- The study addressed unknown drivers and clonal trajectories of aneuploid evolution in hematopoietic stem and progenitor cells (HSPCs) in acute myeloid leukemia.
- Researchers developed a patient-derived induced pluripotent stem cell model, tracking chromosome evolution at single cell resolution.
- They found TP53-mutant HSPCs with chromosome 5q deletions, but not TP53 mutation alone, evolved complex chromosomal changes.
- The authors concluded that mutant TP53 and chromosome 5q deletions drive stepwise chromosome evolution in HSPCs.
- This research suggests BCL2 inhibition with venetoclax may target aneuploid clones in acute myeloid leukemia with complex karyotype.
Understanding Clonal Evolution in High-Risk Acute Myeloid Leukemia
Acute myeloid leukemia (AML) remains a formidable hematologic malignancy, especially in older patients or those with high-risk cytogenetics, where prognosis is poor [1, 2, 3]. Among the most challenging subtypes is complex karyotype AML (AML-CK), defined by its accumulation of multiple chromosomal abnormalities and frequently associated with TP53 mutations and chromosome 5q deletions [4]. While therapies combining the BCL2 inhibitor venetoclax with hypomethylating agents or low-dose cytarabine have improved outcomes for many patients unfit for intensive chemotherapy [5, 6, 7], the mechanisms driving the aggressive clonal evolution and treatment resistance in AML-CK are not fully understood [2]. Clarifying the precise genetic and molecular sequence of events in AML-CK is therefore critical for developing more effective, targeted interventions.
Unraveling the Genetic Drivers of Aneuploidy in AML-CK
A central question in acute myeloid leukemia with complex karyotype (AML-CK) has been what initiates the cascade of chromosomal instability. The disease is characterized by the clonal acquisition of multiple chromosomal abnormalities in hematopoietic stem and progenitor cells (HSPCs), but the initial drivers have been unclear. To investigate this, researchers developed a patient-derived induced pluripotent stem cell (iPSC) model. This technique allowed them to take cells from a patient, reprogram them to an early stem-cell-like state, and then observe how preleukemic genetic defects guide the development of cancer in a controlled laboratory setting. By tracking chromosomal changes at the single-cell level after inducing temporary mitotic stress, the study identified a crucial combination of genetic lesions. The findings show that HSPCs with both a TP53 mutation and a chromosome 5q deletion (del5q), but not a TP53 mutation alone, consistently evolved complex chromosomal changes. This evolution was not random; it proceeded through a stepwise acquisition of specific numerical and structural chromosome alterations that mirror those found in patients with AML-CK. The authors also determined that these individual abnormalities each conferred a distinct fitness advantage, meaning the altered cells were better able to survive and proliferate, which helps explain the aggressive nature of the disease.
Shared Gene Expression Signature and Therapeutic Implications
The study's findings extend from the genetic drivers to the downstream molecular landscape, revealing a consistent pattern of gene activity. Researchers discovered a conserved gene expression signature in both their lab-grown aneuploid HSPCs and in primary tumor samples from patients with AML-CK. This shared biological state was marked by the upregulation of the tumor suppressor PTEN, cohesin proteins (which are critical for chromosome segregation), and the anti-apoptotic factor BCL2. The existence of this common signature suggests that despite varied chromosomal changes, these malignant cells converge on a shared functional state. This discovery has direct clinical relevance, as it points to a specific, targetable vulnerability. The elevated BCL2 levels provided a strong rationale for a targeted therapy, and indeed, the study demonstrated that the clinical BCL2 inhibitor venetoclax effectively eradicated the BCL2-dependent aneuploid clones. However, the research also uncovered a potential mechanism of therapeutic escape: resistant clones could survive by undergoing a lineage switch and upregulating alternative anti-apoptotic factors from the BCL2 family. These results confirm that mutant TP53 and del5q together drive a predictable path of chromosomal evolution and establish a shared cellular state in aneuploid HSPCs, which in turn creates a therapeutic dependency that can be exploited clinically.
References
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2. DiNardo CD, Jonas BA, Pullarkat V, et al. Azacitidine and Venetoclax in Previously Untreated Acute Myeloid Leukemia. New England Journal of Medicine. 2020. doi:10.1056/nejmoa2012971
3. Döhner H, Wei AH, Appelbaum FR, et al. Diagnosis and management of AML in adults: 2022 recommendations from an international expert panel on behalf of the ELN. Blood. 2022. doi:10.1182/blood.2022016867
4. Creamer JP, Ray S, Stewart S, et al. Loss of 5q Drives Evolution to Aneuploidy in an iPSC Model of Complex Karyotype AML. Blood. 2024. doi:10.1182/blood-2024-206210
5. Zhu J, Fan J, Xie T, et al. Venetoclax combined chemotherapy versus chemotherapy alone for acute myeloid leukemia: a systematic review and meta-analysis. Frontiers in Oncology. 2024. doi:10.3389/fonc.2024.1361988
6. Wei AH, Montesinos P, Ivanov V, et al. Venetoclax plus LDAC for newly diagnosed AML ineligible for intensive chemotherapy: a phase 3 randomized placebo-controlled trial. Blood. 2020. doi:10.1182/blood.2020004856
7. Qureshi Z, Altaf F, Jamil A, Siddique R. Safety, Efficacy, and Predictive Factors of Venetoclax-Based Regimens in Elderly Acute Myeloid Leukemia Patients: A Meta-Analysis.. Clinical lymphoma, myeloma & leukemia. 2024. doi:10.1016/j.clml.2024.07.004