Abstract 290: In situ delivery and production of anti-HER2 scFv
Authors: Kikuchi Takeshi , Shimizu Hitomi , Akiyama Yasuto , Taniguchi Shun'ichiro 
Published: August 2015

Introduction: Trastuzumab, a monoclonal antibody targeting human epidermal growth factor receptor-2 (HER2), has become the main therapeutics for HER2-positive breast cancers. Recently, active scFvs (single-chain variable fragment) were produced and anti-tumor function like BITE (Bi-specific T cell engagers) has been added to improve the antitumor efficacy. On the one hand, the in situ delivery and continuous production of anti-cancer drugs at the tumor site will be required to evade adverse effects and elevate the dose of anti-cancer drugs in tumor tissues. We have established such in situ Delivery and continuous Production System (iDPS) with Bifidobacterium that can selectively target hypoxic microenvironment of solid cancer tissues. The purpose of the present study is to establish continuous production and secretion system for biologically active anti-HER2 scFv by Bifidobacterium.

Materials and Methods: We constructed an expression vector of anti-HER2 scFv based on the cDNA sequence of anti-HER2 antibody for E. coli. The biological activity of the product was examined by ELISA, FACS, fluorescence-immunostaining and MTT assay for cell growth using differentially HER2-expressing human cell lines. Anti-tumor activity was assessed by intratumoral injection with the anti-HER2 scFv for tumors of a human breast cancer cell line transplanted into nude mice. We further modified the above vector for E. coli. to make a shuttle vector for Bifidobacterium. The binding activity of the product to HER2 was confirmed by ELISA and the primary structure was examined by LC-MS.

Results: First, we succeeded in producing the recombinant scFv by E. coli, which showed specific binding to HER2. The anti-HER2 scFv inhibited the in vitro growth of several HER2-positive human cancer cell lines with the same efficiency as Trastuzumab. The intratumoral injection of the recombinant anti-HER2 scFv to transplanted human breast cancer tissues in nude mice showed a significant inhibition of the tumor growth. Next, to prepare iDPS of anti-HER2 scFv, we developed a recombinant Bifidobacterium longum to express and secrete anti-HER2 scFv, which was shown to bind to HER2 by ELISA, and its primary structure was confirmed to be the same as the recombinant anti-HER2 scFv produced by E. coli.

Conclusion: We believe that iDPS for anti-cancer substances like anti-HER2 scFv can contribute to the reduction of adverse effects and a better-cost performance than current antibody medicines. Importantly, the upcoming study to modify anti-HER2 scFv to carry BITEs-like activity will be planned, which can provide much more therapeutic effects for not only breast cancers but also other cancers expressing HER2.

Citation Format: Takeshi Kikuchi, Hitomi Shimizu, Yasuto Akiyama, Shun'ichiro Taniguchi. In situ delivery and production of anti-HER2 scFv. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 290. doi:10.1158/1538-7445.AM2015-290