Sirolimus increases the anti-cancer effect of Huai Er by regulating hypoxia inducible factor-1α-mediated glycolysis in hepatocellular carcinoma

Abstract

Background: Glycolysis caused by hypoxia-induced abnormal activation of hypoxia inducible factor-1α (HIF-1α) in the immune microenvironment promotes the progression of hepatocellular carcinoma (HCC), leading to enhanced drug resistance in cancer cells. Therefore, altering the immunosuppressive microenvironment by imp-roving the hypoxic state is a new goal in improving cancer treatment.

Aim: To analyse the role of HIF-1α, which is closely related to tumour proliferation, invasion, metastasis, and angiogenesis, in the proliferation and invasion of liver cancer, and to explore the HIF-1α pathway-mediated anti-cancer mechanism of sirolimus (SRL) combined with Huai Er.

Methods: Previous studies on HCC tissues identified the importance of HIF-1α, glucose transporter 1 (GLUT1), and lactate dehydrogenase A (LDHA) expression. In this study, HepG2 and Huh7 cell lines were treated, under hypoxic and normoxic conditions, with a combination of SRL and Huai Er. The effects on proliferation, invasion, cell cycle, and apoptosis were analysed. Proteomics and genomics techniques were used to analyze the HIF-1α-related signalling pathway during SRL combined with Huai Er treatment and its inhibition of the proliferation of HCC cells.

Results: High levels of HIF-1α, LDHA, and GLUT-1 were found in poorly differentiated HCC, with lower patient survival rates. Hypoxia promoted the proliferation of HepG2 and Huh7 cells and weakened the apoptosis and cell cycle blocking effects of the SRL/Huai Er treatment. This was achieved by activation of HIF-1α and glycolysis in HCC, leading to the upregulation of LDHA, GLUT-1, Akt/mammalian target of rapamycin (mTOR), vascular endothelial growth factor (VEGF), and Forkhead box P3 and downregulation of phosphatase and tensin homolog deleted on chromosome ten (PTEN) and p27. The hypoxia-induced activation of HIF-1α showed the greatest attenuation in the SRL/Huai Er (S50 + H8) group compared to the drug treatments alone (P < 0.001). The S50 + H8 treatment significantly downregulated the expression of mTOR and HIF-1α, and significantly reduced the expression of VEGF mRNA. Meanwhile, the combined blocking of mTOR and HIF-1α enhanced the downregulation of Akt/mTOR, HIF-1α, LDHA, and GLUT-1 mRNA and resulted in the downregulation of PTEN, p27, and VEGF mRNA (P < 0.001).

Conclusion: SRL increases the anti-cancer effect of Huai Er, which reduces the promotion of hypoxia-induced HIF-1α on the Warburg effect by inhibition of the PI3K/Akt/mTOR-HIF-1α and HIF-1α-PTEN signalling pathways in HCC.

Keywords: Hepatocellular carcinoma; Huai Er; Hypoxia inducible factor-1α; Sirolimus; Warburg effect.