Reconstitution of the in vivo micro environment is one of the bottlenecks to be overcome in the in vitro anticancer drug studies, which has been long constrained by conventional 2D cell culture systems that may not accurately mimic the 3D environment in which cancer cells reside in vivo. The dynamics of 2D models differ from 3D models at multiple levels starting from nutrient and gaseous state in the medium to the growth conditions, micro environment and secretion of paracrine and autocrine factors. As a result, 2D environment may provide limited data regarding the predicted response of cancer cells to chemotherapeutics which may not be satisfactory.

To address these short comings of the 2D systems, we propose applying 3D culture technique for screening anticancer drugs. Tumor spheroids derived from cancer stem cells naturally mimic tumors with inherent metabolic (oxygen, carbon dioxide, nutrients and wastes), proliferative gradients, and establish physiological cell-cell and cell-substrate interactions that regulate proliferation and differentiation. Thus, they serve as excellent tumor models which are much closer to the human physiological conditions and possibly yielding more reliable and meaningful therapeutic results compared to 2D models.