MKI67 and neoplasm: By Ki67 staining, we detected that IL-9 stimulation significantly induced L1C2 tumor cell proliferation in a dose dependent manner (Figure 7H). In addition, IL-9 significantly reduced early apoptosis in L1C2 cells at lower concentrations, as determined by Annexin/PI staining, suggesting that IL-9 may directly regulate both apoptosis and proliferation of L1C2 lung tumor cells (Figure 7H).