Secretion of immunosuppressive cytokines such as TGFβ, IL‐6 and IL‐10 by tumor, stroma and inflammatory cells have been shown to stimulate Treg proliferation and reduce the efficacy of cancer vaccine.33, 34 Accordingly, neither Tconv/Treg nor CD8/Treg ratios in tumor tissues were significantly changed by DCVacc treatment, implying that DCVacc did not overcome the immune evasion of the B16‐OVA tumor. Here, TGFB1 is linked to cancer.