To investigate whether cytotoxicity induced by different TSCs leads to apoptotic cell death in lung and breast cancer cells, we first measured the activity of caspase 3, which irreversibly commits cells towards apoptosis, in MCF7 and A549 treated for 2 h with 50 μM solutions of the sigma-2 receptor-targeting TSCs FA4, MLP44, PS3 and the metal chelator ACThio1. The gene discussed is CASP3; the disease is breast cancer.