Metformin Enhances the Effect of Regorafenib and Inhibits Recurrence and Metastasis of Hepatic Carcinoma After Liver Resection via Regulating Expression of Hypoxia Inducible Factors 2α (HIF-2α) and 30 kDa HIV Tat-Interacting Protein (TIP30).

BACKGROUND Regorafenib (RGF) is the drug of choice for treating hepatic carcinoma (HCC), but the drug has drawbacks due to resistance and associated adverse effects. Thus, it becomes crucial to understand the causal 'map' of the resistance conferred by RGF, so that its clinical potency can be amplified, resulting in enhanced efficacy with reduced adverse effects. Metformin (MTF) has been reported to target NLK (Nemo-like kinase) to inhibit non-small lung cancer cells. Based on the literature, the present investigation was carried out to reveal the effect of RGF and MTF, with an expectation that MTF can synergize therapeutic potential as well reduce chances of resistance. MATERIAL AND METHODS Protein expression of hypoxia inducible factors (HIF)-2α, 30 kDa HIV Tat-interacting protein (TIP30), E-cadherin, N-cadherin, and pAMPK were assessed by Western blot analysis. RGF and MTF were exposed to MHCC97H cell and proliferation was quantified by assay of cell viability. Gene silencing and chromatin immunoprecipitation assay were done to reveal the relationship between TIP30 and HIF-2α. The impact of RGF and MTF together on postoperative recurrence and lung metastasis of hepatocellular carcinoma was investigated using tumor engrafted mice after administration of MTF and RGF once daily for 35 days. Immunohistochemistry was used to reveal CD31, Ki67, and TUNEL. RESULTS The results suggested MTF-RGF combination lowered expression of HIF-2α gene silencing and suggested increased TIP30 after reduction of HIF-2α. The chromatin immunoprecipitation study indicated that under hypoxia, HIF-2α could bind with TIP30 promoter. Cell number quantification (CCK8), viable cell count, and apoptosis data (using Annexin V-FITC) indicated co-administration of RGF and MTF reduced cell proliferation, encouraging cell apoptosis, and reduced epithelial-mesenchymal transition course. Thus, in orthotopic mice, the RGF-MTF combination exhibited substantial reduction of HCC in lung metastasis and postoperative relapse. CONCLUSIONS MTF can enhance the potential of RGF and inhibit the recurrence and metastasis of HCC after postoperative liver section by regulating the levels of TIP30 and HIF-2α.