 The activation of procaspase-7 by PAC-1 is consistent with biochemical data, although the relative importance of the procaspase-7 target in cells with functional procaspase-3 is uncertain.A potential selectivity problem arises because procaspase-3 is present in most cells of the body.However, it has been shown that in many cancers, including certain neuroblastomas, lymphomas, leukemias, melanomas, and liver cancers, procaspase-3 is present in higher concentrations.