The loss-of-function of DNA methyltransferase 1 by siRNA impairs the growth of non-small cell lung cancer with alleviated side effects via reactivation of RASSF1A and APC in vitro and vivo

// Qi Lai 1, * , Yin-Hui Xu 2, * , Qiang Chen 2, * , Liang Tang 2 , An-Gui Li 3 , Li-Fei Zhang 2 , Chun-Fang Zhang 1 , Jian-Fei Song 2 and Zhen-Zong Du 4 1 Department of Thoracic Surgery, Xiangya Hospital of Central South University, Changsha 410008, P.R. China 2 Department of Thoracic Surgery, The Second Affiliated Hospital of Guilin Medical University, Guilin 541199, P.R. China 3 Department of Thoracic Surgery, The Affiliated Hospital of Guilin Medical University, Guilin 541001, P.R. China 4 Department of Thoracic Surgery, Nanxi Shan Hospital of Guangxi Zhuang Autonomous Region, The Affiliated Nanxi Shan Hospital of Guilin Medical University, Guilin 541002, P.R. China * The authors have contributed equally to this work Correspondence to: Zhen-Zong Du, email: duzhenzong@sina.com Jian-Fei Song, email: guilinsjf@163.com Keywords: DNMT1, 5-Aza-CR, siRNA, lung cancer, side effects Received: November 04, 2016     Accepted: June 02, 2017     Published: July 26, 2017 ABSTRACT Hypermethylation of tumor suppressor genes (TSGs) promoters by DNA methyltransferase (DNMT) can be observed in almost all cancers which represent a hallmark of carcinogenesis, including lung cancer. DNMT inhibitors (e.g.5-Aza-CR/CdR) reactivate TSGs to exert anti-cancer activity and have been applied into the clinical. However, it is cytotoxic even at low concentrations, which might be not directly related to DNA methylation. We here investigated an alternative strategy in the lung cancer therapy and aimed to estimate and compare its efficiency and side effects of knockdown of DNMT1 in vitro and in vivo . Lung cancer tissues (n=20) showed enhanced expression of DNMT1 than corresponding non-neoplastic tissues. Similar results were found in lung cancer cell lines A549 and H538. The treatment of 5-Aza-CR or knockdown of DNMT1 in vitro could inhibit the expressions of DNMT1 but restore the TSGs expressions including the Ras association domain family 1A (RASSF1A) and the adenomatous polyposis coli (APC) via the demethylation of its promoter region, which results in the decreased proliferation, increased apoptosis and impaired ability of migration. Importantly, knockdown of DNMT1 by siRNA in vivo also effectively demethylated the RASSF1A and APC promoter, elevated their expressions and limited tumor growth, which functioned like 5-Aza-CR but with alleviated side effects, suggesting that knockdown of DNMT1 might be potential strategy for the treatment of lung cancer with better tolerability.