This invention encompasses combination therapies including TCN, TCN-P, TCN-PM and/or related compounds and one or more additional anti-cancer agents, for example, taxanes a molecule that modulates the HER2/neu (erbB2) receptor, anthracyclin compounds, epidermal growth factor receptor inhibitor compounds, one or more platinum compounds and bortezomib and derivatives thereof and compositions with reduced toxicity for the treatment and prevention of tumors, cancer, and other disorders associated with abnormal cell proliferation.