Described are methods of treating a cancer comprising administering to a subject in need thereof an effective amount of a dopamine receptor (DR) antagonist. The DR antagonist may be a phenothiazine derivative, such as thioridazine or chlorpromazine. Optionally, the cancer is acute myeloid leukemia. Also described are methods for identifying subjects with cancer, methods for providing a prognosis for a subjects with cancer and methods for identifying subjects likely to be responsive to therapy with DR receptor antagonists. Methods for identifying cancer stem cells and chemotherapeutic compounds that are DR receptor antagonists as also provided. Also described are methods for the identification and validation of agents that target cancer stem cells.
