Metformin treatment mitigated tumor growth, with accompanying alleviations seen in body mass, fasting glucose, fasting insulin, insulin resistance, circulating WBCs, lymphocytes, neutrophils, plasma leptin, soluble P-selectin, TGF-β1 and HMGB1, as well as the tumor signaling molecules of cyclin D1, β-catenin, HMGB1, RAGE, Akt phosphorylation, Smad2/3 phosphorylation, GLUT1, PKM2, SLC1A5, SLC7A5, glutaminase, CD62P and MPO, while elevation occurred in circulating glutamine. The gene discussed is MPO; the disease is neoplasm.