Fig. 5.

The pro-inflammatory activities of CSF2-activated macrophages are blunted by tumor-derived lactate. a–c Relative lactate production in the media of the indicated cells (n = 3). d Macrophages were obtained by culture of monocytes in culture medium in the presence or absence of 20 ng/ml CSF2 for 6 days. Afterward, macrophages were cultured in a culture medium with or without 5 mM lactate for 24 h. Cytokine levels in the media were measured by ELISA (n = 3 independent experiments using macrophages from three different donors). e SW620 cells were cultured in the presence or absence of 2 mM sodium dichloroacetate (DCA) for 72 h. CM was collected after the cells were cultured for another 24 h without DCA. In addition, the lactate level in CM obtained from SW620 cells treated with DCA was adjusted to the levels in untreated SW620 CM by the addition of lactate. Macrophages were obtained by culture of monocytes in culture medium in the presence or absence of the indicated SW620 CM for 6 days. The cytokine concentrations of the macrophages were measured afterward (n = 3 independent experiments using macrophages from three different donors). *p ≤ 0.05, **p ≤ 0.01, and ***p ≤ 0.001, by one-way ANOVA (a, b, e) or two-tailed Student’s t-test (c, d)