JunD, not c-Jun, is the AP-1 transcription factor required for Ras-induced lung cancer
E. Josue Ruiz, … , Julian Downward, Axel Behrens
E. Josue Ruiz, … , Julian Downward, Axel Behrens
Published July 8, 2021
Citation Information: JCI Insight. 2021;6(13):e124985. https://doi.org/10.1172/jci.insight.124985.
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Research Article Cell biology Oncology

JunD, not c-Jun, is the AP-1 transcription factor required for Ras-induced lung cancer

Abstract

The AP-1 transcription factor c-Jun is required for Ras-driven tumorigenesis in many tissues and is considered as a classical proto-oncogene. To determine the requirement for c-Jun in a mouse model of K-RasG12D–induced lung adenocarcinoma, we inducibly deleted c-Jun in the adult lung. Surprisingly, we found that inactivation of c-Jun, or mutation of its JNK phosphorylation sites, actually increased lung tumor burden. Mechanistically, we found that protein levels of the Jun family member JunD were increased in the absence of c-Jun. In c-Jun–deficient cells, JunD phosphorylation was increased, and expression of a dominant-active JNKK2-JNK1 transgene further increased lung tumor formation. Strikingly, deletion of JunD completely abolished Ras-driven lung tumorigenesis. This work identifies JunD, not c-Jun, as the crucial substrate of JNK signaling and oncogene required for Ras-induced lung cancer.

Authors

E. Josue Ruiz, Linxiang Lan, Markus Elmar Diefenbacher, Eva Madi Riising, Clive Da Costa, Atanu Chakraborty, Joerg D. Hoeck, Bradley Spencer-Dene, Gavin Kelly, Jean-Pierre David, Emma Nye, Julian Downward, Axel Behrens

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Figure 1

c-Jun is tumor suppressive in the KRasG12D lung adenocarcinoma model.

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c-Jun is tumor suppressive in the KRasG12D lung adenocarcinoma model. (A...
(A) Genetic alterations in JUN and KRAS genes in human LADC. Each column represents a tumor sample (n = 230). Data from TCGA were analyzed using cBioportal software. (B) Kaplan-Meier plot showing the association between JUN expression and patient survival. Analysis performed using KM plotter lung cancer database (cut-off median). (C) Schematic representation of c-Junfl/fl; lsl-KRasG12D mouse model. Conditional c-Jun deletion and K-RasG12D expression in the lung was induced by intratracheal intubation (i.t.) with adenovirus carrying Cre recombinase (Adeno-Cre). LoxP (locus of recombination) sites are indicated by black triangles. LSL, stop cassette flanked by 2 loxP sites. (D) H&E and TTF-1 antibody stains of lung sections from mice of the indicated genotypes, 12 weeks after intubation. Scale bars: 2 mm (whole sections), 50 μm (magnified tumor areas). (E) Quantification of the tumor burden in whole lungs isolated from K-RasG12D (4 mice/20 lobes) and c-JunΔ/Δ; K-RasG12D (3 mice/14 lobes) mice. Dots, individual lobes; red horizontal line, median. P values calculated using unpaired t test with Welch’s correction. (F) Violin plots quantifying the percentage of Ki67+ cells in lung tumors from mice of the indicated genotypes. K-RasG12D (4 mice/36 tumors) and c-JunΔ/Δ; K-RasG12D (3 mice/48 tumors). Each data point represents one tumor. Red horizontal line, median. P values calculated using unpaired t test with Welch’s correction. (G) c-Jun, phospho–c-JunSer63, phospho–c-JunSer73/phospho-JunDSer100, and JunD antibody stains of lung tumors from mice of the indicated genotypes. Scale bars: 50 μm, 5 μm (inset). (H) Schematic summary: c-Jun is tumor-suppressor (left). In the absence of c-Jun, K-Ras–dependent tumors increase, possibly through activation of JunD (right). JunDP, phospho-JunD.