Abstract 4064: 3D gel system to study tumor metastasis and EMT
Authors: Fang Josephine Y. , Tan ShiJye , Yang Zhi , Nimni Marcel , Han Bo 
Published: May 2015

Abstract
Carcinoma invasion and metastasis is under intensive investigation. Even though long been depicted as tumor cell autonomous phenotype due to gene mutation, recent studies point out that metastatic potential are acquired through exposure of epithelial cancer cells to the tumor microenvironment, triggered by paracrine signals, environmental stimuli and ECM topologies. It is always a technical hurdle to replicate in vivo environment with proper scaffolds and tailorable mechanical properties. In our newly developed 3D Col-Tgel, scaffolding's stiffness can be controlled by collagen peptide concentration and crosslinking density. Tumor cell metastasis and EMT-MET switches were studied. Three cell types, MDA-MD-231 (breast cancer), HCT116 (colon cancer), and CFPAC (pancreatic cancer) were cultured in Col-Tgel in the range of 50-1000 pka. Tumor cells in Col-Tgel showed cell type specific responses to 3D gel rigidity, with changes in morphology, proliferation rate, and resistance to drugs. At different depths from the surface, cells adapted different morphologies to reflect their different nutritional states and matrix topology. For a prolonged culture (&gt; 6day), cell migration was observed out of the at the edge the gel in the selected gel conditions for specific cell type. As expected, the cells migrated out of the gel were positively stained for vimentin. Surprisingly, a belt of cells located around 200-500um from the edge of the gel were also positive for vimentin, suggesting that tumor cell activation for migration or invasion is more likely environmental dependent than their own gene feature (stemness). Next, migrated cells were harvested by a scrapper and reseeded back into the 3D Col-Tgel. The originally vimentin positive cells uniformly lost the vimentin expression in 3D gel condition in the first day 6. After then, cells in the gel start to migrate as in the previous cycle, suggesting that these cells are flexible to re-differentiated back to epithelial cell phenotype (MET). HIF-1α positive zone overlapped vimenting positive staining zone, indicating hypoxia induced by local environment may be a driving force for EMT. Time-lapsed images were taken showing majority of cells migrated out the matrix by squeezing through the gel (pathway finding) instead of crawling. From migration time (30 min period) and distance, we speculate that cell migration is integrin independent. Tumor EMT is now thought to play a fundamental role in tumor progression and metastasis. Clinical EMT markers always correlate adversely to the prognostic outcomes. However, the origins of these cells are under debate questioning whether malignant migratory cells are cancer stem cells or somatic tumor cells. This study directly proof of the cell fate in well controlled environments. This system may provide a toolbox to study EMT and test therapeutic options.
Citation Format: Josephine Y. Fang, ShiJye Tan, Zhi Yang, Marcel Nimni, Bo Han. 3D gel system to study tumor metastasis and EMT. [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 4064. doi:10.1158/1538-7445.AM2014-4064