A gene made by joining parts of two different genes. Fusion genes, and the fusion proteins that come from them, may be made in the laboratory, or made naturally in the body when part of the DNA from one chromosome moves to another chromosome. Fusion proteins produced by this change may lead to the development of some types of cancer. For example, the BCR-ABL fusion gene and protein are found in some types of leukemia. Fusion genes and proteins may also be found in several other types of cancer, including soft tissue sarcoma, cancers of the prostate, breast, lung, bladder, colon, and rectum, and CNS tumors. Fusion genes and proteins are being studied in the diagnosis and treatment of cancer.