Cellular damage and apoptosis along with changes in NF-kappa B expression were induced with contrast agent enhanced ultrasound in gastric cancer cells and hepatoma cells

Ultrasound irradiated gastric cancer cells (SGC7901 cell line) and hepatocellular carcinoma cells (SMMC-771 cell line) cultured in medium containing contrast agent. Significant cellular damage and apoptosis were observed in the bath cells incubated for 24 hours following 120 seconds ultrasonic irradiation. I kappa B alfa expression synchronously increased in the treatment groups of both the cell lines, and the down-regulated expression of NF-kappa B influenced its-regulated expression of genes that related to apoptosis. Production of intracellular ROS and elevation of NF-kappa B level occurred after incubation of the cells for 1 hour following ultrasonic treatment.Our result suggested that contrast agent enhanced the biological effect of ultrasound. Their reaction might stimulate the transitory expression of NF-kappaB, and subsequent elevation in IκBalfa expression could lead to the apoptosis of SGC7901 cells and SMMC-771 cells.Studies regarding the ultrasonic effects on the proliferation of cells have gradually led to the development of a new field of ultrasonic biological research and promoted the emergence of a new direction for ultrasonic medical therapy [1]. Furthermore, low-frequency ultrasonic (20 khz-2 Mhz) irradiation has the ability to directly kill tumor cells including inhibiting tumor cell proliferation and inducing apoptosis [2,3]. The mechanism of inhibition of tumor cell growth may be related to the cavitation effect of low-frequency ultrasound, because free radicals, produced via the cavitation effect, interrupt the replication of normal double-stranded deoxyribonucleic acid (DNA) by promoting the polymerization of DNA strand and restrain cell growth [4]. The biomechanics study regarding the dynamic characteristics of an ultrasound contrast agent suggested that ultrasound irradiation with a microbubble contrast agent may cause cellular injury[5]. In combination with a microbubble contrast agent, ultrasound might promote cellular injury, including th