Interestingly, TPEN alone did not induced cell apoptosis evaluated with Annexin-V staining, or DNA damage evaluated with γ-H2AX expression (Figures 1H and 1I), but TPEN dramatically enhanced DOX-induced cell apoptosis and DNA damage in LLC cells (42.12 ± 0.51% for DOX, 88.81 ± 2.14% for DOX+TPEN) (Figure 1H), suggesting that TPEN enhanced the killing of tumor cells by DOX. This evidence concerns the gene H2AX and neoplasm.