DNA repair deficiency sensitizes lung cancer cells to NAD+ biosynthesis blockade
Mehdi Touat, … , Jean-Charles Soria, Sophie Postel-Vinay
Mehdi Touat, … , Jean-Charles Soria, Sophie Postel-Vinay
Published February 15, 2018
Citation Information: J Clin Invest. 2018;128(4):1671-1687. https://doi.org/10.1172/JCI90277.
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Research Article Oncology

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

Abstract

Synthetic lethality is an efficient mechanism-based approach to selectively target DNA repair defects. Excision repair cross-complementation group 1 (ERCC1) deficiency is frequently found in non–small-cell lung cancer (NSCLC), making this DNA repair protein an attractive target for exploiting synthetic lethal approaches in the 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 also found 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 1,000 times more sensitive than ERCC1-WT cells — 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 cell fitness. These findings open therapeutic opportunities that exploit a yet-undescribed nuclear-mitochondrial synthetic lethal relationship in NSCLC models, 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 R. 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

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Figure 9

Loss of ERCC1 results in increased ADP-ribosylation and a gradual decrease in NAMPT expression.

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Loss of ERCC1 results in increased ADP-ribosylation and a gradual decrea...
(A) ADP-ribosylation (ADPr) levels were measured by immunofluorescence in A549 cells not treated (NT) or treated with control (scramble siRNA) or ERCC1 siRNA (siERCC1). H2O2 exposure was used for inducing DNA damage. Olaparib was used as control for abrogation of PARP1-related ADP-ribosylation activity. Data are mean ADP-ribosylation activity ± SD from 1 of 3 independent experiments. (B) Representative Western blot of ERCC1 and NAMPT protein expression after acute ERCC1 silencing using siRNA in A549 cells. NT, nontransfected. Data were replicated in 2 independent experiments. (C) Western blot of ERCC1 and NAMPT protein expression after sequential transfections with shERCC1-coding viral particles in A549 cells. V1, V2, V3 indicate infections 1, 2, and 3, respectively, which were performed 10–15 days apart each. Data are from 1 experiment. (D and E) ADP-ribosylation levels were measured by immunofluorescence in the A549 isogenic model in the absence (D) or presence (E) of NMN supplementation. Data are mean ADP-ribosylation activity ± SD from 1 of 2 independent experiments. (F) Variations in NAMPT mRNA levels in A549 ERCC1-WT, ERCC1-Hez, and ERCC1-KO cell lines following 3-day exposure to nontoxic concentrations of the SIRT1 activator STR2104. Data represent mean 2–ΔΔCt ± SD from 1 experiment. Statistical analyses are indicated (2-way ANOVA adjusted using Sidak’s multiple comparison test). (G) Representative Western blot of NAMPT protein expression after 4-day exposure to nontoxic concentrations of STR2104. Data were replicated in 2 independent experiments. For A, D, E, statistical analyses are indicated (2-way ANOVA adjusted for multiple comparisons using Tukey’s t test).