Figure 3.

Metformin blocks MYC protein synthesis in standard culture conditions. (A,B) Metformin‐induced MYC reduction is neither rescued by the proteasome inhibitor MG132, nor accelerated by the protein synthesis inhibitor CHX in HCT116 cells (A) and in HT29 cells (B). In A and B, cells were treated with metformin for 24 h (10 mm), in the presence or absence of MG132 (10 μM). (C,D) Metformin does not enhance the MYC phosphorylation at threonine 58 in 24 h treatment (C) or in colony formation samples (D). (E) Metformin does not reduce luciferase activity of MYC 3′UTR reporter, at the condition of causing MYC protein level changes. Cells were treated with metformin (5 mm, 10 mm) for 24 h, and culture medium was analyzed using the Secrete‐Pair™ Dual Luminescence Assay Kit.