Specific Anti-Tumor Immunity Of Peripheral Blood Lymphocyte In Mice With Implanted Tumor Treated With High Intensity Focused Ultrasound

OBJECTIVE Based on the previous research results, this study was designed to investigate functional changes in both immune activity and specific anti-tumor immunity of peripheral blood lymphocyte in tumor-bearing mice after high intensity focused ultrasound (HIFU) ablation for implanted tumors, and to provide more evidences of the mechanism involved in activated host anti-tumor immunity reaction after HIFU treatment. MATERIAL AND METHODS 1. Specific anti-tumor immune activity in vitro of lymphocytes after HIFU ablation A total of 24 normal C57/6J mice were randomly divided into three groups: HIFU group (n=8), sham-HIFU group (n=8), and control group (n=8). The mice in both HIFU group and sham-HIFU group received H22 hepatic carcinoma implantation using the hypodermic injection of H22 cells suspension in the back of each mouse. Seven days after tumor implantation, tumor mass was obviously detected in the local region. Subsequently, the mice in HIFU group underwent HIFU ablation for the implanted tumor, but those in sham-HIFU group received a sham therapy procedure with no acoustic energy deposition in the tumor. Those in control group were normal mice, without either tumor implantation or HIFU treatment. Fourteen days after HIFU, peripheral blood was collected in each mouse. Using adherence method and lymphocyte density gradient centrifugation, lymphocytes were extracted from peripheral blood in each group. MTT assay was employed to measure the lymphocyte cytotoxicity effect on H22 tumor cells in vitro in three groups respectively. 2. Immune protective effect of activated lymphocytes after HIFU ablation Forty-five normal C57/6J mice were randomly divided into three groups: HIFU group (n=15), sham-HIFU group (n=15), and control group (n=15). Using caudal vein injection technique, each mouse in HIFU group or in sham-HIFU group received 0.05ml lymphocyte suspension (2×107/ml) extracted from the peripheral blood of the tumor-bearing mice treated with HIFU or with sham-HIFU procedure respectively. Those in control group received the same amounts of serum extracted from normal mice. The injecting times were 2 sessions, once a day for 2 days without any interval. At the third day of post-injection, each mouse in 3 groups underwent H22 tumor implantation using the hypodermic injection of0.05ml H22 cells suspension(6×107cells/ml) in the back. All mice were followed up to observe tumor incidence, tumor extinction rate, tumor growth curve, metastasis rate, survival rate, and survival curve in each group respectively. 3. Immune therapeutic effect of activated lymphocytes after HIFU ablation Seventy-five mice bearing H22 tumor were randomly divided into three groups: HIFU group (n=25), sham-HIFU group (n=25), and control group (n=25). Three days after tumor implantation, each mouse in HIFU group or in sham-HIFU group was injected through caudal vein into 0.05ml lymphocyte suspension (2×107/ml) extracted from the peripheral blood of the tumor-bearing mice treated with HIFU or with sham-HIFU procedure respectively. Those in control group received the same amounts of serum extracted from normal mice. The injecting times were 2 sessions, once a day for 2 days without any interval. All mice in each group were followed up to observe tumor incidence, tumor extinction rate, tumor growth curve, metastasis rate, survival rate, and survival curve respectively. RESULTS 1. Specific anti-tumor immune activity in vitro of lymphocytes after HIFU ablation Lymphocyte cytotoxicity effect in vitro on H22 tumor cells in HIFU group, sham-HIFU group, and control group were (41.02±0.63)%, (3.74±2.50)%, and (1.24±1.73)% respectively. Compared to eithersham-HIFU group or control group, the lymphocyte cytotoxicity effect in HIFU group was significantly increased, and statistical differences were observed (P=0.0001) among them. However, there was no significant difference between sham-HIFU group and control group in the lymphocyte cytotoxicity effect (P=0.328). 2. Immune protective effect of activated lymphocytes after HIFU ab...