Expression of heat shock protein 70 in rabbit liver after contrast-enhanced ultrasound and radiofrequency ablation.

Heat shock proteins (HSPs) induced by thermal ablation therapy may help presenting tumor antigen to the host immune system and be a valuable adjuvant in the ablation therapy of liver cancer. This paper described our preliminary study on the expression of HSP70 in rabbit liver after contrast-enhanced ultrasound (CEUS) and radiofrequency (RF) ablation. Twenty-five male New Zealand white rabbits were divided into five groups as: control group (n=5), ultrasound group (n=5), CEUS group (n=5), RF group (n=5) and CEUS+ RF group (n=5). Clinical ultrasound and RF ablation equipment were used in the present experiment. Sonazoid was used as the contrast agent. All the animals were sacrificed 24 h after the procedure, and HSP70 was detected by immunohistochemistry staining and Western blot analysis. In the groups without RF ablation, there was no evidence of HSP70 expression in the liver tissue of the control group and ultrasound group, whereas positive HSP70 expression was detected in the liver tissue of the CEUS group, with a mean optical density of 0.33. In the RF and CEUS+ RF groups, there were cells showing HSP70 expression in the normal liver tissue far from the ablation region. The mean densities of HSP70 expression were 0.31 in the RF group and 0.35 in the CEUS+ RF group, respectively. With regard to the distribution of HSP70 expression of the RF and CEUS+ RF groups, the marginal areas were stronger than liver tissue 1 cm away from the margin, and the ablated tissues showed no evidence of HSP70 expression. The mean density of HSP70 expression in the marginal areas were 0.47 in the RF group and 0.42 in the CEUS+ RF group, respectively. CEUS using Sonazoid may produce HSP70 expression in the normal liver parenchyma after CEUS examination and RF ablation. (E-mail: moriyasu@tokyo-med.ac.jp).