The IHC analysis further demonstrated that the percentage of Ki67‐positive cells (a marker of cell proliferation) was significantly higher in the sh‐CD2 CTL group, whereas the expression of Caspase‐3 (a proapoptotic marker) was markedly lower, indicating that CD2‐deficient CTLs promoted tumor cell proliferation and suppressed apoptosis (Figure 5E, Supporting Information S1: Figure S5B). Here, MKI67 is linked to neoplasm.