Why 3D Cell Culture Is Better For In Vivo Conditions

By Brad Larson, Senior Applications Scientist, Applications Department, BioTek Instruments

Over the last decade, a central focus of drug discovery efforts has been the incorporation of in vitro testing models that better mimic in vivo conditions found within the target patient. An initial step saw a move away from biochemical assays using purified drug target, in favor of a cell-based approach which utilized over-expression of drug target in common host cell lines, such as CHO and HEK-293. The quest for greater physiological relevance proceeded to the use of primary cells, preferably human if supply was adequate, and the reliance on endogenous expression of drug target should detection technology be sensitive enough. A large percentage of these cell types, being naturally adherent, allowed simple culturing workflows that seeded cells in a coated microplate well, incubating the microplate to encourage the cells to attach in a two dimensional (2D) monolayer before performing the prescribed assay. While providing initial improvements over biochemical and immortalized cell lines, an abundance of evidence now supports the reality that culturing cells in this 2D manner is often problematic and is a relatively poor model for in vivo conditions and behaviors. Using a 2D model, attrition rates of drug candidates for cancer were approximately 95%, stemming from in vitro drug efficacy values that did not translate to the clinic, as well as unforeseen toxicity issues. In 2011 alone, out of approximately 900 anti-cancer therapies in clinical trials or under Federal Drug Administration review, only twelve achieved approval; resulting in the loss of hundreds of millions of dollars that were spent on pre-clinical and clinical trials. The reason for these shortfalls can be traced to using conventional 2D conditions, where extracellular matrix (ECM) components, cell-to-cell and cell-to-matrix interactions, important for differentiation, proliferation and cellular functions in vivo, are lost.