Inhibitory effects of different expression plasmids on liver cancer in a mouse model. The differential plasmid treatments were: Control, pGFP-IRES, pGM-CSF-IRES, pIL-21-IRES, pGM-CSF-IRES-IL-21, and pGM-CSF-GFP-IRES-Rae-1-IL-21. Tumor-bearing mice were sacrificed 10 d after treatment and histological sections were made from various tumor tissues. A; Histopathology of tumor tissues in mouse liver cancer (HE × 400 magnification). (a) and (b) shows histopathological tumor tissue sections in mice treated with PBS or pGFP-IRES, wherein the tumor cells grew actively. (c) and (d) shows histopathological sections from the tumor tissue of tumor-bearing mice treated with pGM-CSF-IRES or pIL-21-IRES, wherein the tumor cells grew slowly, and only few immunocytes were seen infiltrating the tumor tissue. (e) showing histopathological sections from the tumor tissues of tumor-bearing mice treated with pGM-CSF-IRES-IL-21. Infiltration of immunocytes increased appreciably and necrotic tumor cells were noticeable in the tumor tissue. (f) showing histopathological sections of the tumor tissues in tumor-bearing mice treated with pGM-CSF-GFP-IRES-Rae-1-IL-21. Here, both monocytes and neutrophils infiltrated the tumor, and there was evidence of mass necrosis seen in the tumor tissue. Note that the red arrow indicates inflammatory cells. B; showing the tumor weights (expressed as mean ± standard deviation) of mice in each group 10 d after treatment (n = 10). C; tumor volumes of mice (expressed as mean ± standard deviation) in each group 1–10 d after treatment (n = 10). D; showing the survival time of the mice in each group (n = 13) that were analyzed by the Kaplan-Meier approach. Note: **P < 0.01, as compared with the control. ##P < 0.01, as compared with the IRES/GM-SCF or IRES/IL21 expression constructs. △P < 0.05, as compared with the IRES/GM-SCF-IL-21 expression construct.