A Novel t(9;22;11) Translocation Variant Involving 11q23 in a Patient with Chronic Myeloid Leukemia

Background:The progression of Philadelphia chromosome positive chronic myeloid leukemia (CML) is frequently accompanied by cytogenetic evolution, commonly unbalanced chromosomal changes. but balanced chromosomal translocations are very rare in CML, especially translocations involving the 11q23. The few reported cases with blast phase (BP) of CML carrying a 11q23 rearrangement results in insufficient responses to tyrosine kinase inhibitors (TKIs) and possess a poor prognosis.

Methods:Cytogenetic analysis , fluorescence in situ hybridization (FISH), RNA sequencing (RNA-seq), targeted genomic sequencing and multi-parametric flow cytometry analysis were performed to identify the chromosome translocations and pathogenic gene alterations in a 36-year-old female with myeloid BP of CML.

Results: In BP, the bone marrow (BM) aspiration showed 61% myeloid blasts; Multi-parametric flow cytometry analysis revealed the abnormal myeloid blasts expression of the following antigens: CD117, CD13, CD33, CD38, partially expressed CD15, CD64. Chromosome analysis revealed a t(11;22)(q23;q11) translocation in addition to the t(9;22)(q34;q11). Fluorescence in situ hybridization (FISH) test confirmed that the t(11;22)(q23;q11) involved the mixed lineage leukemia(MLL) gene on 11q23 and RNA sequence revealed MLL-SEPT5 and BCR/ABL1(p210) fusion transcripts positive. Mutations on 339 commonly mutated genes in hematologic malignancies were analyzed by targeted next-generation sequencing showed ASXL1 p.G949Vfs*2 mutation.

The patient failed to respond to both imatinib and dasatinib despite the absence of resistance-associated mutations in the BCR/ABL1 gene and she had a myeloid blast crisis at 19 months after initiation of first- and second-generation TKI treatment. After BP, she received ponatinb, a third-generation TKI with chemotherapy. Regretly she didn't achieve a complete remission(CR) and was in the process of salvage transplantation at present.

Conclusions:The presence of 11q23 rearrangements in BC of CML is rare and most likely accounts for the adverse clinical outcome. We first report a patient who diagnosed CML with t(11;22)(q23;q11) and MLL-SEPT5 fusion gene positive in BP of CML. The clinical course was aggressive, and therapy was poorly tolerated.