Complete Loss of the RUNX1 Gene: A Review of the Implications for Leukemogenesis and Patient Management

The RUNX1 (AML1) gene is a transcription factor that regulates expression of genes involved in hematopoietic cell differentiation. It is a gene located on chromosome 21 at q22. Genetic alterations of RUNX1 whether through loss-of-function point mutations, translocation or amplification are known to impact myeloid differentiation and trigger leukemic transformation in particular with respect to myelodysplasia and acute myeloid leukemia. However, while there are many articles describing the impact of these types of RUNX1 genetic alterations, there is a paucity of information regarding loss of the entire RUNX1 gene. The case in this abstract highlights the significance of understanding loss of the RUNX1 gene. An 87 year old patient presented for evaluation for anemia and leukopenia. Flow cytometric evaluation revealed 26% myeloid blasts and confirmed a diagnosis of acute myeloid leukemia (AML). The cytogenetic findings demonstrated a translocation between chromosomes 17 and 21 −t(17;21)(q11.2;q22). The dilemma then was to determine if this was a variant of the traditional t(15;17) associated with acute promyelocytic leukemia or a variant of the t(8;21) associated with the M2 subtype of AML. FISH studies determined that there was no involvement of the RARA gene and no evidence of a RUNX1/ETO rearrangement. However, there was a complete loss of RUNX1 on the abnormal chromosome 21. Thus, what appeared to be a balanced translocation included a cryptic loss of RUNX1. While this may be an interesting case presentation the more pertinent question is what is the impact of the RUNX1 loss? This case prompted a review of the data on complete loss of the RUNX1 gene which while limited suggests that RUNX1 loss on its own is not leukemogenic. This poster presents the data and implication of complete loss of RUNX1, the role of this loss in leukemogenesis and patient management.