DNA repair deficiency sensitizes lung cancer cells to NAD⁺ biosynthesis blockade

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Abstract

Synthetic lethality is an efficient mechanism-based approach to selectively target DNA repair defects. ERCC1 deficiency is frequently found in non-small cell lung cancers, making this DNA repair protein an attractive target for exploiting synthetic lethal approaches in this disease. Using unbiased proteomic and metabolic high-throughput profiling on a unique in-house generated isogenic model of ERCC1 deficiency, we found marked metabolic rewiring of ERCC1-deficient populations, including decreased levels of the metabolite NAD+ and reduced expression of the rate-limiting NAD+ biosynthetic enzyme nicotinamide phosphoribosyltransferase (NAMPT). We further evidenced reduced NAMPT expression in NSCLC samples with low levels of ERCC1. These metabolic alterations were a primary effect of ERCC1 deficiency, and caused selective exquisite sensitivity to small molecule NAMPT inhibitors, both in vitro — ERCC1-deficient cells being approximately 1000 times more sensitive — and in vivo. Using transmission electronic microscopy and functional metabolic studies, we found that ERCC1-deficient cells harbor mitochondrial defects. We propose a model where NAD+ acts as a regulator of ERCC1-deficient NSCLC fitness. These findings open therapeutic opportunities that exploit a yet undescribed nuclear — mitochondrial synthetic lethal relationship in cancer cells, and highlight the potential for targeting DNA repair/metabolic crosstalks for cancer therapy.

Authors

Mehdi Touat, Tony Sourisseau, Nicolas Dorvault, Roman M. Chabanon, Marlène Garrido, Daphné Morel, Dragomir B. Krastev, Ludovic Bigot, Julien Adam, Jessica Frankum, Sylvère Durand, Clement Pontoizeau, Sylvie Souquère, Mei-Shiue Kuo, Sylvie Sauvaigo, Faraz Mardakheh, Alain Sarasin, Ken A. Olaussen, Luc Friboulet, Frédéric Bouillaud, Gérard Pierron, Alan Ashworth, Anne Lombès, Christopher J. Lord, Jean-Charles Soria, Sophie Postel-Vinay

Methyldopa blocks MHC class II binding to disease-specific antigens in autoimmune diabetes

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Abstract

Major histocompatibility (MHC) class II molecules are strongly associated with many autoimmune disorders. In type 1 diabetes, the DQ8 molecule is common, confers significant disease risk and is involved in disease pathogenesis. We hypothesized blocking DQ8 antigen presentation would provide therapeutic benefit by preventing recognition of self-peptides by pathogenic T cells. We used the crystal structure of DQ8 to select drug-like small molecules predicted to bind structural pockets in the MHC antigen-binding cleft. A limited number of the predicted compounds inhibited DQ8 antigen presentation in vitro with one compound preventing insulin autoantibody production and delaying diabetes onset in an animal model of spontaneous autoimmune diabetes. An existing drug of similar structure, methyldopa, specifically blocked DQ8 in recent-onset patients with type 1 diabetes along with reducing inflammatory T cell responses toward insulin, highlighting the relevance of blocking disease-specific MHC class II antigen presentation to treat autoimmunity.

Authors

David A. Ostrov, Aimon Alkanani, Kristen A. McDaniel, Stephanie Case, Erin E. Baschal, Laura Pyle, Samuel Ellis, Bernadette Pöllinger, Katherine J. Seidl, Viral N. Shah, Satish K. Garg, Mark A. Atkinson, Peter A. Gottlieb, Aaron W. Michels

STAT3-enhancing germline mutations contribute to tumor-extrinsic immune evasion

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Abstract

Immune evasion and the suppression of anti-tumor responses during cancer progression are considered hallmarks of cancer and are typically attributed to tumor-derived factors. Although the molecular basis for the crosstalk between tumor and immune cells is an area of active investigation, whether host-specific germline variants can dictate immunosuppressive mechanisms has remained a challenge to address. A commonly occurring germline mutation (c.1162G>A/rs351855 G/A) in the FGFR4 (CD334) gene enhances STAT3 signaling and is associated with poor prognosis and accelerated progression of multiple cancer types. Here, using rs351855 single nucleotide polymorphism (SNP) knock-in transgenic mice and Fgfr4 knockout mice, we reveal the genotype-specific gain of immunological function of suppressing the CD8/CD4+FOXP3+CD25+ve regulatory T cell ratio in vivo. Furthermore, using knock-in transgenic mouse models for lung and breast cancers, we establish the host-specific tumor-extrinsic functions of STAT3-enhancing germline variants in impeding the tumor infiltration of CD8 T cells. Thus, STAT3-enhancing germline receptor variants contribute to immune evasion through their pleiotropic functions in immune cells.

Authors

Daniel Kogan, Alexander Grabner, Christopher Yanucil, Christian Faul, Vijay Kumar Ulaganathan

Loss-of-function CARD8 mutation causes NLRP3 inflammasome activation and Crohn’s disease

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Abstract

In these studies we evaluated the contribution of the NLRP3 inflammasome to Crohn’s disease (CD) in a kindred containing individuals having a missense mutation in CARD8, a protein known to inhibit this inflammasome. Whole exome sequencing and PCR studies identified that the affected individuals had a V44I mutation in a single allele of the T60 isoform of CARD8. The serum levels of IL-1β in the affected individuals were increased compared with that in healthy controls and their peripheral monocytes produced increased amounts of IL-1β when stimulated by NLRP3 activators. Immunoblot studies probing the basis of these findings showed that mutated T60 CARD8 fails to down-regulate the NLRP3 inflammasome because it does not bind to NLRP3 and inhibit its oligomerization. In addition, these studies showed that mutated T60 CARD8 exerts a dominant negative effect by its capacity to bind to and form oligomers with unmutated T60 or T48 CARD8 that impede their binding to NLRP3. Finally, inflammasome activation studies revealed that intact but not mutated CARD8 prevents NLRP3 deubiquitination and serine dephosphorylation. CD due to a CARD8 mutation was not effectively treated by anti-TNF-α, but did respond to IL-1β inhibitors. Thus, patients with anti-TNF-α-resistant CD may respond to this treatment option.

Authors

Liming Mao, Atsushi Kitani, Morgan Similuk, Andrew J. Oler, Lindsey Albenberg, Judith Kelsen, Atiye Aktay, Martha Quezado, Michael Yao, Kim Montgomery-Recht, Ivan J. Fuss, Warren Strober

Modifier variant of METTL13 suppresses human GAB1-associated profound deafness

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Abstract

A modifier variant can abrogate risk of a monogenic disorder. DFNM1 is a locus on chromosome 1 encoding a dominant suppressor of human DFNB26 recessive, profound deafness. Here, we report that DFNB26 is associated with a substitution (p.Gly116Glu) in the pleckstrin-homology-domain of GAB1, an essential scaffold in the MET/HGF pathway. A dominant substitution (p.Arg544Gln) of METTL13, encoding a predicted methyltransferase, is the DFNM1 suppressor of GAB1-associated deafness. In zebrafish, human METTL13 mRNA harboring the modifier allele rescues the GAB1 associated morphant phenotype. In mouse, GAB1 and METTL13 co-localize in auditory sensory neurons, and METTL13 co-immunoprecipitates with GAB1 and SPRY2, indicating at least a tripartite complex. Expression of MET-signaling genes in human lymphoblastoid cells of individuals homozygous for p.Gly116Glu GAB1 revealed dysregulation of HGF, MET, SHP2, and SPRY2, all of which have reported variants associated with deafness. However, SPRY2 was not dysregulated in normal-hearing humans homozygous for both the GAB1 DFNB26 deafness variant and the dominant METTL13 deafness suppressor, indicating a plausible mechanism of suppression. Identification of METTL13-based modification of MET-signaling provides potential therapeutic strategy for a wide range of associated hearing disorders. Furthermore, MET-signaling is essential for diverse functions in many tissues including the inner ear. Therefore, identification of the modifier of MET-signaling is likely to have broad clinical implications.

Authors

Rizwan Yousaf, Zubair M. Ahmed, Arnaud P.J. Giese, Robert J. Morell, Ayala Lagziel, Alain Dabdoub, Edward R. Wilcox, Sheikh Riazuddin, Thomas B. Friedman, Saima Riazuddin

Pain control through selective chemo-axotomy of centrally projecting TRPV1⁺ sensory neurons

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Abstract

Transient vanilloid potential 1 (TRPV1) agonists are emerging as highly efficacious non-opioid analgesics in preclinical studies. These drugs selectively lesion TRPV1+ primary sensory afferents, which are responsible for the transmission of many noxious stimulus modalities. Resiniferatoxin (RTX) is a very potent and selective TRPV1 agonist and is a promising candidate for treating many types of pain. Recent work establishing intrathecal application of RTX for the treatment of pain resulting from advanced cancer has demonstrated profound analgesia in client-owned dogs with osteosarcoma. The present study uses transcriptomics and histochemistry to examine the molecular mechanism of RTX action in rats, in clinical canine subjects, and in one human subject with advanced cancer treated for pain using intrathecal RTX. In all three species we observe a strong analgesic action, yet this was accompanied by limited transcriptional alterations at the level of the DRG. Functional and neuroanatomical studies demonstrated that intrathecal RTX largely spares susceptible neuronal perikarya, which remain active peripherally, but unable to transmit signals to the spinal cord. The results demonstrate that central chemo-axotomy of the TRPV1+ afferents underlies RTX analgesia and refine the neurobiology underlying effective clinical use of TRPV1 agonists for pain control.

Authors

Matthew R. Sapio, John K. Neubert, Danielle M. LaPaglia, Dragan Maric, Jason M. Keller, Stephen J. Raithel, Eric L. Rohrs, Ethan M. Anderson, John A. Butman, Robert M. Caudle, Dorothy C. Brown, John D. Heiss, Andrew J. Mannes, Michael J. Iadarola

FoxO transcription factors are required for hepatic HDL-cholesterol clearance

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Abstract

Insulin resistance and type 2 diabetes are associated with low levels of high-density lipoprotein-cholesterol (HDL-C). The insulin-repressible FoxO transcription factors are potential mediators of insulin’s effect on HDL-C. FoxOs mediate a substantial portion of insulin-regulated transcription, and poor FoxO repression is thought to contribute to the excessive glucose production in diabetes. In this work, we show that mice with liver-specific triple FoxO knockout (L-FoxO1,3,4), which are known to have reduced hepatic glucose production, also have increased HDL-C. This was associated with decreased expression of HDL-C clearance factors, scavenger receptor class B type I (SR-BI) and hepatic lipase, and defective selective uptake of HDL-cholesteryl ester by the liver. The phenotype could be rescued by re-expression of SR-BI. These findings demonstrate that hepatic FoxOs are required for cholesterol homeostasis and HDL-mediated reverse cholesterol transport to the liver.

Authors

Samuel X. Lee, Markus Heine, Christian Schlein, Rajasekhar Ramakrishnan, Jing Liu, Gabriella Belnavis, Ido Haimi, Alexander W. Fischer, Henry Ginsberg, Joerg Heeren, Franz Rinninger, Rebecca A. Haeusler

Ribonuclease inhibitor 1 regulates erythropoiesis by controlling GATA1 mRNA translation

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Abstract

Ribosomal proteins (RP) regulate specific gene expression by selectively translating subsets of mRNAs. Indeed, in Diamond–Blackfan anaemia and 5q- syndrome, mutations in RP genes lead to a specific defect in erythroid gene translation and cause anaemia. Little is known about the molecular mechanisms of selective mRNA translation and involvement of ribosomal-associated factors in this process. Ribonuclease inhibitor (RNH1) is an ubiquitously expressed protein that binds to and inhibits pancreatic-type ribonucleases. Here we report that RNH1 binds to ribosomes and regulates erythropoiesis by controlling translation of the erythroid transcription factor GATA1. Rnh1-deficient mice die between embryonic days E8.5 to E10 due to impaired production of mature erythroid cells from progenitor cells. In Rnh1-deficient embryos, mRNA levels of Gata1 are normal, but GATA1 protein levels are decreased. At the molecular level, we found that RNH1 binds to the 40S subunit of ribosomes and facilitates polysome formation on Gata1 mRNA to confer transcript-specific translation. Further, RNH1 knock down in human CD34+ progenitor cells decreased erythroid differentiation without affecting myelopoiesis. Our results reveal an unsuspected role for RNH1 in the control of GATA1 mRNA translation and erythropoiesis.

Authors

Vijaykumar Chennupati, Diogo F.T. Veiga, Kendle M. Maslowski, Nicola Andina, Aubry Tardivel, Eric Chi-Wang Yu, Martina Stilinovic, Cedric Simillion, Michel A. Duchosal, Manfredo Quadroni, Irene Roberts, Vijay G. Sankaran, H. Robson MacDonald, Nicolas Fasel, Anne Angelillo-Scherrer, Pascal Schneider, Trang Hoang, Ramanjaneyulu Allam

Tuberous sclerosis complex–associated CNS abnormalities depend on hyperactivation of mTORC1 and Akt

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Abstract

Tuberous sclerosis complex (TSC) is a dominantly inherited disease, caused by hyperactivation of the mTORC1 pathway and characterized by the development of hamartomas and benign tumors, also in the brain. Among the neurological manifestations associated with TSC, the tumor progression of static subependymal nodules (SENs) into subependymal giant cell astrocytomas (SEGAs) is one of the major causes of morbidity and shortened life expectancy. To date, mouse modeling has failed in reproducing these two lesions. Here we report that simultaneous hyperactivation of mTORC1 and Akt pathways by codeletion of Tsc1 and Pten, selectively in postnatal neural stem cells (pNSCs), is required for the formation of bona fide SENs and SEGAs. Notably, both lesions closely recapitulate the pathognomonic morphological and molecular features of the corresponding human abnormalities. The establishment of long-term expanding pNSC lines from mouse SENs and SEGAs made possible the identification of mTORC2 as one of the mediators conferring tumorigenic potential to SEGA pNSCs. Of note, in spite of concurrent Akt hyperactivation in mouse brain lesions, single mTOR inhibition by rapamycin was sufficient to strongly impair mouse SEGA growth. This study provides the first evidence that, concomitant with mTORC1 hyperactivation, sustained activation of Akt and mTORC2 in pNSCs is a mandatory step for the induction of SENs and SEGAs and, at the same time, makes available an unprecedented NSC-based in vivo/in vitro model to be exploited for identifying actionable targets in TSC.

Authors

Paola Zordan, Manuela Cominelli, Federica Cascino, Elisa Tratta, Pietro L. Poliani, Rossella Galli

A controlled human malaria infection model enabling evaluation of transmission-blocking interventions

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Abstract

BACKGROUND. Drugs and vaccines that can interrupt the transmission of Plasmodium falciparum will be important for malaria control and elimination. However, models for early clinical evaluation of candidate transmission-blocking interventions are currently unavailable. Here we describe a new model for evaluating malaria transmission from humans to Anopheles mosquitoes using controlled human malaria infection (CHMI). METHODS. Seventeen healthy malaria-naïve volunteers underwent CHMI by intravenous inoculation of P. falciparum-infected erythrocytes to initiate blood-stage infection. Seven to eight days after inoculation participants received piperaquine (480 mg) to attenuate asexual parasite replication while allowing gametocytes to develop and mature. Primary endpoints were development of gametocytemia, the transmissibility of gametocytes from humans to mosquitoes, and the safety and tolerability of the CHMI transmission model. To investigate in-vivo gametocytocidal drug activity in this model, participants were either given an experimental antimalarial, artefenomel (500 mg), a known gametocytocidal drug, primaquine (15 mg), or remained untreated during the period of gametocyte carriage. RESULTS. Male and female gametocytes were detected in all participants, and transmission to mosquitoes was achieved from 8/11 (73%) participants evaluated. Compared to untreated controls (n = 7), primaquine (15 mg, n = 5) significantly reduced gametocyte burden (P = 0.01), while artefenomel (500 mg, n = 4) had no effect. Adverse events (AEs) were mostly mild or moderate. Three AEs were assessed as severe — fatigue, elevated alanine aminotransferase, and elevated aspartate aminotransferase — and were attributed to malaria infection. Transaminase elevations were transient, asymptomatic, and resolved without intervention. CONCLUSION. We report the safe and reproducible induction of P. falciparum gametocytes in healthy malaria-naïve volunteers at densities infectious to mosquitoes, thereby demonstrating the potential for evaluating transmission-blocking interventions in this model. TRIAL REGISTRATION. ClinicalTrials.gov NCT02431637 and NCT02431650 FUNDING. Bill & Melinda Gates Foundation

Authors

Katharine A. Collins, Claire Y.T. Wang, Matthew Adams, Hayley Mitchell, Melanie Rampton, Suzanne Elliott, Isaie J. Reuling, Teun Bousema, Robert Sauerwein, Stephan Chalon, Jörg J. Möhrle, James S. McCarthy