Introduction: Despite recent advances in targeted and immune-based therapies, the poor prognosis of lung adenocarcinoma (LUAD) with bone metastasis (BM) remains a challenge. Here, we aimed to investigate the potential biomarker for LUAD with BM.
Methods: First, we collected 5 patients with traumatic amputation, 5 patients with bone infiltration, 9 LUAD patients who underwent curative resection or thoracoscopic lobectomy and 32 LUAD patients with BM who underwent bone biopsy in the Shanghai Sixth People's Hospital (China) from May 2014 to January 2017. 28 bone biopsy samples and 9 LUAD samples were used for immunohistochemistry assays (IHC) and OS (follow-up period of more than one year). Secondly, RT-PCR, IHC, and Western blotting (WB) were used to assess Aldehyde Dehydrogenase 2 (ALDH2) RNA and protein expression levels in samples of LUAD with BM. The Cancer Genome Atlas (TCGA) and Kaplan Meier plotter (KM Plotter) were used to generate survival curves. Thirdly, we analyzed the methylation associated genes and found DNA Methyltransferase 1 (DNMT1) and methyl-CpG binding domain 4 (MBD4) down-regulated the expression of ALDH2. Fourthly, we explored the impact of ALDH2 on tumor cell function and apoptosis via cell counting kit-8 (CCK8), Transwell and Fluorescence activated cell sorter (FACS). Then, we demonstrated that ALDH2 might affect mitogen-activated protein kinase (MAPK) and Epithelial-mesenchymal transition (EMT) markers through WB assays. Last, to confirm ALDH2 effect in vivo, we injected PLVX-flag-aldh2 and PLVX-flag H1299 cells into the left cardiac ventricle to check the effect of ALDH2 in BM and calculated the overall survival of mice.
Results: We identified both mRNA and protein levels of ALDH2 were much lower in tumor tissues than in normal tissues, and they were even lower in tissues that exhibited increased migratory capacity. This low expression feature may be attributed to DNA methylation of ALDH2.The result of over expressing or knocking down ALDH2 showed that this gene inhibited proliferation, migration and promoted apoptosis both in vivo and in vitro. Overexpression of ALDH2 can inhibit MAPK signaling pathway and EMT in H1299. It also inhibited the occurrence of BM in LUAD and expanded survival in mice (p=0.003).
Conclusions: This is the first time that instance where ALDH2 was associated with disease severity and progression in LUAD patients with BM. Thus, with this study, we have identified potential biomarkers and therapeutic targets for this disease. Supported by the National Natural Science Foundation of China (grant No. 81672852,81602519), a three year action plan to promote clinical skills and clinical innovation in municipal hospitals (20164Y0099), Shanghai Municipal Education Commission—Gaofeng Clinical Medicine Grant Support (20172024).
Citation Format: Mengdi Yang, Guangyu Yao, Zhiyu Wang, Jing Sun, Yiyi Zhou, Yifeng Gu, Hui Zhao. The differential expression of ALDH2 is correlated with prognosis of lungadenocarcinoma with bone metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-319.