infection downregulates hypoxia‑inducible factor 1α expression to suppress the vascularization and tumorigenesis of liver cancer.

Liver cancer is characterized by hypervascularization. Anti-angiogenic agents may normalize the tumor vasculature and improve the efficacy of other treatments. The present study aims to investigate the anti-angiogenic effect of infection in a mouse model of implanted liver cancer cells. HepG2 cells were injected into the left liver lobe of nude mice as a model of hepatic tumorigenesis. parasitized erythrocytes were administered in the animal model of liver cancer to introduce infection. The tumor growth and microvascular density were determined in the presence or absence of infection. The expression levels of hypoxia-inducible factor 1α (HIF-1α) and angiogenesis-related factors were evaluated using western blotting and reverse transcription-quantitative PCR analysis. The results demonstrated that infection suppressed tumor growth and vascularization in the mouse model of implanted HepG2 cells. parasites reduced the expression of pro-angiogenic factors (vascular endothelial growth factor A and angiopoietin 2), matrix metalloproteinases [(MMP)2 and MMP9] and inflammatory cytokines [tumor necrosis factor α, interleukin 6 (IL)-6) and IL-1β] in both hepatic and tumor tissues. HIF-1α was downregulated in both hepatic and tumor tissues upon infection, and HIF-1α overexpression rescued angiogenesis and tumor growth under the condition of infection. In conclusion, the results of the present study demonstrated the anti-angiogenic and anti-tumorigenic effects of infection on liver cancer through downregulating HIF-1α expression, indicating that parasites could be developed as an intervention strategy to restrain neo-angiogenesis in liver cancer.