The present inventors found that a fusion gene present in some cancer patients is an oncogene. The present invention relates to a polypeptide as a novel fusion protein, a polynucleotide encoding the polypeptide, a vector comprising the polynucleotide, a transformed cell comprising the vector, a method for detecting the fusion protein or polynucleotide, a method for screening a therapeutic agent for cancer, and a method for treating cancer that is shown to be positive for the fusion gene. Further, the present invention relates kit, primer set, and probe useful in the detection of cancer that is shown to be positive for the fusion gene.