Effects of intratumoral injection of immunoactivator after microwave ablation on antitumor immunity in a mouse model of hepatocellular carcinoma

This study investigated the effects of intratumoral injection of immunoactivator after microwave ablation on antitumor immunity in a mouse model of hepatocellular carcinoma. Hepatocellular carcinoma cell line Hepa1-6 was subcutaneously injected into C57/B6 mice to establish a mouse model of hepatocellular carcinoma. When tumor diameter reached 8 mm, microwave ablation was performed for 3 min with temperature controlled at 55˚C. Cytokine sustained-release microspheres (CytoMPS) containing human interleukin-2 (hIL-2) and mouse granulocyte macrophage colony-stimulating factor (mGM-CSF) were injected into the tumor of mice in the experimental group (n=5) at 3, 7 and 14 days after ablation, while sustained-release microspheres containing no cytokine were used in the control group (n=5). Mice were sacrificed on the 17th day after ablation, and CD4+ and CD8+ T cells in peripheral blood were counted by flow cytometry. Spleen was collected from the mice to isolate lymphocytes. Lactate dehydrogenase (LDH) release assay was used to determine the cytotoxicity of spleen cells to Hepal-6 cells. Injection of CytoMPS after ablation increased the percentage of CD4+ and CD8+ T cells in peripheral blood. Cytotoxicity of CD8+ CTL to Hepal-6 is significantly higher in experimental group than in control group (P<0.01). The results showed that intratumoral injection of CytoMPS containing hIL-2 and mGM-CSF can significantly increase the proportion of CD4+ and CD8+ T cells in blood and increase the cytotoxicity of CTL cells to tumor cells in mice with hepatocellular carcinoma.