Experimental study of low-frequency ultrasound combined with microbubbles promote enhanced green lfuorescent protein plasmid transfecting into transplanted prostate cancer of nude mice / 中华医学超声杂志（电子版）

ABSTRACT

Objective To investigate the feasibility of low-frequency ultrasound combined with microbubbles improving transfection of enhanced green lfuorescent protein plasmid (pEGFP) to subcutaneously transplanted prostate cancer in nude mice, and to optimize the parameters of intensity. Methods The model of nude mice of subcutaneously transplanted prostate cancer were built. Then they were divided into 2 groups including low-frequency ultrasound group and low-frequency ultrasound combined with microbubbles group, each group with 15 mice. Then 250μl of mixture of saline and pEGFP (50μg) were co-injected in low-frequency ultrasound group and 250μl of mixture of SonVue and pEGFP (50μg) were co-injected in low-frequency ultrasound combined with microbubbles group through tail vein. According to intensity, they were divided into 3 subgroups respectively, including group 1 W/cm2, group 2 W/cm2 and group 3 W/cm2, each group with 5 mice. Ultrasound was applied at 80 kHz input frequency with 50%duty cycle for 10 minutes after pEGFP injection. The tumors were collected on the third day after treatment. The expression of pEGFP in tumor was examined by laser scanning confocal microscope (ISCM) and the average lfuorescence intensity were estimated. At the same time, routine pathological examination was performed. The mean lfuorescence intensity of low frequency ultrasound group and low frequency ultrasound combined with microbubble group were compared with one-way ANOVA and those of any two groups were compared by SNQ-q test. Results TThe mean lfuorescent light in low-frequency ultrasound combined with microbubbles group were 23.75±2.54, 30.25±1.67 and 59.60±2.03, which were obviously stronger than those of low-frequency ultrasound treatment group (14.04±1.35, 14.66±0.98 and 14.32±1.20), the difference was statistically signiifcant (the value of q were 18.26, 14.12 and 13.88, P<0.05). The rate of gene transfection increased along with the enhancement of the ultrasound intensity (the value of q were 15.33, 17.81 and 13.79, P<0.05). Histology analyses performed by HE staining showed that there was no damage to the tumor tissues in all groups, tumor tissues were intact and without infection. Conclusions Low-frequency ultrasound combination with microbubbles can significantly enhance pEGFP transfecting into subcutaneously transplanted prostate cancer in nude mice. In certain range, improving the ultrasound intensity can increase the rate of gene transfection.