Three-dimensional porous silk tumor constructs in the approximation of in vivo osteosarcoma physiology

The lack of good preclinical models has hampered anticancer drug discovery. Standard preclinical protocols require the growth of cells in high throughput two-dimensional (2D) culture systems. However, such in vitro drug testing methods yield drug efficacy results that differ greatly from animal models. Conversely, it is much more difficult and expensive to use animal models for large-scale molecular biology research. It is conceivable that three-dimensional (3D) growth may be responsible for some of these changes. Porous silk sponges were fabricated through freeze drying and seeded with 143.98.2 osteosarcoma cells. Molecular profiles were obtained by carrying out real-time polymerase chain reaction for angiogenic growth factors and proliferation markers for osteosarcoma cells grown under 2D, 3D, and SCID mouse xenograft conditions. The angiogenic factor expression profiles for cells grown in 2D differed greatly from the 3D silk scaffold model (P < 0.05 for bFGF, HIF-1α, IL-8, and VEGF-A), whereas 3D tumor model profiles were found to be able to approximate that for the in vivo tumor better with no statistically different expression of HIF-1α and VEGF-A between the two. Immunohistochemistry staining for HIF-1α, VEGF-A, and VEGF receptor on osteosarcoma cells grown on the scaffolds validated the results obtained with the gene expression profiles. The results suggest that 3D tumor models could be used to bridge the gap between in vitro and in vivo tumor studies, and aid in the study of mechanisms activated during tumorigenesis for the development of novel targeted chemotherapy.