Enzyme induction studies
Induction of drug metabolizing enzymes (DMEs) constitutes a serious concern during drug development, as it can impact the efficacy and safety of drug candidates mostly but not exclusively when co-administered with other medications. Induction of DMEs manifests only after repeated exposures and occurs primarily by transcriptional stimulation mediated by nuclear receptors (NRs), such as PXR and CAR, and thus relies on sufficient NR levels. Importantly, expression of NRs is rapidly downregulated in conventional 2D culture models, whereas they remain constant in the 3D spheroid platform over multiple weeks (Fig. 1).
Figure 1: Expression of important hepatic xenobiotic sensors is preserved for multiple weeks in 3D spheroid culture. Expression of the nuclear receptors CAR and PXR remains close to physiological levels in the spheroid system (red), whereas expression is strongly downregulated in 2D culture of the same donors (blue; n=3 donors). The data is presented on semi-log plots showing fold change expression changes compared to freshly isolated cells. Dashed lines depict the evolution of fold changes between 2D and 3D culture over time. Error bars indicate SEM. Figure modified from Vorrink et al., FASEB J, 2017.