# Aberrant CD25 and Increased CD123 Expression Are Common in Acute Myeloid Leukemia with KMT2A Partial Tandem Duplication and Are Associated with FLT3 Internal Tandem Duplication

## TL;DR

This study identifies abnormal CD25 and increased CD123 as common features in a specific type of leukemia linked to poor outcomes, offering potential new diagnostic and treatment targets.

## Contribution

The study reveals novel immunophenotypic markers (CD25 and CD123) associated with FLT3-ITD mutations in KMT2A-PTD AML.

## Key findings

- Aberrant CD25 and increased CD123 expression are common in AML with KMT2A-PTD.
- CD25 and CD123 expression are significantly associated with FLT3-ITD mutations.
- These markers may serve as useful diagnostic and therapeutic targets in this AML subtype.

## Abstract

Acute myeloid leukemia (AML) with KMT2A partial tandem duplication (PTD) is associated with poor prognosis, but its immunophenotype has not been well defined. We studied 47 AML cases with KMT2A-PTD confirmed by optical genome mapping. Most cases showed a relatively simple karyotype and frequent mutations in FLT3-ITD, DNMT3A, and RUNX1 by next-generation sequencing. Immunophenotypic analysis revealed that blasts commonly expressed CD34, CD117 and HLA-DR, with frequently aberrant CD25 and increased CD123 expression. CD25 and increased CD123 expression were significantly associated with FLT3-ITD mutations, but not with other common mutations. These findings identify distinctive immunophenotypic features of AML with KMT2A-PTD and suggest that CD25 and CD123 may serve as useful biomarkers and potential therapeutic targets in this AML subtype.

Background: KMT2A partial tandem duplication (PTD) occurs in approximately 5–10% of acute myeloid leukemia (AML) cases and is associated with poor prognosis. While its cytogenetic and molecular features are well described, the immunophenotypic characteristics of AML with KMT2A-PTD remain incompletely defined. Methods: We identified 47 cases of AML with KMT2A-PTD by optical genome mapping. All cases underwent flow cytometric immunophenotypic analysis and next-generation sequencing using an 81-gene panel. Results: The cohort included 32 men and 15 women with a median age of 67 years (range, 19–87). Thirty-eight cases were de novo AML, and nine were secondary to myelodysplastic syndrome and/or myeloproliferative neoplasm. Most cases (93%) demonstrated a normal or non-complex karyotype. The most frequent mutations involved FLT3-ITD (47%), DNMT3A (43%), and RUNX1 (23%). Thirty-one cases (66%) were granulocytic, while 16 (34%) showed granulocytic and/or monocytic differentiation. Blasts uniformly expressed HLA-DR and frequently expressed CD117 (91%) and CD34 (79%). Increased expression of CD123 (74%) and CD117 (43%) and decreased expression of HLA-DR (74%) and CD38 (69%) were common. Aberrant CD25 expression was observed in 51% of cases. Increased CD123 and aberrant CD25 expression were significantly associated with FLT3-ITD mutations (both p < 0.0001) but not with other recurrent mutations. There was no correlation between FLT3-ITD mutation and expression levels of CD117, CD38 or HLA-DR (all p > 0.05). Conclusions: AML with KMT2A-PTD shows distinctive immunophenotypic features with increased CD123 and aberrant CD25 expression, both associated with FLT3-ITD. These markers may have diagnostic and therapeutic relevance in this AML subtype.