CD4 and neoplasm: To further investigate whether CD4+Foxp3+ cells induced by metformin in tumor-bearing mice were producing IL-10, CD4+ T cells were purified from the spleen of Foxp3-gfp knock-in mice and stimulated with phorbol myristate acetate (PMA) and ionomycin, followed by measurement of intracellular IL-10 levels (Figure 7D).