SMAD4 and neoplasm: As the TGF‐β/SMAD4 signaling has been reported to influence regulatory T (Treg) [13] and T helper 17 (Th17) [24] cell differentiation, we checked the percentage of Treg (gated as CD4+FOXP3+ population) and Th17 cells (gated as CD4+RORγT+ population) in tumor‐infiltrating CD4+ cells, and found no difference between WT and KO group (Figure S1B,D, Supporting Information).