Effect of ADU-S100/doxorubicin in situ vaccine on diffuse large B-cell lymphoma and its mechanism / 白血病·淋巴瘤

ABSTRACT

Objective:To explore the antitumor effect of ADU-S100/doxorubicin in situ vaccine on diffuse large B-cell lymphoma (DLBCL) and its mechanism.Methods:The 6-week-old female BALB/c mice were selected, and the bilateral murine subcutaneous B-cell lymphoma model was established with murine B-cell lymphoma A20 cells. The subcutaneous tumor-bearing mice were randomly divided into untreated group (without treatment), ADU-S100 in situ vaccine treatment group (intratumoral injection of interferon gene stimulating factor agonist ADU-S100), doxorubicin in situ vaccine treatment group (intratumoral injection of doxorubicin), and ADU-S100/doxorubicin in situ vaccine treatment group (intratumoral injection of ADU-S100 and doxorubicin) by using random number table method, with 5 mice in each group. The right tumors of the bilateral subcutaneous tumor-bearing mice were defined as proximal tumors, and the left tumors of the bilateral subcutaneous tumor-bearing mice were defined as distal tumors. Only the proximal tumors were treated via the intratumoral route, and the distal tumors were not treated. On day 23 after tumor inoculation, the percentages of CD11c + dendritic cells (DC), CD8 + CD11c + DC and CD80 + CD11c + DC in the spleen of mice in each group were detected by flow cytometry. The splenocytes of mice in each group were stimulated with A20 tumor cell lysate in vitro, the percentages of 5'-ethynyl-2'-deoxyuridine-positive (EdU +) cells and tumor necrosis factor-α-positive (TNF-α +) cells in CD8 + T cells in each in situ vaccine treatment group were detected by flow cytometry, and the killing effect of cytotoxic T lymphocyte (CTL) in each group was measured by using the lactate dehydrogenase (LDH) cytotoxicity assay kit. The mice treated with ADU-S100/doxorubicin in situ vaccine were intraperitoneally injected with anti-mouse CD8α (clone 53-6.7) mAb or isotype control on days 7, 12 and 17 after tumor inoculation to eliminate CD8 + cells. On day 23 after tumor inoculation, the proximal and distal tumor volumes of mice in the ADU-S100/doxorubicin in situ vaccine combined with anti-mouse CD8α (clone 53-6.7) mAb or isotype control treatment group were measured, the percentages of CD8 + T cells and CD8 + CD11c + DC in the spleen of tumor-bearing mice in these two groups were detected by flow cytometry, and the infiltration of CD8 + T cells in the tumor tissues from these two groups was detected by immunohistochemistry (IHC) staining. Results:On days 11, 14, 17, 20 and 23 after tumor inoculation, the proximal and distal tumor volumes of mice in each treated group were lower than those in the untreated group (all P < 0.05). The proportions of CD11c + DC in the spleen of the untreated group, ADU-S100 in situ vaccine treatment group, doxorubicin in situ vaccine treatment group and ADU-S100/doxorubicin in situ vaccine treatment group were (4.92±0.63)%, (7.54±0.84)%, (7.45±0.86)% and (11.63±0.85)%, respectively, and the difference was statistically significant ( F = 72.30, P < 0.001); the proportions of CD8 + CD11c + DC were (1.36±0.34)%, (4.02±0.43)%, (4.22±0.61)% and (6.11±0.73)%, respectively, and the difference was statistically significant ( F = 76.09, P < 0.001); the proportions of CD80 + CD11c + DC were (0.51±0.24)%, (1.69±0.23)%, (1.82±0.25)% and (4.09±0.39)%, respectively, and the difference was statistically significant ( F = 167.40, P < 0.001). The CTL responses and the proportion of EdU + cells and TNF-α + cells in CD8 + T cells in each in situ vaccine treatment group were higher than those in the untreated group (all P < 0.05). Furthermore, the enhanced CTL responses and the increased proportion of EdU + cells and TNF-α + cells in CD8 + T cells were observed in the ADU-S100/doxorubicin in situ vaccine treatment group as compared to the ADU-S100 in situ vaccine treatment group and doxorubicin in situ vaccine treatment group (all P < 0.05). The proportions of CD8 + T cells and CD8 + CD11c + DC in the spleen of mice treated with ADU-S100/doxorubicin in situ vaccine and anti-mouse CD8α mAb were lower than those in ADU-S100/doxorubicin in situ vaccine and isotype control group (both P < 0.05) and both proximal and distal tumor volumes of mice treated with ADU-S100/doxorubicin in situ vaccine and anti-mouse CD8α mAb were larger than those in ADU-S100/doxorubicin in situ vaccine and isotype control group (both P < 0.05). Conclusions:ADU-S100/doxorubicin in situ vaccine can induce profound regression of proximal tumors in bilateral murine subcutaneous B-cell lymphoma model and generate systemic immune responses capable of partially inhibiting distant tumor growth, and the antitumor efficacy of ADU-S100/doxorubicin in situ vaccine may require CD8 + CD11c + DC-mediated CD8 + T cell immune responses.