CCNB1 and neoplasm: We found increased cyclin B1 and cleaved caspase-3 by immunoblotting in the tumor that responded to MLN2238 but did not observe increased cyclin B1 accumulation or activation of cleaved caspase-3 in the tumor without response (Figure 5—figure supplement 2g) suggesting that adequate inhibition of the proteasome was not achieved in mice with a suboptimal response.