Effect Of HIFU On Hypoxia-inducible Factor(HIF-1α, HIF-2α) And Cell Apoptosis In Liver Cancer Cell Xenografts In Nude Mice

PART Ⅰ Effect of HIFU on cell apoptosis in liver cancer cellxenografts of nude miceObjective: To study the changes of apoptosis by residual tumor cells ina mouse model of hepatocarcinoma after treatment with high-intensityfocused ultrasound (HIFU).Methods: Human HepG2cells were implanted into36nude mice andonce the tumor was established, the mice were treated with a HIFUtherapeutic apparatus. HIFU treatment parameters comprised:frequency setat8.6MHz,pulse at1000Hz, acoustic power fixed at5W.The mice wererandomly divided into a control untreated group and5treatment groupsbased upon the days of post-HIFU treatment (1,3,5,7and14days).Pathological changes were observed using hematoxylin and eosin (HE)staining. SP immunohistochemistry, western blot and real-time quantitativePCR were used to detect P53protein and mRNA expression.Results: HE staining showed that liver tissues contained residualtumor cells and large necrotic areas after HIFU treatment. Compared withother groups, the apoptosis index in3d group was significantly higher (P <0.01),in the5d group,1w group,2w group gradually decreased.Immunohis-tochemistry analysis indicated increased expression of P53protein in theHIFU treated mice compared to the untreated controls. Western blot andRT-PCR analysis showed an increase in P53expression in the liver tissueof mice treated with HIFU from1to3days. This effect reached maximum3days after treatment (P <0.01).Conclusion: HIFU treatment can induce apoptosis in residual tumorand the time of this effect may last for2weeks, which may be closelyrelated with P53expression. PART Ⅱ Effect of HIFU on hypoxia-inducible factor in thehepatocellular carcinomaObjective: To study the expression of hypoxia-inducible factor(HIF-1α and HIF-2α) by residual tumor cells in a mouse model ofhepatocarcinoma after treatment with high-intensity focused ultrasound(HIFU).Methods: Human HepG2cells were implanted into36nude mice andonce the tumor was established, the mice were treated with a therapeuticapparatus. HIFU treatment parameters comprised:frequency set at8.6MHz,pulse at1000Hz, acoustic power fixed at5W.The mice were randomly divided into a control untreated group and5treatment groupsbased upon the days of post-HIFU treatment (1,3,5,7and14days).SPimmunohistochemistry, western blot and real-time quantitative PCR wereused to detect HIF-1α and HIF-2α protein and mRNA expression.Results: Immunohistochemistry analysis indicated increasedexpression of HIF-1α and HIF-2α protein in the HIFU treated micecompared to the untreated controls. Western blot and RT-PCR analysisshowed an increase in HIF-1α expression in the liver tissue of mice treatedwith HIFU for1to3days. This effect reached maximum3days aftertreatment (P <0.01). Compared with the other groups, there was nosignificant change in expression of HIF-2α from1day and3days afterHIFU treatment（P>0.05). However,5,7and14days post-HIFU treatmentshowed a significant increase in HIF-2α expression (P<0.01).Conclusion: HIFU treatment caused a brief rise of cell apoptosis inresidual tumor cells which may be associated with HIF-1α expression.ThusHIF-2α may be closely related with decreased cell apoptosis in residualtumor.