Targeted inactivation of Runx3 in mouse lung induced mucinous and nonmucinous adenomas and markedly shortened latency of adenocarcinoma formation induced by oncogenic K-Ras. RUNX3 was frequently inactivated in K-RAS mutated human lung adenocarcinomas. A functional genetic screen of a fly mutant library and molecular analysis in cultured cell lines revealed that Runx3 forms a complex with BRD2 in a K-Ras dependent manner in the early phase of the cell cycle; this complex induces expression of p14ARF/p19Arf and p21WAF/CIP. When K-Ras was constitutively activated, the Runx3-BRD2 complex was stably maintained and expression of both p14ARF and p21WAF/CIP was prolonged. These results provide a missing link between oncogenic K-Ras and the p14ARF-p53 pathway, and may explain how cells defend against oncogenic K-Ras.
Significance of discovery
Oncogenic K-Ras induces lung adenocarcinoma, and the p14ARF-p53 pathway antagonizes this process. However, it is not known how the p14ARF-p53 pathway is activated by oncogenic K-Ras, or why p53 inhibits malignant adenocarcinoma formation but not adenoma formation. Thus, our knowledge of tumor suppression at the early stage of tumor development is incomplete. Our results show that, in mice, Runx3 inhibits adenoma formation and contributes to the activation of the p14ARF-p53 pathway in a K-Ras-dependent manner. Restoration of RUNX3 in K-RAS-mutated human non-small-cell lung cancer cell line activated the p14ARF-p53 pathway, ultimately leading to apoptosis. Our results fill the gap in current knowledge regarding how cells are protected from forming adenomas at the very early stages of that process.
SP-C+/CC10+ cells differentiate to SP-C+ adenoma cells
Double immunofluorescence staining of Adeno-Cre-infected Runx3f/f/K-RasLSL-G12D mouse lung at 4 months post-infection. Red indicates CC10-positive cells while green indicates SP-C-positive cells. Strong SP-C+/CC10+ double positive cells were generated in bronchiolar epithelium and associated with papillary structures (see bright orange staining on the left). The cells gradually differentiated into SP-C single positive cells and formed lung adenocarcinoma (see graduated decrease of orange intensity and increase of green staining from left to right).
You-Soub Lee,1,7 Jung-Won Lee,1,7 Ju-Won Jang,1,7 Xin-Zi Chi,1,7 Jang-Hyun Kim,1 Ying-Hui Li,1 Min-Kyu Kim,1 Da-Mi Kim,1 Byeung-Sub Choi,1 Eung-Gook Kim,1 Jin-Haeng Chung,2 Ok-Jun Lee,3 You-Mie Lee,4 Joo-Won Suh,5 Linda Shyue Huey Chuang,6 Yoshiaki Ito,6,* and Suk-Chul Bae1,*
1Department of Biochemistry, College of Medicine, Chungbuk National University, Cheongju 361-763, South Korea
2Department of Pathology, Bundang Hospital, Seoul National University College of Medicine, 103 Daehakro, Jongno-gu, Seoul 110-799, South Korea
3Department of Pathology, College of Medicine, Chungbuk National University, Cheongju 361-763, South Korea
4Department of Natural Sciences, School of Life Sciences and Biotechnology, Kyungpook National University, Daegu 702-701, South Korea
5Division of Bioscience and Bioinformatics, Myongji University, Yoingin-si 449-728, South Korea
6Cancer Science Institute of Singapore, National University of Singapore, Center for Translational Medicine, 14 Medical Drive, Singapore 117599, Singapore
7These authors contributed equally to this work
*Correspondence: csiitoy[at]nus.edu.sg (Y.I.), scbae[at]chungbuk.ac.kr (S.-C.B.)