To verify whether the inhibitory effect of metformin on xenograft tumor growth was mediated by inhibiting the urea cycle and decreasing ODC1 levels, the levels of AMPK, p-AMPK, p53, ARG1, CPS1, OTC, p21, and ODC in HCT116 xenografts were assayed using Western blotting. This evidence concerns the gene CPS1 and neoplasm.