Under these conditions, YM155 treatment identified 3 subgroups of breast tumors: the first group exhibiting a response to YM155 above 20% in cleaved caspase-3 staining, defined as sensitive tumors, included 10 tumors and the second including 7 tumors with caspase-3 scores under 5% was considered as YM155-resistant tumors. Here, CASP3 is linked to breast neoplasm.