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 3

c-JunAA increases lung tumor burden, phenocopying c-Jun deletion.

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c-JunAA increases lung tumor burden, phenocopying c-Jun deletion. (A) Sc...
(A) Schematic representation of c-JunAA/AA; lsl-KRasG12D mouse model. The c-JunAA allele lacks the JNK phosphorylation sites Ser63 and Ser73. Expression of K-RasG12D was induced by intratracheal intubation (i.t.) with adenovirus carrying Cre recombinase (Adeno-Cre). LSL, stop cassette flanked by 2 loxP (locus of recombination) sites. (B) 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 areas). (C) Quantification of the tumor burden in whole lungs isolated from K-RasG12D (4 mice/18 lobes) and c-JunAA/AA; K-RasG12D (3 mice/15 lobes) mice. Dots, individual lobes; red horizontal line, median. P values calculated using unpaired t test with Welch’s correction. (D) Violin plots quantifying the percentage of Ki67+ cells in lung tumors from mice of the indicated genotypes. K-RasG12D (3 mice/35 tumors) and c-JunAA/AA; K-RasG12D (3 mice/80 tumors). Each data point represents 1 tumor. Red horizontal line, median. P values calculated using unpaired t test with Welch’s correction. (E) 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). (F) Schematic summary: Blocking JNK phosphorylation of c-Jun increases oncogenic K-Ras–dependent lung tumor burden, similar to the effects of c-Jun deletion, possibly via increased phosphorylation of JunD.