Recent significant progress in the melanoma research affords us to hypothesizing that antitumor immune responses initiated by the tumor vaccine B16F10/GPI-IL-21 might lead to the suppression of the B16F10 cell proliferation or apoptosis, and that this, however, does not completely block the B16F10 cell metastasis in mice [7, 8]. Here, IL21 is linked to melanoma.