Abstract: Presently disclosed are methods of treating cancer comprising administering a MEK inhibitor in combination with a proteasome inhibitor. In some embodiment, the cancer is a solid tumor. In some instances, the cancer has at least one mutation chosen from a NF1, RAS (including N-, K-, and H-RAS), RAF (including A-, B-, and C-RAF), and MEK (including MEK1 and MEK2) mutation. In some embodiments, the cancer is resistant to treatment with at least one of a proteasome inhibitor or a MEK inhibitor. In some embodiments, the combination therapy produces a synergistic effect.