Identification of RNPC3 as a novel JAK2 fusion partner gene in B-acute lymphoblastic leukemia refractory to combination therapy including ruxolitinib

BACKGROUND:

Hematopoietic neoplasms with chromosomal translocations involving JAK2 are rare, and most of them show myeloproliferative neoplasm-associated features, followed by B-acute lymphoblastic leukemia (B-ALL). De novo B-ALL cases with JAK2 rearrangements are suggested to be appropriately considered as BCR-ABL1-like B-ALL, but its partners varied.

METHODS:

Fluorescence in situ hybridization (FISH), RNA sequencing (RNA-Seq), whole-genome sequencing, and reverse transcription polymerase chain reaction (RT-PCR) were performed to identify the pathogenic fusion gene in a 29-year-old woman with relapsed B-ALL and rare t(1;9)(p13;p22) translocation.

RESULTS:

We identified RNPC3 as a new JAK2 fusion partner in the patient. She was treated with a combination of chemotherapy and targeted drug ruxolitinib and chimeric antigen receptor T-cell therapy, but failed to achieve complete remission. She had no chance to undergo allogeneic hematopoietic stem cell transplantation and died of disease progression 7 months after the initial diagnosis. Her clinical course demonstrated that this novel RNPC3-JAK2 fusion might portend an unfavorable prognosis.

CONCLUSION:

This finding adds to the expanding compendium of JAK2 fusions found in B-ALL and suggests the potential need for a diagnostic FISH analysis as well as RNA-Seq in the appropriate clinical setting.

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