Evaluation of combined therapy with chemoembolization and irradiation for large hepatocellular carcinoma

Mechanism of 5-fluorouracil required resistance in human hepatocellular carcinoma cell line Bel7402

AIM: To investigate the resistance mechanism of 5-fluorouracil (5-FU) in Bel₇₄₀₂/5-FU cells which was established in our lab by in vitro continuous stepwise exposure of human hepatocellular carcinoma (HCC) cell line Bel₇₄₀₂ to 5-FU.

METHODS: The expression of multidrug resistance-associated protein (MRP) and thymidylate synthase (TS) in Bel₇₄₀₂ cells was detected by immonocytochemistry. The fluorescein (FLU) accumulation, an index of MRP functional activity, was determined by flow cytometry. The distribution of FLU was observed by confocal laser scanning microscope. The spectrofluorometry was used to show the intracelluar content of glutathione (GSH). Cell growth inhibition was determined by MTT assay. The activity of glutathione S-transferases (GSTs) was determined by spectrophotometry.

RESULTS: A higher expression of MRP in the Bel₇₄₀₂/5-FU cells was observed by using monoclonal mouse anti-MRP antibody, MRPr-1, in comparison with Bel₇₄₀₂ cells. Bel₇₄₀₂/5-FU cells also showed a significant decrease of FLU accumulation. FLU mainly accumulated in the nucleus with a high nuclear/cytoplasmic ratio in Bel₇₄₀₂ cells, whereas there was no difference of FLU accumulation between the nucleus and cytoplasm in Bel₇₄₀₂/5-FU cells. The intracellular GSH content in Bel₇₄₀₂/5-FU cells was almost 3 folds higher than that in Bel₇₄₀₂ cells. Addition of D, L-buthione-S, R-sulfoximine (BSO) dose-dependently reduced the GSH content in Bel₇₄₀₂/ 5-FU cells, however, only a weak enhancement on the cytotoxicity of 5-FU and doxorubicin (Dox) to Bel₇₄₀₂/5-FU cells was observed. Bel₇₄₀₂/5-FU cells also exhibited 29.1% higher total GSTs activity than Bel₇₄₀₂ cells. Immunocytochemical staining by using anti-TS monoclonal antibody TS 106 showed that the level of TS in Bel₇₄₀₂/5-FU cells elevated markedly as compared with Bel₇₄₀₂ cells.

CONCLUSION: The continuous exposure of Bel₇₄₀₂ cells to 5-FU led to overexpression of TS and MRP, as well as increased intracellular GSH content and total GST activity.

Influence of hepatic arterial blockage on blood perfusion and VEGF, MMP-1 expression of implanted liver cancer in rats

AIM: To investigate the influence of hepatic arterial blockage on blood perfusion of transplanted cancer in rat liver and the expression of vascular endothelial growth factor (VEGF) and matrix metalloproteinase-1 (MMP-1), and to explore the mechanisms involved in transarterial embolization (TAE)-induced metastasis of liver cancer preliminarily.

METHODS: Walker 256 carcinosarcoma was transplanted into rat liver to establish the liver cancer model. Hepatic arterial ligation (HAL) was used to block the hepatic arterial blood supply and simulate TAE. Blood perfusion of tumor in control, laparotomy control, and HAL group was analyzed by Hoechst 33342 labeling assay, the serum VEGF level was assayed by ELISA, the expression of VEGF and MMP-1 mRNA was detected by in situ hybridization.

RESULTS: Two days after HAL, the number of Hoechst 33342 labeled cells which represent the blood perfusion of tumor directly and hypoxia of tumor indirectly in HAL group decreased significantly compared with that in control group (329 ± 29 vs 384 ± 19, P < 0.01). The serum VEGF level in the HAL group increased significantly as against that of the control group (93 ng·L^-1± 44 ng·L^-1vs 55 ng·L^-1± 19 ng·L^-1, P < 0.05). The expression of VEGF and MMP-1 mRNA in the tumor tissue of the HAL group increased significantly compared with that of the control and the laparotomy control groups (P < 0.05). The blood perfusion data of the tumor, represented by the number of Hoechst 33342 labeled cells, showed a good linear inverse correlation with the serum VEGF level (r = -0.606, P < 0.05) and the expression of VEGF mRNA in the tumor tissue (r = -0.338, P < 0.01).

CONCLUSION: Blockage of hepatic arterial blood supply results in decreased blood perfusion and increased expression of metastasis-associated genes VEGF and MMP-1 of transplanted liver cancer in rats. Decreased blood perfusion and hypoxia may be the major cause of up-regulated expression of VEGF.