Abstract 2096: HIF-1α is a crucial factor in the development of peritoneal dissemination via natural metastatic routes in scirrhous gastric cancer

Abstract

Abstract Background The molecular mechanisms of peritoneal dissemination in gastric cancer still remain unclear. This study was designed to clarify the role of HIF-1α in the development of peritoneal dissemination of gastric cancer. Methods HIF-1α knockdown (KD) cells were established in the scirrhous gastric cancer cell line 58As9 by siRNA transfection. In western blot analysis, HIF-1α expression was assessed using KD and the control transfectant (SC) cells under normoxia (20%O2) as well as hypoxia (1%O2). A series of in vitro analysis were conducted and compared between the 2 transfectants. Using nude mice, peritoneal dissemination was evaluated by orthotopic implantation (o.i.) and intraperitoneal injection (i.p.) models. Finally, tumor angiogenesis of venous and lymph vessels was immunohistochemically analyzed. Results Deficient HIF-1α expression was observed in KD, but not SC cells under normoxia and hypoxia. In vitro proliferation and invasion was significantly reduced in KD compared with SC cells. On contrary, HIF-1α exerts unfavorable effects on anoikis resistance and adhesion ability. In o.i. model, stomach tumor was highly developed in both of KD (86.7%) and SC mice(100%). On the other hand, peritoneal dissemination was more frequently observed in the SC mice (93%) than in the KD mice (13%) (p < 0.001). In the i.p. model, the dissemination highly occurred in both mice (each 100%), while greater number of nodules was observed in the KD mice (p = 0.017). Angiogenesis with vascular invasion were more highly developed in the SC stomach tumors (venous vessels: p=0.001, lymph vessels: p=0.043). In the disseminated nodules, the vascular invasion was developed at intratumoral regions in the SC o.i. mice, however such appearance was not found in i.p. mice. Conclusions This study clearly showed that HIF-1α is crucial for the development of peritoneal dissemination in the spontaneous metastatic (o.i.) model. Moreover, in i.p. model, larger number of dissemination was found in KD than SC mice, indicating that the dissemination by o.i. would not be developed via seeding mechanism. Analysis of tumor angiogenesis in o.i. model demonstrated that HIF-1α activated venous as well as lymph angiogenesis in the stomach tumor. In peritoneal disseminated nodules, vascular invasion was observed at intratumoral area in o.i. SC mice, but not in the i.p. mice. This unique feature further suggests that the dissemination in o.i. mice might be developed by extravasation of cancer cells, which are micro-connected to the stomach tumor via trans-vessel route. Citation Format: Shuusuke Miyake, Yoshihiko Kitajima, Jun Nakamura, Keita Kai, Kazuyoshi Yanagihara, Tomokazu Tanaka, Masatsugu Hiraki, Kohji Miyazaki, Hirokazu Noshiro. HIF-1α is a crucial factor in the development of peritoneal dissemination via natural metastatic routes in scirrhous gastric cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2096. doi:10.1158/1538-7445.AM2014-2096