Long‐term molecular remission in a patient with acute myeloid leukemia harboring a new NUP98‐LEDGF rearrangement

A large variety of molecular rearrangements of the NUP98 gene have been described in the past decades (n = 72), involving fusion partners coding for different transcription factors, chromatin modifying enzymes, as well as various cytosolic proteins. Here, we report the case of an AML‐M2 patient with a variant NUP98‐LEDGF/PSIP1 gene fusion (N9‐L10). In this patient, three different NUP98-LEDGF fusion mRNAs were characterized due to alternative splicing in LEDGF exon 11. Targeted high‐throughput sequencing revealed the presence of IDH1, SRSF2, and WT1 additional pathogenic mutations. To improve the therapeutic monitoring, quantification of NUP98‐LEDGF mRNA by real‐time PCR was developed. Because of poor response to conventional chemotherapy, allogeneic stem cell transplantation was performed, followed by 20 cycles of azacitidine‐based preemptive treatment of relapse. More than 31 months after diagnosis, corresponding to 25 months post SCT and 4 months after the last cycle of azacytidine, the patient is in complete molecular remission (undetectable NUP98‐LEDGF mRNA transcripts). This study highlights the considerable variability in breakpoint location within both NUP98 and LEDGF, associated with alternative splicing affecting LEDGF. It also emphasizes the need to fully characterize the breakpoints within the two genes and the identification of all fusion mRNAs, particularly for the development of a molecular monitoring assay. All these data seem critical for the optimal management of NUP98‐LEDGF + hematological malignancies commonly associated with a poor prognosis.