The impact of Down syndrome‐specific non‐malignant hematopoietic regeneration in the bone marrow on the detection of leukemic measurable residual disease

Abstract

BackgroundDetection of measurable residual disease detection (MRD) by flow cytometry after the first course of chemotherapy is a standard measure of early response in patients with acute myeloid leukemia (AML). Myeloid leukemia associated with Down Syndrome (ML‐DS) is a distinct form of AML. Differences in steady‐state and regenerating hematopoiesis between patients with or without DS are not well understood. This understanding is essential to accurately determine the presence of residual leukemia in patients with ML‐DS.MethodsA standardized antibody panel defined quantitative antigen expression in 115 follow‐up bone marrow (BM) aspirates from 45 patients following chemotherapy for ML‐DS or DS precursor B‐cell acute lymphoblastic leukemia (B‐ALL‐DS) with the “difference from normal (ΔN)” technique. When possible, FISH and SNP/CGH microarray studies were performed on sorted cell fractions.Results93% of BM specimens submitted post chemotherapy had a clearly identifiable CD34+CD56+ population present between 0.06% and 2.6% of total non‐erythroid cells. An overlapping CD34+HLA‐DRheterogeneous population was observed among 92% of patients at a lower frequency (0.04%–0.8% of total non‐erythroid cells). In B‐ALL‐DS patients, the same CD34+CD56+ HLA‐DRheterogeneous expression was observed. FACS‐FISH/Array studies demonstrated no residual genetic clones in the DS‐specific myeloid progenitor cells.ConclusionsNon‐malignant myeloid progenitors in the regenerating BM of patients who have undergone chemotherapy for either ML‐DS or B‐ALL‐DS express an immunophenotype that is different from normal BM of non‐DS patients. Awareness of this DS‐specific non‐malignant myeloid progenitor is essential to the interpretation of MRD by flow cytometry in patients with ML‐DS.

Leukemogenesis in Acute Lymphoblastic Leukemia through the Lens of Developmental Dynamics of Lymphoid Progenitor Cells: a systematic review

“…GATA1 directly regulates CD34 expression, and mutations in GATA1 can disrupt its regulatory function, leading to altered CD34 levels [120]. Dysregulated CD34 expression due to GATA1 mutations, compounded by potential dosage effects in DS, may disrupt normal lymphoid development, promoting the development of ALL by altering the balance between myeloid and lymphoid lineage commitment [121]. Moreover, dysregulated CRLF2 signaling in DS-ALL can impact CD34 expression indirectly by altering signaling pathways involved in its regulation.…”