Anoikis Induction and Inhibition of Peritoneal Metastasis of Pancreatic Cancer Cells by a Nuclear Factor-κB Inhibitor, (−)-DHMEQ

Abstract

The transcription factor nuclear factor-κB (NF-κB) plays a crucial role in pancreatic cancer (PC) progression. NF-κB is also involved in resistance to anoikis, a special type of apoptosis induced when cells are detached from the extracellular matrix or other cells. Anoikis resistance is related to the metastatic abilities of tumor cells; however, little is known about anoikis induction as it relates to inhibition of PC metastasis by NF-κB inhibitors. Here we used a specific NF-κB inhibitor, (-)-dehydroxymethylepoxyquinomicin (DHMEQ), to investigate anoikis induction and peritoneal metastasis suppression following NF-κB inhibition. We transduced Gluc, a secretory form of luciferase, into a PC cell line, AsPC-1 (AsPC-1-Gluc), for our in vivo experiments. (-)-DHMEQ induced anoikis in AsPC-1-Gluc cells as measured by cell survival assays and flow cytometry. The DNA-binding activity of p65 was enhanced immediately after cell detachment from culture dishes in ELISA assays. Some antiapoptotic proteins such as cellular inhibitor of apoptotic protein-1 were consequently upregulated on Western blots. (-)-DHMEQ prevented this increase in p65 activity and the subsequent expressions of antiapoptotic molecules. In a murine xenograft model, anoikis-resistant PC cell lines tended to metastasize to the peritoneum more than anoikis-sensitive cells, suggesting a correlation between anoikis sensitivity and peritoneal metastasis. (-)-DHMEQ successfully inhibited peritoneal metastasis of AsPC-1-Gluc cells. We monitored metastasis inhibition by ex vivo chemiluminescent detection of Gluc secreted from tumor cells into murine plasma and by in vivo imaging. Our results suggest that (-)-DHMEQ inhibited peritoneal dissemination by preventing anoikis resistance of PC cells.