Brief Article
Copyright ©2010 Baishideng. All rights reserved.
World J Gastroenterol. Jul 28, 2010; 16(28): 3584-3591
Published online Jul 28, 2010. doi: 10.3748/wjg.v16.i28.3584
Enhancement of antitumor vaccine in ablated hepatocellular carcinoma by high-intensity focused ultrasound
Ying Zhang, Jian Deng, Jun Feng, Feng Wu
Ying Zhang, Jian Deng, Jun Feng, Feng Wu, Institute of Ultrasonic Engineering in Medicine, Chongqing Medical University, Chongqing 400016, China
Author contributions: Wu F and Zhang Y designed the research; Zhang Y, Deng J, Feng J and Wu F performed the research; Zhang Y and Deng J analyzed the data; Wu F and Zhang Y wrote the paper.
Supported by The Foundation of Ministry of Education of China, No. IRT0454
Correspondence to: Feng Wu, MD, PhD, Professor, Institute of Ultrasonic Engineering in Medicine, Chongqing Medical University, PO Box 153, Medical College Road 1, Chongqing 400016, China. mfengwu@yahoo.com
Telephone: +86-23-68485022 Fax: +86-23-68610718
Received: December 8, 2009
Revised: April 6, 2010
Accepted: April 13, 2010
Published online: July 28, 2010
Abstract

AIM: To investigate whether tumor debris created by high-intensity focused ultrasound (HIFU) could trigger antitumor immunity in a mouse hepatocellular carcinoma model.

METHODS: Twenty C57BL/6J mice bearing H22 hepatocellular carcinoma were used to generate antitumor vaccines. Ten mice underwent HIFU ablation, and the remaining 10 mice received a sham-HIFU procedure with no ultrasound irradiation. Sixty normal mice were randomly divided into HIFU vaccine, tumor vaccine and control groups. These mice were immunized with HIFU-generated vaccine, tumor-generated vaccine, and saline, respectively. In addition, 20 mice bearing H22 tumors were successfully treated with HIFU ablation. The protective immunity of the vaccinated mice was investigated before and after a subsequent H22 tumor challenge. Using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, the cytotoxicity of splenic lymphocytes co-cultured with H22 cells was determined in vitro before the tumor challenge, and tumor volume and survival were measured in vivo after the challenge in each group. The mechanism was also explored by loading the vaccines with bone marrow-derived dendritic cells (DCs).

RESULTS: Compared to the control, HIFU therapy, tumor-generated and HIFU-generated vaccines significantly increased cytolytic activity against H22 cells in the splenocytes of the vaccinated mice (P < 0.001). The tumor volume was significantly smaller in the HIFU vaccine group than in the tumor vaccine group (P < 0.05) and control group (P < 0.01). However, there was no tumor growth after H22 rechallenge in the HIFU therapy group. Forty-eight-day survival rate was 100% in mice in the HIFU therapy group, 30% in both the HIFU vaccine and tumor vaccine groups, and 20% in the control group, indicating that the HIFU-treated mice displayed significantly longer survival than the vaccinated mice in the remaining three groups (P < 0.001). After bone marrow-derived DCs were incubated with HIFU-generated and tumor-generated vaccines, the number of mature DCs expressing MHC-II+, CD80+ and CD86+ molecules was significantly increased, and interleukin-12 and interferon-γ levels were significantly higher in the supernatants when compared with immature DCs incubated with mouse serum (P < 0.001). However, no differences of the number of mature DCs and cytokine levels were observed between the HIFU-generated and tumor-generated vaccines (P > 0.05).

CONCLUSION: Tumor debris remaining after HIFU can improve tumor immunogenicity. This debris releases tumor antigens as an effective vaccine to develop host antitumor immune response after HIFU ablation.

Keywords: Hepatocellular carcinoma; High-intensity focused ultrasound; Immune response; Immunogenicity; Immunotherapy; Thermal ablation; Tumor vaccine