DNA methylation maintains the CLDN1-EPHB6-SLUG axis to enhance chemotherapeutic efficacy and inhibit lung cancer progression

• Published in: Theranostics Vol. 10; no. 19; pp. 8903 - 8923
• Main Authors: Wu, Jia-En, Wu, Yi-Ying, Tung, Chia-Hao, Tsai, Yao-Tsung, Chen, Hsuan-Yu, Chen, Yuh-Ling, Hong, Tse-Ming
• Format: Journal Article
• Language: English
• Published: Australia Ivyspring International Publisher Pty Ltd 01.01.2020; Ivyspring International Publisher
• Subjects: A549 Cells; Adenocarcinoma of Lung - drug therapy; Adenocarcinoma of Lung - genetics; Adenocarcinoma of Lung - metabolism; Animals; Antibodies; Cell adhesion & migration; Cell Line, Tumor; Cell Movement - drug effects; Cell Proliferation - drug effects; Chemotherapy; Cisplatin - pharmacology; Claudin-1 - genetics; Cloning; DNA Methylation; Drug resistance; Drug Resistance, Neoplasm - drug effects; Drug Synergism; Enzymes; Epigenetics; Fibroblasts; Gene Expression Regulation, Neoplastic - drug effects; Genotype & phenotype; Growth factors; Humans; Hydroxamic Acids - pharmacology; Lung cancer; Lung Neoplasms - drug therapy; Lung Neoplasms - genetics; Lung Neoplasms - metabolism; Medical prognosis; Metastasis; Mice; Penicillin; Plasmids; Proteins; Receptors, Eph Family - metabolism; Research Paper; Sequence Analysis, DNA; Snail Family Transcription Factors - metabolism; Software; Tumor Microenvironment; Tumors; Vorinostat - pharmacology; Xenograft Model Antitumor Assays; United States > US; DNA methylation; cancer stem-like cells; drug resistance; metastasis; CLDN1
• ISSN: 1838-7640; 1838-7640
• DOI: 10.7150/thno.45785

The loss of cancer-cell junctions and escape from the primary-tumor microenvironment are hallmarks of metastasis. A tight-junction protein, Claudin 1 (CLDN1), is a metastasis suppressor in lung adenocarcinoma. However, as a metastasis suppressor, the underlying molecular mechanisms of CLDN1 has not been well studied. The signaling pathway regulated by CLDN1 was analyzed by Metacore software and validated by immunoblots. The effect of the CLDN1-EPHB6-ERK-SLUG axis on the formation of cancer stem-like cells, drug resistance and metastasis were evaluated by sphere assay, aldefluor assay, flow cytometry, migration assay, cytotoxicity, soft agar assay, immunoprecipitation assay and xenograft experiments. Furthermore, the methylation-specific PCR, pyrosequencing assay, chromatin immunoprecipitation and reporter assay were used to study the epigenetic and RUNX3-mediated transcription. Finally, the molecular signatures of RUNX3/CLDN1/SLUG were used to evaluate the correlation with overall survival by using gene expression omnibus (GEO) data. : We demonstrated that CLDN1 repressed cancer progression via a feedback loop of the CLDN1-EPHB6-ERK1/2-SLUG axis, which repressed metastasis, drug resistance, and cancer stemness, indicating that CLDN1 acts as a metastasis suppressor. CLDN1 upregulated the cellular level of EPHB6 and enhanced its activation, resulting in suppression of ERK1/2 signaling. Interestingly, DNA hypermethylation of the promoter abrogated SLUG-mediated suppression of in low-metastatic cancer cells. In contrast, the histone deacetylase inhibitor trichostatin A or vorinostat facilitated expression in high-metastatic cancer cells and thus increased the efficacy of chemotherapy. Combined treatment with cisplatin and trichostatin A or vorinostat had a synergistic effect on cancer-cell death. This study revealed that DNA methylation maintains CLDN1 expression and then represses lung cancer progression via the CLDN1-EPHB6-ERK1/2-SLUG axis. Because CLDN1 enhances the efficacy of chemotherapy, CLDN1 is not only a prognostic marker but a predictive marker for lung adenocarcinoma patients who are good candidates for chemotherapy. Forced CLDN1 expression in low CLDN1-expressing lung adenocarcinoma will increase the chemotherapy response, providing a novel therapeutic strategy.