AFF1 and acute lymphoblastic leukemia: A reverse fusion was also demonstrated as possible—namely, AF4-MLL—which resulted in a protein product having the capacity to induce acute lymphoblastic leukemia (ALL) by promoting transcription elongation in mice or murine hematopoietic progenitor/stem cells through interactions with DOT1L, P-TEFb (Pol II-positive transcription elongation factor), and other core subunits of the MLL-FP complexes.