Targeted silencing of SOX2 by an artificial transcription factor showed antitumor effect in lung and esophageal squamous cell carcinoma

// Etsuko Yokota 1 , Tomoki Yamatsuji 1 , Munenori Takaoka 1 , Minoru Haisa 1 , Nagio Takigawa 2 , Noriko Miyake 3 , Tomoko Ikeda 3 , Tomoaki Mori 4 , Serika Ohno 4 , Takashi Sera 4 , Takuya Fukazawa 1 and Yoshio Naomoto 1 1 Department of General Surgery, Kawasaki Medical School, Okayama, 700-8505, Japan 2 Department of General Internal Medicine 4, Kawasaki Medical School, Okayama, 700-8505, Japan 3 General Medical Center Research Unit, Kawasaki Medical School, Okayama, 700-8505, Japan 4 Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Okayama University, Okayama, 700-8530, Japan Correspondence to: Takuya Fukazawa, email: fukazawat@aol.com Takashi Sera, email: sera@cc.okayama-u.ac.jp Keywords: artificial transcription factor (ATF), SOX2, squamous cell carcinoma, molecular targeted therapy Received: July 05, 2017      Accepted: September 20, 2017      Published: October 05, 2017 ABSTRACT SOX2 is a transcription factor essential for early mammalian development and for the maintenance of stem cells. Recently, SOX2 was identified as a lineage specific oncogene, recurrently amplified and activated in lung and esophageal squamous cell carcinoma (SCC). In this study, we have developed a zinc finger-based artificial transcription factor (ATF) to selectively suppress SOX2 expression in cancer cells and termed the system ATF/ SOX2 . We engineered the ATF using six zinc finger arrays designed to target a 19 bp site in the SOX2 distal promoter and a KOX transcriptional repressor domain. A recombinant adenoviral vector Ad-ATF/ SOX2 that expresses ATF/ SOX2 suppressed SOX2 at the mRNA and protein levels in lung and esophageal SCC cells expressing SOX2. In these kinds of cells, Ad-ATF/ SOX2 decreased cell proliferation and colony formation more effectively than the recombinant adenoviral vector Ad-sh SOX2 , which expresses SOX2 short hairpin RNA (sh SOX2 ). Ad-ATF/ SOX2 induced the cell cycle inhibitor CDKN1A more strongly than Ad-sh SOX2 . Importantly, the ATF did not suppress the cell viability of normal human cells. Moreover, Ad-ATF/ SOX2 effectively inhibited tumor growth in a lung SCC xenograft mouse model. These results indicate that ATF/ SOX2 would lead to the development of an effective molecular-targeted therapy for lung and esophageal SCC.