An example is only f-circM9 to be produced from the fusion region of MLL-AF9 gene in leukemia; however, in MLL-rearranged leukemia, the MLL gene can be fused with one of over 100 partners, including AF4, AF9, and ENL, to form more than 100 MLL fusion genes [28]. The gene discussed is AFF1; the disease is leukemia.