Compositions and methods for the treatment of cancer, particularly melanoma, myeloma, small cell lung cancer, thymic lymphoma, T-cell lymphoma, B-cell lymphoma, osteosarcoma, and acute T-cell leukemia, are disclosed. Illustrative compositions include one or more anti-ganglioside antibodies and polynucleotides that encode such anti-ganglioside antibodies. These antibodies may be for example, hamster antibodies, chimeric human/hamster antibodies, or humanized antibodies. The disclosed compositions are useful, for example, in the treatment of cancer and can be used to induce apoptosis in a cancer cell.