The present invention relates to therapeutic compositions for treating cancer or preventing the growth of cancer cells, e.g., tumor growth, in a subject. The present invention also relates to methods for treating cancer, e.g., inhibiting tumor growth, in a subject who has become resistant to treatment, by administering to a subject an effective amount of a proteasome inhibitor and an effective amount of a therapeutic agent, e.g., a chemotherapeutic agent. The present invention further relates to methods for purging bone marrow, i.e., removing cancer cells from bone marrow, by exposing the bone marrow cells to a proteasome inhibitor and a therapeutic agent, e.g., a chemotherapeutic agent.
