Abstract Chromosome 8 (chr8) gain, particularly the gain of its long arm 8q, represents one of the most frequent chromosomal abnormalities across multiple human cancers. In Ewing sarcoma, approximately 50% of cases exhibit chr8 gain while in prostate cancer, high level amplification of 8q occurs in about 24% of primary cases with much higher frequencies in metastatic cases. Across both diseases, the cohesin subunit gene RAD21, located on 8q24.11 region, has emerged as a key driver that facilitat