In vivo antitumour activity of PBMCs via genetic modification of single-chain immunotoxin

Anti-hepatoma effect and its mechanism of arsenic trioxide on experimental liver cancer

AIM: To study the synergistic anti-hepatoma efficacy of arsenic trioxide (As₂O₃) and matrine in the treatment of experimental rat hepatocellular carcinoma (HCC) induced by 2-acetamidofluorene (2-FAA) and to elucidate the possible mechanisms.

METHODS: SD rats (2 mo old) were fed with 2-FAA for 8 weeks to induce HCC, then treated with As₂O₃ and matrine. On day 29, we weighed the liver and counted liver tumors. The histological changes of the liver were observed under microscope, and the cellular dynamic parameters were studied by flow cytometry. Immunohistochemistry (two-step method) was used to observe the expression of vascular endothelial growth factor (VEGF) and to show micro-vessel density (MVD) on consecutive sections. The pathological parameters were analyzed at the same time. The levels of serum AST, ALT, TBi and DBi were also investigated.

RESULTS: The number of liver tumors decreased significantly in groups treated with As₂O₃, especially in middle-dose (1 mg/kg) group (P < 0.01). Treatment with As₂O₃ caused HCC cell death via apoptosis. Necrosis was seldomly found and apoptosis was common when the dose was appropriate (1 mg/kg). Proliferation index (PI) decreased sharply in middle-dose (1 mg/kg) group (P < 0.01), but not in another (0.2 mg/kg) group (P > 0.05). However, S phase fraction (SPF) decreasd dramatically in the two groups, it reached the top only when the dose (1 mg/kg) was appropriciate (P < 0.01), and it was obviously accompanied with accumulation of cells in G₀/G₁ (G₀/G₁ restriction). The inhibitory effects of As₂O₃ on HCC cells were not significantly enhanced by matrine. Comparied with single treatment with As₂O₃ 1 mg/kg or 0.2 mg/kg, G₀/G₁ phase cells in the group of combination treatment with As₂O₃ 1 mg/kg or 0.2 mg/kg and matrine 4.2 g/kg did not increased, and apoptostic cells with fractional DNA content did not increased either. The expression of VEGF and MVD was significantly lower in middle-dose (1 mg/kg) group (P < 0.01) than that in normal saline group. In comparison with normal saline group, administration of As₂O₃ or/and matrine lowered the levels of AST in serum (P < 0.05), but had no effect on the amount of serum AST, TBi and DBi (P > 0.05).

CONCLUSION: Arsenic trioxide inhibits growth of experimental hepatocellular carcinoma in rats induced by 2-acetamidofluorene, but As₂O₃ has no obvious effect on the normal hepatic cells. The mechanisms may involved in decreasing cell mitosis, accumulating cells in G₀/G₁ phrase, inducing apoptosis of tumer cells, and having inhibitory effects on the angiogeninase through inhibiting vascular endothelial growth factor. Matrine with As₂O₃ has not significantly synergistic anti-hepatoma effects.