Background: IL-8, a pro-inflammatory cytokine, and its receptor, CXCR2, are expressed in various cancer cells. The IL-8/CXCR2 network is believed to be involved in angiogenesis, tumor cell proliferation and invasion. However, its role in esophageal squamous cell carcinoma (ESCC) remains unclear. In this study, we investigated the role of the IL-8/CXCR2 network in the tumor microenvironment of ESCC. Methods: CXCR2 expression was investigated immunohistochemically in 82 primary ESCCs with R0 resection but without any preoperative treatment. We evaluated the intensity of the staining in four grades; grades 3 (strong) and 2 (medium) were deemed “positive”, and 1 (weak) and 0 (negative) as “negative”. The concentration of IL-8 and CXCR2 were investigated using the human ESCC cell lines TE1, 4, 5, 6, 8, 9, 10, 11, 14 and 15. IL-8/CXCR2 signaling was stimulated by IL-8 addition, and suppressed by SB225002 (Cayman Chemical) treatment, a selective antagonist of CXCR2. Stable IL-8 over-expressing TE4 cells were established, and cell proliferation assays were performed. To evaluate tumor growth in vivo, we subcutaneously inoculated 1.0×106 TE4 cells or transfectant into nude mice, and half of the transfectant-inoculated mice received 1mg/kg of SB225002 by intraperitoneal injection thrice weekly. The size and incidence of subcutaneous tumors were recorded.

Result: Thirty-two (38.6%) patients were positive for CXCR2 immunostaining and 50 (61.4%) patients were negative. CXCR2 expression was related to poor survival in ESCC patients (P = 0.063). IL-8 concentration was high in TE4, 5, 10 and 14 supernatant, and low in that of TE1, 6, 8, 9, 11 and 15. CXCR2 expression was high in TE1, 4, 5, and 14 cells, and low in TE6, 8, 9, 10, 11 and 15. We chose TE1 and TE4 cells for further investigation. Stimulation or inhibition of the IL-8/CXCR2 network resulted in significant enhancement or suppression of cell proliferation in both cell lines (P<0.05) in a dose-dependent manner. IL-8 over-expressing TE4 cells showed significantly higher proliferative activity than the parental line (P<0.05), which was markedly suppressed by inhibition of the IL-8/CXCR2 network using SB225002 (P<0.05). In vivo, tumor sizes were smaller in the SB225002-treated group than in the untreated group.

Conclusion: Our results demonstrated that stimulation of the IL-8/CXCR2 network clearly enhanced ESCC cell proliferation, while its inhibition obviously suppressed ESCC cell proliferation in vitro. These results indicate that control of IL-8/CXCR2 network signaling may be a new therapeutic strategy for ESCC.

Citation Format: Masazumi Inoue, Hiroya Takeuchi, Sachiko Matsuda, Tomohiko Nishi, Kazumasa Fukuda, Rieko Nakamura, Tsunehiro Takahashi, Norihito Wada, Hirofumi Kawakubo, Yoshiro Saikawa, Yuko Kitagawa. Role of IL-8/CXCR2 network in the tumor microenvironment of esophageal squamous cell carcinoma. [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 433. doi:10.1158/1538-7445.AM2015-433