Abstract 4742: Role of tumor-associated macrophages in esophageal cancer: PD-L1 expression and prognosis
Authors: Yagi Taisuke , Baba Yoshifumi , Koga Yuki , Uchihara Tomoyuki , Kiyozumi Yuki , Sawayama Hiroshi , Hiyoshi Yukiharu , Iwatsuki Masaaki , Miyamoto Yuji , Yoshida Naoya , Baba Hideo 
Published: August 2018

Introduction: It has become clear that macrophages are important cells forming cancer microenvironment and tumor-associated macrophages (TAM) promote their proliferation in various cancer types. In particularly, M2-type macrophages have been reported to promote the production of anti-inflammatory factors and the infiltration of regulatory T cells and suppress anti-tumor immunity, and new antitumor therapies that control tumor growth by controlling TAM have been proposed. In addition, "anti-PD-1 antibody" has attracted attention also in esophageal cancer, but the relationship between TAM and PD-L1 expression has not been clarified.

Methods: A retrospective study was performed on 301 patients who underwent esophagectomy for esophageal cancer between March 2005 and June 2013. We performed immunohistochemistry and evaluation of macrophage markers (CD163 and CD204) and PD-L1. In addition, we performed in vitro experiments to clarify the cellular malignancy and relationship with PD-L1 expression.

Results: Out of 301 cases of esophageal cancer, 156 cases showed CD163 high expression (51.8%) while 146 cases showed CD204 high expression (48.5%). We divided into three groups of TAM status based on CD204 and CD163 expression (CD163 and CD204 both positive: TAM status high (n=100), either one positive: moderate (n=102), both negative: low (n=99)). In TAM high group, there were more advanced cancers and adenocarcinoma cases (P&lt;0.0001, P=0.042, respectively). Interestingly, TAM status correlated with PD-L1 expression (P=0.0005). We found that there was a significant difference in overall survival, cancer specific survival and disease-free survival among these three groups (log rank P = 0.0062, P= 0.0012, P= 0.0006, respectively), and TAM status correlated with poor prognosis. We performed double immunostaining of PD-L1 and CD163, there is a part where PD-L1 is expressed around TAM, suggesting that the expression of PD-L1 and the presence of TAM are correlated. We performed co-culture of esophageal cancer cell lines (TE-8 and KYSE30) and activated macrophage. In real time PCR PD-L1 expression were elevated at co-culture with activated macrophage. Fluorescence activated cell sorting (FACS) revealed PD-L1 expression positive cells were increased at co-culture with activated macrophage. In invasion assay, when co-cultured with activated macrophages, the number of infiltrating cells were significantly increasing (P=0.00021). In timelapse imaging showed increased cell activity by co-culture with activated macrophage.

Conclusion: This study suggested that TAM correlated with poor prognosis in patients with esophageal cancer. In addition, TAM correlated with invasive capacity and migratory capacity. Importantly, TAM correlated PD-L1 expression in esophageal cancer cell lines.

Citation Format: Taisuke Yagi, Yoshifumi Baba, Yuki Koga, Tomoyuki Uchihara, Yuki Kiyozumi, Hiroshi Sawayama, Yukiharu Hiyoshi, Masaaki Iwatsuki, Yuji Miyamoto, Naoya Yoshida, Hideo Baba. Role of tumor-associated macrophages in esophageal cancer: PD-L1 expression and prognosis [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 4742.