The smaller pRB + population in M-Smo/EedcKO tumors at P12, the increased rate of proliferation within the pRB + population, and the similar pRB + population at P18 are all consistent with a biphasic effect of Eed deletion on tumor growth, in which tumors initially grew more slowly and then accelerated, producing shorter survival times. This evidence concerns the gene EED and neoplasm.