MUC1 and neoplasm: Because the number of intratumoral Treg cells increased at day 10, and the increase was more prominent in MUC1.Tg mice than in B6 mice (Fig. 2C), the enhanced percentages of Treg cells in MUC1.Tg mice at day 10 (Fig. 2A) could be due at least in part to the infiltration or proliferation of Treg cells in the MUC1-expressing tumor tissues.