A method of treating a mammalian subject with cancer comprises administering to said subject having a cancer, e.g., a metastatic or refractory cancer or tumor, a small molecule inhibitor of a target signaling molecule of the MEK/MAPK pathway that impairs T cell activation, and administering to said subject a molecule that induces T cell proliferation in the presence of said inhibitor. The combination of a small molecule inhibitor of a target of the MEK/MAPK pathway and the T cell proliferation inducer reduces the proliferation of the cancer and tumor cells in vivo. Compositions and kits including these components are also provided.