Migration and vascular lumen formation of endothelial cells in cancer cell spheroids of various sizes

We developed a microfluidic device to culture cellular spheroids of controlled sizes and suitable for live cell imaging by selective plane illumination microscopy (SPIM). We cocultured human umbilical vein endothelial cells (HUVECs) within the spheroids formed by hepatocellular carcinoma cells, and studied the distributions of the HUVECs over time. We observed that the migration of HUVECs depended on the size of spheroids. In the spheroids of similar to 200 mu m diameters, HUVECs migrated outwards to the edges within 48 h; while in the spheroids of similar to 250 mu m diameters, there was no outward migration of the HUVECs up to 72 h. In addition, we studied the effects of pro-angiogenic factors, namely, vascular endothelial growth factor (VEGF) and fibroblast growth factor (beta-FGF), on the migration of HUVECs in the carcinoma cell spheroid. The outward migration of HUVECs in 200 mu m spheroids was hindered by the treatment with VEGF and beta-FGF. Moreover, some of the HUVECs formed hollow lumen within 72 h under VEGF and beta-FGF treatment. The combination of SPIM and microfluidic devices gives high resolution in both spatial and temporal domains. The observation of HUVECs in spheroids provides us insight on tumor vascularization, an ideal disease model for drug screening and fundamental studies. (C) 2014 AIP Publishing LLC.