Abstract 4946: Novel photoimmunotherapy (PIT) targeting cancer-associated fibroblasts (CAFs) for esophageal cancer.
Authors: Watanabe Shinichiro , Noma Kazuhiro , Urano Shinichi , Ohara Toshiaki , Hashimoto Yuuri , Tazawa Hiroshi , Fujiwara Toshiyoshi 
Published: August 2014

Introduction: CAFs are thought to play an essential role in cancer invasion and metastasis. We have developed the novel therapy targeting CAFs. Originally, CAFs have been defined as fibroblasts which express α-SMA in cancer tissue. As α-SMA express in cytoplasm, it can't become the target by itself. However recently it was reported that fibroblast activation protein (FAP) is functional and specific surface protein for CAFs. The aim of this study is to analyze CAFs and FAP expression of esophageal cancer and to develop the new therapy that targeted CAFs by PIT for esophageal cancer. Here we suggest a novel method of an antitumor effect by killing CAF itself.

Matherials and Methods: TE-4 and TE-8 (esophageal squamous cell carcinoma), FEF3 (fetal esophageal fibroblast 3),GEP-FEF3 cell lines were used in this study. 1) The specimens of esophageal cancer were double immunostained with α-SMA and FSP1 antibodies to count CAFs. 2) In vivo study, TE cells and TE cells+activated FEF3 in the two groups were compared with tumor progression. 3) The interaction of activated FEF3 and TE cells was examined about the expression of α-SMA and FAP by western blotting and flowcytometry. 4) We examined the surface expression of FAP in activated FEF3 by immunohistochemistory(IHC). 5) We used a target-specific photosensitizer based on a near-infrared(NIR) phthalocyanine dye, IR700, conjugated to monoclonal antibodies targeting FAP. In vitro and in vivo, we observed whether cell proliferation and tumorigenicity are controlled after irradiation with NIR light in FEF3 expressing FAP conjugated FAP-IR700.

Results: 1) The expression of CAFs was recognized as a deeper invasion depth, moreover the CAFs has tended to express more in the periphery and the leading parts. 2) In vivo, the tumors co-injected TE cells and CAFs tended to grow more than cancer cell alone. 3) In western blotting, FAP expression of FEF3 activated by TGF-β and co-cultured with TE cells was detected more than that of normal status.In flowcytometry, FAP expression of FEF3 activated by TGF-β, co-cultured with TE cells and cultured in TE cells conditioned medium was detected more than that of normal status. 4) In IHC, FAP expression of FEF3 activated by TGF-β and co-cultured with TE cells was increased more than that of normal status.5.We could suppress the proliferation of activated FEF3 cells in vitro with FAP-IR700 mediated PIT. And in vivo, the tumor with FAP-IR700 was also suppressed.

Conclusion: In conclusion, we demonstrate that CAF contributed to tumor invasion and progression in surgical specimens and it was represented in vivo, which indicated that CAF is essential for cancer development. Furthermore, here we suggest novel therapeutic concept of “Targeting CAF by PIT” for cancer progression. The PIT for CAF is a unique strategy and can bring us a new type theory as combination targeting cancer cells and their fundamental microenvironment.

Citation Format: Shinichiro Watanabe, Kazuhiro Noma, Shinichi Urano, Toshiaki Ohara, Yuuri Hashimoto, Hiroshi Tazawa, Toshiyoshi Fujiwara. Novel photoimmunotherapy (PIT) targeting cancer-associated fibroblasts (CAFs) for esophageal cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4946. doi:10.1158/1538-7445.AM2013-4946