CASP3 and Parkinson disease: When exposed to neurotoxins, such as 1-methyl-4-phenyl-pyridinium ion (MPP+) and 6-hydroxydopamine (6-OHDA), RA-differentiated cells expressed higher tolerance as shown by the lower rate of the release of lactate dehydrogenase (LDH), cell mortality, and caspase-3 activation, compared to undifferentiated cells, suggesting that undifferentiated cells are more appropriate for studying neurotoxicity or neuroprotection in experimental PD research [2].