| Malignant tumor is one of the most deadly diseases for human. Scientists from both home and abroad having been done many researches to conquer it. In 1989, Japanese Umemura put forword Sonodynamic Therapy ( SDT ) for the first time. The therapy presumes that the enhancement of antitumor effect is caused by US activated HpD. Ultrasound especially focus ultrasound can penetrate deeply in organic tissues without any harm, so the application of SDT is a promising way on treatment of tumors in deep tissue. Many scholars at home and abroad have done many researches on this and obtained some primary results, but the study on the cytological molecular biology mechanism of SDT have not done enough.Based on the internal and external studies, this paper has designed to solve the two significative problems. One is to define the optimum parameter of the irradiation, the other is to study the changes of microstructure, ultramicrostructure, cytochemistry, molecular structure for human liver cancer cell SMMC-7721 and human hematopoietic cell K562 by combined treatment with US and Hp, and whether or not SDT can cause cancer cells apoptosic phenomena under certain conditions, whether or not lipid peroxidation appears during the course of SDT, and whether or not the reproduce potential of tumor cells drops correspondingly.The author has used MTT, which has been proved to be a reliable way to study the activity of cells, to study the survival of SMMC-7721 and K562 in vitro under the certain ultrasonic intensity(3.0W/cm2), and the experimental results show: (l)When the ultrasonic frequency was 1.6MHz, the survival rate of SMMC-7721 and K562 cancer cells in six mediums was remarkable fall compared with control cells; (2)When exposed to 2.0,2.6,3.0MHz focus ultrasound, the killing effexct of ultrasonically activated HpD for SMMC-7721 and K562 cancer cells in six mediums was different compared with control cells.Based on this, The author used H-E staining under light microscope, PI-HO33342 fluorescent staining, scanning electron microscopy and transmission electron microscope to observe the morphologic changes of the tumor cells after beingradiated by US at the same frequency but different mediums, and proved that SDT made tumor cells death and apoptosis by destroying the microstructure and the ultramicrostructure , especially the cell membrane and the organelle membrane thereby to achieve the antitumor effect.With the method of TBA chromotest, we detected the influence of HpD combined 2.6MHz frequency US on the degree of lipid overoxidation of tumor cells in different mediums, and found the quality of lipid overoxidation arising, especially in simple mediums.Through clone forming test, we observed that in suspensions of physiological saline, phosphated buffer, RPMI1640 culture medium and complete medium, after HpD combined with US treated tumor cells, the relative clone formation rate of K562 cells were 4.94%,6.85% ,5.77% and 10.15%. This could show that proliferation potential of K562 cells treated with acoustic irradiation decreased greatly.We used agarose gel eletrophoresis to detected significant apoptosis phenomena accompany with necrosis. In different mediums the proportion of apoptosis and necrosis was different.The above experimental result showed SDT had multiform models for antitumor and was influenced by different physical and chemical factors with complex biology elements. Especially, in this experiment, we found that low-intensity ultrasonically activated HpD could induce tow kinds of tumor cells apoptosis for the first time. This conclusion had certain meaning to rich and develop SDT theory for advanced study of mechanism of SDT.
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