Background: Esophageal cancer has been reported to express HER family, especially EGFR and HER2, of which expressed cases have been reported to show poor prognosis. However, although there are some clinical trials that target those markers, using cetuximab (Cet), panitumumab (Pan), and trasutuzumab (Tra), the result is not sufficient. On the other hand, cancer-associated fibroblasts (CAFs) are one of the major components of tumor microenvironment and suggested to be associated with those chemoprevention, leading to poor prognosis. Thus, to target both cancer cells and CAFs, we focused on near-infrared photoimmunotherapy (NIR-PIT). NIR-PIT is a new molecular targeted therapy, which is based on a near-infrared (NIR) photosensitizer IR700, conjugated to monoclonal antibody (mAb) targeting particular molecules. We developed the CAFs-targeting PIT targeted on fibroblast activated protein (FAP) and have confirmed the efficacy to FAP-expressed CAFs. In this study, we hypothesized that the effect of cancer-targeting PIT is decreased under CAF-rich condition as like other antibody-based therapy. Here we firstly evaluated the effect of cancer-targeting PIT in esophageal cancer cells and furthermore the possibility of additional effect by “dual-targeting PIT” for CAFs and cancer cells.

Materials and Methods: Human esophageal cancer cell lines and human esophageal fibroblasts (FEF3) were used in this study. FEF3 stimulated with conditioned medium (CM) of cancer cells defined as CAFs. We used cetuximab and panitumumab for anti-EGFR antibody and trastuzumab for anti-HER2 antibody. The expression of EGFR, HER2 in esophageal cancer cells was confirmed by Western blot (WB). Cell viability for quantitative evaluation was determined using an XTT Cell Proliferation Kit II.

Result: WB demonstrated that HER2 expression was increased in TE4 and OE19, and EGFR was increased in TE8. FEF3 stimulated with CM was increased FAP expression compared with control. XTT assay demonstrated that the effect of cancer-targeting PIT using Pan-IR700, Tra-IR700 is efficient. Additionally, we confirmed that CAFs-targeting PIT worked in co-culture condition with cancer cells as well as monoculture condition. Furthermore, “dual-targeting PIT” showed rapid cell death of both in co-culture condition, and XTT assay showed the additive effects in vitro, as expected.

Discussion: In this study, dual-targeting therapy has shown cellular specific cell death by targeting to cell-specific antigen and induced both cells death simultaneously. NIR-PIT can be novel effective therapy for esophageal cancer, and also for CAFs in tumor microenvironment. Thus, “dual-targeting PIT," which is combined with both mAb-IR700 for cancer cells and CAFs, can regulate tumor stroma as well as cancer cells simultaneously and can be highly expected to have strong antitumor effect by remodeling tumor microenvironment.

Citation Format: Hiroaki Sato, Kazuhiro Noma, Toru Narusaka, Satoshi Komoto, Yuki Katsura, Takuya Kato, Takayuki Ninomiya, Toshiaki Ohara, Hiroshi Tazawa, Yasuhiro Shirakawa, Hisataka Kobayashi, Toshiyoshi Fujiwara. Dual-targeting photoimmunotherapy (NIR-PIT) for esophageal cancer cells and cancer-associated fibroblasts (CAFs) [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 5066.