Search

Despite the absence of mutations in the DNA repair machinery in myeloid malignancies, the advent of high-throughput sequencing and discovery of splicing and epigenetics defects in chronic myelomonocytic leukaemia (CMML) prompted us to revisit a pathogenic role for genes involved in DNA damage response. We screened for misregulated DNA repair genes by enhanced RNA-sequencing on bone marrow from a discovery cohort of 27 CMML patients and 9 controls. We validated 4 differentially expressed candidates in CMML CD34(+) bone marrow selected cells and in an independent cohort of 74 CMML patients, mutationally contextualized by targeted sequencing, and assessed their transcriptional behavior in 70 myelodysplastic syndrome, 66 acute myeloid leukaemia and 25 chronic myeloid leukaemia cases. We found BAP1 and PARP1 down-regulation to be specific to CMML compared with other related disorders. Chromatin-regulator mutated cases showed decreased BAP1 dosage. We validated a significant over-expression of the double strand break-fidelity genes CDKN1A and ERCC1, independent of promoter methylation and associated with chemorefractoriness. In addition, patients bearing mutations in the splicing component SRSF2 displayed numerous aberrant splicing events in DNA repair genes, with a quantitative predominance in the single strand break pathway. Our results highlight potential targets in this disease, which currently has few therapeutic options.

A 32-year-old human immunodeficiency virus (HIV)-positive male presented with fever and some haemorrhagic vesicles on the soft palate. Three years previously, he had been diagnosed with stage IVB, nodular sclerosis Hodgkin lymphoma, treated with six cycles of doxorubicin, bleomycin, vinblastine, dacarbazine (ABVD), and achieved complete remission. On admission, a full blood count showed: white cell count 67AE4 · 10/l, haemoglobin concentration 85 g/l and platelet count 10 · 10/l. Peripheral blood films showed 10% blasts (some with granules), 25% promonocytes and 6% eosinophils. A variable number of Auer rods were observed in some neutrophils and band forms, occasionally being numerous (top). A bone marrow aspirate showed blast cells, promonocytes, monocytes, eosinophils and eosinophil precursors. In addition there were faggot cells – maturing cells of neutrophil lineage containing bundles of Auer rods (bottom). Cytochemical studies showed a proportion of cells positive for myeloperoxidase, chloroacetate esterase and butyrate esterase. Periodic acid–Schiff (PAS) positivity was observed in some atypical eosinophils. Immunophenotypic analysis showed two abnormal populations: the first of these accounted for 15% of the events and showed a CD34+, CD117+, CD33+, CD13++, CD15±, HLA)DR+, CD45+, cMPO+ and lysozyme–phenotype; the second accounted for 60% and showed a CD34), CD117±, CD13+, CD15+, HLA-DR+, CD11b+, CD14+, CD64+, CD36+, CD45++, cMPO± and lysozyme+ phenotype. Interphase fluorescence in situ hybridization analysis revealed inv(16) and excluded t(15;17). Cytogenetic analysis showed 47,XY,+8,inv(16)(p13q22)[20]. Molecular analysis confirmed inv(16) (MYH11-CBFB/ABL1 ratio:12AE47). The final diagnosis was therapy related-acute myeloid leukaemia (AML) with +8 and inv(16). He received two cycles of induction chemotherapy without attaining complete remission. Faggot cells are very characteristic of acute promyelocytic leukaemia but, as illustrated by this patient, they cannot be regarded as specific. They are a very uncommon feature of AML associated with inv(16).