Concentrations of caspase-3 molecules have been estimated at 2.1×104 molecules per cell in unstimulated HeLa [34] cells or up to 1.6×106 molecules per cell for certain cancer cell lines [35], and in most cell culture systems 2–10 μM of caspase inhibitor suffice to inhibit cell death after apoptotic stimulation. Here, CASP3 is linked to cancer.