simon R.V. Knott, Kenneth Chang, Justin Leu, John Wongvipat, Cristina R. Antonescu, Gregory Hannon, Ping Chi, Yu Chen

Tie2 protects the vasculature against thrombus formation in systemic inflammation

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Abstract

Disordered coagulation contributes to death in sepsis and lacks effective treatments. Existing markers of disseminated intravascular coagulation (DIC) reflect its sequelae rather than its causes, delaying diagnosis and treatment. Here we show that disruption of the endothelial Tie2 axis is a sentinel event in septic DIC. Proteomics in septic DIC patients revealed a network involving inflammation and coagulation with the Tie2 antagonist, Angiopoietin-2 (Angpt-2), occupying a central node. Angpt-2 was strongly associated with traditional DIC markers including platelet counts, yet more accurately predicted mortality in two large independent cohorts (combined N = 1077). In endotoxemic mice, reduced Tie2 signaling preceded signs of overt DIC. During this early phase, intravital imaging of microvascular injury revealed excessive fibrin accumulation, a pattern remarkably mimicked by Tie2 deficiency even without inflammation. Conversely, Tie2 activation normalized pro-thrombotic responses by inhibiting endothelial tissue factor and phosphatidylserine exposure. Critically, Tie2 activation had no adverse effects on bleeding. These results mechanistically implicate Tie2 signaling as a central regulator of microvascular thrombus formation in septic DIC and indicate that circulating markers of the Tie2 axis could facilitate earlier diagnosis. Finally, interventions targeting Tie2 may normalize coagulation in inflammatory states while averting the bleeding risks of current DIC therapies.

Authors

Sarah J. Higgins, Karen De Ceunynck, John Kellum, Xiuying Chen, Xuesong Gu, Sharjeel A. Chaudhry, Sol Schulman, Towia A. Libermann, Shulin Lu, Nathan I. Shapiro, David C. Christiani, Robert Flaumenhaft, Samir M. Parikh

The deubiquitinase USP9X regulates FBW7 stability and suppresses colorectal cancer

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Abstract

The tumor suppressor FBW7 targets oncoproteins such as c-MYC for ubiquitylation and is mutated in several human cancers. We noted that in a significant percentage of colon cancers, FBW7 protein is undetectable despite the presence of FBW7 mRNA. To understand the molecular mechanism of FBW7 regulation in these cancers, we employed proteomics and identified the deubiquitinase USP9X as an FBW7 interactor. USP9X antagonised FBW7 ubiquitylation, and Usp9x deletion caused Fbw7 destabilization. Mice lacking Usp9x in the gut showed reduced secretory cell differentiation and increased progenitor proliferation, phenocopying Fbw7 loss. In addition, Usp9x inactivation impaired intestinal regeneration and increased tumor burden in colitis-associated intestinal cancer. c-Myc heterozygosity abrogated increased progenitor proliferation and tumor burden in Usp9x-deficient mice, suggesting that Usp9x suppresses tumor formation by regulating Fbw7 protein stability and thereby reducing c-Myc. Thus, we identify a novel tumor suppressor mechanism in the mammalian intestine that arises from the posttranslational regulation of FBW7 by USP9X independent of somatic FBW7 mutations.

Authors

Omar M. Khan, Joana Carvalho, Bradley Spencer-Dene, Richard Mitter, David Frith, Ambrosius P. Snijders, Stephen A. Wood, Axel Behrens

The epithelial-to-mesenchymal transition activator ZEB1 initiates a prometastatic competing endogenous RNA network

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Abstract

Epithelial tumor cells undergo epithelial-to-mesenchymal transition (EMT) to gain metastatic activity. Competing endogenous RNAs (ceRNAs) have binding sites for a common set of microRNAs (miRs) and regulate each other’s expression by sponging miRs. Here, we address whether ceRNAs govern EMT–driven metastasis. High miR-181b levels were correlated with an improved prognosis in human lung adenocarcinomas, and metastatic tumor cell lines derived from a murine lung adenocarcinoma model in which metastasis is EMT–driven were enriched in miR-181b targets. The EMT–activating transcription factor ZEB1 relieved a strong basal repression of integrin-α1 (ITGA1), which in turn upregulated adenylyl cyclase 9 (ADCY9) by sponging miR181b. Ectopic expression of the ITGA1 3’ untranslated region reversed miR-181b–mediated metastasis suppression and increased the levels of ADCY9, which promoted ZEB1–driven tumor cell migration and metastasis. In human lung adenocarcinomas, ITGA1 and ADCY9 levels were positively correlated, and an ADCY9–activated transcriptomic signature had poor-prognostic value. Thus, ZEB1 initiates a miR-181b–regulated ceRNA network to drive metastasis.

Authors

Xiaochao Tan, Priyam Banerjee, Xin Liu, Jiang Yu, Don L. Gibbons, Ping Wu, Kenneth L. Scott, Lixia Diao, Xiaofeng Zheng, Jing Wang, Ali Jalali, Milind Suraokar, Junya Fujimoto, Carmen Behrens, Xiuping Liu, Chang-gong Liu, Chad J. Creighton, Ignacio I. Wistuba, Jonathan M. Kurie

Epithelial-mesenchymal transition leads to NK cell–mediated metastasis-specific immunosurveillance in lung cancer

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Abstract

During epithelial-mesenchymal transition (EMT) epithelial cancer cells trans-differentiate into highly-motile, invasive, mesenchymal-like cells giving rise to disseminating tumor cells. Only few of these disseminated cells successfully metastasize. Immune cells and inflammation in the tumor microenvironment was shown to drive EMT, but few studies investigated the consequences of EMT on tumor immunosurveillance. In addition to initiating metastasis, we demonstrate that EMT confers increased susceptibility to NK cells and contributes, in part, to the inefficiency of the metastatic process. Depletion of NK cells allowed spontaneous metastasis without effecting primary tumor growth. EMT-induced modulation of E-cadherin and cell adhesion molecule 1 (CADM1) mediated increased susceptibility to NK cytotoxicity. Higher CADM1 expression correlates with improved patient survival in two lung and one breast adenocarcinoma patient cohorts and decreased metastasis. Our observation reveal a novel NK-mediated, metastasis-specific, immunosurveillance in lung cancer and presents a window of opportunity for the prevention of metastasis by boosting NK cell activity.

Authors

Peter J. Chockley, Jun Chen, Guoan Chen, David G. Beer, Theodore J. Standiford, Venkateshwar G. Keshamouni