T-lymphocytes from focused ultrasound ablation subsequently mediate cellular antitumor immunity after adoptive cell transfer immunotherapy.

Background: Our previous studies found that high-intensity focused ultrasound (HIFU) stimulated tumor-specific T cells in a mouse H22 tumor model, and adoptive transfer of the T cells from HIFU-treated mice could subsequently elicit stronger inhibition on the growth and progression of the implanted tumors. The aim of this study was to investigate the mechanism of T cells from focused ultrasound ablation in HIFU-mediated immunomodulation. Methods: Sixty H22 tumor-bearing mice were treated by either HIFU or sham-HIFU, and 30 naïve syngeneic mice served as controls. All mice were euthanized on day 14 after HIFU and splenic T cell suspensions were obtained in each group. Using an adoptive cell transfer model, a total of 1 × 106 T cells from HIFU treated-mice were intravenously injected into each syngeneic H22 tumor-bearing mouse twice on day 3 and 4, followed by the sacrifice for immunological assessments at 14 days after the adoptive transfer. Results: T cells from HIFU-treated mice could significantly enhance the cytotoxicity of CTLs (p < 0.001), with a significant increase of TNF-α (p < 0.001) and IFN-γ secretion (p < 0.001). Compared to control and sham-HIFU groups, the number of Fas ligand+ and perforin+ tumor-infiltrating lymphocytes (TILs) and apoptotic H22 tumor cells were significantly higher (p < 0.001) in the HIFU group. There were linear correlations between apoptotic tumor cells and Fas ligand+ TILs (r = 0.9145, p < 0.001) and perforin+ TILs (r = 0.9619, p < 0.001). Conclusion: T cells from HIFU-treated mice can subsequently mediate cellular antitumor immunity, which may play an important role in the HIFU-based immunomodulation.

Specific antitumour immunity of HIFU-activated cytotoxic T lymphocytes after adoptive transfusion in tumour-bearing mice.

PURPOSE: The aim of this study was to investigate the specific anti-tumour immunity of cytotoxic T lymphocytes (CTL) activated by high-intensity focused ultrasound (HIFU) after adoptive transfer in a murine tumour model. MATERIALS AND METHODS: H22 tumour-bearing mice were treated by either HIFU or sham-HIFU, while naïve syngeneic mice were used as controls. They were sacrificed and the spleens were harvested 14 days after HIFU. T lymphocytes were obtained from the spleens, and then adoptively transferred into 40 mice each bearing a 3-day implanted H22 tumour. On day 14 after adoptive transfer, 10 mice were sacrificed in each group for assessment of the number of tumour-infiltrating T lymphocytes and interferon-gamma (IFN-γ) secreting cells. The remaining 30 mice were continuously observed for 60 days, and tumour growth, progression and survival were recorded. RESULTS: HIFU significantly increased peripheral blood CD3(+), CD4(+) levels and CD4(+)/CD8(+) ratio (P < 0.05), CTL cytotoxicity (P < 0.01) and IFN-γ and TNF-α secretion (P < 0.01) in H22 tumour-bearing mice. Adoptive transfer of HIFU-activated T lymphocytes into the autologous tumour-bearing mice induced a significant increase of tumour-infiltrating T lymphocytes and IFN-γ-secreting cells (P < 0.001). Compared to the control and sham-HIFU groups, HIFU-activated lymphocytes elicited significant inhibition of in vivo tumour growth (P < 0.01) and progression (P < 0.0001), and longer survival time in the tumour-bearing mice (P < 0.001). CONCLUSIONS: HIFU could enhance CTL's specific antitumour immunity. Adoptive transfer of HIFU-activated T lymphocytes could increase local antitumour immunity, and elicit stronger inhibition on tumour growth and progression, with more survival benefit in the autologous tumour-bearing mice.

High-intensity focused ultrasound tumor ablation activates autologous tumor-specific cytotoxic T lymphocytes.

Previous studies have shown that high-intensity focused ultrasound (HIFU) ablation can enhance host antitumor immune response, though the mechanism is still unknown. In the present study, we investigated whether HIFU ablation could activate tumor-specific T lymphocytes and then induce antitumor cellular immunity. We studied 70 C57BL/6J mice bearing the H(22) tumor; they were randomly divided into a HIFU group and a sham-HIFU group. Of the mice, 35 in the HIFU group underwent HIFU ablation of the H(22) hepatic tumor, and the remaining 35 received a sham-HIFU procedure. In addition, 35 female, naïve syngeneic C57BL/6J mice were used as controls. All mice were sacrificed 14 days after HIFU, and the spleens were harvested. The function of T lymphocytes was determined. As a valuable tool for detecting and characterizing peptide-specific cells, the frequency of MHC class I tetramer/CD8-positive cells was quantified, which could help to determine the response and number of T lymphocytes. The therapeutic effect of the HIFU-activated lymphocytes on tumor-bearing mice was investigated after adoptive transfer of the lymphocytes. The results showed that compared to sham-HIFU and control groups, HIFU ablation significantly increased the cytotoxicity of cytotoxic T lymphocytes (p < 0.05), with a significant increase of IFN-γ and TNF-α secretion (p < 0.001). The frequency of the MHC class I tetramer/CD8-positive cells was significantly higher in the HIFU group (p < 0.05). A stronger inhibition of tumor progression and higher survival rates were observed to be significant after adoptive immunotherapy in the HIFU group as compared to the sham-HIFU and control groups (p < 0.01). It is concluded that HIFU ablation could activate tumor-specific T lymphocytes, thus inducing antitumor cellular immune responses in tumor-bearing mice.