While serum HMGB1 concentrations in naïve C57Bl/6 and Balb/c were 7.65 ng/mL and 8.51 ng/mL, respectively, the concentrations in untreated B16F10 and 4T1 tumor-bearing mice were approximately a threefold increased, which further escalated over time. Here, HMGB1 is linked to neoplasm.