A three-dimensional and temporo-spatial model to study invasiveness of cancer cells by heregulin and prostaglandin E₂¹

To study the temporal expression of motile structures and protease activity during colon cancer cell invasion by heregulin-β1 (HRG) and prostaglandin E2 (PGE₂), we have developed a three-dimensional spatial model system. HRG and PGE₂each induced the formation of well-organized, three-dimensional structures with empty spaces in the center and stimulated the expression of urokinase plasminogen activator (uPA) with differential localization of membrane-bound uPA at the focal adhesion points and leading edges of the motile cells. A specific cyclooxygenase-2 inhibitor blocked the formation of three-dimensional luminal glandular structures induced by HRG but did not block those induced by PGE₂A specific antagonist of uPA receptor completely blocked the formation of these luminal glandular structures induced by PGE₂and HRG. These findings suggest that HRG-mediated increased invasiveness of colon cancer cells is augmented at least in part by induction of PGE₂and uPA, and this augmentation may involve the formation of three-dimensional invasive structures via the uPA pathway. In addition, the three-dimensional model system presented here may have a wider application to screen the effects of therapeutic compounds and biomolecules on different spatial aspects of colonic biology, including cell growth, motility, invasion, survival, and apoptosis.