The invention provides a method for treating cancers that are dependent on cyclin D1 for proliferation, survival, metastasis and differentiation, involving administering a composition containing an effective amount of arsenic trioxide to an affected patient. The arsenic trioxide can be administered orally, for example, as a solution, suspension, syrup, emulsion, tablet, or capsule. The composition can also contain one or more pharmaceutically acceptable carriers and/or excipients.