The present invention relates to enhancing, modulating or stimulating the immune response to MMP-2 expressing tumors, including melanoma, and to the modulation and application of immune modulators and MMP-2 peptides for melanoma or other MMP-2 expressing tumor vaccines. The invention provides methods and means to activate an effective response to MMP-2 expressing tumors and modulate the ability of MMP-2 to skew CD4+ T cell responses toward that of TH2 cells, which are less effective mediators of tumor cell clearance than TH1 cells. Methods and assays are provided for screening for compounds, agents, or peptides capable of enhancing or activating immune responses, particularly to melanoma.