Analysis of hTERT Gene Polymorphism, hTERT Gene Methylation and Telomere Length in Patients with De Novo AML, AML-MR and AML-Pct with Complex and Normal Karyotype
Authors: Adamska Monika , Kowal-Wiśniewska Ewelina , Przybylowicz-Chalecka Anna , Lis-Tanaś Emilia , Jarmuż-Szymczak Małgorzata , Gil Lidia 
Published: December 2024

Background: Acute myeloid leukemia (AML), among other cancers, is characterised by elevated expression of telomerase. Maintenance of telomere length (TL) is regulated by telomerase and human telomerase reverse transcriptase gene (hTERT). Understanding the mechanisms of TERT dysregulation in various AML subtypes and its impact on clinical outcome of patients remains still challenging. Study aims to assess the clinical outcome of AML post cytotoxic therapy (AML-pCT), de novo AML (dAML) and AML myelodysplasia-related (AML-MR) patients with complex karyotype (CK) or normal karyotype (NK) with respect tohTERT gene polymorphism, hTERT THOR region DNA methylation level and TL.

Methods: Retrospective analysis of 543 AML patients treated between 01.2009-04.2024 in a single hematological center was performed to select 58 patients with CK or NK (36 dAML; 11 AML-MR; 11 AML-pCT). Acute promyelocytic leukemia patients were excluded from the analysis. The genetic analysis included: hTERT gene DNA sequence variants analyses (p.(Ala1062Thr), rs2853669), THOR region DNA methylation level assessing and quantification of absolute TL on each chromosome end. As a study material, DNA isolated from retrospectively collected bone marrow samples and 10 healthy controls (HC) (peripheral blood) was used. Analysis of a clinical outcomes concerning genetic results was performed.

Results: Among 275 AML patients with performed cytogenetic analysis at the moment of diagnosis we select 58 AML individuals. Median age at diagnosis was 58.2 (IQR: 42.3-63.3) years. 79.3% of patients underwent intensive chemotherapy and 21 of them were qualified to allogenic hematopoietic cell transplantation (alloHCT). Non-intensive therapies were applied to 6 patients. CK occurred in majority of AML-pCT patients (7/11). NK was more frequent within dAML (22/36) and AML-MR subtypes (6/11). FLT3-ITD mutation was present in 15.9% of AML patients and was more frequent within AML with NK than AML with CK (p=0.03). RUNX1::RUNX1T1 rearrangement was present in 19.4% of AML (4/6 of them possessed CK).

p.(Ala1062Thr) hTERT DNA sequence variant was detected in 2 dAML with CK patients and in 2 HC. Rs2853669 hTERT polymorphism was present in 20/58 AML patients (most frequently among AML-pCT; 36.4%) and 7/10 HC. DNA methylation level of THOR region of TERT promoter was significantly higher in AML patients group compared to HC suggesting their potential role in TERT activation (p&lt;0.001). Hipermethylation of THOR region occurred in 44/58 patients (10/11 patients within AML-MR and 10/11 among AML-pCT subgroup). Elevated methylation was more frequent among AML with NK than AML with CK (p=0.08). Short TL were observed in 14/57 of AML patients (most frequently among dAML subgroup; 34.6%) and were more frequent among AML with CK than AML with NK (p=0.18).

Median overall survival (OS) in a study group was 12 months. Survival rates were lower within AML patients with CK than AML with NK (median OS: 10 and 22 months respectively; p=0.013). Among AML patients with hipermethylation of THOR region (1) median OS was lower among AML-pCT (4 months) than non-AML-pCT (17 months) subtypes (p= 0.048); (2) inferior survival rates were observed among CK than NK patients (median OS: 11 months vs not reached; p=0.024) and (3) survival rates were higher for individuals &lt; 60 years old than older (median OS: 27 vs 8 months; p= 0.006). Tendency toward inferior OS was observed within AML with short TL than long TL (median OS: 11 vs 14 months, p=0.1335).

In both multivariate and univariate Cox regression model treatment with chemotherapy, treatment with alloHCT (adjusted hazard ratio [AHR]: 0.01, 95% CI: 0.00-0.06, p&lt;0.0001), non-intensive regimens were factors associated with improved OS, however CK emerged as factor influencing poorer OS (AHR: 2.77; 95% CI, 1.38-5.6; p=0.005). In univariate Cox regression model age (hazard ratio [HR]: 1.03, 95% CI: 1.01-1.05, p=0.012) and AML-pCT subtype (HR: 2.48, 95% CI: 1.15-5.35, p=0.020) emerged as factors associated with worse OS.

Conslusions: Hipermethylation of a THOR region of TERT promoter observed in our study suggests higher telomerase activity and may represent a marker of a worse outcome for AML-pCT patients, AML individuals with CK as well as AML older than 60 years old. As the therapies targeting TERT can further improve the OS of TERT-dependent leukemias there is a growing need to perform a study on a larger group of AML patients.