Moreover, to clearly demonstrate that ATRA causes apoptosis in GIST-T1 cells, we assessed the molecular aspects of apoptosis, such as caspase-3, well recognized as a marker of apoptosis, and PARP, considered as a biochemical marker of necrosis when it is hyperactivated [27], by western blot. The gene discussed is CASP3; the disease is gastrointestinal stromal tumor.