Abstract 5176: Cell free malignant ascites fluid facilitates gastric adenocarcinoma peritoneal metastasis

Abstract

Abstract Gastric adenocarcinoma is the fastest rising malignancy in North America. It is commonly associated with malignant ascites (MA), the pathological accumulation of fluid containing cancer cells in the peritoneum. Peritoneal metastasis is the most common site of gastric cancer (GC) progression after curative intent surgery and is the leading cause of death. Upon peritoneal dissemination, the malignant process is deemed non-curative as it is rarely amenable to surgical resection and chemotherapeutic regimens are simply palliative. We hypothesize that cell-free MA increases the potential of GC cells to worsen peritoneal metastasis. Gastric adenocarcinoma cell lines (human: MKN-45, SNU-5, KATO III, OKAJIMA; murine NCC-S1, NCC-S1M) were incubated with cell-free MA and their metastatic ability assessed with static in vitro adhesion assays, as well as migration assays. A novel ex vivo peritoneal metastasis model further corroborated the in vitro results, where cancer cell adhesion to stripped human peritoneum was assessed by co-incubation with non- and pre-stimulated cancer cells. Gross liver metastasis was monitored over several weeks after in vivo intra-peritoneal and intra-splenic injections, whereby C57BL/6 mice were inoculated with control media or stimulated NCC-S1M cells. Incubation of human GC cells and/or human peritoneal mesothelial cells (HPMC) with cell-free MA resulted in a significant three to five-fold increase of GC cell adhesion to HPMC compared to non-stimulated condition (P<0.05), as measured by inverted fluorescent microscopy. In addition, the murine GC cells incubated with MA showed a significant eight-fold increase on average (P<0.05) in GC cell adhesion to HPMC compared to non-stimulated condition. Cell-free MA was shown to significantly enhance ex vivo SNU-5 cell adhesion to stripped human peritoneum by a two to four-fold increase (P<0.05) compared to non-stimulated condition. Liver metastases were visible in mice that received in vivo injections of ascites-stimulated NCC-S1M cancer cells by day 25, yet not in mice inoculated with control media. Several factors (ANG-2, HGF, ICAM-1, IL-8, TIMP-2, uPAR, VEGF, NAP-2, MIF) were shown to be upregulated in MA samples compared to a cirrhotic ascites control, using a multiplex ELISA. In particular, VEGF was upregulated 11 to 25-fold, and MIF two to 12-fold. The results demonstrated that MA plays a significant role in facilitating GC cell adhesion to peritoneal mesothelia, an important early step in the peritoneal metastatic cascade. MA must therefore provide an environment that supports tumour growth and spread. A more comprehensive understanding of the molecular network is essential to determine the role of cell free MA fluid in GC progression, allowing for the identification of potential therapeutic targets for this aggressive malignancy. Citation Format: Chantelle A. Janeiro, Vivian Stavrakos, Malak Alzahrani, Roni F. Rayes, France Bourdeau, Betty Giannias, Nicholas Bertos, Veena Sangwan, Jonathan Cools-Lartigue, Jonathan D. Spicer, Lorenzo E. Ferri. Cell free malignant ascites fluid facilitates gastric adenocarcinoma peritoneal metastasis [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 5176.