The Changes In Blood Supply And Neovascularization Of The Survival Cancerous Tissue After Transcatheter Arterial Embolization With Lipiodol In Rabbit VX2 Liver Tumor

Objective To evaluate the changes in blood supply and neovascularization of the survival cancerous tissue after transcatheter arterial embolization (THAE) with lipiodol in rabbit VX2 liver tumors, and to explore the essentiality of the portal vein chemoembolization and antiangiogenesis therapy in human liver cancer.Materials and Methods A total of 40 healthy New Zealand White rabbits were used. Through a epigastrium incision, minced VX2 carcinoma was implanted into the subcapsular parenchyma of the left medial lobe of the liver in traditional and improved process respectively. The liver CT plain scan and dual-phase dynamic contrast enhanced scan were performed in day 7 and day 14 after tumor implantation. Of which, 36 bearing liver cancer rabbits were selected for experiment and randomly divided into 3 groups: experimental group (group A, n=24), pseudo-operative group (group B, n=6) and control group (group C, n=6). One day after CT scan, the digital subtraction angiography (DSA) for hepatic artery and portal vein were performed. Group A was embolizated with lipiodol, and group B was dealed with 0.9% Sodium Chloride 2 ml. Group C was killed after DSA, then the liver tumors were removed and undertaken histopathologic examination. In day 21 and day 22, the remaining models were performed with CT plain scan and DSA examination respectively, then treated as group C. To evaluate the changes in blood supply of the survival cancerous tissue after THAE with lipiodol through the CT and DSA image, and to analyze the tumor neovascularization through the outcome of histopathologic examination (including immunohistochemistry). Results VX2 carcinoma were grown in livers of 36 rabbits. With improved method, the successful rate of implantation was higher than traditional method (95%,19/20), It was lower that the rate of disseminated metastasis in liver and implantation metastasis in enterocoelia or epiploon (P<0.05). The tumors'growth would be retardation because of lipiodol embolism. In day 21, the tumor volume was approximately 1.44±0.75 cm3 in group A, which had a significant difference with group B (6.90±2.22 cm3) (P<0.05), and the values of ALT and AST in group A were significantly higher than those of group B (P<0.001).Most of the tumors (35/36) were demonstrated as low density or isodensity lesions on plain CT. Tumors enhancement began during the arterial phase and continued through the early portal phase, showed obviously peripheral cricoid enhancement, and plateaued during the mid portal phase, appeared to change minimally in equilibrium phase. One model(2.78%,1/36) showed slightly low density on plain CT, it demonstrated no enhancement in arterial phase, laminated enhancement higher than the normal hepatic parenchyma from early portal phase to equilibrium phase, and seen the portal vein branch to enter the tumor. Lipiodol obviously deposition in tumor peripheral and still could be seen the surviving area after 1 week in group A.The DSA demonstrated that the blood supplies in 31 rabbit were the hepatic artery. On hepatic angiography, the feeding artery of tumors were obviously thickening ,the vascular of lump area were increased and disordered, the tumors were revealed by congregation of contrast medium as homogeneous or cricoid. No congregation of contrast medium on portal angiography. Although less blood supply of 4 rabbits showed no obviously tumor staining on DSA, but one week after the lipiodol still can be seen deposited within the tumor. One model was demonstrated the blood supply from portal vein on DSA, which was showed the lump area hepatic artery branch sparsely and portal vein branch increased and disordered, could saw the tumor staining on portal angiography. In day 22, the DSA performance was similar to the day 15 except the increased tumors'volume in group B. 20 rabbits were survived after THAE in group A. On artery angiography the tumor vascellum were of angiostenosis or occlusion, anomalous dyeing located at tumor peripheral. And congregation of contrast medium had not been shown on portal angiography.Immunohistochemistry showed that the positive rate of the VEGF expression of tumor peripheral which was 43.38±19.65 in group B and 43.18±14.01 in group C. There was no significant statistical difference between the two groups (F=0.450, t=0.020, P=0.985). In group A, the tumor was mainly composed by coagulability necrosis and the peripheral survival cancerous tissue. The treatment of lipiodol embolization significantly increased the expression of VEGF protein, the positive rate of its was 62.04±19.91, there were remarkable differences among three groups (F=3.664, P=0.038). There was the most intensive angiogenesis in tumor peripheral and survival cancerous tissue, especially at the region of the incomplete involucrum. The MVD counting of the tumors was 28.69±5.43 in group B and 28.71±5.68 in group C. There was no significant statistical difference between the two groups (F=0.000, t=0.006, P=0.995). However, it was 39.26±6.80 in group A, higher than the others, there were very significant statistically differences among three groups (F=10.209, P=0.000). The expression of VEGF and tumor angiogenesis had a better distribution of consistency. Moreover, there was a obvious positive correlation (r=0.457, P=0.009) between the positive rate of the VEGF expression and the MVD counting.Conclusion (1) The improved method adopted in the establishment of the rabbit VX2 liver cancer model was easier in operation and more successful than the traditional method. And it was more stable and suitable for the experiment. (2) The majority of rabbit VX2 liver cancer was hypervascular, which supplied mainly by the hepatic artery, only 2.78% by the portal vein. After THAE with lipiodol, the blood supply of the survival cancerous tissue still was from the hepatic artery, not from portal vein. (3) The arterioportant communications in tumor peripheral played an important role in the blood supply of hepatic tumors. The portal vein within tomur was merely flowed through in the anatomy, which did not involved in tumor blood supplying. It is necessary to strengthen the portal vein chemoembolization in order to block the communication channels. Moreover, liver cancer supplied from the portal vein should be treated with the portal vein embolization. (4) The hypoxia condition in the survival cancerous tissue of tumor induced the expression of VEGF and MVD after embolization, it was significantly higher than before embolization. There was a obvious positive correlation between the positive rate of VEGF expression and the MVD counting. The VEGF expression may play a vital role in the reconstruction of the tumor's blood supply after THAE. Therefore, it is necessary to strengthen antiangiogenesis therapy in liver tumor.