1. Introduction
Acute myeloid leukemia (AML) is a heterogeneous group of aggressive hematologic malignancies driven by different genetic and epigenetic aberrations. These mutations may promote leukemic cell proliferation, impair differentiation, and enhance cell survival, making AML a particularly challenging disease to treat [
1]. Although extensive research has identified numerous genetic drivers, ongoing studies continue to uncover the role of less common mutations and their interactions, which may offer therapeutic potential.
KDM6A (lysine demethylase 6A) is an epigenetic modulator involved in chromatin remodeling and gene expression [
2]. Variants of
KDM6A result in global epigenetic dysregulation and are associated with diverse cancers, including acute myeloid leukemia (AML). Pre-clinical data indicate that
KDM6A variants are associated with a worse survival in AML, possibly because of repressive H3K27me3 marks, which silence genes critical for hematopoietic differentiation [
3,
4,
5]. However, the impact of
KDM6A variants on the cumulative incidence of relapse in adults with AML in histological remission is untested.
This study aimed to investigate the correlation between
KDM6A mutations and relapse risk in AML. Our preliminary research found that
KDM6A mutations predicted poor outcomes in patients with
RUNX1::RUNX1T1 [
6], so we conducted a subgroup analysis on the
RUNX1::RUNX1T1 subtype. By integrating genomic data, measurable residual disease (MRD) information, and clinical outcomes, we assessed the impact of
KDM6A variants on the cumulative incidence of relapse in 1676 adults with AML in histological remission, including a subgroup of 207 patients with
RUNX1::RUNX1T1 fusion.
2. Materials and Methods
2.1. Participants
Data from 1970 consecutive adult patients with AML diagnosed and treated between January 2017 and July 2024 at Peking University People’s Hospital were reviewed. AML was diagnosed by histology, immunology, cytogenetics, and genetic abnormalities as described. The study enrolled participants who met the following inclusion criteria: (1) age ≥ 16 years; (2) histological complete remission (CR) achieved after induction therapy. Among 1970 AML patients, 1676 (85.1%) achieved final CR/CRi after induction chemotherapy and were enrolled in this study. A total of 207 participants with the RUNX1::RUNX1T1 fusion gene were eligible, along with 178 participants with the RUNX1::RUNX1T1 quantitation and MRD reduction record. This study was approved by Peking University People’s Hospital Ethics Committee (2025PHB305-001); conducted as per the Declaration of Helsinki.
2.2. Diagnosis, Monitoring, and Therapy Responses
Diagnosis, monitoring, and treatment responses adhered to the 2022 European Leukemia Net (ELN) recommendations [
7]. Immune phenotyping was performed using multi-parameter flow cytometry with CD45/side scatter (SSC) gating. Cytogenetic analyses were conducted using standard G-banding techniques. Molecular screening for leukemia-associated fusion genes and high-depth targeted regional sequencing (TRS) was performed for all patients. Demographic and clinical variables, including complete blood count (CBC) and results of initial hematological, cytogenetic, and molecular analyses, were extracted from medical records. Measurable residual disease was identified using real-time quantitative polymerase chain reaction (RT-qPCR) and multi-parameter flow cytometry measured minimal residual disease (MRD). RT-qPCR was performed on BM samples using DNA extracted with DNAzol kits (Invitrogen, Carlsbad, CA, USA) following standard protocols as previously described [
8]. Primers and TaqMan
® probes (Foster City, CA, USA) for the target gene and internal control (ALB) were designed with Primer Express 2.0. Reactions were run on an ABI PRISM
® 7500 (Foster City, CA, USA) using TaqMan
® Universal PCR Master Mix (Foster City, CA, USA), with specific primer/probe concentrations and 150–250 ng DNA. Cycling conditions included an initial step at 50 °C for 2 min and 95 °C for 10 min, followed by 50 cycles of 95 °C for 15 s and 60 °C for 1 min. Gene expression was calculated by normalizing target gene copies to ALB. Detection sensitivity ranged from 10
−4 to 10
−5 [
8]. In
RUNX1::RUNX1T1 AML, molecular response (MR)
2.5 (>2.5 log reduction) was determined after treatment cycle 1, while MR
3.0 (>3.0 log reduction) was identified after treatment cycle 2, according to the MRD detection guideline in previous study [
9].
The induction regimens, as detailed in previous studies [
6], comprised intensive therapy options including the homoharringtonine-cytarabine-aclarubicin (HAA) regimen and the idarubicin-cytarabine (IA) regimen, and the DA regimen. For patients unsuitable for intensive therapy, less intensive approaches such as hypomethylating agents (HMAs) combined with venetoclax (VEN) or the CAG regimen were employed. For favorable risk AML, patients who achieved CR or CR with incomplete hematologic recovery (CRi) received high-dose cytarabine-based consolidation therapy for 3–4 cycles or less intensive continued therapy. If patients did not achieve CR/CRi after 2 cycles of induction or relapsed, intermediate or high-dose cytarabine-based regimens, such as revised CLAG (cladribine, cytarabine, and granulocyte colony-stimulating factor [G-CSF]) or FLAG (fludarabine, cytarabine and G-CSF) regimens, were considered as salvage therapy. For intermediate and adverse risk AML, patients eligible for allogeneic hematopoietic stem cell transplantation (allo-HSCT) underwent ≥ 2 cycles of consolidation chemotherapy. If transplantation is not eligible, the chemotherapy regimen will be determined by the physician [
10]. Donor selection included human leukocyte antigen (HLA)-matched siblings, HLA-matched unrelated donors, or HLA haploidentical-related donors. Allo-HSCT was performed following previously reported methodologies. After the second consolidation course, eligible participants with a potential donor and physicians discussed the risks and benefits of transplant versus continuing consolidation chemotherapy, considering covariates, such as risk stratification, measurable residual disease test results, economics, and patient preference. Based on these discussions, 735 of 1676 participants (43.8%) and 78 of 207
RUNX1::RUNX1T1 fusion-positive participants (37%) received a transplant after a median of 4 (2–6) courses of consolidation chemotherapy, as described.
2.3. High-Depth Targeted Regional Sequencing (TRS)
TRS was performed on bone marrow samples from patients initially diagnosed with AML, and sequencing was conducted by Kingmed Diagnostics in Guangzhou. The deep-targeted sequencing panel initially comprised 175 genes for patients diagnosed between 2018 and 2020, and it was expanded to 290 genes for patients diagnosed from 2021 onwards. All genes included in the targeted sequencing panel were associated with hematological myeloid malignancies (
Table A1 in
Appendix A). DNA sequencing was executed using the Illumina NovaSeq6000 system (Illumina, San Diego, CA, USA) in accordance with the manufacturer’s recommendations. Variant curation adhered to the Standards and Guidelines for the Interpretation and Reporting of Sequence Variants in Cancer. This study primarily focused on variants categorized as having strong clinical significance (Tier I) and those presenting potential clinical significance (Tier II) [
11].
2.4. Statistical Analyses
Propensity score matching (PSM) was employed to estimate the causal effect of
KDM6A mutations on clinical outcomes. Among the 1677 participants, covariates, such as age, gender, ELN 2022 risk category [
7], Eastern Cooperative Oncology Group (ECOG) performance status, and whether allo-HSCT was performed after CR1 were included in the analysis. The matching procedure followed a 1:10 strategy, where 27 participants with
KDM6A mutations were matched with 270 participants with the wild-type genotype. The most frequent chromosomal abnormality co-occurring with
KDM6A mutations was
RUNX1::RUNX1T1 fusion, observed in 48.1% of cases (
n = 13). For the
RUNX1::RUNX1T1 fusion AML, additional covariates, including age, sex, MR
2.5, MR
3.0, and
KIT mutation, and allo-HSCT status, were incorporated [
12]. A similar 1:5 matching strategy was applied, with each treated participant matched to 10 control participants using nearest-neighbor matching with a 0.2 caliper. The balance of covariates before and after matching was assessed using standardized mean differences (SMDs) to ensure comparability between groups.
Descriptive statistics were employed to summarize covariates, with categorical variables presented as counts and percentages and continuous variables expressed as medians and interquartile ranges (IQRs). The Pearson chi-square test was applied to analyze categorical covariates. The correlation analysis was performed using the Pearson correlation coefficient to assess the linear relationship between genes. In contrast, the Student’s t-test (for normal distributed data) or the Mann–Whitney U test (for non-normally distributed data) was used to assess continuous covariates. Cox regression models were used to conduct multivariable analyses to identify covariates associated with overall survival (OS) and relapse-free survival (RFS). Variance inflation factor (VIF) was estimated to assess multicollinearity among covariates in the Cox model. OS and RFS were calculated using the Kaplan–Meier method with the log-rank test. The CIR was assessed using competing risk analysis, and Gray’s test compared differences between groups. A two-sided p-value < 0.05 was considered significant. For analysis and graphing, SPSS 27.0 (SPSS, Chicago, IL), R version 4.0.2 (R Core Team, Vienna, Austria), and GraphPad Prism 10 (GraphPad Software Inc., Boston, MA, USA) were employed.
2.5. Bioinformatics Analysis
Bioinformatics analyses were performed using R. Mutation annotation and visualization were conducted with the maftools package, including lollipop plots for KDM6A variants. Gene co-mutation patterns were assessed using corrplot and visualized with circlize and ComplexHeatmap. Baseline clinical characteristics were summarized using the tableone package. Data processing and figure generation were supported by the tidyverse suite.
4. Discussion
Based on the large scale analyzed for this alteration, we validated KDM6A mutations as a rare but recurrent genetic lesion in AML (1.6%), and RUNX1::RUNX1T1 AML (6.3%). KDM6A mutations are an independent prognostic marker for poor clinical outcomes, associated with a specific co-occurrence profile with the RUNX1::RUNX1T1 fusion gene.
To our knowledge, this study represents one of the first comprehensive investigations examining the clinical impact of
KDM6A mutations in patients with AML. Despite emerging evidence implicating
KDM6A alterations in hematologic malignancies [
13], prior research has predominantly focused on its transcriptional downregulation or epigenetic dysregulation rather than somatic mutations. Notably, only one previous study from our institute reported an association between
KDM6A mutations and adverse prognosis in the subset of
RUNX1::RUNX1T1-positive CBF-AML, partially aligning with our findings [
6]. However, that study did not explore the broader implications of
KDM6A mutations across unselected AML cohorts, leaving a critical gap in understanding their all subtype of AML relevance.
While several groups have linked reduced
KDM6A expression to chemotherapy resistance and poor outcomes [
2,
14,
15,
16], these observations operate at a distinct mechanistic level compared to genomic
KDM6A mutations.
KDM6A promotes AML progression and drug resistance through its tumor suppressor functions and involvement in DNA repair mechanisms [
17].
KDM6A is frequently mutated in AML, leading to a loss of function and increased drug resistance [
5]. For example,
KDM6A mutations are associated with higher IC50 values for cytarabine, indicating reduced sensitivity to this common AML treatment. Additionally,
KDM6A regulates the expression of DNA repair genes. Its deficiency impairs the DNA damage response (DDR), leading to increased sensitivity to PARP and BCL2 inhibition [
4]. In AML cells,
KDM6A is recruited to the transcriptional start sites of key homologous recombination genes upon DNA damage, facilitating their transcription. Loss of
KDM6A activity, either through genetic or pharmacological inhibition, results in elevated H3K27me3 levels at these regulatory elements, preventing gene transcription and compromising DNA repair. This highlights
KDM6A’s essential role in maintaining genomic stability and its potential as a therapeutic target in AML. Expression level-based studies reflect regulatory or epigenetic perturbations, whereas truncating or loss-of-function mutations directly impair
KDM6A’s function, potentially exacerbating genomic instability and altering transcriptional programs in a mutation-specific manner [
3,
4,
5]. Previous research has primarily focused on the impact of the
KDM6A expression level on tumor recurrence and treatment resistance, with limited direct data on complete remission rates [
18].
KDM6A mutations may enhance tumor cell drug resistance or promote immune evasion, thereby affecting treatment outcomes and recurrence rates [
19].
Our data extend these prior observations by demonstrating that KDM6A mutations, independent of expression changes, confer a high-risk phenotype characterized by shortened survival, even after adjusting for established prognostic factors such as age, cytogenetics, MRD, and ELN guidelines for AML risk stratification. The uniqueness of our study lies in its systematic integration of clinical, molecular, and functional data to establish KDM6A mutations as independent biomarkers of adverse prognosis. In AML, there are few studies on the coexistence of KDM6A mutations with other gene mutations or chromosomal abnormalities. To date, no large-scale AML cohorts have specifically interrogated the genetic signature, prognostic, or therapeutic relevance of KDM6A mutations, underscoring the novelty of our findings.
Our study had some limitations. First, it was a retrospective single-center clinical study, which inherently involves therapy selection biases. Second, we lacked functional studies to validate the clinical findings. Despite these limitations, the findings represent an important step towards understanding the KDM6A mutations influencing the prognosis of AML and could inform future therapeutic strategies.