While this outcome has not been previously reported in HepaRG spheroids, a study on the real-time viability detection of Cellosaurus tumor spheroids revealed that propidium iodide and caspase 3/7 fluorescence showed a time-dependent increase from day 4 to day 7 [31], which implies that the compaction-induced necrotic core was caused by hypoxia. Here, CASP3 is linked to neoplasm.