An AMPK agonist suppresses the progress of colorectal cancer by regulating the polarization of TAM to M1 through inhibition of HIF-1 and mTOR signal pathway

Objective:This study aimed to evaluate the impact of an adenosine monophosphate-activated protein kinase (AMPK) agonist, metformin (MET), on the antitumor effects of macrophages and to determine the underlying mechanism involved in the process.Materials and Methods:M0 macrophages were derived from phorbol-12-myristate-13-acetate-stimulated THP-1 cells.Results:The levels of tumor necrosis factor-alpha (TNF-alpha) and human leukocyte antigen-DR (HLA-DR) were decreased in macrophages incubated with HCT116 cells, whereas those of arginase-1 (Arg-1), CD163, and CD206 were elevated; these effects were reversed by MET. The transfection of small interfering (si) RNA abrogated the influence of MET on the expression of the M1/M2 macrophage biomarkers. MET significantly suppressed the proliferation and migration abilities of HCT116 cells incubated with M0 macrophages; these actions were reversed by siRNA transfection against AMPK. The hypoxia-inducible factor 1-alpha (HIF-1 alpha), phosphorylated protein kinase B (p-AKT), and phosphorylated mammalian target of rapamycin (p-mTOR) levels were reduced by the introduction of MET and promoted by siRNA transfection against AMPK. In addition, the levels of HIF-1 alpha, p-AKT, and p-mTOR suppressed by MET were markedly increased following the transfection of siRNA against AMPK.Conclusion:These findings indicate that MET can repress the progression of colorectal cancer by transforming tumor-associated macrophages to the M1phenotype via inhibition of the HIF-1 alpha and mTOR signaling pathways.