Treg cells were found to proliferate in tumors in MUC1.Tg mice.

<p>SL4-MUC1 cells (1×10⁶ cells/50 µL) were injected into the space under the cecal serosa of B6 mice or MUC1.Tg mice. Ten days after injection, mice were sacrificed, the cecal tumors, spleens, and MLNs were resected and single cell suspensions were prepared. (A) Cells from MUC1.Tg mice in each organ were stained with CD4, Foxp3, and Ki-67 and percentage of Ki-67⁺ Treg cells in each organ were shown. Lines indicate the median values. (B) Cells from tumor tissues in B6 or MUC1.Tg mice were stained with CD4, Foxp3, and Ki-67 and the absolute number of Ki-67⁺ Treg cells was calculated. The absolute number of Ki-67⁺ Treg cells normalized to the cecal weight was illustrated. A representative result from two independent experiments is shown.