Genetic subtypes of pediatric acute myeloid leukemia with poor outcomes show increased signaling of inflammatory cytokines

In a recent study published in Nature Communicationresearchers used ribonucleic acid (RNA) sequence data to understand the association between inflammatory cytokines and poor outcomes in pediatric acute myeloid leukemia (pAML).

Background

Pediatric acute myeloid leukemia is a heterogeneous disease with various subtypes based on genetic, clinical, transcriptional and epigenomic factors. Developing therapies that target the clinical outcomes of each of these subtypes is economically challenging. Targeting dysregulated pathways common to various pAML subtypes with poor outcomes can help make treatment methods more cost-effective.

Pro-inflammatory cytokine signaling pathways such as those for interleukin (IL)-6 are linked to various cancers, with IL-6 and IL-3 synergistically increasing hematopoietic stem cell proliferation and ill adult and pediatric AML findings being associated with elevated levels of IL-6 in the bone marrow. In adult AML, IL-6 also upregulates the Janus signal transducer kinase (JAK) and activator of transcription (STAT) signaling pathway in stem cells and blood cell progenitors.

Treatment with JAK/STAT pathway inhibitors or antibodies that neutralize IL-6 has shown promise in adult cases of AML. Understanding the role of IL-6 signaling in pAML and the association of IL-6 with pAML subtypes with poor clinical outcomes may aid the development of broad targeted therapies for various subtypes .

About the study

In the current study, researchers collected bone marrow samples from approximately 1500 patients enrolled in the pediatric oncology group who were diagnosed with pAML. Total RNA was extracted and bulk RNA sequence data was compared to that extracted from healthy controls with normal bone marrow.

The researchers then performed gene-set enrichment analyzes to understand the signaling pathways associated with elevated levels of IL-6 in certain groups of patients. The results were verified using previously published bone marrow RNA sequence data from an independent cohort. The immunological, genetic, demographic and transcriptomic profiles of patients expressing high levels of IL-6 and IL-6 receptors were also analyzed.

Bone marrow cells from pAML patients expressing high levels of IL-6 and IL-6 receptors were cultured in human bone marrow stromal cells (HS-5 cells), which mimic the stromal cell expression patterns of bone marrow such as IL-6, IL-1β secretion, receptor-like protein tyrosine kinase (KIT) ligand and macrophage/granulocyte colony stimulating factors M-CSF, G-CSF and GM -CSF.

Bone marrow cells were cultured in the presence and absence of Ruxolitinub, which inhibits JAK1/2 and signaling by various interferons (IFN), tumor necrosis factor-alpha (TNF-α), IL- 6 and GM-CSF. Cytokine signaling mediators were analyzed by time-of-flight cytometry (CyTOF).

In addition, differentially expressed genes in the bone marrow of pAML patients with high IL-6 and low IL-6, as well as in the normal bone marrow of healthy controls, were analyzed using a pairwise differential expression analysis.

Results

The results indicated that more than 20% of patients with pAML had elevated levels of IL-6 and higher signaling activity of inflammatory cytokines, such as TNF-α, IFNα and IFNβ, and IL-1. These high levels of inflammatory cytokines and signaling activity were also associated with poor outcomes, such as a lower probability of event-free and overall survival for two years.

Adjustment for age and cytogenic subtypes in the high IL-6 group did not improve two- and five-year overall survival, indicating that poor outcome and response to treatment were due to factors unrelated to cytogenetics and age. Furthermore, CyTOF analysis indicated that distinct genomic subtypes of pAML with elevated levels of IL-6 and IL-6 receptors have common receptor-mediated inflammatory signaling pathways. Other studies in adult patients with AML have also found similar patterns of upregulated GM-CSF, IL-6, and IL-1.

Targeted sequencing identified five recurrent regions of somatic mutations, including various translocations and rearrangements that activated common STAT-mediated signal transduction and protein phosphoinositide-3-kinase (PI3K) signaling pathways. Genomic subtypes associated with these somatic mutations also showed activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB).

Regardless of genomic subtype, elevated levels of IL-6 and IL-6 receptors have been associated with activation of JAK/STAT, NF-κB, extracellular signal-regulated kinase 1/2 (ERK1 /2) and the PI3K channels, and the in vitro inhibition of JAK1/2 by Ruxolitinub has been shown to downregulate receptor-mediated signaling by inflammatory cytokines.

conclusion

Overall, the results indicated that elevated levels of IL-6 and IL-6 receptors in pAML patients were associated with genetic subtypes based on five somatic mutations. However, regardless of subtype, pAML patients with elevated IL-6 levels exhibited upregulated inflammatory cytokine signaling pathways and JAK/STAT, NF-κB, ERK1/2, and PI3K pathways. activated.

Therapies including inhibitors of these co-activated pathways could benefit patients with high IL-6 pAML by reducing inflammatory cytokine signaling pathways across genetic subtypes.