MKI67 and neoplasm: By using Ki67 staining we found that, IL-9 stimulation did not induce tumor cell proliferation of LL/2 cells (Figure 6A). In addition, IL-9 significantly reduced late apoptosis in LL/2 cells at the lower concentration analyzed, as determined by Annexin/PI staining, suggesting that IL-9 may directly regulate apoptosis of LL/2 lung tumor cells in a dose dependent manner (Figure 6B). The overall survival of LL/2 was induced by higher concentrations of IL-9 at 100ng/ml (Figure 6C).